Link between climate and catchment erosion in the Himalaya during the late Quaternary

Abstract

Few studies using geochemistry of sediments from plains and delta of the Himalayan river system have reported contrasting results on the shift in erosion of different lithotectonic units, across the strike of Himalayan orogen, in response to changes in the intensity of Indian summer monsoon (ISM) and glacial cover during the late Quaternary. Here we present records of the 143Nd/144Nd (εNd) and 87Sr/86Sr ratios and δ13C of sediment organic matter (δ13CSOM) in bulk sediment samples from two ~45 m long alluvial cores, collected from a paleo-Sutlej channel (in Sirhind, Punjab) at an upstream connection of a large river (Ghaggar-Hakra) with present-day Sutlej River in NW India. The isotopic variations are compared with the available proxy records that document changes in the ISM and Himalayan glacial extent. Significant covariation in down-core profiles of εNd (−14.1 to −22.2) and 87Sr/86Sr (0.72251–0.79456) reveals changing contributions of sediment derived from the Higher and Lesser Himalaya end-member sources in the catchment. Higher εNd (and lower 87Sr/86Sr) during early marine isotope stage (MIS) 1 and late MIS3 reflects increased contribution from the Higher Himalaya as a result of receding glacial cover as well as intense ISM that penetrates into the interior of the Higher Himalaya during warm periods. The δ13CSOM varies from −28.5‰ to −21.3‰ and shows a 5–7‰ increase from colder MIS2 to warmer early MIS1, implying an increase in C4 plant abundance during the same period in response to intensification of the ISM in the post last glacial maximum period. These variations in sediment provenance and vegetation pattern thus highlight the pronounced influence of climate on distribution of erosion and vegetation types in the NW Himalaya.