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Backscatter Intensity and Sun-Illuminated Sea Floor Topography of Quadrangles 1 and 2

IMAP 2698-E

Prepared in cooperation with the U.S. National Oceanic and Atmospheric Administration
By:
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Abstract

The Great South Channel separates the western part of Georges Bank from Nantucket Shoals and is a major conduit for the exchange of water between the Gulf of Maine to the north and the Atlantic Ocean to the south. Water depths range mostly between 65 and 80 m in the region. A minimum depth of 45 m occurs in the east-central part of the mapped area, and a maximum depth of 100 m occurs in the northwest corner. The channel region is characterized by strong tidal and storm currents that flow dominantly north and south. Major topographic features of the seabed were formed by glacial and postglacial processes. Ice containing rock debris moved from north to south, sculpting the region into a broad shallow depression and depositing sediment to form the irregular depressions and low gravelly mounds and ridges that are visible in parts of the mapped area. Many other smaller glacial featuresprobably have been eroded by waves and currents at worksince the time when the region, formerly exposed bylowered sea level or occupied by ice, was invaded by the sea. The low, irregular and somewhat lumpy fabric formed by the glacial deposits is obscured in places by drifting sand and by the linear, sharp fabric formed by modern sand features. Today, sand transported by the strong north-south-flowing tidal and storm currents has formed large, east-west-trending dunes. These bedforms (ranging between 5 and 20 m in height) contrast strongly with, and partly mask, the subdued topography of the older glacial features.

Geospatial Extents

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Backscatter Intensity and Sun-Illuminated Sea Floor Topography of Quadrangles 1 and 2
Series title:
IMAP
Series number:
2698
Subseries
GIS
Chapter:
E
Edition:
Version 1.0
Year Published:
2002
Language:
ENGLISH
Publisher:
Geological Survey (U.S.)
Contributing office(s):
U.S. Geological Survey
Description:
1 Sheet: 40 x 57 inches; Also available on CD-ROM
Larger Work Type:
Report
Larger Work Subtype:
USGS Numbered Series
Larger Work Title:
Maps Showing Sea Floor Topography, Sun-Illuminated Sea Floor Topography, and Backscatter Intensity of Quadrangles 1 and 2 in the Great South Channel Region, Western Georges Bank
Projection:
Universal Transverse Mercator
Scale:
25000