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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 4. (April)

First Page: 660

Last Page: 660

Title: Cretaceous Olistostrome Model, Brooks Range, Alaska: ABSTRACT

Author(s): R. C. Crane

Article Type: Meeting abstract

Abstract:

The foothills area of the Brooks Range thrust belt in the area between the Itkillik River and the Etivluk River is composed dominantly of shallow, thrusted olistostrome sheets. Three olistostrome units can be recognized based on the dominant lithology of contained olistoliths and age of the matrix shales. The lower unit is Tithonian to mid-Valanginian in age and is characterized by abundant graywacke and turbidite, mafic rocks, black cherts, olistoliths of Norian-Rhaetic shales, Nuka sands, and glide sheets of Upper Devonian to Lower Mississippian rocks. Olistolights were derived from the Misheguk, Ipnavik, and Nuka Ridge allochthonous sequences.

The middle unit is of late Valanginian age and has olistoliths of Norian shales; more abundant Upper Triassic chert; Otuk Formation; variegated, radiolarian, black and white cherts; Siksikpuk facies red, green and black shales; Upper Jurassic graywacke; and minor occurrences of mafic rocks. The unit is characterized by glide sheets of Triassic white and multicolor cherts. Olistoliths are derived from Nuka Ridge and Brooks Range sequences.

The upper unit is Hauterivian in age and olistoliths include reworked material from all older units. Olistoliths are few and widely scattered. Isolated outcrops of white chert and conglomerate boulders are characteristic.

The oldest unit was originally deposited in a now-destroyed "southern" basin, south of the Brooks Range. The middle unit was originally deposited in a basin near the present mountain front and the upper unit in the Colville trough. Each unit developed in front of and was sourced from advancing thrust sheets.

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Copyright 1997 American Association of Petroleum Geologists