3D Strain at Transitions in Foreland Arch Geometry: Structural Modeling of the Beartooth Arch - Rattlesnake Mountain Transition, NW Wyoming

Thomas Neely
Colorado State University, Department of Geosciences
Fort Collins, Colorado
[email protected]

How is 3D strain accommodated at transitions in foreland arch geometry? Basement-involved arches of the Laramide Central Rocky Mountain foreland, which bifurcate, anastamose, and change orientation and structural style along strike, display complex structures at these transition zones. The presence of these structures, which include backthrusts, anomalous east-west orientations, and oblique-slip, may be explained by the following hypotheses: 1) oblique, preexisting weaknesses are an important component of the strain and allow a more even strain distribution; 2) slip transfer between parallel, oppositely vergent faults requires structurally complex transition zones; and 3) 3D jogs in arch geometry require complex structures for strain compatibility. I propose to test these hypotheses by investigating the causes and mechanisms by which the Beartooth arch, NW Wyoming, transitions into anomalously oriented and complexly vergent second-order structures, including the Pat O’Hara and Rattlesnake Mountain anticlines.

AAPG Search and Discovery Article #90033©2004 AAPG Foundation Grants-in-Aid