Relations between mud volcanoes, thrust deformation, slope sedimentation, and gas hydrate, offshore north Panama

Abstract

SeaMARC II swath-mapping and migrated seismic reflection data show a high concentration of mud volcanoes in the primary sediment depocentre along the lower slope of a thrust belt, offshore north Panama. The mud volcanoes are 0.4–2.0 km wide, <100 m high, and have pierced the crests of dominantly seaward-verging, thrust-bounded anticlines, landward of the frontal fold. The depocentre marks the confluence of the two major sediment transport systems along the northern Panama margin. Few mud volcanoes are located outside of the depocentre, except in a mid-slope region slightly east of the depocentre and near a zone of probable strike-slip deformation. Sonar reflectivity (backscattering), sediment cores, and seismic stratigraphic relations indicate that the depocentre contains thick sequences of basinal turbidites which are ponded between the anticlinal ridges. The ridges are composed of the deformed turbidites of the Colombian basin and exhibit a strong bottom-simulating reflector (BSR), apparently associated with a gas hydrate layer. Based on the concentration of mud volcanoes along the crests of the anticlinal ridges in the depocentre and the structural position of the BSR, we suggest that folding along the deformation front, sediment ponding leading to differential loading, methane migration and accumulation in the anticlines, and gas hydrate formation are important factors in the development of mud volcanoes in this region.