Turbidity currents and submarine slumps, and the 1929 Grand Banks [Newfoundland] earthquake

Abstract

Following the 1929 Grand Banks earthquake which shook the continental slope south of Newfoundland, all the submarine telegraph cables lying downslope (south) of the epicentral area were broken in sequence from north to south. All previously published explanations of these breaks are considered and rejected because they do not adequately explain this sequence. A new explanatio is offered according to which each successive cable was broken by a turbidity current originating as a slump on the continental slope in the epicentral area and traveling downward across the continental slope, continental rise, and ocean basin floor and continuing far out on the abyssal plain well over 450 miles from the continental shelf. We may consider these events as a full scale experiment in erosion, transportation and deposition of marine sediments by a turbidity current in which the submarine telegraph cables served to measure its progress, give evidence of its force, and by their subsequent burial indicate some of the areas of deposition. On the bsis of widespread evidence for exposure of Tertiary and older sediments on steep submarine slopes, for numerous coarse graded deposits interbedded with deep sea clays in flat-bottomed ocean basins hundreds of miles from land, we conclude that large scale work by slump-generated turbidity currents is a fundamental process in submarine geology.