The North American segment of the Circum-Pacific, east of the Aleutian Trench, is distinguished from adjoining segments by the absence of an oceanic trench and the lack of recorded seismicity with focal depths exceeding 70 km. The continental margin seaward of the North American Cordillera incorporates a series of irregularly distributed sedimentary basins of late Mesozoic and Cenozoic age. The structural development of these basins was determined by progressive, episodic subsidence accompanied by interbasin uplift.

The tectonic history, structural style, and distribution of the basins demonstrate the presence of a composite system of mobile vertical-stress fields which has endured over the past 140 m.y. The primary forces which created these basins were expressed by increments of episodic and randomly distributed vertical movements, in the same manner in which this fundamental tectonic process is occurring today. A superimposed tangential stress field, also active today, is expressed by strike-slip faults and related structures. These data are mechanically incompatible with hypotheses of overriding crustal plates as currently proposed.

Twenty-one billion barrels of oil and 37 Tcf of gas have been discovered in seven basins. A practical understanding of the structural style and framework of these prime target areas is critical to the realization of the energy potential of the relatively untested basins of this province.