Quaternary Alluvial Stratigraphy and Palaeoclimatic Reconstruction in the Damodar River Basin of West Bengal

Abstract

The Quaternary (starting from ~2.6 million years ago) climate changes have progressively triggered abrupt changes in the fluvial system and the resultant signatures are captured in the fluvial archives which are used as climate proxies to detect the palaeoclimate. In this chapter, the stratigraphic exposures, sediment characteristics, and dating information have been utilised to reconstruct the palaeoclimate in the alluvial valley of the Damodar River, West Bengal. This study has identified four distinct Quaternary geological units of the lower Damodar River Basin (DRB)—Lalgarh, Sijua, Chuchura, and Hooghly—morphostratigraphic units which belong to the northwestern part of the Bengal Basin. Analysing the architectures of different lithofacies, approximately six to seven climate changes (semi-arid to warm–humid) occurred in the study area from ~14 and 6 kiloannum (ka). Alongside these climate changes (from Late Pleistocene to Late Holocene) were directly linked the variability of the southwest monsoon (SWM) in two forms: (1) the semi-arid climate (i.e. the onset of low-strength SWM, associated with caliches, pond, and backswamp deposits of waning low-energy floods), and (2) the warm–humid climate (i.e., the onset of high-strength SWM, bearing imprints of sandy bedforms, valley fills, slack water deposits (SWD) of extreme floods, and ferruginous nodules).