Sediments on the Southeastern Flank of the Bermuda Pedestal

摘要

The Bermuda Pedestal has steep slopes ranging from 30 deg near the top to 2.5 deg near the bottom. Seismic records indicate sparse sediment cover on the slopes and an absence of large amounts of slump material on the lower slopes of the pedestal. This suggests that the apron at the base is not recent; rather, it may be a remnant of a talus slope associated with mid Eocene-Oligocene volcanic and erosional events. The carbonate content of surface and near-surface sediment (quaternary) is generally high, decreasing only slightly with increasing depth in spite of probable extensive dissolution. Carbonate constituents and composed of both shallow platform and pelagrc organisms. Constituents particles identified by scanning electron microscopy correlate well in most instances with mineralogy identified by X-ray diffraction. Clay mineral content is low to nonexistent on the pedestal. In general, grain sizes tend to be coarser near the top of the pedestal, but anomalously high percentages of sand were found in a few places low on the flank and apron of the pedestal. Sediment deposition on the pedestal is discontinuous and episodic, a combination of pelagic rain and redeposition by rapid-transport processes such as slumping, turbidity currents, and resuspension and dispersion of sediment by eddies and currents.