| Till and bedrock of the Heath-Northfield-Southwick-Hampden 24-quadrangle area in the Connecticut Valley region, west-central Massachusetts - till_bedrock | |
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Data format: Shapefile File or table name: till_bedrock Coordinate system: State Plane Coordinate System 1983 Theme keywords: surficial geology, stratified materials, stratified deposits, till, glacial deposits, stream terrace, alluvium, swamp deposits, artificial fill, dune, talus |
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Abstract:
The till_bedrock data layer is part of a comprehensive study to produce a statewide digital map of the surficial geology at 1:24,000 scale. This compilation of surficial geologic materials defines the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits. The till_bedrock layer shows areas of thin till, thick till, bedrock outcrops, and areas of abundant outcrop and shallow bedrock for a twenty-four-quadrangle area in west-central Massachusetts.Thin till and bedrock outcrops polygons are mutually exclusive; thick till polygons overlie areas of thin till, and abundant outcrop/shallow bedrock polygons overlie areas of thin till and bedrock outcrops. This data layer should be used in conjunction with the overlying stratified_deposits data layer, early_postglacial data layer, and the postglacial data layer. |
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Metadata elements shown with blue text are defined in the Federal Geographic Data Committee's (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM). Elements shown with green text are defined in the ESRI Profile of the CSDGM. Elements shown with a green asterisk (*) will be automatically updated by ArcCatalog. ArcCatalog adds hints indicating which FGDC elements are mandatory; these are shown with gray text.
The till_bedrock data layer is part of a comprehensive study to produce a statewide digital map of the surficial geology at 1:24,000 scale. This compilation of surficial geologic materials defines the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits. The till_bedrock layer shows areas of thin till, thick till, bedrock outcrops, and areas of abundant outcrop and shallow bedrock for a twenty-four-quadrangle area in west-central Massachusetts.Thin till and bedrock outcrops polygons are mutually exclusive; thick till polygons overlie areas of thin till, and abundant outcrop/shallow bedrock polygons overlie areas of thin till and bedrock outcrops. This data layer should be used in conjunction with the overlying stratified_deposits data layer, early_postglacial data layer, and the postglacial data layer.
The purpose of this study is to provide fundamental geologic data for the evaluation of natural resources, hazards, and land information within the Commonwealth of Massachusetts. The till_bedrock deposits data layer is part of a comprehensive effort to produce a statewide digital map of the surficial geology at 1:24,000 scale. This compilation of surficial geologic materials defines the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits. The till_bedrock layer shows areas of thin till, thick till, bedrock outcrops, and areas of abundant outcrop and shallow bedrock for a twenty-four-quadrangle area in west-central Massachusetts. This data layer should be used in conjunction with the overlying stratified_deposits data layer, early_postglacial data layer, and the postglacial data layer. This map of twenty-four quadrangles revises previous digital surficial geologic maps (Stone and others, 1993; MassGIS, 1999) that were compiled on base maps at regional scales of 1:250,000.
publication date
No restrictions or legal prerequisites for using the data. The data are suitable for use at appropriate scale, and are not intended for maps printed at scales with higher resolution than 1:24,000 scale (1 inch = 2,000 feet). Although this data set has been used by the U.S. Geological Survey and the Commonwealth of Massachusetts, neither the U.S. Geological Survey nor the United States Government nor the Commonwealth of Massachusetts makes any warranty, expressed or implied, nor assumes any legal liability or responsibility for the accuracy of these data 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 United States Government, or the Commonwealth of Massachusetts 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 are distributed to the user, modifications made to the data by the user should be noted in the metadata. When printing these data on a map or using them in a software application, analysis, or report, please acknowledge the U.S. Geological Survey as the source for this information.
101 Pitkin St.
Multiple agencies and individuals contributed to this data layer: MassGIS scanned and georeferenced paper copies of the published surficial geologic maps for fifteen quadrangles; the Office of the Massachusetts State Geologist vectorized the georeferenced images and compiled geologic units in order to digitally retain the original information on the published maps (Mabee and others, 2004); U.S. Geological Survey personnel compiled and digitized the basic units for nine unpublished quadrangles from scanned field maps, and then joined and edge-matched the twenty four quadrangles in order to form a seamless geologic map.
Attributes have been visually checked by the compilers.
Polygon features conform to the following topological rules. There are no duplicate polygons. Polygons do not self overlap. Thin till and bedrock polygons are exclusive and do not overlap other each other. Thick till polygons overlie thin till polygons. Abundant outcrop/shallow bedrock polygons overlie thin till polygons and may overlie individual bedrock outcrops. No automated procedures or tests were performed to guarantee desired topology other than visual inspection.
The completeness of the data reflects the feature content of the basic units chosen for this interim product for all data sources. Additional information can be found on the data sources, which may be utilized in future compilations. The layer is complete in the sense that it accurately reflects the postglacial units for this twenty-four-quadrangle area, noting that edits (including additional units) may occur to this data set when it is edge-matched to surrounding quadrangles during future compilations.
The horizontal positional accuracy of these 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.
Glacial deposits - some stratified deposits have been modified (including, but not limited to, extention beneath water bodies and postglacial deposits).
Glacial deposits - some stratified deposits have been modified (including, but not limited to, extention beneath water bodies and postglacial deposits).
glacial deposits
glacial deposits
glacial deposits
glacial deposits
glacial deposits
glacial deposits
glacial deposits
glacial deposits
glacial deposits
Paper copies of the published surficial geologic maps (15 quadrangles) were scanned at 500 dpi and georeferenced using lat/long coordinates (2nd-order polynomial transformation). Images were projected to UTM, zone 19, NAD27.
MassGIS
Executive Office of Environmental Affairs
251 Causeway St., Suite 500
The Office of the Massachusetts State Geologist vectorized the georeferenced images in order to digitally retain the original line work of the published maps (Mabee and others, 2004). Digital geologic map units were compiled and grouped into basic units and attributed: artificial fill, swamp deposits, floodplain alluvial deposits, stream terrace deposits, glacial stratified deposits, glacial till, and bedrock areas (outcrops and areas of shallow bedrock).
Department of Geosciences
University of Massachusetts
611 North Pleasant St.
Basic unit coverages for each layer in each quadrangle were projected to Massachusetts state plane NAD83, then edited, edge-matched, and appended into a single layer for each geologic unit (covering all published quadrangles).
101 Pitkin St.
Unpublished field sheets were scanned and georeferenced. Published map were consulted and geologic units were vectorized or created (on screen digiziting). Basic unit coverages for each layer in each quad were edited, edge-matched, and appended into a single layer for each geologic unit (covering all unpublished quadrangles).
101 Pitkin St.
Basic unit coverages for unpublished and published areas were edge-matched, edited as needed, and appended into coverages for the twenty four quadrangle area. Coverages were converted to shapefile format and combined into the four final layers.
101 Pitkin St.
Metadata imported.
Internal feature number.
ESRI
Feature geometry
ESRI
map unit label
compiler
thin till
thick till
bedrock outcrops
areas of abundant outcrop and shallow bedrock
map unit
compiler
Nonsorted, nonstratified matrix of sand, some silt, and little clay containing scattered pebble, cobble, and boulder clasts; large surface boulders are common; mapped where till is generally less than 10 to 15 ft thick including areas of shallow bedrock. Predominantly consists of upper till of the last glaciation; 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 an underlying more compact, finer grained lodgement facies deposited subglacially. In general, both ablation and lodgement facies of upper till derived from fine-grained bedrock are finer grained, more compact, less stony and have fewer surface boulders than upper till derived from coarse-grained crystalline rocks. Fine-grained bedrock sources include the red Mesozoic sedimentary rocks of the Connecticut River lowland, marble in the western river valleys, and fine-grained schists in upland areas
compiler
Nonsorted, nonstratified matrix of sand, some silt, and little clay containing scattered pebble, cobble, and boulders in the shallow subsurface; at greater depths consists of compact, nonsorted matrix of silt, very fine sand, and some clay containing scattered small gravel clasts. Mapped in areas where till is greater than 10 to15 ft thick, chiefly in drumlin landforms in which till thickness commonly exceeds 100 ft (maximum recorded thickness is 230 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
compiler
extent of individual bedrock outcrops
compiler
areas of shallow bedrock or areas where small outcrops are too numerous to map individually; in areas of shallow bedrock, surficial materials are less than 5 to 10 ft thick. These units are not mapped consistently among all quadrangles; see Appendix for level of bedrock outcrop mapping in each quadrangle.
compiler
Although this data set has been used by the U.S. Geological Survey and the Commonwealth of Massachusetts, neither the U.S. Geological Survey nor the United States Government nor the Commonwealth of Massachusetts makes any warranty, expressed or implied, nor assumes any legal liability or responsibility for the accuracy of these data or related materials.
101 Pitkin St.