Dating of Sediment Layers and Sediment Accumulation Studies along the Western Continental Margin of India: A Review

Abstract

Modern surface sediments and organic matter/peat in sediment cores along the western continental margin of India have been dated by excess 210Pb and conventional or accelerator mass spectrometry 14C techniques. We have established an extensive database of these radiometric dates and related parameters, and have calculated sedimentation rates. Modern sedimentation rates are higher (1.8-19.0 mm/yr) on the continental margin of northwestern India and decline (0.01-2.6 mm/yr) toward the southwest. This trend is attributed to differences in load-carrying capacity of the rivers and lithology of the adjacent hinterland. Sedimentation rates decrease away from the coast, except for higher sedimentation rates at few places on the mid-slope compared to inner slope regions. The data reveal lateral as well as temporal variations in accumulation rates, which are explained in terms of environment of deposition and paleomonsoon conditions. The onset of intensive monsoonal conditions during the Holocene is reflected in very high sedimentation rates on the inner shelf. Peat and carbonized wood layers in the inner shelf cores are of Early Holocene age and indicate marine transgression. Age inversions in the cores of continental shelf and slope regions are attributed to either sediment slumping or reworking and redeposition of foraminifera shells. This study provides additional information to the worldwide database for continental margin sedimentation, and is useful for understanding Late Quaternary sedimentation records, sea level changes, the Holocene marine transgression event, the role of Last Glacial Maxima (LGM), and climatic changes in the input of terrigenous sediments to continental margins.