Francis Sousa
Oregon State University, OR·Earth & Environmental Science
About 55 to 40 million years ago, a huge slab of volcanic ocean crust called Siletzia collided with western North America. The collision is thought to have built mountains, rotated parts of the crust, and moved the plate boundary westward to create today's Cascadia subduction zone.
- Fields
Earth & Environmental Science
- Topics
tectonics
Siletzia
Siletz terrane
- Grants
- 2 known grants, through Aug 2027
What they work on
- Test whether the ancient Tyee river drained a large continental interior from western Idaho or began in the Klamath Mountains, using U-Pb and Lu-Hf analysis of zircon sand grains to trace sediment sources.
- Reconstruct how the Klamath Mountains were uplifted and eroded during sedimentation of the Umpqua and Tyee Groups, using 40Ar/39Ar dating of detrital micas and detrital thermochronology.
- Tie provenance and age data to detailed geologic mapping, stratigraphic analysis and basin subsidence analysis to test models of drainage reorganization after the Siletzia collision.
- Reconstruct the burial, thickening, uplift and erosion of the northern Klamath Mountains before, during and after Siletzia accretion, using multiple mid- and low-temperature thermochronometers.
- Engage a year-long cohort of undergraduates at Cal Poly Humboldt and Oregon State University as primary researchers, applying mineral thermochronometry to Klamath Mountain samples.
More about the research
A subduction zone is where one tectonic plate dives beneath another. The event helped shape the Oregon and Washington Coast Ranges and the deep crustal structure beneath the Pacific Northwest. Much of its rock record is missing or overprinted, so its effects are poorly known. This work reconstructs how the land surface and crust of southwest Oregon responded, using two complementary records: the sediments shed during and after the collision, and the cooling histories of older rocks nearby.
Why it matters
The results could clarify the crustal structure that governs processes in the modern Cascadia subduction zone beneath Oregon and Washington. They could also inform studies of collision zones elsewhere in the world. The work shares data with the Oregon Department of Geology and Mineral Industries. It also trains undergraduates, including community college students, in advanced dating methods usually found only at large research institutions.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
Collaborative Research: Testing Models for Fluvial Response to Eocene Terrane Collision in Western Oregon Using Integrated Tectono-Stratigraphy and Detrital Provenance Analysis
NSF · Sep 2024 – Aug 2027
Collaborative Research: RUI: An undergraduate cohort thermochronology research and mentorship experience investigating the thermo-tectonic record of the northern Klamath Mountains
NSF · Jul 2023 – Jun 2027
Closest labs
Ryan Leary
New Mexico Institute of Mining and Technology, NM·Earth & Environmental Science
Reconstruct paleohydrology, including flow depth, slope and water discharge, of Late Cretaceous to early Eocene river deposits in Laramide basins using quantitative fluvial stratigraphy.
Chelsea Mackaman-Lofland
University of Tennessee-Knoxville, TN·Earth & Environmental Science
Test whether high mountains in western Anatolia delayed hominoid migration from Africa into Eurasia. Reconstruct basin history, crustal thickness from zircon geochemistry, and past elevation using proxy-based paleoaltimetry.
Alexander Pullen
Clemson University, SC·Earth & Environmental Science
Reconstruct the Miocene–Pleistocene sediment sources of the Beaufort-Mackenzie Basin using detrital zircon uranium-lead (U-Pb) dating and neodymium (Nd) isotope provenance analysis.
The school
Oregon State University: 29 labs on PI Pages, $372M a year on research, 238 research doctorates a year.
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