Climatic Change during the Pleistocene/Holocene Transition in Upland Western Maharashtra, Western India

Abstract

Upland Western Maharashtra is drained by the Krishna and Godavari rivers and their tributaries. These rivers have their source in the Western Ghats and flow into the Bay of Bengal. The region is semi-arid (800–400 mm rainfall) due to its location on the leeward side of the Western Ghats. The major rivers therefore derive much of their discharge from the high rainfall source region (up to 6,000 mm), and bring water to the semi-arid zone downstream. The landscape is dominated by flat denudational surfaces at 1,200, 1,000, 800 and 700 meters above sea level (Kale and Rajaguru, 1988) of pre-Quaternary age developed on 60 myr old Deccan Trap basalt. The rivers lack well-developed floodplains and alluvium is confined to à narrow belt less than 2 km wide. The non-alluvial part of the landscape is basalt bedrock, covered with varying thicknesses of weathered bedrock, locally called ‘murrum’ on which a soil has developed. This weathered mantle developed during the Tertiary, when the climate was comparatively humid. The thickness of the alluvium is generally less than 20 m. This alluvium includes several fills ranging in age from the Early Middle Pleistocene to the Late Holocene. The Holocene deposits are non-calcareous silts and sand and generally form an alluvial terrace 5–6 m high inset into an older Pleistocene alluvial fill terrace 10 to 15 m high. The Pleistocene alluvium is calcareous and dominated by sandy silt with lenses of gravels and fissured clays. Colluvium covers some footslopes.