First discovery of channel-levee complexes in a modern deep-water carbonate slope environment

Abstract

New high-quality high-resolution seismic data along the western slope of the Great Bahama Bank reveals a present-day channel-levee complex developed in a pure carbonate setting. This complex grew over two buried complexes separated by erosion surfaces, suggesting both the continuity of downslope gravity-driven processes along this carbonate slope, and channel migration through avulsion, processes similar to what happens along siliciclastic slopes. Complex morphology and geometry are similar to analogs described in siliciclastic systems, but the size of the presented carbonate complex is smaller by a factor of ten. Integrating high-resolution seismic and core studies shows that this complex was built by the stacking of gravity-flow deposits, including turbidites. It presently is inactive and buried by deposits from hemipelagic fallout or low-energy density processes channeled by the gully network; Recent sediments are reworked by along-slope bottom currents dominated by internal tides. The discovery of these channel-levee complexes has implications both on the conceptual models describing the behavior of carbonate slope systems and on hydrocarbon exploration by enhancing the reservoir-bearing potential of carbonate slopes.