Chemical weathering variability during last glacial-interglacial cycle: A geochemical study of Bay of Bengal sediments

Abstract

Continental weathering and sediment transport are strongly influenced by climatic fluctuations. Studies from the Bay of Bengal, however, provide diverging evidence for the weathering and climate coupling. In this study, we present high-resolution major oxides concentration data for a sediment core VM29-19PC (water depth: 3182 m), retrieved from the western Bay of Bengal, to reconstruct variations in chemical weathering intensity and sediment provenance over the past ~35,000 years. The chronology of this core was established in an earlier study using AMS radiocarbon dating of planktic foraminifera, confirming a continuous sedimentary archive spanning the last glacial–interglacial cycle. Geochemical indices, particularly an increase in the Chemical Index of Alteration (CIA) and a concurrent decline in K/Al ratios, suggest progressive intensification of chemical weathering beginning around 25 ka, likely driven by climatic amelioration. These variations are synchronous with climatic transitions, and point to affect of enhanced monsoonal activity on continental weathering via increased continental runoff. The observed trends reflect a dynamic interplay between monsoon-driven hydrological shifts and regional erosion patterns, highlighting the sensitivity of weathering regimes to long-term climate variability in South Asia.