A prominent volcaniclastic channel sandstone deposited by a landward-flowing sediment gravity flow is described from the Maastrichtian of Snow Hill Island in the northern Larsen Basin. The characteristics of this petrographically distinct event deposit appear to indicate a volcanic source to the east of Snow Hill Island, well away from the magmatic arc landmass which sourced the bulk of the Larsen Basin fill, suggesting minor off-axis intrabasinal volcanism in Maastrichtian to Paleogene times.