Speaker
Summary
The study examines sedimentary organic matter (SOM) from the Karankadu mangrove (Tamil Nadu coast) using stable isotope analyses to reconstruct anoxia and ecosystem processes over the last ~7800 cal yr BP. Depth-wise variability in δ¹³CTOC, and δ³⁴STS, along with TOC/TS ratios, revealed distinct redox regimes. Shallow sediments exhibited oxic signatures (δ³⁴STS –8‰ to +6‰; TOC/TS: 8.2–3.1), whereas deeper layers showed strongly negative δ³⁴S values (–26‰ to –10‰) and lower TOC/TS ratios (2.4–0.9), indicating suboxic–anoxic conditions. Microscopic evidence of pyrite and greigite supported these isotopic shifts. Additionally, δ¹³CTOC values, integrated with grain-size and pollen data, provided insights into paleoclimate variability and ecosystem alteration with silty clay fractions enriched in ¹³C (more positive δ¹³C). Overall, the isotopic dataset demonstrates how shifts in carbon and Sulphur isotopes can trace coastal anoxia, SOM alteration, and long-term climate-driven ecosystem changes.
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