Holocene Palaeoenvironmental change at the mouth of Sabarmati River, Gulf of Khambhat, Western India

Abstract

The fluvio-marine archives have been widely used to assess the imprints of land-sea interaction during the Holocene period, which has been enigmatic in terms of changes in environmental conditions. To comprehend the fluvial-marine interactions during the Holocene period in response to relative sea level changes, a sedimentary record has been studied from the mouth of the Sabarmati river at the Gulf of Khambhat (western India), which has also hosted mighty Harappan cultural centres during Holocene period. We employed a suite of multiproxy technique (sedimentology, OSL dating, geochemistry and foraminiferal content) from a terrace sequence at the Sabarmati River mouth (i.e. Vadgam). Based on an optical dating, the studied terrace sequence spans from 11 ± 1 ka to 1.3 ± 0.3 ka (11300–1300 year BP) covering almost entire Holocene period. The multiproxy investigation identified three distinct depositional zones at the site, namely zone 1 (11300–5300 year BP), which is characterised by a predominantly fluvial to marginal marine environment, zone 2 (5300–3700 year BP), which indicates a change to a marginal marine to predominantly marine environment, and zone 3 (3700–1300 year BP), which demonstrates a change to an again mixed environment. A present analogue to the palaeoenvironments in the area is provided by the deposition that is still occurring at the mouth of the Sabarmati River under the estuarine tidal environment. The variations in the rate of sedimentation and the source of the sediments are consistent with the environmental change, which will be driven by the changes in climatic circumstances in connection with the rapid sedimentation near the mouth of the Sabarmati River.