The depositional history of late Quaternary sediments around Mangalore, west coast of India

Netravati and Gurpur are relatively large rivers drain the hinterland near Mangalore, form a common estuary before they debouching into the Arabian Sea. Lithologic successions observed in a number of bore holes and dug wells indicate that Netravati and Gurpur rivers drained into the Arabian Sea independently during the last glacial period when the sea level was about 100-138 m below the present level. In contrast to Netravati, the lower course of Gurpur has migrated southerly in four stages for a distance of 8 km and at present forms a common estuary with the Netravati river. This is because of drowning of the river channel due to rapid rise in sea level during the early Holocene and growth of barrier spit under the strong influence of southerly littoral currents during late Holocene when the sea level was relatively stabile. The rate of infilling of alluvial and marshy sediments during late Pleistocene to early Holocene (0.5-5.0 mm/yr and 0.33-4.33 mm/yr respectively) is about two-three times slower than that for barrier spit sands accumulation (0.14-1.14 mm/yr) during the late Holocene.