Eastern Cordilleran Foldbelt of Northern Canada: Its Structural Geometry and Hydrocarbon Potential

Abstract

The eastern Cordilleran foldbelt of northern Canada embraces that part of the foreland thrust and foldbelt north of lat. 60°N, including the continental shelf of southern Beaufort Sea. The sedimentary succession there lies with pronounced unconformity on continental crust, presumably crystalline rocks of the Hudsonian (1,750 Ma) basement, and ranges in thickness from an estimated 4 mi (7 km) along the eastern margin of the foldbelt to more than 12 mi (20 km) in the interior. Regional and interregional unconformities divide the succession into five discrete tectono-stratigraphic sequences, ranging in age from Proterozoic (Helikian) to Holocene. These sequences are termed, from oldest to youngest, Inuvikian, Rapitanian, Franklinian, Ellesmerian, and Brookian. The region is characterized by bundles of en echelon folds cut by two major fault systems, the Richardson fault array bordering the foreland and the Kaltag fault zone transecting the foldbelt. Late Cretaceous and Tertiary horizontal contraction with concomitant vertical thickening of the supracrustal wedge is roughly one-fourth that of the eastern Cordillera of southern Canada. Potential hydrocarbon traps in Paleozoic and Mesozoic rocks of the northern Cordillera commonly occur within these en echelon fold bundles. Thus, their locations are predictable because they are arranged systematically right- and left-hand en echelon. In the Cenozoic succession of the Arctic coastal plain and continental shelf, however, closures are arranged only crudely en echelon. Current estimates of the combined oil and gas resources of the eastern Cordilleran foldbelt of northern Canada and the adjacent interior platform are about 10 billion bbl of oil and 123 tcf of natural gas, with the preponderance of resources being confined to the Upper Cretaceous and Tertiary (Brookian) sequence.