United States
Environmental Protection
Agency
Air and Radiation
(6604J)
402-R-9S-041
September 1993
EPA's Map of Radon Zones
MASSACHUSETTS
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EPA'S MAP OF RADON ZONES
MASSACHUSETTS
RADON DIVISION
OFFICE OF RADIATION AND INDOOR AIR
U.S. ENVIRONMENTAL PROTECTION AGENCY
SEPTEMBER, 1993
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ACKNOWLEDGEMENTS
This document was prepared by the U.S. Environmental Protection Agency's (EPA's)
Office of Radiation and Indoor Air (ORIA) in conjunction with the U.S. Geological Survey
(USGS). Sharon -W. White was the EPA project manager. Numerous other people in ORIA
were instrumental in the development of the Map of Radon Zones, including Lisa Ratcliff,
Kirk Maconaughey, R. Thomas Peake, Dave Rowson, and Steve Page.
EPA would especially like to acknowledge the outstanding effort of the USGS
radon team ~ Linda Gundersen, Randy Schumann, Jim Otton, Doug Owen, Russell
Dubiel, Kendell Dickinson, and Sandra Szarzi — in developing the technical base for the
Map of Radon Zones.
ORIA would also like to recognize the efforts of all the EPA Regional Offices in
coordinating the reviews with the State programs and the Association of American State
Geologists (AASG) for providing a liaison with the State geological surveys. In addition,
appreciation is expressed to all of the State radon programs and geological surveys for their
technical input and review of the Map of Radon Zones.
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TABLE OF CONTENTS
I. OVERVIEW
II. THE USGS/EPA RADON POTENTIAL
ASSESSMENTS:INTRODUCTION
III. REGION 1 GEOLOGIC RADON POTENTIAL
SUMMARY
V. PRELIMINARY GEOLOGIC RADON POTENTIAL
ASSESSMENT OF MASSACHUSETTS
V. EPA'S MAP OF RADON ZONES -- MASSACHUSETTS
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OVERVIEW
Sections 307 and 309 of the 1988 Indoor Radon Abatement Act (IRAA) direct EPA to
identify areas of the United States that have the potential to produce elevated levels of radon.
EPA, the U.S. Geological Survey (USGS), and the Association of American State Geologists
(AASG) have worked closely over the past several years to produce a series of maps and
documents which address these directives. The EPA Map of Radon Zones is a compilation of
that work and fulfills the requirements of sections 307 and 309 of IRAA. The Map of Radon
Zones identifies, on a county-by-county basis, areas of the U.S. that have the highest potential
for elevated indoor radon levels (greater than 4 pCi/L).
The Map of Radon Zones is designed to assist national, State and local governments
and organizations to target their radon program activities and resources. It is also intended to
help building code officials determine areas that are the highest priority for adopting radon-
resistant building practices. The Map of Radon Zones should not be used to determine if
individual homes in any given area need to be tested for radon. EPA recommends that all
homes be tested for radon, regardless of geographic location or the zone designation of
the county in which they are located.
This document provides background information concerning the development of the
Map of Radon Zones. It explains the purposes of the map, the approach for developing the
map (including the respective roles of EPA and USGS), the data sources used, the conclusions
and confidence levels developed for the prediction of radon potential, and the review process
that was conducted to finalize this effort.
BACKGROUND
Radon (Rn222) is a colorless, odorless, radioactive gas. It comes from the natural
decay of uranium that is found in nearly all soils. It typically moves through the ground to
the air above and into homes and other buildings through cracks and openings in the
foundation. Any home, school or workplace may have a radon problem, regardless of
whether it is new or old, well-sealed or drafty, or with or without a basement. Nearly one out
of every 15 homes in the U.S. is estimated to have elevated annual average levels of indoor
radon.
Radon first gained national attention in early 1984, when extremely high levels of
indoor radon were found in areas of Pennsylvania, New Jersey, and New York, along the
Reading Prong-physiographic province. EPA established a Radon Program in 1985 to assist
States and homeowners in reducing their risk of lung cancer from indoor radon.
Since 1985, EPA and USGS have been working together to continually increase our
understanding of radon sources and the migration dynamics that cause elevated indoor radon
levels. Early efforts resulted in the 1987 map entitled "Areas with Potentially High Radon
Levels." This map was based on limited geologic information only because few indoor radon
measurements were available at the time. The development of EPA's Map of Radon Zones
and its technical foundation, USGS1 National Geologic Radon Province Map, has been based
on additional information from six years of the State/EPA Residential Radon Surveys,
independent State residential surveys, and continued expansion of geologic and geophysical
information, particularly the data from the National Uranium Resource Evaluation project.
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Purpose of the Map of Radon Zones
EPA's Map of Radon Zones (Figure 1) assigns each of the 3141 counties in the
United States to one of three zones:
o Zone 1 counties have a predicted average indoor screening level > than
4 pCi/L
o Zone 2 counties have a predicted average screening level > 2 pCi/L and
< 4 pCi/L
o Zone 3 counties have a predicted average screening level < 2 pCi/L
The Zone designations were determined by assessing five factors that are known to be
important indicators of radon potential: indoor radon measurements, geology, aerial
radioactivity, soil parameters, and foundation types.
The predictions of average screening levels in each of the Zones is an expression of
radon potential in the lowest liveable area of a structure. This map is unable to estimate
actual exposures to radon. EPA recommends methods for testing and fixing individual homes
based on an estimate of actual exposure to radon. For more information on testing and fixing
elevated radon levels in homes consult these EPA publications: A Citizen's Guide to Radon.
the Consumer's Guide to Radon Reduction and the Home Buyer's and Seller's Guide to
Radon.
EPA believes that States, local governments and other organizations can achieve
optimal risk reductions by targeting resources and program activities to high radon potential
areas. Emphasizing targeted approaches (technical assistance, information and outreach
efforts, promotion of real estate mandates and policies and building codes, etc.) in such areas
addresses the greatest potential risks first.
EPA also believes that the use of passive radon control systems in the construction of
new homes in Zone 1 counties, and the activation of those systems if necessitated by follow-
up testing, is a cost effective approach to achieving significant radon risk reduction.
The Map of Radon Zones and its supporting documentation establish no regulatory
requirements. Use of this map by State or local radon programs and building code officials is
voluntary. The information presented on the Map of Radon Zones and in the supporting
documentation is not applicable to radon in water.
Development of the Map of Radon Zones
The technical foundation for the Map of Radon Zones is the USGS Geologic Radon
Province Map. In order to examine the radon potential for the United States, the USGS
began by identifying approximately 360 separate geologic provinces for the U.S. The
provinces are shown on the USGS Geologic Radon Province Map (Figure 2). Each of the
geologic provinces was evaluated by examining the available data for that area: indoor radon
measurements, geology, aerial radioactivity, soil parameters, and foundation types. As stated
previously, these five factors are considered to be of basic importance in assessing radon
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potential and some data are available for each of these factors in every geologic province. The
province boundaries do not coincide with political borders (county and state) but define areas
of general radon potential. The five factors were assigned numerical values based on an
assessment of their respective contribution to radon potential, and a confidence level was
assigned to each contributing variable. The approach used by USGS to estimate the radon
potential for each province is described in Part II of this document.
EPA subsequently developed the Map of Radon Zones by extrapolating from the
province level to the county level so that all counties in the U.S. were assigned to one of
three radon zones. EPA assigned each county to a given zone based on its provincial radon
potential. For example, if a county is located within a geologic province that has a predicted
average screening level greater than 4 pCi/L, it was assigned to Zone 1. Likewise, counties
located in provinces with predicted average screening levels > 2 pCi/L and < 4 pCi/L, and
less than 2 pCi/L, were assigned to Zones 2 and 3, respectively.
If the boundaries of a county fall in more than one geologic province, the county was
assigned to a zone based on the predicted radon potential of the province in which most of
the area lies. For example, if three different provinces cross through a given county, the
county was assigned to the zone representing the radon potential of the province containing
most of the county's land area. (In this case, it is not technically correct to say that the
predicted average screening level applies to the entire county since the county falls in
multiple provinces with differing radon potentials.)
Figures 3 and 4 demonstrate an example of how EPA extrapolated the county zone
designations for Nebraska from the USGS geologic province map for the State. As figure 3
shows, USGS has identified 5 geologic provinces for Nebraska. Most of the counties are
extrapolated "straight" from their corresponding provinces, but there are counties "partitioned"
by several provinces — for example, Lincoln County. Although Lincoln county falls in
multiple provinces, it was assigned to Zone 3 because most of its area falls in the province
with the lowest radon potential.
It is important to note that EPA's extrapolation from the province level to the
county level may mask significant "highs" and "lows" within specific counties. In other
words, within-county variations in radon potential are not shown on the Map of Radon
Zones. EPA recommends that users who may need to address specific within-county
variations in radon potential (e.g., local government officials considering the
implementation of radon-resistant construction codes) consult USGS' Geologic Radon
Province Map and the State chapters provided with this map for more detailed
information, as well as any locally available data.
Map Validation
The Map of Radon Zones is intended to represent a preliminary assessment of radon
potential for the entire United States. The factors that are used in this effort —indoor radon
data, geology, aerial radioactivity, soils, and foundation type ~ are basic indicators for radon
potential. It is important to note, however, that the map's county zone designations are not
"statistically valid" predictions due to the nature of the data available for these 5 factors at the
county level. In order to validate the map in light of this lack of statistical confidence, EPA
conducted a number of analyses. These analyses have helped EPA to identify the best
situations in which to apply the map, and its limitations.
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Figure 3
Geologic Radon Potential Provinces for Nebraska
Lincoln Count y
gilt Uoicritc Low
Figure 4
NEBRASKA - EPA Map of Radon Zones
Lincoln County
lest 1 Zeae 2 Zoae 3
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One such analysis involved comparing county zone designations to indoor radon
measurements from the State/EPA Residential Radon Surveys (SRRS). Screening averages
for counties with at least 100 measurements were compared to the counties' predicted radon
potential as indicated by the Map of Radon Zones. EPA found that 72% of the county
screening averages were correctly reflected by the anrfopriate zone designations on the Map.
In all other cases, they only differed by 1 zone.
Another accuracy analysis used the annual average data from the National Residential
Radon Survey (NRRS). The NRRS indicated that approximately 6 million homes in the
United States have annual averages greater than or equal to 4 pCi/L. By cross checking the
county location of the approximately 5,700 homes which participated in the survey, their
radon measurements, and the zone designations for these counties, EPA found that
approximately 3.8 million homes of the 5.4 million homes with radon levels greater than or
equal to 4 pCi/L will be found in counties designated as Zone 1. A random sampling of an
equal number of counties would have only found approximately 1.8 million homes greater
than 4 pCi/L. In other words, this analysis indicated that the map approach is three times
more efficient at identifying high radon areas than random selection of zone designations.
Together, these analyses show that the approach EPA used to develop the Map of
Radon Zones is a reasonable one. In addition, the Agency's confidence is enhanced by results
of the extensive State review process — the map generally agrees with the States' knowledge
of and experience in their own jurisdictions. However, the accuracy analyses highlight two
important points: the fact that elevated levels will be found in Zones 2 and 3, and that there
will be significant numbers of homes with lower indoor radon levels in all of the Zones. For
these reasons, users of the Map of Radon Zones need to supplement the Map with locally
available data whenever possible. Although all known "hot spots", i.e., localized areas of
consistently elevated levels, are discussed in the State-
specific chapters, accurately defining the boundaries of the "hot spots" on this scale of map is
not possible at this time. Also, unknown "hot spots" do exist.
The Map of Radon Zones is intended to be a starting point for characterizing radon
potential because our knowledge of radon sources and transport is always growing. Although
this effort represents the best data available at this time, EPA will continue to study these
parameters and others such as house construction, ventilation features and meteorology factors
in order to better characterize the presence of radon in U.S homes, especially in high risk
areas. These efforts will eventually assist EPA in refining and revising the conclusions of the
Map of Radon Zones. And although this map is most appropriately used as a targeting tool
by the aforementioned audiences ~ the Agency encourages all residents to test their homes
for radon, regardless of geographic location or the zone designation of the county in
which they live. Similarly, the Map of Radon Zones should not to be used in lieu of
testing during real estate transactions.
Review Process
The Map of Radon Zones has undergone extensive review within EPA and outside the
Agency. The Association of American State Geologists (AASG) played an integral role in
this review process. The AASG individual State geologists have reviewed their State-specific
information, the USGS Geologic Radon Province Map, and other materials for their geologic
content and consistency.
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In addition to each State geologist providing technical comments, the State radon
offices were asked to comment on their respective States' radon potential evaluations. In
particular, the States were asked to evaluate the data used to assign their counties to specific
zones. EPA and USGS worked with the States to resolve any issues concerning county zone
designations. In a few cases, States have requested changes in county zone designations. The
requests were based on additional data from the State on geology, indoor radon
measurements, population, etc. Upon reviewing the data submitted by the States, EPA did
make some changes in zone designations. These changes, which do not strictly follow the
methodology outlined in this document, are discussed in the respective State chapters.
EPA encourages the States and counties to conduct further research and data collection
efforts to refine the Map of Radon Zones. EPA would like to be kept informed of any
changes the States, counties, or others make to the maps. Updates and revisions will be
handled in a similar fashion to the way the map was developed. States should notify EPA of
any proposed changes by forwarding the changes through the Regional EPA offices that are
listed in Part II. Depending on the amount of new information that is presented, EPA will
consider updating this map periodically. The State radon programs should initiate proper
notification of the appropriate State officials when the Map of Radon Zones is released and
when revisions or updates are made by the State or EPA.
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THE USGS/EPA RADON POTENTIAL ASSESSMENTS: AN INTRODUCTION
by
Linda C.S. Gundersen and R. Randal! Schumann
U.S. Geological Survey
and
Sharon W. White
U.S. Environmental Protection Agency
BACKGROUND
The Indoor Radon Abatement Act of 1988 (15 U.S.C. 2661-2671) directed the U.S.
Environmental Protection Agency (EPA) to identify areas of the United States that have the
potential to produce harmful levels of indoor radon. These characterizations were to be based
on both geological data and on indoor radon levels in homes and other structures. The EPA
also was directed to develop model standards and techniques for new building construction
that would provide adequate prevention or mitigation of radon entry. As part of an
Interagency Agreement between the EPA and the U.S. Geological Survey (USGS), the USGS
has prepared radon potential estimates for the United States. This report is one of ten
booklets that document this effort. The purpose and intended use of these reports is to help
identify areas where states can target their radon program resources, to provide guidance in
selecting the most appropriate building code options for areas, and to provide general
information on radon and geology for each state for federal, state, and municipal officials
dealing with radon issues. These reports are not intended to be used as a substitute for
indoor radon testing, and they cannot and should not be used to estimate or predict the
indoor radon concentrations of individual homes, building sites, or housing tracts. Elevated
levels of indoor radon have been found in every State, and EPA recommends that all homes
be tested for indoor radon.
Booklets detailing the radon potential assessment for the U.S. have been developed for
each State. USGS geologists are the authors of the geologic radon potential booklets. Each
booklet consists of several components, the first being an overview to the mapping project
(Part I), this introduction to the USGS assessment (Part II), including a general discussion of
radon (occurrence, transport, etc.), and details concerning the types of data used. The third
component is a summary chapter outlining the general geology and geologic radon potential
of the EPA Region (Part III). The fourth component is an individual chapter for each state
(Part IV). Each state chapter discusses the state's specific geographic setting, soils, geologic
setting, geologic radon potential, indoor radon data, and a summary outlining the radon
potential rankings of geologic areas in the state. A variety of maps are presented in each
chapter—geologic, geographic, population, soils, aerial radioactivity, and indoor radon data by
county. Finally, the booklets contain EPA's map of radon zones for each state and an
accompanying description (Part V).
Because of constraints on the scales of maps presented in these reports and because the
smallest units used to present the indoor radon data are counties, some generalizations have
been made in order to estimate the radon potential of each area. Variations in geology, soil
characteristics, climatic factors, homeowner lifestyles, and other factors that influence radon
concentrations can be quite large within any particular geologic area, so these reports cannot
be used to estimate or predict the indoor radon concentrations of individual homes or housing
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tracts. Within any area of a given geologic radon potential ranking, there are likely to be
areas where the radon potential is lower or higher than that assigned to the area as a whole,
especially in larger areas such as the large counties in some western states.
In each state chapter, references to additional reports related to radon are listed for the
state, and the reader is urged to consult these reports for more detailed information. In most
cases the best sources of information on radon for specific areas are state and local
departments of health, state departments responsible for nuclear safely or environmental
protection, and U.S. EPA regional offices. More detailed information on state or local
geology may be obtained from the state geological surveys. Addresses and telephone
numbers of state radon contacts, geological surveys, and EPA regional offices are listed in
Appendix C at the end of this chapter.
RADON GENERATION AND TRANSPORT IN SOILS
Radon (5HRn) is produced from the radioactive decay of radium (226Ra), which is, in turn,
a product of the decay of uranium (USU) (fig. 1). The half-life of 222Rn is 3.825 days. Other
isotopes of radon occur naturally, but, with the exception of thoron (220Rn), which occurs in
concentrations high enough to be of concern in a few localized areas, they are less important
in terms of indoor radon risk because of their extremely short half-lives and less common
occurrence. In general, the concentration and mobility of radon in soil are dependent on
several factors, the most important of which are the soil's radium content and distribution,
porosity, permeability to gas movement, and moisture content. These characteristics are, in
turn, determined by the soil's parent-material composition, climate, and the soil's age or
maturity. If parent-material composition, climate, vegetation, age of the soil, and topography
are known, the physical and chemical properties of a soil in a given area can be predicted.
As soils form, they develop distinct layers, or horizons, that are cumulatively called the
soil profile. The A horizon is a surface or near-surface horizon containing a relative
abundance of organic matter but dominated by mineral matter. Some soils contain an E
horizon, directly below the A horizon, that is generally characterized by loss of clays, iron, or
aluminum, and has a characteristically lighter color than the A horizon. The B horizon
underlies the A or E horizon. Important characteristics of B horizons include accumulation of
clays, iron oxides, calcium carbonate or other soluble salts, and organic matter complexes. In
drier environments, a horizon may exist within or below the B horizon that is dominated by
calcium carbonate, often called caliche or calcrete. This carbonate-cemented horizon is
designated the K horizon in modern soil classification schemes. The C horizon underlies the
B (or K) and is a zone of weathered parent material that does not exhibit characteristics of A
or B horizons; that is, it is generally not a zone of leaching or accumulation. In soils formed
in place from the underlying bedrock, the C horizon is a zone of unconsolidated, weathered
bedrock overlying the unweathered bedrock.
The shape and orientation of soil particles (soil structure) control permeability and affect
water movement in the soil. Soils with blocky or granular structure have roughly equivalent
permeabilities in the horizontal and vertical directions, and air and water can infiltrate the soil
relatively easily. However, in soils with platy structure, horizontal permeability is much
greater than vertical permeability, and air and moisture infiltration is generally slow. Soils
with prismatic or columnar structure have dominantly vertical permeability. Platy and
prismatic structures form in soils with high clay contents. In soils with shrink-swell clays, air
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and moisture infiltration rates and depth of wetting may be limited when the cracks in the
surface soil layers swell shut. Clay-rich B horizons, particularly those with massive or platy
structure, can form a capping layer that impedes the escape of soil gas to the surface
(Schumann and others, 1992). However, the shrinkage of clays can act to open or widen
cracks upon drying, thus increasing the soil's permeability to gas flow during drier periods.
Radon transport in soils occurs by two processes: (1) diffusion and (2) flow (Tanner,
1964). Diffusion is the process whereby radon atoms move from areas of higher
concentration to areas of lower concentration in response to a concentration gradient. Flow is
the process by which soil air moves through soil pores in response to differences in pressure
within the soil or between the soil and the atmosphere, carrying the radon atoms along with it.
Diffusion is the dominant radon transport process in soils of low permeability, whereas flow
tends to dominate in highly permeable soils (Sextro and others, 1987). In low-permeability
soils, much of the radon may decay before it is able to enter a building because its transport
rate is reduced. Conversely, highly permeable soils, even those that are relatively low in
radium, such as those derived from some types of glacial deposits, have been associated with
high indoor radon levels in Europe and in the northern United States (Akerblom and others,
1984; Kunz and others, 1989; Sextro and others, 1987). In areas of karst topography formed
in carbonate rock (limestone or dolomite) environments, solution cavities and fissures can
increase soil permeability at depth by providing additional pathways for gas flow.
Not all radium contained in soil grains and grain coatings will result in mobile radon
when the radium decays. Depending on where the radium is distributed in the soil, many of
the radon atoms may remain imbedded in the soil grain containing the parent radium atom, or
become imbedded in adjacent soil grains. The portion of radium that releases radon into the
pores and fractures of rocks and soils is called the emanating fraction. When a radium atom
decays to radon, the energy generated is strong enough to send the radon atom a distance of
about 40 nanometers (1 nm = 10'9 meters), or about 2x10'6 inches—this is known as alpha
recoil (Tanner, 1980) Moisture in the soil lessens the chance of a recoiling radon atom
becoming imbedded in an adjacent grain. Because water is more dense than air, a radon atom
will travel a shorter distance in a water-filled pore than in an air-filled pore, thus increasing
the likelihood that the radon atom will remain in the pore space. Intermediate moisture levels
enhance radon emanation but do not significantly affect permeability. However, high
moisture levels can significantly decrease the gas permeability of the soil and impede radon
movement through the soil
Concentrations of radon in soils are generally many times higher than those inside of
buildings, ranging from tens of pCi/L to more than 100,000 pCi/L, but typically in the range
of hundreds to low thousands of pCi/L. Soil-gas radon concentrations can vary in response to
variations in climate and weather on hourly, daily, or seasonal time scales. Schumann and
others (1992) and Rose and others (1988) recorded order-of-magnitude variations in soil-gas
radon concentrations between seasons in Colorado and Pennsylvania. The most important
factors appear to be (1) soil moisture conditions, which are controlled in large part by
precipitation; (2) barometric pressure; and (3) temperature. Washington and Rose (1990)
suggest that temperature-controlled partitioning of radon between water and gas in soil pores
also has a significant influence on the amount of mobile radon in soil gas.
Homes in hilly limestone regions of the southern Appalachians were found to have higher
indoor radon concentrations during the summer than in the winter. A suggested cause for this
phenomenon involves temperature/pressure-driven flow of radon-laden air from subsurface
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solution cavities in the carbonate rock into houses. As warm air enters solution cavities that
are higher on the hillslope than the homes,,it cools and settles, pushing radon-laden air from
lower in the cave or cavity system into structures on the hillslope (Gammage and others,
1993). In contrast, homes built over caves having openings situated below the level of the
home had higher indoor radon levels in the winter, caused by cooler outside air entering the
cave, driving radon-laden air into cracks and solution cavities in the rock and soil, and
ultimately, into homes (Gammage and others, 1993).
RADON ENTRY INTO BUILDINGS
A driving force (reduced atmospheric pressure in the house relative to the soil, producing
a pressure gradient) and entry points must exist for radon to enter a building from the soil.
The negative pressure caused by furnace combustion, ventilation devices, and the stack effect
(the rising and escape of warm air from the upper floors of the building, causing a
temperature and pressure gradient within the structure) during cold winter months are
common driving forces. Cracks and other penetrations through building foundations, sump
holes, and slab-to-foundation wall joints are common entry points.
Radon levels in the basement are generally higher than those on the main floor or upper
floors of most structures. Homes with basements generally provide more entry points for
radon, commonly have a more pronounced stack effect, and typically have lower air pressure
relative to the surrounding soil than nonbasement homes. The term "nonbasement" applies to
slab-on-grade or crawl space construction.
METHODS AND SOURCES OF DATA
The assessments of radon potential in the booklets that follow this introduction were
made using five main types of data: (1) geologic (lithologic); (2) aerial radiometric; (3) soil '
characteristics, including soil moisture, permeability, and drainage characteristics; (4) indoor
radon data; and (5) building architecture (specifically, whether homes in each area are built
slab-on-grade or have a basement or crawl space). These five factors were evaluated and
integrated to produce estimates of radon potential. Field measurements of soil-gas radon or
soil radioactivity were not used except where such data were available in existing, published
reports of local field studies. Where applicable, such field studies are described in the
individual state chapters.
GEOLOGIC DATA
The types and distribution of lithologic units and other geologic features in an
assessment area are of primary importance in determining radon potential. Rock types that
are most likely to cause indoor radon problems include carbonaceous black shales, glauconite-
bearing sandstones, certain kinds of fluvial sandstones and fluvial sediments, phosphorites,
chalk, karst-producing carbonate rocks, certain kinds of glacial deposits, bauxite, uranium-rich
granitic rocks, metamorphic rocks of granitic composition, silica-rich volcanic rocks, many
sheared or faulted rocks, some coals, and certain kinds of contact metamorphosed rocks.
Rock types least likely to cause radon problems include marine quartz sands, non-.
carbonaceous shales and siltstones, certain kinds of clays, silica-poor metamorphic and
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igneous rocks, and basalts. Exceptions exist within these general lithologic groups because of
the occurrence of localized uranium deposits, commonly of the hydrothermal type in
crystalline rocks or the "roll-front" type in sedimentary rocks. Uranium and radium are
commonly sited in heavy minerals, iron-oxide coatings on rock and soil grains, and organic
materials in soils and sediments. Less common are uranium associated with phosphate and
carbonate complexes in rocks and soils, and uranium minerals.
Although many cases of elevated indoor radon levels can be traced to high radium and
(or) uranium concentrations in parent rocks, some structural features, most notably faults and
shear zones, have been identified as sites of localized uranium concentrations (Deffeyes and
MacGregor, 1980) and have been associated with some of the highest reported indoor radon
levels (Gundersen, 1991). The two highest known indoor radon occurrences are associated
with sheared fault zones in Boyertown, Pennsylvania (Gundersen and others, 1988a; Smith
and others, 1987), and in Clinton, New Jersey (Henry and others, 1991; Muessig and Bell,
1988).
NURE AERIAL RADIOMETRIC DATA
Aerial radiometric data are used to quantify the radioactivity of rocks and soils.
Equivalent uranium (eU) data provide an estimate of the surficial concentrations of radon
parent materials (uranium, radium) in rocks and soils. Equivalent uranium is calculated from
the counts received by a gamma-ray detector from the 1.76 MeV (mega-electron volts)
emission energy corresponding to bismuth-214 (214Bi), with the assumption that uranium and
its decay products are in secular equilibrium. Equivalent uranium is expressed in units of
parts per million (ppm). Gamma radioactivity also may be expressed in terms of a radium
activity; 3 ppm eU corresponds to approximately 1 picocurie per gram (pCi/g) of radium-226.
Although radon is highly mobile in soil and its concentration is affected by meteorological
conditions (Kovach, 1945; Klusman and Jaacks, 1987; Schery and others, 1984; Schumann
and others, 1992), statistical correlations between average soil-gas radon concentrations and
average eU values for a wide variety of soils have been documented (Gundersen and others,
1988a, 1988b; Schumann and Owen, 1988). Aerial radiometric data can provide an estimate
of radon source strength over a region, but the amount of radon that is able to enter a home
from the soil is dependent on several local factors, including soil structure, grain size
distribution, moisture content, and permeability, as well as type of house construction and its
structural condition.
The aerial radiometric data used for these characterizations were collected as part of the
Department of Energy National Uranium Resource Evaluation (NURE) program of the 1970s
and early 1980s. The purpose of the NURE program was to identify and describe areas in the
United States having potential uranium resources (U.S. Department of Energy, 1976). The
NURE aerial radiometric data were collected by aircraft in which a gamma-ray spectrometer
was mounted, flying approximately 122 m (400 ft) above the ground surface. The equivalent
uranium maps presented in the state chapters were generated from reprocessed NURE data in
which smoothing, filtering, recalibrating, and matching of adjacent quadrangle data sets were
performed to compensate for background, altitude, calibration, and other types of errors and
inconsistencies in the original data set (Duval and others, 1989). The data were then gridded
and contoured to produce maps of eU with a pixel size corresponding to approximately 2.5 x
2.5 km (1.6 x 1.6 mi).
II-6 Reprinted from USGS Open-File Report 93-292
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FLIGHT LINE SPICING OF SUKE AERIAL SURVEYS
2 KU (1 MILE)
5 KM (3 MILES)
2 i 5 KU
10 £11 (6 BILES)
5 fc 10 KM
NO DATA
Figure 2. Nominal flightline spacings for NURE aerial gamma-ray surveys covering the
contiguous United States (from Duval and others, 1990). Rectangles represent I°x2° quadrangles.
-------
Figure 2 is an index map of NURE 1° x 2° quadrangles showing the flight-line spacing
for each quadrangle. In general, the more closely spaced the flightlines are, the more area
was covered by the aerial gamma survey, and thus, more detail is available in the data set.
For an altitude of 400 ft above the ground surface and with primary flightline spacing
typically between 3 and 6 miles, less than 10 percent of the ground surface of the United
States was actually measured by the airborne gamma-ray detectors (Duval and others, 1989),
although some areas had better coverage than others due to the differences in flight-line
spacing' between areas (fig. 2). This suggests that some localized uranium anomalies may not
have been detected by the aerial surveys, but the good correlations of eU patterns with
geologic outcrop patterns indicate that, at relatively small scales (approximately 1:1,000,000
or smaller) the National eU map (Duval and others, 1989) gives reasonably good estimates of
average surface uranium concentrations and thus can assist in the prediction of radon potential
of rocks and soils, especially when augmented with additional geologic and soil data.
The shallow (20-30 cm) depth of investigation of gamma-ray spectrometers, either
ground-based or airborne (Duval and others, 1971; Durrance, 1986), suggests that gamma-ray
data may sometimes underestimate the radon-source strength in soils in which some of the
radionuclides in the near-surface soil layers have been transported downward through the soil
profile In such cases the concentration of radioactive minerals in the A horizon would be
lower than in the B horizon, where such minerals are typically concentrated. The
concentration of radionuclides in the C horizon and below may be relatively unaffected by
surface solution processes. Under these conditions the surface gamma-ray signal may indicate
a lower radon source concentration than actually exists in the deeper soil layers, which are
most likely to affect radon levels in structures with basements. The redistribution of
radionuclides in soil profiles is dependent on a combination of climatic, geologic, and
geochemical factors. There is reason to believe that correlations of eU with actual soil
radium and uranium concentrations at a depth relevant to radon entry into structures may be
regionally variable (Duval, 1989; Schumann and Gundersen, 1991). Given sufficient
understanding of the factors cited above, these regional differences may be predictable.
SOIL SURVEY DATA
Soil surveys prepared by the U.S. Soil Conservation Service (SCS) provide data on soil
characteristics, including soil-cover thickness, grain-size distribution, permeability, shrink-
swell potential, vegetative cover, generalized groundwater characteristics, and land use. The
reports are available in county formats and State summaries. The county reports typically
contain both generalized and detailed maps of soils in the area.
Because of time and map-scale constraints, it was impractical to examine county soil
reports for each county in the United States, so more generalized summaries at appropriate
scales were used where available. For State or regional-scale radon characterizations, soil
maps were compared to geologic maps of the area, and the soil descriptions, shrink-swell
potential, drainage characteristics, depth to seasonal high water table, permeability, and other
relevant characteristics of each soil group noted. Technical soil terms used in soil surveys are
generally complex; however, a good summary of soil engineering terms and the national
distribution of technical soil types is the "Soils" sheet of the National Atlas (U.S. Department
of Agriculture, 1987).
II-8 Reprinted from USGS Open-File Report 93-292
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Soil permeability is commonly expressed in SCS soil surveys in terms of the speed, in
inches per hour (in/hr), at which water soaks into the soil, as measured in a soil percolation
test. Although in/hr are not truly units of permeability, these units are in widespread use and
are referred to as "permeability" in SCS soil surveys. The permeabilities listed in the SCS
. jr.eys are for water, but they generally correlate w 11 with gas permeability, because data
on gas permeability of soils is extremely limited, data on permeability to water is used as a
substitute except in cases in which excessive soil moisture is known to exist. Water in soil
pores inhibits gas transport, so the amount of radon available to a home is effectively reduced
by a high water table. Areas likely to have high water tables include river valleys, coastal
areas, and some areas overlain by deposits of glacial origin (for example, loess).
Soil permeabilities greater than 6.0 in/hr may be considered high, and permeabilities less
than 0.6 in/hr may be considered low in terms of soil-gas transport. Soils with low
permeability may generally be considered to have a lower radon potential than more
permeable soils with similar radium concentrations. Many well-developed soils contain a
clay-rich B horizon that may impede vertical soil gas transport. Radon generated below this
horizon cannot readily escape to the surface, so it would instead tend to move laterally,
especially under the influence of a negative pressure exerted by a building.
Shrink-swell potential is an indicator of the abundance of smectitic (swelling) clays in a
soil. Soils with a high shrink-swell potential may cause building foundations to crack,
creating pathways for radon entry into the structure. During dry periods, desiccation cracks in
shrink-swell soils provide additional pathways for soil-gas transport and effectively increase
the gas permeability of the soil. Soil permeability data and soil profile data thus provide
important information for regional radon assessments.
INDOOR RADON DATA
Two major sources of indoor radon data were used. The first and largest source of data is
from the State/EPA Residential Radon Survey (Ronca-Battista and others, 1988; Dziuban and
others, 1990). Forty-two states completed EPA-sponsored indoor radon surveys between 1986
and 1992 (fig. 3). The State/EPA Residential Radon Surveys were designed to be
comprehensive and statistically significant at the state level, and were subjected to high levels
of quality assurance and control. The surveys collected screening indoor radon measurements,
defined as 2-7 day measurements using charcoal canister radon detectors placed in the lowest
livable area of the home. The target population for the surveys included owner-occupied
single family, detached housing units (White and others, 1989), although attached structures
such as duplexes, townhouses, or condominiums were included in some of the surveys if they
met the other criteria and had contact with the ground surface. Participants were selected
randomly from telephone-directory listings. In total, approximately 60,000 homes were tested
in the State/EPA surveys.
The second source of indoor radon data comes from residential surveys that have been
conducted in a specific state or region of the country (e.g. independent state surveys or utility
company surveys). Several states, including Delaware, Florida, Illinois, New Hampshire, New
Jersey, New York, Oregon, and Utah, have conducted their own surveys of indoor radon. The
quality and design of a state or other independent survey are discussed and referenced where
the data are used.
II-9 Reprinted from USGS Open-File Report 93-292
-------
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Data for only those counties with five or more measurements are shown in the indoor
radon maps in the state chapters, although data for all counties with a nonzero number of
measurements are listed in the indoor radon data tables in each state chapter. In total, indoor
radon data from more than 100,000 homes nationwide were used in the compilation of these
assessments. Radon data from State or regional indoor radon surveys, public health
organizations, or other sources are discussed in addition to the primary data sources where
they are available. Nearly all of the data used in these evaluations represent short-term (2-7
day) screening measurements from the lowest livable space of the homes. Specific details
concerning the nature and use of indoor radon data sets other than the State/EPA Residential
Radon Survey are discussed in the individual State chapters.
RADON INDEX AND CONFIDENCE INDEX
Many of the geologic methods used to evaluate an area for radon potential require
subjective opinions based on the professional judgment and experience of the individual
geologist. The evaluations are nevertheless based on established scientific principles that are
universally applicable to any geographic area or geologic setting. This section describes the
methods and conceptual framework used by the U.S. Geological Survey to evaluate areas for
radon potential based on the five factors discussed in the previous sections. The scheme is
divided into two basic parts, a Radon Index (RI), used to rank the general radon potential of
the area, and the Confidence Index (CI), used to express the level of confidence in the
prediction based on the quantity and quality of the data used to make the determination. This
scheme works best if the areas to be evaluated are delineated by geologically-based
boundaries (geologic provinces) rather than political ones (state/county boundaries) in which
the geology may vary across the area.
Radon Index. Table 1 presents the Radon Index (RI) matrix. The five factors—indoor
radon data, geology, aerial radioactivity, soil parameters, and house foundation type—were
quantitatively ranked (using a point value of 1, 2, or 3) for their respective contribution to
radon potential in a given area. At least some data for the 5 factors are consistently available
for every geologic province. Because each of these main factors encompass a wide variety of
complex and variable components, the geologists performing the evaluation relied heavily on
their professional judgment and experience in assigning point values to each category and in
determining the overall radon potential ranking. Background information on these factors is
discussed in more detail in the preceding sections of this introduction.
Indoor radon was evaluated using unweighted arithmetic means of the indoor radon data
for each geologic area to be assessed. Other expressions of indoor radon levels in an area
also could have been used, such as weighted averages or annual averages, but these types of
data were not consistently available for the entire United States at the time of this writing, or
the schemes were not considered sufficient to provide a means of consistent comparison
across all areas. For this report, charcoal-canister screening measurement data from the
State/EPA Residential Radon Surveys and other carefully selected sources were used, as
described in the preceding section. To maintain consistency, other indoor radon data sets
(vendor, state, or other data) were not considered in scoring the indoor radon factor of the
Radon Index if they were not randomly sampled or could not be statistically combined with
the primary indoor radon data sets. However, these additional radon data sets can provide a
means to further refine correlations between geologic factors and radon potential, so they are
II-11 Reprinted from USGS Open-File Report 93-292
-------
TABLE 1. RADON INDEX MATRIX, "ppm ell" indicates parts per million of equivalent
uranium, as indicated by NURE aerial radiometric data. See text discussion for details.
FACTOR
INDOOR RADON (average)
AERIAL RADIOACTIVITY
GEOLOGY*
SOIL PERMEABILITY
ARCHITECTURE TYPE
INCREASING RADON POTENTIAL ^
POINT VALUE
1
<2pCi/L
< 1.5 ppm elJ
negative
low
mostly slab
2
2-4pCi/L
1.5 - 2.5 ppm eU
variable
moderate
mixed
3
>4pCi/L
> 2.5 ppm eU
positive
high
mostly basement
"GEOLOGIC FIELD EVIDENCE (GFE) POINTS: GFE points are assigned in addition to points
for the "Geology" factor for specific, relevant geologic field studies. See text for details.
Geologic evidence supporting: HIGH radon +2 points
MODERATE +1 point
LOW -2 points
No relevant geologic field studies 0 points
SCORING:
Radon potential category
Point ranee
Probable average screening
indoor radon for area
LOW
MODERATE/VARIABLE
HIGH
3-8 points
9-11 points
12-17 points
<2pCi/L
2-4pCi/L
>4pCi/L
POSSIBLE RANGE OF POINTS = 3 to 17
TABLE 2. CONFIDENCE INDEX MATRIX
INCREASING CONFIDENCE
^
FACTOR
INDOOR RADON DATA
AERIAL RADIOACTIVITY
GEOLOGIC DATA
SOIL PERMEABILITY
POINT VALUE
1
sparse/no data
questionable/no data
questionable
questionable/no data
2
fair coverage/quality
glacial cover
variable
variable
3
good coverage/quality
no glacial cover
proven geol. model
reliable, abundant
SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10 -12 points
POSSIBLE RANGE OF POINTS = 4 to 12
H-12
Reprinted from USGS Open-File Report 93-292
-------
included as supplementary information and are discussed in the individual State chapters. If
the average screening indoor radon level for an area was less than 2 pCi/L, the indoor radon
factor was assigned 1 point, if it was between 2 and 4 pCi/L, it was scored 2 points, and if
the average screening indoor radon level for an area was greater than 4 pCi/L, the indoor
radon factor was assigned 3 RI points.
Aerial radioactivity data used in this report are from the equivalent uranium map of the
conterminous United States compiled from NURE aerial gamma-ray surveys (Duval and
others, 1989). These data indicate the gamma radioactivity from approximately the upper 30
cm of rock and soil, expressed in units of ppm equivalent uranium. An approximate average
value of eU was determined visually for each area and point values assigned based on
whether the overall eU for the area falls below 1.5 ppm (1 point), between 1.5 and 2.5 ppm
(2 points), or greater than 2.5 ppm (3 points).
The geology factor is complex and actually incorporates many geologic characteristics. In
the matrix, "positive" and "negative" refer to the presence or absence and distribution of rock
types known to have high uranium contents and to generate elevated radon in soils or indoors.
Examples of "positive" rock types include granites, black shales, phosphatic rocks, and other
rock types described in the preceding "geologic data" section. Examples of "negative" rock
types include marine quartz sands and some clays. The-term "variable" indicates that the
geology within the region is variable or that the rock types in the area are known or suspected
to generate elevated radon in some areas but not in others due to compositional differences,
climatic effects, localizeddistribution of uranium, or other factors. Geologic information
indicates not only how much uranium is present in the rocks and soils but also gives clues for
predicting general radon emanation and mobility characteristics through additional factors
such as structure (notably the presence of faults or shears) and geochemical characteristics
(for example, a phosphate-rich sandstone will likely contain more uranium than a sandstone
containing little or no phosphate because the phosphate forms chemical complexes with
uranium). "Negative", "variable", and "positive" geology were assigned 1, 2, and 3 points,.
respectively.
In cases where additional reinforcing or contradictory geologic evidence is available,
Geologic Field Evidence (GFE) points were added to or subtracted from an area's score
(Table 1). Relevant geologic field studies are important to enhancing our understanding of
how geologic processes affect radon distribution. In some cases, geologic models and
supporting field data reinforced an already strong (high or low) score; in others, they provided
important contradictory data. GFE points were applied for geologically-sound evidence that
supports the prediction (but which may contradict one or more factors) on the basis of known
geologic field studies in the area or in areas with geologic and climatic settings similar
enough that they could be applied with full confidence. For example, areas of the Dakotas,
Minnesota, and Iowa that are covered with Wisconsin-age glacial deposits exhibit a low aerial
radiometric signature and score only one RI point in that category. However, data from
geologic field studies in North Dakota and Minnesota (Schumann and others, 1991) suggest
that eU is a poor predictor of geologic radon potential in this area because radionuclides have
II-13 Reprinted from USGS Open-File Report 93-292
-------
been leached from the upper soil layers but are present and possibly even concentrated in
deeper soil horizons, generating significant soil-gas radon. This positive supporting field
evidence adds two GFE points to the score, which helps to counteract the invalid conclusion
suggested by the radiometric data. No GFE point? are awarded if there are no documented
field studies for the area.
"Soil permeability" refers to several soil characteristics that influence radon concentration
and mobility, including soil type, grain size, structure, soil moisture, drainage, slope, and
permeability. In the matrix, "low" refers to permeabilities less than about 0.6 in/hr; "high"
corresponds to greater than about 6.0 in/hr, in U.S. Soil Conservation Service (SCS) standard
soil percolation tests. The SCS data are for water permeability, which generally correlates
well with the gas permeability of the soil except when the soil moisture content is very high.
Areas with consistently high water tables were thus considered to have low gas permeability.
"Low, "moderate", and "high" permeability were assigned 1, 2, and 3 points, respectively.
Architecture type refers to whether homes in the area have mostly basements (3 points),
mostly slab-on-grade construction (1 point), or a mixture of the two. Split-level and crawl
space homes fall into the "mixed" category (2 points). Architecture information is necessary
to properly interpret the indoor radon data and produce geologic radon potential categories
that are consistent with screening indoor radon data.
The overall RI for an area is calculated by adding the individual RI scores for the 5
factors, plus or minus GFE points, if any. The total RI for an area falls in one of three
categories—low, moderate or variable, or high. The point ranges for the three categories were
determined by examining the possible combinations of points for the 5 factors and setting
rules such that a majority (3 of 5 factors) would determine the final score for the low and
high categories, with allowances for possible deviation from an ideal score by the other two
factors. The moderate/variable category lies between these two ranges. A total deviation of 3
points from the "ideal" score was considered reasonable to allow for natural variability of
factors—if two of the five factors are allowed to vary from the "ideal" for a category, they
can differ by a minimum of 2 (1 point different each) and a maximum of 4 points (2 points
different each). With "ideal" scores of 5, 10, and 15 points describing low, moderate, and
high geologic radon potential, respectively, an ideal low score of 5 points plus 3 points for
possible variability allows a maximum of 8 points in the low category. Similarly, an ideal
high score of 15 points minus 3 points gives a minimum of 12 points for the high category.
Note, however, that if both other factors differ by two points from the "ideal", indicating
considerable variability in the system, the total point score would lie in the adjacent (i.e.,
moderate/variable) category.
Confidence Index. Except for architecture type, the same factors were used to establish a
Confidence Index (CI) for the radon potential prediction for each area (Table 2). Architecture
type was not included in the confidence index because house construction data are readily and
reliably available through surveys taken by agencies and industry groups including the
National Association of Home Builders, U.S. Department of Housing and Urban
Development, and the Federal Housing Administration; thus it was not considered necessary
11-14 Reprinted from USGS Open-File Report 93-292
-------
to question the quality or validity of these data. The other factors were scored on the basis of
the quality and quantity of the data used to complete the RI matrix.
Indoor radon data were evaluated based on the distribution and number of data points and
on whether the data were collected by random sampling (State/EPA Residential Radon Survey
or other state survey data) or volunteered vendor data (likely to be nonrandom and biased
toward population centers and/or high indoor radon levels). The categories listed in the CI
matrix for indoor radon data ("sparse or no data", "fair coverage or quality", and "good
coverage/quality") indicate the sampling density and statistical robustness of an indoor radon
data set. Data from the State/EPA Residential Radon Survey and statistically valid state
surveys were typically assigned 3 Confidence Index points unless the data were poorly
distributed or absent in the area evaluated.
Aerial radioactivity data are available for all but a few areas of the continental United
States and for part of Alaska. An evaluation of the quality of the radioactivity data was based
on whether there appeared to be a good correlation between the radioactivity and the actual
amount of uranium or radium available to generate mobile radon in the rocks and soils of the
area evaluated. In general, the greatest problems with correlations among eU, geology, and
soil-gas or indoor radon levels were associated with glacial deposits (see the discussion in a
previous section) and typically were assigned a 2-point Confidence Index score. Correlations
among eU, geology, and radon were generally sound in unglaciated areas and were usually
assigned 3 CI points. Again, however, radioactivity data in some unglaciated areas may have
been assigned fewer than 3 points, and in glaciated areas may be assigned only -one point, if
the data were considered questionable or if coverage was poor.
To assign Confidence Index scores for the geologic data factor, rock types and geologic
settings for which a physical-chemical, process-based understanding of radon generation and
mobility exists were regarded as having "proven geologic models" (3 points); a high
confidence could be held for predictions in such areas. Rocks for which the processes are
less well known or for which data are contradictory were regarded as "variable" (2 points),
and those about which little is known or for which no apparent correlations have been found
were deemed "questionable" (1 point).
The soil permeability factor was also scored based on quality and amount of data. The
three categories for soil permeability in the Confidence Index are similar in concept, and
scored similarly, to those for the geologic data factor. Soil permeability can be roughly
estimated from grain size and drainage class if data from standard, accepted soil percolation
tests are unavailable; however, the reliability of the data would be lower than if percolation
test figures or other measured permeability data are available, because an estimate of this type
does not encompass all the factors that affect soil permeability and thus may be inaccurate in
some instances. Most published soil permeability data are for water; although this is
generally closely related to the air permeability of the soil, there are some instances when it
may provide an incorrect estimate. Examples of areas in which water permeability data may
not accurately reflect air permeability include areas with consistently high levels of soil
moisture, or clay-rich soils, which would have a low water permeability but may have a
11-15 Reprinted from USGS Open-File Report 93-292
-------
significantly higher air permeability when dry due to shrinkage cracks in the soil. These
additional factors were applied to the soil permeability factor when assigning the RI score, but
may have less certainty in some cases and thus would be assigned a lower CI score.
The Radon Index and Confidence Index give a general indication of the relative
contributions of the interrelated geologic factors influencing radon generation and transport in
rocks and soils, and thus, of the potential for elevated indoor radon levels to occur in a
particular area. However, because these reports are somewhat generalized to cover relatively
large areas of States, it is highly recommended that more detailed studies be performed in
local areas of interest, using the methods and general information in these booklets as a guide.
11-16 Reprinted from USGS Open-File Report 93-292
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and indoor radon with geology hi glacially derived soils of the northern Great Plains, in
Proceedings of the 1990 International Symposium on Radon and Radon Reduction
Technology, Volume 2, Symposium Oral Papers: U.S. Environmental Protection Agency
report EPA/600/9-9 l/026b, p. 6-23-6-36.
II-18 Reprinted from USGS Open-File Report 93-292
-------
-------
Schumann, R.R., Owen, D.E., and Asher-Bolinder, S., 1992, Effects of weather and soil
characteristics on temporal variations in soil-gas radon concentrations, in Gates, A.E., and
Gundersen, L.C.S., eds., Geologic controls on radon: Geological Society of America
Special Paper 271, p. 65-72.
Sextro, R.G., Moed, B.A., Nazaroff, W.W., Revzan, K.L., and Nero, A.V., 1987,
Investigations of soil as a source of indoor radon, in Hopke, P.K., ed., Radon and its
decay products: American Chemical Society Symposium Series 331, p. 10-29.
Sterling, R., Meixel, G., Shen, L., Labs, K., and Bligh, T., 1985, Assessment of the energy
savings potential of building foundations research: Oak Ridge, Term., U.S. Department of
Energy Report ORNL/SUB/84-0024/1.
Smith, R.C., H, Reilly, M.A., Rose, A.W., Barnes, J.H., and Berkheiser, S.W., Jr., 1987,
Radon: a profound case: Pennsylvania Geology, v. 18, p. 1-7.
Tanner, A.B., 1964, Radon migration in the ground: a review, in Adams, J.A.S., and Lowder,
W.M., eds., The natural radiation environment: Chicago, HI., University of Chicago
Press, p. 161-190.
Tanner, A.B., 1980, Radon migration in the ground: a supplementary review, in Gesell, T.F.,
and Lowder, W.M. (eds), Natural radiation environment HI, Symposium proceedings,
Houston, Texas, v. 1, p. 5-56.
U.S. Department of Agriculture, 1987, Principal kinds of soils: Orders, suborders, and great
groups: U.S. Geological Survey, National Atlas of the United States of America, sheet
38077-BE-NA-07M-00, scale 1:7,500,000.
U.S. Department of Energy, 1976, National Uranium Resource Evaluation preliminary report,
prepared by the U.S. Energy Research and Development Administration, Grand Junction,
Colo.: GJO-11(76).
Wanty, Richard B., and Schoen, Robert, 1991, A review of the chemical processes affecting the
mobility of radionuclides in natural waters, with applications, in Gundersen, Linda C.S.,
and Richard B. Wanty, eds., Field studies of radon in rocks, soils, and water: U.S.
Geological Survey Bulletin no. 1971, p. 183-194.
Washington, J.W., and Rose, A.W., 1990, Regional and temporal relations of radon in soil gas to
soil temperature and moisture: Geophysical Research Letters, v. 17, p. 829-832.
White, S.B., Bergsten, J.W., Alexander, B.V., and Ronca-Battista, ML, 1989, Multi-State
surveys of indoor 222Rn: Health Physics, v. 57, p. 891-896.
JJ-19 Reprinted from USGS Open-File Report 93-292
-------
APPENDIX A
GEOLOGIC TIME SCALE
Subdivisions (and their symbols)
Eon or
Eonothem
Phanerozoic2
Proterozoic
(B)
Archean
(A)
Era or
• Erathem
Ceno:oie2
(Cz)
Mesozoic2
(VW
Paleozoic
(Pi)
H^Sl**
Mioai*
£«rty
•JSR.W,
Miaax
Are*:E.ui
Period, System,
Subperiod, Subsystem
Quaternary2
IQ)
Neoeene z
Subperiod or
Tf~:.-f Subsystem IN)
m Paleogene2
1 ' Subperiod or
Subsystem (Pi)
Cretaceous
(K)
Jurassic
(J)
Triassic
05)
Permian
(P)
Pennsylvanian
Carboniferous "?'
(C) Mississippian
(M)
Devonian
(D)
Silurian
(S)
Ordovician
n m.y. used for a*
""^M^'powT. midd... upper or e.riy. middte. late) when used with these hems an informal division, of the ^ unit: the
first toner of the modifier is lowercase.
3 Rocks older than 570 M» also wiled Precambrian (p€). a time term without specific rank.
'Informal time term without specific rank.
USGS Open-File Report 93-292
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-------
APPENDIX B
GLOSSARY OF TERMS
Units of measure
pCi/L (picocuries per liter)- a unit of measure of radioactivity used to describe radon
concenttations in a volume of air. One picocurie (10-12 curies) is equal to about 2.2 disintegrations
of radon atoms per minute. A liter is about 1.06 quarts. The average concentration of radon in
U.S. homes measured to date is between 1 and 2 pCi/L.
Bq/m3 (Becquerels per cubic meter)- a metric unit of radioactivity used to describe radon
concentrations in a volume of air. One becquerel is equal to one radioactive disintegration per
second. One pCi/L is equal to 37 Bq/m3.
ppm (parts per million)- a unit of measure of concentration by weight of an element in a
substance, in this case, soil or rock. One ppm of uranium contained in a ton of rock .coir
rtion of uranium in soils in the U
substance, in this case, soil or rock. One ppm o uranum conaine in a .
to about 0.03 ounces of uranium. The average concentration of uranium in soils in the United
States is between 1 and 2 ppm.
in/hr (inches per hour)- a unit of measure used by soil scientists and engineers to de«ribe the
permeability of a soil to water flowing through it It is measured by digging a hole si f oot (12
inches) square and one foot deep, filling it with water, and measuring the time it tekes for the water
to drain from the hole. The drop in height of the water level in the hole, measured in inches, is
then divided by the time (in hours) to determine the permeability Soils range in Permeabikt? from
less than 0.06 in/hr to greater than 20 in/hr, but most soils in the United States have permeabilities
between these two extremes.
Geologic terms and terms related to the study of radon
aerial radiometric, aeroradiometric survey A survey of radioactivity, usually gamma rays,
taken by an aircraft carrying a gamma-ray .spectrometer pointed at the ground surface.
alluvial fan A low, widespread mass of loose rock and soil material, shaped like an open fan
and deposited by a stream at the point where it flows from a narrow mountain valley out onto a
plain or broader valley. May also form at the junction with larger streams or when the gradient of
the stream abruptly decreases.
alluvium, alluvial General terms referring to unconsolidated detrital material deposited by a
stream or other body of running water.
alpha-track detector A passive radon measurement device consisting of a plastic filiri that.is
sensitive to alpha particles. The film is etched with acid in a laboratory after it is exposed. The
Sing reveals scratches, or "tracks", left by the alpha particles resulting from radon decay, which
can then be counted to calculate the radon concentration. Useful for long-term (1-12 montnsj
radon tests.
amphibolite A mafic metamoiphic rock consisting mainly of pyroxenes and(or) amphibole and
plagioclase.
n-21 Reprinted firom USGS Open-File Report 93-292
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argillite, argillaceous Terms referring to a rock derived from clay or shale, or any sedimentary
rock containing an appreciable amount of clay-size material, i.e., argillaceous sandstone.
arid Term describing a climate characterized by dryness, or an evaporation rate that exceeds the
amount of precipitation.
basalt A general term for a dark-colored mafic igneous rocks that may be of extrusive origin,
such as volcanic basalt flows, or intrusive origin, such as basalt dikes.
batholith A mass of plutonic igneous rock that has more than 40 square miles of surface
exposure and no known bottom.
carbonate A sedimentary rock consisting of the carbonate (COs) compounds of calcium,
magnesium, or iron, e.g. limestone and dolomite.
carbonaceous Said of a rock or sediment that is rich in carbon, is coaly, or contains organic
matter.
charcoal canister A passive radon measurement device consisting of a small container of
granulated activated charcoal that is designed to adsorb radon. Useful for short duration (2-7 days)
measurements only. May be referred to as a "screening" test
chert A hard, extremely dense sedimentary rock consisting dominantly of interlocking crystals of
quartz. Crystals are not visible to the naked eye, giving the rock a milky, dull luster. It may be
white or gray but is commonly colored red, black, yellow, blue, pink, brown, or green.
clastic pertaining to a rock or sediment composed of fragments that are derived from preexisting
rocks or minerals. The most common clastic sedimentary rocks are sandstone and shale.
clay A rock containing clay mineral fragments or material of any composition having a diameter
less than 1/256 mm.
clay mineral One of a complex and loosely defined group of finely crystalline minerals made up
of water, silicate and aluminum (and a wide variety of other elements). They are formed chiefly by
alteration or weathering of primary silicate minerals. Certain clay minerals are noted for their small
size and ability to absorb substantial amounts of water, causing them to swell. The change in size
that occurs as these clays change between dry and wet is referred to as their "shrink-swell"
potential.
concretion A hard, compact mass of mineral matter, normally subspherical but commonly
irregular in shape; formed by precipitation from a water solution about a nucleus or center, such as
a leaf, shell, bone, or fossil, within a sedimentary or fractured rock.
conglomerate A coarse-grained, clastic sedimentary rock composed of rock and mineral
fragments larger than 2 mm, set in a finer-grained matrix of clastic material.
cuesta A hill or ridge with a gentle slope on one side and a steep slope on the other. The
formation of a cuesta is controlled by the different weathering properties and the structural dip of
the rocks forming the hill or ridge.
daughter product A nuclide formed by the disintegration of a radioactive precursor or "parent"
atom.
H-22 Reprinted from USGS Open-File Report 93-292
-------
delta, deltaic Referring to a low, flat, alluvial tract of land having a triangular or fan shape,
located at or near the mouth of a river. It results from the accumulation of sediment deposited by a
river at the point at which the river loses its ability to transport the sediment, commonly where a
river meets a larger body of water such as a lake or ocean.
dike A tabular igneous intrusion of rock, younger than the surrounding rock, that commonly cuts
across the bedding or foliation of the rock it intrudes.
diorite A plutonic igneous rock that is medium in color and contains visible dark minerals that
make up less than 50% of the rock. It also contains abundant sodium plagioclase and minor
quartz.
dolomite A carbonate sedimentary rock of which more than 50% consists of the mineral dolomite
(CaMg(CO3)2), and is commonly white, gray, brown, yellow, or pinkish in color.
drainage The manner in which the waters of an area pass, flow off of, or flow into the soil.
Also refers to the water features of an area, such as lakes and rivers, that drain it
eolian Pertaining to sediments deposited by the wind.
esker A long, narrow, steep-sided ridge composed of irregular beds of sand and gravel deposited
by streams beneath a glacier and left behind when the ice melted.
evapotranspiration Loss of water from a land area by evaporation from the soil and
transpiration from plants.
extrusive Said of igneous rocks that have been erupted onto the surface of the Earth.
fault A fracture or zone of fractures in rock or sediment along which there has been movement.
fluvial, fluvial deposit Pertaining to sediment that has been deposited by a river or stream.
foliation A linear feature in a rock defined by both mineralogic and structural characteristics. It
may be formed during deformation or metamorphism.
formation A mappable body of rock having similar characteristics.
glacial deposit Any sediment transported and deposited by a glacier or processes associated
with glaciers, such as glaciofluvial sediments deposited by streams flowing from melting glaciers.
gneiss A rock formed by metamorphism in which bands and lenses of minerals of similar
composition alternate with bands and lenses of different composition, giving the rock a striped or
"foliated" appearance.
granite Broadly applied, any coarsely crystalline, quartz- and feldspar-bearing igneous plutonic
rock. Technically, granites have between 10 and 50% quartz, and alkali feldspar comprises at least
65% of the total feldspar.
gravel An unconsolidated, natural accumulation of rock fragments consisting predominantly of
particles greater than 2 mm in size.
heavy minerals Mineral grains in sediment or sedimentary rock having higher than average
specific gravity. May form layers and lenses because of wind or water sorting by weight and size
n-23 Reprinted from USGS Open-File Report 93-292
-------
and may be referred to as a "placer deposit" Some heavy minerals are magnetite, garnet, zircon,
monazite, and xenotime.
igneous Said of a rock or mineral that solidified from molten or partly molten rock material. It is
one of the three main classes in*o which re -'-s are divij •** the others tr 'ng sedimentary and
metamorphic.
intermontane A term that refers to an area between two mountains or mountain ranges.
intrusion, intrusive The processes of emplacement or injection of molten rock into pre-existing
rock. Also refers to the rock formed by intrusive processes, such as an "intrusive igneous rock .
kame A low mound, knob, hummock, or short irregular ridge formed by a glacial stream at the
margin of a melting glacier; composed of bedded sand and gravel.
karst terrain A type of topography that is formed on limestone, gypsum and other rocks by
dissolution of the rock by water, forming sinkholes and caves.
lignite A brownish-black coal that is intermediate in coalification between peat and
subbituminous coal.
limestone A carbonate sedimentary rock consisting of more than 50% calcium carbonate,
primarily in the form of the mineral calcite (CaCOs).
lithology The description of rocks in hand specimen and in outcrop on the basis of color,
composition, and grain size.
loam A permeable soil composed of a mixture of relatively equal parts clay, silt, and sand, and
usually containing some organic matter.
loess A fine-grained eolian deposit composed of silt-sized particles generally thought to have
been deposited from windblown dust of Pleistocene age.
mafic Term describing an igneous rock containing more than 50% dark-colored minerals.
marine Term describing sediments deposited in the ocean, or precipitated from ocean waters.
metamorphic Any rock derived from pre-existing rocks by mineralogical, chemical, or structural
changes in response to changes in temperature, pressure, stress, and the chemical environment
Phyllite, schist, amphibolite, and gneiss are metamorphic rocks.
moraine A mound, ridge, or other distinct accumulation of unsorted, unbedded glacial material,
predominantly till, deposited by the action of glacial ice.
outcrop That part of a geologic formation or structure that appears at the surface of the Earth, as
in "rock outcrop".
percolation test A term used in engineering for a test to determine the water permeability of a
soil. A hole is dug and filled with water and the rate of water level decline is measured.
permeability The capacity of a rock, sediment, or soil to transmit liquid or gas.
phosphate, phosphatic, phosphorite Any rock or sediment containing a significant amount
of phosphate minerals, i.e., minerals containing PO4-
n-24 Reprinted from USGS Open-File Report 93-292
-------
physiographic province A region in which all parts are similar in geologic structure and
climate, which has had a uniform geomorphic history, and whose topography or landforms differ
significantly from adjacent regions.
•Mpcer deposit See heavy minerals
residual Formed by weathering of a material in place.
residuum Deposit of residual material.
rhyolite An extrusive igneous rock of volcanic origin, compositionally equivalent to granite.
sandstone A clastic sedimentary rock composed of sand-sized rock and mineral material that is
more or less firmly cemented. Sand particles range from 1/16 to 2 mm in size.
schist A strongly foliated crystalline rock, formed by metamorphism, that can be readily split into
thin flakes or slabs. Contains mica; minerals are typically aligned.
screening level Result of an indoor radon test taken with a charcoal canister or similar device,
for a short period of time, usually less than seven days. May indicate the potential for an indoor
radon problem but does not indicate annual exposure to radon.
sediment Deposits of rock and mineral particles or fragments originating from material that is
transported by air, water or ice, or that accumulate by natural chemical precipitation or secretion of
organisms.
semiarid Refers to a climate that has slightly more precipitation than an arid climate.
shale A fine-grained sedimentary rock formed from solidification (Tithification) of clay or mud.
shear zone Refers to a roughly linear zone of rock that has been faulted by ductile or non-ductile
processes in which the rock is sheared and both sides are displaced relative to one another.
shrink-swell clay See clay mineral.
siltstone A fine-grained clastic sedimentary rock composed of silt-sized rock and mineral
material and more or less firmly cemented. Silt particles range from 1/16 to 1/256 mm in size.
sinkhole A roughly circular depression hi a karst area measuring meters to tens of meters in
diameter. It is funnel shaped and is formed by collapse of the surface material into an underlying
void created by the dissolution of carbonate rock.
slope An inclined part of the earth's surface.
solution cavity A hole, channel or cave-like cavity formed by dissolution of rock.
stratigraphy The study of rock strata; also refers to the succession of rocks of a particular area,
surficial materials Unconsolidated glacial, wind-, or waterborne deposits occurring on the
earth's surface.
tablelands General term for a broad, elevated region with a nearly level surface of considerable
extent.
11-25 Reprinted from USGS Open-File Report 93-292
-------
terrace gravel Gravel-sized material that caps ridges and terraces, left behind by a stream as it
cuts down to a lower level.
terrain A tract or region of the Earth's surface considered as a physical feature or an ecological
envkonment.
till Unsorted generally unconsolidated and unbedded rock and mineral^material deposited directly
^jacenfSunderneath a glacier, without reworking by meltwater. Size of grains vanes greatly
from clay to boulders.
uraniferous Containing uranium, usually more than 2 ppm.
vendor data Used in this report to refer to indoor radon data collected and measured by
commercial vendors of radon measurement devices and/or services.
volcanic Pertaining to the activities, structures, and extrusive rock types of a volcano.
water table The surface forming the boundary between the zone of saturation and the zone of
aeration; the top surface of a body of unconfined groundwater in rock or soil.
weathering The destructive process by which earth and rock materials, on exposure to
Smother! elements, are changed in color, texture, composition, firmness, or form with little or
no transport of the material.
IE-26 Reprinted from USGS Open-File Report 93-292
-------
APPENDIX C
EPA REGIONAL OFFICES
State
EPA Region
EPA Region 1
JFK Federal Building
Boston, MA 02203
(617) 565-4502
EPA Region 2
(2AIR:RAD)
26 Federal Plaza
New York, NY 10278
(212) 264-4110
Region 3 (3AH14)
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8326
EPA Region 4
345 Courtland Street, N.E.
Atlanta, GA 30365
(404) 347-3907
EPA Region 5 (5AR26)
77 West Jackson Blvd.
Chicago, IL 60604-3507
(312) 886-6175
EPA Region 6 (6T-AS)
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7224
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7604
EPA Region 8
(8HWM-RP)
999 18th Street
One Denver Place, Suite 1300
Denver, CO 80202-2413
(303) 293-1713
EPA Region 9 (A-3)
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1048
EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
(202) 442-7660
Alabama • 4
Alaska 10
Arizona 9
Arkansas 6
California 9
Colorado 8
Connecticut 1
Delaware 3
District of Columbia 3
Florida 4
Georgia 4
Hawaii 9
Idaho 10
Illinois 5
Indiana -.5
Iowa 1
Kansas : 7
Kentucky 4
Louisiana 6
Maine 1
Maryland 3
Massachusetts 1
Michigan 5
Minnesota 5
Mississippi 4
Missouri 1
Montana 8
Nebraska 7
Nevada 9
New Hampshire 1
New Jersey 2
New Mexico 6
New York 2
North Carolina 4
North Dakota 8
Ohio 5
Oklahoma 6
Oregon 1°
Pennsylvania 3
Rhode Island 1
South Carolina 4
South Dakota 8
Tennessee 4
Texas 6
Utah 8
Vermont 1
Virginia • 3
Washington 10
West Virginia 3
Wisconsin 5
Wyoming 8
n-27 Reprinted from USGS Open-FUe Report 93-292
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STATE RADON CONTACTS
May, 1993
Alabama James McNees
Division of Radiation Control
Alabama Department of Public Health
State Office Building
Montgomery, AL 36130
(205)242-5315
1-800-582-1866 in state
Alaska Chaiies Tedford
Department of Health and Social
Services
P.O. Box 110613
Juneau,AK 99811-0613
(907)465-3019
1-800-478-4845 in state
Arizona John Stewart
Arizona Radiation Regulatory Agency
4814 South 40th St
Phoenix, AZ 85040
(602) 255-4845
Arkansas Lee Gershner
Division of Radiation Control
Department of Health
4815 Markham Street, Slot 30
Little Rock, AR 72205-3867
(501) 661-2301
California J. David Quinton
Department of Health Services
714 P Street, Room 600
Sacramento, CA 94234-7320
(916) 324-2208
1-800-745-7236 in state
Colorado Linda Martin
Department of Health
4210 East llth Avenue
Denver, CO 80220
(303) 692-3057
1-800-846-3986 in state
Connecticut Alan J. Siniscalchi
Radon Program
Connecticut Department of Health
Services
150 Washington Street
Hartford, CT 061064474
(203) 566-3122
Delaware Marai G. Rejai
Office of Radiation Control
Division of Public Health
P.O. Box 637
Dover, DE 19903
(302) 736-3028
1-800-554-4636 In State
District
of Columbia
Rpbert Davis
DC Department of Consumer and
Regulatory Affairs
614 H Street NW
Room 1014
Washington, DC 20001
(202)727-71068
N. Michael Gilley
Office of Radiation Control
Department of Health and
Rehabilitative Services
1317 Winewood Boulevard
Tallahassee, FL 32399-0700
(904)488-1525
1-800-543-8279 in state
Richard Schreiber
Georgia Department of Human
Resources
878 Peachtree St, Room 100
Atlanta, GA 30309
(404) 894-6644
1-800-745-0037 in state
Hawaii Russell Takata
Environmental Health Services
Division
591 Ala Moana Boulevard
Honolulu, HI 96813-2498
(808) 586-4700
H-28 Reprinted from USGS Open-File Report 93-292
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Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
PatMcGavarn
Office of Environmental Health
450 West State Street
Boise, ID 83720
(208) 334-6584
1-800-445-8647 in state
Richard Allen
Illinois Department of Nuclear Safety
1301 Outer Park. Drive
Springfield, IL 62704
(217) 524-5614
1-800-325-1245 in state
Lorand Magyar
Radiological Health Section
Indiana State Department of Health
1330 West Michigan Street
P.O. Box 1964
Indianapolis, IN 46206
(317) 633-8563
1-800-272-9723 In State
Donald A. Plater
Bureau of Radiological Health
Iowa Department of Public Health
Lucas State Office Building
Des Moines, IA 50319-0075
(515) 281-3478
1-800-383-5992 In State
Harold Spiker
Radiation Control Program
Kansas Department of Health and
Environment
109 SW 9th Street
6th Floor Mills Building
Topeka, KS 66612
(913)296-1561
JeanaPhelps
Radiation Control Branch
Department of Health Services
Cabinet for Human Resources
275 East Main Street
Frankfort, KY 40601
(502) 564-3700
Louisiana Matt Schlenker
Louisiana Department of
Environmental Quality
P.O. Box 82135
Baton Rouge, LA 70884-2135
(504) 925-7042
1-800-256-2494 in state
Bob Stilwell
Division of Health Engineering
Department of Human Services
State House, Station 10
Augusta, ME 04333
(207) 289-5676
1-800-232-0842 in state
Maryland Leon J. Rachuba
Radiological Health Program
Maryland Department of the
Environment
2500 Broening Highway
Baltimore, MD 21224
(410)631-3301
1-800-872-3666 In State
Massachusetts William J. Bell
Radiation Control Program
Department of Public Health
23 Service Center
Northampton, MA 01060
(413) 586-7525
1-800-445-1255 in state
Michigan Sue Hendershott
Division of Radiological Health
Bureau of Environmental and
Occupational Health
3423 North Logan Street
P.O. Box 30195
Lansing, MI 48909
(517) 335-8194
Minnesota Laura Oatmann
Indoor Air Quality Unit
925 Delaware Street, SE
P.O. Box 59040
Minneapolis, MN 55459-0040
(612) 627-5480
1-800-798-9050 in state
n-29
Reprinted from USGS Open-File Report 93-292
-------
Mississippi Silas Anderson
Division of Radiological Health
Department of Health
3150 Lawson Street
P.O. Box 1700
Jackson, MS 39215-1700
(601) 354-6657
1-800-626-7739 in state
Missouri Kenneth V. Miller
Bureau of Radiological Health
Missouri Department of Health
1730 East Elm
P.O. Box 570
Jefferson City, MO 65102
(314)751-6083
1-800-669-7236 In State
Montana Adrian C. Howe
Occupational Health Bureau
Montana Department of Health and
Environmental Sciences
Cogswell Building A113
Helena, MT 59620
(406)444-3671
Nebraska Joseph Milone
Division of Radiological Health
Nebraska Department of Health
301 Centennial Mall, South
P.O. Box 95007
Lincoln, NE 68509
(402)471-2168
1-800-334-9491 In State
Nevada Stan Marshall
Department of Human Resources
505 East King Street
Room 203
Carson City, NV 89710
(702) 687-5394
New Hampshire David Chase
Bureau of Radiological Health
Division of Public Health Services
Health and Welfare Building
Six Hazen Drive
Concord, NH 03301
(603) 271^674
1-800-852-3345 x4674
New Jersey Tonalee Carlson Key
Division of Environmental Quality
Department of Environmental
Protection
CN415
Trenton, NJ 08625-0145
(609) 987-6369
1-800-648-0394 in state
New Mexico William M. Floyd
Radiation Licensing and Registration
Section
New Mexico Environmental
Improvement Division
1190 St. Francis Drive
Santa Fe,NM 87503
(505) 827-4300
New York William J. Condon
Bureau of Environmental Radiation
Protection
New York State Health Department
Two University Place
Albany, NY 12202
(518)458-6495
1-800-458-1158 in state
North Carolina Dr. Felix Fong
Radiation Protection Division
Department of Environmental Health
and Natural Resources
701 Barbour Drive
Raleigh, NC 27603-2008
(919) 571-4141
1-800-662-7301 (recorded info x4196)
North Dakota Arlen Jacobson
North Dakota Department of Health
1200 Missouri Avenue, Room 304
P.O. Box 5520
Bismarck, ND 58502-5520
(701)221-5188
Ohio Marcie Matthews
Radiological Health Program
Department of Health
1224 Kinnear Road - Suite 120
Columbus, OH 43212
(614) 644-2727
1-800-523-4439 in state
n-so
Reprinted from USGS Open-File Report 93-292
-------
Oklahoma Gene Smith
Radiation Protection Division
Oklahoma State Department of
Health
P.O. Box 53551
Oklahoma City, OK 73152
(405)271-5221
Oregon George Toombs
Department of Human Resources
Health Division
1400 SW 5th Avenue
Portland, OR 97201
(503) 731^014
Pennsylvania Michael Pyles
Pennsylvania Department of
Environmental Resources
Bureau of Radiation Protection
P.O. Box 2063
Harrisburg, PA 17120
(717) 783-3594
1-800-23-RADON In State
Puerto Rico David Saldana
Radiological Health Division
G.P.O. Call Box 70184
Rio Piedras, Puerto Rico 00936
(809) 767-3563
Rhode Island Edmund Arcand
Division of Occupational Health and
Radiation
Department of Health
205 Cannon Building
Davis Street
Providence, RI02908
(401) 277-2438
Smith Carolina
Bureau of Radiological Health
Department of Health and
Environmental Control
2600 Bull Street
Columbia, SC 29201
(803)734-4631
1-800-768-0362
South Dakota MikePochop
Division of Environment Regulation
Department of Water and Natural
Resources
Joe Foss Building, Room 217
523 E. Capitol
Pierre, SD 57501-3181
(605)773-3351
Tennessee Susie Shimek
Division of Air Pollution Control
Bureau of the Environment
Department of Environment and
Conservation
Customs House, 701 Broadway
Nashville, TN 37219-5403
(615) 532-0733
1-800-232-1139 in state
Texas Gary Smith
Bureau of Radiation Control
Texas Department of Health
1100 West 49th Street
Austin, TX 78756-3189
(512) 834-6688
Utah John Hultquist
Bureau of Radiation Control
Utah State Department of Health
288 North, 1460 West
P.O. Box 16690
Salt Lake City, UT 84116-0690
(801) 536-4250
Vermont Paul demons
Occupational and Radiological Health
Division
Vermont Department of Health
10 Baldwin Street
Montpelier, VT 05602
(802) 828-2886
1-800-640-0601 in state
Virgin Islands Contact the U.S. Environmental
Protection Agency, Region TJ
in New York
(212) 264-4110
II-31 Reprinted from USGS Open-File Report 93-292
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Virginia Shelly Ottenbrite
Bureau of Radiological Health
Department of Health
109 Governor Street
Richmond, VA 23219
(804) 786-5932
1-800-468-0138 in state
Washington Kate Coleman
Department of Health
Office of Radiation Protection
Airdustrial Building 5, LE-13
Olympia, WA 98504
(206) 753-4518
1-800-323-9727 In State
West Virginia Beattie L. DeBord
Industrial Hygiene Division
West Virginia Department of Health
151 llth Avenue
South Charleston, WV 25303
(304) 558-3526
1-800-922-1255 In State
Wisconsin Conrad Weiffenbach
Radiation Protection Section
Division of Health
Department of Health and Social
Services
P.O. Box 309
Madison, WI53701-0309
(608) 267-47%
1-800-798-9050 in state
Wyoming Janet Hough
Wyoming Department of Health and
Social Services
Halhway Building, 4th Floor
Cheyenne. WY 82002-0710
(307)777-6015
1-800-458-5847 in state
11-32 Reprinted from USGS Open-File Report 93-292
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STATE GEOLOGICAL SURVEYS
May, 1993
Alabama Ernest A. Mancini
Geological Survey of Alabama
P.O. Box 0
420 Hackberry Lane
Tuscaloosa, AL 35486-9780
(205) 349-2852
Alaska Thomas E. Smith
Alaska Division of Geological &
Geophysical Surveys
794 University Ave., Suite 200
Fairbanks, AK 99709-3645
(907)479-7147
Arizona Larry D. Fellows
Arizona Geological Survey
845 North Park Ave., Suite 100
Tucson, AZ 85719
(602) 882-4795
Arkansas Norman F. Williams
Arkansas Geological Commission
Vardelle Parham Geology Center
3815 West Roosevelt Rd.
Little Rock, AR 72204
(501) 324-9165
California James F. Davis
California Division of Mines &
Geology
801 K Street, MS 12-30
Sacramento, CA 95814-3531
(916) 445-1923
Colorado Pat Rogers (Acting)
Colorado Geological Survey
1313 Sherman St., Rm 715
Denver, CO 80203
(303)866-2611
Connecticut Richard C. Hyde
Connecticut Geological & Natural
History Survey
165 Capitol Ave., Rm. 553
Hartford, CT 06106
(203) 566-3540
Delaware Robert R. Jordan
Delaware Geological Survey
University of Delaware
101 Penny Hall
Newark, DE 19716-7501
(302) 831-2833
Florida Walter Schmidt
Florida Geological Survey
903 W. Tennessee St.
Tallahassee, FL 32304-7700
(904)488-4191
William H. McLemore
Georgia Geologic Survey
Rm. 400
19 Martin Luther King Jr. Dr. SW
Atlanta, GA 30334
(404) 656-3214
Hawaii Manabu Tagomori
Dept. of Land and Natural Resources
Division of Water & Land Mgt
P.O. Box 373
Honolulu, ffl 96809
(808) 548-7539
Idaho Earl H. Bennett
Idaho Geological Survey
University of Idaho
Morrill Hall, Rm. 332
Moscow, ID 83843
(208) 885-7991
Illinois Morris W. Leighton
Illinois State Geological Survey
Natural Resources Building
615 East Peabody Dr.
Champaign, IL 61820
(217) 333^747
Indiana Norman C. Hester
Indiana Geological Survey
611 North Walnut Grove
Bloomington, IN 47405
(812) 855-9350
Iowa Donald L. Koch
Iowa Department of Natural Resources
Geological Survey Bureau
109 Trowbridge Hall
Iowa City, IA 52242-1319
(319) 335-1575
Kansas LeeC.Gerhard
Kansas Geological Survey
1930 Constant Ave., West Campus
University of Kansas
Lawrence, KS 66047
(913)864-3965
n-33 Reprinted from USGS Open-File Report 93-292
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Kentucky Donald C. Haney
Kentucky Geological Survey
University of Kentucky
228 Mining & Mineral Resources
Building
Lexington, KY 40506-0107
(606) 257-5500
Louisiana William E. Marsalis
Louisiana Geological Survey
P.O. Box 2827
University Station
Baton Rouge, LA 70821-2827
(504) 388-5320
Maine Walter A, Anderson
Maine Geological Survey
Department of Conservation
State House, Station 22
Augusta, ME 04333
(207)289-2801
Maryland Emery T. Cleaves
Maryland Geological Survey
2300 St. Paul Street
Baltimore, MD 21218-5210
(410) 554-5500
Massachusetts Joseph A. Sinnott
Massachusetts Office of
Environmental Affairs
100 Cambridge St., Room 2000
Boston, MA 02202
(617) 727-9800
Michigan R. Thomas Segall
Michigan Geological Survey Division
Box 30256
Lansing, MI 48909
(517) 334-6923
Minnesota Priscilla C. Grew
Minnesota Geological Survey
2642 University Ave.
St Paul, MN 55114-1057
(612) 627-4780
Mississippi S. Cragin Knox
Mississippi Office of Geology
P.O. Box 20307
Jackson, MS 39289-1307
(601)961-5500
Missouri James H. Williams
Missouri Division of Geology &
Land Survey
111 Fairgrounds Road
P.O. Box 250
Rolla, MO 65401
(314) 368-2100
Montana Edward T. Ruppel
Montana Bureau of Mines & Geology
Montana College of Mineral Science
and Technology, Main Hall
Butte, MT 59701
(406)496^180
Nebraska Perry B. Wigley
Nebraska Conservation & Survey
Division
113 Nebraska Hall
University of Nebraska
Lincoln, ME 68588-0517
(402)472-2410
Nevada Jonathan G. Price
Nevada Bureau of Mines & Geology
Stop 178
University of Nevada-Reno
Reno, NV 89557-0088
(702) 784-6691
New Hampshire Eugene L. Boudette
Dept. of Environmental Services
117 James Hall
University of New Hampshire
Durham, NH 03824-3589
(603)862-3160
New Jersey Haig F. Kasabach
New Jersey Geological Survey
P.O. Box 427
Trenton, NJ 08625
(609) 292-1185
New Mexico Charles E. Chapin
New Mexico Bureau of Mines &
Mineral Resources
Campus Station
Socorro.NM 87801
(505) 835-5420
NewYork Robert H. Fakundiny
New York State Geological Survey
3136 Cultural Education Center
Empire State Plaza
Albany, NY 12230
(518)474-5816
IE-34 Reprinted from USGS Open-File Report 93-292
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North Carolina Charles H. Gardner
North Carolina Geological Survey
P.O. Box 27687
Raleigh, NC 27611-7687
(919) 733-3833
North Dakota John P. Bluemle
North Dakota Geological Survey
600 East Blvd.
Bismarck, ND 58505-0840
(701) 224^109
Ohio Thomas M. Berg
Ohio DepL of Natural Resources
Division of Geological Survey
4383 Fountain Square Drive
Columbus, OH 43224-1362
(614) 265-6576
Oklahoma Charles J. Mankin
Oklahoma Geological Survey
Room N-131, Energy Center
100E.Boyd
Norman, OK 73019-0628
(405)325-3031
Oregon Donald A. Hull
Dept. of Geology & Mineral Indust.
Suite 965
800 NE Oregon St. #28
Portland, OR 97232-2162
(503) 731-4600
Pennsylvania Donald M. Hoskins
Dept. of Environmental Resources
Bureau of Topographic & Geologic
Survey
P.O. Box 2357
Harrisburg.PA 17105-2357
(717) 787-2169
Puerto Rico Ram6n M. Alonso
Puerto Rico Geological Survey
Division
Box 5887
Puerta de Tierra Station
San Juan, P.R. 00906
(809) 722-2526
Rhode Island J. Allan Cain
Department of Geology
University of Rhode Island
315 Green Hall
Kingston, RI02881
(401) 792-2265
Utah
South Carolina Alan-Jon W. Zupan (Acting)
South Carolina Geological Survey
5 Geology Road
Columbia, SC 29210-9998
(803) 737-9440
South Dakota C.M. Christensen (Acting)
South Dakota Geological Survey
Science Center
University of South Dakota
Vermillion, SD 57069-2390
(605) 677-5227
Tennessee Edward T. Luther
Tennessee Division of Geology
13th Floor, L & C Tower
401 Church Street
Nashville, TN 37243-0445
(615) 532-1500
William L. Fisher
Texas Bureau of Economic Geology
University of Texas
University Station, Box X
Austin, TX 78713-7508
(512)471-7721
M. Lee Allison
Utah Geological & Mineral Survey
2363 S. Foothill Dr.
Salt Lake City, UT 84109-1491
(801)467-7970
Vermont Diane L.Conrad
Vermont Division of Geology and
Mineral Resources
103 South Main St.
Waterbury.VT 05671
(802)244-5164
Virginia Stanley S. Johnson
Virginia Division of Mineral
Resources
P.O. Box 3667
Charlottesvffle, VA 22903
(804)293-5121
Washington Raymond Lasmanis
Washington Division of Geology &
Earth Resources
Department of Natural Resources
P.O. Box 47007
Olympia, Washington 98504-7007
(206) 902-1450
11-35 Reprinted from USGS Open-File Report 93-292
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West Virginia Larry D. Woodfork
West Virginia Geological and
Economic Survey
Mont Chateau Research Center
P.O. Box 879
Morgantown.WV 26507-0879
(304) 594-2331
Wisconsin James Robertson
Wisconsin Geological & Natural
History Survey
3817 Mineral Point Road
Madison, WI 53705-5100
(608) 263-7384
Wyoming Gary B. Glass
Geological Survey of Wyoming
University of Wyoming
Box 3008, University Station
Laramie, WY 82071-3008
(307)766-2286
II-36 Reprinted from USGS Open-File Report 93-292
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EPA REGION 1 GEOLOGIC RADON POTENTIAL SUMMARY
by
Linda C.S. Gundersen, R. Randall Schumann, and Sandra L. Szarzi
US. Geological Survey
EPA Region 1 includes the states of Connecticut, Maine, Massachusetts, New Hampshire,
Rhode Island, and Vermont For each state, geologic radon potential areas were delineated and
ranked on the basis of geology, soil, housing construction, indoor radon, and other factors. Areas
in which the average screening indoor radon level of all homes within the area is estimated to be
greater than 4 pCi/L were ranked high. Areas in which the average screening indoor radon level
of all homes within the area is estimated to be between 2 and 4 pCi/L were ranked
moderate/variable, and areas in which the average screening indoor radon level of all homes within
the area is estimated to be less than 2 pCi/L were ranked low. Information on the data used and on
the radon potential ranking scheme is given in the introduction to this volume. More detailed
information on the geology and radon potential of each state in Region 1 is given in the individual
state chapters. The individual chapters describing the geology and radon potential of the states in
Region 1, though much more detailed than this summary, still are generalized assessments and
there is no substitute for having a home tested. Within any radon potential area homes with indoor
radon levels both above and below the predicted average likely will be found.
Figure 1 shows a generalized map of the physiographic/geologic provinces in Region 1.
The following summary of radon potential in Region 1 is based on these provinces. Figure 2
shows average screening indoor radon levels by county, calculated from the State/EPA Residential
Radon Survey data. Figure 3 shows the geologic radon potential of areas in Region 1, combined
and summarized from the individual state chapters.
CONNECTICUT
The Western Uplands of western Connecticut comprise several terranes underlain by
metamorphosed sedimentary and igneous rocks. Soils developed on the Proterozoic massifs and
overlying till in the Proto-North American Terrane (area 23, fig. 1) have moderate to high
permeability. Equivalent uranium is generally low and indoor radon averaged 2.5 pCi/L over the
massifs. The carbonate shelf rocks of the Proto-North American Terrane (23, fig. 1) are
predominantly marble, schist, and quartzite, all overlain in places by glacial till. Indoor radon
averaged 2.8 pCi/L for homes built on the carbonate shelf rocks. Some homes built on parts of the
Stockbridge Marble have elevated indoor radon levels. The Taconic Allochthons (24, 25, fig. 1)
underlie several fault-bounded areas in the northern part of the Western Uplands. The dominant
rock type is schist of varying composition. Equivalent Uranium is generally moderate and
permeability is low to moderate in this area. Indoor radon in the Taconic Allochthons averaged
2.7 pCi/L. Overall, these terranes have moderate radon potential.
Rocks of the Connecticut Valley Synclinorium (26, fig. 1) underlie most of the Western
Uplands. These rocks are schist, gneiss, granite, and phyllite, predominantly granitic or
aluminous in composition. Equivalent uranium is moderate to high with areas of very high
equivalent uranium over granitic gneisses in the southern portion. The Pinewood Adamellite has
high radioactivity and generates locally elevated indoor radon levels. Other granites and granitic
gneisses associated with elevated indoor radon include the Harrison Gneiss, an Ordovician granite
gneiss, and the Shelton Member of the Trap Falls Formation. These rocks all occur mainly in the
ffl-1 Reprinted from USGS Open-File Report 93-292-A
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LAKE N /
CHAMPLAIN
23'
47-
Figure 1. Geologic radon potential areas of EPA Region 1. 1,5-Melange; 2-Seboomook Formation-
3-Metasedimentary rocks, predominantly carbonates; 4-Granite and high-grade metamorphic rocks; 67811-Glacial
lake clay, marine clay; 9,10-Penobscot Formation, granites, and minor metamorphic rocks; 12-Boundary Mountains
Terrane; 13-Gander Terrane; 14-Avalonian Composite Terrane; 15-Northeastern Highlands; 16-Vermont Piedmont-
17-Green Mountains; 18-Champlain Lowland; 19-Vermont Valley; 20,21-Taconic Mountains-Stockbridee Valley'
22-Berkshire Mountains; 23-Proto-North American Terrane; 24,25-Taconic AUochthons; 26-Connecticut Valley
Syncbnonum; 27-Western Connecticut Valley Belt; 28,29-Connecticut Valley (Mesozoic Basins); 30-Gneissic domes
of the Eastern Connecticut Valley Belt; 31-Bronson Hill AnticUnorium; 32,33-Merrimack Synclinorium- 34 35 37 38
40-Avalonian Terrene (includes Hope Valley subterrane); 36-Nashoba and Rhode Island Terranes; 39,44 46-Esmond-'
Dedham Terrane; 41-Newbuiy Basin volcanics; 42-Cape Ann and Peabody plutons; 43-Boston Basin-
45-Narrangansett Basin; 47-Coastal Plain.
-------
Bsmt. & 1st Floor Rn
Average Concentration (pCi/L)
0.0 to 1.9
2.0 to 4.0
4.1 to 6.0
3 E3 6.1 to 9.1
1 u Missing Data
100 Miles
Figure 2. Average screening indoor radon levels, by county, for EPA Region 1. Data are from
2-7 day charcoal canister tests. Data from the EPA/State Residential Radon Survey, except for
New Hampshire data, which are from the New Hampshire Division of Public Health Services
radon survey. Histograms in map legend show the number of counties in each category.
-------
GEOLOGIC RADON POTENTIAL
I I LOW (<2 pCi/L)
E£3 MODERATE/VARIABLE (2-4 pCi/L)
HIGH (>4 pCi/L)
Figure 3. Geologic radon potential areas of EPA Region 1. For more detail, refer to individual
state radon potential chapters.
-------
southern part of the Connecticut Valley Synclinorium and are associated with the high radioactivity
and with elevated indoor radon. The Nonewaug Granite and the Scranton Member of the Taine
Mountain Formation are also associated with high aeroradioactivity and elevated indoor radon
levels. Graphitic schist and phyllites may be the cause of elevated indoor radon levels associated
with the Wepawaug Schist. Soils are derived from the rocks and overlying tills and have low to
moderate permeability. Indoor radon averages 3.5 pCi/L in the Connecticut Valley Synclinorium.
Because many of the rocks of this terrane have the potential to generate elevated radon levels, this
area is assigned a high geologic radon potential.
The Central Lowlands of Connecticut (29, fig. 1) are underlain by Triassic and Jurassic
sedimentary and volcanic rocks of the Newark Terrane. The average indoor radon in the Central
Lowlands was 1.6 pCi/L. Radioactivity in the Hartford and Pomperaug basins is generally low
and the soils have generally low to moderate permeability or are poorly drained. Overall, the
Central Lowlands have a low radon potential. However, localized uranium occurrences in the
upper New Haven Arkose, the middle Portland Formation, and possibly in the Shuttle Meadow,
East Berlin, and Portland Formations could generate locally elevated indoor radon levels, but they
are not expected to be common or widespread.
Rocks of the Bronson Hill Anticlinorium, in the Eastern Uplands of Connecticut (31,
fig. 1), include felsic and mafic schists and gneisses, quartzite, and granite gneiss. Radioactivity
in the Bronson Hill is moderate to locally high, and equivalent uranium anomalies in the central
part of the area appear to be associated with outcrops of granite gneiss. The soils have low to
moderate permeability with areas of locally high permeability. The Glastonbury granite gneiss and
graphitic schists in the Collins Hill Formation are likely to generate elevated indoor radon levels.
The Monson Gneiss, and schist and granofels of the Middletown Formation, also generate high
average indoor radon levels. Average indoor radon in the Bronson Hill Anticlinorium is
5.6 pCi/L, the highest among the geologic terranes of Connecticut. Overall, this area has a high
radon potential.
The Merrimack Synclinorium, in the central part of the Eastern Uplands (33, fig. 1), is
underlain by gneiss, schist, granofels, and quartzite that are intruded by granite gneiss, diorite, and
gabbro. The area has moderate to high radioactivity. Soils have low to high permeability but most
are in the low to moderate range. Indoor radon in the Merrimack Synclinorium averaged 2.7
pCi/L. The Canterbury granite gneiss, which occurs in several broad outcrop bands in the
northern and central parts of the area, appears to be associated with elevated radioactivity and with
moderate to high indoor radon levels. This area has moderate radon potential overall.
The Avalonian Terrane, along the eastern and southeastern borders of Connecticut (34,35,
fig. 1), is underlain by granite, granite gneiss, mafic gneiss, and amphibolite. Granitic rocks
known to generate elevated indoor radon levels include the Waterford and Branford Gneisses, and
the Hope Valley Alaskite Gneiss, which also has a high aeroradioactivity signature, as well as
locally-occurring graphitic schist and gneiss in the Plainfield Formation. The overall radioactivity
signature of the area is moderate to high. Soils of the Avalonian Terrane have low to high
permeability, with granitic rocks producing sandy, more permeable soils, and mafic and volcanic
rocks producing silty and sandy soils with slowly permeable, clayey substrata. The indoor radon
average for this terrane is 3.3 pCi/L. Overall, this area has high radon potential.
m-5 Reprinted from USGS Open-File Report 93-292-A
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MAINE
The rocks, surficial deposits, and geologic structures of Maine that are most likely to cause
high (>4 pCi/L) indoor radon concentrations include: two-mica granite, alkaline and calc-alkalic
granite, and granodiorite; pegmatites, faults and shear zones; and carbonaceous schist, slate, and
phyllite. Deposits and rocks likely to cause moderate (2-4 pCi/L) to high (>4 pCi/L) indoor radon
include soils developed on carbonate rocks, especially the interbedded slates and dolostones in
south-central and northeastern Maine; glacial gravels, especially outwash, kames, and eskers;
melange; granitic gneiss; high- to medium-grade metamorphic rocks, and contact metamorphosed
rocks in the vicinity of plutons. Rocks and deposits with moderate to variable radon potential
include felsic metavolcanic rocks, intermediate composition plutonic rocks, and glacial till. Rocks
likely to cause low indoor radon (< 2 pCi/L) include metamorphosed coarse-grained clastic
sedimentary rocks, mafic metavolcanic rocks, marine clays, and mafic plutonic rocks.
Most of Maine is underlain by Cambrian-Devonian stratified metamorphic rocks of igneous
or sedimentary origin that we have ranked from low to high in radon potential. Uranium
concentration generally increases with metamorphic grade and local uranium concentrations may be
present in fractures and faults. Areas in northern Maine underlain by coarse-grained clastic
metasedimentary rocks and tills derived from these rocks generally have low equivalent uranium
and have soils with low permeability. Many of the rocks in this area belong to the Seboomook *
Formation (area 2, fig. 1). In central and southern Maine, indoor radon is low to moderate in areas
underlain by coarse-grained clastic metasedimentary rocks. Formations such as the Vasselboro,
which consists of interbedded carbonate rocks and clastic metasedimentary rocks and tends to be
more calcareous in general, appears to have high indoor radon associated with it in southern
Penobscot County. Central Maine (area 5, fig. 1) is a highly variable area-radon potential varies
from moderate to locally high or low. Locally high areas may be associated with granites, kames,
eskers, carbonate rocks, graphitic or carbonaceous schist, phyllite, and slate. Locally low areas
may be associated with mafic plutonic rocks and clastic metasedimentary rocks. Indoor radon is
highly variable in this area and the type and character of the rocks are variable over short distances.
Soils and glacial deposits derived from interbedded carbonate metasedimentary rocks and
slates in the northeastern portion of the State (3, fig. 1) and in the south-central portion of the State
(5, fig. 1) are associated with moderate and high indoor radon. Equivalent uranium is variable
over these deposits but is higher than the dominantly clastic metasedimentary rocks. Soils, tills,
eskers, and kames derived from these rocks generally have moderate to locally high permeability.
The area underlain by these rock units in the northeastern part of Maine (area 3) has high radon
potential, whereas the rocks in the south-central part (area 5) are assigned a moderate geologic
radon potential.
Most of the carbonaceous or graphitic rock units in Maine have moderate to high equivalent
uranium. Some high indoor radon may be associated with carbonaceous rocks of the Penobscot
Formation in Knox County (area 10, fig. 1). Soils formed on carbonaceous and graphitic rocks in
Maine have low to moderate permeability. Areas underlain by these rock units have high geologic
radon potential.
Plutonic rocks of intermediate to mafic composition generally have low or variable radon
potential. Diorite and mafic intrusives of the New Hampshire series have low equivalent uranium
and comprise two northeast-trending belts along the southern coast and from southern Oxford
County to central Picataquis County. However, two-mica granites, calc-alkaline granites, and
alkalic plutonic rocks in Maine (in areas 4, 5, 9, fig. 1) have been ranked high in geologic radon
m-6 Reprinted from USGS Open-File Report 93-292-A
-------
potential. Uranium concentrations in these types of granites are commonly more than 3 ppm and
are as high as several hundred ppm in Maine. Two-mica granites are most abundant in the
southwestern part of the State and include the rocks of the Sebago Pluton. Calc-alkaline to alkaline
granites are more abundant in the southern and central part of the State, particularly in the area
northeast of Penobscot Bay and in the Katadhin pluton in central Maine (the part of area 4 in central
Maine). Indoor radon averages are high in the southwestern counties of Maine, which may be due
to the abundance of igneous plutons and high-grade metamorphic rocks in this area. Most of the
areas underlain by igneous plutonic rocks and associated glacial deposits have moderate to locally
high permeability.
Although there is no obvious anomalous radioactivity associated with major fault and shear
zones in Maine, evidence from other areas of the Appalachians suggests that shear zones can create
isolated occurrences of severe indoor radon, especially when they deform uranium-bearing rocks.
The radon potential of melange, most of which is found in the northwestern part of Maine (area 1
and a small part of area 5, fig. 1), is not well known, but gray to black phyllitic rocks and
deformed zones have the potential to produce at least moderate amounts of radon. We have
tentatively ranked these rocks as moderate or variable in radon potential.
The effect of glacial deposits is difficult to assess in Maine because most till is relatively
locally derived and is composed primarily of clasts of the surrounding bedrock. The areas of
coarse-grained glacial deposits in southwestern Maine and the kame and esker deposits scattered
throughout the State enhance the geologic radon potential due to their very high permeability; these
units have moderate to high radon potential. The coarser glacial deposits appear to be associated
with the igneous plutonic rocks and belts of calcareous and carbonate metasedimentary rocks.
Along the coast, areas of slowly permeable marine and glaciomarine clay (areas 7, 8,11, fig. 1)
probably reduce the radon potential and they are assigned a low geologic radon potential. Glacial
lake sediments with low permeability in Penobscot County (6, fig. 1) appear to be associated with
low indoor radon. Till with compact, slowly permeable substrata is dominant in much of central
and northern Maine and the rocks underlying these areas are metasedimentary and metavolcanic
rocks that are generally low in uranium.
MASSACHUSETTS
The metamorphic rocks of the Taconic Mountains and carbonate sedimentary and
metasedimentary rocks of the Vermont-Stockbridge Valley, in westernmost Massachusetts
(area 21, fig. 1), have been ranked moderate in geologic radon potential. Graphitic phyllites and
schist of the Walloomsac Formation have moderate to high radioactivity associated with them and
may produce locally elevated indoor radon levels. Elevated radon may also be associated with fault
and shear zones, especially in the Taconic Mountains.
The Berkshire Mountains (area 22, fig. 1) have been ranked moderate overall in radon
potential. Granitic to dioritic gneiss and schist have generally low equivalent uranium associated
with them. Shear zones, pegmatites, and local accumulations of monazite in biotite schist and
gneiss may be sources of locally high indoor radon levels. Soil permeability is low to moderate.
Metamorphic rocks of the Connecticut Valley Belt, flanking the Mesozoic basins of west-
central Massachusetts (27, 30, fig. 1), have been ranked moderate in radon potential.
Metasedimentary and metavolcanic gneisses and schists have generally low to moderate
radioactivity associated with them. Soils have generally moderate permeability. The Pauchaug and
Glastonbury granite gneisses, which form the cores of the Warwick and Glastonbury domes, as
ffl-7 Reprinted from USGS Open-File Report 93-292-A
-------
well as other locally-occurring granitic rocks in area 30 (fig. 1), may generate locally high indoor
radon levels. Locally high radon levels are likely to be associated with an area of anomalous
radioactivity at the south end of the Warwick dome and may be associated with faults and shears
throughout the area.
Mesozoic sedimentary and igneous rocks of the Connecticut Valley (28, fig. 1) have been
ranked moderate or variable in radon potential. Most of the sedimentary rocks have low radon
potential but locally high indoor radon levels may be associated with Jurassic-age black shales and
localized uranium deposits in fluvial sandstone and conglomerates. Geologic radon potential is
low to moderate in glacial lake-bottom sediments, and moderate to high in glaciofiuvial deposits
including outwash, lacustrine delta deposits, and alluvium.
Granitic plutons of the Merrimack Belt, central Massachusetts (32, fig. 1), have been
ranked high in radon potential. The metasedimentary rocks surrounding the plutons are
predominantly phyllites and carbonaceous slates and schists with moderate to high radon potential.
Mafic metamorphic rocks, which are less common in the Merrimack Belt, have generally low to
moderate radon potential. Faults and shear zones may produce locally high radon concentrations.
Granitic plutonic rocks and metamorphic rocks of the Nashoba terrane (36, fig. 1), the
northward extention of the Avalonian terrane (37, fig. 1), and granites of the Cape Ann and
Peabody plutons, in northeastern Massachusetts (42, fig. 1), are ranked high in radon potential.
They are associated with moderate to high radioactivity and the soils developed on these rocks have
moderate to high permeability. Relationships between radon and underlying bedrock in eastern
Massachusetts, particularly in the Merrimack zone and in these areas, are less distinct, probably
due to the influence of glacial deposits that are made up of a mixture of the rock types underlying
eastern Massachusetts and areas to the north. The glacial deposits generally have enhanced
permeability and may have enhanced radon emanation due to the redistribution of rock
components, mixing, and grain-size reduction effects of the glacial processes. Volcanic rocks and
soils of the Newbury basin (41, fig. 1) are ranked moderate in radon potential.
The Esmond-Dedham terrane, southeastern Massachusetts (44, 46, fig. 1), is ranked
moderate overall in geologic radon potential. This area includes a number of granite plutons and
fault zones that may generate high radon levels, as well as mafic metasedimentary and metavolcanic
rocks having low to moderate radon potential. Aeroradioactivity is generally low to moderate with
one anomaly associated with granite of the Rattlesnake Hill Pluton. Soils in this area have low to
moderate permeability.
Pennsylvanian sedimentary rocks of the Narragansett basin, southeastern Massachusetts
(45, fig. 1), are associated with low to moderate radioactivity and low to moderate soil
permeability, and have moderate geologic radon potential. The Norfolk basin is similar to the
Narragansett basin and also has moderate radon potential. Proterozoic to Pennsylvanian
sedimentary rocks of the Boston basin (43, fig. 1) have been ranked low in radon potential.
Information on soil characteristics and radioactivity is unavailable for the Boston basin but
radioactivity is assumed to be generally low based on the radioactivity of similar rocks elsewhere in
the State. Soil characteristics are highly variable in urban areas due to human disturbance, and thus
are considered to be variable for this assessment. Black shales and conglomerates in the Boston
basin may have locally high radioactivity and may cause locally elevated indoor radon levels.
Sediments of the Coastal Plain are found primarily on Nantucket Island and Martha's
Vineyard (47, fig. 1). Areas underlain by Cretaceous and Tertiary sediments have low radon
potential, but areas underlain by the Martha's Vineyard and Nantucket moraines have moderate to
locally high radon potential caused by their relatively higher permeability and better drainage
m-8 Reprinted from USGS Open-File Report 93-292-A
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characteristics compared to surrounding areas, and the crystalline rock source component of the
moraines. This is also true of the Buzzard's Bay and Sandwich moraines on Cape Cod. Areas
underlain by highly permeable glacial outwash may also generate locally elevated indoor radon
levels if the soils are not too wet to preclude soil-gas transport
NEW HAMPSHIRE
The Avalonian Composite Terrane, in southeastern New Hampshire (area 14, fig. 1), is
underlain by the Merrimack Group, Massabesic Gneiss, the Rye Formation and several bodies of
two-mica granites, alkalic plutonic rocks, and mafic plutonic rocks. Soils in this area have
generally low permeability that is locally moderate to high. The Merrimack Group has low to
moderate equivalent uranium, whereas other rocks have generally moderate to high equivalent
uranium, particularly the Massabesic Gneiss, two-mica granites, and the extensive fault zones.
The Merrimack Group and Rye Formation have overall moderate radon potential, with locally low
radon potential. The Massabesic Gneiss, the granite intrusives, and the fault zones have high
radon potential. Average indoor radon for the townships underlain by Avalonian rocks is
predominantly moderate to high. Overall, the Avalonian Composite Terrane has been ranked
moderate to high in radon potential.
About half of New Hampshire is underlain by Cambrian-Devonian stratified metamorphic
rocks of igneous or sedimentary origin of the Gander (area 13, fig. 1) and Boundary Mountains
(area 12) Terranes. These rocks have been ranked moderate in radon potential overall. The
metasedimentary and metavolcanic rocks have variable uranium content, with increasing uranium
as metamorphic grade increases, and contain local uranium concentrations in fractures and faults.
Graphitic slates, phyllites, and schists are may also be possible sources of high indoor radon.
Where indoor radon data are available, the stratified metamorphic rocks appear to be associated
with low to moderate indoor radon in the western portion of the State and with higher indoor radon
in the eastern portion of the State and in the vicinity of plutonic rocks. Intermediate to mafic
plutonic rocks generally have low or variable radon potential. The Lake Winnipesaukee Quartz
Diorite and the Kinsman Quartz Monzonite appear to have low equivalent uranium and low indoor
radon associated with them, and are ranked low in geologic radon potential.
Several of the Oliverian domes have distinct radiometric highs associated with them except
for the northernmost and largest of the Oliverian rocks in the northern Gander Terrane, which have
low radioactivity. Indoor radon in the townships underlying this area is variable from low to high.
The Oliverian rocks and intermediate composition plutonic rocks are ranked moderate or variable in
geologic radon potential.
Two mica granites, calc-alkaline granites, and alkalic plutonic rocks in New Hampshire
have been ranked high in radon potential. Uranium content of these granites is commonly more
than 3 ppm and ranges to several hundreds of ppm. Two-mica granites occur throughout the
central and eastern portions of New Hampshire. Calc-alkaline granites occur from east-central to
northwestern New Hampshire. The largest body of calc-alkaline granite underlies the White
Mountains and has very high radioactivity associated with it Indoor radon levels in several
townships in this area are high.
High radon concentrations in domestic water are associated with granites, pegmatites, and
faults in some parts of New Hampshire. The radon in these wells may be high enough to
contribute significantly to the radon content of the indoor air.
m-9 Reprinted from USGS Open-File Report 93-292-A
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RHODE ISLAND
The radon potential of Rhode Island appears to be influenced most by the composition of
the underlying bedrock and secondarily affected by glacial deposits. The greatest percentage of
homes with 4pCi/L or more of radon are concentrated in the southern part of the State over the
Scituate and Narragansett Pier Igneous Suites, and parts of the Esmond Igneous Suite (area 39,
fig. 1), as well as with two areas also noted for high uranium: the northwestern and southwestern
corners of the State, underlain by the Sterling Plutonic group (38,40, fig. 1), and in the East Bay
Area, which is underlain by the granites of Southeastern Rhode Island. Igneous intrusive rocks of
the Scituate Igneous Suite, rocks of the Hope Valley Group, granites of southeastern Rhode
Island, the Narragansett Pier Granite, and alkalic granites of the Cumberland area have significant
uranium concentrations and surface radioactivity. Many of the areas underlain by these rocks also
have locally derived tills, kames and glacial lake deposits that may contribute significantly to the
overall high radon potential. The lowest radon potential appears to be associated with the less-
metamorphosed sediments of the Rhode Island Formation, which is overlain by glacial outwash
deposits in the northern portion of the Narragansett Lowlands (45, fig. 1). Low to moderate radon
appears to be associated with stratified metamorphic rocks of the Blackstone Group, the Harmony
Group, the Plainfield Formation, parts of the Esmond Igneous Suite, and scattered stratified
metamorphic rocks in the Narragansett Lowlands. These areas are ranked moderate or variable in
geologic radon potential overall.
The effect of glacial deposits is complex because most of the materials making up the
glacial deposits are locally derived and primarily reflect a collection of the surrounding bedrock.
The majority of soils and glacial deposits are moderate to high in permeability and probably
enhance the geologic radon potential. In the southern half of the State, stratified glacial deposits
appear to have lower radioactivity than areas of till over the same bedrock. Stratified glacial
deposits are most common along valley floors and in the Narragansett Basin, and are thicker and
generally coarser than the till. The thickness of the stratified deposits may damp the radioactivity
of the bedrock or indicate an overall lower radioactivity for the glacial deposit Although the
coarser stratified glacial sediments have higher permeability than some of the tills, their radon
emanation coefficient tends not to be as high as for some tills. Tills commonly have higher radon
emanation because of the higher proportion of finer-grained sediments. This is also true of some
glacial lake deposits. Thick deposits of outwash sand and gravel blanket much of the northern
Narragansett Lowlands and appear to have both low radioactivity and low indoor radon associated
with them; this area is assigned a low geologic radon potential. The southern part of the
Narragansett Lowlands and East Bay Area, however, have a significantly higher percentage of
indoor radon readings exceeding 4 pCi/L. This may be due to the fact that the southern part of the
Narragansett Lowlands and East Bay Area are dominated by thin glacial till containing components
of uraniferous granite and phyllite; this area has a moderate or variable geologic radon potential.
Another example of the influence of glacial deposits may be seen in the area of the Narragansett
Pier Granite, where high percentages of homes have indoor radon levels greater than 4 pCi/L.
The types of glacial deposits in this area include kames, glacial lake deposits, and till, which are
known to have enhanced radon exhalation. These glacial deposits may also have significant source
components in the adjacent Scituate Igneous Suite and Sterling Plutonic Group as well as the
Narragansett Pier granite, all of which have some elevated uranium concentrations.
ffl-10 Reprinted from USGS Open-File Report 93-292-A
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VERMONT
The geologic radon potential of the Champlain Lowlands (area 18, fig. 1) is low, with
areas of locally moderate to high radon potential possible. The Vermont Valley (19, fig. 1) has
generally moderate geologic radon potential. Clay-rich soils with low permeability dominate the
lowlands and include glacial lake and marine clays, which probably reduce the radon potential
significantly. Radioactivity is generally low, with a few scattered high and moderate areas that
appear to be associated with the Clarendon Springs Formation and, possibly, with black shales and
slates in surrounding rock units. Indoor radon levels in the counties underlain by the Champlain
Lowlands are generally less than 4 pCi/L except in Addison County, where out of 26 readings, six
were greater than 4 pCi/L and of these, two were greater than 20 pCi/L.
The Green Mountains (17, fig. 1) have been rated moderate in radon potential; however,
the radon potential is actually highly variable. Areas with locally high radon potential are those
underlain by metamorphic rocks of Proterozoic age, including quartzite; graphite- and pyrite-
bearing schists and slates; migmatitic schist and gneiss; biotite-rich zones in mica schist; and schist
and gneiss with high concentrations of the minerals monazite, allanite, and zircon; the Cheshire
Quartzite; and local deposits of uranium in veins and fault zones. Mafic metamorphic rocks such
as amphibolite, hornblende gneiss, gabbro, and serpentinite, have low geologic radon potential.
Radioactivity is variable—low in the southern portion but containing local high radioactivity areas,
moderate to high radioactivity in the central portion, and low in the north.
The Taconic Mountains (20, fig. 1) have moderate geologic radon potential. Radioactivity
is generally moderate to high, and several rock types appear to have elevated levels of uranium,
especially the carbonaceous sedimentary rocks of the Pawlet Formation. Elevated concentrations
of uranium in the black to gray phyllites and slates are probably the principal radon sources in this
area.
The Vermont Piedmont (16, fig. 1) has moderate but variable geologic radon potential.
Much of the area is underlain by mafic rocks with low radon potential. Granites, granitic gneiss
and schist, and carbonaceous or graphitic slate and phyllite have the potential to generate moderate
to high indoor radon levels.
The Northeastern Highlands (15, fig. 1) have moderate radon potential. Plutonic igneous
rocks are abundant in this area and in the northern half of the Vermont Piedmont, but only a few of
the plutons have distinct radiometric anomalies associated with them. Indoor radon for counties
underlain by these rocks is moderate with the exception of Caledonia County, in which 11 of the
51 indoor radon measurements in the State/EPA Residential Radon Survey were greater than
4 pCi/L.
m-11 Reprinted from USGS Open-File Report 93-292-A
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PRELIMINARY GEOLOGIC RADON POTENTIAL ASSESSMENT OF MASSACHUSETTS
by R. Randall Schumann and Linda C.S. Gundersen
US. Geological Survey
INTRODUCTION
This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
deposits of Massachusetts. The scale of this assessment is such that it is inappropriate
for use in identifying the radon potential of small areas such as towns,
neighborhoods, individual building sites, housing tracts, or individual homes.
Any localized assessment of radon potential must be supplemented with additional data and
information from the locality. Within any area of a given radon potential ranking, there are likely
to be areas with higher or lower radon levels than characterized for the area as a whole. Indoor
radon levels, both high and low, can be quite localized, and there is no substitute for testing
individual homes. Elevated levels of indoor radon have been found in every State, and EPA
recommends that all homes be tested. For more information on radon, the reader is urged to
consult the local or State radon program or EPA regional office. More detailed information on state
or local geology may be obtained from the state geological survey. Addresses and phone numbers
for these agencies are listed in chapter 1 of this booklet
PHYSIOGRAPHIC AND GEOGRAPHIC SETTING
The physiography of Massachusetts (fig. 1) is a reflection of the underlying bedrock
geology (fig. 2) and subsequent modification by Pleistocene glaciation and postglacial erosional
processes. The State's elevation ranges from sea level to 3,491 feet at Mount Greylock, in the
Taconic Mountains in northwestern Massachusetts. Massachusetts is divided into six major
physiographic regions. From west to east they are the Taconic Mountains, Berkshire Valley,
Western New England Upland, Connecticut Valley Lowland, Eastern New England Upland, and
the Coastal Lowlands (fig. 1).
The Taconic Mountains are an area of low mountains and hills along the Massachusetts-
New York border which extend northward, increasing in height, into Vermont. In Massachusetts,
several peaks are greater than 2500 ft in altitude (Denny, 1982). The Taconic Mountains roughly
coincide with the Taconic allochthon, a series of schists, phyllites, and metagraywackes that
produce steep-sided mountains bordered by a relatively broad valley called the Berkshire Valley
(fig. 1). The Berkshire Valley section, consisting of the Stockbridge Valley and several smaller
valleys, is a group of roughly linear, flat-floored valleys underlain largely by carbonate rocks that
were eroded by the Hoosic and Housatonic Rivers. The Western New England Upland is an area
of rolling hills and low mountains ranging from about 1300 to 2500 ft in altitude, known as the
Berkshire Mountains and Hoosac Mountains, and underlain primarily by Proterozoic gneisses and
quartzite, and Paleozoic schist and quartzite.
The Western New England Upland is separated from the Eastern New England Upland by
the Connecticut Valley Lowland, a broad, relatively flat-floored valley carved by the Connecticut
River and by glacial erosion. The Connecticut Valley ranges from about 5 to 15 miles wide and the
valley floor has a maximum altitude of about 300 ft in its northern part Ridges of volcanic rock
that border the west side of the valley locally rise to elevations of more than 500 ft The
Connecticut Valley is underlain by Triassic and Jurassic sedimentary and volcanic rocks. To the
east of the Connecticut Valley Lowland lies the Eastern New England Upland, an area of low
IV-1 Reprinted from USGS Open-FUe Report 93-292-A
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EXPLANATION FOR GENERALIZED BEDROCK GEOLOGIC MAP OF MASSACHUSETTS
TACONIC-BERKSfflRE ZONE (ORDOVICIAN AND OLDER ROCKS)
Walloomsac Formation (Middle Ordovician)—Graphitic quartz phyllite and schist containing minor lenses of
limestone; quartzite and calcareous quartzite previously mapped as Bellowspipe Quartzite; graphitic and calcitic
marble and schistose marble with interbedded black phyllite; crystalline limestone lenses near base of the
Walloomsac locally yielding fragments of pelmatozoa, bryozoa and cup coral
Stockbridge Formation (Lower Ordovician to Lower Cambrian)—Limestone and calcite marble and beds
of beige dolostone; local layers of quartzose limestone near base; layered calcite marble; quartzose calcite and
dolomite marble, locally containing interbeds of phyllite and quartzite; quartzite; dolostone with quartz and
tremolite in higher-grade areas.
Cheshire Quartzite (Lower Cambrian)—White, massive vitreous quartzite
Dalton Formation (Lower Cambrian and Proterozoic Z>—Muscovite-microcline quartzite and feldspathic
quartzite with tourmaline, locally includes thin beds of: carbonaceous quartz schist; quartzite; feldspathic,
biotite-muscovite gneiss and granofels; muscovite-quartz schist and interlayered feldspathic quartzite and quartz
conglomerate with minor beds of rusty schist; quartz and gneiss cobble and pebble conglomerate, and muscovite
quartz schist
Hoosac Formation (Lower Cambrian and Proterozoic Z)—Muscovite-biotite schist or gneiss, with
interlayered garnet-biotite schist near base, that interfingers with Dalton Formation; conglomerate
Canaan Mountain Formation (Lower Ordovician and Proterozoic Z)—Rusty-weathering, coarse garnet
schist and feldspathic schist
Biotite-plagioclase-quartzite, and calc-silicate gneiss (Proterozoic Y)
Calc-silicate granofels and gneiss (Proterozoic Y)—Including calcitic or dolomitic marble, coarse
hornblende-plagioclase-diopside and diopside rock, locally containing beds of schist
Lee Gneiss (Proterozoic Y)—Mafic gneiss and granofels
Well-layered hornblende-biotite gneiss (Proterozoic Y)
Pinkish-gray, fine-grained, well-laminated felsic biotite-microcline-plagioclase-quartz gneiss (Proterozoic
Y)—Probably metamorphosed rhyolite
Black and white, well-layered hornblende-biotite-plagioclase gneiss and amphibolite (Proterozoic Y)—
Contains irregular pods of diopside or cummingtonite-talc rock or amphibole calc-silicate, epidote-layered
quartz-plagioclase gneiss near Hinsdale
Massive amphibolite of uncertain age (Proterozoic Y?)—Near South Sandisfield
Washington Gneiss (Proterozoic Y)—Rusty-weathering, muscovite-biotite-sillimanite and/or kyanite-garnet
schist; conglomerate, interlayered metadacite; well-layered, rusty-tan weathering, quartz granofels containing
layers of rusty, sulfidic, calc-silicate rocks; coarse- to medium-grained mafic gneiss and metabasalt; rusty-
weathering diopside and sulfide-rich calcite marble and calc-silicate rock
Intrusive rocks:
White, magnetite-bearing alaskite and trondhjemite (Ordovician)—Associated with blastomylonite.
White to gray and black-spotted muscovite-biotite granite and granodiorite (Ordovician)—Intruded near
or along thrust faults.
Serpentinized peridotite stocks (Ordovician to Proterozoic Z) and Biotite-hornblende mafic dikes
(Proterozoic Z) Intrudes Washington Gneiss and Proterozoic Y granitiod gneiss
Tyringham Gneiss (Proterozoic Y)—Gray biotite granodioritic to quartz monzonitie gneiss, coarsely
porphyritic, locally having fine-grained aplitic border.
Stamford Granite Gneiss (Proterozoic Y)—White to gray biotite granite gneiss containing blue quartz
Granitoid Gneiss (Proterozoic Y)—Biotite granodioritic and granitic gneiss with large schlieren of biotite,
locally contains garnet and muscovite
Hoosac Formation (Lower Cambrian and Proterozoic Z)—Phyllite; interbeds of schist and minor quartzite;
rusty gray schist and gneiss, locally conglomeratic; greenish-gray schist with garnets; rusty-weathering kyanite
schist with distinctive quartz lenses and minor thin beds of calc-silicate rocks; green, tan, and gray schist;
granofels; amphibolite
Sherman Marble (Proterozoic Y)—White, coarse-grained graphite dolomite-calcite marble at Sherman
Reservoir at the Sate line
Intrusive rocks:
Diorite at Goff Ledges (Ordovician)—Coarse-grained to pegmatitic, homblende-plagioclase diorite, minor
hornblende pyroxenite
White to gray and black-spotted muscovite-biotite granite and granodiorite (Ordovician)—Intruded near
or along thrust faults, intrudes Hoosac Fm. and Proterozoic gneisses
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GEOLOGIC MAP OF MASSACHUSETTS EXPLANATION
Tectonic breccia (Ordovician)—Zones of mixed inclusions of Stockbridge Formation, Walloomsac
Formation, and phyllites of the Taconic allochthon, or complexly mixed phyllites of Walloomsac Formation and
Taconic allochthon
Nassau Formation (Lower Cambrian and Proterozoic Z)—Siliceous phyllite, quartzite, metasiltstone and
subgraywacke (includes Bomoseen Graywacke Member and Zion Hill Quartzite Member); chloritoid-rich
phyllite; albitic phyllite; chloritoid-chlorite phyllite (Mettawee Member); plagioclase-rich, blue quartz pebble
metagraywacke and minor gneiss-cobble conglomerate (Rensselaer Graywacke Member); metabasalt and
basaltic tuff
Greylock Schist (Lower Cambrian and Proterozoic Z)—Phyllite with minor beds of green quartzite,
resembles Hoosac and Nassau Formations; phyllite and interbedded metagraywacke, dolostone and
conglomerate.
Everett Formation (Lower Cambrian and Proterozoic Z)—Phyllite, metagraywacke and quartzite;
predominantly chloritoid-rich schist in Lenox Mountain
CONNECTICUT VALLEY BELT (SILURIAN AND DEVONIAN ROCKS)
Belchertown Complex (Devonian)—Quartz monzodiorite, quartz monzodiorite gneiss, hornblende peridotite
homblendite, intrusive breccia, mafic and ultramafic fragments in quartz diorite; biotite tonalite of marginal
stocks; inclusions of amphibolite, granofels and dacite porphyry.
Prescott Complex: Cooleyville Granitic Gneiss (Devonian)—Biotite tonalite to granite in composition;
contains inclusions of hornblende gabbro (formerly Prescott Diorite of Emerson, 1917) and intrusions of
Littleton Formaion
Putney Volcanics (Devonian)—Greenish-gray plagirolase-quartz-muscovite phyllite and granofels.
Gile Mountain formation (Devonian)—Gray, slightly rusty phyllite and schist interbedded with quartzite
local calcareous granofels or quartzose marble, pods and stringers of vein quartz, amphibolite, and hornblende
schist.
Waits River Formation (Devonian)—Interbedded gray, rusty-weathering, schist and calcareous granofels or
quartzose marble, pods and stringers of vein quartz; amphibolite or hornblende schist with calcareous granofels
Goshen Formation (Devonian)—Quartzite or quartz schist grading upward into gray, carbonaceous schist-
local calcareous granofels; micaceous quartzite and schist. Calc-silicate granofels; carbonaceous schist and
quartz schist.
Erving Formation (Devonian)—Biotite-plagioclase granofels, minor mica schist and calc-silicate granofels
layers of epidote amphibolite; mixed mica schist and amphibolite.
Littleton Formation (Devonian)—Black to gray aluminous mica schist, quartzose schist, and aluminous
phyllite; locally intruded by hornblende-olivine gabbro of uncertain age.
Russell Mountain Formation (Silurian)—Quartzite, calc-silicate granofels, and calc-silicate marble
Fitch Formation (Silurian)—Calc-silicate granofels, biotite granofels, sulfidic schist and marble.
Clough Quartzite (Silurian)—Quartz conglomerate, quartzite, mica schist and calc-silicate rocks
Intrusive rocks:
Williamsburg Granodiorite (Devonian)—Biotite-muscovite granodiorite.
Feldspar-quartz-muscovite pegmatite (Devonian)—Partly associated with the Williamsburg Granodiorite
Hawley Formation (Middle Ordovician)—Interbedded amphibolite, greenstone, feldspathic schist and
granofels. Sparse coticule (Emerson, 1971, p. 43); black, rusty-weathering schist and thin dark quartzite-
interlayers of amphibolite; light-colored plagioclase gneiss; medium-gray mafic schist containing megacrysts of
plagioclase and angular fragments of feldspar granofels, epidote-plagioclase granofels; dark-gray amphibolite-
liognt-colored plagioclase granofels; gametiferous mafic gneiss
Cobble Mountain Formation (Middle Ordovician)—Rusty-weathering feldspathic gneiss and mica schist-
nonrusty-weathenng silvery-gray schist and aluminous schist; serpentinite and/or talc rock; thin beds of gneiss
arnpnibolite, politic schist and granofels; feldspar gneiss, coticule and cummingtonite schist; calc-silicate rocfa
Moretown Formation (Middle Ordovician or older)—Light-colored, pinstriped granofels and schist; nubble
garnet schist and fine-grained amphibolite; rusty, carbonaceous quartz-muscovite schist; green to dark-creen
greenstone or amphibolite
Rowe Schist (Lower Ordovician and Cambrian)—Light-colored schist with quartz, kyanite and staurolite
typical at higher grades; gray to black, slightly rusty, moderately carbonaceous schist; minor quartzite- well-
layered and foliated amphibolite, includes its type Chester Amphibolite Member at Chester, Massachusetts
Intrusive rocks:
Middlefield Granite (Devonian)—Moderately foliated granite
Gneiss at Hallockville Pond (Ordovician)—Light-gray foliated quartz biotite gneiss
Serpentinite and/or talc rock (age uncertain)—Interpreted as tectonic slivers
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GEOLOGIC MAP OF MASSACHUSETTS EXPLANATION
Collinsville Formation (Middle Ordovician or older)—Brown to rusty-brown schist containing coticule and
locally massive amphibolite at base; amphibolite and plagioclase gneiss; felsic gneiss; local calc-silicate beds;
quartzite; garnetiferous biotite gneiss; rusty-weathering, massive granofels; some rusty-stained gneiss
Monson Gneiss (Ordovician, Cambrian;, or Proterozoic Z)—Layered to massive biotite-plagioclase gneiss,
amphibolite, microcline augen gneiss; lenses of peridotite, variously altered
Fourmile Gneiss (Ordovician, Cambrian, or Proterozoic Z)—Layered to massive biotite-feldspar gneiss and
amphibolite; ultramafic hornblendite; muscovite quartzite
Poplar Mountain Gneiss (Proterozoic Z) (Probably correlates with Mount Mineral Formation but is more
feldspathic)—Dark biotite gneiss containing white microcline megacrysts and beds of quartzite; basal quartzite,
commonly feldspathic
Mount Mineral Formation (Proterozoic Z) (Probably correlates with Poplar Mountain Gneiss but is more
aluminous)—Aluminous schist, amphibolite, and quartzite, undifferentiated; locally rich in garnet and kyanite,
and with relict sillimanite and orthoclase
Dry Hill Gneiss (Proterozoic Z)—Pink microcline-homblende gneiss, biotite-tourmaline schist, minor
quartzite; white to buff quartzite and feldspathic quartzite, commonly with biotite and/or actinolite (Pelham
Quartzite Member)
Intrusive rocks:
Glastonbury Gneiss (Ordovician)—Massive granitic gneiss in core of Glastonbury dome and in adjacent areas
Pauchaug Gneiss (Ordovician)—Massive granitic gneiss in core of Warwick dome
MESOZOIC BASINS (JURASSIC AND TRIASSIC ROCKS)
Portland Formation (Lower Jurassic)—Red arkose and siltstone, gray sandstone and siltstone, black shale,
red conglomerate and arkose.
Granby Basaltic Tuff (Lower Jurassic)—Dark tuff, with sediment fragments.
Hampden Basalt (Lower Jurassic)—Thin quartz tholeiite, locally associated with Granby Basaltic Tuff.
East Berlin Formation (Lower Jurassic)—Red arkosic sandstone and siltstone, gray sandstoneand mudstone,
black shale, red conglomerate and arkosic sandstone.
Holyoke Basalt (Lower Jurassic)—Thick quartz tholeiite containing local gabbroic segregations.
Shuttle Meadow Formation (Lower Jurassic)—Red arkosic sandstone and siltstone, gray sandstoneand
mudstone, black shale, red conglomerate and arkosic sandstone.
Hitchcock Volcanics (Lower Jurassic)—Basaltic breccia containing abundant fragments of New Haven
Arkose, locally intrusive into arkose near base.
New Haven Arkose (Lower Jurassic and Upper Triassic)—Red, pink, and gray coarse-grained, locally
conglomeratic arkose interbedded with brick-red shaley siltstone and fine-grained arkosic sandstone; continuous
with and lithically similar to the Sugarloaf Formation near Northampton.
Intrusive and Catactastic Rocks—Silicified fault-breccia or strongly silicified metamorphic rocks. Mylonite
along Connecticut Valley border fault. Diabase dikes and sills.
Mount Toby Formation (Lower Jurassic)—Red arkosic sandstone, gray sandstone and siltstone, black shale,
red conglomerate and arkosic sandstone, coarsens eastward; breccia of granitic gneiss at Taylor Hill and breccia
of amphibolite at Whitmore Ferry.
Turner Fails Sandstone (Lower Jurassic)—Red arkosic sandstone, gray sandstone and siltstone, black shale,
red conglomerate and arkosic sandstone.
Deerfield Basalt (Lower Jurassic)—Quartz tholeiite.
Sugarloaf Formation (Lower Jurassic and Upper Triassic)—Red arkose, gray sandstone and siltstone, black
shale, red conglomerate and arkosic sandstone, coarsens eastward; continuous with and lithically similar to the
New Haven Arkose near Northampton.
Fine-grained hornblende diorite (age uncertain)—In Connecticut River bed, near French King Rock
MERRIMACK BELT (SILURIAN, DEVONIAN, AND PENNSYLVANIA^ ROCKS)
Massive to weakly foliated, pink and gray, fine- to medium-grained biotite granite (Pennsylvanian)—
commonly contains pink magnetite-bearing pegmatite
Massabesic Gneiss Complex—Biotite-feldspar paragneiss of Proterozoic Z age intruded by potassium-
feldspar-rich gneiss of Ordovician age.
Biotite-muscovite granite (Devonian)
Hardwick Tonalite (Devonian)—Gray biotite tonalite to granodiorite gneiss; intruded by porphyritic
microcline-biotite granite gneiss in sills
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GEOLOGIC MAP OF MASSACHUSETTS EXPLANATION
Fitchburg Complex (Devonian)—Gray to white muscovite-biotite granite; commonly contains white
pegmatite; may include granite of late Paleozoic age; gray biotite-muscovite granite to granodiorite gneiss;
common inclusions of Littleton Formation; gray, biotite granodiorite to tonalite gneiss; contains zones of
foliated biotite-muscovite granite gneiss and inclusions of mica schist and feldspathic granulite, inclusions of
massive coarse-grained biotite-hornblende tonalite
Biotite-hornblende diorite, quartz-bearing diorite, metadiorite and norite (Devonian)
Coys Hill Porphyritic Granite Gneiss (Devonian)—Microcline granite gneiss, commonly containing garnet,
sillimanite, and muscovite; contains hornblende gneiss inclusions.
Chelmsford Granite (Devonian)—Gray muscovite-biotite granite.
Diorite and tonalite (Devonian and Silurian)—Includes Dracut Diorite, tonalite near the Ayer Granite, and
equivalents of the Exeter Diorite of New Hampshire
Ayer Granite (Lower Silurian and Upper Ordovician?)—Biotite granite to tonalite, locally gneissic, locally
with muscovite, may include rocks older than Silurian.
Newburyport complex (Silurian and Ordovician)—Gray granite, tonalite, and granodiorite
Erring Formation (Lower Devonian)—Biotite-plagioclase granofels, minor mica schist and calc-silicate
granofels, layers of epidote amphibolite; mica schist and amphibolite
Littleton Formation (Lower Devonian)—Black to gray aluminous mica schist, quartzose schist, aluminous
phyllite; biotite gneiss, quartz-feldspar-garnet gneiss, and calcitic marble
Fitch Formation (Upper Silurian)—Sulfidic calc-silicate and minor sulfidic schist
Partridge Formation (Middle Ordovician) (includes Brimfield Schist of Emerson, 1917)—Sulfidic mica
schist, amphibolite, calc-silicate rock; mafic and felsic gneisses and biotite gneiss of volcanic derivation; minor
amphibplite and sulfidic schist; sillimanite-feldspar augen gneiss; lenses of ultramafic rock; layered felsic gneiss
and schist
Ammonoosuc Volcanics (Middle Ordovician)—Amphibolite, felsic gneiss, garnet-amphibole quartzite, and
marble; ultramafic rock; basal quartzite and conglomerate
Intrusive rocks:
Granodiorite (Devonian)
Biotite-muscovite granite (Devonian)
Includes intrusive rocks of uncertain age: Biotite granitic gneiss, Granodiorite, Quartz diorite, Granite,
Hornblende-plagioclase gneiss, Biotite granitic gneiss—Mainly small lenses, Hornblende-olivine gabbro—
Intrudes the Littleton Formation, Biotite-garnet-feldspar gneiss of Ragged Hill
Coal Mine Brook Formation (Middle Pennsylvanian)—Fossiliferous, carbonaceous slate and garnet phyllite
with a lens of meta-anthracite; conglomerate and arkose
Harvard Conglomerate (Pennsylvanian)—Conglomerate and chloritoid-hematite phyllite
Worcester Formation (Lower Devonian and Silurian)—Carbonaceous slate and phyllite with minor
metagraywacke
Paxton Formation (Silurian)—Biotite and calc-silicate granofels, sulfidic schist, amphibolite, cordierite schist,
and sillimanite quartzite; rusty-weathering sulfidic quartzite and schist, calc-silicate granofels; Bigelow Brook '
Member—Biotite granofels, sulfidic schist, and calc-silicate granofels; Southbridge Member—Biotite and
calc-silicate granofels
Oakdale Formation (Silurian)—Metamorphosed, pelitic to calcareous siltstone and muscovite schist.
Berwick Formation (Silurian)—Metamorphosed calcareous sandstone, siltstone, and mica schist.
Eliot Formation (Silurian)—Phyllite and calcareous phyllite
Tower Hill Quartzite (Silurian)—Quartzite and phyllite
Vaughn Hills Quartzite (Silurian or Ordovician)—Quartzite, phyllite, conglomerate, and chlorite schist
Reubens Hill Formation (Silurian or Ordovician)—Amphibolite, hornblende-chlorite schist, and feldspathic
schist. Includes metamorphosed diorite
Boylston Schist (Silurian or Ordovician)—Carbonaceous phyllite and schist, locally sulfidic; quartzite- calc-
silicate beds
Intrusive rocks:
Muscovite-biotite granite (Devonian)—At Millstone Hill
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GEOLOGIC MAP OF MASSACHUSETTS EXPLANATION
ESMOND-DEDHAM ZONE (TERTIARY AND OLDER ROCKS)
Cretaceous and Tertiary sediments—Clay, silt, sand, and gravel, mostly of non-marine and nearshore marine
origin; contains Tertiary fossils
Red arkosic conglomerate, sandstone, and siltstone (Upper Triassic)—In Essex County
Lynn Volcanic Complex (Lower Devonian, Silurian, or Proterozoic Z)—Rhyolite, agglomerate, and tuff
Green Lodge Formation of Rhodes and Graves (1931) (Upper Cambrian?)—Quartzite and slate
Westboro Formation (Proterozoic Z)—Quartzite, schist, calc-silicate quaitzite, and amphibolite. Consists of
quartzite and argillite in Saugus and Lyunnfield areas
Metamorphosed mafic to felsic flow, and volcaniclastic and hypabyssal intrusive rocks (Proterozoic Z)—
Includes some diorite and gabbro north and northwest of Boston
Intrusive rocks:
Nahant Gabbro and gabbro at Salem Neck (Ordovician)—Labradorite-pyroxene gabbro, hornblende gabbro
and hornblende diorite
Topsfield Granodiorite (Proterozoic Z)—Grayish, porphyritic granodiorite containing blue quartz; usually
cataclastically foliated and altered
Diorite at Rowley (Proterozoic Z)—Dark green-gray, medium-grained hornblende diorite
Diorite and gabbro (Proterozoic Z)—Complex of diorite and gabbro, subordinate metavolcanic rocks and
intrusive granite and granodiorite
Serpentinite (age uncertain)
Dighton Conglomerate (Upper Pennsylvanian)—Coarse conglomerate having sandy matrix; minor sandstone
Rhode Island Formation (Upper and Middle Pennsylvanian)—Sandstone, graywacke, shale, and
conglomerate; minor beds of meta-anthracite. Fossil plants
Wamsutta Formation (Middle and Lower Pennsylvanian)—Red to pink, well-sorted conglomerate,
graywacke, sandstone, and shale; fossil plants; rhyolite and mafic volcanic rocks
Pondville Conglomerate (Lower Pennsylvanian)—Quartz conglomerate having abundant sandy matrix;
boulder conglomerate, arkose; fossil plants
Hoppin Formation (Middle and Lower Cambrian)—Quartzite, argillite, and minor limestone
Peabody Granite (Middle Devonian)—Alkalic granite containing ferro-homblende
Newbury Volcanic Complex (Lower Devonian and Upper Silurian)—Micrographic rhyolite; undivided
sedimentary and volcanic rocks; calcareous mudstone, red mudstone, and siliceous siltstone; porphyritic
andesite, includes tuffaceous mudstone beds; basalt, andesite, rhyolite, and tuff
Orange-pink, rusty-weathering, medium- to coarse-grained biotite granite to granodiorite (Silurian)—
Locally porphyritic
Sharpners Pond Diorite (Silurian)—Non-foliated, medium-grained equigranular biotite-hornblende tonalite
and diorite
Braintree Argillite and Weymouth Formation (Middle and Lower Cambrian)—Argillite, some with rare
limestone
Intrusive rocks:
Wenham Monzonite (Middle Devonian)—Monzonite containing ferro-hornblende
Cherry Hill Granite (Devonian)—Alaskitic granite containing ferro-hornblende
Blue Hill Granite Porphyry (Lower Silurian and Upper Ordovician)—Microperthite-quartz porphyry
Cape Ann Complex (Lower Silurian or Upper Ordovician)—Alkalic granite to quartz syenite containing
ferro-hornblende; Squam Granite—Fine- to medium-grained monzodiorite; Beverly Syenite—Quartz-poor
facies
Quincy Granite (Lower Silurian or Upper Ordovician)—Alkalic granite
Bellingham Conglomerate (Pennsylvanian, Cambrian or Proterozoic Z)—Red and gray metamorphosed
conglomerate, sandstone, graywacke, and shale
Cambridge Argillite (Proterozoic Z to earliest Paleozoic)—Gray argillite and minor quartzite; rare sandstone
and conglomerate
Roxbury Conglomerate (Proterozoic Z to earliest Paleozoic)—Conglomerate, sandstone, siltstone, argillite,
and melaphyre. Consists of Brookline, Dorchester, and Squantum Members
Mattapan Volcanic Complex (Proterozoic Z or younger)—Rhyolite, melaphyre, agglomerate, and tuff
-------
GEOLOGIC MAP OF MASSACHUSETTS EXPLANATION
Andover Granite (Silurian or Ordovician)—Gray, foliated, muscovite-biotite granite; pegmatite masses
common. Includes Acton Granite (Silurian or Ordovician)
Tadmuck Brook Schist (Silurian?, Ordovician, or Proterozoic Z)—Andalusite phyllite and sillimanite
schist, partly sulfidic; local quartzite in upper part
Tatnic Hill Formation (Ordovician or Proterozoic Z)—Sulfidic sillimanite schist, sillimanite schist and
gneiss, biotite gneiss; minor amphibolite, calc-silicate gneiss and marble; gray mica schist (Yantic Member);
calc-silicate gneiss and marble (Fly Pond Member)
Nashoba Formation (Ordovician or Proterozoic Z)—Sillimanite schist and gneiss, partly sulfidic,
amphibolite, biotite gneiss, calc-silicate gneiss
Fish Brook Gneiss (Ordovician or Proterozoic Z)—Light-gray, biotite-plagioclase quartz gneiss
Shawsheen Gneiss (Ordovician or Proterozoic Z)—Sillimanite gneiss, sulfidic at base; minor amphibolite
Quinebaug Formation (Ordovician, Cambrian, or Proterozoic Z)—Amphibolite, biotite and hornblende
gneiss, felsic gneiss, and calc-silicate gneiss
Marlboro Formation (Ordovician, Cambrian, or Proterozoic Z)—Thinly layered amphibolite, biotite schist
and gneiss, minor calc-silicate granofels and felsic granofels; homogeneous light-gray feldspathic gneiss
Intrusive rocks:
Straw Hollow Diorite and Assabet Quartz Diorite, unduTerentiated (Silurian)—Gray, medium-grained,
slightly-foliated biotite-homblende diorite and quartz diorite
Granodiorite of the Indian Head pluton (age uncertain)—Biotite granodiorite & homblende-biotite tonalite
Light-gray muscovite granite (age uncertain)
Plainfield Formation (Proterozoic Z)—Quartzite, pelitic schist, minor calc-silicate rock and amphibolite
Blackstone Group (Proterozoic Z)—-Quartzite, schist, phyllite, marble, and metavolcanic rocks
Metamorphosed felsic metavolcanic rocks (Proterozoic Z)
Intrusive rocks:
Milford Granite (Proterozoic Z)—Light-colored biotite granite, locally gneissic; granodiorite, with clots of
mafic minerals, locally gneissic (mafic phase)
Biotite granite (Proterozoic Z)—Light-colored biotite granite, locally foliated. Mafic minerals less prominent
than in Milford Granite but granular quartz common. Includes mafic-poor granite similar to the Hope Valley
Alaskite Gneiss
Hope Valley Alaskite Gneiss (Proterozoic Z)—Mafic-poor gneissic granite, locally muscovitic. Gradational
with Scituate Granite Gneiss
Scituate Granite Gneiss (Proterozoic Z)—Gneissic granite with biotite in small clots. Equivalent to part of
former Northbridge Granite Gneiss (usage now abandoned). Gradational with Hope Valley Alaskite Gneiss
Ponaganset Gneiss (Proterozoic Z)—Gneissic biotite granite containing microcline and biotite. Equivalent to
part of former Northbridge Granite Gneiss (usage now abandoned)
Gabbro (Proterozoic Z)—Hornblende gabbro and hornblende-pyroxene gabbro metamorphosed in part to
hornblende gneiss and amphibolite
Felsic and mafic volcanic rocks (Proterozoic Z)—Southwest of Boston Basin
Gneiss and schist near New Bedford (Proterozoic Z)—Hornblende and biotite schist and gneiss, amphibolite
Biotite gneiss near New Bedford (Proterozoic Z)—Layered feldspathic gneiss
Intrusive rocks:
Granite of Rattlesnake Hill pluton (Devonian)—Coarse-grained biotite granite and fine-grained riebeckite
granite
Alkalic granite in Franklin (Devonian to Ordovician)
Alaskite (Proterozoic Z)—Light-gray, pinkish-gray to tan, mafic-poor, muscovite gneissic granite
Dedham Granite (Proterozoic Z)—Light grayish, equigranular to slightly porphyritic, variably altered, granite
south and west of Boston. Includes dioritic rock near Scituate and Cohasset and Barefoot Hills Quartz
Monzonite of Lyons (1969) and Lyons and Wolfe (1971). Gray granite to granodiorite, more mafic than the
main body of Dedham Granite, crops out north of Boston
Westwood Granite (Proterozoic Z)—Light-grayish, fine- to medium-grained granite
Fine-grained granite and granite porphyry (age uncertain)
Granite of the Fall River pluton (Proterozoic Z)—Light-gray, medium-grained, biotite granite, in part mafic-
poor. Gneissic in New Bedford area. Includes Bulgarmarsh Granite (Proterozoic Z)
Porphyritic granite (Proterozoic Z)—Gray, seriate to porphyritic biotite granite containing biotite, epidote,
andsphene. Mafic inclusions common. Gneissic in New Bedford area
Granite, gneiss, and schist, undivided (Proterozoic Z)—Plutonic and metamorphic rocks of probable
Proterozoic Z age. May include plutonic and volcanic rocks of Paleozoic or younger age
Diorite (Proterozoic Z)—Medium-grained hornblende diorite, metamorphosed in part
Sharon Syenite (Proterozoic Z)—Gray to dark-gray syenite, mixed with ferro-gabbro
-------
mountains and hills underlain primarily by Paleozoic gneiss, schist, and phyllites of sedimentary
origin that are intruded by Paleozoic plutonic (granitic) rocks. Relief on the plutonic rocks is
generally less than 1000 ft (Denny, 1982).
The Coastal Lowlands occupy approximately the eastern one-third of Massachusetts
(fig. 1) and consist of flat to gently rolling lowlands ranging from sea level to about 400 ft. The
border between the Coastal Lowlands and the Eastern New England Upland is distinct and abrupt
In the northern part of the State it is defined by an east-facing scarp as much as 300 ft high running
from Worcester to the New Hampshire border along the west side of the Nashua River valley
(Denny, 1982). The Coastal Lowland is underlain primarily by Proterozoic through Tertiary-age
sedimentary rocks intruded by Proterozoic and Paleozoic granites and granite gneisses.
In 1990 the population of Massachusetts was 6,016,425, including 84 percent urban
population (fig. 3). Average population density is approximately 700 per square mile. The climate
of Massachusetts is temperate, although it is colder and drier in the western region. Average
annual precipitation ranges from 40 to 48 in (fig. 4).
BEDROCK GEOLOGY
Massachusetts has been divided into major geologic belts and zones (fig. 5) that will be
described from west to east across the State. For simplicity the groupings shown in figure 5 are
modified from those presented in Zen (1983). The geologic descriptions that follow are derived
from several sources including Zen (1983), Rankin and others (1989), and Page (1976). A
generalized bedrock geologic map is given for reference in figure 2. It is suggested, however, that
the reader refer to the published State Geologic Map of Massachusetts (Zen, 1983), large-scale,
local geologic maps and reports, and other references for more detail.
The Taconic-Berkshire Zone (figs. 2, 5) consists of sedimentary, metasedimentary, and
metavolcanic rocks of the Taconic Mountains, Stockbridge Valley, and Berkshire Mountains, that
are locally intruded by granitic rocks. The Taconics in Massachusetts consist of all or parts of the
Everett, Berlin Mountain, and Greylock thrust slices (fig. 5). The southern part of the Everett slice
is underlain almost entirely by the Everett Formation, consisting of phyllite, metagraywacke, and
quartzite. The northern part of the Everett slice is underlain by the Everett and Nassau Formations.
The Nassau formation consists of phyllite, quartzite, metasiltstone, subgraywacke, and local
conglomerate and volcanic rocks. The Berlin Mountain slice, which lies to the north of the Everett
slice, is underlain almost entirely by Nassau Formation. The Greylock slice, to the east of the
main body of the Taconics, is underlain primarily by the Greylock Schist, which consists of
phyllite with interbedded quartzite, metagraywacke, dolostone, and conglomerate. To the east of
the Taconic Mountains lies the Vermont-Stockbridge Valley Autochthon, which is underlain by the
Stockbridge Formation, comprising limestone, dolostone, quartzite, and marble, locally containing
interbeds of phyllite and quartzite; and the Walloomsac Formation, consisting of graphitic phyllite
and schist, quartzite, calcareous quartzite, calcareous marble, and limestone. The Berkshire massif
and the southern tip of the Green Mountain anticlinorium underlie most of the Berkshire
Mountains. The Berkshire massif consists of a complex thrust-faulted group of thrust slices made
up of Middle Proterozoic metamorphic rocks of sedimentary and volcanic origin (Rankin and
others, 1989), including biotite gneiss, quartzite, amphibolite, biotite-quartz-feldspar gneiss, mafic
gneiss, granofels, schistose gneiss, granulite, and bedded magnetite rock: Rocks of the Berkshire
massif are intruded by biotite granite, granodiorite, and granitic gneiss, including the Stamford
Granite Gneiss and the Tyringham Gneiss; and locally by peridotite stocks, mafic dikes, magnetite-
IV-10 Reprinted from USGS Open-File Report 93-292-A
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bearing alaskite, and trondhjemite (Zen, 1983). Included in the Taconic-Berkshire Zone for this
discussion are rocks of the Middlefield thrust comprising the Sherman Marble, a coarse-grained
graphite-dolomite-calcite marble exposed at Sherman Reservoir at the Vermont border, and the
Hoosac Formation, consisting of phyllite, schist, gneiss, quartzite, calc-silicate rocks, granofels,
and amphibolite. These rocks are locally intruded by granite, granodiorite, and diorite.
The Connecticut Valley Belt consists of metasedimentary rocks of the Connecticut Valley
Synclinorium and Bronson Hill Anticlinorium (fig. 5), which are separated by sedimentary rocks
of the Mesozoic basins (discussed separately) and intruded by various granitic plutons. To the
west of the Connecticut Valley Synclinorium are rocks of the Whitcomb Summit thrust, included in
this belt for the purposes of this discussion and comprising the Rowe Schist; the Moretown
Formation, consisting of light-colored granofels and schist, and dark-colored amphibolite and
greenstone; the Cobble Mountain Formation, comprising feldspathic gneiss, mica schist,
aluminous schist, politic schist, serpentinite, and calc-silicate rock; and the Hawley Formation,
consisting of interbedded amphibolite, greenstone, feldspathic schist, granofels, and mafic gneiss
and schist These rocks are intruded locally by the Middlefield Granite, a biotite gneiss at
Hallockville Pond, and by serpentinite and/or talc rock. Rocks of the Connecticut Valley
Synclinorium include the Clough Quartzite; Fitch Formation, consisting of granofels, schist, and
marble; the Russell Mountain Formation, comprising quartzite, granofels, and marble; the Littleton
Formation, consisting of schist and phyllite, which underlies the northern part of this map unit;
Erving Formation, including granofels, mica schist, and amphibolite; Goshen Formation,
consisting of quartzite and quartz schist grading upward into carbonaceous schist; the Waits River
Formation, consisting of interbedded schist, calcareous granofels, and marble, and amphibolite
and hornblende schist; Gile Mountain Formation, comprising phyllite and schist interbedded with
calcareous granofels and marble; the Putney Volcanics, consisting of plagioclase-quartz-muscovite
phyllite and granofels. The Williamsburg Granodiorite underlies the eastern edge of the
Synclinorium near Northampton. The Shelburne Falls, Goshen, and Granville Domes are
underlain by the Collinsville Formation, consisting primarily of schist, mafic and felsic gneiss,
granofels, and amphibolite.
The eastern part of the Connecticut Valley Belt consists of several domes underlain by
mafic gneisses (black unit on fig. 2), surrounded by younger schists and amphibolites (white unit
on fig, 2) and intruded by several granitic complexes. The Pelham dome comprises the Dry Hill
Gneiss, consisting of microcline-homblende gneiss, schist, and quartzite; Mount Mineral
Formation, which consists of schist, amphibolite, and quartzite; and the Poplar Mountain Gneiss,
consisting of biotite gneiss and quartzite. The Monson Gneiss, comprising biotite-plagioclase
gneiss, amphibolite, and microcline augen gneiss, underlies the main part of the Bronson Hill
Anticlinorium and the Tully dome (fig. 5). The Glastonbury Gneiss is a granitic gneiss that forms
the core of the Glastonbury dome. The Pauchaug Gneiss is a granitic gneiss forming the core of
the Warwick dome. The Fourmile Gneiss, consisting of biotite-feldspar gneiss and amphibolite,
surrounds the east and south sides of the Pelham dome and the northwestern flank of the
Glastonbury dome. Other granitic complexes include the Belchertown Complex, which lies mainly
to the east of the Hartford basin, but underlies a small area to the west of the basin; and the Prescott
Complex. The Belchertown Complex consists of quartz monzodiorite and monzodiorite gneiss,
hornblende peridotite and hornblendite, and inclusions of mafic and ultramafic rocks, dacite, and
tonalite. The Prescott Complex consists of biotite to tonalite granite with intrusions of hornblende
gabbro and schist and phyllite of the Littleton Formation.
IV-14 Reprinted from USGS Open-File Report 93-292-A
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The Mesozoic Basins consist of late Triassic-early Jurassic continental sedimentary and
igneous rocks of the Newark Supergroup occurring in three half-graben basins extending north-
south in the west-central part of the State. Each basin has eastward dipping rocks which are folded
into a broad syncline along the faulted eastern margin. The Hartford basin is the largest of the
three, extending northward from Connecticut. The basal Triassic New Haven Arkose consists of
fluvial arkosic sandstone and conglomerate forming a wide band on the western side of the basin.
The New Haven Arkose is overlain by a narrow belt of Jurassic volcanic and sedimentary rocks
that include the Shuttle Meadow Formation, Holyoke Basalt, East Berlin Formation, and the
Hampden Basalt. The Shuttle Meadow and East Berlin Formations comprise a mixture of
sandstone and conglomerate, and red and black lacustrine shales. The Holyoke and Hampden
Basalts (and the Hampden Basalt equivalent called the Granby Basaltic Tuff) are tholeiitic basalt
flows. The eastern part of the Hartford basin is a wide belt of sedimentary rocks of the Jurassic
Portland Formation. The lower part of the Portland consists of lacustrine black shales and red
siltstones and the upper part consists of fluvial sandstones and conglomerates. Along the eastern
margin of the basin all of the formations intertongue with conglomerates made up of clasts of the
older rocks immediately outside of the basin. The Deerfield basin is a much smaller half graben
north of the Hartford basin that is connected to it by a narrow band of New Haven Arkose. The
basal Triassic Sugarloaf Arkose, which is similar to the New Haven Arkose, forms a broad band
on the eastern side of the basin. The uppermost part of this formation contains a thin belt of
Jurassic lacustrine black shales and red siltstones. The Sugarloaf Arkose is overlain by the thin
Jurassic Deerfield Basalt, which is overlain by the Jurassic Turners Falls Formation, then the
Mount Toby Formation, each forming moderately thick bands within the syncline. Both of these
units contain a mixture of sandstone and conglomerate and red and black lacustrine shales, but the
Mount Toby is more conglomeratic. As in the Hartford basin, all formations intertongue with
alluvial fan conglomerates along the eastern border fault. The Northfield basin is a small half
graben north of the Deerfield basin and connected to it by a narrow belt of Sugarloaf Formation. It
is filled entirely with Sugarloaf conglomeratic sandstone. Jurassic diabase dikes and sills intrude
the sedimentary rocks of all of the basins.
The Merrimack Belt consists of metavolcanic and metasedimentary rocks intruded by a
number of granitic plutons. Metavolcanic rocks dominate the western part of the Merrimack belt
and include the Ammonoosuc Volcanics, consisting of amphibolite, quartzite, ultramafic rocks,
felsic gneiss, and marble, with quartzite and conglomerate at the base; the Partridge Formation,
comprising mica schist, amphibolite, calc-silicate rock, and mafic and felsic gneisses of volcanic
origin; the Fitch Formation, consisting of sulfidic calc-silicate and sulfidic schist; and the Littleton
Formation, consisting of aluminous mica schist and phyllite, and quartzose schist, gneiss, and
marble; and the Erving Formation, which consists primarily of biotite-plagioclase granofels. These
rocks are locally intruded by lenses and dikes of granite, granodiorite, and granitic gneiss. The
eastern part of the Merrimack belt is primarily underlain by metasedimentary rocks, including the
Boylston Schist; Reubens Hill Formation, including amphibolite and schist; the Vaughn Hills
Quartzite; Tower Hill Quartzite; phyllite of the Eliot Formation; Berwick Formation, consisting of
metamorphosed sandstone and siltstone, and mica schist; the Oakdale Formation, consisting of
metasiltstone and muscovite schist; the Paxton Formation, comprising granofels, schist,
amphibolite, and quartzite; and slate and phyllite of the Worcester Formation. The Harvard
Conglomerate and the Coal Mine Brook Formation, consisting of slate, phylh'te, thin meta-
anthricite, conglomerate and arkose, underlie the Worcester basin (fig. 5), located at the eastern
edge of the Merrimack belt, to the east and northeast of Worcester.
IV-15 Reprinted from USGS Open-File Report 93-292-A
-------
A number of granitic intrusions occur in the Merrimack belt; they will be discussed in order
roughly from west to east (refer to fig. 5). The Hardwick Pluton consists of the Hardwick
Tonalite, a biotite tonalite to granodiorite gneiss, and biotite-muscovite granite. The Coys Hill
Pluton, which forms a thin band directly to the east of the Hardwick, contains porphyritic
microcline granite gneiss with hornblende gneiss inclusions. The West Warren Plutons are located
at the southern tip of the Coys Hill Pluton and consist of biotite-hornblende diorite, quartzose
diorite, metadiorite, and norite. The Fitchburg Pluton consists of muscovite-biotite granite,
granodiorite, granodiorite gneiss, and pegmatite; biotite granodiorite to tonalite gneiss; and zones
and inclusions of granite gneiss, mica schist, and biotite-hornblende tonalite. The southern tip of
the Massabesic Gneiss Complex extends into Massachusetts just to the east of the Fitchburg
Complex (fig. 5). The Massabesic Gneiss Complex consists of biotite-feldspar gneiss intruded by
potassium feldspar gneiss and biotite granite containing magnetite-bearing pegmatites. The Ayer
Pluton consists of the Ayer Granite, a biotite granite to tonalite; and the Chelmsford Granite, a
muscovite-biotite granite. Southwest of the Ayer Pluton is a small body of muscovite-biotite
granite at Millstone Hill that is not shown separately on the generalized geologic map (fig. 2). To
the east of the Ayer Pluton lies the Dracut Pluton, comprising the Dracut Diorite. The
Newburyport Complex is an intrusion of gray granite, tonalite, and granodiorite located in the
northeasternmost corner of Massachusetts (figs. 2, 5).
The Esmond-Dedham Zone consists of metasedimentary rocks of the Nashoba terrane, and
a series of britfley deformed terranes, gneissic terranes, and. granitic plutons (the Milford-Dedham
zone of Zen (1983)). The Nashoba terrane is separated from the low-grade metamorphic rocks of
the Merrimack synclinorium by the Clinton-Newberry Fault system (fig. 5). Eastward across the
fault the metamorphic grade increases abruptly, then abruptly decreases across the Bloody Bluff
Fault, which marks the eastern margin of the Nashoba terrane. Major rock units in the Nashoba
terrane include the Marlboro Formation, characterized by amphibolite with lesser amounts of
metasedimentary or metavolcanic gneisses; Quinebaug Formation, consisting of amphibolite and
mafic, felsic, and calc-silicate gneiss; the Fish Brook Gneiss, a biotite-feldspar quartz gneiss;
Shawsheen Gneiss, a sillimanite gneiss with minor amphibolite; and the Nashoba Formation,
consisting primarily of feldspathic to aluminous schists and other metasedimentary or metavolcanic
gneisses. Overlying this sequence is the Tadmuck Brook Schist, which is equivalent in age to the
Andover Granite (Andover pluton on fig. 5). The youngest rocks in this sequence are the
Sharpners Pond Diorite and related calc-alkalic igneous rocks (Rankin and others, 1989).
Preeambrian granitic suites can be divided into two groups, the Milford-Ponaganset Plutonic Suite
and the Esrnond-Dedham Plutonic Suite. Both groups contain areas of metasedimentary rocks but
they consist primarily of granite, with lesser amounts of granodiorite and tonalite. The Milford-
Ponaganset Plutonic Suite occupies the Rhode Island Anticlinorium (fig. 5) and includes the Hope
Valley Alaskite, a mafic-poor granite gneiss; Scituate Granite Gneiss; Ponaganset Gneiss, a
gneissic biotite granite; and the Milford Granite, dominantly a light-colored biotite granite and
granodiorite. To the northeast of this area, between the Bloody Bluff Fault and the Northern
Border Fault, lies an area of brittley-deformed terrane consisting of granitic, volcanic, and
metavolcanic rocks including diorite, granodiorite, gabbro, and serpentinite; the Lynn Volcanic
complex, on the northern edge of the Boston Basin, consisting of rhyolite, agglomerate, and tuff;
and metasedimentary rocks of the Westboro Formation. The Newbury basin, underlain by the
Newbury Volcanic Complex, consisting of rhyolite, andesite, and sedimentary rocks, lies at the
northern end of this zone. South of the Newbury basin, The Cape Ann and Peabody Plutons, and
the Quincy Pluton to the south of the Boston basin, consist of alkalic granites, monzonites,
IV-16 Reprinted from USGS Open-File Report 93-292-A
-------
monzodiorites, and alaskitic granites of the Cape Ann Complex, Quincy Granite, Blue Hill Granite
Porphyry, Cherry Hill Granite, Wenham Monzonite, and Peabody Granite. The Esmond-Dedham
Plutonic Suite lies to the southeast of the Boston basin and the Milford-Ponaganset Plutonic Suite.
The rocks of the Esmond-Dedham suite are similar to those of the Milford-Ponaganset Plutonic
Suite except that hornblende is more common whereas biotite is less common (Rankin and others,
1989). The Esmond-Dedham Plutonic Suite includes the Westwood and Dedham Granites, the
Sharon Syenite, alaskite, diorite, granites of the Rattlesnake Hill and Fall River Plutons, and a
small body of alkalic granite near Franklin. Also included in this map unit are felsic and mafic
volcanic rocks southwest of the Boston basin and hornblende and biotite gneiss and schist near
New Bedford. Just east of the eastern margin of the Narragansett basin is a granite thought to
correlate with the Dedham Granite, along with metasedimentary and metavolcanic rocks also
presumed to be late Precambrian in age. Proceeding southeast, the granitic and gabbroic rocks
become progressively more intensely deformed, terminating in shear zones. Among the highly
deformed granitic rocks occurs a relatively massive alkalic granite, similar to the Scituate granite,
the exact age and origin of which is currently not known.
The Narragansett basin, Boston basin, and Norfolk basin are underlain by late Precambrian
to Pennsylvanian sedimentary, metasedimentary, and volcanic rocks. In the Boston basin, the
oldest rocks are felsic volcanic rocks of the Lynn and Mattapan Volcanic Complexes. Overlying
the volcanic rocks is a sequence of coarse-grained clastic sedimentary rocks belonging to the
Boston Bay Group, which contains two formations, the Roxbury Conglomerate and the
Cambridge Argillite. This map unit also includes the Bellingham Conglomerate. The Narragansett
basin is underlain Primarily by the Rhode Island Formation, consisting of sandstone, shale,
graywacke, and conglomerate; and the Dighton Conglomerate. The Hoppin Formation, consisting
of quartzite, argillite, and minor limestone, underlies Hoppin Hill, in the northwestern part of the
Narragansett basin (fig. 5). The Norfolk basin, a narrow, east-west trending basin located
between the Narragansett and Boston basins, is underlain by the Pondville quartz conglomerate
and the Wamsutta Formation, consisting of conglomerate, graywacke, sandstone, shale, and minor
rhyolite and mafic volcanic rocks. Cretaceous and Tertiary sedimentary rocks and unconsolidated
sediments underlie Nantucket island and Martha's Vineyard (fig. 2).
GLACIAL GEOLOGY
Deposits of five or possibly six Pleistocene glacial advances in New England have been
recognized or inferred from surface or subsurface data (Stone and Borns, 1986); however, two
main till units are mapped throughout much of southern New England (Richmond and Fullerton,
1991). Glacial deposits exposed at the surface in Massachusetts are of Late Wisconsin age.
Glaciers moved in a dominantly N-S or NW-SE direction across the State, terminating on Long
Island, Martha's Vineyard, and Nantucket Island at their maximum extent In Late Wisconsin
time, parts of four glacial lobes advanced across Massachusetts. The Connecticut Valley Lobe
covered the western part of the State and carved the Connecticut Valley Lowland. The Charles-
Merrimack Lobe covered the northern part of the coastal lowland. The Narragansett-Buzzard's
Bay Lobe and the Cape Cod Bay Lobe covered the southern part of the coastal lowland and Cape
Cod (fig. 6). The final retreat of Wisconsinan glaciers from Massachusetts occurred about 12,000
years ago (Stone and Borns, 1986).
IV-17 Reprinted from USGS Open-File Report 93-292-A
-------
1^1 V } rj' ''NEW \o
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IVORK' A// [, (^5
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NARRAGANSETT BAY-
BUZZARDS BAY LOBE
Figure 6. Major late Wisconsin glacial lobes of New England. Arrows indicate maior directions
of ice advances (from Stone and Borns, 1986).
-------
Figure 7 is a generalized map of glacial deposits in Massachusetts. The glacial deposits are
divided into two main categories, till and stratified glacial deposits. Till, sometimes also referred to
as drift or ground moraine, is the most widespread glacial deposit (fig. 7), covering about 63
percent of the State (Stone, 1982). Till was deposited directly by glacier ice and it is composed of
a nonsorted matrix of sand, silt, and clay containing variable amounts of rounded cobbles and
boulders. Till composition generally reflects the local bedrock. The "upper till", which covers
most of the surface mapped as till on figure 7, is sandy to gravelly and locally calcareous. It
typically overlies a "lower till" which is more clayey, more compact, and less bouldery that the
upper till (Richmond and Fullerton, 1991). Till thickness averages 3-5 m (Stone, 1982), and is
rarely more than 10 m (Richmond and Fullerton, 1.991). Glacial landforms typically associated
with till include drumlins, kettles, and moraines. The Martha's Vineyard and Nantucket moraines
(fig. 7) are part of a larger terminal moraine complex that stretches from Long Island to Nantucket.
These moraines were deposited approximately 21,000 years ago (Stone and Borns, 1986). The
Sandwich and Buzzard's Bay moraines are also part of a large moraine complex that was deposited
approximately 18,000 years ago (Stone and Borns, 1986). Remnants of smaller, younger
moraines, such as the Monk's Hill Moraine (fig. 7), are found in the southern coastal lowland.
Glacial meltwater deposits were laid down in streams and lakes in front of the retreating ice
margin. They are characterized by layers of poorly-sorted to well-sorted gravel and sand with
minor beds of silt and clay. Thickness of these deposits ranges from 5-40 m (Richmond and
Fullerton, 1991). Meltwater deposits are subdivided into two categories on figure 7. Glaciofluvial
deposits consist primarily of outwash (layered sand and gravel deposited by glacial meltwater
streams), but also include deposits of kames and eskers, kame terraces, and collapsed stratified
drift. Outwash is generally the coarsest-grained class of glacial deposits because most of the silt
and clay was removed by the rapidly-moving water. The other types of deposits, referred to as
ice-contact stratified drift, range from poorly sorted to well sorted and consist of sand, gravel,
cobbles, and boulders, with varying amounts of silt and clay, though they generally contain
considerably less fine-grained material than till. Glaciofluvial deposits cover about 7 percent of the
State (Stone, 1982).
Glaciolacustrine deposits, the second category of glacial meltwater deposits, were
deposited in or adjacent to glacial lakes that formed at the edge of the retreating glacier and
occupied topographic basins. Glaciolacustrine deposits cover about 28 percent of the State and
include lake-bottom sand, silt, and clay, and lacustrine delta silt, sand, and gravel (Stone, 1982).
Silt and clay are the dominant grain sizes in lake bottom sediments (Zoino and Campagna, 1982).
Coarse-grained glaciofluvial valley fill deposits, which supplied sediment to the glacial lake deltas,
are also included in this map unit (fig. 7). Large glacial lakes in Massachusetts include lakes
Hitchcock and Westfield, in the Connecticut River basin; the Taunton basin lake in southeastern
Massachusetts; and lakes Nashua and Charles in northeastern Massachusetts (fig. 7).
Glaciomarine deposits form a separate category of glacial deposits shown on figure 7.
These deposits consist of silt and clay marine bottom sediments and silt, sand, and gravel delta
sediments, which were deposited in ocean water. Glaciomarine deposits cover about 2 percent of
Massachusetts (Stone, 1982).
IV-19 Reprinted from USGS Open-File Report 93-292-A
-------
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SOILS
Soils in Massachusetts include Inceptisols, mineral soils with horizons of alteration or
accumulation of metal oxides such as iron, aluminum, or manganese; Entisols, mineral soils with
no discernible horizons because their parent material is inert (such as quartz sand) or because the
soils are very young; and Histosols, organic soils such as peats or mucks which occur along
coastlines or in river valleys. Figure 8 is a generalized soil map of Massachusetts (U.S.
Department of Agriculture, 1989). The following discussion is condensed from the general soils
map of Massachusetts (U.S. Department of Agriculture, 1989) and from U.S. Soil Conservation
Service county soil surveys. State- and county-scale soil survey reports should be consulted for
more detailed descriptions and information.
Very deep, loamy and sandy soils formed in glacial till derived from granite, schist and
gneiss on upland till plains and moraines cover about 45 percent of Massachusetts (fig. 8). The till
is a stony and bouldery, unsorted and unstratified material consisting of a heterogeneous mixture
of sand, silt, clay, gravel, stones, and boulders. These soils are moderately well- to well drained
and have a loamy or sandy surface layer and a firm (typically clayey) to friable (loosely packed,
easily separated, and permeable) substratum. Soils with friable subsurface layers have moderate
permeability, whereas those with firm substrata have low permeability. This map unit consists of
gently sloping to very steep soils on hilltops and hillsides throughout the State. Most areas
underlain by the soils of this unit are forested.
Very deep, loamy soils formed in glacial till derived from limestone and crystalline rocks
on upland till plains occur in the extreme western part of the State (fig. 8). This map unit consists
of nearly level to very steep soils, mainly in the central valley region of Berkshire County. These
soils are moderately drained to well drained, typically have a friable substratum, and have moderate
permeability. Areas underlain by these soils are extensively farmed. This map unit makes up
about 5 percent of the State.
Very deep, loamy and sandy soils formed in glacial outwash, lacustrine, and alluvial
sediments, on outwash plains and in stream valleys are found in the Connecticut Valley and eastern
Massachusetts (fig. 8). This map unit consists of nearly level to moderately steep soils. Soils
formed from glacial outwash are well drained to excessively drained and have high permeability.
Soils formed from alluvial deposits include poorly-drained soils in valley bottoms and moderately
drained to well-drained soils on terraces and floodplains. Alluvial soils have moderate to high
permeability. Glaciolacustrine sediments formed from postglacial lakes. Fine particles (silt and
clay) that were held in suspension within these lakes settled out and formed alternating layers of silt
and clay. This map unit also includes soils formed on glaciomarine sediments, primarily silt and
clay that were deposited by glaciers in ocean water. Soils formed on glaciolacustrine and
glaciomarine sediments have low to moderate permeability. Alluvial, glaciolacustrine, and
glaciomarine soils in low-lying areas may be subject to high water tables and flooding. Most areas
underlain by soils of this unit are cleared and are used for agricultural and commercial uses. This
map unit makes up about 30 percent of the State.
Moderately deep to shallow, loamy soils formed in glacial till on bedrock-controlled
uplands cover about 15 percent of the State (fig. 8). Generally in Massachusetts, areas of shallow
soils are a complex of rock outcrop, shallow-to-bedrock soils (10-20 inches of soil over bedrock),
moderately deep soils (20-40 inches of soil over bedrock), and very deep soils (greater than 60
inches of soil over bedrock). These soils are well- to excessively drained and have moderate
permeability. This map unit consists of gently sloping to very steep soils on hilltops and hillsides,
IV-21 Reprinted from USGS Open-File Report 93-292-A
-------
mainly in the western and eastern parts of the State. Most areas underlain by this soil unit are
forested.
Areas mapped as urban land (fig. 8) consist of nearly level to moderately steep areas where
the soils have been altered or obscured by urban works and structures. Buildings, industrial areas,
and paved areas cover more than 75 percent of the surface. The properties and characteristics of
this map unit are highly variable.
RADIOACTIVITY
An aeroradiometric map of Massachusetts (fig. 9) compiled from National Uranium
Resource Evaluation (NURE) flightiine data (Duval and others, 1989) shows several high
radioactivity areas in the State. Low radioactivity (<1.5 ppm elJ) is associated with the gneisses
and amphibolites of the Berkshire massif; the Waits River Formation in the northern Connecticut
Valley Synclinorium; with mafic and ultramafic rocks of the gneissic domes in the eastern
Connecticut Valley Belt; with volcanic rocks in and south of the Newbury basin; and with mostly
mafic granites and gneisses, including the Ponaganset Gneiss, south and southwest of Boston.
Low to moderate radioactivity is associated with sedimentary rocks of the Narragansett basin. A
prominent radiometric low in the eastern Connecticut Valley Belt is associated with Quabbin
Reservoir. Moderate radioactivity (1.5-2.5 ppm) covers the southern and central Taconic
Mountains, the Mesozoic basins and southern part of the Connecticut Valley Synclinorium, and
scattered areas throughout the Merrimack Belt, associated mainly with Paleozoic-age metamorphic
rocks. High radioactivity (>2.5 ppm) is associated with black phyllitic schist of the Walloomsac
Formation in the northern Taconics; with granite gneiss in the southern part of the Warwick Dome;
with the Hardwick Tonah'te in north-central Massachusetts; and with granitic plutons and glacial
deposits containing significant amounts of granitic rock as source material in the Merrimack Belt.
A group of small high (>2.5 ppm eU) radioactivity areas occurs in a roughly arcuate pattern
extending from the center of the Hartford basin north of Springfield into the southern part of the
Connecticut Valley Synclinorium just north of the Granville Dome.
Conglomerate beds of the Dalton Formation, on the west side of the Berkshire Mountains,
have radioactivity 3-7 times background, which, although caused mostly by thorium (Field and
Truesdell, 1982), may also contain elevated uranium concentrations. The Tyringham Gneiss
locally contains up to 11 ppm uranium on the west side of the Berkshire Mountains southeast of
Stockbridge. Other parts of the Tyringham Gneiss have normal radioactivity (Field and Truesdell,
1982), Precambrian gneiss south of Adams contains 5-10 ppm uranium, and locally as much as
80 ppm in a small pegmatite. There are no reported uranium occurrences in the Newark
Supergroup of Massachusetts but there are some units likely to have elevated uranium
concentrations. Carbonaceous debris in fluvial crossbeds in the uppermost New Haven Arkose
and Sugarloaf Formation and in the middle portion of the Portland Formation are similar to
reported uranium-bearing units in the Triassic of Connecticut (Robinson and Sears, 1988). Black
shales and deltaic gray sandstones in the Shuttle Meadow, East Berlin, lower Portland, Turners
Falls, and lower Mount Toby formations may also have elevated uranium. The basalts and
diabases, the lower portions of the New Haven Arkose and Sugarloaf Formations, and the upper
portions of the Portland and Mount Toby Formations are not likely to have significant uranium
concentrations, except possibly along fractures.
IV-23 Reprinted from USGS Open-File Report 93-292-A
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The Warwick and Vernon domes have cores of the Pauchaug Gneiss, a massive feldspathic
gneiss containing 1-2 ppm uranium on average. However, the south end of the Warwick dome
contains an area with 5-33 ppm uranium, whteh can be easily seen on the aeroradioactivity map
(fig. 9). The Hardwick Tonalite was found to contain up to 4 ppm uranium near Athol. Small
granite bodies in the North Brookfield area had radioactivity 3-4 times background, possibly due to
high potassium-feldspar content (Field and Truesdell, 1982). Radiometric anomalies in the
Merrimack Belt and Esmond-Dedham Zone appear to generally correlate with the locations of
granitic plutons, including the Hardwick, Coys Hill, Fitchburg, Ayer, Dracut, Newburyport,
Andover, Cape Ann, Peabody, and Quincy plutons. The widespread appearance of the radiometric
highs probably reflect the overlying glacial till, which incorporates fragments of granitic rock from
the various plutons, that has spread over most of northeastern Massachusetts. Chemical analyses
of samples of the Quincy Granite yielded as much as 33 ppm uranium (Zollinger and others,
1982). Uranium occurs in pegmatites in the Cape Ann Complex in Essex County; the Loudville
Lead Mine and at West Chesterfield in Hampshire County; in the Dedham Granite and in
pegmatites at Blueberry Mountain in Middlesex County; and in pegmatites at the foot of Long Hill
in Leominster and on Rollstone Hill in Fitchburg, Worcester County (Grauch and Zarinski, 1976).
Only one uranium occurrence has been reported in Pennsylvanian sedimentary rocks of the
Narragansett basin. It consists of an iron-stained zone in the Dighton Conglomerate that yielded 14
ppm uranium (Zollinger and others, 1982). Areas along cataclastic and mylonitic fault and shear
zones, particularly the Lake Char fault zone (Zollinger and others, 1982), may host significant
uranium concentrations and generate locally elevated radon because shear zones tend to concentrate
and redistribute uranium to sites of high emanation, and because shear zones typically have
enhanced permeability compared to surrounding rocks (Gundersen, 1991).
INDOOR RADON
Indoor radon data from 1664 homes sampled in the State/EPA Residential Radon Survey
conducted in Massachusetts during 1988 are shown in figure 10 and listed in Table 1. A map of
counties is included for reference (fig. 11). Indoor radon was measured by 2-7 day charcoal-
canister screening tests. Data for Berkshire and Dukes Counties, and for Franklin and Hampshire
Counties, which each contain fewer than 100 samples, are shown both individually and combined
in Table 1. Data for these counties were combined by the Massachusetts Department of Public
Health to achieve a statistically representative sample at the county level (the pairs of combined
counties were treated as one county). Average (arithmetic mean) values reported here and used in
the Radon Index evaluations may be subject to bias by extremely high values, especially if the
sample size is relatively small, and thus may not necessarily represent "typical" indoor radon
values in each county. A comparison of county averages with the corresponding number of
samples, median, geometric mean, and maximum (Table 1) can indicate instances in which the
county indoor radon average has been artificially elevated by the influence of one or more high
values. Maximum indoor radon levels listed in Table 1 represent the highest screening indoor
radon level recorded in the 1988 State/EPA survey, and do not necessarily indicate the highest
possible indoor radon levels in each county. However, these values may be helpful in giving a
general, relative indication of where locally high indoor radon levels are likely to occur.
The statewide indoor radon average for Massachusetts was 3.3 pCi/L and 24 percent of the
homes tested in the State had indoor radon levels exceeding 4 pCi/L. Notable counties include
Dukes, Essex, Middlesex, and Worcester, in which the average indoor radon for each county
IV-25 Reprinted from USGS Open-File Report 93-292-A
-------
Bsmt & 1st Floor Radon
%>4pCi/L
OtolO
11 to 20
21 to 30
31 to 40
Missing Data or < 5 measurements
Bsmt & 1st Floor Radon
Average Concentration (pCi/L)
0.0 to 1.9
2.0 to 4.0
4.1 to 4.6
Missing Data or < 5 measurements
50 Miles
Figure 10. Screening indoor radon data from the EPA/State Residential Radon Survey of
Massachusetts, 1988, for counties with 5 or more measurements. Data are from 2-7 day charcoal
canister tests. Histograms in map legends show the number of counties in each category. The
number of samples in each county (See Table 1) may not be sufficient to statistically characterize
the radon levels of the counties, but they do suggest general trends. Unequal category intervals
were chosen to provide reference to decision and action levels.
-------
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exceeded 4 pCi/L. Counties with 25 percent or more homes exceeding 4 pCi/L include Dukes,
Essex, Franklin, Middlesex, and Worcester. The 4.6 pCi/L average and high percentage of homes
exceeding 4 pCi/L for Dukes County may be somewhat misleading, however, as the median
indoor radon value was 1.2 pCi/L and only 6 homes were sampled in this county. Although not
necessarily representative of the whole county, it does indicate that some homes with indoor radon
levels exceeding 4 pCi/L are found on Martha's Vineyard and further testing is warranted. The
Martha's Vineyard Moraine has high permeability and incorporates clasts of more radon-rich rocks
from north of this area, and may be a source for elevated indoor radon levels on Martha's
Vineyard. No homes were sampled on Nantucket Island.
TABLE 1. Screening indoor radon data from the State/EPA Residential Radon Survey of
Massachusetts conducted during 1988. Data represent 2-7 day charcoal canister tests.
COUNTY
BARNSTABLE
BARNSTABLE
+DUKES
BERKSHIRE
BRISTOL
DUKES
ESSEX
FRANKLIN
FRANKLIN
•(•HAMPSHIRE
HAMPDEN
HAMPSHIRE
MIDDLESEX
NORFOLK
PLYMOUTH
SUFFOLK
WORCESTER
NUMBER
ofMEAS.
99
105
47
115
6
203
26
80
125
54
400
171
141
61
216
AVERAGE
2.1
2.2
3.3
2.8
4.6
4.1
3.3
2.8
2.0
2.6
4.1
3.0
2.0
1.7
4.6
STD.
DEV.
2.0
2.6
3.8
3.4
7.4
5.1
3.4
2.9
2.4
2.6
7.0
3.5
2.0
1.3
5.3
4.9
MF.DTAN
1.6
1.6
1.9
1.8
1.2
2.8
1.6
1.6
1.3
1.6
2.2
1.9
1.4
1.2
2.8
1.9
GEOM.
MEAN
1.5
1.6
1.8
1.8
1.9
2.6
2.1
1.9
1.4 '
1.8
2.3
2.0
1.4
1.4
2.9
2.0
MAX
12.5
19.5
15.7
28.8
19.5
52.4
12.6
14.1
22.9
14.1
61.3
30.1
14.7
8.0
41.1
61.3
%>4 pCi/L
14
15
21
22
33
36
31
23
11
19
26
21
12
5
38
24
%>20 pCi/L
0
0
0
1
0
1
0
0
1
0
3
1
0
0
3
1
GEOLOGIC RADON POTENTIAL
The metamorphic rocks of the Taconic Mountains and carbonate sedimentary and
metasedimentary rocks of the Vermont-Stockbridge Valley have been ranked moderate in geologic
radon potential. Soil permeability is generally moderate. Radioactivity is moderate with one
distinctive anomaly. Graphitic phyllites and schist of the Walloomsac Formation have moderate to
high radioactivity associated with them and may produce locally elevated indoor radon levels.
Elevated radon may also be associated with fault and shear zones, especially in the Taconics.
The Berkshire Mountains have been ranked moderate overall in radon potential. The
granitic to dioritic gneiss and schist have generally low equivalent uranium associated with them.
Shear zones, pegmatites, and local accumulations of monazite in biotite schist and gneiss may be
sources of locally high indoor radon levels. Soil permeability is low to moderate. Hall and others
(1985) classified these rocks as having variable low to high uranium enrichment
IV-28 Reprinted from USGS Open-File Report 93-292-A
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Metamorphic rocks of the Connecticut Valley Belt, on the eastern and western sides of the
Mesozoic basins, have been ranked moderate in geologic radon potential. Metasedimentary and
metavolcanic gneisses and schists have generally low to moderate radioactivity associated with
them. Soils have generally moderate permeability. The Pauchaug and Glastonbury granite
gneisses, which form the cores of the Warwick and Glastonbury domes, as well as other locally-
occurring granitic rocks, may generate locally high indoor radon levels. Locally high radon is
likely to be associated with the area of anomalous radioactivity at the south end of the Warwick
dome and may be associated with faults and shears throughout the area.
Mesozoic sedimentary and igneous rocks of the Hartford, Deerfield, and Northfield basins
in the Connecticut Valley have been ranked moderate or variable overall in radon potential. Most
of the sedimentary rocks in the basins have low radon potential but locally high indoor radon may
be associated with Jurassic-age black shales and localized uranium deposits in fluvial sandstone
and conglomerates. Soil permeability is low to moderate in glacial lake-bottom sediments that
cover most of the Hartford basin, and moderate to high in glaciofluvial deposits, including
outwash, lacustrine delta deposits, and alluvium in the basins. Radioactivity is generally moderate
but contains scattered radiometric highs in the central Hartford basin.
Granitic plutons of the Merrimack Belt have been ranked high in geologic radon potential.
The metasedimentary rocks surrounding the plutons are predominantly phyllites and carbonaceous
slates and schists with moderate to high radon potential. Mafic metamorphic rocks, which are less
common in the Merrimack Belt, have generally low to moderate radon potential. Faults and shear
zones may produce locally high radon concentrations. Equivalent uranium (fig. 9) is high over
most of the area and the soils have low to moderate permeability. Overall, this area is ranked high
in geologic radon potential.
Granitic plutonic rocks and metamorphic rocks of the Nashdba terrane, and granites of the
Cape Ann and Peabody plutons, are ranked high in radon potential. They are associated with
moderate to high radioactivity and the soils developed on these rocks have moderate to high
permeability. Relationships between radon and underlying bedrock in eastern Massachusetts,
particularly in the Merrimack zone and in these areas, are less distinct, probably due to the
influence of glacial deposits that are made up of a mixture of the rock types underlying eastern
Massachusetts and areas to the north. The glacial deposits generally have enhanced permeability
and may have enhanced radon emanation due to the redistribution of rock components, mixing,
and grain-size reduction effects of the glaciers. Volcanic rocks and soils of the Newbury basin are
ranked moderate in radon potential. They are associated with generally low radioactivity, low to
moderate soil permeability, and moderate to high indoor radon levels.
The Esmond-Dedham terrane is ranked moderate or variable overall in radon potential.
This area includes a number of granite plutons and faulted and brittley sheared zones that may
generate high radon levels, as well as mafic metasedimentary and metavolcanic rocks having low to
moderate radon potential. Aeroradioactivity is generally low to moderate with one anomaly
associated with granite of the Rattlesnake Hill Pluton. Soils in this area have low to moderate
permeability. Indoor radon in this area averages between 2 and 4 pCi/L.
Proterozoic to Pennsylvanian sedimentary rocks of the Boston basin have been ranked low
in radon potential. Pennsylvanian sedimentary rocks of the Narragansett basin are associated with
low to moderate radioactivity and low to moderate soil permeability, and have moderate geologic
radon potential. The Norfolk basin is similar to the Narragansett basin and also has moderate
radon potential. Information on soil characteristics and radioactivity is unavailable for the Boston
basin but radioactivity is assumed to be generally low based on the radioactivity of similar rocks
IV-29 Reprinted from USGS Open-File Report 93-292-A
-------
elsewhere in the State. Soil characteristics are highly variable in urban areas due to human
disturbance, and thus are considered to be variable for this assessment. Black shales and
conglomerates in the Boston basin may have locally high radioactivity and may cause locally
elevated indoor radon levels (J. Sinnott, personal communication, 1992).
Sediments of the Coastal Plain are found primarily on Nantucket Island and Martha's
Vineyard. Areas underlain by Cretaceous and Tertiary sediments have low radon potential, but
areas underlain by the Martha's Vineyard and Nantucket moraines have moderate to locally high
radon potential caused by their relatively higher permeability and better drainage characteristics
compared to surrounding areas, and the crystalline rock source component of the moraines. This
is also true of the Buzzard's Bay and Sandwich moraines on Cape Cod (see fig. 7 for locations and
names of moraines). Areas underlain by highly permeable glacial outwash may also generate
locally elevated indoor radon levels if the water table is not too high to preclude soil-gas transport
SUMMARY
For the purpose of this assessment, Massachusetts has been divided into twelve geologic
radon potential areas and each area assigned a Radon Index (RI) and a Confidence Index (CI) score
(Table 2). The RI is a semi-quantitative measure of radon potential based on geology, soils,
radioactivity, architecture, and indoor radon. The CI is a measure of the relative confidence of the
RI assessment based on the quality and quantity of the data used to assess geologic radon potential
(see the Introduction chapter to this regional booklet for more information). The areas referred to
in the radon potential matrix (Table 2) are shown on figure 12.
The Boston basin has low geologic radon potential overall, but a few homes in the area
may have locally elevated indoor radon levels. Areas with moderate or variable radon potential
include the Narragansett basin, Esmond-Dedham terrane, the Newbury basin, and roughly the
western half of Massachusetts. The Coastal Plain, consisting of Martha's Vineyard and
Nantucket, are assigned a variable radon potential, based on the variable geology and drainage
characteristics of the moraines, outwash, and glacial till on the islands. Although only 6 homes in
this area were sampled in the State/EPA Residential Radon Survey, the fact that two of the homes
had screening indoor radon levels exceeding 4 pCi/L, including a 19.5 pCi/L reading, indicates that
further investigations are warranted in this area.
Areas with high radon potential include the central and eastern parts of the State underlain
by granitic rocks and by tills containing granites or other uraniferous rocks, such as graphitic
schists and phyllites, as a major source component Faults and shear zones in many parts of the
State, particularly in the Taconics, on the west side of the Berkshire Mountains, and in the
Merrimack and Esmond-Dedham terranes, have the potential to generate locally high indoor radon.
This is a generalized assessment of the State's geologic radon potential and
there is no substitute for having a home tested. The conclusions about radon
potential presented in this report cannot be applied to individual homes or
building sites. Indoor radon levels, both high and low, can be quite localized,
and within any radon potential area there will likely be areas with higher or lower
radon potential than assigned to the area as a whole. Any local decisions about radon
should up! be made without consulting all available local data. For additional information on radon
and how to test, contact your State radon program or EPA regional office. More detailed
information on state or local geology may be obtained from the state geological survey. Addresses
and phone numbers for these agencies are listed in chapter 1 of this booklet
IV-30 Reprinted from USGS Open-File Report 93-292-A
-------
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TABLE 2. RI and CI scores for geologic radon potential areas of Massachusetts.
Taconics/
Stockbridge Valley
FACTOR RI CI
INDOOR RADON 2 2
RADIOACTIVITY 2 2
GEOLOGY 2 3
SOIL PERM. 2 3
ARCHITECTURE 3
GEE POINTS 0
TOTAL 11 10
MOD HIGH
Gneissic
Domes
FACTOR RI CI
INDOOR RADON 2 2
RADiOAcnvrrY i 2
GEOLOGY 2 3
SOIL PERM. 2 3
ARCHITECTURE 3
GFE POINTS 0
TOTAL 10 10
MOD HIGH
Boston
Basin
FACTOR RI CI
INDOOR RADON 1 3
RADIOACTIVITY 1 1
GEOLOGY 1 3
SOIL PERM. 2 1
ARCHITECTURE 3
GFE POINTS 0
TOTAL 8 8
LOW MOD
RADON INDEX SCORING:
Radon potential category
LOW
MODERATE/VARIABLE
HIGH
Berkshire
Mountains
RI CI
2 2
1 2
2 3
2 3
3
0
10 10
MOD HIGH
Merrimack
Belt
RI CI
3 3
3 2
3 3
2 3
3
0
14 11
HIGH HIGH
Esmond-Dedham
Tenane
RI CI
2 2
2 2
2 3
2 3
3
0
11 10
MOD HIGH
Point range
3-8 points
9-11 points
> 1 1 points
Western Connecticut
Valley Belt
RI CI
2 2
2 2
2 3
2 3
3
0
11 10
Mesozoic
basins
RI CI
2 2
2 2
2 3
2 3
3
0
11 10
MOD HIGH MOD HIGH
Nashoba Terrane & Newbury & other
Cape Ann/Peabody Volcanics
RI CI RI CI
3 2
2 2
3 3
2 3
3
0
13 10
HIGH HIGH
Coastal
Plain
RI CI
3 1
1 1
2 2
2 3
3
0
11 7
2 2
2 2
1 3
2 3
3
0
10 10
MOD HIGH
Narragansett
Basin
RI CI
2 2
2 1
1 3
2 3
3
0
9 9
MOD MOD MOD MOD
Probable screening indoor
radon average for area
<2pCi/L
2-4pCi/L
>4pCi/L
Possible range of points = 3 to 17
CONFIDENCE INDEX SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10 -12 points
Possible range of points = 4 to 12
IV-32 Reprinted from USGS Open-File Report 93-292-A
-------
REFERENCES CITED IN THIS REPORT
AND GENERAL REFERENCES PERTAINING TO RADON IN MASSACHUSETTS
Denny, C.S., 1982, Geomoiphology of New England: U.S. Geological Survey Professional
Paper 1208, 18 p.
Duval, J.S., Jones, W.J., Riggle, F.R., and Pitkin, J.A., 1989, Equivalent uranium map of
conterminous United States: U.S. Geological Survey Open-File Report 89-478,10 p.
Facts on File Publications, 1984, State Maps on File: New England.
Field, M.T., and Truesdell, D.B., 1982, National Uranium Resource Evaluation, Albany
quadrangle, Massachusetts, New York, Connecticut, Vermont, and New Hampshire:
Bendix Field Engineering Corporation, prepared for the U.S. Department of Energy, report
PGJ/F-104(82).
Grauch, R.I., and Zarinski, K., 1976, Generalized descriptions of uranium-bearing veins,
pegmatites, and disseminations in non-sedimentary rocks, eastern United States: U.S.
Geological Survey Open-File Report 76-582,114 p.
Gundersen, L.C.S., 1991, Radon in sheared metamorphic and igneous rocks, in Gundersen,
L.C.S., and Wanty, R.B., eds, Field studies of radon in rocks, soils, and water: U.S.
Geological Survey Bulletin 1971, p. 39-50.
Hall, F.R., Boudette, E.L., and Olszewski, W.J., Jr., 1987, Geologic controls and radon
occurrence in New England, in Graves, Barbara, ed., Radon in ground water: Chelsea,
Michigan: Lewis Publishers, p. 15-30.
National Oceanic and Atmospheric Administration, 1974, Climates of the States, Volume 1—
eastern states: Port Washington, NY: Water Information Center, Inc.
Olszewski, W.J., Jr., and Boudette, E.L., 1986, Generalized bedrock geologic map of New
England with emphasis on uranium endowment and radon production: EPA open-file map.
Page, L.R., editor, 1976, Contributions to the stratigraphy of New England: Geological Society
of America Memoir 148,445 p.
Rankin, D.W., Drake, A.A., Jr., Glover, L., IE, Goldsmith, R., Hall, L.M., Murray, D.P.,
Ratcliffe, N.M., Read, J.F., Seacor, D.T., Jr., and Stanley, R.S., 1989, Pre-orogenic
terranes, in Hatcher, R.D., Jr., Thomas, W.A., and Viele, G.W., eds., The Appalachian-
Ouachita Orogen in the United States: Geological Society of America, The Geology of
North America, v. F-2, p. 7-100.
Richmond, G.M., and Fullerton, D.S., eds., 1991, Quaternary geologic map of the Boston 4° x 6°
quadrangle, United States and Canada: U.S. Geological Survey Miscellaneous
Investigations Map 1-1420, sheet NK-19, scale 1:1,000,000.
IV-33 Reprinted from USGS Open-File Report 93-292-A
-------
Robinson, G.R., Jr., and Sears, C.M., 1988, Inventory of metal mines and occurrences
associated with the early Mesozoic basins of the eastern United States - Summary tables: in
AJ. Froelich and G.R. Robinson, Jr. eds., Studies of the early Mesozoic basins of the
eastern United States, U.S. Geological Survey Bulletin 1776, p. 265-303.
Stone, B.D., 1982, The Massachusetts state surficial geologic map, in Farquhar, O.C., ed.,
Geotechnology in Massachusetts, conference proceedings: Amherst, Mass., University of
Massachusetts, p. 11-27.
Stone, B.D., and Borns, H.W., Jr., 1986, Pleistocene glacial and interglacial stratigraphy of New
England, Long Island, and adjacent Georges Bank and Gulf of Maine, in Sibrava, V.,
Bowen, D.Q., and Richmond, G.M., eds., Quaternary Glaciations in the Northern
Hemisphere: Quaternary Science Reviews, v. 5, p. 39-52.
U.S. Department of Agriculture, 1978, Massachusetts Soils-Their Classification, Family Groups,
Parent Material and Drainage relationships: US Soil Conservation Service, 48 p.
U.S. Department of Agriculture, 1989, Generalized soils map of Massachusetts: Soil
Conservation Service, scale approximately 1:1,170,000.
Zen, E-an, editor, 1983, Bedrock geologic map of Massachusetts: U.S. Geological Survey, scale
1:250,000, 3 sheets.
Zoino, W.S., and Campagna, N.A., Jr., 1982, Engineering behavior of the Taunton River clays,
in Farquhar, O.C., ed., Geotechnology in Massachusetts, conference proceedings:
Amherst, Mass., University of Massachusetts, p. 183-192.
ZoUinger, R.C., Blauvclt, R.P., and Chew, R.T., HI, 1982, National Uranium Resource
Evaluation, Providence quadrangle, Connecticut, Rhode Island, and Massachusetts:
Bendix Field Engineering Corporation, prepared for the U.S. Department of Energy, report
PGJ/F-101(82).
IV-34 Reprinted from USGS Open-File Report 93-292-A
-------
EPA's Map of Radon Zones
The USGS' Geologic Radon Province Map is the technical foundation for EPA's Map
of Radon Zones. The Geologic Radon Province Map defines the radon potential for
approximately 360 geologic provinces. EPA has adapted this information to fit a county
boundary map in order to produce the Map of Radon Zones.
The Map of Radon Zones is based on the same range of predicted screening levels of
indoor radon as USGS1 Geologic Radon Province Map. EPA defines the three zones as
follows: Zone One areas have an average predicted indoor radon screening potential greater
than 4 pCi/L. Zone Two areas are predicted to have an average indoor radon screening
potential between 2 pCi/L and 4 pCi/L. Zone Three areas are predicted to have an average
indoor radon screening potential less than 2 pCi/L.
Since the geologic province boundaries cross state and county boundaries, a strict
translation of counties from the Geologic Radon Province Map to the Map of Radon Zones
was not possible. For counties that have variable radon potential (i.e., are located in two or
more provinces of different rankings), the counties were assigned to a zone based on the
predicted radon potential of the province in which most of its area lies. (See Part I for more
details.)
MASSACHUSETTS MAP OF RADON ZONES
The Massachusetts Map of Radon Zones and its supporting documentation (Part IV of
this report) have received extensive review by Massachusetts geologists and radon program
experts. The map for Massachusetts generally reflects current State knowledge about radon
for its counties. Some States have been able to conduct radon investigations in areas smaller
than geologic provinces and counties, so it is important to consult locally available data.
Although the information provided in Part IV of this report — the State chapter entitled
"Preliminary Geologic Radon Potential Assessment of Massachusetts" — may appear to be
quite specific, it cannot be applied to determine the radon levels of a neighborhood, housing
tract, individual house, etc. THE ONLY WAY TO DETERMINE IF A HOUSE HAS
ELEVATED INDOOR RADON IS TO TEST. Contact the Region 1 EPA office or the
Massachusetts radon program for information on testing and fixing homes. Telephone
numbers and addresses can be found in Part II of this report.
V-l
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