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Tolson, R.B., 1987

Structure, stratigraphy, tectonic evolution and petroleum source potential of the Hope basin, southern Chukchi Sea, Alaska

Bibliographic Reference

Tolson, R.B., 1987, Structure, stratigraphy, tectonic evolution and petroleum source potential of the Hope basin, southern Chukchi Sea, Alaska: Palo Alto, California, Stanford University, Ph.D. dissertation, 261 p., illust., map.

Abstract

Multichannel seismic reflection data from the Hope basin of the southern Chukchi Sea, Alaska, reveal a fill of as much as 5.8 km of probable Eocene and younger sedimentary rock. Throughout the geologic history of this basin, tectonics played a major role in controlling sedimentation. The initial faulting and rifting of the basin localized depositional sites and subsequent faulting shifted the major depocenters about the basin. The basin evolved in three main stages. First, isolated half-grabens formed during the early Paleogene in response to transtensional movement along the Kobuk fault zone. The main fault zone trends northeast-southwest across central Kotzebue Sound and displays predominantly normal displacement. However, structural styles observed in seismic data and radically different thermal maturities of juxtaposed Upper Cretaceous rocks along the Kobuk River valley suggest that some component of strike-slip movement occurred. Related faults exhibiting similar structural styles trend southeast-northwest in the main basin southwest of the Lisburne Peninsula. The half-grabens filled with trachytic and basaltic volcanic flows and nonmarine and possibly marine or lacustrine sedimentary rocks. Second, the basin thermally subsided in the early Miocene, and nonmarine sediment was deposited over the entire basin. Third, an extensional phase characterized by reactivation of the Eocene faults and initiation of numerous normal faults commenced during the middle to late Miocene. Extension was coeval with deposition of nonmarine and marine sediment in basin lows not necessarily coincident with the Eocene half-grabens. At the close of this extensional phase, the Kotzebue arch, a basement high trending east-west across the basin, was uplifted. Hydrocarbon potential of the Hope basin remains low primarily because of the abundance in the Kotzebue Sound area of thermally immature sedimentary deposits that are nonmarine and contain predominantly gas-prone organic matter. However, seismic stratigraphic evidence indicates that more oil-prone marine or lacustrine sedimentary rocks may be present in some of the deeper, more thermally mature, undrilled parts of the basin.

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