Seabed fluid expulsion along the upper slope and outer shelf of the U. S. Atlantic continental margin

Identifying the spatial distribution of seabed fluid expulsion features is crucial for understanding the substrate plumbing system of any continental margin. A 1100km stretch of the U.S. Atlantic margin contains more than 5000 pockmarks at water depths of 120m (shelf edge) to 700m (upper slope), mostly updip of the contemporary gas hydrate stability zone (GHSZ). Advanced attribute analyses of high-resolution multichannel seismic reflection data reveal gas-charged sediment and probable fluid chimneys beneath pockmark fields. A series of enhanced reflectors, inferred to represent hydrate-bearing sediments, occur within the GHSZ. Differential sediment loading at the shelf edge and warming-induced gas hydrate dissociation along the upper slope are the proposed mechanisms that led to transient changes in substrate pore fluid overpressure, vertical fluid/gas migration, and pockmark formation.