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Abstract

A large submarine-slide deposit from the western Scotian Slope off eastern Canada was imaged on a 3D seismic reflection dataset in the Barrington exploration block. The mass-transport deposit (MTD) forms a tongue-shaped body that is 25 km long and 8 km wide, with a run-out distance from the headscarp of 41.5 km and a total volume of 12.5 km3. In profile, it consists of a chaotic seismic facies. This facies forms a highly rugose top surface morphology, suggesting that the flow consisted of an abundance of intact angular blocks. Its base reveals evidence of erosion typical of submarine MTDs, with linear downslope-trending gouges and excavation of a pit 50-m-deep. The source area and headscarp of the Barrington MTD are somewhat obscured by postdepositional erosion. Additionally, high-resolution seismic profiles show that the deposit is draped by approximately 30 m of late Pleistocene and Holocene sediment, providing an age estimate of 30 ka for the failure. Despite this drape, the modern seafloor above the MTD still has a highly rugose morphology, echoing the top surface of the deposit.

Seismic profile data show a series of stacked MTDs underlying the Barrington MTD, suggesting that mass-failure recurrence is common on geologic time scales. Although it is difficult to attribute mass-failure triggering mechanisms, high sedimentation rates due to proximal shelf glaciers and intense erosion causing oversteepening, and likely established preconditions for instability. Local seismicity, possibly a result of glacial rebound, is the most probable initiating factor.

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