Postglacial marine diatom record of the Palmer Deep, Antarctic Peninsula (ODP Leg 178, Site 1098) 2. Diatom assemblages

Abstract

The distribution of Late Pleistocene to Holocene diatom assemblages from Ocean Drilling Program (ODP) Leg 178 Site 1098 (Palmer Deep) is described and compared using multivariate statistical methods (cluster analysis and analysis of variance). Five assemblages are identified from Site 1098, which are correlated with the climatic zones identified previously in the Palmer Deep [Domack et al., 2001]. A Thalassiosira diatom assemblage characterizes the "deglaciation phase" (13.2-11.0 ka) and was deposited during glacial retreat at the end of the regional Last Glacial Maximum. A well-preserved Rhizosolenia assemblage was deposited during a "climatic reversal" (11.0-9.0 ka) and indicates periods of seasonally open water with diatom blooms. An open water Fragilariopsis kerguelensis assemblage characterizes the mid-Holocene climatic optimum (9.0-3.7 ka). In the Neoglacial (late Holocene, <3.7 ka), climatic cooling, increased sea ice cover, and increased wind are inferred from a Cocconeis assemblage. During the climatic optimum/Neoglacial transition (4.4-1.8 ka), laminae characterized by Corethron criophilum were preserved. It is uncertain whether the laminae represent short-lived (interannual) bloom events with high settling rates or have been deposited over longer time periods.