Intraslope Basin Deposits and Potential Relation to the Continental Shelf, Northern Gulf of Mexico

摘要

The continental slope in the north central Gulf of Mexico has a very hummocky topography in which the highs are underlain by diapairs. The topographic depressions, or intraslope basins, can be divided into blocked-canyon basins, interdominal basins, and collapse basins. Only the blocked-canyon basins may have a direct relationship to the contential shelf. An acoustical sequence, typical for blocked-canyon intraslope basins, starts with a semitransparent or a chaotic seismic facies, overlain by a zone with discontinuous, slightly irregular, parallel reflectors, and topped by continuous, distinct, parallel reflectors. Inferred lithologies and process (bottom to top) are: sandy, silty, and clayey; and density currents and slumps, low density turbidity currents, and pelagic-hemipelagic depositions. Transport and deposition can be related to relative changes in sea level; the lower zero being deposited during a falling sea level and perhaps during the intial rise, the middle zone during high sea level stands. When sediments, emplaced on the outer shelf and upper slope, are put in motion as a result of slope failure, they can move downslope for long distances through channel - like depressions. Different sediment thicknesses in the channel and on the diapiric highs will cause differential loading which results in diapiric activity. As a consequence, damming of a channel can result and an intraslope basin is formed. (Reprinted)