| Postglacial deposits of the Pocasset-Provincetown-Cuttyhunk-Nantucket 24-quadrangle area of Cape Cod and Islands, southeast Massachusetts | |
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Data format: Shapefile File or table name: post_glacial Coordinate system: State Plane Coordinate System 1983 Theme keywords: surficial geology, stratified materials, stratified deposits, till, moraine, glacial deposits, beach, alluvium, swamp deposits, artificial fill, dune, cranberry bog |
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Abstract:
The postglacial 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 postglacial layer shows areas of swamp deposits, floodplain alluvium, cranberry bogs, and artificial fill for a twenty-four-quadrangle area in southeast Massachusetts. Swamp polygons may overlie alluvium polygons; artificial fill polygons may overlie areas of swamp or alluvium. This data layer should be used in conjunction with the underlying till and stratified_deposits data layers. |
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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 postglacial 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 postglacial layer shows areas of swamp deposits, floodplain alluvium, cranberry bogs, and artificial fill for a twenty-four-quadrangle area in southeast Massachusetts. Swamp polygons may overlie alluvium polygons; artificial fill polygons may overlie areas of swamp or alluvium. This data layer should be used in conjunction with the underlying till and stratified_deposits data layers.
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 postglacial 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 postglacial layer shows areas of swamp deposits, floodplain alluvium, cranberry bogs, and artificial fill deposits for a twenty-four-quadrangle area in southeast Massachusetts. This data layer should be used in conjunction with the underlying till and stratified_deposits data layers. 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 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 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.
1080 Shennecossett Rd.
Multiple agencies and individuals contributed to this data layer: MassGIS scanned and georeferenced paper copies of the published surficial geologic maps for fourteen 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 ten 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. Swamp deposits may overlap floodplain alluvium polygons. Artificial fill polygons may overlie swamp or alluvium polygons. 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
glacial deposits
glacial deposits
glacial deposits
glacial deposits
Paper copies of the published surficial geologic maps (10 quadrangles and Nantucket) 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, glacial stratified deposits, glacial till, and moraine deposits.
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).
1080 Shennecossett Rd.
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).
1080 Shennecossett Rd.
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 three final layers.
1080 Shennecossett Rd.
Metadata imported.
Internal feature number.
ESRI
Feature geometry
ESRI
map unit label
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floodplain alluvium
artificial fill
swamp and marsh deposits
salt-marsh deposits
beach and dune deposits
valley-floor fluvial deposits
cranberry bog
map unit
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Sand, gravel, silt, and some organic material, stratified and well sorted to poorly sorted, in narrow valleys of small modern streams. Most alluvial deposits in the Cape Cod region are not extensive enough to be shown on the map. The only mapped surface alluvial deposits are discontinuous deposits along Black, Paint Mill, Mill, and Roaring Brooks and the Tiasquam River, all on Martha's Vineyard, and near Cataumet, in the Pocasset quadrangle. Alluvium overlies thicker glacial moraine and stratified deposits, and thin alluvial deposits probably lie beneath salt-marsh deposits in coastal valley reaches that were flooded during the postglacial rise of sea level.
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Earth materials and manmade materials that have been artificially emplaced, primarily in highway and railroad embankments, and in dams; may also include landfills, urban development areas, and filled coastal wetlands
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Organic muck and peat that contain minor amounts of sand, silt, and clay, stratified and poorly sorted, in freshwater swamps and marshes, kettle depressions, or poorly drained areas. Swamp and marsh deposits are shown only where they are estimated to be at least 3 ft thick. Most swamp and marsh deposits are less than 10 ft thick. Swamp deposits overlie glacial meltwater deposits and postglacial pond deposits in kettle depressions. Unit includes salt-marsh deposits not differentiated on previously published quadrangle maps.
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Peat and organic muck interbedded with sand and silt, deposited in salt- or brackish-water environments of low wave energy along the coast and in river estuaries. Salt-marsh deposits are generally a few feet to 25 ft thick. In the major estuaries, these deposits locally overlie estuarine deposits (not mapped), which are sand and silt with minor organic material as much as 30 to 80 ft thick. The salt-marsh and estuarine deposits generally are underlain by adjacent glacial stratified deposits.
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Sand and fine 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. Sand beach deposits are composed of moderately sorted, very coarse to fine sand, commonly laminated. Coarser layers locally contain some fine gravel particles; finer layers contain some very fine sand and silt. Gravel beach deposits are composed of granule- to cobble-size clasts in moderately sorted thin beds; deposits contain minor amounts of sand within gravel beds, and thin beds of sand as alternating layers. Beach deposits are rarely more than a few feet thick. Dune deposits are composed of moderately to well sorted, fine to medium sand, variably massive, laminated, and crossbedded. Dune deposits are as much as 100 ft thick. Unit includes artificial sand deposits in locally replenished beaches.
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Sand, gravel, and minor silt, stratified and moderately to poorly sorted, beneath flat floors of valleys, called furrows (Mather and others, 1942) that are eroded into glacial outwash plains. The texture of the fluvial deposits commonly varies over short distances both laterally and vertically and generally is similar to the texture of adjacent glacial deposits. The fluvial deposits overlie thick glacial stratified deposits in the upper, dry reaches of the furrow valleys and probably are less than 20 ft thick. Swamp deposits and deformation of bedding related to melting of buried ice in kettles interrupt the fluvial deposits. The deposits probably extend beneath salt-marsh deposits in coastal valley reaches. The most extensive valley fluvial deposits are along Quaker Run and Coonamessett, Childs, and Quashnet Rivers on upper Cape Cod, and Quampachje Bottom on Martha's Vineyard.
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Mostly freshwater swamps or peat bogs overlain locally by artificially emplaced sand or other fill.
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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 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.
1080 Shennecossett Rd.