Seismic stratigraphic framework and Fluid migration patterns of the rifted continental margin offshore North Carolina

Abstract

Seismic reflection data is useful for unravelling the subsurface fluid migration patterns and can help to understand the plumbing system. The study presents the seismic stratigraphic framework and fluid migration features of a 12000 km stretch of the U.S. Atlantic margin at water depths of 150 m (shelf break) to 5000 m (abyssal zone). The high‐resolution multichannel seismic reflection data reveal the presence of a gas hydrate system, such as a bottom simulating reflector (BSR), gas‐charged sediments, and fluid pathways on the continental slope. The new seismic data helps to extend the previously reported gas hydrate BSR into deeper waters. The BSR derived geothermal gradient shows lateral variation, such as isolated high anomalies related to salt diapirs on the upper continental slope. Salt pierced sedimentary strata. The gas hydrate stability field becomes thinner above the conical salt diapir. The seismic analysis and numerical modelling suggest that the diapirs are due to salt and not due to the mobilization of shale or other sedimentary rocks. At the continental rise, a silica diagenetic reflector is identified as an opal-A to opal-CT conversion boundary. Silica diagenesis releases water and builds high pore fluid pressure. Such pressure facilitates vertical fluid migration that transports diagenetic fluids to the seafloor creating pockmarks. On the upper continental slope, a buried mass transport complex occurs. Rapid sediment delivery from the outer shelf and shelf-break caused by low sea-level during Miocene could have triggered a submarine slide or slump.