McHugh et al. (2002) studied mass-transport deposits sampled at Leg 150 Sites 902-906. These consist predominantly of muddy slumps and debris flows and, to a lesser extent, sandy mass flows. In the Pleistocene and upper Miocene, mass-wasting deposits are thought to rest preferentially on sequence boundaries of the middle to upper paleocontinental slope. In older Oligocene and Miocene strata, they are inferred to overlie sequence boundaries mainly on the mid- to lower slope.
Dugan and Flemings (2000) recognized that Pleistocene sediments of the continental slope (Site 1073) are undercompacted (40%-65% porosity) to depths as great as 640 mbsf. They interpreted these data to imply that fluid pressures reach 95% of the lithostatic stress. Such excess pressures may account for slope failure during both interglacial and glacial intervals (McHugh and Olson, 2002) and cold seeps.
Dugan and Flemings (2002) used a hydrodynamic analysis of Site 1073 porosities to demonstrate the interplay of sedimentation and fluid migration on the distribution, timing, and size of sedimentary failures. They hypothesized that portions of the New Jersey slope were unstable at ~500 ka, owing to rapid sediment loading during a Pleistocene lowstand combined with flow-focusing in underlying permeable Miocene strata. Their modeling suggests that stability on this slope has increased since 300 ka.