Reconstruction of palaeo-depositional environment in North-Eastern Arabian Sea

Abstract

A sediment gravity core recovered from the North-Eastern Arabian Sea was investigated for sediment grain size, total organic carbon (TOC) and selected trace metals to understand the changes in the depositional environment over time. The core exhibited three distinct zones of sediment, the lower zone I, middle zone II and upper zone III, representing the varying conditions of sediment deposition. The lower zone is dominated by the silt-sized fraction with low organic carbon that revealed a shallow depositional environment and led to oxidation of organic matter, while the low metal concentration in this zone was either due to the low intensity of monsoon or the dilution by biogenic components and aeolian sediment influx. On other hand, the middle zone represented a transition phase where metal along with clay and organic carbon concentration started increasing due to strengthening monsoon intensity. Further, the upper zone that represented the Holocene sediments pointed to the increase in concentration of metals Al, Fe, Co and Cu that indicated an increase in the intensity of the South-West Monsoon and led to large fluvial inputs. TOC also increased towards the surface, indicating an increase in productivity that was controlled by South-West Monsoon.