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.
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
Bedrock Geology map units represented as polygon features. (Source: State of Connecticut, Department of Environmental Protection)
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
Geologic Unit - Represents the map unit symbol for bedrock geology polygon features. Upper case letters in the map unit represent the geologic age of the formation. Lower case letters in the map unit represent the formation. Map units (Geological Formations) with more than one upper case letter denote a geologic age range represented by the formation (i.e. DSts, The Straits Schist, denotes Devonian and Silurian aged rock unit). Use of the question mark indicates uncertainty about the age or the identification of the geologic formation. For example: D?d denotes uncertainty about the designation of D (Devonian) for the age of the geologic formation. Jb? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit. C is used for the Cambrian age rocks ~ 500 mya - 570 mya. There are no Cretaceous age rocks in Connecticut. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Cc | Cheshire Quartzite (Lower Cambrian) - Mainly pure, white, glassy, tough quartzite |
| Cd | Dalton Formation (including Poughquag Quartzite and Lowerre Formation) (Lower Cambrian and perhaps partly older) - Gray, tan-weathering, medium grained, generally well layered gneiss or feldspathic quartzite, composed of quartz, microcline, plagioclase, muscovite, biotite, and generally tourmaline; some schistose micaceous layers have sillimanite, commonly as quartz-sillimanite nodules rimmed with muscovite. Layers of purer quartzite in many areas, especially near the top or where the formation is thin |
| Ce | Everett Schist (Cambrian?) - Grayish to greenish (some rusty-weathering), fine-to medium-grained, foliated but poorly layered schist or phyllite, composed or quartz, albite or oligoclase, muscovite, garnet, staurolite or chloritoid, and generally chlorite. Local layers are dark-gray to silvery schist or phyllite |
| Ch | Hoosac Schist (Cambrian?) - Light-to medium-gray, rusty-weathering, fine- to medium-grained schist and poorly layered schistose gneiss, composed of quartz, biotite, plagioclase, muscovite, and generally garnet and sillimanite or kyanite |
| Cm | Manhattan Schist (including Waramaug Formation and Canaan Mountain Schist) - (Cambrian?) - Dark-gray to silvery, rusty-weathering, generally coarse grained, foliated but poorly layered to massive gneiss or schistose gneiss, composed of quartz, oligoclase, microcline, biotite, and muscovite, and generally sillimanite and garnet. Amphibolite layers locally, especially near base where in places separately mapped as unit Cma |
| Cma | Amphibolite-bearing unit of Manhattan Schist (Cambrian?) - Like Manhattan Schist but with numerous lenses and layers of amphibolite |
| Cmcl | Lower slice of Canaan Mountain Schist (Cambrian?) - Dark-gray, rusty-weathering, coarse-grained, well-foliated and moderately well layered schist composed of quartz, plagioclase, biotite, muscovite, and generally garnet and sillimanite (or minor staurolite). Amphibolite layers rather rare |
| Cmcu | Upper slice of Canaan Mountain Schist (Cambrian?) - Dark-gray to silvery, generally rusty weathering, medium- to coarse-grained, well-foliated, massive to well-layered schist and schistose gneiss, composed of quartz, plagioclase, biotite, muscovite, and generally garnet and sillimanite; also layers of amphibolite |
| Cmcub | Basal member of upper slice of Canaan Mountain Schist (Cambrian?) - Gray, generally rusty- or tan-weathering gneiss, composed of quartz, plagioclase, microline, biotite, and muscovite, interlayered with feldspathic quartzite |
| Csa | Unit a [of Stockbridge Marble] (Lower Cambrian) - White to pale-gray, massive, smooth-weathering dolomite marble |
| Csb | Unit b [of Stockbridge Marble] (Upper and Middle? Cambrian) - White, pink, cream, and light-gray, generally well-bedded dolomitic marble interlayered with phyllite and schist and with siltstone, sandstone, or quartzite, commonly dolomitic |
| Csc | Unit c [of Stockbridge Marble] (Upper Cambrian) - Gray, generally massive dolomite marble, commonly contains quartz grains, locally beds of sandstone; may be calcitic near top |
| Cwb | Waterbury Gneiss (Proterozoic Z or Cambrian or both) - Medium- to dark-gray, fine- to medium-grained, generally irregularly foliated and lenticular rather than regularly layered schist and schistose gneiss, composed of biotite, quartz, oligoclase, kyanite (or sillimanite), and garnet, also locally microcline, irregularly mixed with granitoid gneiss, composed of oligoclase or andesine, quartz, biotite, and commonly microcline and muscovite |
| D?d | Foliated quartz diorite (Devonian in part, probably Ordovician in part) - Mainly dark-gray, medium-grained, well-foliated gneiss (locally strongly sheared, especially near contacts), composed of plagioclase, quartz, biotite, and hornblende, locally also pyroxene (? denotes uncertainty about the designation of D (Devonian) for the age of the geologic formation). |
| DSs | Scotland Schist (Devonian or Silurian or both) - Gray to silvery, locally rusty, fine- to medium-grained schist, composed of quartz, muscovite, biotite, staurolite, and oligoclase, locally with kyanite or sillimanite; interlayered, especially below and to the west, with quartz-oligoclase-biotite schist and granofels and locally with quartzite |
| DSsq | Quartzite unit [in Scotland Schist] (Devonian or Silurian or both) - Quartzite, generally micaceous, interlayered with mica schist |
| DSt | The Straits Schist (= Goshen Formation of Massachusetts) (Devonian or Silurian or both) - Silvery to gray, non-rusty, coarse- to very coarse grained, generally poorly layered schist, composed of quartz, muscovite, biotite, oligoclase, garnet, and commonly staurolite and kyanite or sillimanite; graphitic almost throughout |
| DSts | Southington Mountain Member [of The Straits Schist] (Devonian or Silurian or both) - Gray to silvery, non-rusty, medium-grained, well-layered alternating schist and granofels, composed of quartz, oligoclase, muscovite, biotite, and garnet, commonly with staurolite and kyanite (or sillimanite); schist commonly graphitic |
| DSw | Wepawaug Schist (Devonian or Silurian or both) - Medium- to dark-gray, medium- to fine-grained, well-layered schist or phylite and metasiltstone, composed of quartz, muscovite or sericite, plagioclase, biotite, and in appropriate metamorphic zones chlorite, garnet, staurolite, and kyanite. Schist or phyllite generally graphitic |
| Dbl | Littleton Formation (Devonian) - Gray to silvery, generally non-rusty, medium-grained, massive to well-layered alternating schist and micaceous quartzite, composed of quartz, muscovite, biotite, garnet, and oligoclase, also staurolite, graphite, and ilmenite, and in certain areas kyanite or sillimanite in schist |
| Dbl? | Littleton Formation - see Dbl (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Dblm | Mount Pisgah Member of Littleton Formation (Devonian) - Gray, medium-grained, well-layered (locally graded) granofels or micaceous quartzite with some schist, composed of quartz, oligoclase, biotite, garnet, and sillimanite |
| Dc | Canterbury Gneiss (may be equivalent to Ayer Granite of Massachusetts) (Devonian) - Light-gray, medium-grained, variably foliated, locally strongly lineated gneiss, composed of quartz, oligoclase, microcline, and biotite, locally also muscovite or epidote, and generally with megacrysts 1 to 2 cm long of either or both feldspars |
| Dce | 'Eastford gneiss phase' [of Canterbury Gneiss] (Devonian) - Mainly light gray, medium-grained, foliated to strongly lineated gneiss, composed of quartz, microcline, oligoclase or albite, biotite, and muscovite |
| De | Erving Formation (Devonian) - Gray, medium-grained, well-foliated and generally well layered granofels and schist, composed of quartz, plagioclase, and biotite, also muscovite in schist, and accessory garnet and kyanite |
| Dgg | Foliated granitic gneiss (Devonian?) - Light-gray, coarse-grained, strongly to weakly foliated gneiss, composed of phenocrysts of K-feldspar in a groundmass of plagioclase, quartz, K-feldspar, and biotite, with accessory sillimanite and garnet |
| Dl | Lebanon Gabbro (Devonian) - Dark, speckled, coarse-grained, massive but locally sheared gabbro, composed of hornblende, labradorite, and opaques. Some bodies contain biotite and quartz; some smaller ones are nearly pure hornblende with local augite |
| Dld | Dioritic phase [of Lebanon Gabbro] (Devonian) - White to black, streaked, medium-grained, foliated or sheared gneiss, composed of plagioclase, biotite, quartz, and generally hornblende |
| Dlp | Lamprophyre (Devonian?) - Dark-gray to greenish, fine-grained, badly altered dike rock, composed of biotite, augite, K-feldspar, and accessory apatite and sphene, plus secondary minerals |
| Dm | Maromas Granite Gneiss (Devonian?) - Light-gray to buff, medium- to fine-grained granitic gneiss, composed of quartz and microcline with minor plagioclase and biotite. Central body is massive, but outlying strips are foliated and have accessory hornblende or garnet. Massive parts may be young anatectic intrusive rocks; foliated parts may include older felsic metavolcanic rocks belonging to unit Ochv. Pegmatite bodies are common in the vicinity |
| Dn | Hornblende norite (Devonian?) - Dark, coarse-grained, massive rock, composed of bytownite, hornblende, and hypesthene |
| Dng | Nonewaug Granite (Devonian) - White to pink, fine- to very coarse grained (commonly pegmatitic), massive to layered granite composed of albite, microcline, quartz, and muscovite, with minor biotite and garnet. Microcline commonly graphic; quartz and muscovite commonly in plumose aggregates |
| Jb | Buttress Dolerite (Middle? Jurassic) - Dark-gray to greenish-gray (weathers brown or gray), medium- to fine-grained, commonly porphyritic, generally massive with well-developed columnar jointing, grading from basalt near contacts to fine-grained gabbro in the interior, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine |
| Jb? | Buttress Dolerite - see Jb (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Jeb | East Berlin Formation (Lower Jurassic) - Maroon siltstone, silty and sandy shale, and fine-grained silty sandstone, generally well laminated and commonly well indurated, alternating with dark fissile shale; dolomitic carbonate common in cement, concretions, and thin argillaceous laminae. Local arkose; grades eastward into coarse conglomerate close to eastern border fault |
| Jha | Hampden Basalt (Lower Jurassic) - Greenish-gray to black (weathers bright orange to brown), fine- to medium-grained, grading from basalt near contacts to fine-grained gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass |
| Jho | Holyoke Basalt (Lower Jurassic) - Greenish-gray to black (weathers bright orange to brown), fine- to coarse-grained, grading from basalt near contacts to gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass |
| Jp | Portland Arkose (Lower Jurassic) - Reddish-brown to maroon micaceous arkose and siltstone and red to black fissile silty shale. Grades eastward into coarse conglomerate (fanglomerate) 'Meriden Formation' of Krynine (1950) (Lower Jurassic) |
| Jsi | Silicified rock and mylonite along Mesozoic faults (probably mainly Jurassic) - Close network of quartz veins and veinlets cutting each other and older rock, which is mostly replaced by very fine grained quartz. In places, incompletely replaced rock shows strongly mylonitic texture. |
| Jsm | Shuttle Meadow Formation (Lower Jurassic) - Maroon to dark-gray, silty shale, siltstone, and fine-grained silty sandstone, generally well and thinly laminated. In the southern part of the State includes a layer, up to 5 m thick, of blue, commonly sandy, fine-grained limestone or dolomitic limestone, grading laterally into calcareous siltstone. Coarser and more arkosic to east and south, grading into conglomerate near the eastern border fault |
| Jta | Talcott Basalt (Lower Jurassic) - Greenish-gray to black (weathers bright orange to brown), fine- to medium-grained, grading from basalt near contacts to fine-grained gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass. Pillows in may places; volcanic breccia with fragmentary pillows in others |
| Jwr | West Rock Dolerite (Lower Jurassic) - Dark-gray to greenish-gray (weathers bright orange to brown), medium- to fine-grained, grading from basalt near contacts to fine-grained gabbro in the interior, generally massive with well-developed columnar jointing, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine |
| Jwr? | West Rock Dolerite - see Jwr (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| OCr | Rowe Schist (Lower Ordovician or Cambrian or both) - Light-gray to silvery, fine- to medium-grained, generally poorly layered schist composed of quartz, muscovite, biotite, oligoclase, and generally garnet, staurolite, and kyanite or sillimanite. Layers of granofels common; also some layers of amphibolite, quartz-spessartine rock (coticule), and calc-silicate rock |
| OCr+OCra | Rowe Schist and Amphibolite unit in Rowe Schist undivided - see OCr and OCra |
| OCr? | Rowe Schist - see OCr (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| OCs | Stockbridge Marble (including Inwood Marble (Lower Ordovician and Cambrian) - White to gray, massive to layered marble, generally dolomitic but containing calcite marble in upper part, locally interlayered with schist or phyllite and with calcareous siltstone or sandstone |
| Oa | Allingtown Metavolcanics (Middle? Ordovician) - Green, fine-grained, massive greenstone, composed of epidote, actinolite, albite, and chlorite, commonly with abundant megacrysts of saussurite, interlayered with minor green phyllite, generally containing quartz and sericite. Dark amphibole in western outcrops |
| Oa+Oma | Allingtown Metavolcanics and Maltby Lakes Metavolcanics undivided - see Oa and Oma |
| Ob | Brookfield (dioritic and granodioritic) Gneiss (including Newtown Gneiss of Crowley, 1968) (Middle? Ordovician) - Dark and light, commonly speckled or banded, medium- to coarse-grained, massive to poorly foliated gneiss, composed of plagioclase, biotite, and hornblende, generally with quartz and K-feldspar, the latter commonly as megacrysts 1 to 3 cm across (also plagioclase megacrysts in darker rocks), locally associated with amphibolite or hornblende schist |
| Obr | Brimfield Schist (includes Hamilton Reservoir Formation) (Upper? and Middle Ordovician) - Gray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across. Minor layers and lenses of hornblende and pyroxene-bearing gneiss, amphibolite, and calc-silicate rock |
| Obr? | Brimfield Schist - see Obr (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Obrg | Gneiss (metavolcanic) member [of Brimfield Schist] (Upper? and Middle Ordovician) - Medium-gray, medium-grained, layered gneiss and schist, composed of oligoclase, quartz, and biotite; some gneiss and most schist layers contain garnet and sillimanite; some gneiss layers contain garnet, hornblende, or pyroxene or grade into amphibolite or calc-silicate rock. Probably includes metavolcanic rocks |
| Obs | Bristol Gneiss (Middle? Ordovician) - Light, medium-grained, massive to well-layered gneiss, composed of plagioclase, quartz, and biotite, also muscovite and garnet in many layers, interlayered in places with dark amphibolite |
| Oc | Collinsville Formation (Middle Ordovician) - Mixture of rock types as described for the two members; in many areas felsic and mafic striped metavolcanic rocks predominate |
| Ocg | Hornblende gneiss member [of Collinsville Formation] (Middle Ordovician) - Dark, fine- to medium-grained, well-layered amphibolite and hornblende gneiss, composed or hornblende and plagioclase, commonly with biotite, garnet, or epidote, interlayered with light-gray felsic gneiss and pink quartz-spessartine rock (coticule). Grades into Bristol Gneiss |
| Och | Collins Hill Formation ( = Partridge Formation of New Hampshire) (Upper? and Middle Ordovician) - Gray, rusty-weathering, medium- to coarse-grained, poorly layered schist, composed of quartz, oligoclase, muscovite, biotite, and garnet, and commonly staurolite, kyanite, or sillimanite, generally graphitic, interlayered with fine-grained two-mica gneiss, especially to the west, and with calc-silicate and amphibolite layers, also rare quartz-spessartine (colicule) layers |
| Ochv | Metavolcanic member [of Collins Hill Formation] (Upper? and Middle Ordovician) - Ranges from mafic to felsic, from dark layered amphibolite and hornblende schist, locally with garnet or epidote, to light-gray (in places purplish), laminated gneiss, composed of quartz, oligoclase, and biotite, in which some layers contain garnet (generally manganiferous) and hornblende or cummingtonite |
| Ocm | Cobble Mountain Formation (Middle Ordovician) - Gray to silvery (not rusty), medium- to coarse-grained, generally layered schist and granofels, composed of quartz, oligoclase, muscovite, biotite, and garnet, and locally kyanite and staurolite or sillimanite. Some amphibolite layers |
| Ocs | Sweetheart Mountain Member [of Collinsville Formation] (Middle Ordovician) - Gray and silvery (not rusty), medium- to coarse-grained, poorly layered schist, composed of quartz, oligoclase, biotite, muscovite, and garnet, and in places kyanite or sillimanite. Amphibolite layers common; also layers of quartz-spessartine rock (coticule) |
| Og | Ordovician(?) granitic gneiss (including local terms Ansonia, Mine Hill, 'Tyler Lake', 'Siscowit') (Middle Ordovician?) - White, light-gray, buff, or pink, generally foliated granitic gneiss, composed of sodic plagioclase, quartz, microcline, muscovite, and biotite, and locally garnet or sillimanite. Commonly contains numerous inclusions or layers of mica schist and gneiss |
| Og? | Ordovician? granitic gneiss - see Og (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Ogh | Golden Hill Schist (may be equivalent to part of Trap Falls Formation) (Lower? Ordovician) - Gray to silvery, medium- to coarse-grained, generally layered schist and granofels, composed of quartz, muscovite, biotite, plagioclase, and garnet |
| Ogh? | Golden Hill Schist - see Ogh (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Ogl | Glastonbury Gneiss (Middle? Ordovician) - Gray, medium- to coarse-grained, massive to well-foliated granitoid gneiss composed of oligoclase, quartz, microcline, and biotite, (as patches), also epidote and hornblende in many areas, commonly associated with layers of amphibolite; elsewhere minor muscovite and garnet |
| Oh | Harrison Gneiss (including Prospect Gneiss) (Middle? Ordovician) - Interlayered dark- and light-gray, medium-grained, well-foliated gneiss, composed of andesine, quartz, hornblende, and biotite (also locally K-feldspar as megacrysts 1 to 5 cm long). Thought to be metavolcanic equivalent of unit Ob |
| Oh? | Harrison Gneiss - see Oh (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Ohb | Beardsley (hornblendic) Member [of Harrison (Prospect) Gneiss] (Middle? Ordovician) - Gray to dark-gray, medium-grained, lineated gneiss |
| Ohc | Hawley Formation (carbonaceous schist facies) (Middle Ordovician) - Gray, rusty-weathering, fine- to medium-grained, generally layered schist and granofels, composed of quartz, oligoclase, and biotite; some muscovite and graphite, rare garnet and kyanite or sillimanite. Layers of quartz-spessartine rock (coticule) common |
| Ohn | Nodular member [of Harrison Gneiss] (Middle? Ordovician) - Harrison Gneiss containing prominent quartz-sillimanite nodules |
| Ohp | Pumpkin Ground (porphyritic) Member [of Harrison (Prospect) Gneiss] (Middle? Ordovician) - Medium- to light-gray, medium- to coarse-grained, well-layered and foliated gneiss, composed of oligoclase, microcline, quartz, and biotite; some layers have numerous microcline megacrysts 1 to 5 cm across; others have hornblende. Minor layers of garnetiferous schist and gneiss |
| Ol | Litchfield Norite (Middle? Ordovician) - Dark, medium- to coarse-grained, mostly massive mafic rock (olivine norite, quartz norite, hypersthene pyroxenite), composed of labradorite, hypersthene, augite, and olivine in varying proportions, also hornblende and biotite (and minor quartz in quartz norite). Associated with small mineral deposits of pyrrhotite, pentlandite, and chalcopyrite |
| Om | Middletown Formation ( = Ammonoosuc Volcanics of New Hampshire) (Middle Ordovician) - Heterogeneously interlayered dark- to light-gray, generally medium grained gneiss and granofels, ranging from quartz-biotite gneiss through felsic amphibolite gneiss to amphibolite and characteristically containing anthophyllite or cummingtonite with or without hornblende. Also layers of calc-silicate rock and of biotite gneiss with quartz-sillimanite nodules |
| Om? | Middletown Formation - see Om (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Oma | Maltby Lakes Metavolcanics (Middle? Ordovician) - Green to gray-green, fine-grained, massive to well-foliated and layered greenstone, greenschist, and schist; also dark amphibolite to west and southwest |
| Omal | Lower part [of Maltby Lakes Metavolcanics] (Middle? Ordovician) - Gray-green to green, fine-grained, generally well foliated greenschist, greenstone, and schist or phyllite, composed of albite and chlorite, plus quartz and sericite or epidote and actinolite, mixed metavolcanic and metasemidentary rocks |
| Omau | Upper part [of Maltby Lakes Metavolcanic] (Middle? Ordovician) - Green to gray-green, fine-grained, layered and foliated to massive greenstone and greenschist, composed of epidote, albite, actinolite, and chlorite, and locally minor quartz, sericite, garnet, pyrite, or calcite. Mainly metavolcanic |
| Oml | Lower member [of Middletown Formation] (Middle Ordovician) - Dark- to medium-gray amphibolite and hornblende gneiss, commonly with garnet, diopside, or epidote, interlayered with light-gray gneiss composed of oligoclase, quartz, biotite, and generally one or more amphiboles, also garnet |
| Omm | Massive mafic rock [in Middletown Formation] (Middle Ordovician) - Dark, coarse-grained, massive amphibolite and metagabbro, composed of hornblende and plagioclase; in places with quartz and epidote, in others with patches of actinolite or anthophyllite, chlorite, and epidote or garnet. May be intrusive |
| Omo | Monson Gneiss (may be equivalent to part of Waterford Group) (Middle or Lower Ordovician?) - Interlayered light to dark, mostly medium to coarse-grained gneiss and amphibolite; gneiss composed of plagioclase, quartz and biotite, with hornblende in some layers and microcline in others; traces of garnet, epidote, and magnetite |
| Omu | Upper member [of Middletown Formation] (Middle Ordovician) - Light-gray, generally rusty weathering, well-layered gneiss and granofels, composed of oligoclase, quartz, biotite, and amphibole (cummingtonite, anthophyllite, gedrite, or hornblende, or several of these), also garnet and chlorite. Many layers of amphibolite and biotite gneiss throughout |
| Oo | Oronoque Schist (Lower? Ordovician) - Gray to silver, medium- to fine-grained, well-layered to laminated schist and granofels, composed of quartz, oligoclase or albite, muscovite or sericite, biotite or chlorite, and in western belt local garnet, staurolite, and kyanite. Small lenses of amphibolite or greenstone |
| Op | Preston Gabbro (Middle Ordovician or older) - Dark, medium- to coarse-grained, mainly massive gabbro, composed of labradorite, augite, and opaques, generally with hornblende, locally hypersthene or olivine or both |
| Op+Oq | Preston Gabbro and Quinebaug Formation undivided - see Op and Oq |
| Opd | Dioritic phase [of Preston Gabbro] (Middle Ordovician or older) - Medium- to dark-gray, streaked or speckled, medium-grained diorite and quartz diorite, gneissic where sheared near contact, composed of plagioclase, hornblende, and biotite, and locally quartz and relic pyroxene |
| Oq | Quinebaug Formation (Middle Ordovician or older) - Medium- to dark-gray, commonly greenish, medium-grained, well-layered gneiss, composed of hornblende, andesine, biotite, and epidote, commonly with quartz or garnet, interlayered with amphibolite |
| Oqb | Black Hill Member [of Quinebaug Formation] (Middle Ordovician or older) - Gray, medium- to fine-grained, well-layered schist and granofels, composed of oligoclase, quartz, and biotite, commonly with hornblende or muscovite, and locally with calcite, garnet, or epidote |
| Oqf | Felsic gneiss member [of Quinebaug Formation] (Middle Ordovician or older) - Light- to medium-gray, fine- to medium-grained gneiss, composed of plagioclase, quartz, biotite, and muscovite, commonly with K-feldspar |
| Or | Ratlum Mountain Schist (Lower? Ordovician) - Gray, medium-grained, interlayered schist and granofels, composed of quartz, oligoclase, muscovite (in the schist), biotite, and garnet, also staurolite and kyanite in the schist. Numerous layers and lenses of amphibolite; also some of quartz-spessartine (coticule) and calc-silicate rock |
| Or+Ora | Ratlum Mountain Schist and Amphibolite unit in Ratlum Mountain Schist undivided - see Or and Ora |
| Or? | Ratlum Mountain Schist - see Or (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Ora | Amphibolite unit [in Ratlum Mountain Schist] (Lower? Ordovician) - Black or mottled, generally massive amphibolite and hornblende gneiss, composed of hornblende and andesine, commonly with minor quartz and magnetite, and locally with garnet, biotite, and epidote |
| Ose | Units e and d [of Strockbridge Marble] (Lower Ordovician) - White to gray massive calcite marble, commonly mottled with dolomite and locally interlayered with dolomite marble and calcareous siltstone and sandstone |
| Osg | Units g and f [of Strockbridge Marble] (Lower Ordovician) - White to gray massive calcite marble with layers and laminae of dolomitic marble |
| Ot | Taine Mountain Formation (Lower? Ordovician) - Gray, medium-grained, generally fairly well layered to well-laminated ('pin-stripe') gneissic or schistose granofels, composed of quartz, oligoclase, biotite, muscovite, and garnet, and locally staurolite and kyanite or sillimanite |
| Ot+Oc | Taine Mountain and Collinsville Formation undivided - see Ot and Oc |
| Ota | Tatnic Hill Formation (Upper? and Middle Ordovician) - Medium- to dark-gray, medium-grained gneiss or schist composed of quartz, andesine, biotite, garnet, and sillimanite, locally kyanite, muscovite, or K-feldspar, interlayered with locally mappable units and thinner layers of rusty-weathering graphitic pyrrhotitic two-mica schist, amphibolite, and calc-silicate rock |
| Otaf | Fly Pond (calc-silicate) Member [of Tatnic Hill Formation] (Upper? and Middle Ordovician) - Light-gray, medium-grained, layered to massive calc-silicate gneiss, composed of andesine, quartz, hornblende or actinolite, epidote, and commonly diopside, biotite, and scapolite; some layers are calcitic |
| Otay | Yantic Member [of Tatnic Hill Formation] (Upper? and Middle Ordovician) - Medium- to dark-gray, fine- to medium-grained schist, composed of quartz, oligoclase, biotite, and muscovite, some layers with garnet, staurolite, and kyanite or garnet and sillimanite, local epidote or K-feldspar; some layers of rusty-weathering graphitic, pyrrhotitic, two-mica schist |
| Otb | Basal member [of Taine Mountain Formation] around Waterbury dome (Lower? Ordovician) - Differs from rest of Taine Mountain Formation in being especially well layered and generally less micaceous and schistose |
| Otf | Trap Falls Formation (may be equivalent in part to Golden Hill Schist) (Middle or Lower Ordovician) - Gray to silvery, partly rusty weathering, medium-grained, generally well layered schist, composed of quartz, sodic plagioclase, biotite, muscovite, and garnet, locally with sillimanite or kyanite, interlayered with two-mica gneiss and granulite and with amphibolite |
| Otf+Og | Trap Falls Formation and Ordovician? granitic gneiss undivided - see Otf and Og |
| Otfc | Carringtons Pond Member [of Trap Falls Formation] (Middle or Lower Ordovician) - Interlayered medium- to dark-gray, rusty-weathering, medium-grained schist and light-gray, fine- to medium-grained gneiss, composed of quartz, sodic plagioclase, biotite, muscovite, and garnet; schist locally contains sillimanite or kyanite; gneiss locally contains K-feldspar; amphibolite layers common |
| Otfg | Schist and granulite member [of Trap Falls Formation] (Middle or Lower Ordovician) - Interlayered gray to silvery, medium- to coarse-grained schist and fine-grained granofels, composed of quartz, sodic plagioclase, biotite, and muscovite; garnet common in schist |
| Otfs | Shelton (white gneiss) Member [of Trap Falls Formation] (Middle or Lower Ordovician) - White, light-gray, or buff, fine- to medium-grained, generally well foliated granitic gneiss, composed of sodic plagioclase, quartz, microcline, muscovite, and garnet (in tiny almost ubiquitous grains), also commonly minor biotite; generally interlayered with mica schist, biotite gneiss, and calc-silicate rock. Thought to be metavolcanic equivalent of unit Og |
| Ots | Scranton Mountain Member [of Taine Mountain Formation] (Lower? Ordovician) - Gray, rusty-weathering, medium-grained schist, composed of quartz, muscovite, biotite, plagioclase, garnet, and generally kyanite |
| Otw | Wildcat Member [of Taine Mountain Formation] (Lower? Ordovician) - Gray, medium-grained, generally fairly well layered to well-laminated ('pin-stripe') gneissic or schistose granofels, composed of quartz, oligoclase, biotite, muscovite, and garnet, and locally starolite and kyanite or sillimanite |
| Otwv | Whigville Member [of Taine Mountain Formation] (Lower? Ordovician) - Gray, medium-grained, generally fairly well layered to well-laminated ('pin-stripe') gneissic or schistose granofels, composed of quartz, oligoclase, biotite, muscovite, and garnet, and locally staurolite and kyanite or sillimanite |
| Ow | Walloomsac Schist (Middle Ordovician) - Black to dark-or silvery-gray, rarely layered schist or phyllite, composed of quartz, albite, and commonly garnet and staurolite or sillimanite (locally strongly retrograded to chlorite and muscovite). Locally feldspathic or calcareous near the base |
| Owm | Basal marble member [of Walloomsac Schist] (Middle Ordovician) - Dark-gray to white, massive to layered schistose or phyllitic calcite-phlogopite marble |
| Pn | Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite and accessory muscovite and magnetite. Considerable associated pegmatite |
| Pnm | Mafic phase [of Narragansett Pier Granite] (Permian) - Gray to reddish, medium-grained, generally massive granite, like Pn but with more biotite and locally hornblende |
| Pp | Porphyry (dacite or rhyolite) (Permian) - Light-colored, very fine grained, massive porphyry with phenocrysts of quartz, feldspar, and biotite; muscovite and accessory fluorite in ground mass |
| Ppa | Pinewood Adamellite (Permian) - Light-gray, medium-grained, massive adamellite, composed of microcline, albite, quartz, and muscovite with accessory fluorite. High radioactivity |
| Ps | Syenite (Permian) - Medium-gray, massive syenite, composed of microcline, amphibole (arfvedsonite), and biotite with accessory apatite and sphene |
| Pw | Westerly Granite (Permian) - Light-gray, pink-weathering, fine-grained, massive, aplitic granite, composed of oligoclase or albite, quartz, and K-feldspar, with minor biotite and accessory muscovite, magnetite, allanite, and sphene |
| Pzmy | Mylonite along Paleozoic faults (Upper or Middle Paleozoic) - Mylonite, blastomylonite, and blastomylonitic gneiss, composed of intensely granulated quartz, plagioclase, biotite, and epidote, in places with hornblende or microcline and commonly with secondary minerals. In places has later been silicified (compare unit Jsi) |
| SObl | Lower member [of Bigelow Brook Formation] (Silurian or Ordovician or both) - Chiefly gray, medium-grained, well-layered granofels, composed of quartz, oligoclase, and biotite, commonly with garnet and sillimanite, interlayered with thinly fissile sillimanitic, graphitic, pyrrhotitic biotite schist and with calc-silicate rock |
| SObm | Middle member [of Bigelow Brook Formation] (Silurian and perhaps Ordovician) - Greenish-gray, medium-grained calc-silicate rock, composed of plagioclase, quartz, and diopside (locally hornblende and scapolite), interbedded with schist and granofels composed of plagioclase, quartz, biotite, and commonly garnet and sillimanite |
| SObu | Upper member [of Bigelow Brook Formation] (Silurian and perhaps Ordovician) - Chiefly gray, rusty-weathering, medium-grained, generally well layered and locally fissile schist, composed of plagioclase, quartz, biotite, garnet, and sillimanite, locally with K-feldspar or cordierite, fissile layers commonly with graphite and pyrrhotite, interlayered with quartzose granofels with less biotite but with calc-silicate minerals |
| SOh | Hebron Gneiss (Silurian and Ordovician) - Interlayered dark-gray, medium- to coarse-grained schist, composed of andesine, quartz, biotite, and local K-feldspar, and greenish-gray, fine- to medium-grained calc-silicate rock, composed of labradorite, quartz, biotite, actinolite, hornblende, and diopside, and locally scapolite. Local lenses of graphitic two-mica schist |
| SOs | Southbridge Formation (Silurian or Ordovician or both) - Dark- to light-gray, locally rusty, fine- to medium-grained interlayered granofels and schist, composed of quartz, plagioclase, and biotite, with muscovite in schist and amphibole, calc-silicate minerals, or K-feldspar in certain layers; also locally mappable units and thinner layers of calc-silicate rock, amphibolite, and sillimanite-garnet and sillimanite-graphite-pyrrhotite schist |
| SOs? | Southbridge Formation - see SOs (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| SOsp | Porphyritic member [of Southbridge Formation] (Silurian or Ordovician or both) - Light-to medium-gray, fine-grained porphyritic massive to layered gneiss, composed of quartz, oligoclase, microcline, and biotite, with megacrysts 1 to 2 cm long of microcline |
| Sbc | Clough Quartzite (Silurian) - White, medium-grained, glassy to granular, well-layered quartzite and muscovitic quartzite, locally with garnet; conglomeratic (commonly with tourmaline) in lower part |
| Sbf | Fitch Formation (Silurian) - Gray, fine- to medium-grained calc-silicate rock, composed of quartz, biotite, calcite, actinolite, diopside, microcline, and locally garnet, scapolite, or epidote, interlayered with two-mica schist |
| Stb | Basal member [of The Straits Schist] ( = Russell Mountain Formation of Massachusetts) (Silurian) - Distinguished by presence of layers of amphibolite, marble, calc-silicate rock, and quartzite within more uniform schist like that on either side. Minor, unevenly distributed mineralization in W, Bi, Cu, Ni, and other metals |
| TRnh | New Haven Arkose (Upper Triassic; possibly Lower Jurassic at top) - Red, pink, and gray coarse-grained, locally conglomeratic, poorly sorted and indurated arkose, interbedded with brick-red micaceous, locally shaly siltstone and fine-grained feldspathic clayey sandstone |
| TRnh+Jb | New Haven Arkose and Buttress Dolerite undivided - see TRnh and Jb |
| Yg | Gneiss of Highlands massifs, (including Fordham Gneiss) (Proterozoic Y; may contain some older rocks) - Mixture of rock types described below, where not separately mapped |
| Yga | Augen gneiss (including local term 'Danbury Gneiss', equivalent in part to Tyringham Gneiss of Massachusetts) (Proterozoic Y) - Medium-gray to spotted, fine- to medium-grained, porphyritic, foliated and lineated granitic gneiss, composed of microcline (largely as megacrysts or augen up to 10 cm long), quartz, albite, or oligoclase, biotite and minor hornblende |
| Ygh | Hornblende gneiss and amphibolite (Proterozoic Y) - Dark-gray to mottled, fine- to medium-grained, massive to foliated amphibolite and gneiss, composed of hornblende and plagioclase, also commonly biotite and minor quartz; commonly interlayered with banded felsic gneiss. Locally contains calc-silicate rock or diopsidic calcite marble |
| Ygn | Layered gneiss (Proterozoic Y) - Gray, medium-grained, well-foliated and generally well layered, light and dark, but locally wispy gneiss, composed of quartz and plagioclase, with microcline locally in the light layers and abundant biotite and common hornblende in the dark layers; garnet or epidote locally. Layers and lenses of calc-silicate rock and amphibolite in some areas |
| Ygr | Pink granitic gneiss (Proterozoic Y) - Light-pink to gray, medium- to coarse-grained, foliated but generally massive or poorly layered granitic gneiss, composed of quartz, microcline, oligoclase, and either biotite or muscovite or both, also locally amphibole or epidote |
| Ygs | Rusty mica schist and gneiss (equivalent in part to Washington Gneiss of Massachusetts) (Proterozoic Y; may contain some older rocks) - Dark-gray, rusty-weathering, well-foliated and well- to poorly layered schist and gneiss composed of quartz, plagioclase, biotite, muscovite, sillimanite, and locally garnet; some layers of feldspathic quartzite and garnetiferous amphibolite |
| Zl | Light House Gneiss (Proterozoic Z?) - Light-pink or gray to red, medium-grained, generally well foliated granitic gneiss, composed of K-feldspar, oligoclase, quartz, biotite, and magnetite, with local muscovite but no garnet |
| Zp | Plainfield Formation (Proterozoic Z?) - Interlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite, light- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline), medium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet, dark-gray or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside), amphibolite, diopside-bearing quartzite, and calc-silicate rock. In places contains quartz-sillimanite nodules |
| Zp+Zsc+Pn | Plainfield Formation, Stony Creek Granite Gneiss and Narragansett Pier Granite undivided - see Zp, Zsc and Pn |
| Zp+Zsph+Pn? | Plainfield Formation, Potter Hill Granite Gneiss and Narragansett Pier Granite undivided - see Zp, Zsph and Pn (? denotes uncertain identification of the formation, with the most closely associated formation symbol used for the map unit). |
| Zpq | Quartzite unit [in Plainfield Formation] (Proterozoic Z?) - Light-gray, glassy, generally thin bedded quartzite, also feldspathic and micaceous quartzite containing quartz-sillimanite nodules |
| Zpq+Zsc+Pn | Quartzite unit in Plainfield Formation, Stony Creek Granite Gneiss and Narragansett Pier Granite undivided - see Zpq, Zsc and Pn |
| Zsc+Pn | Stony Creek Granite Gneiss and Narragansett Pier Granite undivided - see Zsc and Pn |
| Zsh | Hope Valley Alaskite Gneiss (Proterozoic Z?) - Light-pink to gray, medium- to coarse-grained, locally porphyritic, variably lineated and foliated alaskitic gneiss, composed of microcline, quartz, albite or oligoclase, and minor magnetite, and locally biotite and muscovite. Lineation formed by rods of quartz. Locally contains quartz-sillimanite nodules |
| Zsp | Ponaganset Gneiss (Proterozoic Z?) - Dark-gray, coarse-grained, porphyritic, well-foliated gneiss, composed of oligoclase, quartz, microcline (mostly as megacrysts up to 8 cm long), biotite, magnetite, and generally hornblende; also garnet and muscovite where hornblende is absent |
| Zsph | Potter Hill Granite Gneiss (Proterozoic Z?) - Light-pink to gray, tan-weathering, fine- to medium-grained, rarely porphyritic, well-foliated (not lineated) granitic gneiss, composed of microcline, quartz, oligoclase (or albite), biotite, and magnetite, minor muscovite, and local garnet |
| Zsph+Pn | Potter Hill Granite Gneiss and Narragansett Pier Granite undivided - see Zsph and Pn |
| Zspp | Porphyritic phase [of Potter Hill Granite Gneiss] (Proterozoic Z?) - Light- to medium-gray, fine- to medium-grained, porphyritic, well-foliated (note lineated) granitic gneiss, composed of microcline (much of it as megacrysts up to 4 cm long), quartz, oligoclase, biotite, and magnetite |
| Zss | 'Scituate' Granite Gneiss (Proterozoic Z?) (probably not equivalent to type Scituate in Rhode Island, which is probably Devonian) - Light-pink to gray, medium- to coarse-grained, generally porphyritic, well-lineated and locally foliated granitic gneiss, composed of microcline, quartz, albite or orthoclase, biotite, hornblende, and magnetite. Megacrysts of microcline up to 3 cm long; lineation formed by splotches of biotite or by rods of quartz |
| Zw | Waterford Group (may be equivalent in part to Monson Gneiss) (Proterozoic Z?) - Interlayered part (but layers locally distinct) of Waterford Group, light to dark, generally medium grained gneiss, composed of plagioclase, quartz, and biotite, with hornblende in some layers and microcline in others. Some layers of amphibolite |
| Zw+Zb | Waterford Group and Branford Gneiss undivided - see Zw and Zb |
| Zw+Zsc+Pn | Waterford Group, Stony Creek Granite Gneiss and Narragansett Pier Granite undivided - see Zw, Zsc and Pn |
| Zwm | Mamacoke Formation (Proterozoic Z?) - Interlayered (but layers locally indistinct) light- to dark-gray, medium-grained gneiss, composed of plagioclase, quartz, and biotite; sillimanite, garnet, hornblende, or microcline in certain layers; in upper part locally contains quartz-sillimanite nodules or thin layers of quartzite, amphibolite, or calc-silicate rock |
| Zwn | New London Gneiss (Proterozoic Z?) - Massive, gray granodioritic gneiss, also interlayered light-gray gneiss and dark-gray amphibolite; gneiss generally medium grained; composed of oligoclase, quartz, biotite, and magnetite, also microcline in massive gneiss |
| Zwnj | Joshua Rock Member [of New London Gneiss] (Proterozoic Z?) (may include intrusive rocks of Ordovician age) - Medium-gray (weathers with red spots of hematite), medium-grained, foliated gneiss composed of microperthite, quartz, albite, aegerine-augite, and magnetite; rare riebeckite |
| Zwr | Rope Ferry Gneiss (Proterozoic Z?) - Interlayered (but layers commonly lenticular to indistinct) light- to dark-gray, fine- to medium-grained gneiss, composed of plagioclase, quartz, and biotite, with hornblende in some layers and microcline in others; local layers of amphibolite |
| l | Unmapped - Unmapped |
| u | Ultramafic rock (Ordovician or older) - Ultramafic rock, originally composed of olivine an pyroxene, now generally altered to tremolite, talc, chlorite, or serpentine |
Geologic Formation Name - The name of the geologic formation associated with the geologic unit. (Source: State of Connecticut, Department of Environmental Protection)
Geologic Description - A brief description of the geologic unit. (Source: State of Connecticut, Department of Environmental Protection)
Terrane Code - A geologic terrane code (alphanumeric) that denotes the map unit's associated geologic terrane. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Fault Related Rocks |
| 1 | Newark Terrane / Hartford and Pomperaug Mesozoic Basins |
| 2a | Proto-North American (Continental) Terrane / Ordovician and Cambrian Shelf Sequence |
| 2b | Proto-North American (Continental) Terrane / Proterozoic Massifs - "Grenville" |
| 3a | Iapetos (Oceanic) Terrane / Connecticut Valley Synclinorium |
| 3a/3b | Iapetos (Oceanic) Terrane / Connecticut Valley Synclinorium and Bronson Hill Anticlinorium |
| 3a/om | Iapetos (Oceanic) Terrane / Connecticut Valley Synclinorium / Orange Milford Belt |
| 3b | Iapetos (Oceanic) Terrane / Bronson Hill Anticlinorium |
| 3c | Iapetos (Oceanic) Terrane / Merrimack Synclinorium |
| 3d | Proto-North American (Continental) Terrane / Taconic Allochthons (Displaced Iapetos Terrane) |
| 4 | Avalonian (Continental) Terrane / Avalonian Anticlinorium |
| 99 | Unmapped |
Geologic Terrane - provides the explanation of the geologic terrane code. TERRANE is the English Equivalent of (decodes) the TERR_COD field. (Source: State of Connecticut, Department of Environmental Protection)
First Lithology - The primary lithology of the geologic unit. These lithologic values were determined from the short description of map units, with minor adjustments made from field observations. Simplified descriptions are given for rock terms used above. Descriptions include general and distinguishing characteristics of rocks as they commonly occur in Connecticut. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 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. |
| Diorite 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. |
| Granite 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. |
| 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. |
| Porphyry | Light-colored, fine-grained intrusive igneous rock with some conspicuously large crystals of quartz, feldspar, or biotite. |
| Quartz | Light-colored to gray, massive to layered, medium-grained metamorphic rock. Very hard and resistant; a metamorphosed sandstone composed primarily of quartz. |
| Quartzite | Light-colored to gray, massive to layered, medium-grained metamorphic rock. Very hard and resistant; a metamorphosed sandstone composed primarily of quartz. |
| 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. |
| Shale | Red to brown, locally gray to green, extremely fine-grained, strongly layered sedimentary rock composed of clay minerals; occurs in the Central Lowlands. |
| 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. |
| Unmapped | Unmapped |
Second Lithology - The second lithology of the geologic unit. These lithologic values were determined from the short description of map units, with minor adjustments made from field observations. Simplified descriptions are given for rock terms used above. Descriptions include general and distinguishing characteristics of rocks as they commonly occur in Connecticut. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Amphibolite | Dark-colored, fine-to coarse-grained, massive to poorly layered metamorphic rock containing amphibole and plagioclase with little or no quartz. |
| 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. |
| 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. |
| 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. |
| Mafic Rock | Dark-colored rock consisting of one or more dark (iron and magnesian) minerals as its major constituent. |
| 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. |
| Phylite | Silvery, gray to dark-gray, fine- to very fine-grained, schist-like metamorphic rock. |
| Quartzite | Light-colored to gray, massive to layered, medium-grained metamorphic rock. Very hard and resistant; a metamorphosed sandstone composed primarily of quartz. |
| 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. |
Third Lithology - The third lithology of the geologic unit. These lithologic values were determined from the short description of map units, with minor adjustments made from field observations. Simplified descriptions are given for rock terms used above. Descriptions include general and distinguishing characteristics of rocks as they commonly occur in Connecticut. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Amphibolite | Dark-colored, fine-to coarse-grained, massive to poorly layered metamorphic rock containing amphibole and plagioclase with little or no quartz. |
| 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. |
| 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. |
| Phylite | Silvery, gray to dark-gray, fine- to very fine-grained, schist-like metamorphic rock. |
| 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. |
Fourth Lithology - The fourth lithology of the geologic unit. These lithologic values were determined from the short description of map units, with minor adjustments made from field observations. Simplified descriptions are given for rock terms used above. Descriptions include general and distinguishing characteristics of rocks as they commonly occur in Connecticut. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 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. |
| Granitic Gneiss | Light-colored, medium- to coarse-grained, compositionally banded metamorphic rock of granitic composition. Quarried for use as dimension stone (see granite). |
| Quartzite | Light-colored to gray, massive to layered, medium-grained metamorphic rock. Very hard and resistant; a metamorphosed sandstone composed primarily of quartz. |
Fifth Lithology - The fifth lithology of the geologic unit. These lithologic values were determined from the short description of map units, with minor adjustments made from field observations. Simplified descriptions are given for rock terms used above. Descriptions include general and distinguishing characteristics of rocks as they commonly occur in Connecticut. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 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. |
Age - Denotes the geologic age of the mapping unit. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Cambrian | 500 - 570 million years ago |
| Cambrian / Proterozoic Z | 500-570/570-800 million years ago |
| Devonian | 360 - 410 million years ago |
| Devonian / Permian | 360-410/240-290 million years ago |
| Devonian / Silurian | 360-410/410-435 million years ago |
| Jurassic | 140 - 205 million years ago |
| Ordovician | 435 - 500 million years ago |
| Ordovician / Cambrian | 435-500/500-570 million years ago |
| Permian | 240 - 290 million years ago |
| Proterozoic Y | 800 - 1700 million years ago |
| Proterozoic Z | 570 - 800 million years ago |
| Silurian | 410 - 435 million years ago |
| Silurian / Ordovician | 410-435/435-500 million years ago |
| Triassic | 205 - 240 million years ago |
Geologic Time - Explains the range of dates for the geologic time period associated with the geologic age. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 140 - 205 mya | Jurassic (140 - 205 million years ago) |
| 205 - 240 mya | Triassic (205 - 240 million years ago) |
| 240 - 290 mya | Permian (240 - 290 million years ago) |
| 360-410/240-290 mya | Devonian / Permian (360-410/240-290 million years ago) |
| 360 - 410 mya | Devonian (360 - 410 million years ago) |
| 360-410/410-435 mya | Devonian / Silurian (360-410/410-435 million years ago) |
| 410 - 435 mya | Silurian (410 - 435 million years ago) |
| 410-435/435-500 mya | Silurian / Ordovician (410-435/435-500 million years ago) |
| 435 - 500 mya | Ordovician (435 - 500 million years ago) |
| 435-500/500-570 mya | Ordovician / Cambrian (435-500/500-570 million years ago) |
| 500 - 570 mya | Cambrian (500 - 570 million years ago) |
| 500-570/570-800 mya | Cambrian / Proterozoic Z (500-570/570-800 million years ago) |
| 570 - 800 mya | Proterozoic Z (70 - 800 million years ago) |
| 800 - 1700 mya | Proterozoic Y (800 - 1700 million years ago) |
Calculated area of polygon feature in acres. Note, ACREAGE values are not automatically updated after modifying feature geometry (shape). Values must be recalculated after features are edited, simplified, generalized, clipped, dissolved, etc. (Source: State of Connecticut, Department of Environmental Protection)
Calculated area of polygon feature in square miles. Note, AREA_SQMI values are not automatically updated after modifying feature geometry (shape). Values must be recalculated after features are edited, simplified, generalized, clipped, dissolved, etc. (Source: 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)
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.
79 Elm Street
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.
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 polygon features from Source 3 - Bedrock Geology (ArcInfo Coverage format). Bedrock Geology_Polygon.shp is in Shapefile format.
Bedrock_Geology_Poly 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 polygon feature data from ArcInfo Coverage named BEDROCK to a Shapefile named Bedrock_Geology_Poly.shp. Excluded the AREA, PERIMETER, BEDROCK#, BEDROCK-ID attributes from the Shapefile because their values are only maintained by ArcInfo software with data that is in ArcInfo Coverage format.
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Convert to GeoDatabase Feature Class format - Defined new Feature Class named Bedrock_Geology_Poly; and imported the attribute definitions, loaded features and imported metadata from Bedrock_Geology_Poly.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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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.
The horizontal positional accuracy of this data is unknown.
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.
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).
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.
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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.
| Data format: | in format Shapefile, Feature Class, ArcInfo Coverage (version ArcGIS) Size: 4.358 |
|---|---|
| Network links: | http://www.ct.gov/deep |
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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