Abstract: Deformation and Foreland Basin Sedimentation in the North-Central Brooks Range, Alaska

Frances Cole, Kenneth J. Bird, David G. Howell, Francois Roure, Zenon C. Valin, Mark J. Pawlewicz, Stephen L. Robbins, Jaime Toro

We have synthesized surface and subsurface geologic data along a transect in the north-central Brooks Range, to provide an integrated view of the Brooks Range fold and thrust belt and the North Slope foreland basin. Field relations, seismic reflection data, and detailed gravity data have been used to model the geometry of the fold and thrust belt. Vitrinite reflectance and Rock-Eval data from Paleozoic through Cretaceous strata in the fold and thrust belt have been analyzed in terms of petroleum source rock potential and thermal maturity. Fluctuations in sedimentation and paleobathymetry in the adjacent foreland basin provide constraints on the timing and magnitude of tectonic loading in the fold and thrust belt.

The fold and thrust belt is dominated by two regionally-extensive structural culminations: (1) a north-vergent tectonic wedge of Devonian Kanayut Conglomerate and Hunt Fork Shale at the northern front of the Brooks Range, and (2) a north-vergent duplex 15 kilometers to the north, representing seven or more repetitions of Carboniferous through Jurassic age rocks of the Lisburne and Etivluk Groups. According to our interpretation of seismic data along the transect, both of these overthrusts involve Lower Cretaceous strata in the footwall, indicating major overthrusting in Early Cretaceous time or later. Based on our analysis of the foreland basin subsidence history, these overthrusts probably formed in Barremian to Aptian time, during an episode of major flexural loading. Low-amplitude holding and minor thrusting in Albian strata farther north, and probably involving lowest Tertiary strata along strike to the east, may have occurred during a second thrust-loading/subsidence event in Cenomanian to early Tertiary time.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California