Tectonics and climate controlled sedimentary provenance in the Teesta basin since mid-Holocene

Abstract

Erosion of the Himalaya Mountain and subsequent deposition of sediments in the flood plains, and distal fans are primarily regulated by tectonics, climates, lithology, and relief of the region. These eroded sediments preserve their chemical and isotopic compositions in their depositional archive, which can be used to trace the erosion processes and assess the relative role of controlling factors and their spatio-temporal variations. The present study has analysed the ⁸⁷Sr/⁸⁶Sr and Ԑ_Nd of in silicate phase of sediment recovered from a ~ 40 m long sedimentary core representing ~8 ky of sediment accumulation in the Teesta River mega fan. The lithostratigraphy of the core indicates rapid aggradational nature of the Teesta mega fan. The ⁸⁷Sr/⁸⁶Sr and Ԑ_Nd display large variability with depth, which ranges from 0.75700 to 0.89294 and − 15.1 to −25.0, respectively. The observed ⁸⁷Sr/⁸⁶Sr and Ԑ_Nd values in the core sediments have been interpreted in terms of differential sediment contribution from the Higher and the Lesser Himalayan lithology. The ⁸⁷Sr/⁸⁶Sr and Ԑ_Nd isotope profiles and estimated fractional sediment contributions identify the Lesser Himalaya as the major sediment contributor to the Teesta basin since the mid-Holocene, unlike the other Himalayan River basins, dominated by sediments from the Higher Himalaya after the Last Glacial Maximum. The rapid exhumation and erosion of the tectonically active Rangeet window with the focused precipitation and presence of rock types vulnerable to weathering in the Lesser Himalaya of the basin appear to be the major factors resulting in the sedimentary budget of the Teesta River basin over at least last 8 ky. Our assessment suggests that tectonic activity and climate have a competitive effect on the observed sedimentary budget, with an additional role of lithology. The study infers a major control of active tectonics, precipitation, and lithology on the sedimentary budget of the Himalayan River basins.