A geological and geophysical study of the 1929 Grand Banks slide

Abstract

The St. Pierre Slope off the Grand Banks of Newfoundland is the site of a large submarine failure complex that was the result of the 1929 Grand Banks earthquake. A 2000 km 2 area has been investigated in detail using seismic reflection, sidescan sonar and core data. Failure development and evolution is strongly influenced by local changes in gradient on the slope. Documented modes of failure are mass flows, slumps, and isolated occurrences of glides and creep. The total volume of sediment involved in initial failure is estimated at 93 km 3 : 47 km 3 as MTDs on the slope and 46 km 3 that evacuated, likely contributing to the 1929 turbidity current. The total volume of the turbidite is conservatively estimated at 175 km 3 , suggesting that at least 222 km 3 (47 km 3 + 175 km 3 ) of sediment was eroded and displaced during the 1929 event.