Deglacial environments in the northeastern of South Shetland Islands, Antarctica: evidence from the high resolution diatom record

Abstract

A total of 70 species and varieties belonging to 31 genera are identified from 300~350 cm horizons of the Core GC03-C1 in the South Shetland Islands, Antarctic Peninsula. High number of diatom valves per gram of dry sediment was observed in core, ranging from 0.7~6.1×10^7/g. The Holocene diatom assemblages from the core are dominated by Fragilariopsis kerguelensis and Eucampia antarctica which are about 45.7% of the total. Three diatom subzones are identified on the basis of frequency of the index species throughout the section: diatom assemblage subzone I-a from 350 to 331 cm (late Last Glacial Maximum), diatom assemblage subzone I-b from 330 to 313 cm (deglaciation) and diatom assemblage subzone II-a from 312 to 300 cm (early Holocene). The paleoenvironmental conditions from the late LGM to early Holocene can be subdivided into three intervals based on diatom assemblages: 1) diatom assemblage subzone I-a condition with persistent seasonal sea-ice cover and summer upwelling of Antarctic Circumpolar Deep Water, 2) diatom assemblage subzone I-b condition with collapse of land glaciers and influx of meltwater with increasing warming, and 3) diatom assemblage subzone II-a open ocean conditions more affected by Antarctic Circumpolar Current.