Subsurface architecture of the Currituck submarine landslide complex: New insights from high-resolution MCS data

Abstract:

The Currituck submarine landslide complex located offshore North Carolina is one of the most pronounced geomorphic features of the US Mid-Atlantic Margin, evacuating and redepositing sediment over an area greater than 6500 km² along continental slope and upper rise. Despite its geomorphic significance, the factors that preconditioned the Currituck slope for failure remain poorly understood. We present an integrated analysis of new high-resolution multichannel seismic (MCS) reflection profiles acquired by the USGS, multibeam bathymetry data, and 1980s vintage industry MCS profiles. The Currituck slope appears to be made up of multiple failure events. Bathymetry data show evidence for multiple surface scarps, while the MCS data suggest there are additional buried scarps within the Pleistocene section. A ~500-m-thick section of relatively intact strata is observed across a 10 x 18 km swath of the lower slope and adjacent to the primary slide evacuation zone. Within this section, chaotic mass transport deposits are sandwiched between parallel reflectors, suggesting older landslides occurred along the upper slope prior to the most recent episode of slope failure. Plio-Pleistocene strata imaged below the main Currituck slide surface display seaward divergence and little to no evidence for buried submarine canyons, suggesting that the Currituck slope was progradational prior to failure. In contrast, the slope to the north and south of Currituck is heavily canyonized and Plio-Pleistocene depocenters are concentrated on the upper rise, suggesting these regions were dominated by sediment bypass and erosion. 3-D mapping of allostratigraphic surfaces imaged in industry MCS profiles reveal significant spatial variation in the antecedent margin morphology that may have set the stage for the accumulation of unstable Plio-Pleistocene depocenters. Upper Miocene strata to the north and south of Currituck show an angular shelf-edge and steep upper slope, whereas the Currituck region displays a rounded and gentle shelf-edge/upper slope. The gentler slope profile may have allowed for preferential sediment accumulation.