The constructive functions of tropical cyclones and tsunamis on deep-water sand deposition during sea level highstand: Implications for petroleum exploration
Empirical data on tropical cyclones (meteorological phenomena) and tsunamis (oceanographic phenomena] from the Indian, Atlantic, and Pacific Oceans reveal that they are highly powerful and frequent events during the present sea level highstand. Tropical cyclones have the power to stir up the entire water column across the United States Atlantic continental shelf, which is 100 km (62 mi) wide and 200 m (656 ft) deep at the shelf edge. Maximum measured velocities of cyclone-triggered bottom flows are commonly in the range of 100-300 cm s~(-1) (39-117 in. s~(-1)) on the shelf and 200-7000 cm s~(-1) (78—2730 in. s~(-1)) in submarine canyons and troughs. At these high velocities, even gravel-size grains would be eroded and transported. Data also reveal that tropical cyclones accelerate deep-water siliciclastic deposition by transporting sediment seaward across the open shelf, over the shelf edge, and via submarine canyons into deep-water environments during the present high-stand. Modern shelf edges are composed of both relict and active sand bodies that are suitable for delivering sand and gravel into the deep sea. Estimates suggest that 200,000 tropical cyclones (Bay of Bengal [Indian Ocean] and Atlantic Ocean) and 140,000 tsunamis (Pacific Ocean) would have occurred during the present high-stand interval. During Hurricane Hugo (September 1989), more than 2 million kg of sediments were flushed down the Salt River Submarine Canyon (St. Croix, U.S. Virgin Islands) into deep water.
G. Shanmugam
Department of Earth and Environmental Sciences, University of Texas at Arlington, P.O. Box 19049, Arlington, Texas