Late Quaternary changes in sea level and sedimentation rate along the SWcoast of India: Evidence from radiocarbon dates

摘要

We determined the C-14 dates of carbonized wood/peat and organic matter from two cores from the southwestern inner continental shelf of India, to understand late Quaternary changes in sea level and sedimentation rate. The C-14 ages of carbonized wood/peat samples from the two cores range from 10,760 +/- 130 to 9,280 +/- 150 yr BP, corresponding to Late Pleistocene-Early Holocene. These ages suggest that the sea level was much lower (> 50 m) than the present level during the Late Pleistocene-Early Holocene, when there was a luxuriant growth of mangrove vegetation and rainfall in the region. Later, due to transgression during Early Holocene, the mangrove vegetation was submerged and buried under a thick column of sediment, giving rise to carbonized wood/peat. The C-14 ages reported for the present-day onshore peat and, shell material at various depths along the SW coast of India reveal that after 6400 yr BP, the sea level receded and stabilized at the present level. The results indicate that: (1) the present-day sedimentation rates in the study area are generally comparable to those reported for similar water depths off the Karnataka coast, but higher than that reported for the Kerala coast; (2) sedimentation rate at a site is controlled by its proximity to river mouths and it decreases offshore; and (3) sedimentation rate during the Pleistocene-Holocene transition period is 6-7 times higher compared to the Holocene.