Anomolous seismic horizons which (1) are strongly reflective, i.e. have a high impedence contrast; (2)cut across bedding planes of sediments;(3)are subparallel with the sea floor; and (4)increase their sub-bottom depth with increasing depth of sea floor (and thus with decreasing temperature of bottom water) are tentavely identifed as the base of a gas hydrate layer. The anamalous reflections occur below waters 1000-2500m deep, and along 500km of the continental slope. Some 10–20,000 sq km appear to be underlain by gas hydrates. The hydrate layer is often associated with structural anomalies(anticlines, tilted faultblocks). These would allow gas to migrate up-dip into pressure and temperature conditions suitable for hydrate formation. Since the hydrate-cemented layer itself acts as a barrier to gas migration, free gas will be trapped and accumulated in the sediments beneath it. It is concluded that huge amounts of hydrocarbon gas, both free gas and solid hydrate, have accumulated in this continental margin. On land, gas and oil generation is widespread, mainly originating from overpressured, Lower Teritiary to Upper Cretaceous shales. From seismic evidence the same formations appear to extend under the shelf and continental slope. The extensive occurence of gas hydrates would confirm that organicrich, terrigenous sediments have extensively been deposited in these areas.