--> Abstract: Frontal Triangle Zones of the Brooks Range Fold and Thrust Belt, Northern Alaska: Regional Framework, by Thomas E. Moore, Christopher J. Potter, and Paul B. O'Sullivan; #90039 (2005)

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Frontal Triangle Zones of the Brooks Range Fold and Thrust Belt, Northern Alaska: Regional Framework

Thomas E. Moore1, Christopher J. Potter2, and Paul B. O'Sullivan3
1 U.S. Geological Survey, Menlo Park, CA
2 U.S. Geological Survey, Denver, CO
3 Apatite to Zircon, Inc, Viola, ID

Seismic reflection and field observations show that frontal triangle zones are present along most parts of the 500-mile-long north-directed Brooks Range fold-thrust belt. West of the Trans-Alaska Pipeline (TAPS), a regionally extensive triangle zone is located at the Tuktu escarpment, delineated by a floor thrust in the Jurassic and Lower Cretaceous Kingak Shale and a roof thrust in slope deposits of the upper part of the middle Cretaceous Torok Formation. The intervening duplex is developed in structurally competent sandstone-dominated turbidites of the lower Torok Formation. In its rearward parts, the duplex includes an underlying northward-tapering wedge of previously deformed Devonian to Cretaceous strata. East of TAPS, the lower Torok Formation thins and is replaced by shale-rich units. There, the duplex consists of closely spaced linking thrusts and thin horses. The roof thrust is poorly defined and merges upward into detachment folds cored by the Upper Cretaceous shale. In the 1002 area of the Arctic National Wildlife Refuge (ANWR), a northward succession of triangle zones of progressively younger age are developed at the Aichilik High, Jago Ridge, and Marsh Creek anticline. Floor thrusts are located in the Kingak Shale and Upper Cretaceous Hue Shale. Roof thrusts are located near the base of overlying synorogenic clastic wedges, with duplexes formed of similar strata.

In western areas, the frontal triangle zones are gas-prone and were developed during the Paleogene (60-45 Ma) in mostly successor-basin strata of Cretaceous age, whereas in ANWR, the triangle zones are oil-prone and were constructed at ~60, 45, and 25 Ma in synorogenic clastic deposits.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005