Late Holocene geochemical and environmental changes inferred from a multiproxy investigation in sediments from Kondagai Lake Tamil Nadu, India

Climatic crises have been increasing rapidly since the late Holocene worldwide. Strategic planning needs multi-proxy records to understand the rate of ecosystem and climatic perturbations for generating mitigation maps. We present multiproxy records with isotopic composition (δ 13 C TOC , δ 15 N Bulk ), total organic carbon (TOC%), total nitrogen (TN%), total organic carbon to total nitrogen (C/N) ratio, palynofacies and grain size analysis of an AMS radiocarbon-dated Holocene sediment profile recovered from Kondagai lake (KLD), Tamil Nadu, India. Data sets are used to interpret the organic matter source and variation in the sediment deposition pattern. Enriched values of δ 13 C TOC and finer grain size between ~4.5 and 3.7 k cal yrs BP. represent the sources of organic matter were mostly aquatic plankton and C4-type vegetation (Poaceae), attested with low terrestrial inputs, which supports the fungal production, suggesting the shallower lake levels and drier period (parallel with the 4.2 ka event), indicating the weaker phase of the Indian monsoon. From ~3.7 to 2.5 k cal yrs BP, the lake had a high water level, marked by increased terrestrial flux, with higher sand % and depleted δ 13 C TOC values. From ~2.5 to 0.9 k cal yr BP, Lake witnessed the continuity of a warm episode, represented by the depleted values of δ 13 C TOC and coarser grain fraction at the episodic scale suggest the lake level fluctuation with marked flooding events. Higher values of δ 15 N Bulk , and C/N ratio suggest the altered element cycling in the latest phase of KLD Lake, coincides with Roman warm period (RWP). The findings enhance our understanding of organic matter sources, marking flooding events and lake level changes in accordance with monsoon variabilities, land use alteration by the combination of natural and anthropogenic actions. This investigation also highlighted the integrated effects of Indian monsoon and El Niño Southern Oscillation (ENSO) variabilities over the last 4.5 k cal yrs BP.