ABSTRACT: Structural and Stratigraphic Evolution of the Utah-Wyoming Thrust Belt: Application of Kinematic Structural Modeling, Critical Taper Theory, and Regional Stratigraphic Reconstructions

SCHIRMER, TAD W., Chevron USA Production Co., Houston, TX

A regional structural cross section, which extends 125 mi (200 km) from the Lakeside Mountains west of the Great Salt Lake in northern Utah to east of the Hogsback thrust fault in the western Wyoming thrust belt, is analyzed using kinematic structural modeling and stratigraphic reconstructions to model the evolution of the eastern Basin-Range and Overthrust belt from Precambrian through Neogene time.

Reverse kinematic modeling and palinspastic stratigraphic reconstructions from Precambrian through Jurassic time determines the regional slope of basement and the geometry of the stratigraphic wedge across the shelf margin before Mesozoic thrusting commenced. Stratigraphic reconstructions and age-dating of synorogenic deposits combined with forward kinematic modeling determines the geometry and timing of thrusting, basement slope, critical taper, and depositional history of the foreland basin during thrust propagation toward the east. Critical taper theory correlates the geometry of the compressional wedge, the paleoslope of the thrust belt, and the gross clast content and depositional history of the developing foreland basin.

The regional structural-stratigraphic kinematic model incorporates a number of significant concepts. Of primary interest are large-scale basement-cored thrust sheets exposed in the Wasatch range in northern Utah, which record significant basement shortening and uplift in the root zone of the thin-skinned thrusts to the east. The analysis sheds new light on modeling the complex structural evolution of the hinterland-foreland transition. This basement-cored thrust culmination built progressively through time starting during late Willard thrust movement in the Lower Cretaceous and continued through Hogsback thrust movement in Eocene time; and is identified as the primary source area for synorogenic deposits in the southern portion of the thrust belt during this time period.

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