Possible sub-glacial volcanism in western Ross Sea

Abstract

Preliminary Results from the Korean JangBogo Expedition to Terra Nova Bay in February 2011 extended the extent of the field of unusual flat topped seafloor mounds located west of Franklin Island. Detailed multibeam bathymetry data were recorded using an EM122 swath echosounder with 455 beams, and extends the mound field (OGS Explora Mounds) about 6 km further east, confirming that two features imaged on single channel bathymetry are of the same character. An additional six mounds have been delineated, with some appearing to be coalesced features. The total field covers an area about 20 km square and lies at a depth of about 500 m. The north-western margin trends NNE, drops sharply away into water depths of about 850 m and may be fault controlled. The mounds have a northerly trend and tend to be circular in the east and linear in the west. The largest mound is about 4 km across and 100 m high. The mounds have a steepest slope to the south- east, and shallowest slope to the northwest. Three similar features were delineated about 25 km to the south of Franklin Island at a depth of 650 m, and one 5 km east of Franklin Island at a depth of about 400 m. Seismic, gravity and magnetic data indicate a low density and magnetisation body overlying a largely non-disrupted sedimentary section. The proximity of the main mound field to inferred subsurface gas hydrates and associated mud volcanoes and