Structure of the Northern Great Plains and Implications for Continental Assembly and Evolution
Current understanding of the evolution of the North American plate in the northern Great Plains is constrained by basement outcrops on the Black Hills uplift combined with subsurface geologic, gravity, magnetic, heat flow, and very few seismic studies of the surrounding region. A Laramide arch, active ~64 - 40 Ma, extends from western Montana through the Black Hills uplift (structural relief ~ 2,000 m) and connects with the Chadron uplift of northwestern Nebraska. This trend crosses both the Wyoming/Trans-Hudson (WP/TH) and Trans-Hudson/Central Plains (TH-CP) province boundaries. A zone of small alkalic and calc-alkalic Laramide plutons (46-58 Ma) trend N.70oW across the Black Hills uplift possibly emplaced along an ancient basement fracture. Localization of the Laramide arch may lie along a transition from thin to thick lithosphere and reflect the surface manifestation of crustal shortening associated with deep-seated reverse faults. Understanding of the deep Proterozoic and Laramide structures requires remote sensing of the subsurface lithosphere beneath the Black Hills and surrounding regions. New seismic stations from the USArray's transportable array and the proposed FlexArray will help us to better understand the origin and tectonic evolution of the North American continental lithosphere, as well as the role of lithospheric roots and asthenospheric mantle flow in driving North American plate motion. In order to image lithospheric structure, we have begun to analyze the initial passive source seismic data from the transportable array stations recently deployed in and around the Black Hills. Shear wave splitting data provide information on the mantle anisotropy in this region and receiver functions on the nature of the crust across the Trans-Hudson collisional boundary.
E. Sandvol et al., "Structure of the Northern Great Plains and Implications for Continental Assembly and Evolution,", vol. 42, no. 3 Geological Society of America, Apr 2010.
Rocky Mountain - 62nd Annual Meeting (2010: Apr. 21-23, Rapid City, SD)
Geosciences and Geological and Petroleum Engineering
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