Precambrian basement structure and Laramide deformation revealed by seismic reflection profiling in the Laramie Mountains, Wyoming

Authors:
  • MSM. A. Speece
    M. A. Speece
  • BFB. R. Frost
    B. R. Frost
  • SSS. B. Smithson
    S. B. Smithson
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Abstract
The University of Wyoming conducted seismic reflection profiling in the Laramie Mountains of Wyoming to investigate the nature of Precambrian crustal structure and Laramide deformation in the region. Here the imaging of layering in the Laramie Anorthosite complex confirms that layered intrusions can be reflective and establishes an analog for interpreting events in other seismic reflection data sets where layered intrusions could be the cause of multicyclic events. Moreover, the presence of prominent primary layering in the Complex supports a conclusion that it formed in situ and not as the result of the emplacement of a diapiric crystal mush. Imaging of Laramide thrusts in the Laramie Mountains adds credence to the idea that brittle faults can be reflective in some situations. Migrated apparent dips on these faults are 30° westward. Basement‐involved compressive structures, consisting of monoclinal folding and a fault triple junction, demonstrate that compression controlled the style of deformation during the Laramide orogen in Wyoming. West dipping Precambrian structures imaged in these data have a similar attitude to the Laramide structures, suggesting that Laramide deformation was influenced by Precambrian features. These Precambrian structures may be subthrust slices of exotic Proterozoic terranes.

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