A characterization of the data, including its intended use and limitations.
Connecticut Quaternary Geology Long Island Submerged Marine Lake Deposits identifies lake-bottom and deltaic deposits of Glacial Lake Connecticut submerged in Long Island Sound and Fishers Island Sound. This information appears on Sheet 1 of the The Quaternary Geologic Map of Connecticut and Long Island Sound Basin (Stone and others, 2005).
The Connecticut Quaternary Geology digital spatial data combines the information portrayed on the on-land portion of the Quaternary Geologic Map of Connecticut and Long Island Sound Basin (Stone and others 2005) with the information portrayed on its sister map, the Surficial Materials Map of Connecticut (Stone and others, 1992). When used together, these maps provide a three dimensional context for understanding and predicting the internal composition, resource potential and hydrologic character of Connecticut's glacial and postglacial deposits. Both were compiled at 1:24,000 scale, and published at 1:125,000 scale.
The Quaternary Geologic Map of Connecticut and Long Island Sound Basin (Stone and others, 2005) portrays the glacial and postglacial deposits of Connecticut (including Long Island Sound) with an emphasis on where and how they were emplaced. Glacial Ice-Laid Deposits (thin till, thick till, and deposits of individual end moraines), Early Postglacial Deposits (Late Wisconsinan to Early Holocene stream terrace and inland dune deposits) and Holocene Postglacial Deposits (alluvium, swamp deposits, marsh deposits, beach and dune deposits, talus, and artificial fill) are differentiated from Glacial Meltwater Deposits. This mapping is based on the concept of systematic northward retreat of the Late Wisconsinan glacier. Meltwater deposits are divided into six depositional system categories (Deposits of Major Ice-Dammed Lakes, Deposits of Major Sediment-Dammed Lakes, Deposits of Related Series of Ice-Dammed Ponds, Deposits of Related Series of Sediment-Dammed Ponds, Deposits of Proximal Meltwater Streams, and Deposits of Distal Meltwater Streams) based on the arrangement and character of the groupings of sedimentary facies (morphosequences).
The Surficial Materials Map of Connecticut (Stone and others, 1992) 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.
The geologic contacts between till and meltwater deposits coincide on both the Quaternary and Surficial Materials maps, as do the boundaries of polygons that define areas of thick till, alluvium, swamp deposits, marsh deposits, beach and dune deposits, talus, and artificial fill. Within the meltwater deposits, a Quaternary map unit (deposit) may contain several Surficial Materials textural units (akin to facies within a delta, for example). Combining the textural and vertical stacking information from the Surficial Materials map with the orderly portrayal of morphosequence relationships, up and down valley, that can be gleaned from the Quaternary map provides a three dimensional predictive context for relating the geologic setting of Connecticut's glacial meltwater deposits to their behavior as aquifers and/or transmitters of contaminants.
Since this data layer is a polygon and line feature representation of the two maps combined, each map unit's depiction and description could provide information as to its aerial extent, subsurface textural characteristics, depositional and paleogeographic settings, and facies composition in a morphosequence context. Therefore, a typical meltwater polygon would have a combination of Quaternary (e.g. Deposit of Major Sediment-Dammed Lake; Glacial Lake Middletown Cromwell Deltaic Deposit) and Surficial Materials (e.g. sand and gravel overlying sand overlying fine) map attributes. 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 geologic or textural units such as a geologic contact line between two different geologic units or a linear shoreline feature between a textural unit and an adjacent waterbody.
The data have been updated to reflect minor changes in map unit name (QUPOLY_COD) for consistency with the 2005 publication of the Quaternary Geologic Map of Connecticut and Long Island Sound Basin. Previously distributed versions of CTQSGEOM were consistent with the 1998 Open-file Report for the same map.
It is important to note that this data layer represents only the on-land portion of the Quaternary Geologic Map of Connecticut and Long Island Sound Basin (Stone and others, 2005). The off-shore geologic units are organized in separate data layers (LISQMOR, LISQFAN, LISQLAKE, LISQCHAN, LISQMARD) which can be used in conjunction with this data layer. These Long Island Sound layers have been mapped at 1:80,000 scale using seismic reflection data.
The CTQSGEOM data layer should be used as the geologic base for Connecticut Quaternary Geology / Surficial Materials Features (CTQSFEAT) data layer which represents features such as eskers, meltwater channels, spillways, and locations of radio-carbon dated samples.
Connecticut Quaternary Geology and 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. This data layer should be used as the geologic base for Connecticut Quaternary Geology / Surficial Materials Features (CTQSFEAT). The data layer can be used in conjunction with data layers representing related geologic features in the Long Island Sound Basin (LISQMOR, LISQFAN, LISQLAKE, LISQCHAN, LISQMARD).
Data manually digitized from 1:24,000-scale mylar quadrangle compilation sheets prepared for the Surficial Materials Map of Connecticut, 1:125,000 scale (Stone and others, 1992) and the Quaternary Geologic Map Of Connecticut and Long Island Sound Basin, 1:125,000 scale (Stone and others,2005). For a more complete understanding of the geologic principles behind the data it is advisable to consult these source maps which contain cross sections, diagrams and text not available in digital form. Digital files which should be used with this data set include: SIM-2784.pdf (pamphet from the Quaternary Geologic Map Of Connecticut and Long Island Sound Basin), Surficial Materials data layer, and the companion data sets: Connecticut Quaternary Geology / Surficial Materials Features (CTQSFEAT), and Long Island Sound moraines (LISQMOR), lacustrine fans (LISQFAN), lake-bottom and deltaic deposits (LISQLAKE), channel-fill deposits (LISQCHAN), and marine deltaic deposits (LISQMARD); all available for download at http://www.dep.state.ct.us/gis.
Kristi LeDuc, Margaret Thomas, and Mary DiGiacomo-Cohen for designing, compiling, digitizing, and editing the Quaternary Geology and Surficial Materials data layer. Much of the production effort was undertaken by the Long Island Sound Resource Center: a partnership between the State of Connecticut, Department of Environmental Protection and the University of Connecticut Marine Sciences and Technology Center. This 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.