Connecticut Bedrock Geology is a 1:50,000-scale, polygon and line feature-based layer describing the solid material that underlies the soil or other unconsolidated material of the earth for Connecticut. Bedrock geologic formations are described as polygons in terms of formation name (incorporating geologic age), rock type, and tectonic terrane association. Tectonic forces are responsible for the present day geologic configuration of the continents. Resulting terranes are regionally fault bounded rocks of a similar tectonic history. Each terrane is named after its plate tectonics ancestry. Geologic lines include contacts, faults, and terrane boundaries. Terrane boundaries are named for the faults involved. The geologic contacts and faults are delineated and classified by type. Polygon feature attribute information is comprised of codes to identify individual bedrock geologic units, their formation name, description and size. Line feature attributes identify, name and describe bedrock contacts, faults and terrane boundaries between these bedrock geologic units. Data is compiled at 1:50,000 scale and is not updated. A complete description of the bedrock mapping units with mineralogical descriptions and a brief history of Connecticut geology are included in the Supplemental Information Section for reference. The data source is from John Rodgers, Bedrock Geological Map of Connecticut, 1985 (Connecticut Geological and Natural History Survey, DEP, in cooperation with the U.S. Geological Survey, 2 sheets, 1:125,000 publication scale). This datalayer was digitized from a set of 1:50,000 scale regional sheets used for compilation of the 1:125,000 scale published map. The regional sheets were compiled to a common publication base from 1:24,000 scale mylar originals prepared from geologic quadrangle mapping and other interpretations. A list of sources is included later in this document. Additional historical information is in the map notes section. For a stratigraphic correlation of bedrock units, major regional and statewide tectonic structures, and cross sectional views of the State's geology, please refer to the 1:125,000 scale Bedrock Geological Map of Connecticut. The Bedrock Geological Map of Connecticut is available for purchase at the DEP Store.
Connecticut Bedrock Geology is 1:50,000-scale data suitable for for geologic and environmental mapping and analysis purposes. Not intended for maps printed at map scales greater or more detailed than 1:50,000 scale (1 inch = 4,167 feet.). Not intended for site specific spatial analysis purposes.
Brief Bedrock Geologic History of Connecticut - Geologic regions (terranes) on this map reflect the role of plate tectonics in the geologic history of Connecticut. Each terrane is named after its plate tectonics history. From 450 to 250 million years ago, during the Paleozoic Era, several crustal plates, including Africa and Eurasia, sequentially collided with the Proto-North American plate in a series of four mountain building events that ultimately created the Appalachian Mountains and the supercontinent Pangea. During these collisions, Avalonia, a small continent believed to have been a part of the African plate, was thrust against the continent of Proto-North America, closing and collapsing the intervening Iapetos Ocean. The collisions deformed and metamorphosed both the continental rocks of Proto-North America and Avalonia and the oceanic rocks and sediments of the Iapetos Ocean floor. This process created the schists, gneisses and granites exposed today in eastern and western Connecticut. Features of these metamorphic and igneous rocks show this complex geologic history, confirming the continental and oceanic origins and the processes of plate tectonics. Shortly after the collision ended, at the beginning of the Mesozoic Era or about 235 million years ago, plate tectonic processes reversed. Pangea began to break apart, initiating the opening of the Atlantic Ocean and leaving Avalonia welded to North America. In the early stages of this breakup, rift basins formed along and on both sides of the zone where the Atlantic Ocean finally opened. The Newark terrane in central Connecticut is the eroded remnant of one of these rift basins. It contains 200 million year old sedimentary rocks (brownstone) and lava flows and intrusions of basalt (trap rock). Geologic Ages - Below is a list of Geologic ages represented in Connecticut rocks. The first letter represents the geologic age, which is the first portion of each bedrock unit code. AGE CODE, GEOLOGIC AGE, DATE (mya = million years ago) J, Jurassic, 140 - 205 mya, Youngest rocks in Connecticut TR, Triassic, 205 - 240 mya P, Permian, 240 - 290 mya Carboniferous rocks (Pennsylvanian and Mississippian) are not present in Connecticut 290 - 360 mya D, Devonian, 360 - 410 mya S, Silurian, 410 - 435 mya O, Ordovician, 435 - 500 mya C, Cambrian, 500 - 570 mya Z, Proterozoic (PreCambrian), 570 - 800 mya Y, Proterozoic (PreCambrian), 800 - 1700 mya, 'Y' Proterozoic are the oldest rocks in Connecticut (~ 1100 mya) Simplified descriptions are given for rock terms used above. Descriptions include general and distinguishing characteristics of rocks as they commonly occur in Connecticut. Alaskite gneiss: Light-colored, fine-to coarse-grained, banded metamorphic rock of granite-like composition with potassium feldspar as the major feldspar, and only a few percent dark minerals. Amphibolite: Dark-colored, fine-to coarse-grained, massive to poorly layered metamorphic rock containing amphibole and plagioclase with little or no quartz. Arkose: Red to brown, medium-to coarse-grained, sandstone-like, sedimentary rock containing quartz, feldspar, and rock fragments. It is the most common sedimentary rock of the Central Lowlands; locally known as brownstone. Brownstone was quarried for use as building stone. Basalt: Dark-gray, orange-to brown-weathering, fine-grained, extrusive igneous rock, commonly fractured (jointed), containing calcium-plagioclase and pyroxene; occurs as lava flows in the Central Lowlands; locally known as traprock. Basalt is extensively quarried for use as crushed stone. Diorite: Light and dark (salt and pepper), medium- to coarse-grained intrusive igneous rock, commonly massive-appearing, generally lacking layering or banding; composed primarily of plagioclase feldspar, quartz and dark minerals. Dioritic gneiss: Light and dark, medium- to coarse-grained, compositionally banded metamorphic rock of dioritic composition. Dolerite: Dark-gray, orange- to brown- to gray-weathering, medium- to fine-grained intrusive igneous rock, commonly fractured into well-developed columnar joints, compositionally similar to basalt; occurs as dikes and sills in both the lowlands and uplands; locally known as traprock. Dolerite is quarried for use as crushed stone. Gabbro: Dark, medium- to coarse-grained, intrusive mafic igneous rock, commonly massive-appearing, generally lacking layering or banding; composed primarily of clinopyroxene and plagioclase; often altered. Gneiss: Light and dark, medium- to coarse-grained metamorphic rock characterized by compositional banding of light and dark minerals, typically composed of quartz, feldspar, and various amounts of dark minerals; occurs with a variety of compositions and is a characteristic rock of the uplands. Granite: Light-colored, medium- to very coarse-grained intrusive igneous rock, commonly massive-appearing, lacking layering or banding; composed of quartz, feldspar, and commonly muscovite mica with minor amounts of dark minerals. Granite and granitic gneiss were quarried for use as dimension stone. Very limited quarrying continues. Granitic gneiss: Light-colored, medium- to coarse-grained, compositionally banded metamorphic rock of granitic composition. Quarried for use as dimension stone (see granite). Granofels: Light to dark, medium- to coarse-grained, massive to poorly layered metamorphic rock composed primarily of quartz and feldspar; lacking the compositional banding of a gneiss. Greenschist: Light to dark, green, medium- to coarse-grained schist; typically consisting of the green minerals: chlorite, epidote, or actinolite. Greenstone: Green to gray-green, fine- to coarse-grained, massive to poorly layered metamorphic rock composed of chlorite, hornblende, and epidote. Lamprophyre: Dark-colored, medium-grained intrusive igneous rock occurring as dikes; composed of biotite, hornblende, pyroxene, and feldspars or feldspathoids. Mafic rock: Dark-colored rock consisting of one or more dark (iron and magnesian) minerals as its major constituent. Marble: Conspicuously white, or gray, medium- to coarse-grained, massive to layered metamorphic rock composed of calcite and/or dolomite. It is a metamorphosed limestone and underlies several major valleys in the Western Uplands. Marble is quarried for use as agricultural lime and for industrial uses. Mylonite: Compact rock with streaky or banded structure, found in fault zones, and produced by extreme crushing and shearing of rocks during movement of a fault. It is particularly well developed along the Lake Char - Honey Hill fault zones of the Eastern Uplands. Norite: Dark-colored, medium- to coarse-grained intrusive mafic igneous rock commonly massive-appearing, lacking layering or banding, composed of plagioclase and orthopyroxene; often altered. Pegmatite: Light-colored, very coarse-grained intrusive igneous rock, composed of feldspar, quartz, and micas; frequently can be seen in highway roadcuts as light-colored parallel and cross cutting veins and lenses in the metamorphic rock of the uplands; occasionally is a host for gem minerals. Pegmatite is a common and economically important rock type in Connecticut. It occurs in bodies too small to show on a state-scale geologic map. The Branchville area of western Connecticut and the Middletown area of eastern Connecticut have pegmatites of particular significance. Phyllite: Silvery, gray to dark-gray, fine- to very fine-grained, schist-like metamorphic rock. Porphyry: Light-colored, fine-grained intrusive igneous rock with some conspicuously large crystals of quartz, feldspar, or biotite. Quartzite: Light-colored to gray, massive to layered, medium-grained metamorphic rock. Very hard and resistant; a metamorphosed sandstone composed primarily of quartz. Shale: Red to brown, locally gray to green, extremely fine-grained, strongly layered sedimentary rock composed of clay minerals; occurs in the Central Lowlands. Schist: Light, silvery to dark, coarse- to very coarse-grained, strongly to very strongly layered metamorphic rock whose layering is typically defined by parallel alignment of micas. Primarily composed of mica, quartz, and feldspar; occasionally spotted with conspicuous garnets. Schistose marble: Light-colored, fine- to coarse-grained, marble interlayered with schist or phyllite. Syenite: Medium-gray, fine- to coarse-grained intrusive igneous rock, commonly massive-appearing, generally lacking layering or banding, composed primarily of potassium feldspar with minor dark minerals but little quartz. Ultramafic rock: Dark-colored, medium- to coarse-grained intrusive igneous rock, commonly massive-appearing, generally lacking layering or banding and originally composed chiefly of olivine and pyroxene; commonly altered to serpentine and talc. Occurs as small intrusions in the uplands.
publication date
No restrictions or legal prerequisites for using the data. The data is suitable for use at appropriate scale, and is not intended for maps printed at scales greater or more detailed than 1:50,000 scale (1 inch = 4,167 feet). Although this data set has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection as to the accuracy of the data and or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut, Department of Environmental Protection in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data is distributed to the user, modifications made to the data by the user should be noted in the metadata. When printing this data on a map or using it in a software application, analysis, or report, please acknowledge the State of Connecticut, Department of Environmental Protection as the source for this information. For example, include the following data source description when printing this layer on a map: Geology - From the Bedrock Geology layer, compiled and published by CT DEP and USGS. Source map scale is 1:50,000.
79 Elm Street
The compiler, John Rodgers, wishes to acknowledge his great debt to all the many geologists who have worked on the bedrock geology of the State over the years. But perhaps his deepest indebtedness is to the Report on the Geology of the State of Connecticut and the accompanying Geological Map of Connecticut published in 1842 by James Gates Percival. Connecticut had far less forest (or urban sprawl) and far more open country (fields and pastures) in Percival's day than ours, so that he almost certainly saw many more outcrops than anyone since; he was, moreover, an extraordinarily accurate observer with a retentive memory, so that his tracing of rock units from one part of the state to another is thoroughly reliable. His map is almost certainly more accurate than either subsequent geological map of the State (Gregory and Robinson 1906; Rodgers, Cameron, Gates, and Ross, 1956), but it is hardly usable because the map units are designated only by letters, numbers, Greek letters, and symbols keyed to the difficulty readable text. In more than one place, the compiler chose among diverse interpretations on the basis of Percival's mapping. The compiler must further point out that, in order to produce a map consistent with itself and also with the Bedrock Geologic Map of Massachusetts (Zen and others, 1983), which was being compiled at the same time, he felt it necessary to depart significantly in some places from the source maps cited, as by using different units, correlating units differently, and occasionally introducing or suppressing contacts or faults. In those places of course the authors of the source materials are not responsible for the interpretation shown on this map within the quadrangles for which they are cited. In some cases, indeed, they strongly disagree with the compiler's reinterpretation, for which he must take the entire responsibility. This compilation was begun at the suggestion of Joe Webb Peoples, then State Geologist. His persistence and encouragement helped carry the map through draft and redraft. Sidney Quarrier coordinated much of the work and brought the map to print two times; first a preliminary version at the scale of 1:250,000 in 1982, and now the final colored map at 1:125,000. He and his coworkers Robert Altamura and Margaret Thomas designed the format and material for this map. Nancy Davis, Craigh Dietsch, and Nat Gibbons drafted the original compilation.
The Bedrock Geology layer retains the feature types and information identified on the 1:50,000-scale compilation sheets for the Bedrock Geological Map of Connecticut, Rodgers, 1985. All attributes have valid values. Values are within defined domains. The accuracy test for the UNIT attribute values was conducted by comparing the Geologic Map Unit information presented on the source mylar overlays with 1:50,000-scale check plots or interactive displays of the digital data on a computer graphic system. These check plot maps and computer displays depicted and labeled the Bedrock Geology polygon features in different colors and line-fill patterns based on UNIT attribute values for comparison with the original data source. FORMATION is the English language equivalent of (decodes) the UNIT field values. The FORMATION, DESCRIPTION, TERR_COD, TERRANE, LITH01, LITHO2, LITHO3, LITHO4, LITHO5, AGE, and TIME polygon attributes are all based on and key off the UNIT attribute. These related attributes were populated by joining to lookup data tables using the UNIT as the relate key field instead of manually entering these values for each polygon feature. These lookup data tables contain records that account for and describe the unique occurrences of UNIT. The AREA_SQMI (area in square miles) and ACREAGE (area in acres) field were automatically calculated for each polygon feature based on computer generated feature area in square feet. For line features, the CLASS_COD attribute that distinguishes faults from contacts, for example, was manually entered for each feature. DEFINITION is the English language equivalent of (decodes) the CLASS_COD field values. The DEFINITION, AV_LEGEND, TERRB_COD, and TERR_BNDRY line attributes are all based on and key off the CLASS_COD attribute. These related line attributes were populated by joining to lookup data tables using the CLASS_COD as the relate key field instead of manually attributing these values for each line feature.
Polygon features conform to the following topological rules. Polygons are single part. There are no duplicate polygons. Polygons do not self overlap. Polygons do not overlap other polygons. Lines are single part. Line features conform to the following topological rules. There are no duplicate lines. Lines do not self overlap. Lines do not overlap other lines. Lines intersect only at nodes, and nodes anchor the ends of all lines. Lines do not overshoot or undershoot other lines they are supposed to meet and intersect. The tests of logical consistency were performed by the State of Connecticut using ESRI ArcInfo software to maintain feature topology in ArcInfo coverage format. The data is topologically clean. The ArcInfo Clean function was repeatedly used following edits to verify topology and enforce a minimum distance between vertices of 4 feet (fuzzy tolerance) and a minimum allowed overshoot length of 10 feet (dangle length).
The data completely reflects the content of the data sources, which is a set of 1:50,000 scale regional map (mylar) sheets used for compilation of the Bedrock Geological Map of Connecticut, 1985 (Connecticut Geological and Natural History Survey, DEP, in cooperation with the U.S. Geological Survey, 2 sheets, 1:125,000 publication scale). The Bedrock Geology datalayer was digitized from this set of 1:50,000 scale mylar compilation sheets that mapped the Bedrock Geology for the State of Connecticut. This data is not updated.
The horizontal positional accuracy of this data is unknown.
SOURCE MATERIALS used in compiling the Bedrock Geological Map of Connecticut, 1985, listed by 7.5' quadrangle. Amenia - Geol. Map of N.Y., NYSMMC 15, 1970 Ansonia - Fritts, GQ 426, 1965 Ashaway - Feininger, GQ 403, 1965 Ashley Falls - Ratcliffe, USGS OF 75-148 Avon - Schnabel, GQ 134, 1960 Bashbish Falls - Zen and Hartshorn, GQ 507, 1966 Bayville - No bedrock exposed Bethel - Clarke, ms. (CGNHS) Botsford - Heyl, ms. (CGNHS) Branford - Sanders, ms. (CGNHS); Rodgers, ms. (Yale) Brewster - Prucha, Scotford, and Sneider, NYSMMC 11, 1968; Geol. Map of N.Y., NYSMMC 15, 1970 Bridgeport - Crowley, QR 24, 1968 Bristol - Simpson, ms. (USGS) Broad Brook - Colton, GQ 434, 1965 Clinton - Lundgren and Thurrell, QR 29, 1973 Colchester - Lundgren and Snyder, QR 27, 1971 Collinsville - Stanley, QR 16, 1964 Columbia - Snyder, GQ 592, 1967 Cornwall - Gates, QR 11, 1961 Danbury - Clarke, QR 7, 1958 Danielson - Dixon, GQ 696, 1968 Deep River - Lundgren, QR 13, 1963; London, ms. (CGNHS-1985, in prep.) Dover Plains - Carroll, ms. (Yale); Jackson, ms. (U. Mass.) Durham - Simpson, USGS OF, 1969; de Boer, ms. (CGNHS); Steinen, ms. (U. Conn.) Eastford - Pease, GQ 1023, 1973 East Killingly - Moore, GQ 1571, 1983 Ellington - Collins, QR 4, 1954 Ellsworth - Burr, ms. (U. Mass.) Essex - Lundgren, QR 15, 1964 Fitchville - Snyder, USGS Bull. 1161-1, 1964 Glastonbury - Herz, QR 5, 1955 Glenville - Hall, ms. (CGNHS) Guilford - Bernold, Loilis, de Neufville, mss. (Yale) Haddam - Lundgren, QR 37, 1979 Hamburg - Lundgren, QR 19, 1966 Hampden - Peper, GQ 1368, 1977 Hampton - Dixon and Pessl, GQ 468, 1966 Hartford North - Cushman, GQ 223, 1963 Hartford South - Weitz, Byrnes, mss. (CGNHS) Jewett City - Dixon, ms. (USGS).* Kent - Jackson, ms. (U. Mass) and (CGNHS) Litchfield - Gates, QR 1, 1951 Long Hill - Crowley, QR 24, 1968 Mamaroneck - Pellegrini, NYSMMC 29, 1977; Hall, ms. (U. Mass.) Manchester - Colton, GQ 433, 1965 Marlborough - Snyder, GQ 791, 1969 Meriden - Hanshaw, GQ 738, 1968 Middle Haddam - Eaton and Rosenfeld, USGS OF, 1972; London, ms. (CGNHS-1985, in prep.) Middletown - Lehmann, QR 8, 1959 Milford - Fritts, GQ 427, 1965 Millerton - Geol. Map of N.Y., NYSMMC 15, 1970 Monson - Peper, GQ 1374, 1977 Montville - Goldsmith, GQ 609, 1967 Moodus - Lundgren and Ashmead, QR 27, 1971 Mount Carmel - Fritts, GQ 199, 1963 Mount Kisco - Hall, ms. (U. Mass.) Mystic - Goldsmith, USGS OF 75-602 Naugatuck - Cary, QR 9, 1960 New Britain - Simpson, GQ 494, 1966 New Hartford - Schnabel, GQ 1257, 1975 New Haven - Burger, RI 4, 1967; Sanders, ms. (CGNHS); Rodgers, ms. (Yale) New London - Goldsmith, GQ 574, 1967 New Milford - Caldwell, ms. (U. Mass.) New Preston - Gates, QR 2, 1952; Dana, ms. (U. Mass.) Newtown - Stanley, QR 33, 1976 Niantic - Goldsmith, GQ 575, 1967 Norfolk - Harwood, GQ 1518, 1979 Norwalk North - Kroll, QR 34, 1977 Norwalk South - Kroll, QR 34, 1977 Norwich - Snyder, GQ 144, 1961 Old Lyme - Lundgren, QR 21, 1967 Old Mystic - Goldsmith, ms. (USGS) Oneco - Harwood and Goldsmith, GQ 930, 1971 Oxford - Dixon, ms. (USGS); Barosh, USGS OF 76-622 Pawling - Geol. Map of N.Y., NY StMus MandC 15, 1970 Peach Lake - Prucha, Scotford, and Sneider, NYSMMC 11, 1968 Plainfield - Dixon, GQ 481, 1965 Pound Ridge - Hall, ms. (U. Mass.) Putnam - Dixon, GQ 1562, 1982 Rockville - Aitken, QR 6, 1955; Pease, ms. (USGS) Roxbury - Gates, GQ 121, 1959 Scotland - Dixon and Shaw, GQ 392, 1965 Sharon - Gates, QR 38, 1979 Sherwood Point - Dieterich, ms. (CGNHS) Southbridge - Moore, USGS OF 78-220 Southbury - Scott, QR 30, 1974 South Canaan - Gates, QR 32, 1975; Harwood, ms. (USGS) South Coventry - Fahey and Pease, USGS OF 77-584; Snyder, ms. (USGS); Wintsch, ms. (U. Ind.) Southington - Fritts, GQ 200, 1963 South Sandisfield - Harwood, GQ 1519, 1979 Southwick - Schnabel, GQ 1170, 1974 Springfield South - Hartshorn and Koteff, GQ 678, 1967 Spring Hill - Pease, Snyder, Dixon, mss. (USGS); Wintsch, ms. (U. Ind.) Stafford Springs - Pease, USGS OF 75-633; Pease, GB 5, 1982 Stamford - Frank, ms. (CGNHS) Tariffville - Schnabel and Eric, GQ 370, 1965 Thomaston - Cassie, ms. (CGNHS) Thompson - Dixon, GQ 1165, 1974 Tolland Center - Harwood, Ratcliffe, mss. (USGS) Torrington - Martin, QR 25, 1970 Uncasville - Goldsmith, GQ 576, 1967 Voluntown - Feininger, GQ 436, 1965 Wales - Seiders, GQ 1320, 1976 Wallingford - Sanders, rns. (CGNHS); King, Rodgers, mss. (Yale) Watch Hill - Moore, GQ 655, 1967 Waterbury - Gates and Martin, QR 22, 1967; Dietsch, ms. (Yale) Webster - Barosh, USGS OF 74-192; Dixon, ms. (USGS) Westford - Peper and Pease, GQ 1214, 1975 West Granville - Schnabel, USGS OF, 1973 Westport - Dieterich, ms. (CGNHS) West Springfield - Colton and Hartshorn, GQ 537, 1966 West Torrington - Gates and Christensen, QR 17, 1965; Merguerian, ms. (CUNY) Willimantic - Snyder, GQ 335, 1964 Windsor Locks - Schnabel and Eric, GQ 388, 1964 Winsted - Martin, ms. (CGNHS); Harwood, ms. (USGS) Woodbury - Gates, QR 3, 1954; Schutz, Naruk, mss. (Yale) Woodmont - Rodgers, ms. (Yale); Sanders, ms. (CGNHS) ABBREVIATIONS CGNHS - Connecticut Geological and Natural History Survey, Department of Environmental Protection, State of Connecticut GB - Guidebook, Connecticut Geological and Natural History Survey GQ - Geologic Quadrangle map, U.S. Geological Survey ms. - Unpublished manuscript including theses mss. - Separate unpublished manuscripts by individual authors listed NYSMMC - New York State Museum Map and Chart Series, Education Department, State of New York OF - Open file report, U.S. Geological Survey QR - Quadrangle Report, Connecticut Geological and Natural History Survey RI - Report of Investigations, Connecticut Geological and Natural History Survey USGS - United States Geological Survey, Department of the Interior
SOURCE MATERIALS used in compiling the Bedrock Geological Map of Connecticut, 1985, listed by author. PUBLISHED REFERENCES CITED Aitken, J.M., 1955, The bedrock geology of the Rockville quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 6, 55 p., map. Burger, H.R., 1967, Stratigraphy and structure of the western part of the New Haven quadrangle, Connecticut: Conn. Geo . Nat. History Survey Rept. Invs. 4, 15 p., map. Carr, M.H., 1960, The bedrock geology of the Naugatuck quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 9, 25 p., map. Clarke, J.W., 1958, The bedrock geology of the Danbury quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 7, 47 p., map. Collins, G.E., 1954, The bedrock geology of the Ellington quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 4, 44 p., map. Colton, R.B., 1965a, Geology of the Manchester quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-433. Colton, R.B., 1965b, Geology of the Broad Brook quadrangle: U.S. Geol. Survey Geol.Quad@ Map GQ-434. Colton, R.B., and Hartshorn, J.H., 1966, Bedrock geology of the West Springfield quad- rangle: U.S. Geol. Survey Geol. Quad. Map GQ-537. Crowley, W.P., 1968, The bedrock geology of the Long Hill and Bridger)ort quadrangles: Conn. Geol. Nat. History Survey Quad. Rept. 24, 81 p., maps. Cushman, R.V., 1963, Geology of the Hartford North quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-223. Dixon, H.R., 1965, Bedrock geology of the Plainfield quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-481. Dixon, H.R., 1968, Bedrock geology of the Danielson quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-696. Dixon, H.R., 1974, Bedrock geology of the Thompson quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ- 1 165. Dixon, H.R., 1982, Bedrock geologic map of the Putnam quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1562. Dixon, H. R., and Pessi, Fred, Jr., 1966, Geology of the Hampton quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-468. Dixon, H.R., and Shaw, C.E., Jr., 1965, Geology of the Scotland quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-392. Emerson, B.K., 1898, Geology of old Hampshire County, Massachusetts, comprising Franklin, Hampshire, and Hampden Counties: U.S. Geol. Survey Mon. 29, 790 p. Emerson, B.K., 1917, Geology of Massachusetts and Rhode Island: U.S. Geol. Survey Bull. 597, 289 p. Feininger, Tomas, 1965a, Bedrock geology of the Ashaway quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-403. Feininger, Tomas, 1965b, Bedrock geology of the Voluntown quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-436. Fisher, D.W., Isachsen, Y.W., and Rickard, L.V., 1970, Geologic map of New York, Lower Hudson sheet: New York State Mus. Map and Chart Ser. 15. Fritts, C.E., 1963a, Bedrock geology of the Mount Carmel quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-199. Fritts, C.E., 1963b, Bedrock geology of the Southington quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-200. Fritts, C.E., 1965a Bedrock Geology of the Ansonia quadrangle: U.S. Geol. Survey Geol. Quad.Map GQ-426. Fritts, C.E., 1965b, Bedrock geology of the Milford quadrangle: U.S. Geol. Survey Geol.Quad. Map GQ-427. Gates, R.M., 1951, The bedrock geology of the Litchfield quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 1, (Misc. Ser. 3), 13 p., map. Gates, R.M., 1954, The bedrock geology of the Woodbury quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 3, 32 p., map. Gates, R.M., 1959, Bedrock geology of the Roxbury quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-121. Gates, R.M., 1961, The bedrock geology of the Cornwall quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 11, 35 p., map. GaLes, R.M., 1975, The bedrock geology of the South Canaan quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 32, 33 p., map. Gates, R.M., 1979, The bedrock geology of the Sharon quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 38, 24 p., map. Gates, R.M., and Bradley, W.C., 1952, The geology of the New Preston quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 2, (Misc. Ser. 5) 46 p., maps. Gates, R.M., and Christensen, N.I., 1965, The bedrock geology of the West Torrington quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 17, 38 p., map. Gates, R.M., and Martin, C.W., 1967, The bedrock geology of the Waterbury quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 22, 36 p., map. Goldsmith, Richard, 1967a, Bedrock geology of the New London quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-574. Goldsmith, Richard, 1967b, Bedrock geology of the Niantic quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-575. Goldsmith, Ricbard, 1967c, Bedrock geology of the Uncasville quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-576. Goldsmith, Richard, 1967d, Bedrock geology of the Montville quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-609. Gregory, H.E., and Robinson, H.H., 1907, Preliminary geological map of Connecticut: Survey Geol. Quad. Map GQ-574. Goldsmith, Richard, 1967b, Bedrock geology of the Niantic quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-575. Goldsmith, Ricbard, 1967c, Bedrock geology of the Uncasville quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-576. Goldsmith, Richard, 1967d, Bedrock geology of the Montville quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-609. Gregory, H.E., and Robinson, H.H., 1907, Preliminary geological map of Connecticut: Conn. Geol. Nat. History Survey Bull. 7, 39 p., map [map is dated 19061. Hanshaw, P.M., 1968, Bedrock geology of the Meriden quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-738. Hartshorn, J.H., and Koteff, Carl, 1967, Geology of the Springfield South quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-678. Harwood, D.S., 1979a, Bedrock geology of the Norfolk quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1518. Harwood, D.S., 1979b, Geology of the South Sandisfield quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1519. Harwood, D.S., and Goldsmith, Richard, 1971, Geology of the Oneco quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-930. Herz, Norman, 1955, The bedrock geology of the Glastonbury quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 5, 22 p., map. Kroll, R.L., 1977, The bedrock geology of the Norwalk North and Norwalk South quad- rangles: Conn. Geol. Nat. History Survey Quad. Rept. 34, 64 p., maps. Krynine, P.D., 1950, Petrology, stratigraphy, and origin of the Triassic sedimentary rocks of Connecticut: Conn. Geol. Nat. History Survey Bull. 73, 239 p. Lehman,p, E.P., 1959, The bedrock geology of the Middletown quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 8, 40 p., map. Lundgren, Lawrence, Jr., 1963, The bedrock geology of the Deep River quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 13, 40 p., map. Lundgren, Lawrence, Jr., 1964, The bedrock geology of the Essex quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 15, 37 p., map. Lundgren, Lawrence, Jr., 1966, The bedrock geology of the Hamburg quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 19, 41 p., map. Lundgren, Lawrence, Jr., 1967, The bedrock geology of the Old Lyme quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 21, 30 p., map. Lundgren, Lawrence, Jr., 1979, The bedrock geology of the Haddam quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 37, 44 p., map. Lundgren, Lawrence, Jr., Ashmead, Lawrence, and Snyder, G.L., 1971, The bedrock geology of the Moodus and Colchester quadrangles: Conn. Geol. Nat. History Survey Quad. Rept. 27, 24 p., maps. Lundgren, Lawrence, Jr., and Thurrell, R.F., 1973, The bedrock geology of the Clinton quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 29, 22 p., map. Martin, C.W., 1970, The bedrock geology of the Torrington quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 25, 53 p., map. Moore, G.E., Jr., 1967, Bedrock geology of the Watch Hill quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-655. Moore, G.E., Jr., 1983, Bedrock geologic map of the East Killingly quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1571. Pease, M.H., Jr., 1973, Geology of the Eastford quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1023. Pease, M.H., 1982, The Bone Mill Brook fault, eastern Connecticut: in New England lntercoll. Geol. Conf., 74th Ann. Mtg., Univ. of Connecticut: Connecticut Geol. Nat. History Survey Guidebook 5, Trip P-2. Pelligrini, T.L., 1977, Bedrock geology of the Mamaroneck quadrangle: New York State Mus. Map and Chart Ser. 29. Peper, J.D., 1977a, Bedrock geology of the Hampden quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1368. Peper, J.D., 1977b, Bedrock geology of the Monson quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1374. Peper, J. D., and Pease, M.H., Jr., 1975, Geology of the Westford quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1214. Percival, J.G., 1842, Report on the geology of the State of Connecticut: New Haven, 495 p., map. Prucha, J.J., Scotford, D.M., and Sneider, R.M., 1968, Bedrock geology of parts of Putnam and Westchester Counties, New York, and Fairfield County, Connecticut: New York State Mus. Map and Chart Set. 11, 26 p., map. Rodgers, John, Cameron, E.N., Gates, R.M., and Ross, R.J., Jr., 1956, Preliminary geological map of Connecticut: Conn. Geol. Nat. History Survey. Schnabel, R.W., 1960, Bedrock geology of the Avon quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-134. Schnabel, R.W., 1974, Bedrock geology of the Southwick quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ- 1 170. Schnabel, R.W., 1975, Geology of the New Hartford quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1257. Schnabel, R.W., and Eric, J.H., 1964, Bedrock geology of the Windsor Locks quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-388. Schnabel, R.W., and Eric, J.H., 1965, Bedrock geology of the Tarriffville quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-370. Scott, R.B., 1974, The bedrock geology of the Southbury quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 30, 63 p., map. Sciders, V.M., 1976, Bedrock geology of the Wales quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1320. Simpson, H.E., 1966, Bedrock geology of the New Britain quadrangle: U.S. Geol. Survey Geol.. Quad. Map GQ-494. Snyder, G.L., 1961, Bedrock geology of the Norwich quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-144. Snyder, G.L., 1964a, Petrochemistry and bedrock geology of the Fitchville quadrangle: U.S. Geol. Survey Bull. 1161-1, 63 p., map. Snyder, G.L., 1964b, Bedrock geology of the Willimantic quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-335. Snyder, G.L., 1967, Bedrock geology of the Columbia quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-592. Snyder, G.L., 1969, Bedrock geology of the Marlborough quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-791. Stanley, R.S., 1964, The bedrock geology of the Collinsville quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 16, 99 p., map. Stanley, R.S., 1976, The bedrock geology of the Newtown quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 33, 44 p., map. Zen, E-an, ed., Goldsmith, Richard, Ratcliffe, N.M., Robinson, Peter, and Stanley, R.S., compilers, 1983, Bedrock geologic map of Massachusetts: Reston, Va., U.S. Geo- logical Survey, scale 1:250,000, 3 sheets. Zen, E-an, and Hartshorn, J.H., 1966, Geology of the Bashbish Falls quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-507. ADDITIONS Dixon, H.R., and Felmlee, J.K., (in press), Bedrock geologic map of the Jewett City quadrangle: U.S. Geological Survey Geol. Quad. Map GQ-1575. Goldsmith, Richard, 1985, Bedrock geologic map of the Old Mystic and part of the Mystic quadrangles: U.S. Geological Survey Misc. Inv. Ser. Map 1-1524.
1:50,000-scale mylar overlay compilation sheets used to publish the Bedrock Geological Map of Connecticut, 1985.
Bedrock Geology Layer is in ArcInfo coverage format having both polygon and line features.
Includes all line features from Source 3 - Bedrock Geology Layer (ArcInfo Coverage format). Bedrock_Geology_Line.shp is in Shapefile format.
Bedrock_Geology_Line is in GeoDatabase Feature Class format.
Compilation - Original compilations at 1:24,000 scale under the direction of John Rodgers, Yale University, were prepared from existing geologic quadrangle mapping and other interpretations (see Source 1 - Source Materials). 1:50,000-scale regional mylars were compiled by the Connecticut Geological and Natural History Survey to resolve mapping differences between adjacent 1:24,000 scale sheets and were used as a common publication base to produce the final map. Connecticut Geological and Natural History Survey contractors and staff manually digitized regional compilations sheets. Topographic bases used in the original geologic compilation from USGS 1:24,000 scale revisions 1952-1970. Compilation bases, and publication preparation by the Connecticut Department of Environmental Protection from U.S. Geological Survey 1:50,000 scale County Map Series. Base map contour intervals and other features are specific to individual county maps. There are 7 regional compilation areas divided into Northeast, North Central, Northwest, Central West, South Central, Southeast, and Southwest sheets. These are defined along 41 degrees, 15 minutes; 41 degrees, 15 minutes, 30 seconds of latitude and 73 degrees; 72 degrees, 22 minutes, 30 seconds of longitude.
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Digital Automation - Bedrock geology digital data were produced by the Connecticut Geological and Natural History Survey, Connecticut Department. of Environmental Protection with support from the U.S. Geological Survey, the U.S. Environmental Protection Agency, and the Connecticut Department of Public Health. Using ESRI ArcInfo software, features were digitized by registering each 1:50,000-scale source map to the digitizing tablet and using the crosshairs of the digitizer's mouse to manually capture the geometry (location) of features drafted on the map. The (rectangular) area mapped on each 1:50,000-scale source map is defined by a set of 7.5-minute quadrangle areas. Mapped at 1:50,000-scale, the corners of USGS 7.5 minute topographic quadrangle maps are used as registration points and are depicted on the source map. The source map was registered to the digitizing tablet by digitizing (entering) the locations of four outermost quadrangle corner registration points shown on the map. ArcInfo software compared the values of the digitized coordinates with the actual (true) values for the quadrangle corner (tic) features. The Root Mean Square (RMS) error generated by the ArcInfo software indicated the amount of error involved in transforming coordinates from the registered map to the digital layer. Typically, RMS errors higher than 0.004 are not acceptable and required re-registering the source map by digitizing the tic locations again. The actual RMS values were not documented, but are assumed to be within acceptable range. With a correct registration, individual polygon boundary features were manually digitized off the source map. Polygon features were assigned UNIT values to denote the Bedrock Geology Unit, and line features were assigned CLASS_COD and TERRB_COD to denote geographic boundaries, contacts and faults. Where necessary, additional minor corrections (edits) to feature geometry were manually digitized on the screen (heads-up digitizing) at display scales greater than 1:24,000. Features were assigned attribute values based on information shown on the 1:50,000-scale compilation sheets. Feature location and attribute accuracy was visually checked and inspected by symbolizing and labeling features according to UNIT, CLASS_COD and TERRB_COD attribute values on the computer screen and on hard copy paper maps in order to verify the accuracy of the manually encoded attribute values. These check plot maps were printed at the same scale as the source maps in order to visually inspect digitizing quality and the assignment of attribute values. Digitzing each 1:50,000-scale sheet resulted in the creation of an ArcInfo coverage having both polygon and line features. All ArcInfo coverages where subsequently appended to create the statewide Bedrock Geology layer in ArcInfo Coverage format. Throughout this process, the ArcInfo Clean function was repeatedly used following edits to verify topology and enforce a minimum distance between vertices of 4 feet (fuzzy tolerance) and a minimum allowed overshoot length of 10 feet (dangle length). Additional attributes were added to the statewide layer by joining the corresponding lookup tables to polygon and line features.
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Export to Shapefile format - Converted line feature data from an ArcInfo coverage named BEDROCK to a Shapefile named Bedrock_Geology_Line.shp. Excluded the FNODE#, TNODE#, LPOLY#, RPOLY#, LENGTH, BEDROCK#, BEDROCK-ID attributes from the Shapefile because their values are only maintained by ArcInfo software with spatial data that is ArcInfo coverage format.
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Convert to GeoDatabase Feature Class format - Defined new Feature Class named Bedrock_Geology_Line; and imported the attribute definitions, loaded features and imported metadata from Bedrock_Geology_Line.shp shapefile. Spatial Reference Properties for Feature Class: Coordinate System: NAD_1983_StatePlane_Connecticut_FIPS_0600_Feet XY Domain MinX: 100000; MaxX: 2247483.645 XY Domain MinY: 200000; MaxY: 2347483.645 Precision: 1000
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Internal feature number.
ESRI
Feature geometry.
ESRI
Bedrock Line Class - Describes the type of bedrock lines mapped. Classes include contacts, faults of various types, cartographic boundaries, and limits of mapping.
State of Connecticut, Department of Environmental Protection
Boundary
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Cartographic Boundary - Line introduced to close a polygon
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Geologic Contact
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Contact with a questionable termination
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Fault
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Fault approximately located
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Fault Questionable - Otherwise interpret as a contact
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High angle fault, mostly Jurassic
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Fault with a questionable termination
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Strike-slip fault
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Thrust fault, mostly Devonian or Ordovician
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Folded and overturned thrust fault - deformed
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Folded thrust fault
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Klippe or Outlier of upper plate of thrust fault
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Overturned thrust fault
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Window or Inlier through upper plate of thrust fault
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Limit of bedrock mapping
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Bedrock Line Class Definition - Text values that correspond to the numeric CLASS attribute values. DEFINITION is the English language equivalent of (decodes) the CLASS field.
State of Connecticut, Department of Environmental Protection
ArcView Legend. A text field to easily classify and symbolize bedrock line types on a map.
State of Connecticut, Department of Environmental Protection
Inludes CLASS attribute value B.
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Includes CLASS attribute values C and CQT.
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Includes CLASS attribute values F, FA, FC, FH, FQT, FQT, FS, FT, FTD, FTF, FTK, FTO, and FTW.
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Inludes CLASS attribute value L.
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Inludes CLASS attribute value BC.
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Terrane Boundary Code - Identifies and describes the significant geologic terrane boundaries, including the Eastern Border Fault, the Lake Char/Honey Hill Fault, and Cameron's Line.
State of Connecticut, Department of Environmental Protection
Not a terrane boundary
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Cameron's Line
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East Derby Fault
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Eastern Border Fault
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Faults Beneath Taconic Allochthons
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Faults Beneath Taconic Allochthons - inferred
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Honey Hill Fault
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Lake Char Fault
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Western Border Fault
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Willimantic Window
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Terrane Boundary - Text values that correspond to numeric TERR_COD attribute values. TERR_BNDRY is the English language equivalent of (decodes) the TERRB_COD field.
State of Connecticut, Department of Environmental Protection
Bedrock Geology polygon features describe 157 geologic units for arkose, basalt, gneiss, granite, marble, shist, shale and other rock types. The information encoded about the geologic unites includes the formation name, description, geologic terrane, and age. Use the UNIT attribute as the key field that identifies and differentiates bedrock units. Refer to the FORMATION attribute for the name of the geologic unit. Label a map with either the UNIT or FORMATION attribute. Refer to the DESCRIPTION attribute for a brief explanation of the geologic unit. For cartographic purposes, symbolize polygon features on a map using either the UNIT or TERRANE attribute, depending on the desired level of detail. Use the LITHO1, LITHO2, LITHO3, LITHO4, and LITHO5 for information about the lithology of the geologic unit. The Bedrock Geology layer also describes 17 classes of geologic boundaries, contacts and faults. Line feature attributes are primarily for cartographic purposes. For example, when symbolizing polygon features on different UNIT attribute values, also uniquely symbolize line features on the CLASS_COD or DEFINITION attribute to emphasize the various boundary types. When symbolizing polygon features on different TERRANE attribute values, also uniquely symbolize line features on the TERRB_COD or TERR_BNDRY to emphasize the terrain boundaries.
Bedrock Geology of Connecticut (Rogers, J., State of Connecticut, Department of Environmental Protection, 1985, scale 1:125,000)
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Although this data set has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection as to the accuracy of the data and or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut, Department of Environmental Protection in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data is distributed to the user, modifications made to the data by the user should be noted in the metadata.
The data distributor does not provide custom GIS analysis or mapping services. Data is available in a standard format and may be converted to other formats, projections, coordinate systems, or selected for specific geographic regions by the party receiving the data.
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