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Abstract: Laramide Faulting and Tectonics of South-Central Colorado

Branislav K. Jurista, Stephen L. Fryer, Eric A. Erslev

How did the Colorado Plateau impinge on the North American foreland during the Laramide Orogen? Minor fault studies in south-central Colorado provide tests of multi-stage, rotational, strike-slip, and differential displacement hypotheses for the interaction of the Colorado Plateau and the craton.

The Rocky Mountain front, delineated by resistant exposures of uplifted sedimentary and Precambrian rocks, forms an en echelon pattern defined by southeast-plunging ranges which step to the northeast. In the Canon City embayment, an enclave between the southeast-plunging Wet Mountains and the emerging Front Range to the north, minor faults in Cretaceous sandstones indicate a N70E principal compression direction. Similar compression directions from the Front Range to the north suggests a uniform regional stress field and convergence direction for the Rocky Mountain front in Colorado.

Faults along the axis of the Wet Mountains bound inliers of sedimentary rocks and have been hypothesized to be strike-slip faults related to the northward emplacement of the Colorado Plateau. Minor faulting in Cretaceous sandstones at Webster and Twelve mile parks show a single stage of N60E compression perpendicular to the Ilse fault, indicating thrust faulting and contradicting previous hypotheses of major strike-slip faulting. Strike-slip faulting does occur on NE-SW and E-W faults connecting different strands of the Ilse fault. No evidence for large-scale strike-slip faulting parallel to the Colorado Plateau margin was seen, although potential strike-slip faults in the Echo Park basin were not adequately exposed to determine stress or slip directions.

AAPG Search and Discovery Article #90959©1995 AAPG Rocky Mountain Section Meeting, Reno, Nevada