Geologic Features of the Sea Bottom Around a Municipal Sludge Dumpsite near 39øN, 73øW, Offshore New Jersey and New York: U.S. Geological Survey Open-file Report 94-152

ILLUSTRATION AND CAPTIONS SUMMARY

An Index Map showing the continental margin off the mid-Atlantic Coast of the U.S. Areas of the following GLORIA mosaic illustration and the site-mapping studies are outlined as rectangles; an area mapped using Sea Beam bathymetry is shown as an irregular polygon; and the most recent sludge dumpsite area is outlined as a smaller north-south rectangle.

Airgun seismic-reflection profile across the central part of the study area. Nearly flat continental-rise sediments of Neogene age lap onto an unconformity on seaward-dipping Eocene strata of the continental slope. This profile shows back-tilted blocks at the base of the slope on the rise and several truncated horizons in older, buried base-of-slope troughs or blocks within the onlapping rise strata.

Bathymetric contours. Sea-Beam soundings gridded to 125-m interval and contoured at sea aboard RV Atlantis II, during September, 1989. Depressions are shaded.

Perspective image of Sea Beam bathymetric data set. View from southwest, looking northeast, across upper rise. Lower part of continental slope on upper left. Brightness of each grid cell in this image is varied with respect to a vertical sun angle and the viewer's position. Note the terrace or trough at the base of the continental slope (A), the slope-parallel wrinkles(?) (B), an area of probable slide deformation on the upper rise (C), and depressions (D). Slight north-south bands of noise show where data swaths abut. Image courtesy of Robert C. Tyce, University of Rhode Island.

GLORIA sidescan-sonar mosaic of slope and rise off the mid-Atlantic coast of the U.S. shows the study area in relation to features of neighboring areas of the sea floor Bathymetric contours at 200, 1000, 2000, and 3000 meters. The areas of site study, Sea Beam bathymetry, and municipal sludge dumpsite are outlined.

Center: Composite illustration of GLORIA imagery and bathymetric contours of the dumpsite study area. The central part of this area was mapped using Sea Beam data, and is shown using a 10-m contour interval; contours of the peripheral area, at a 100-m interval, from Escowitz and others (1988); of the northeastern part, kindly provided by A. Shor). Note the congruence of the GLORIA backscatter pattern and the bathymetric contours. Central dark colored deposit separates lower areas, which finer scale imaging (below) shows to be furrowed. Left image: GLORIA imagery of study area without overlay. Right image: Contour lines and location of deep-towed 120-kHz sidescan-sonar imagery. Rectangle shows location of data illustrated below.

Airgun seismic-reflection profile along upper continental rise near base of slope shows strata of uppermost rise, slump structures, and faults. Labeled scarp is shown in higher resolution profile below.

High-resolution 3.5-kHz subbottom profile shows faulting and tilting of surficial acoustically laminated strata on upper rise; graben created by slumping of upper rise sediments. Labeled scarp is crossed by airgun profile above.

High-resolution 3.5-kHz subbottom profile across the seaward part of study area on upper continental rise. Arrow marks transition between area of smooth surface to the northeast, and rough, acoustically impenetrable surface, probably of blocky debris-flow deposits to the southwest. This 3.5-kHz profile shows deposit overlying surface that is seen (elsewhere) to be furrowed.

Boulders observed during dives of RV Alvin in 1989. Boulders are about 2 m in diameter. A (left). Dive 2163, water depth about 2485 m; B (right). Dive 2165, water depth about 2405 m.

Left: 120-kHz Sidescan-sonar tracklines (vehicle tracks) in relation to bathymetry. Rectangle locates next image.

Center: Mosaicked images over furrowed bottom area; 10-m contour interval. Closed-contours show depression (upper right quadrant: 2500-m contour identified) and the neighboring, downrise, elliptical high (near upper center of image). Rectangle locates the swath shown in the next image.

Right: A single swath of AMS-120 sidescan-sonar imagery, 900 m wide x 3300 m long. See location to left.

Note the surface features of the Blackhawk landslide in California. Closer view on right. Photographs from Thornbury (1954). Note that the rise features have much less relief, but may be similar to the surface features here, apart from the vertical exaggeration.

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Abstract...

Introduction...

Data and Methods...

(Bathymetric map)

(GLORIA mosaic)

Description of the sea floor...

Discussion...

Conclusions...

References Cited...