Seismic characteristics, distribution and origin of shallow gas on the continental shelf offshore the Pearl River Estuary, northern South China Sea

Li, Jian, Li, Wei, Alves, Tiago M. ORCID: https://orcid.org/0000-0002-2765-3760, Feng, Yingci, Sun, Jie, Yao, Yantao, Huang, Jiaxian, Wang, Pin, Tang, Qinqin and Zhan, Wenhuan 2026. Seismic characteristics, distribution and origin of shallow gas on the continental shelf offshore the Pearl River Estuary, northern South China Sea. Marine Geology 502 , 107885. 10.1016/j.margeo.2026.107885

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Abstract

Shallow gas accumulations on continental shelves are crucial for assessing offshore geohazards, understanding marine methane cycling, and evaluating potential hydrocarbon targets. The study area, situated on the Pearl River shelf south of Macau and Hong Kong, is part of a major sedimentary basin in the northern South China Sea, where high sediment input, well-developed paleochannels, and active faults favor shallow gas generation and accumulation. Here, we use multi-frequency two-dimensional seismic data to investigate the seismic characteristics, distribution, origins, and geohazard potential of shallow gas, and establish a migration-accumulation framework. Our results reveal extensive acoustic anomalies offshore the Pearl River Estuary, including acoustic blanking, turbidity, brightened reflectors, and gas pipes. These features suggest widespread shallow gas primarily concentrated southwest of Da Wanshan Island and south of Jiapeng Island, with fronts at 6–40 m below the seafloor. Integrated analysis interprets this shallow gas as a mixed system with contributions from both shallow biogenic and deeper-sourced gases, controlled by depositional conditions and tectonic setting. Biogenic gas most likely derives from organic-rich Late Pleistocene paleochannel fills and Holocene muddy deposits, where rapid burial favors methanogenesis, though other intervals may also contribute. Deeper-sourced gas may originate from Paleogene source rocks at depth, potentially migrating upward through basement-rooted fault zones and gas pipes, though its exact origin cannot be determined from seismic data alone. These findings are critical for assessing and mitigating geohazards in this region, where coastal infrastructure is expanding.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences Schools > Physical, Chemical & Environmental Sciences
Publisher:	Elsevier
ISSN:	0025-3227
Date of First Compliant Deposit:	1 September 2026
Date of Acceptance:	21 August 2026
Last Modified:	01 Sep 2026 10:01
URI:	https://orca.cardiff.ac.uk/id/eprint/189260

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