Long-Range Side-Scan Sonar Survey of Eastern Gulf of Mexico

D. C. Twichell, L. M. Parson, P. C. Valentine, C. E. Paull

The eastern Gulf of Mexico was mapped by long-range side-scan sonar (GLORIA or Geologic Long Range Inclined Asdic) to describe the morphology and sedimentary processes of this part of the gulf. The most pronounced feature in the area is the Florida escarpment, a steep carbonate cliff that separates the carbonate rocks of the Florida platform from the terrigenous deposits of the deep gulf. The escarpment and the slope above it have been surveyed from Desoto Canyon (29°N) to the Straits of Florida (24°N), and three distinctive geomorphic provinces have been observed. Between Desoto Canyon and 28°N, the escarpment has about 1,000 m of relief, and its face is smooth. Between 28°N and 27°N, the escarpment has about 1,500 m of relief and a series of val eys whose highly reflective floors are separated by ridges that have a lower acoustic reflectivity. Slide scars on the slope above the escarpment and small debris aprons at the mouths of some of these valleys suggest active downslope sediment movement. South of 27°N, the escarpment has more than 1,500 m of relief and much of it is deeply incised by box canyons spaced 7-15 km apart. These canyons have sediment-filled floors and nearly vertical headwalls. Slumps originating on the slope above the escarpment in water depths of 500-1,500 m feed into these canyons. Mass wasting is an important process on the slope above the escarpment, and differences in the morphology of the escarpment suggest that different erosional processes act on different parts of it.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.