The Arctic Alaska region includes three composite tectono-sedimentary elements (CTSEs): the (1) Arctic Alaska Basin (AAB), (2) Hanna Trough (HT), and (3) Beaufortian Rifted Margin (BRM) CTSEs. These CTSEs comprise Mississippian to Lower Cretaceous (Neocomian) strata beneath much of the Alaska North Slope, the Chukchi Sea and westernmost North Slope, and Beaufort Sea, respectively. These sedimentary successions rest on Devonian and older sedimentary and metasedimentary rocks, considered economic basement, and are overlain by Cretaceous to Cenozoic syn- and post-tectonic strata deposited in the foreland of the Chukotka and Brooks Range orogens and in the Amerasia Basin. (1) The Mississippian-Neocomian AAB CTSE includes two TSEs: (a) The Ellesmerian Platform TSE comprises mainly shelf strata of Mississippian to Middle Jurassic age and includes a relatively undeformed domain in the north and a fold-and-thrust domain in the south. (b) The Beaufortian Rift Shoulder TSE includes Middle Jurassic to Neocomian deposits related to rift-shoulder uplift. (2) The HT CTSE includes four TSEs: (a) The Ellesmerian Syn-Rift TSE comprises Late Devonian(?) to Middle Mississippian growth strata deposited in grabens and half grabens during intracontinental rifting. (b) The Ellesmerian-Beaufortian Sag-Basin TSE comprises Middle Mississippian to Upper Triassic strata deposited in a sag basin following cessation of rifting. (c) The Beaufortian Syn-Rift TSE comprises Jurassic to Neocomian graben-fill deposits related to rifting in the Amerasia and North Chukchi Basins. (d) The Beaufortian Rift-Shoulder TSE comprises Jurassic to Neocomian strata related to rifting and deposited outside rift basins. (3) The BRM CTSE includes two TSEs: (a) The Beaufortian Syn-Rift TSE comprises Middle Jurassic to Neocomian syn-rift strata deposited on attenuated continental crust associated with opening of the Amerasia Basin. (b) The Ellesmerian Platform TSE comprises mainly shelf strata of Mississippian to Middle Jurassic age that lie beneath Beaufortian syn-rift strata.The AAB, HT, and BRM CTSEs contain oil-prone source rocks in Triassic, Jurassic, and Cretaceous strata and proven reservoir rocks spanning Mississippian to Lower Cretaceous strata. A structurally high-standing area in the northern AAB CTSE, northern HT CTSE, and southernmost BRM CTSE lies in the oil window whereas all other areas lie in the gas window. Known hydrocarbon accumulations in the three CTSEs total more than 30 billion barrels of oil equivalent and yet-to-find estimates suggest a similar volume remains to be discovered.
