--> ABSTRACT: Regional Structural Framework of the Brooks Range Foothills in the Southern Part of NPRA, Northern Alaska, by Christopher J. Potter and Thomas E. Moore; #90906(2001)

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Christopher J. Potter1, Thomas E. Moore2

(1) U.S. Geological Survey, Denver, CO
(2) U.S.G.S, Menlo Park, CA

ABSTRACT: Regional Structural Framework of the Brooks Range Foothills in the Southern Part of NPRA, Northern Alaska

Syntheses of new seismic interpretations along several long north-south transects of the frontal part of the Brooks Range orogen in the National Petroleum Reserve-Alaska (NPRA) provide the basic framework for a regional three-dimensional model of this thrust system. This system underlies the Brooks Range foothills, bounded on the south by the main Brooks Range mountain front and on the north by the Arctic Coastal Plain. The transect interpretations are based on regional seismic reflection data from the late 1970s and early 1980s, on recent geologic field work, and on new apatite fission-track analyses.

From the main mountain front northward to the deformation front (marked by the transition between fold-controlled valley and ridge topography and the coastal plain), the seismic data show that the basal thrust detachment steps up from the Triassic Shublik Formation, to the Jurassic Kingak Shale, and finally into Cretaceous Torok mudstones. Thrust duplexes stacked above this upward-stepping basal detachment are not uniformly well-imaged, but are readily apparent on some seismic lines. Separate duplex levels consist of Devonian clastic rocks, Mississippian carbonates and shales, a late Paleozoic through early Mesozoic oceanic allochthon, Triassic limestones, and Cretaceous clastic rocks. The frontal part of the deformed belt is underlain by a triangle zone (passive-roof duplex) above the basal detachment within the Torok. Individual anticlines in the Cretaceous clastic rocks behind the thrust front are underlain by tectonically thickened sections of Torok mudstone. The thrust system records protracted crustal shortening that occurred from early Cretaceous into Tertiary time.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado