Abstract

The Chukchi Sea is a broad, shallow (<60 m deep), essentially nontidal (tidal range < 10 cm), epicontinental sea that is ice covered 8 to 9 months of the year. A northward-flowing coastal current (velocity ± 200 cm/s) apparently controls the sediment distribution and texture along the east side of the sea. Extensive surficial gravel lag deposits, gravel-sand ribbons, sand-wave fields, and sandbanks record areas of erosion and deposition as well as sea bed processes within this current-dominated part of the northeastern Chukchi Sea. Reconnaissance investigations along the east boundary of the coastal current, using side-scan sonar, high resolution bathymetric and seismic profiles, television observations, and sediment sampling, define the major sea bed features, sediment pathways, and areas of sediment deposition. Sediment input to the coastal region is low, and over much of the sea floor a thin sediment cover of sand and gravel overlies bedrock. Two capes represent the major sediment depocentres. Arcuate sandbanks covered with sand waves, which may exhibit the same or opposed orientations on the ridge flanks, form off one cape where the coastal current is far offshore. These sand banks migrate seaward, where ice groundings and the coastal current erode the sediment and form fields of northward-migrating sand waves. Where the coastal current approaches the shore, gravel-sand ribbons oriented parallel to the shore or fields of northward-migrating sand waves form. These sand-wave fields are more than 30 km long and are elongate parallel to the coast; the bed forms are 1 to 3 m high oriented normal to the coastal current trend. The sand bodies that form as a result of sediment transport and deposition within the coastal current are as much as 10 to 12 m thick.