--> Abstract: A Field Test of Foreland-Basin Models in the Overfilled, Nonmarine Part of the Jurassic-Cretaceous Cordilleran Foreland Basin, Central Wyoming, by P. G. Decelles and E. T. Burden; #91012 (1992).

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ABSTRACT: A Field Test of Foreland-Basin Models in the Overfilled, Nonmarine Part of the Jurassic-Cretaceous Cordilleran Foreland Basin, Central Wyoming

DECELLES, P. G., University of Rochester, Rochester, NY, and E. T. BURDEN, Memorial University of Newfoundland, St. John's, Newfoundland, Canada

New lithostratigraphic, biostratigraphic, sedimentologic, and petrographic data from the Morrison and Cloverly Formations (upper Jurassic-lower Cretaceous) in central Wyoming provide a test of recent predictions from theoretical foreland-basin models. In central Wyoming, the Morrison and Cloverly were deposited by alternating sandy-gravelly fluvial systems and muddy fluvial-lacustrine systems over an area of ~120,000 sq. kilometers, several hundred kilometers east of the zone of maximum foreland-basin subsidence. Palynological data indicate that the lower part of the Morrison is Oxfordian and the Cloverly is Neocomian. Morrison sandstones are subarkosic (QmFLt = 83,6,11) whereas Cloverly sandstones are cherty litharenites (QmFLt = 82,0,18). Paleocurrent and provenance data from coarse lithologies indicate derivation primarily from upper Paleozoic through lower Mesozoic strata of the Cordilleran thrust belt to the west and south-southwest.

This part of the basin filled by nearly syntaxial (north-northeast) progradation of major fluvial systems that headed in central Utah. A large component of Cloverly mudrock consists of volcanogenic ash, providing a regional chronostratigraphic zone. The Morrison-Cloverly succession bears several characteristics in common with model predictions for overfilled foreland basins: It filled the basin by prograding into it; its thickness is nearly constant (~90 m) over a vast area well outside of the basin foredeep; and it was deposited primarily by through-flowing fluvial systems. On the other hand, the Morrison-Cloverly also exhibits important differences from model predictions: progradation was subparallel (not transverse) to the mountain belt; subtle intraforeland structures, probably re ctivated, controlled local paleodrainage; and base-level and source-rock changes may have exerted control on lithostratigraphy.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)