Sedimentary records of paleoenvironmental changes during the last deglaciation in the Ulleung Interplain Gap, East Sea (Sea of Japan)

Abstract

The Ulleung Basin in the East Sea (Sea of Japan) is a semi-enclosed basin surrounded by shallow sills and straits. Detailed observation of X-radiographs and thin sections of core sediments from the Ulleung Interplain Gap reveals five mud facies: laminated mud, crudely laminated mud, homogeneous mud, bioturbated mud and laminated Mn-carbonate mud. The laminated and homogenous muds were most likely deposited from turbidity currents, whereas the bioturbated and crudely laminated muds were formed by pelagic/hemipelagic sedimentation under oxic and anoxic bottom-water conditions, respectively. The laminated Mn-carbonate mud occurs at the lithologic boundary between the turbidite and hemipelagic laminated mud (last glacial) and the pelagic bioturbated mud (Lateglacial to Holocene). Mn-carbonates were formed at the sediment-water interface, probably reflecting an abrupt change in bottom-water oxygenation caused by sea-level rise during the last deglaciation. Profiles of redox-sensitive elements also support an anoxic to oxic change of bottom-water conditions during this period. (C) 2001 Elsevier Science B.V. All rights reserved.