Holocene oceanographic and glacial changes recorded in Maxwell Bay, West Antarctica

Abstract: Three Holocene core sections from Maxwell Bay, South Shetland Islands, West Antarctica are investigated, using MS, grain size, TOC, foraminifera, δ18O and δ13C, 14C, and 210Pb, in order to examine Holocene oceanographic, glacial and climatic changes in the region. They come from 190, 221, and 333m water-depths and the bay margin-proximal locations, complementing earlier studies from the deep central part. The three records vary between locations and reflect combined marine and terrigenous influence from the open ocean and surrounding islands, respectively. The longest and best dated composite section comes from the inner part of the bay (core JTC/JPC-17) and extends back to 6.3calkyr BP, close to the termination of the Holocene Climatic Optimum. A combination of dating problems and mixed foraminiferal assemblages prevented reliable interpretation of core JPC-15 from the outer part of the bay. Core JPC-16, collected from the inner bay near the inlet between King George and Nelson Islands, revealed repeated highs in planktonic Neogloboquadrina pachyderma occurrence during last 3000yr. These highs are interpreted as indicating periods of decreased meltwater flow into the bay, and thus greater influence of open-marine surface-waters. Core JTC/JPC-17, located closest to King George Island and the Collins Ice Cap, records increased glacial conditions at ~2000calyr BP. This event is recorded by turbidite deposition at core site JPC-16. Major components of the benthic foraminiferal assemblage indicate decreasing tolerance to near-glacier or near-shore conditions, however, local climate variability appears to have overall little impact on benthic foraminiferal biota. Thus, it is unlikely that, in similar settings, recent warming would be strongly manifest as changes in benthic foraminiferal communities. Stable isotopic analysis is based on Cassidulinoides parkerianus and Globocassidulina biora. Subtle decrease in δ18O at ~3500calyr BP, followed by episodic increases at ~1000calyr BP and in the youngest part of the record, appear to correlate with the period prior to the beginning of the Neoglacial, with Medieval Warm Period, and with post Little Ice Age warming, respectively. The latest event is also marked by a significant increase in sediment accumulation rate in the second half of the 20th century. [Copyright &y& Elsevier]