Abyssal sediment erosion in the Central Indian Basin: Evidence from radiochemical and radiolarian studies

Abstract

Radiochemical analyses of three spade cores collected around 78°E between 10°S and 12°S from the abyssal depths in the Central Indian Basin yield an average accumulation rate of 2 mm/ka. The ratios of 230Th flux in the sediments to its production rate in the overlying water column ( Fa Fp ) are extremely low (∼0.2). This fact, and the absence of Collosphaera invaginata (first appearance datum, 150–200 ka), an index radiolarian species of Neogene Radiolarian Zone 1, indicate intense erosion and lateral transport of younger sediments from this region. The radiochemical and radiolarian biostratigraphic evidence for nearly 175 ka of erosion of the chronological record of the sediments in this region has been attributed to the effect of turbulent Antarctic Bottom Water entering the Central Indian Basin through the northern saddles of the Ninety East Ridge.