| Abstract Submission No. | ABS-2.4-0095 |
| Title of Abstract | Role of Geological Processes in Controlling Methane Seepage along the Indian Continental Margin |
| Authors | Aditya Peketi*, A. Zatale, A. Mazumdar, P. Dewangan, S. Ramesh, Aniruddha Mitra, G. Sriram, Swati Verma, Subhashree Mishra, V. Mahale |
| Organisation | CSIR- National Institute of Oceanography |
| Address | NIO colony, Dona Paula North goa, GOA, India Pincode: 403004 E-mail: adipeketi@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Methane seepages across Indian offshore basins are critical geobiological and geochemical phenomena influencing benthic ecosystems and regional carbon cycling. Investigations in the Bay of Bengal and Andaman Sea reveal dissolved methane concentrations up to ~1500 nmol/L, far above background seawater, confirming widespread active seepage. Geological controls, however, vary significantly between basins. In the Krishna¿Godavari basin, shallow-water seepages (~200 m; ~172 nmol/L) are linked to recent submarine landslides, whereas deeper-water seepages (~700¿1800 m) are associated with compressive structures formed by shale tectonism, which provide favourable conditions for gas hydrate accumulation and cold seep activity. Twenty-two seepage sites have been identified in the deep basin; while a fully developed cold seep ecosystem has been documented at one site, the remaining 21 require detailed ecological assessment. In contrast, shallow-water seepages, despite active methane release, show no evidence of ecosystem development. The Mannar basin hosts gas-bearing sediments underlain by a well-developed bottom-simulating reflector (BSR), with vertical chimneys and fractures acting as conduits for deep-seated gas migration, sustaining seepage activity (~48 nmol/L). In the Andaman Sea, elevated methane concentrations at a submarine seamount (SM-13) may reflect hydrothermal influence, though this remains unconfirmed. The recovery of Bathymodiolus mussels indicates the presence of a potential seep ecosystem at this site, warranting further investigation. Nearby mounds display seepage controlled by compressional tectonics associated with subduction, where BSRs and fault systems provide structural pathways for fluid migration. Collectively, these seepages demonstrate that methane release in the northern Indian Ocean is governed by diverse geological processes, including landslides, shale tectonism, faulting, hydrothermal activity, and subduction. Yet, the extent to which these contrasting geological controls regulate the intensity, persistence, and ecological consequences of seepage remains poorly understood. Resolving these uncertainties is essential for constraining methane cycling and evaluating its role in global carbon dynamics. |
| Keywords | Methane seepage, Indian continental margin, Krishna¿Godavari Basin, Mannar Basin, Andaman Sea, Gas hydrate, Shale tectonism, Submarine landslides, Hydrothermal activity |