Late Pleistocene sedimentation: A case study of the central Indian Ocean Basin

Abstract

Concentration-depth profiles of excess sup(230)Th have been measured in five sediment cores from the central Indian Ocean Basin to determine their accumulation rates and excess sup(230)Th flux to the depositional environment. Sedimentation accumulation rates ranged between 1 and 5 mm ky sup(-1). The excess sup(230)Th inventories in the cores range from 44 to 481 dpm cm sup(-2), considerably lower than that expected from its production in the overlying water column. These low excess sup(230)Th inventories (relative to its production) have been attributed to the effects of winnowing by bottom currents. The absence of sup(230)Th sub(ex) in core (Sagar Kanya-176) has been attributed to the lack of sediment deposition in this area causEd. by the influence of Antarctic Bottom Water (AABW). This study shows that the deposition of biogenic silica and lithogenic components exhibited orders of magnitude variations during Late Pleistocene. The biogenic flux variation are attributed to productivity changes while the episodic variations in the non-biogenic flux could result from major changes in the influx of terrigenous materials via the Ganges-Brahmaputra