PALAEO Late Holocene palaeoclimatic records from lake sediments on James Ross Island, Antarctica

Sediment profiles from several lakes/ponds in the northern, ice-free area of James Ross Island, Antarctica, were the subject of a multi-disciplinary palaeoenvironmental investigation. The results, obtained from lithological, geomagnetic, geochemical nd diatom analyses, and the frequency of Branchinecta eggs, were evaluated with multivariate statistics and provide a fairly detailed picture of climate change during the last 5000 years. New radiocarbon dates are combined with previously published 14C dates, so as to date the palaeoenvironmental and palaeohydrological hanges identified by the stratigraphic studies. In combination with the findings of glacial geological studies our data suggest hat the Brandy Bay glacier began to recede rapidly just before 5000 yr B.P., due to calving and moisture starvation caused by cold and arid conditions. In one of the ponds studied gypsum began to precipitate as a consequence of these conditions when the influence of glacial meltwater ceased. This hypothesis was tested by hydrochemical modeling. At approximately 4200 yr B.P. the climate became more humid (and warmer) and the pond supported a fairly diverse biota, which included a variety of diatom species and, for example, Branchinecta gaini, a crustacean that feeds on benthic cyanobacterial mats. The Brandy Bay glacier probably advanced uring this humid period, but the advance was interrupted by subsequent arid conditions which started at 3000 yr B.P. During this arid phase, glaciers became completely absent from the study area. As a result formerly large lakes, fed by glacial meltwater, transformed int