This geographic information system (GIS) data layer shows the
dominant lithology and geochemical, termed lithogeochemical,
character of near-surface bedrock in the New England region
covering the states of Connecticut, Maine, Massachusetts, New
Hampshire, Rhode Island, and Vermont. The bedrock units in the
map are generalized into groups based on their lithological
composition and, for granites, geochemistry. Geologic provinces
are defined as time-stratigraphic groups that share common features
of age of formation, geologic setting, tectonic history, and lithology.
This data set incorporates data from digital maps of two NAWQA
study areas, the New England Coastal Basin (NECB) and the
Connecticut, Housatonic, and Thames River Basins (CONN) areas and
extends data to cover the states of Connecticut, Maine,
Massachusetts, New Hampshire, Rhode Island, and Vermont.
The result is a regional dataset for the lithogeochemical
characterization of New England (the layer named NE_LITH).
Polygons in the final coverage are attributed according
to state, drainage area, geologic province, general rock type,
lithogeochemical characteristics, and specific bedrock map unit.
This geologic characterization provides a framework to interpret
regional geochemistry and habitat characteristics in relation to
bedrock lithology and geologic provinces that share common
features. The lithogeochemical data layer combines and extends
data previously compiled for the U.S. Geological Survey National
Water Quality Assessment Program (NAWQA) study areas of the New
England Coastal Basin (NECB), and the Connecticut, Housatonic,
and Thames River Basins (CONN). The coverage provides digital
geologic information that may be applied to the analysis of
water-quality characteristics of surface water and shallow ground
water, and soil and stream sediment characteristics based on
The geologic characterization provided in this classification is
intended to portray significant bedrock geologic features that
influence stream sediment and soil chemistry and water quality.
"Near-surface bedrock" in this report refers to lithified
materials covered by no more than about 60 feet of overlying
unconsolidated surficial materials. The thickness of Quaternary
sediments overlying bedrock is generally less than 60 feet in
the New England states (Soller, 1993).
The bedrock units shown on the source maps were grouped and
generalized for this compilation. Consequently this map
will show fewer geologic units and less detail than the
state geologic maps from which the information was drawn.
A few areas have been modified from those shown on the state
maps, for example, additional units portrayed by Smoot (1991) are
shown in the Hartford Basin area of Connecticut and Massachusetts
and mismatched contacts have been adjusted along state borders.
Based on the geologic map compilation scales, mismatches of some
unit contacts across state boundaries, and the positioneal
uncertainty of the source digital files relative to the published
geologic maps, the spatial accuracy of this compilation is
estimated as 1.5 km.
To the degree that surficial materials are related to their
proximal bedrock source, the variations in bedrock geology also
provide guidelines to the expected variation in the properties
and chemistry of surficial materials and surface waters. In
glaciated areas, such as New England, the mineralogy of tills and
some stratified drift is related to adjacent bedrock units, and
bedrock geology has been used to help define their chemical
character (Bailey and Hornbeck, 1992). A lithogeochemical
framework similar to that provided in this report has been used
to define correlations between groundwater chemistry and bedrock
geology (Grady and Mullaney, 1988; Ayotte and others, 1999).
Groundwater chemistry for alkalinity, pH, Ca, Mg, Na, silica, and
radon in surficial aquifers sampled from wells up to 60 feet in
depth in surficial aquifers have been shown to correlate with
groups of lithology of the underlying bedrock (Grady and
Mullaney, 1988). Groundwater chemistry for pH, iron, manganese,
and arsenic in fractured crystalline bedrock aquifers sampled
from wells up to 500 feet in depth differ by bedrock lithology
groups (Ayotte and others, 1999; Ayotte and others, 2003).
The lithogeochemical characterization in these data have been
put to use analyzing water-quality characteristics in studies
by Grady and Mullaney (1998) and Ayotte and others (2003).
The lithogeochemical classification scheme for the New England
Lithology data set was first developed as part of the USGS's
study of the CONN area (Robinson and others, 1999). The
classification scheme is based on geochemical principles,
previous studies of the relations among water-quality and
ecosystem characteristics and rock type, and regional geology
(Robinson, 1997 and references cited within). The classification
scheme and data set are intended to provide a general, flexible
framework to portray the lithologic character of mapped bedrock
units in New England in relation to regional geochemical and
The data set is a lithologic map that has been coded to reflect
the potential influence of bedrock geology on water quality and
sediment chemistry. Information on the map unit identities
portrayed on the source bedrock geologic maps for each state
are retained in this digital dataset.
The bedrock units in New England have been mapped by time-
stratigraphic and other geologic criteria that may not be
directly relevant to variation in regional geochemistry and water
quality. Bedrock units depicted on the state geologic maps are
inconsistent across state boundaries in some areas. Thus, a
regional coding scheme was developed to reclassify the geologic
map units according to mineralogical and chemical characteristics
that are relevant for analysis of regional variation in geochemistry
To provide a framework for geochemical investigations, the
bedrock units were classified according to the chemical
composition (based upon the geologic maps used in the creation of
this data set) and the relative susceptibility to
weathering of their constituent minerals. Although weathering
rates may vary, the relative stability of different minerals
during weathering in moist climates is generally consistent
(Robinson, 1997). However, the degree to which a rock weathers
reflects the proportions of its constituent mineral as well as
many other factors such as degree of induration and relative
amount of mineral surfaces exposed to water through primary and
secondary porosity (Robinson, 1997 and references cited within).
Thus, although largely based on the relative stability of rock
constituent minerals, the classification scheme to group bedrock
units according to effects on soil and sediment chemistry and
water quality is more complex than mineral-stability sequences.
Most common rock-forming minerals are only sparingly soluble, so
small amounts of highly reactive minerals can have large
effects on water quality (Robinson, 1997; Grady and Mullaney,
1998). For example, rocks containing significant amounts of
carbonate minerals are more rapidly weathered and tend to produce
higher solute concentrations in natural waters than many other
rock types. In contrast, rock types such as granite, schist and
quartzite are rich in quartz, muscovite, and alkali-feldspars;
these minerals tend to produce low solute concentrations because
they react to a lesser degree and at slower rates than other mineral
types in humid temperate climates (Robinson, 1997). Further
description of the lithogeochemical classification scheme and
the expected water-quality and ecosystem characteristics associated
with each lithogeochemical unit is explained in Robinson (1997).
The lithogeochemical classification scheme used in this data set
incorporates mineralogical information derived from published
descriptions of the bedrock geology map units with other
information on geologic features, such as metamorphic grade and
geologic setting. The attributes of lithology code ("Litho_code")
and modifier code ("Lith_mod") are used to express this
lithogeochemical coding of bedrock units. Thirty-seven
lithogeochemical units (combinations of lithology and modifier
codes) are defined for the New England study region based on the
mineral and textural properties of the bedrock unit's constituent
minerals, presence of carbonate and sulfide minerals,
depositional setting (such as restricted deposition within fault
bounded sedimentary basins of Mississipian or younger age), and
for some of the granitic units, mineralogy and magma chemistry.
The classification scheme used descriptions from state and
regional geologic maps (Doll and others, 1961; Osberg and others,
1985; Lyons and others, 1997; Zen and others, 1983; Hermes and
others, 1994; and Rogers, 1985; Smoot, 1991). For Rhode Island
and Maine, source materials of the state geologic maps were
available as digital data layers (Osberg and others, 1985, Maine;
Hermes and others, 1994, 1:100,000 scale, Rhode Island).
Information from these sources included descriptions of the
lithology, mineralogy, and weathering characteristics of the
bedrock units. For example, "rusty-weathering" serves as an
indicator of sulfidic-bearing bedrock units (Robinson, 1997).
Carbonate and sulfide minerals predominate in the classification
scheme because these highly reactive minerals have a
disproportionately large effect on water chemistry compared to
other minerals commonly found in the rocks of this region
(Robinson, 1997). In the Maine data set, information about
metamorphic grade was also used to classify bedrock units. A
digital data layer of generalized regional metamorphic zones
(Guidotti, 1985, shown in Osberg and others, 1985, was obtained
from the Maine Geological Survey. This layer was intersected
with the digital bedrock geology to determine the regional
metamorphic grade of each polygon in the bedrock geology data
layer. Polygons lying within two metamorphic zones were split at
the metamorphic-zone boundary. Metamorphic grade and geochemical
composition of the protolith (pre-metamorphism source rock) were
used to classify polygons into lithogeochemical units. For
example, bedrock units with protoliths of "limestone and (or)
dolostone" were classified as "limestone, dolomite, and
carbonate-rich clastic sediments" (lithogeochemical unit "11u")
in areas of little or no regional metamorphism and as "marble,
may include some calc-silicate rock" (lithogeochemical unit
"12u") in areas of greenschist facies or high-grade metamorphism.
Ayotte, J.P., Nielsen, M.G., Robinson, G.R., Jr., Moore, R,B., 1999, Relation of arsenic, iron, and manganese in ground water to aquifer type, bedrock lithogeochemistry, and land use in the New England Coastal Basins, U. S. Geological Survey Water-Resources Investigative Report 99-4162, 61 p.
Ayotte, J.D., Montgomery, D.L., Flanagan, S.M., and Robinson, K.W., 2003, Arsenic in ground water in eastern New England: Occurrence, controls, and human health implications: Environmental Science and Technology, v. 37, no.10, p.2075-2083.
Bailey, S.W. and Hornbeck, J.W., 1992, Lithologic composition and rock weathering potential of forested, glacial-till soils, Research paper NE-662, Radnor PA: United States Department of Agriculture, Forest Service, Northeastern Forest Experimental Station, 7 p.
Doll, C.G., Cady, W.M., and Thompson, J.B., Jr., and Billings, M.P., eds. and compilers, 1961, Centennial Geology Map of Vermont: Montpelier, VT, U.S. Geological Survey, 1:250,000, 1 sheet. (transverse mercator projection, based on best available information).
Grady, S.J. and Mullaney, J.R., 1998, Natural and human factors affecting shallow water quality in surficial aquifers in the Connecticut, Housatonic, and Thames River Basins: U.S. Geological Survey Water-Resources Investigations Report 98-4042, 81 p.
Guidotti, C.V., 1985, Generalized map of regional metamorphic zones:in Osberg, P.H., and others: Augusta, Maine, Maine Geological Survey, 1 map sheet, 1:1,600,000.
Hermes, O.D., Gromet, L.P., Murray, D.P., 1994, Bedrock geologic map of Rhode Island: Kingston, R.I., Office of the Rhode Island State Geologist, Rhode Island Map Series No 1, 1 map sheet, 1:100,000.
Lyons, J.B., Bothner, W.A., Moench, R.H., and Thompson, J.B., Jr., 1997, Bedrock geologic map of New Hampshire: Reston, Va., U.S. Geological Survey Special Map, 2 map sheets, 1:250,000.
McHone, J.G., and Butler, J.R. 1984. Mesozoic igneous provinces of New England and the opening of the North Atlantic Ocean: Geological Society of America Bulletin v.95, p. 757-765.
Osberg, P.H., Hussey, A.M. II, and Boone, G.M., 1985, Bedrock geologic map of Maine: Augusta, Maine, Maine Geological Survey, 1 map sheet, 1:500,000.
Robinson, G.R., Jr., 1997, Portraying chemical properties of bedrock for water quality and ecosystem analysis: an approach for the New England Region: U.S. Geological Survey Open-File Report 97-154, 17 p.
Robinson, G.R., Jr., Peper, J.D., Steeves, P.A., and DeSimone, L.A., 1999, Lithogeochemical character of near-surface bedrock in the Connecticut, Housatonic, and Thames River Basins: U.S. Geological Survey, Water-Resources Investigations Report 99-4000 digital.
Robinson, G.R., Jr., Ayotte, J.P., Montgomery, D.C., and DeSimone, L.A. 2002, Lithogeochemical Character of Near-Surface Bedrock in the New England Coastal Basins: U.S. Geological Survey Open-File Report, 02-00 digital.
Rogers, John (compiler), 1985, Bedrock geological map of Connecticut: Connecticut Geologic and Natural History Survey, Natural Resource Atlas Map Series, 2 map sheets, 1:125,000.
Soller, D.R., 1993, Map showing the thickness and character of Quaternary sediments in the glaciated United States east of the Rocky Mountains - Northeastern states, the Great Lakes, and parts of southern Ontario and the Atlantic offshore area (east of 80o 31' west longitude): U.S. Geological Survey Miscellaneous Invistigations Series Map I-1970-A.
Smoot, J.P., 1991, Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America: Paleogeography, Paleoclimatology, Paleoecology, v. 84, p. 369-423.
Zen, E-an, Goldsmith, G.R., Ratcliffe, N.L., Robinson, P., and Stanley, R.S., 1983, Bedrock geologic map of Massachusetts: U.S. Geological Survey, Monograph Series, 3 map sheets, 1:250,000.
Individuals involved in the creation of the final New England Lithology (NE_LITH), CONN, and NECB coverages are listed as follows:
New England Lithology (final Coverage NE_LITH):
Gilpin R. Robinson, Jr.: U.S. Geological Survey, Reston, Va.
Primary developer of the classification scheme. Preparation of source materials and information for combining the coverages into a general representation of New England Lithology.
Katherine E. Kapo: U.S. Geological Survey, Reston, Virginia. Assisted in editing the coverage linework and attributes, creation of the final "New England Lithology" version, and compilation of the final metadata.
Joseph D. Ayotte: U.S. Geological Survey, Pembroke, New Hampshire. New England Coastal Basin NAWQA ground-water specialist; reviewed the construction of the combined coverage.
Laura Hayes: U.S. Geological Survey, Pembroke, New Hampshire. Reviewed the finalized coverage and metadata and provided corrections for the metadata and attribute table.
Gilpin R. Robinson, Jr: Preparation of source materials and compilation of lithogeochemical units for Connecticut and Massachusetts regions; primary development of lithogeochemical classification scheme.
John D. Peper: Preparation of source materials and compilation
of lithogeochemical units for Vermont and New Hampshire regions;
additional development of lithogeochemical classification scheme.
Peter A. Steeves: Construction, revision, quality-assurance, and
documentation of the digital data layer and publication of the data layer as a digital map product.
Leslie A. DeSimone: Quality assurance, revision, and documentation
of the data layer and publication of the data layer as a digital
Stephen P. Garabedian: Connecticut River NAWQA chief; coordinating personnel and funding, planning, oversight, and review of the data layer
Stephen J. Grady: Connecticut River NAWQA ground-water specialist;
primary user of the resulting data; planning and definition of
water quality issues of the NAWQA study unit for use in development of the data layer and oversight of the initial data-layer construction phases.
Robert Sava, Jr: Digitizing and coding contributions in NH, MA, and VT
Shanon Wappel: Digitizing and coding contributions in CT
Gilpin R. Robinson, Jr.: U.S. Geological Survey, Reston, VA.
Primary developer of the classification scheme. Preparation of source materials and compilation of lithogeochemical units for Maine, Massachusetts, and Rhode Island.
John D. Peper: U.S. Geological Survey, Reston, VA. Preparation of source materials and compilation of lithogeochemical units for New Hampshire; secondary developer of the lithogeochemical classification scheme.
John C. Rader: U.S. Geological Survey, Marlboro, Massachusetts. Construction, revision, quality-assurance, and documentation of the original digital data layer.
Keith W. Robinson: U.S. Geological Survey, Pembroke, New Hampshire. New England Coastal Basin NAWQA Chief; Coordination of personnel and funding, planning, oversight, and review of the data layer.
Joseph D. Ayotte: U.S. Geological Survey, Pembroke, New Hampshire. New England Coastal Basin NAWQA ground-water specialist; primary user of the resulting data; planning and definition of the water-quality issues of the NAWQA study unit for use in development of the data layer and oversight of the data layer construction phases.
Leslie A. DeSimone: U.S. Geological Survey, Marlboro, Massachusetts. Technical reviewer of original digital data layer.
Walt Bawiec: U.S. Geological Survey, Reston, Virginia. Colleague reviewer who performed technical reviews of the completed digital data set and metadata document.
Curtis Price: U.S. Geological Survey, Rapid City, South Dakota. Colleague reviewer who performed technical reviews of the completed digital data set and metadata document.
Sarah M. Flanagan: U.S. Geological Survey, Pembroke, New Hampshire. Edited the coverage and assisted in compilation and editing the metadata.
Laura Hayes: U.S. Geological Survey, Pembroke, New Hampshire. Created plots of the CONN lithogeochemical coverage and the NECB lithogeochemical coverage so that consistency along the study-unit border could be checked. Corrected the shift in the Massachusetts portion of the coverage. Assisted in compilation and editing of the NECB metadata.