Abstract: Amelia Zhi Yi
Laramide foreland deformation in Wyoming represents a classic tectonic province, yet there are outstanding questions about the kinematic and mechanical processes responsible for the mountain systems seen today. The archetype Laramide orogen, which spans over 1,200km from Central Montana to New Mexico, was formed during the Late Cretaceous to early Paleogene. Sedimentation and thermochronological data constrain the Wyoming Laramide deformation to between about 70 to 50Ma. Several models have been proposed to explain the mechanical processes that resulted in the spatial distribution of ranges across western North America. Among them are shortening of the thrust belt due to lower crustal detachment, basal traction induced by the North American plate with respect to shallow subduction of the Farallon plate, and rotation and indentation of the Colorado Plateau relative to the North American plate. However, timing of initial deformation, and the extent of changes in the location and direction of foreland shortening through time are yet to be constrained. This summer, I will be collecting structural measurements and paleomagnetic samples for Professor Arlo Weil’s ongoing research project in the Wyoming Rockies. The goal of this research project is to gather and analyze stress and strain field data that will provide a substantial structural data set to be used to help reconstruct the kinematic evolution of Laramide foreland deformations.
Field work will be completed over a four week period in July. The regional areas of focus this summer are the Owl Creek, Bighorn , Ferris and Seminoe mountains. The focus of my work will be on collecting comprehensive structural data that includes: fault lineations, stylolite and vein orientations, minor fold trends, joint systems, fault set orientations, and bedding. Back in the lab, core samples will be prepared and measured for their Anisotropy of Magnetic Susceptibility (AMS) , which will be used as a proxy for paleo-stress. Ultimately these data sets will be combined to test competing kinematic models for the formation for the Laramide throughout western North America.