This data layer includes the information portrayed on the Surficial Materials Map of Connecticut (Stone, J.R., Schafer, J.P., London, E.H. and Thompson, W.B., 1992, U.S. Geological Survey special map, 2 sheets, scale 1:125,000). The Surficial Materials Map of Connecticut portrays the glacial and postglacial deposits of Connecticut in terms of their aerial extent and subsurface textural relationships. Glacial Ice-Laid Deposits (thin till, thick till, end moraine deposits) and Postglacial Deposits (alluvium, swamp deposits, marsh deposits, beach deposits, talus, and artificial fill) are differentiated from Glacial Meltwater Deposits. The meltwater deposits are further characterized using four texturally-based map units (g = gravel, sg = sand and gravel, s = sand, and f = fines). In many places a single map unit (e.g. sand) is sufficient to describe the entire meltwater section. Where more complex stratigraphic relationships exist, "stacked" map units are used to characterize the subsurface (e.g. sg/s/f - sand and gravel overlying sand overlying fines). Where postglacial deposits overlie meltwater deposits, this relationship is also described (e.g. alluvium overlying sand). Map unit definitions (Surficial Materials Polygon Code definitions, found in the metadata) provide a short description of the inferred depositional environment for each of the glacial meltwater map units. This map was compiled at 1:24,000 scale, and published at 1:125,000 scale. Connecticut Surficial Materials is a 1:24,000-scale, polygon and line feature-based layer describing the unconsolidated glacial and postglacial deposits of Connecticut in terms of their grain-size distribution (texture) as compiled at 1:24,000 scale for the Surficial Materials Map of Connecticut. Glacial meltwater deposits (stratified deposits) are particularly emphasized because these sediments are the major groundwater aquifers in the State and are also the major source of construction aggregate. These deposits are described in terms of their subsurface distribution of textures as well as their extent. The texture of meltwater deposits through their total vertical thickness in the subsurface is shown to the extent that it is known or can be inferred. In some places only one textural unit (such as SG - Sand and Gravel) describes the whole vertical extent of the meltwater deposits; in other places 'stacked units' (such as SG/S/F - Sand and Gravel overlying Sand overlying Fines) indicate changes of textural units in the subsurface. Polygon features represent individual textural (surficial material) units with attributes that describe textural unit type and size. Examples of polygon features that are postglacial deposits include floodplain alluvium, swamp deposits, salt-marsh and estuarine deposits, talus, coastal beach and dune deposits, and artificial fill. Examples of glacial ice-laid deposits include till, thin till, thick till and end moraine deposits. Examples of glacial melt-water deposits include gravel, sand and gravel, sand, and very fine sand, silt and clay. Additional polygon features are incorporated to define surface water areas for streams, lakes, ponds, bays, and estuaries greater than 5 acres in size. Line features describe the type of boundary between individual textural units such as a geologic contact line between two different textural units or a linear shoreline feature between a textural unit and an adjacent waterbody. Data is compiled at 1:24,000 scale and is not updated.
GEOLOGIC DISCUSSION - The following text is excerpted from the text on sheet 1 of the Surficial Materials Map of Connecticut, Stone and others, 1992. It has been modified as necessary for use with the 1:24,000 scale digital data, and is not considered a valid substitute for the information found on the published map. For a more complete understanding of the geologic principles behind the Surficial Materials data it is advisable to consult the published map, which contains cross sections, diagrams and text not available in digital form. DISCUSSION OF SURFICIAL MATERIALS - The unconsolidated deposits overlying bedrock in Connecticut range from a few feet to several hundred feet in thickness. These earth materials significantly affect human development of the land. Most of the unconsolidated materials are deposits of continental glaciers that covered all of New England at least twice during the Pleistocene ice age. These glacial deposits are divided into two broad categories, glacial till and glacial stratified deposits. Till, the most widespread glacial deposit, was laid down directly by glacier ice and is characterized by a nonsorted matrix of sand, silt, and clay with variable amounts of stones and large boulders. Glacial meltwater deposits are concentrated in both small and large valleys and were laid down by glacial meltwater in streams and lakes in front of the retreating ice margin during deglaciation. These deposits are characterized by layers of well-sorted to poorly sorted gravel, sand, silt, and clay. Postglacial sediments, primarily floodplain alluvium and swamp deposits, make up a lesser proportion of the unconsolidated materials of Connecticut. Alluvium is largely reworked from glacial materials and has similar physical characteristics. The distribution of surficial (unconsolidated) materials that lie between the land surface (below the pedogenic soil) and the bedrock surface is shown on this map to the extent that it is known or can be inferred. The cross sections and the block diagram shown on the published map (Stone and others, 1992) illustrate the characteristic vertical distribution of glacial till, glacial meltwater deposits, and postglacial deposits encountered in Connecticut. The areal distribution of till and stratified deposits is related to the physiographic regions of the State: the eastern and western highlands and the central lowland. In highland areas, till is the major unconsolidated material, present as a discontinuous mantle of variable thickness over the bedrock surface. Till is thickest in drumlins and on the northwest slopes of hills. Glacial meltwater deposits that average 10-40 feet in thickness overlie the till in small upland valleys and commonly in north-sloping pockets between bedrock hills. In the central lowland, especially in the north half, glacial stratified deposits are the predominant surficial materials. These deposits generally overlie till; however, well logs indicate that in some places till is not present and the stratified deposits lie directly on bedrock. The extensive stratified deposits of the central lowland average 50-100 feet in thickness, and in the northern part they almost completely mask the till-draped bedrock surface. Postglacial materials locally overlie the glacial deposits throughout the State. Alluvium occurs on the floodplains of most streams and rivers. Swamp deposits occur in poorly drained areas. Talus occurs along the bases of steep bedrock cliffs, principally along the traprock ridges within the central lowland. Salt-marsh and estuarine deposits occur mainly along the tidal portions of streams and rivers entering Long Island Sound. Beach deposits occur along the shoreline of Long Island Sound. The units on this map delineate textural changes in the subsurface as well as areally at the surface. An earlier map at 1:125,000 scale of central Connecticut (Stone and others, 1979) shows only surface textural units; a separate map in the same series (Langer, 1979) shows subsurface deposits of fine-grained materials. Several previous 1:24,000-scale quadrangle maps in Connecticut show three-dimensional textural units and refer to them as 'superposed deposits' (see Stone, 1976 and Radway and Schnabel, 1976, as examples). On this map, the term 'stack unit' (Kempton, 1981) is used in place of superposed deposits. DISTRIBUTION OF TEXTURES IN GLACIAL MELTWATER DEPOSITS - The distribution of textural units is extrapolated from both point data (well and test-hole logs, gravel pits, and shovel holes) and from interpretation of landforms based on the principles of morphosequence deposition and systematic northward ice retreat (Koteff, 1974; Koteff and Pessl, 1981). These concepts provide a model by which grain-size distribution can be predicted from the morphology of a deposit, given primary data about the textures at specific points. A morphosequence is a package of sediments deposited contemporaneously by meltwater flowing from the glacier margin to a specific base level. Within a morphosequence, grain size decreases and sorting improves from the ice-marginal (proximal) end of a deposit downstream to the distal end. Landforms are transitional within a sequence as well, ranging from ice-contact forms (eskers, kettles, kames) at the head (proximal end) of a deposit to uncollapsed forms (delta-foreset slopes, lake-bottom plains, valley trains) downstream (distal end). Coarser grained sediments are associated with the proximal parts of morphosequences, finer grained sediments are associated with distal parts; given this principle, textural distribution can be mapped using point data that serve as controls. The relationship between textural variations and morphosequences is illustrated by a cross section on the published map, which shows the distribution of texture units in the northern Quinnipiac River valley. This north-south section transects seven chronologically numbered morphosequences. Dashed lines drawn to the six southern sequences represent the probable generalized surface gradients of the heads of these deposits, prior to collapse (due to melting of buried ice) and subsequent stream entrenchment. From north to south within each of these sequences, the textures grade from coarse- to fine-grained sediments and the topography changes from collapsed to non-collapsed landforms. The longitudinal and vertical relationships illustrated by this section are common in other valleys as well. Stack units similar to those on the section described above occur throughout the stratified deposits of Connecticut. Many deposits having similar superposition of materials of differing texture were produced by geologic processes that occurred repeatedly in time and space during the deglaciation of Connecticut. For example, the SG/S/F and S/F stack units commonly occur in glacial-lake deltas. The SG/F stack unit commonly results from fluvial meltwater (or postglacial stream) terrace deposition on slightly older lake bottom deposits. The F/SG and S/SG units commonly occur in the distal parts of morphosequences where the sand or fines overlap the collapsed, coarser, proximal parts of other (older) sequences. Many basic texture units (G, SG, S, F) likewise have broadly common origins. Units of gravel or sand and gravel often occur in the proximal parts of deposits, or were commonly laid down in glaciofluvial environments. Units of sand and fine-grained sediment are typically associated with distal parts of sequences and were usually laid down in lacustrine environments. THICKNESS OF MATERIALS - The thickness of surficial materials in Connecticut varies considerably because of such factors as the high relief of the bedrock surface, changing conditions of deposition during deglaciation, and various effects of postglacial erosion and removal of glacial sediments. For more information on the thickness of deposits and the point data used to determine stacked units, it is beneficial to review the complete and figures on the published map. DESCRIPTION OF MAP UNITS GLACIAL ICE-LAID DEPOSITS - Glacial ice-laid deposits (tills) consist of nonsorted, generally nonstratified mixtures of grain-sizes ranging from clay to large boulders. The matrix of most tills is composed dominantly of sand and silt. Boulders within and on the surface of tills range from sparse to abundant. Some tills contain lenses of sorted sand and gravel and, less commonly, masses of laminated fine-grained sediments. The color and lithology of till vary across Connecticut, but generally reflect the composition of the local underlying and northerly adjacent bedrock from which the till was derived. Till blankets the bedrock surface in variable thickness, ranging from 0 to about 200 ft, and commonly underlies stratified meltwater deposits. Tills deposited during two separate glaciations occur in superposition within Connecticut (Pessl and Schafer, 1968). The upper till was deposited during the last (late Wisconsinan) glaciation; it is the most extensive till and is commonly observed in surface exposures, especially in areas where till thickness is less than 15 ft; it is described in the thin till unit description below. The lower till or 'old' till was deposited during an earlier glaciation (probably Illinoian). The lower till has a more patchy distribution; it is principally a subsurface deposit, generally overlain by upper till, and therefore not shown as a separate map unit; the lower till does however constitute the bulk of material in the areas where till thickness is greater than 15 ft; it is described in the thick till unit description below. In all two-till exposures, the base of the upper till truncates the weathered surface of the old till. The lower part of the upper till commonly displays a zone of shearing, dislocation, and brecciation in which clasts of lower till are mixed and incorporated into the upper till. End moraine deposits occur principally in southeastern Connecticut. These deposits were laid down by ablation processes along active ice margins during retreat of the last (late-Wisconsinan) ice sheet. Glacial Ice-Laid deposits include Thin till (T), Thick till (TT), and End moraine deposits (TS). GLACIAL MELTWATER DEPOSITS - Glacial meltwater deposits (stratified deposits) consist of layers of well-sorted to poorly sorted gravel, sand, silt, and clay laid down by flowing meltwater in glacial lakes and streams which occupied the valleys and lowlands of Connecticut during retreat of the last ice sheet. Textural variations within the meltwater deposits occur both areally and vertically because meltwater-flow regimes were different in glaciofluvial (stream), glaciodeltaic (where a stream entered a lake), and glaciolacustrine (lake bottom) depositional environments. Grain-size variations also resulted from meltwater deposition in positions either proximal to or distal from the retreating glacier margin, which was the principal sediment source. A common depositional scenario contained a proximal, ice-marginal meltwater stream in which horizontally bedded glaciofluvial gravel and/or sand and gravel were laid down; farther down valley, the stream entered a glacial lake where glaciodeltaic sediments were deposited consisting of horizontally layered sand and gravel delta-topset beds overlying inclined layers of sand in delta-foreset beds. Farther out in the glacial lake, glaciolacustrine very fine sand, silt, and clay settled out on the lake bottom in flat-lying, thinly bedded layers. Mappable textural variations are present in the vertical section of meltwater deposits in many places. This stacking of textural units commonly resulted from locally changing conditions of meltwater deposition. For example, glacial lakes drained upon ice retreat from particular positions. This may have been followed locally by distal glaciofluvial (stream) deposition from ice positions farther up valley. The resulting vertical section shows meltwater terrace sediments consisting of horizontally bedded fluvial sand and gravel which overlie lake-bottom sediments of very fine sand, silt and clay (shown as unit SG/F on the map). In other places glaciodeltaic deposition over an extended period of time in a particular glacial lake caused deltaic deposits (sand and gravel topset beds over sand foreset beds, unit SG/S) to prograde farther out into the lake and to overlie lake-bottom sediments; such deposits are shown as stack unit SG/S/F on the map. Meltwater deposits are shown on this map as four basic units: gravel, sand and gravel, sand, and fines. Grain-size terminology used to define the textural range within these units is modified from Wentworth, 1922. Stack units are also shown; these are combinations of the four basic units in various orders of superposition. The map units described below show the texture of meltwater deposits through the total vertical section to the extent that it is known or can be reasonably inferred. In some places only one textural unit (such as unit SG) describes the entire vertical thickness of the meltwater deposits. In other places stack units (such as units SG/S/F or S/F) indicate changes of textural units in the subsurface. Common depositional environments for each textural unit are given in parentheses after each unit description. Glacial meltwater deposits are represented by the following categories. Fine deposits include Fines (F). Coarse deposits include Gravel (G), Sand and Gravel (SG), and Sand (S). Stacked Coarse deposits include Gravel overlying Sand and Gravel (G/SG), Gravel overlying Sand (G/S), Sand and Gravel overlying Sand (SG/S), Sand and Gravel overlying Sand overlying Sand and Gravel (SG/S/SG), Sand overlying Gravel (S/G), and Sand overlying Sand and Gravel (S/SG). Stacked Coarse Deposits Overlying Fine deposits include Gravel overlying Sand overlying Fines (G/S/F), Gravel overlying Fines (G/F), Sand and Gravel overlying Sand overlying Fines (SG/S/F), Sand and Gravel overlying Fines (SG/F), and Sand overlying Fines (S/F). POSTGLACIAL DEPOSITS include Floodplain alluvium (A), Alluvium overlying undifferentiated coarse deposits (A/SG), Alluvium overlying Sand (A/S), Alluvium overlying Fines (A/F), Alluvium overlying undifferentiated coarse deposits overlying Fine deposits (A/SG/F), Alluvium overlying Sand overlying Fines (A/S/F), Alluvium overlying undifferentiated Fine deposits overlying coarse deposits (A/F/SG), Alluvium overlying Fines overlying Sand (A/F/S), Swamp deposits (SW), Swamp deposits overlying undifferentiated coarse deposits (SW/SG), Swamp deposits overlying Sand (SW/S), Swamp deposits overlying Fines (SW/F), Swamp deposits overlying Sand overlying undifferentiated coarse deposits (SW/S/SG), Swamp deposits overlying sand overlying Fines (SW/S/F), Swamp deposits overlying Fines overlying Sand (SW/F/S), Salt-marsh and tidal-marsh deposits (SM), Salt-marsh and tidal-marsh deposits overlying Sand (SM/S), Salt-marsh and tidal-marsh deposits overlying Fines (SM/F), Salt-marsh and tidal-marsh deposits overlying Sand overlying Fines (SM/S/F), Talus (TA), Beach deposits (B), and Artificial Fill (AF). REFERENCES Deane, R.E., 1967, The surficial geology of the Hartford South quadrangle, with map: Connecticut Geological and Natural History Survey Quadrangle Report 20, 43 p. Haeni, F.P., and Anderson, H.R., 1980, Hydrogeologic data for south-central Connecticut: Connecticut Water Resources Bulletin 32,43 p. Kempton, J.P., 1981, Three-dimensional geologic mapping for environmental studies in Illinois: Illinois Geological Survey Environmental Geology Note 100, 43 p. Koteff, Carl, 1974, The morphologic sequence concept and deglaciation of southern New England, in Coates, D.R., ed., Glacial geomorphology: Binghamton, N.Y., State University of New York, Publications in Geomorphology, p. 121-144. Koteff, Carl, and Pessl, Fred, Jr., 1981, Systematic ice retreat in New England: U.S. Geological Survey Professional Paper 1179, 20 p. Langer, W.H., 1979, Map showing distribution and thickness of the principal fine-grained deposits, Connecticut Valley urban area, central New England: U.S. Geological Survey Miscellaneous Investigations Series Map I-1074-C, scale 1:125,000. Mazzaferro, D.L., 1973, Hydrogeologic data for the Quinnipiac River basin, Connecticut: Connecticut Water Resources Bulletin 26, 54 p. Pessl, Fred, Jr., and Schafer, J.P., 1968, Two-till problem in Naugatuck-Torrington area, western Connecticut, in Orville, P.M., ed., New England Intercollegiate Geological Conference 60th Annual Meeting, New Haven, Conn., Oct. 25-27, 1968, Guidebook for fieldtrips in Connecticut: Connecticut Geological and Natural History Survey Guidebook 2, Trip B-1, 25 p. Radway, J.A., and Schnabel, R.W., 1976, Map showing unconsolidated materials, Avon quadrangle, Connecticut: U.S. Geological Survey Miscellaneous Field Studies Map MF-514-C, scale 1:24,000. Ryder, R.B., and Weiss, L.A., 1971, Hydrogeologic data for the Upper Connecticut River basin, Connecticut: Connecticut Water Resources Bulletin 26, 54 p. Stone, J.R., 1976, Map showing unconsolidated materials, Windsor Locks quadrangle, Connecticut: U.S. Geological Survey Miscellaneous Field Studies Map MF-450-E, scale 1:24,000. Stone, J.R., London, E.H., and Langer, W.H., 1979, Map showing textures of unconsolidated materials, Connecticut Valley urban area, central New England: U.S. Geological Survey Miscellaneous Investigations Series Map I-1074-B, scale 1:125,000. Wentworth, C.K. 1922, A scale of grade and class terms for clastic sediments: Journal of Geology, v. 30, p. 377-392.
Publication date of 1:125,000-scale Surficial Materials Map of Connecticut, Stone and others, 1992.
Polygon features represent individual textural (surficial material) units (Source: U.S. Geological Survey and State of Connecticut, Department of Environmental Protection)
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
Surficial Materials Polygon Code - A key field used to classify surficial materials units. Attribute values are mostly single characters in length, except for stacked map units that include forward slashes (/) between the different textural types such as A/F, A/F/G, and A/F/SG. (Source: U.S. Geological Survey and State of Connecticut, Department of Environmental Protection)
Floodplain Alluvium - Sand, gravel, silt, and some organic material, on the floodplains of modern streams. The texture of alluvium commonly varies over short distances both laterally and vertically, and is often similar to the texture of adjacent glacial deposits. Along smaller streams, alluvium is commonly less than 5 ft thick. The most extensive deposit of alluvium on the map is along the Connecticut River where the texture is predominantly fine to very fine sand and silt; here and along other larger rivers, it may be as much as 25 ft thick. Alluvium typically overlies thicker glacial stratified deposits, the general texture of which is indicated by the stacked unit.
Alluvium overlying Fines
Alluvium overlying Fines overlying Gravel
Alluvium overlying Fines overlying Sand
Alluvium overlying undifferentiated Fine deposits overlying coarse deposits (Sand and Gravel)
Alluvium overlying Sand
Alluvium overlying Sand overlying Fines
Alluvium overlying Sand overlying Sand and Gravel
Alluvium overlying undifferentiated coarse deposits (Sand and Gravel)
Alluvium overlying undifferentiated coarse deposits (Sand and Gravel) overlying Fine deposits
Alluvium overlying Sand and Gravel overlying Sand
Alluvium overlying Sand and Gravel overlying Sand overlying Fines
Artificial Fill - Earth materials and manmade materials that have been artificially emplaced. Artificial fill is common throughout the map area but has been shown on this map only where extensive areas of 'made land' occur, principally along the coast.
Beach deposits - Sand and and gravel deposited along the shoreline by waves and currents and by wind action. The texture of beach deposits varies over short distances and is generally controlled by the texture of nearby glacial materials exposed to wave action. Beach deposits are generally well sorted and rarely more than a few feet thick. Many sand beaches along the Connecticut coast have been 'restored'; these have not been distinguished from natural beaches on this map; however, extensive beaches that consist totally of 'made-land' are mapped as artificial fill.
Fines (very fine sand, silt, and clay) - Composed of well-sorted, thin layers of alternating silt and clay, or thicker layers of very fine sand and silt. Very fine sand commonly occurs at the surface and grades downward into rhythmically bedded silt and clay varves (lake-bottom deposits)
Fines overlying Gravel
Fines overlying Sand-- Fines of variable thickness, commonly in thinly bedded layers overlie sand of variable thickness (distal lake-bottom deposits overlying slightly older more delta-proximal lacustrine sediment)
Fines overlying Sand and Gravel - Fines of variable thickness, commonly in thinly bedded layers overlie sand and gravel of ariable thickness (lake-bottom deposits overlying slightly older collapsed proximal fluvial or deltaic deposits); in a few places sand or sand and gravel, generally less than 25 ft thick occurs on top of the F/SG unit and is indicated as S/F/SG and SG/F/SG on the map, respectively
Gravel - Composed mainly of gravel-sized particles; cobbles and boulders predominate; minor amounts of sand within gravel beds, and sand comprises few separate layers. Gravel layers generally are poorly sorted and bedding commonly is distorted and faulted due to postdepositional collapse related to melting of ice. Gravel deposits are shown only where observed in the field; additional gravel deposits may be expected, principally in areas mapped as unit SG (proximal fluvial deposits or delta-topset beds)
Gravel overlying Fines - Gravel is generally less than 20 ft thick, horizontally bedded and overlies thicker thinly bedded fines (proximal fluvial deposits overlying lake-bottom sediments)
Gravel overlying Sand-- Gravel is generally less than 20 ft thick, horizontally bedded, and overlies thicker, inclined layers of sand (proximal deltaic deposits)
Gravel overlying Sand overlying Fines - Gravel is generally less than 20 ft thick, horizontally bedded and overlies thicker inclined beds of sand which in turn overlie fines of variable thickness (proximal deltaic deposits overlying lake-bottom sediments)
Gravel overlying Sand and Gravel - Gravel is generally less than 20 ft thick, horizontally bedded, and overlies thicker, inclined layers of sand and gravel (proximal deltaic deposits)
Gravel overlying Sand and Gravel overlying Sand
Sand - Composed mainly of very coarse to fine sand, commonly in well-sorted layers. Coarser layers may contain up to 25 percent gravel particles, generally granules and pebbles; finer layers may contain some very fine sand, silt, and clay (delta-foreset beds, very distal fluvial deposits, or windblown sediment)
Sand overlying Fines - Sand is of variable thickness, commonly in inclined foreset beds and overlies thinly bedded fines of variable thickness (distal deltaic deposits overlying lake-bottom sediment)
Sand overlying Fines overlying Sand and Gravel
Sand overlying Gravel - Sand of variable thickness overlies gravel of variable thickness (younger distal deltaic or fluvial sediments overlying older, more proximal fluvial or deltaic sediments)
Sand overlying Sand and Gravel - Sand of variable thickness overlies sand and gravel of variable thickness (distal deltaic or fluvial sediments overlying slightly older proximal fluvial or deltaic sediments)
Sand and gravel - Composed of mixtures of gravel and sand within individual layers and as alternating layers. Sand and gravel layers generally range from 25 to 50 percent gravel particles and from 50 to 75 percent sand particles. Layers are well to poorly sorted; bedding may be distorted and faulted due to postdepositional collapse. It is likely that some deposits within this map unit actually are gravel or sand and gravel overlying sand. It is less likely that some of these deposits are sand (fluvial deposits or delta-topset beds)
Sand and Gravel overlying Fines - Sand and gravel is generally less than 20 ft thick, horizontally bedded and overlies thicker thinly bedded fines (fluvial meltwater terrace deposits overlying lake-bottom sediment)
Sand and Gravel overlying Fines overlying Sand and Gravel
Sand and Gravel overlying Sand - Sand and gravel is generally less that 20 ft thick, horizontally bedded, and overlies thicker, inclined layers of sand (deltaic deposits)
Sand and Gravel overlying Sand overlying Fines - Sand and gravel is generally less than 20 ft thick, horizontally bedded and overlies thicker inclined beds of sand which in turn overlie thinly bedded fines of variable thickness (deltaic deposits overlying lake-bottom sediment)
Sand and Gravel overlying Sand overlying Sand and Gravel - Sand and gravel is generally less than 20 ft thick, horizontally bedded, and overlies thicker inclined layers of sand; thickness of sand and gravel at the base of the section is variable (deltaic deposits overlying slightly older, more proximal deposits)
Salt-marsh and tidal-marsh deposits - Peat and muck interbedded with sand and silt, deposited in environments of low wave energy along the coast and in river estuaries. Marsh deposits are dominantly peat and muck, generally a few feet to 35 ft thick. In the major estuaries marsh deposits may overlie estuarine deposits which are sand and silt with minor organic material as much as 40 - 90 ft thick. These deposits are generally underlain by the glacial material shown adjacent on the map; either till or sand and gravel. Where they are known or inferred to be underlain by sand or fines, they are shown on the map by stacked units.
Salt-marsh and tidal-marsh deposits overlying Fines
Salt-marsh and tidal-marsh deposits overlying Sand overlying Fines
Swamp deposits - Muck and peat that contain minor amounts of sand, silt, and clay, accumulated in poorly drained areas. Most swamp deposits are less than about 10 ft thick. Swamp deposits are underlain by glacial deposits or bedrock. They are often underlain by glacial till even where they occur within glacial meltwater deposits. Where swamp deposits are known or inferred to be underlain by sand and/or fines, they are shown on the map by the stacked unit.
Swamp deposits overlying Fines
Swamp deposits overlying Fines overlying Sand
Swamp deposits overlying Sand
Swamp deposits overlying Sand overlying Fines
Swamp deposits overlying Sand overlying undifferentiated coarse deposits (Sand and Gravel)
Swamp deposits overlying undifferentiated coarse deposits (Sand and Gravel)
Thin Till - areas where till is generally less than 10-15 ft thick and including areas of bedrock outcrop where till is absent. Predominantly upper till; loose to moderately compact, generally sandy, commonly stony. Two facies are present in some places; a looser, coarser-grained ablation facies, melted out from supraglacial position; and a more compact finer-grained lodgement facies deposited subglacially. In general, both facies of upper till derived from the red Mesozoic sedimentary rocks of the central lowland of Connecticut are finer-grained, more compact, less stony and have fewer surface boulders than upper till derived from crystalline rocks of the eastern and western highlands.
Talus - Loose, angular blocks (mostly boulders) accumulated by rockfall at the bases of steep bedrock cliffs. Talus forms steep unstable slopes and is generally less than 10 ft thick. It occurs most extensively along the linear basalt and diabase ridges within the central lowland.
Sandy Till, Sand and Gravel, some areas of dense surface bolders (End moraine deposits) - Composed predominantly of ablation facies sandy upper till; lenses of stratified sand and gravel occur locally within the till. Surface boulders on end moraine deposits are generally more numerous than on adjacent till surfaces; dense concentrations of boulders are present in some places. Deposits occur as free-standing hummocky landforms, commonly in elongate ridges that trend NNE - SSW, and range in thickness from 10 to 60 ft.
Thick Till - areas where till is greater than 10-15 ft thick and including drumlins in which till thickness commonly exceeds 100 ft (maximum recorded thickness is about 200 ft). Although upper till is the surface deposit, the lower till constitutes the bulk of the material in these areas. Lower till is moderately to very compact, and is commonly finer-grained and less stony than upper till. An oxidized zone, the lower part of a soil profile formed during a period of interglacial weathering, is generally present in the upper part of the lower till. This zone commonly shows closely-spaced joints that are stained with iron and manganese oxides.
Water - Defined as streams, lakes, ponds, bays, and estuaries greater than 5 acres in size. Surficial Material water polygon features are outlined by Surficial Material line features with a SMARC_COD attribute value of 2 (for Hydrography Shoreline).
Surficial Materials - The SURFM_POLY attribute includes longer text values for the mostly single-character values stored in the SMPOLY_COD field. SURFM_POLY is the English language equivalent of (decodes) the SMPOLY_COD field. For example, SMPOLY_COD and SURFM_POLY attribute values for the same polygon feature are G and Gravel, respectively. SURFM_POLY attribute values for stacked map units include forward slashes (/) between the different textural types such as Aluv/Fines, Aluv/Fines/Gravel, and Alluv/Fines/Sand+Gravel. (Source: U.S. Geological Survey and State of Connecticut, Department of Environmental Protection)
Surficial Materials Description - Based on the SMPOLY_COD attribute, a longer decoded description of the map unit than that provided by the SURFM_POLY attribute. For example, SMPOLY_COD, SURFM_POLY, and DESCRIP attribute values for the same polygon feature are A/S, Aluv/Sand, and Aluvium overlying Sand, respectively. (Source: U.S. Geological Survey and State of Connecticut, Department of Environmental Protection)
Internet Mapping Software Legend - A text field used to classify and symbolize surficial material polygon features into broad categories, more suitable for use with Internet mapping applications. The IMS_LEGEND attribute condenses the 50 surficial materials map units (SMPOLY_COD values) into 11 broad textural categories of deposits (artificial fill, natural post glacial, fine, coarse, stacked coarse, coarse over fine, fine over coarse, till, thick till, end moraine, and water). (Source: U.S. Geological Survey and State of Connecticut, Department of Environmental Protection)
This category includes SMPOLY_COD value AF
This category includes SMPOLY_COD values G, S, and SG
|Coarse over Fine|
This category includes SMPOLY_COD value G/F, G/S/F, S/F, SG/F and SG/S/F
This category includes SMPOLY_COD value TS
This category includes SMPOLY_COD value F
|Fine over Coarse|
This category includes SMPOLY_COD values F/G, F/S and F/SG.
This category includes SMPOLY_COD values SM, SM/F, SM/S/F, SW, SW/F, SW/F/S, SW/S, SW/S/F, SW/S/SG, SW/SG and TA
This category includes SMPOLY_COD values G/S, G/SG, G/SG/S, S/F/SG, S/G, S/SG, SG/F/SG, SG/S and SG/S/SG
This category includes SMPOLY_COD value TT
This category includes SMPOLY_COD value T
This category includes SMPOLY_COD value W. Note, water is defined as streams, lakes, ponds, bays, and estuaries greater than 5 acres in size. Surficial Material water polygon features are outlined by Surficial Material line features with a SMARC_COD attribute value of 2 (for Hydrography Shoreline).
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: U.S. Geological Survey and 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: U.S. Geological Survey and State of Connecticut, Department of Environmental Protection)
Surficial Material polygon features describe 50 geologic textural units of unconsolidated materials (including water features) such as aluvium, fines, sand, gravel, and till. The information encoded about the geologic units includes the surficial material unit type and size. Use the SMPOLY_COD attribute as the key field to identify and differentiate surficial materials units. Refer to the SURFM_POLY attribute for a longer name for the geologic unit. Recommend labeling a map with the SMPOLY_COD attribute. For cartographic purposes, symbolize polygon features on a map using either the SMPOLY_COD or IMS_LEGEND attribute, depending on the desired level of detail. The Surfical Materials layer also describes 3 classes of polygon feature boundary types. Line feature attributes are primarily for cartographic purposes. For example, when symbolizing polygon features on different SMPOLY_COD attribute values, also uniquely symbolize line features on the SMARC_COD attribute to emphasize the various boundary types. When symbolizing polygon features on IMS_LEGEND attribute values, either uniquely symbolize line features on the SMARC_COD attribute to differentiate different boundary types or choose not display line features and simply outline all polygon features with the same line symbol.
Surficial Materials Map of Connecticut (Stone, J.R., Schafer, J.P., London, E.H. and Thompson, W.B., 1992, U.S. Geological Survey special map, 2 sheets, scale 1:125,000).
Mary DiGiacomo-Cohen (Long Island Sound Resource Center) for designing, compiling, digitizing, and editing the Surficial Materials data layer. The Long Island Sound Resource Center is a partnership between the State of Connecticut, Department of Environmental Protection and the University of Connecticut. Surficial materials digital data was produced by the State of 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 and Addiction Services. The U.S. Geological Survey in cooperation with the State of Connecticut, Department of Environmental Protection, Geological and Natural History Survey drafted the 1:24,000-scale compilation sheets used to publish the 1:125,000-scale Surficial Materials Map of Connecticut, Stone and others, 1992 and create the 1:24,000-scale digital data.
101 Pitkin Street
Connecticut Surficial Materials is 1:24,000-scale data suitable for geologic and environmental mapping and analysis purposes. Not intended for maps printed at map scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet.). Not intended for analysis with other digital data compiled at scales greater than or more detailed than 1:24,000 scale. Note, the Surficial Materials layer is complemented by the Quaternary Geology layer, which is based on the 1:24,000-scale compilation sheets for the 1:125,000-scale Quaternary Geologic Map of Connecticut and Long Island Sound Basin (U.S.G.S. Scientific Investigations Map 2784). The Quaternary Geologic Map of Connecticut and Long Island Sound Basin provides information on the distribution of depositional environments of glacial meltwater deposits.
Includes the 1:24,000-scale mylar overlay compilation sheets used to publish the Surficial Materials Map of Connecticut, Stone and others, 1992. Compilation sheets based on published and unpublished 1:24,000-scale surficial geolgic maps available to the compiler. Depending on the 7.5 minute quadrangle, data sources include Connecticut Geological and Natural History Survey Quadrangle Report (QR), U.S. Geological Survey Geologic Quadrangle Map (GQ), U.S. Geological Survey Miscellaneous Field Studies Map (MF), U.S. Geological Survey Miscellaneous Geologic Investication Map, U.S. Geological Survey Open-File Report, U.S. Geological Survey Open-File Map, University of Connecticut thesis, or unpublished data. For a complete list of data sources by 7.5 minute quadrangle, refer to Sheet 2 of the Surficial Materials Map of Connecticut, Stone and others, 1992. Topographic bases used in the original geologic compilation from USGS 1:24,000 scale revisions 1952-1970.
Surficial Materials is in ArcInfo Coverage format having both polygon and line features. The name of the ArcInfo Coverage is SURFMAT.
Includes all polygon features from Source 2 - Surficial Materials (ArcInfo Coverage format). Surficial_Materials_Poly.shp is in Shapefile format.
Surficial_Materials_Poly is in GeoDatabase Feature Class format.
Feature digitizing (digitizing tablet method) - Using ESRI ArcInfo software, features were digitized by registering each source Mylar 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 corners of the USGS 7.5 minute topographic quadrangle maps are used as registration points and are depicted on the source map. Each source map was registered to the digitizing tablet by digitizing (entering) the locations of four 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. RMS errors higher than 0.004 were not acceptable and required re-registering the source map by digitizing the tic locations again. Surficial material boundary lines (contacts) delineated on each source map were manually digitized according to the following spatial data accuracy standards: Standards for feature accuracy are: 90 percent of the digitized (linear) features are within .01 inch of their centerline on the original manuscript (source map); all digitize (linear) features are within .02 inch of their centerline on the original manuscript. Polygon features were created as a result of digitizing these (boundary) line features. The source maps are made from stable-base mylar. Selected waterbodies greater than 5 acres and related shoreline features were incorporated from existing digital hydrography data. Digital compilation utilized hydrography from 7.5 minute, 1:24,000-scale U.S. Geological Survey Digital Line Graph source material (1969-1984) with minor modification of geologic contacts to fit the revised hydrography where necessary. Hydrography selected from the USGS Digital Line Graph data (code numbers 050 0412,050 0421, and 050 0116) include streams, lakes, ponds, bays, estuaries, and seas with areas greater than 5 acres. In general, units shown on the 1:24,000-scale compilation sheets are typically those published on the 1:125,000-scale Surficial Materials Map of Connecticut. Additional map units may be present in the digital data that could not be readily shown on the published map at 1:125,000 scale or that represent more recent mapping, particularly along the coast. Some subsurface information as noted by stacked units may also be more detailed in the 1:24,000-scale digital data than that of the published 1:125,000-scale State Map. Attribution - Each polygon feature was manually assigned the corresponding SMPOLY_COD attribute, indicating the geologic unit type based on information the compilation sheets. Additionally, line features were manually attributed with SMARC_COD values to distinguish geologic contacts from shoreline and the state boundary. 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. Feature location and attribute accuracy was visually checked and inspected by symbolizing and labeling features according to attribute value on the computer screen and on hard copy paper maps, and comparing this information to the original source data. 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. Edgematching - Features along the boundaries of adjacent 7.5-minute quadrangle coverages were made to match (connect) to each other through a process of checkerboard style edgematching. Following a checkerboard pattern, line features were only adjusted on every other quadrangle. The edgmatching process resulted in defining the same point coordinate where line features from two adjacent quadrangles connect along quadrangle boundaries. Essentially, line end points were snapped to connect to line end points of the corresponding stationary linear features on adjacent quadrangles. Edge matching was successfully completed once it was possible to append all 7.5-minute quadrangle coverages and assemble a statewide coverage with polygons that closed without gaps (slivers) and overlaps. Appending - Subsequently, all 7.5-minute quadrangle coverages were appended to form a single, statewide Surficial Materials layer. Polygon features were merged across quadrangle boundaries. Linear features were unsplit (merged) to eliminate unnecessary pseudo nodes that connected similar line features (originally from different quadrangle coverages). Final polygon and line feature topology was established with ArcInfo Fuzzy and Dangle tolerances verified at 4 and 0 feet, respectively. Lookup tables were joined to the polygon and feature attribute to include additional attributes that decoded the SMPOLY_COD and SMARC_COD attributes such as SURFM_POLY, SURFM_ARC, DESCRIP, and IMS_LEGEND. 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. At this step in the process the Surficial Materials layer was fully attributed and ready for use. The name of the resulting data in ArcInfo Coverage format was SURFMAT.
Long Island Sound Resource Center
UConn Avery Point
1080 Shennecossett Rd
Export to Shapefile Format - Converted polygon feature data from ArcInfo Coverage named SURFMAT to a Shapefile named Surficial_Materials_Poly.shp. Excluded the AREA, PERIMETER, SURFMAT#, SURFMAT-ID attributes from the Shapefile because their values are only maintained by ArcInfo software with data that is in ArcInfo Coverage format.
79 Elm Street
Convert to GeoDatabase Feature Class format - Defined new Feature Class named Surficial_Materials_Poly; and imported the attribute definitions, loaded features and imported metadata from Surficial_Materials_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
79 Elm Street
The Surficial Materials layer retains the feature types and information identified on the 1:24,000-scale compilation sheets for the Surficial Materials Map of Connecticut, Stone and others, 1992. All attributes have valid values. Values are within defined domains. The accuracy test for the SMPOLY_COD attribute values was conducted by comparing the geologic map unit information presented on the source mylar overlays with 1:24,000-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 surficial material polygon features in different colors and line-fill patterns based on SMPOLY_COD attribute values for comparison with the original data source. SURFM_POLY and DESCRIP represent both brief and full text English language equivalents of (decodes) the SMPOLY_COD attribute, respectively. The AV_LEGEND and IMS_LEGEND polygon attributes are based on and key off the SMPOLY_COD attribute. These related attributes were populated by joining to lookup data tables using the SMPOLY_COD 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 SMPOLY_COD values. 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 SMARC_COD attribute that distinguishes contact boundaries from shoreline boundaries was manually entered for each feature. SURFM_ARC is the English language equivalent of (decodes) the SMARC_COD field values and was populated by joining a lookup table to the line features instead of manually attributing these values for each line feature.
The horizontal positional accuracy of this data complies with the United States National Map Accuracy Standards for 1:24,000 scale maps. According to this standard, not more than 10 percent of the locations tested are to be in error by more than 1/50 inch (40 feet) measured on the publication scale of a USGS 7.5 minute topographic quadrangle map. Feature locations were interpolated from the transporation features, surface water features, elevation contours, buildings, built-up areas, and other natural features and landforms depicted on USGS 7.5 minute topographic quadrangle maps.
The data reflects the content of the data source, which is a set of 1:24,000 scale mylar sheets used to compile and publish the Surficial Material Map of Connecticut, Stone and others, 1992 (U.S. Geological Survey in cooperation with the Connecticut Geological and Natural History Survey, DEP, 2 sheets, 1:125,000 publication scale). The Surficial Materials datalayer was digitized from these 1:24,000-scale mylar compilation sheets. 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. In general, there are no duplicate features, unresolved intersections, overshooting lines, open polygons, sliver polygons, or unlabeled (unattributed) polygons. 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 0 feet (dangle length).
No restrictions or legal prerequisites for using the data. The data is suitable for use at appropriate scale, and is not recommended for use with other data layers having source map scales greater than 1:24,000 (1 inch = 2000 feet) or printed on maps at scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet). The geologic contacts are considered accurate as mapped at 1:24,000 scale. While it may be desirable to represent the geology at a larger scale for site-specific applications, keep in mind that 1:24,000-scale accuracy may not be appropriate for such uses. 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 U.S. Geological Survey or 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 U.S. Geological Survey and 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: Surficial Materials - From the Surficial Materials layer, compiled and published by the USGS and CT DEP. Source map scale is 1:24,000.
79 Elm Street
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.
in format Shapefile, Feature Class, ArcInfo Coverage (version ArcGIS)
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.
Long Island Sound Resource Center, UConn Avery Point, 1080 Shennecossett Rd