Back to Swath Mapping of the New Jersey and Northern
California Margins
Back to STRATAFORM home page
Principle Investigators:
Larry Mayer (lmayer@jupiter.sun.csd.unb.ca):
University of New Brunswick, Fredrickton Ocean Mapping Group
John Goff (goff@utig.ig.utexas.edu): University of
Texas Institute for Geophysics, Austin, TX
Funded by: Office of Naval
Research
Accurate, high resolution images of the continental shelf seafloor are an essential starting point for quantitative, rigorous investigation of modern seafloor geomorphology and sedimentology. Furthermore, meter-scale investigation of the sedimentary structure and sedimentology of the modern seafloor give us the information we need to link modern seafloor features with sedimentary structure, and process, in the stratigraphic record. Our newest data from the New Jersey continental shelf help us meet these STRATAFORM objectives.
Figure 1: Study area location with regional bathymetry in meters (generated from CD-ROM compilation of hydrographic data by the National Oceanic Services). Swath survey area in yellow
From April 30 to May 23, 1996 we collected ~2000 km2 of high resolution bathymetry and acoustic backscatter data on the continental shelf off Atlantic City, NJ (see our cruise reports). Principle Investigators Larry Mayer and John Goff conducted eight two-day cruise legs aboard the Canadian Hydrographic Survey ship Frederick G. Creed. James Austin and Laurie Schuur from UTIG, John Hughes Clark from UNB, Bill Ryan, Micheal Steckler and Dale Chayes from LDEO, and Peter Rona and Waldo Wakefield from Rutgers University also participated in the cruise. Navigation (differential GPS), ship maintainance and sound velocity profiling were the responsibilty of the Canadian Hydrographic Survey crew.
Figure 2: The Fredrick J. Creed at the U.S. Coast Guard Station
in Atlantic City (Bally's casino for scale)
The sonar system, Simrad EM-1000, is a 150 degree semicircular 95 kHz multibeam transducer that collects both amplitude and phase-angle information for each of 60, 2.5 degree beams. The Simrad transducer is mounted on the Creed's starboard pontoon. Thanks to software created by John Hughes Clarke and Larry Mayer, we collected, processed and displayed the data during the cruise. Using a graphic interface; we checked for navigation errors, edited artifacts (e.g. a multiple off the port pontoon, scattering of the farthest beams), made a refraction correction to account for water column thermal structure, created a bathymetry grid and a sidescan mosaic of each survey line while collected data for the next line. Now, back at Texas and in New Brunswick, we have completed a preliminary set of bathymetry and sidescan maps and have begun interpretation of the acoustic features we see on the seafloor. The pixel resolution in this first set of images is 25mX29m and we can resolve vertical structures <1m in height.
(Click image for a larger version)
Figure 3: Illuminated bathymetry (illumination angle 0 degrees) of the NJ Continental shelf. Numbers indicate the following areas of interest: 1. The relict Franklin shore, 2. The Hudson apron and glacial morphology, 3. The continental shelf edge and the heads of 9 submarine canyons from Tom's Canyon to Lindenkohl Canyon 4. Relict and modern sand ridges, ripples, relict bedforms, and sedimentary fabrics created in shore and shelf depositional systems.
(Click image for a larger version)
Figure 4: Color sidescan sonar image (yellow represents high backscatter and microscale roughness) with illuminated bathymetry. Note the following features: 1. The area of high backscatter on the Franklin shore east of Tom's Canyon, 2. Fairly low microscale roughness the area of extensive glacial morphology, 3. a low backscatter valley between sand ridges 4. A very high backscatter scarp oriented obliquely to other local features.
Abstract for submitted paper:
High resolution swath sonar
investigation of sand ridge and sand ribbon morphology in the offshore environment of the
New Jersey margin
Correspondence to Larry Mayer (lmayer@jupiter.sun.csd.unb.ca) in New Brunswick or John Goff (goff@utig.ig.utexas.edu) at Texas. Questions about NJ swath mapping and this page to Laurie Schuur (laurie@utig.ig.utexas.edu)