U.S. DEPARTMENT OF THE INTERIOR Prepared in cooperation with the GEOLOGIC INVESTIGATIONS SERIES U.S. GEOLOGICAL SURVEY NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION MAP I- 2698- A

69o 03' W 69o 02' W 69o 01' W 69o 00' W 68o 59' W 68o 58' W 68o 57' W 68o 56' W 68o 55' W 68o 54' W 68o 53' W 68o 52' W 68o 51' W 68o 50' W 68o 49' W 68o 48' W o 80 55 o 41 01' N 8 70 5 41 01' N 80 7 65 65 5 0 7 70 80 80 8 5 5 60 55 85 7 70 60 5 65 7 8 5 70 5 5 75 7 75 65 80 7 70 60 0 60 80 8 65 60 80 80 60 85 70 70 90 7 75 80 65 5 60 60 60 80 80 70 80 85 70 85 85 70 5 65 80 80 7 65 70 60 0 0 8 8 65 8 0 75 60 75 75 75 70 70 75 65 70 60 65 65 75 70 80 85 75 70 85 85 80 0 8 75 60 65 8 0 70 80 5 70 60 85 7 60 75 65 65 0 65 80 8 75 0 0 75 65 80 8 8 60 70 70 65 85 80 80 70

70 70 65 75 70 75 75 0 80 8 70 70 41o 00' N 80 75 70 41o 00' N 70 75 60 80 8 5 60 0 7 65 70 80 75 8 0 65 75 65 70 70 65 65 60 65 60 70 65 85 0 75 8 85 65 65 0 70 8 80 70 75 0 8 0 60 75 80 80 8 5 7 70 65 80 75 70 65 65 80 80 70 70 65 80 70 70 70 80 80 65 85

5 70 8 7 70 70 65 0 70 75 70 70 65 80 75 0 70 65 75 8 70 65 65 75 85 80 65 70 75 65 80 70 65 75 80 75 70 75 70 80 80 5 75 70 80 75 7 7 70 5 65 75 75 80 5 0 70 7 o 40o 59' N 70 8 70 40 59' N 80 75 65 5 7 70 70 65 80 70 85 5 75 75 7 70 80 85 70 80 0 70 60 70 0 8 8 75 65 70 75 70 70 75 7 80 0 75 5 70 8 60 80 80 70 65 75 7 75 80 75 5 65 75 75 65 80 5 7 70 70 65 75 80 85 75 70

8 75 70 75 0 70 60 80 0 80 80 8 70 80 0 8 85 70 0 0 70 75 8 7 70 65 70 70 65 7 80 5 75 5 7 70 70 70 65 75 80 65 65 70 55 80 80 8 75 70 0 75 5 75 70 7 75 70 80 8 70 70 0 8 85 80 0 75 75 5 65 8 65 7 0 70 0 70 8 8 75 70 0 70 80 80 70 o 75 75 70 o 40 58' N 70 40 58' N 85 70 75 80 75 75 70 70 0 75 75 8 80 80 75 75 70 80 65 65 60 75 85 80 70 70 70 65 7 80 5 75 65 70 5 80 75 80 7 75 70 85 85 75 70 75 75 70 5 70 5

7 80 75 80 80 7 65 70 75 80 90 80 5 70 7 85 65 70 70 75 70 70 75 80 70 65 65 85 65 85 75 5 80 75 7 80 80 5 5 65 7 75 7 0 8 70 70 70 60 75 80 70 7 75 5 70 0 5 70 65 0 8 7 70 65 70 8 70 75 70 75 75 70 75 75 65 65 70 85 75 80 0 75 8 70

75 65 80 70 o 75 55 70 o 40 57' N 65 85 80 65 40 57' N 70 70 70 5 70 75 65 7 65 75 80 80 80 75 70 85 70 70 80 80 75 70 7 80 5 75 0 65 8 65 75 7 65 5 70 70 80 85 70 6 0 65 0 70 85 80 8 70 60 75 85 80 80 75 70 70 8 70 70 75 0 70 70 8 70 0 70

75 0 65 6 80 70 70 70 80 5 75 80 7 80 85 70 8 8 70 0 0 0 75 65 6 65 7 70 75 80 85 70 5 65 70 0 5 8 80 7 75 75 75 75 80 65 75 70 70 70 8 85 85 70 65 75 0 5 8 70 75 85 70 85 70 5 0 7 80 8 70 70 65 70 75 75 65 65 0 70 7 70 8 5 5 5 70 5 70 70 7 o 7 80 7 70 40o 56' N 40 56' N 80 75 70 65 7 5 7 0 5 8 80 75 70 8 70 5 7 80 5 70 65 7 80 5 7 5 70 75 5 80 7 7 75 5 75 75 75 85 80 75 65 80 75 80 75 70 80 65 5 70 7 80 70 65 5 75 75 60 7 75 75 7 80 75 5 75 70 0 85 0 85 8 80 8 0 70 70 75 8 75 75 75 70 80 75 5 7 75 80 0 0 80 8 70 8 70 75 70 75 70 75 5 75 80 75 7 70 7 70 70 70 5 75 8 5 80 70 7 0 75 5 8 5 7 70 0 5 0 7 70 8 90 8 75 7 80 0 5 70 75 7 75 85 5 70 7 85 7 5 80 80 0 80 8 75 8 0 70 0 5 5 8 75 0 5 70 7 65 7 80 8 7 7 7 70 5 5 5 75 85 80 70 7 70 65 70 75 80 65 75 70 75 80 75 8 7 75 0 65 80 5 75 65 80 65 75 8 0 85 85 7 5 75 70 o 5 7 70 65 6 70 o 40 55' N 70 0 40 55' N 7 80 5 80 80 70 7 60 7 5 70 65 70 0 65 5 70 8 7 8 70 0 5 70 65 70 75 5 65 75 7 70 60 70 70 65 80 80 80 70 75 70 0 65 70 65 0 8 5 70 8 7 75 65 70 75 70 70 65 70 75 75 85 65 80 70 70 6 70 80 70 80 65 0 65 80 75 75 80 75 60 80 70 0 70 70 65 80 8 70 75 75 70 70 80 70 8 5 80 60 75 70 0 75 7 70 0 75 70 5 70 8 8 7 0 7 75 70 5 75 80 70 70 70 85 65 75 70 75 0 0 65 5 8 8 5 5 70 8 7 8 65 75 0 7 70 70 70 75 0 70 5 80 8 65 85 8 80 65 0 70 8 80 70 70 0 8 8 7 0 5 70 75 70 70 70 75 75 5 85 70 75 75 70 70 65 8 80 0 5 70 0 8 7 75 9 70 75 8 9 5 70 0 0 7 70 0 7 8 70 70 5 80 70 70 75 65 70 60 70 40o 54' N 85 80 85 70 40o 54' N 69o 03' W 69o 02' W 69o 01' W 69o 00' W 68o 59' W 68o 58' W 68o 57' W 68o 56' W 68o 55' W 68o 54' W 68o 53' W 68o 52' W 68o 51' W 68o 50' W 68o 49' W 68o 48' W

Mercator projection SCALE 1:25 000

Geodetic Reference System 1980; 1983 ONE CENTIMETER REPRESENTS 250 METERS ON THE SEA FLOOR o o of central meridian 68 55' W.; latitude of true scale 40 50' N. 1 .5 0 1234 KILOMETERS False easting 0 m; false northing 0 m

This map is not intended for navigational purposes 1 .5 0 1 2 NAUTICAL MILES 70º 69º CONTOUR INTERVAL 5 METERS 40 DATUM MEAN LOWER LOW WATER

42º

4 0

CAPE COD BAY 200 DISCUSSION Topographic contour mapping 42º Bathymetric data were contoured using the Arc/Info geographic information system E AIN Introduction software (Environmental Systems Research Institute, Inc., version 7.0.3). Processed data CAPE COD M F were formatted into a point file using the Arc/Info "point generate" routine. The point file O The Georges Bank Mapping Project is a cooperative effort of the U.S. Geological Survey o F was transformed to a Mercator projection, with the longitude of the central meridian at 68 100 L 80 U and the National Oceanic and Atmospheric Administration (NOAA), with support from the 60 o 4 G 55' W. and the latitude of true scale at 40 50' N. The "point grid" routine was used to 0 University of New Brunswick and the Canadian Hydrographic Service. A multibeam echo NANTU create a grid from the point file and to assign depth values to individual grid cells. The cell CKET SOUND sounder survey of the Great South Channel region was conducted in November 1998. This size of the output grid was 9 m. Topographic contours at 5-meter intervals were generated map, one in a series of two mapped quadrangles (see location map), presents the results of using the "lattice contour" routine. Most of the contour lines are shown here unedited. C 100 this survey, in which sea floor topography is depicted at a scale of 1:25,000. For a map LOSED However, in areas of very smooth sea floor, some contours displayed distortions caused by AREA I showing sun-illuminated sea floor topographic imagery, see the companion map by problems encountered during data acquisition at nadir (directly below the vessel's keel) and NANTUC

Valentine and others (2002) on this CD-ROM. 0 by refraction effects at the outermost edge of the swath. These distortions were smoothed ISLAN 8 NAN by employing a user-defined low-frequency "focal median" filter routine on the grid created KET D TUC Survey methods by "point grid". A square focal median filter using a 3-cell by 3-cell size was used. The 60 K resulting contours were compared with features displayed in shaded-relief seabed imagery of ET S The survey was conducted using a multibeam echo sounder installed aboard the Canadian H the same data, and were edited manually with Arc/Edit to remove small artifacts that 41º OALS Hydrographic Service vessel Frederick G. Creed, a SWATH (Small Waterplane Area Twin BANK remained after filtering. Large east-west-trending bedforms (typically 5 to 10 m high, but Hull) ship that surveys at speeds up to 15 knots. During the survey, the ship's position was ES ranging up to 20 m) characterize parts of the sea floor in this region. The multibeam echo 2 G determined with an accuracy of 10 m or better using a global positioning system (GPS) EOR sounder had difficulty imaging these features because they are oriented at right angles to the G receiver in conjunction with differential GPS corrections transmitted by U.S. Coast Guard ship's tracks and display steep sides and narrow crests. As a result, some of these bedforms radio beacons. The multibeam echo sounder data were collected by means of a Simrad 1 are depicted by slightly irregular contours. Each of the quadrangles was contoured 41º Subsea EM 1000 Multibeam Echo Sounder (95 kHz) that is permanently installed in the hull independently, and contours that extend into Quadrangle 2 were edited manually to match 40 of the Creed. In water depths between 5 and 200 m, the EM 1000 generates 60 aimed at the boundary. beams, spaced at intervals of 2.5 degrees, that insonify a swath of sea floor measuring in REFERENCE CITED width approximately 7.5 times the water depth. Horizontal spatial resolution is on the order Valentine, P.C., Middleton, T.J., and Malczyk, J.T., 2002, Sun-illuminated sea floor 60 of 10 percent of the water depth at 15 knots; vertical resolution is approximately 1 percent topography of Quadrangle 1, map B of Valentine, P.C., ed., Maps showing sea floor of the water depth or better. Software developed by the Ocean Mapping Group, University ANNEL topography, sun-illuminated sea floor topography, and backscatter intensity of H of New Brunswick, was used to process and edit the echo sounder bathymetric and Quadrangles 1 and 2 in the Great South Channel region, western Georges Bank: U.S. C H differential GPS navigation data; tidal corrections based on NOAA's Nantucket tide gauge Geological Survey Geologic Investigations Series Map I–2698, scale 1:25,000, on a N ANTUCKE were used to reference depth data to mean lower low water. CD-ROM. T LIG HTSHIP CLOSE D AREA 80 (part)

REAT SOUT

G

100

70º 69º Location map outlining the two quadrangles in this series. Quadrangle 1 shown in blue. Closed Area I and Nantucket Lightship Closed Area were established in December SEA FLOOR TOPOGRAPHY OF QUADRANGLE 1 1994 by the New England Fishery Management Council. Bathymetric contours are in meters. By Page C. Valentine, Tammie J. Middleton, and Jeremy T. Malczyk

Map A of Maps Showing Sea Floor Topography, Sun-Illuminated Sea Floor Topography, and Backscatter Intensity of

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Quadrangles 1 and 2 in the Great South Channel Region, Western Georges Bank

CD-ROM of I- 2698 is for sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225; telephone: 1-888-ASK-USGS Page C. Valentine, editor For more information contact: Page Valentine, U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, MA 02543 2002