Pockmarks, Mud Volcanoes and Hydrocarbon Seeps in the Northern Gulf of Mexico: Trends and Controls on Widespread Fluid and Gas Venting

Abstract

The release of hydrocarbons, pore water and fluidized sediments impacts seafloor morphology, marine biogeochemical cycling and subsurface hydrocarbon resources. However, the basin-scale occurrence and controls on fluid seepage remain poorly constrained. Herein, we combine datasets that used bathymetry to map pockmarks and mud volcanoes with water column acoustic data that identified gas seeps in the northern Gulf of Mexico. Then, we map hundreds of new pockmarks and mud volcanoes using newly released industry seismic data. We observe strong water depth-dependent patterns: pockmarks cluster at 330–605 m, while mud volcanoes are most common at less than 1000 m. The downslope decline in the number of pockmarks and mud volcanoes corresponds to the basinward thickening of the gas hydrate stability zone, as well as thicker and broader underlying salt masses, indicating potential controls on fluid seepage. Furthermore, water column gas plumes, pockmarks, and mud volcanoes cluster above salt-cored ridges and associated fault networks, demonstrating that seepage is non-random and controlled by localized geological structures. By scaling the abundance of active seeps against flux rates from representative vents, we make a first-order estimate of total hydrocarbon flux ranging between ~5.6–46 × 10⁷ tons year⁻¹ for the northern Gulf of Mexico. Our analysis further reveals that despite these estimates, a multitude of seeps remain undocumented across the region, indicating that the true extent of hydrocarbon release is most likely greater than currently recognized. Ultimately, these findings are vital for making informed decisions for subsurface hydrocarbon resource exploration, flux estimation, marine habitat assessment, CO₂ sequestration and geohazard assessment in marine sedimentary basins.