Contemporary Epicontinental Sedimentation and Shelf Grading in the Southeast Bering Sea

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Abstract
Sediments from the southeastern Bering Sea have been studied to elucidate post-Wisconsin transgressive sedimentation. The study of contemporary sediments from this shallow, broad, epicontinental sea reveals the processes of sediment transport and deposition and evolution of subarctic shelf sediments. The area investigated extends over 1.5 × 105 km2 and has a smooth profile bottom with a remarkably gentle slope of about 2.4 × 10−2 percent. The entire shelf is covered by sand, and the mean grain size generally decreases with increasing depth. The sources for the sediments in the southeastern Bering Sea shelf lie in the immediately adjacent landmass. The distribution of minerals in the sediments suggests that sedimentary, high metamorphic, and igneous minerals originate in the north and east, and the source for volcanic minerals lies in the south. Sediment dispersal is influenced by wave energy and marine currents. Two broad depositional environments are suggested by the scatterplots of grain-size parameters. On the basis of available meteorological data for severe annual storms in this area, theoretical wave dimensions were computed. Such storms apparently generate waves about 200 m long and 10 m high with significant disturbance of the bottom sediment to depths greater than 100 m. Sediment textural differences, shelf grading, and sediment transport from shallow shelf to deeper parts are attributed to storm-generated waves.

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