The Barrington Submarine Landslide: Southwestern Scotian Slope

David C. Mosher, D. Calvin Campbell, and Laurie Tremblay
Geological Survey of Canada Atlantic, Dartmouth, NS

The present day continental margin morphology offshore of Nova Scotia formed during the Cenozoic. Canyons and gullies dissected the slope during late Tertiary major sea-level lowstands. Shelf-crossing glaciations over the past 0.5 Ma played a dominant role in sediment delivery to the continental slopes. Mass transport processes removed variable amounts of the Cenozoic succession but within the remaining sequence are mass transport deposits (MTDs) identified at scales ranging from centimeters to hundreds of meters, forming a significant sedimentation style on the slope and rise. It is the intent of this paper to produce a case-study of a particularly well-preserved MTD on the southwestern Scotian margin, visualized with 3D seismic technology.

The Barrington MTD is considered to be mid to late Wisconsinan in age. It is the topmost of a sequence of at least four MTDs apparent in section. It comprises an area of over 200 km² and has an average thickness of about 90 ms (ca. 80 m), thus incorporating about 16 km³ of sediment. The Barrington MTD demonstrates a blocky morphology on its top and downslope linear scours at its base, implying a flow origin. In addition, there are large (50 m-deep) “pluck-out” holes beneath it, indicating an erosional base. Geotechnical investigations show that Holocene to Late Pleistocene sediment on the slope is statically stable and significant pore pressures or ground accelerations are required to initiate failure. This fact draws questions about triggering mechanisms for such large debris flows in a passive continental margin setting.