High-resolution diatom analysis of a core sediment in the Bransfield strait, Antarctica

Abstract

A box core BC02-EB03 obtained in the eastern basin of the Bransfield Strait (West Antarctica) shows high-resolution laminated layers of diatom ooze sediments. The basin is influenced by the warm and less saline Bellingshausen Sea water and the cold and saline Weddell Sea water. The range of diatom valves per gram of dry sediment was from 8.6 to 22.0×107 in quantitative diatom assemblage analysis. Two facies (upper and lower units) are divided upon the basis of frequency of the diatom taxa and magnetic susceptibility values. The lower unit (22~60 cm) is characterized by the lower magnetic susceptibility and higher number of diatom valves per gram sediment. It contains diatom mass influx of Chaetoceros resting spores, Corethron criophilum, and Rhizosolenia styliformis which are associated with the stratification of surface water of ice-shelf's edge by the increased meltwater between austral summer and fall. Meanwhile, the upper unit (0~22 cm) displays relative decrease of critical species and lower diatom abundances according to the relative increase of terrigenous supply during modern warming which reflects the rapid regional warming of the Antarctic Peninsula.