High resolution imaging of the north (NPTB) and south Panama thrust belts, using the SeaMARC II seafloor mapping system and digital seismic reflection profiling, provides an excellent data base with which to determine the kinematics of oroclinal deformation of Panama. Remarkable continuity of structural orientations over 300 km along the NPTB argues for widespread uniformity in direction of thrusting between Panama and the Caribbean plate. Westward decrease in the width and height of the accretionary wedge indicates a westward decrease in the total amount of convergence. Two major cross faults cut the wedge in its eastern part, forming two minor blocks with different relative motions with respect to the Caribbean. Frontal thrust orientations change across these faults. Major faults have been proposed to cut the isthmus of Panama, but simple cross‐isthmus faulting alone cannot explain the orientations of the major thrusts of the NPTB. Bending of a flexible beam can explain much of the observed structure, both directions and rates, though the scale of the orocline precludes considering this as an elastic phenomenon. Plastic deformation of Panama may be a useful mechanical explanation, at least for eastern Panama, but consideration of plastic slip lines must include the northern Andes as well. Changing from more rigid, blocklike offsets on faults in western Panama to a continuum of strain in eastern Panama may be the best explanation for observations at present.

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.

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