Sediment dispersal patterns in part of a deformed Mesozoic back-arc basin on South Georgia, South Atlantic
The Cumberland Bay Formation is a deformed Late Jurassic-Early Cretaceous volcaniclastic turbidite formation several kilometers thick. It has been interpreted as the fill of a back-arc basin which was active on the southwest margin of Gondwana. Sole marks, oriented fossil wood, and small channels identified the paleocurrent directions, and slump folds indicated the paleoslope. Sole marks show a southeast-northwest trend parallel to the axis of the island; unambiguous current-direction indicators show that the "axial" dispersal was towards the northwest. Paleocurrent distributions are bimodal, there is a "lateral" mode at a high angle to the axial-mode in most areas. Beds bearing lateral-mode sole marks are thicker than those with only axial-mode sole marks. Fossil-wood and channel orientations indicate a major axial dispersal pattern. Slump folds show that over much of the outcrop, paleoslopes were roughly northerly. The overall paleocurrent pattern defines a curve concave to the southwest which parallels the shape of the island; this pattern may reflect original basin shape