BOTTOM CURRENT-CONTROLLED SEDIMENTATION AND MASS WASTING IN THE NORTHWESTERN SEA OF OKHOTSK

Abstract

Quaternary sedimentation in the northwestern Sea of Okhotsk, where tidal and thermohaline currents are active, was studied using 8443 km of high-resolution air gun profiles from four cruises. It is characterized by: (1) bottom current-controlled processes, which lead to widespread deposition of contourite drifts and sediment waves on the North Okhotsk continental margin and the northernmost Sakhalin slope, as well as to erosion and sediment reworking on the northern Sakhalin shelf; (2) mass wasting triggered probably by shallow earthquakes, by gas hydrate instability during sea-level lowstands leading to slumps and debris flows in the western Derugin Basin; (3) deposition of the fluvial load of the River Amur, which results in sediment drift bodies and prograding lowstand wedges during glacial periods, and to contourite drifts and a ‘fan’ during interglacial times; and (4) ice-rafted detritus and hemipelagic sedimentation interrupted by episodic turbidity current activity, especially in the Derugin Basin and its northern, eastern and southern flanks.