Passive continental margins have been shown to subside with a 50-m.y. exponentially decaying rate which cannot be explained by isostatic compensation for sediment loading. This suggests that the subsidence is dominated by geodynamic processes similar to those in the deep ocean. Two simple geologic models for continental breakup are developed: (1) attenuation of continental lithosphere and (2) intrusion of mantle diapirs.

These models for rifting give a direct relation between subsidence of passive margins and their surface heat flow through time. On this basis we develop a method of reconstructing the thermal history of sedimentary strata from regional subsidence and sedimentation history. Because generation of petroleum hydrocarbons depends on the integrated time/temperature history of buried organic material, this reconstruction technique can be used to determine the depth to the oil range of the "hydrocarbon generation window" in advance of drilling. By way of example, we reconstruct time/temperature/depth plots and estimate hydrocarbon maturity for one site in the Falkland Plateau and three sites in the North Atlantic near Cape Hatteras. In addition to providing a method for evaluating hydrocarbon potential in frontier regions where there is little or no well control, this approach suggests that there may be significant potential for oil and gas generation on the outer part of the continental rise and in deep-sea sedimentary basins.