Late Holocene Climatic Record in the Northeastern Part of the Deccan Trap Region, Maharashtra, India: Episodic Intensification and Weakening of the Monsoon

Abstract

A high-resolution paleoclimatic reconstruction from the Tirna River basin in the Deccan Volcanic Province (DVP) of western India, covering about 2022 - 1596 calibrated years BP, is presented in this paper. The study combines magnetic susceptibility (χ) and elemental geochemistry ratios (Fe/Al, Ti/Al, K/Na, K/Al, Ca/Al, Mn/Al, and Mg/Al) to infer weathering regimes, detrital input patterns, and sedimentary processes controlled by climate. An initial wet and erosive period (~1596–1707 cal yr. BP) characterised by high Fe/Al, Ti/Al, and χ values, reflects intense monsoon-driven detrital input, and represents one of the several climatic sequences captured in the record. A transitional period with decreasing magnetic susceptibility and Fe/Al ratios (~1722–1785 cal yr. BP) follows, indicating reduced runoff and possible monsoon variability. When chemical weathering markers peak between 1840 and 1872 cal yr. BP, it suggests a humid period with more intensified pedogenesis. Declining χ and subsequent increases in Ca/Al and Mg/Al (~1903–1974 cal yr. BP) indicate reduced erosion and a shift towards warmer and more stable conditions. A shift to cooler, drier, and more stable environmental conditions is indicated by the rapid fall in weathering proxies and χ during the most recent phase (~1993–2022 cal yr. BP). These climate changes are consistent with known regional and global paleoclimatic events, including the beginning of the Dark Ages Cold Period, the end of the Roman Warm Period, and the well-documented monsoon weakening event around 2.0 ka BP. The results demonstrate sensitivity of the DVP landscape to variations in the Indian Summer Monsoon. Overall, this study highlights the value of multi-proxy sediment records for reconstructing past monsoon variability and enhances our understanding of Late Holocene hydroclimatic dynamics in peninsular India.