Timing of deposition and failure of steep carbonate slopes, Tongue of the Ocean, Bahamas
- Univ. of Miami, FL (United States)
Steep marginal slopes around the Tongue of the Ocean record deposition during the early rise of sea level following the last lowstand some 18,000-21,000 years B.P. Coarse-grained skeletal packstones and grainstones derived from the overlying escarpment were deposited on slopes of 35-45{degree} and rapidly cemented in place. Deposition by rockfall and grainflow processes resulted in a series of elongate lenses oriented parallel to the slope. These lenses are generally less than 0.5 m thick and pinch out downslope within tens of meters. Radiocarbon dating indicates that active deposition on the slopes ceased abruptly about 10,000 years ago as sea level rose above the escarpment and began to flood the top of Great Bahama Bank. Fine-grained, nonskeletal sands and muds derived from the platform are presently by passing these slopes resulting in a 'modern' example of a drowning unconformity. Although these slopes are no longer sites of active deposition, they are still influencing the ultimate record of slope sedimentation. Arcuate, concave-up cracks in the cemented slope indicate zones of weakness and possibly represent areas susceptible to slope failure. These cracks are a few centimeters wide and may extend for tens of meters across the slope. Post-depositional failure of the slope has been observed at several locations. These slide/slump scars are as much as 30 m across and may extend downslope for 70-80 m. Large blocks, some more than 10 m across, derived from failure of the relict slope have been transported for tens or hundreds of meters downslope. The release and transport of such blocks may be one mechanism by which turbidity currents are initiated in deeper slope environments.
- OSTI ID:
- 5677332
- Report Number(s):
- CONF-910403-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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