Physical properties of a long sediment core from the central Indian Basin
Abstract
In a 7.5 m-long box core, collected at 9 degrees S and 77 degrees E from 5400 m water depth from the Central Indian Basin, geotechnical properties clearly reflect the Plio-Pleistocene boundary. It is marked by a drastic change in the physical properties and clay mineralogy, indicating a sedimentary hiatus or a volcanic ash layer. The shear strength increases from 10 to 13 kPa at this boundary, and despite higher clay and montmorillonite contents, the water content and liquid limit decrease drastically, showing the same values (WC and LL = 94%). These indicate the highly compressed and consolidated nature of this layer, which may be due to overburden pressure of the thick sediment column. Wet-bulk density increases from 1.2 to 1.5 g/cc and porosity decreases from 87 to 71 per cent at this layer. The boundary layer is about 30 cm thick and is devoid of any radiolarian fossils, which may be attributed to either sudden climatic change or to volcanic activity, which precluded preservation of radiolarian fossils
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