Geologic Field Trips to the Basin and Range, Rocky Mountains, Snake River Plain, and Terranes of the U.S. Cordillera

2011 ◽  
Keyword(s):  
Rocky Mountains ◽  
Basin And Range ◽  
Field Trips ◽  
Snake River Plain ◽  
Snake River ◽  
River Plain ◽  
The U.S

Constraints on olivine deformation mechanisms from SKS shear-wave splitting beneath the High Lava Plains, Northwestern Basin and Range and Western Yellowstone Snake River Plain

2021 ◽  
Author(s):  
Eric Löberich ◽  
Maureen D. Long ◽  
Lara S. Wagner ◽  
Ehsan Qorbani ◽  
Götz Bokelmann
Keyword(s):  
Shear Wave ◽  
Upper Mantle ◽  
Basin And Range ◽  
Shear Wave Splitting ◽  
Snake River Plain ◽  
Snake River ◽  
Azimuthal Variation ◽  
Wave Splitting ◽  
High Lava Plains ◽  
River Plain

<p>Shear-wave splitting observations of SKS and SKKS phases have been used widely to map azimuthal anisotropy, and to constrain the dominant mechanism of upper mantle deformation. As the interpretation is often ambiguous, it is useful to consider additional information, e.g. based on the non-vertical incidence of core-phases. Depending on the lattice-preferred orientation of anisotropic minerals, this condition leads to a variation of splitting parameters with azimuth and enables a differentiation between various types of olivine deformation. As the fabric of olivine-rich rocks in the upper mantle relates to certain ambient conditions, it is of key importance to further define it. In this study, we predict the azimuthal variation of splitting parameters for A-, C-, and E-type olivine, and match them with observations from the High Lava Plains, Northwestern Basin and Range, and Western Yellowstone Snake River Plain. This can help to constrain the amount of water in the upper mantle beneath an area, known for a consistent, mainly E-W fast orientation, and increased splitting delay in the back-arc of the Cascadia Subduction Zone. Comparing expected and observed variations renders a C-type olivine mechanism unlikely; a differentiation between A- and E-type olivine remains more difficult though. However, the agreement of the amplitude of azimuthal variation of the fast orientation, and the potential to explain larger splitting values, suggest the occurrence of E-type olivine and the presence of a hydrated upper mantle. Along with a discrepancy to predict delay times from azimuthal surface wave anisotropy, deeper sources could further affect shear-wave splitting observations.</p>

Strain rates and contemporary deformation in the Snake River Plain and surrounding Basin and Range from GPS and seismicity

Geology ◽  
2008 ◽  
Vol 36 (8) ◽  
pp. 647 ◽  
Author(s):  
Suzette J. Payne ◽  
Robert McCaffrey ◽  
Robert W. King
Keyword(s):  
Basin And Range ◽  
Snake River Plain ◽  
Snake River ◽  
Strain Rates ◽  
River Plain

scholarly journals Major reorganization of the Snake River modulated by passage of the Yellowstone Hotspot

2021 ◽  
Author(s):  
Lydia M. Staisch ◽  
Jim E. O’Connor ◽  
Charles M. Cannon ◽  
Chris Holm-Denoma ◽  
Paul K. Link ◽  
...  
Keyword(s):  
Rocky Mountains ◽  
Detrital Zircon ◽  
Columbia River ◽  
Snake River Plain ◽  
Snake River ◽  
Columbia Basin ◽  
Northern Rocky Mountains ◽  
Yellowstone Hotspot ◽  
River Plain ◽  
Hells Canyon

The details and mechanisms for Neogene river reorganization in the U.S. Pacific Northwest and northern Rocky Mountains have been debated for over a century with key implications for how tectonic and volcanic systems modulate topographic development. To evaluate paleo-drainage networks, we produced an expansive data set and provenance analysis of detrital zircon U-Pb ages from Miocene to Pleistocene fluvial strata along proposed proto-Snake and Columbia River pathways. Statistical comparisons of Miocene-Pliocene detrital zircon spectra do not support previously hypothesized drainage routes of the Snake River. We use detrital zircon unmixing models to test prior Snake River routes against a newly hypothesized route, in which the Snake River circumnavigated the northern Rocky Mountains and entered the Columbia Basin from the northeast prior to incision of Hells Canyon. Our proposed ancestral Snake River route best matches detrital zircon age spectra throughout the region. Furthermore, this northerly Snake River route satisfies and provides context for shifts in the sedimentology and fish faunal assemblages of the western Snake River Plain and Columbia Basin through Miocene−Pliocene time. We posit that eastward migration of the Yellowstone Hotspot and its effect on thermally induced buoyancy and topographic uplift, coupled with volcanic densification of the eastern Snake River Plain lithosphere, are the primary mechanisms for drainage reorganization and that the eastern and western Snake River Plain were isolated from one another until the early Pliocene. Following this basin integration, the substantial increase in drainage area to the western Snake River Plain likely overtopped a bedrock threshold that previously contained Lake Idaho, which led to incision of Hells Canyon and establishment of the modern Snake and Columbia River drainage network.

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