Sediment Dispersal Pattern Off the Mahanadi-Nagavali Continental Shelf, Northwest Bay of Bengal

Textural distribution patterns of seafloor sediments from the Mahanadi-Nagavali shelf, northwest Bay of Bengal, are used to evolve a model for the regional sediment-dispersal system. Mean size trends, standard deviation, skewness and correlation of negative skewness with silt/Clay ratios reveal certain patterns, each being specific to an area(s) of shelf. Sediment distribution patterns show that the near shore environment is occupied by sand and clayey sand, while the inner and middle shelf regions are covered by sandy silt, silty calcareous sand, silty clay, silty sand and sand-Silt-Clay. The outer shelf is largely covered by clayey silt. Relict carbonate deposits are preserved on the outer shelf at ∼100 m off Rushikulya to Baruva. Palimpsest sediments cover the Sonapurapeta-Bavanapadu shelf at depths of 0-60 m.

Mud dispersal in the study area offshore is caused by transport components along and across the shelf. The Mahanadi-Devi River system is the principal source of sediment for the Mahanadi-Nagavali shelf. The Nagavali and Vamsadhara rivers are a minor source of sediment towards the southern part of the shelf, and their detrital inputs are largely deposited on the shelf adjacent to the river mouths. Sediments in the study area are transported and advected southward (bottom nepheloid layers ?). The Mahanadi-Nagavali shelf response to the present hydraulic regime is recorded in the modern sand facies and the offshore mud facies, particularly the silty clays.