8. GRAIN SIZE AND DIATOM CONTENT OF HEMIPELAGIC SEDIMENTS AT SITE 697, ODP LEG 113: A RECORD OF PLIOCENE-PLEISTOCENE CLIMATE 1

• Main Authors: P E Barker, J P Kennett
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1990
• Subjects: Antarctic; West Antarctica; Antarc*; Antarctica; Ice Sheet; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1071.2542; http://www-odp.tamu.edu/publications/113_SR/VOLUME/CHAPTERS/sr113_08.pdf

ABSTRACT At Site 697 a 320 m thick Pleistocene and Pliocene section was recovered, consisting of hemipelagic terrigenous mud with varying amounts of diatoms, thin altered ash layers, and ice-rafted debris (IRD). Sedimentation rates range from 41 m/m.y. (upper Pleistocene) to 150 m/m.y. (lower Pliocene). Diatom percentage and sediment grain-size have been measured for the whole section with approximately one sample per 5,000 yr. IRD is most abundant in the lower Pliocene (sediments older than 4.5 Ma) following the first major West Antarctic glaciation. A decrease in IRD to near-zero above 3.2 Ma may record a transition from valley glaciers to a grounded ice-sheet on West Antarctica. Bottom current flow, recorded in sediments as the proportion of silt, was at a maximum around 3.0-3.3 Ma then gradually decreased until 0.5 Ma. In the upper Pleistocene, maxima in diatom percentage are assumed to occur during interglacials, implying reduced sea-ice cover; maxima in silt percentage correspond to diatom maxima, implying stronger bottom water flow during interglacials.