GEOL5690 Western US Tectonics

Tectonic History of the Western United States

GEOL 5690, Spring 2024

Meet: Wednesdays and Fridays 11:30-12:45, BESC 440E.

Instructor: Craig Jones, ESCI 440C, cjones@colorado.edu

Text: Turcotte and Schubert, Geodynamics, 2nd or 3rd edition.
Baldridge, Geology of the American Southwest is optional
Stüwe, Geodynamics of the Lithosphere: An Introduction can be helpful

News:

Class projects (written version) wil be due May 7 by 5 pm. (Earlier would be nice).
Oral presentations (15 minutes apiece, ideally a bit less) on final class May 1.

Syllabus (mostly updated for 2024)

Research aids webpage
Bibliography (background readings, not required readings, includes more older literature)
Announcement of the course
Links of use for background:
- Ron Blakely's original images at Northern Arizona are now gone. Newer images at the (commercial) Deep Time Maps website.
- Tectonics of the Western U.S. site developed by GEOL5700 in 1999, 2002, 2003, 2005, 2010 and 2013 (needs some TLC to be fully updated). 2016 class examined Hildebrand's Rubia hypothesis for creation of the western U.S. 2021 considered oceanic plateau collision with SW US.
Bob Anderson's math primer might be of some interest.

Schedule (older agenda items on a separate page)

Friday, 4/19: Shatsky Conjugate, Alternative models. How do we know there was a Shatsky conjugate? How can we decide where it was? How do we determine its effect on the surface? What should alternative models predict? What options are there?

Please read and be ready to discuss: Liu, L., Gurnis, M., Seton, M., Saleeby, J., Müller, R. D., and Jackson, J. M., 2010, The role of oceanic plateau subduction in the Laramide orogeny: Nature Geoscience, v. 3, no. 4, p. 1-5, doi: 10.1038/ngeo829. Note there is a supplement that can be of some use.
If you are curious, a recent paper with some challenges for the Shatsky story: Schwartz, J. J., Lackey, J. S., Miranda, E. A., Klepeis, K. A., Mora-Klepeis, G., Robles, F., and Bixler, J. D., 2023, Magmatic surge requires two-stage model for the Laramide orogeny: Nature Communications, v. 14, no. 1, 3841, doi: 10.1038/s41467-023-39473-7.
Another resource. How much should we believe a specific seismic tomographic model? One thing you can do is compare a bunch of models...which would be daunting except that there are tools at IRIS that allow one to make these plots fairly easily. You might want to fist identify models relevant for your concerns (hit the "Earth Models" link, where models are listed by extent) and then, armed with the shorthand ID of the models of interest, you can make arbitrary cross sections, stacked sections, stacks of map views at different depths, etc.

Wednesday, 4/24: Paleoelevation. What approaches work for getting ancient elevations? What are the assumptions? What are the weaknesses? Focus will be on "Nevadaplano"; consider the differences in interpretations of these two papers and why they do differ:

Friday, 4/26: Gravitational potential energy, Basin and Range extension and Core Complexes. What are the sources of stress necessary to drive deformation? How does lithospheric structure affect those stresses? What is a core complex, and how might they form? What is the relationship between Basin and Range extension and the evolution of magmatism?

Forces acting on the lithosphere (handout) (might note new paleoelevation handout covering some of Wednesday's class material)
Turcotte and Schubert, pp. 226-229 (section 6-1, 6-2); (Baldridge sec. 8.4)
Buck, W. R., Modes of continental lithospheric extension, J. Geophys. Res., 96, 20,161-20,178, doi: 10.1029/91JB01485,1991.
Images used in class

Wednesday, 5/1: Term project presentations. Please send whatever PowerPoint/Keynote you intend to show prior to class so they can all be on one computer. Everybody gets 15 minutes, but aim for less so there can be some Q and A and discussion.