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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 7. (July)

First Page: 932

Last Page: 933

Title: Demarcation of a Duplex Zone: Rockport Lake Area, Utah: ABSTRACT

Author(s): Michael D. Bradley


The structural relationship between the east-trending Uinta axis and the north-trending overthrust systems in Utah and southwestern Wyoming remains a major structural problem with important implications for regional tectonics and petroleum exploration. This relationship is apparent in the Rockport Lake area where a lateral to oblique ramp formed in the Absaroka thrust system and was folded about the Uinta axis. Three northeast-trending subparallel thrusts forming a duplex zone are exposed at the surface in the Rockport Lake area. From north to south, the thrusts place Kelvin Formation over Evanston Formation, Frontier Formation over Kelvin Formation, and Preuss formation over Frontier Formation, respectively. Ubiquitous stylolitic pressure solution cleavage in the hanging wall of the ramp shows major shortening from the west. South of the Weber River, in the foot wall of the ramp, the stylolitic cleavage is less common but still present.

Angular unconformities between the Frontier and Evanston Formations

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and between the Evanston and lower Wasatch Formations show the Uintas to have risen in two distinct pulses. The earliest rise may have begun by Maestrichtian time and the latest rise, forming the north flank fault system, culminated in the Eocene.

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Copyright 1997 American Association of Petroleum Geologists