Silicate weathering linked with global climate change along the Mid-Pleistocene transition: A record from the Himalayan foreland Basin, India

Abstract

Tectonic uplift and climate change play a pivotal role in controlling silicate weathering in the source region. Being adjacent to the hinterland, the sediments of the Himalayan foreland basin (HFB) hold an excellent archive to elucidate weathering link with climate and uplift. In this study, we present geochemical records of major, trace and rare earth elements, clay mineral compositions as well as the environmental magnetic and stable carbon isotope composition (δ13C) of siliciclastic sediments of the HFB over the past 2.0 Ma. These records have been used to link silicate weathering with global climate change along the Mid-Pleistocene Transition (MPT) period. The source rock compositions are characterized by selected elemental ratios, i.e., Cr/Th, Th/Sc, Th/Co and La/Sc as well as other geochemical proxies such as Al2O3/TiO2 and TiO2/Zr, suggesting a felsic source rock composition. The enriched LREE pattern of Chondrite-normalised REE with a negative Europium anomaly also attributes to felsic source rock composition. All these inferences suggest that most of the studied sediments were derived from mixed sources of the Higher Himalayan rocks and the Lesser Himalayan crystalline regions. A declining trend in kaolinite/(illite + chlorite) ratios, decreasing values of geochemical weathering indices (such as Rb/Sr and CIA), a decrease in magnetic susceptibility and gradual depleted value of δ13C indicate a decrease in chemical weathering of the siliciclastic rocks in the source region, which is most probably associated with the global climate change from warm-humid to cold-dry condition along the MPT. This suggests that variation in silicate weathering in the Himalayan region are mainly controlled by global climate and monsoon conditions.