(Figure 2) Diatom relative abundance of sediment core PS58/254-1

• Main Authors: Konfirst, Matthew Alan, Scherer, Reed P, Hillenbrand, Claus-Dieter, Kuhn, Gerhard
• Format: Dataset
• Language: English
• Published: PANGAEA 2012
• Subjects: Accumulation rate; mass; Actinocyclus actinochilus; Actinocyclus ingens; AGE; ANT-XVIII/5a; AWI_Paleo; Azpeitia tabularis; Calculated; Chaetoceros spp.; Counting; diatoms; DEPTH; sediment/rock; marine; reworked; sea-ice; total abundance per unit sediment mass; Diatoms tropical/subtropical; Distephanus speculum; Eucampia antarctica; Fragilariopsis curta; Fragilariopsis kerguelensis; Fragilariopsis separanda; Hemidiscus karstenii; KL; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Piston corer (BGR type); Polarstern; PS58; PS58/254-1; Rhizosolenia spp.; Rouxia antarctica; Rouxia constricta; Southeast Pacific; Thalassionema spp.; Thalassiosira elliptipora; Thalassiosira fasciculata; Thalassiosira gracilis; Thalassiosira lentiginosa; Thalassiosira oestrupii; Thalassiosira oliverana; Thalassiosira tetraoestrupii; Thalassiosira tetraoestrupii var. reimeri; Thalassiothrix antarctica; Amundsen Sea; Antarctic; Island Bay; Pacific; Pine Island Bay; West Antarctic Ice Sheet; Antarc*; Antarctica; Ice Sheet; Pine Island; Sea ice
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.779253; https://doi.org/10.1594/PANGAEA.779253

The goal of this study is to assess the changes that have occurred during the Mid-Pleistocene Transition, an important transitional period in cryosphere evolution, by examining the siliceous microfossil record of sediments collected proximal to a major ice drainage outlet for the West Antarctic Ice Sheet. Core PS58/254 was collected from a sediment drift on the upper continental rise in the Amundsen Sea, directly offshore from Pine Island Bay, one of the three main discharge areas for the West Antarctic Ice Sheet (WAIS). Published data on physical properties, geochemical composition, grain size and clay mineral assemblages are complemented here by a high-resolution record (sample spacing 10 cm) of the siliceous microfossil assemblages (diatoms and silicoflagellates). Between 1200 ka and 621 ka, the assemblage is relatively diverse, with Actinocyclus ingens, Thalassiothrix antarctica and Fragilariopsis kerguelensis dominating the assemblages, but diatom abundance is variable from low to barren. Additionally, the occurrence of A. ingens, Thalassiosira elliptipora and Thalassiosira fasciculata is used to confirm and further refine the existing age model and extend it back to 1200 ka. Species composition during the last ca. 621 ka is dominated by F. kerguelensis, which consistently comprises 80-90% of the assemblage. A clear relationship between diatom abundance and glacial/interglacial variability is apparent after 621 ka, which resembles the glacial-interglacial variability previously observed in other proxy data. A significant change in both sediment composition and diatom assemblages is observed at 621 ka. This change concurs with the last abundant occurrence of A. ingens and the end of the Mid-Pleistocene Transition (MPT, i.e. the onset of modern eccentricity/precession-paced glacial cycles around 650 ka). We suggest that during interglacial periods after 621 ka the Amundsen Sea Low pressure system shifted seasonally southwestwards towards the shelf and thereby increased the advection of relatively warm ...