Biological productivity, terrigenous influence and noncrustal elements supply to the Central Indian Ocean Basin: Paleoceanography during the past approx. 1 Ma

Abstract

A 2 m-long sediment core from the siliceous ooze domain in the Central Indian Ocean Basin (CIOB; 13 degrees 03'S: 74 degrees 44'E; water depth 5099 m) is studied for calcium carbonate, total organic carbon, total nitrogen, biogenic opal, major and few trace elements (Al, Ti, Fe, K, Mg, Zr, Sc, V, Mn, Cu, Ni, Zn, Co, and Ba) to understand the productivity and intensity of terrigenous supply. The age model of the sediment core is based on U-Th dating, occurrence of Youngest Toba Tuff of approx. 74 ka and Australasian microtektites of approx. 770 ka. Low carbonate content (< 1%) of sediment core indicates deposition below the carbonate compensation depth. Organic carbon content is also very low, almost uniform (mean 0.2 wt%) and is of marine origin. This suggests a well-oxygenated bottom water environment during the past approx. 1100 ka. Our data suggest that during approx. 1100 ka and approx. 400 ka siliceous productivity was lower, complimented by higher supply of terrigenous material mostly derived from the metasedimentary rocks of High Himalayan crystalline. However, during the last approx. 400 ka, siliceous productivity increased with substantial reduction in the terrigenous sediment supply. The results suggest that intensity of Himalayan weathering, erosion associated with monsoons was comparatively higher prior to 400 ka. Manganese, Ba, Cu, Ni, Zn, and Co have around 90% of their supply from noncrustal (excess) source and their burial to seaøoor remained unaffected throughout the past approx. 1100 ka.