About This Item
Share This Item
Based on analysis of 1,350 km of high resolution, 5 cu in. air-gun and 3.5 kHz seismic reflection profiles, as well as 30 piston cores, the open ocean, windward, deep carbonate bank margin north of Little Bahama Bank has been divided into upper and lower slope facies. The seismic character of the post-Paleocene upper slope unit (200 to 1,000 m water depth) consists of a low-energy slope-front fill facies characterized by parallel to subparallel reflectors that downlap onto a regional unconformity near the Paleocene-Eocene boundary. Sediments of this upper slope facies are interpreted to be primarily fine-grained pelagic carbonates. In contrast, the post-Paleocene unit on the lower slope (1,000 to 1,300 -m water depth) consists of a variable energy chaotic-fill facies char cterized by hummocky/discordant to wavy subparallel reflectors. Sediments of this facies are interpreted as coarse, high-energy mass transport deposits such as turbidites and debris flows. Detachment scars on the upper slope and erosional gouge on the lower slope indicate that submarine slides and sediment gravity flows originated on the upper slope. The sediment gravity flows have bypassed the fine-grained upper slope facies via numerous evenly spaced small canyons, which act as a "line source," and were deposited at the base of the slope in a broad "apron" rather than a fan. The seaward transition in the lower slope chaotic fill facies from hummocky/discordant to wavy subparallel reflectors suggests that the sediment gravity flows become thinner and more "distal" seaward. Recurrent fau ting and oversteepening of unlithified carbonate slopes are believed to be responsible for the generation of mass movements. Similar facies relations should be recognizable in the rock record. In terms of hydrocarbon exploration, the coarse, lower slope sediment gravity flow facies would appear to have the greatest reservoir potential.
End_of_Article - Last_Page 1004------------