Abstract Here, we present organic geochemical evidence of past methane‐seepage events in a sediment core retrieved from a recently discovered methane cold‐seep site off Mannar Basin, east coast of India. The significant negative C‐isotope excursion of organic matter (δ13CTOC) in the seep core compared to a reference non‐seep core suggests a substantial contribution of methanotroph‐derived organic carbon to the seep sediment organic pool. Based on archeal biomarker data, and the presence of relict chemosymbiont‐bearing Calyptogena shells, we propose a protracted period of episodic methane seepage events spanning across the Marine Isotope Stage‐3 to mid‐Holocene, with a declining seepage intensity toward the Holocene. The episodic depletion in δ13CTOC reveals four intermittent high methane flux events. Our study highlights that δ13CTOC can be used as an important proxy for reconstructing the dynamic evolution of past methane‐seep activities, particularly when integrated with lipid biomarkers and their isotopic fingerprints.
Observations from the Little Bunker
Last updated: October 16, 2025 02:57 AM
Atmospheric CO₂
424.4 ppm
+18.2
ppm/year
Atmospheric CH₄
1933.54 ppb
+12.29
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
World Population
8.1 billion
+67
million/year