Sedimentary Environment Map of Long Island Sound in ArcView Shapefile Format, USGS OFR 00-304

This GIS layer represents the researcher's interpretation of the
regional distribution of sea-floor sedimentary environments in Long
Island Sound.

Long Island Sound is one of the largest estuaries along the Atlantic
coast of the United States. It is a glacially produced, semi-enclosed,
northeast-southwest-trending embayment, which is 150 km long and 30 km
across at its widest point. Its mean water depth is approximately 24
m. The eastern end of the Sound opens to the Atlantic Ocean through
several large passages between islands, whereas the western end is
connected to New York Harbor through a narrow tidal strait. Long
Island Sound abuts the New York-Connecticut metropolitan area and
contains more than 8 million people within its watershed. A study of
the modern sedimentary environments on the sea floor within the Long
Island Sound estuarine system was undertaken as part of a larger
research program by the U.S. Geological Survey (Coastal and Marine
Geology Program) conducted in cooperation with the State of
Connecticut Department of Environmental Protection and the
U.S. Environmental Protection Agency. Knowledge of the bottom
sedimentary environments was needed to discern the long-term fate of
wastes and contaminants that have been, or potentially will be,
introduced into the system and to help understand the distribution of
benthic biologic habitats.

The original interpretation was hand-drawn on mylar based on
sidescan-sonar data, seismic-reflection profiles, and sediment sample
data collected in the study area. The extent of this orginal work only
extended shoreward to the 10m contour interval. This interpretation
was then digitized on a digitizing table. This line information was
then transferred to Arc/Info where significant cleaning of the data
was done. These arcs were then converted to polygons and the attribute
information attached. Subsequently, data from the 10 m contour
shoreward was incorporated into the original mylar interpretive
map. These changes were then digitized and incorporated into the
existing Arc/Info coverage. Again, significant cleaning of the arcs as
well as assigning the attribute information was done in Arc/Info. The
original projection of this work was UTM zone 18, NAD27. For this
publication, these data were reprojected into UTM zone 18 NAD 83. This
Arc coverage was exported in the e00 format and imported into
ArcView. The new theme was then saved in the shapefile format.