Holocene submarine terraces on the western continental shelf of India; implications for sea-level changes

Abstract

Detailed echosounding, side-scan sonar and high-resolution seismic-reflection profiling on the western continental shelf of India have revealed a series of submarine terraces at different depths between the outer fringe of the inner shelf and the shelf break, being more common between 11~' and 20~'N. The terraces are prominent between water depths of 50 and 115 m and occur at six distinct levels: (1) 55-60 m, (2) 65-70 m, (3) 75-80 m, (4) 85-90 m, (5) 95-100 m and (6) 110-115 m. They are categorized into: (1) wave-cut terraces, (2) coral/algal reef-induced terraces and (3) palaeo-beach/barrier terraces. The reef-induced terraces occur predominantly in the carbonate-rich province (20~'-13~'N), while both the wave-cut and palaeo-beach/barrier terraces are discernible in the terrigenous regime, which is located north and south of these latitudes. Despite their genetic differences, their evolution is ascribed to reef growth, progaradation and wave activity during the lowstands of sea level and reflect different phases of stillstands of the late Pleistocene to mid-Holocene age