Gas hydrates and active mud volcanism on the South Shetland continental margin, Antarctic Peninsula

Abstract During the Antarctic summer of 2003­2004, new geophysical data were acquired from aboard the R/V OGS Explora in the BSR-rich area discovered in 1996­1997 a l o n g t h e S o u t h S h e t l a n d c o n t i n e n t a l m a rg i n o ff t h e Antarctic Peninsula. The objective of the research program, su pp orte d b y th e I talia n Na tional Antarctic Program (PNRA), was to verify the existence of a potential gas hydrate reservoir and to reconstruct the tectonic setting of t h e m a rg i n , w h i c h p r o b a b l y c o n t r o l s t h e e x t e n t a n d character of the diffused and discontinuous bottom simu- lating reflections. The new dataset, i.e. multibeam bathym- etry, seismic profiles (airgun and chirp), and two gravity cores analysed by computer-aided tomography as well as for gas composition and content, clearly shows active mud volcanism sustained by hydrocarbon venting in the region: several vents, located mainly close to mud volcanoes, were imaged during the cruise and their occurrence identified in the sediment samples. Mud volcanoes, vents and recent slides border the gas hydrate reservoir discovered in 1996­ 1997. The cores are composed of stiff silty mud. In core GC01, collected in the proximity of a mud volcano ridge, the following gases were identified (maximum contents in brackets): methane (46 g/kg), pentane (45), ethane (35),