Depositional and erosional features of the inner shelf, northeastern Bering Sea

Abstract

Sonographs and bathymetric profiles from water depths less than 1-5 m in the Nome-Solomon, Port Clarence, and Yukon Delta areas of the Alaskan Bering Sea coast show features generated by waves, currents, and drifting ice. The surficial sediments in the Nome-Solomon and Port Clarence areas range in grain size from sand to boulder gravel and have many surface features visible on sonographs, whereas the sediments off the Yukon Delta are fine sands and silts that have few such features. Materials in the Nome-Solomon and Port Clarence areas have been segregated by grain size into ribbons and irregular, elongate, and lobate patches. The sand patches commonly have convex-up profiles and probably rest on gravel lag deposits that are exposed in adjacent gravel patches. Coarse sand and fine gravel patches and ribbons are characterized by symmetrical ripples, spaced 0.5 to 2 m apart, that could only have been generated by storm waves. Gravelly sand waves in the Nome-Solomon area were formed by westward shore-parallel currents. Boulder gravel ridges in this area are of unknown origin. Sand and gravel ribbons are common near the entrance to Port Clarence. Unlike ribbons elsewhere, which have been attributed to tidal or other currents. the ribbons in the port Clarence area show features suggesting generation by storm waves. These ribbons are oriented approximately normal to the associated large wave ripples, and both the ripples and ribbons vary in orientation in ways that can be explained as effects of wave refraction over a shoaling bottom. Ribbonlike features of unknown origin occur locally on the Yukon delta front. Ice-gouged furrows, though less common than in areas farther offshore. occur in all the nearshore areas studied. The gouges are 5 to 15 m wide, as much as hundreds of meters long. and usually less than 0.25 m deep.