Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


17354.pdf (10.27 MB)

ETD Abstract Container

Abstract Header

From terrane accretion to glacial erosion: Characterizing the evolution of the St. Elias orogen in southeast Alaska and southwest Yukon using low-temperature thermochronology

Piestrzeniewicz, Adam
http://orcid.org/0000-0003-3673-8392
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439279821

Abstract Details

2015, MS, University of Cincinnati, Arts and Sciences: Geology.
The border region between southeastern Alaska and southwestern Yukon is marked by the extreme topography of the St. Elias Mountains, the world’s tallest coastal mountain range with peaks rising up to ~6,000 m asl. This high topography is coincident with the indenting corner of the Yakutat microplate where it collides with the North American plate. Here, the plate boundary forms a ~30 degree syntaxial bend where dextral strike-slip motion along the Fairweather Fault transitions to convergence and subduction-collision-related deformation. A combination of tectonic uplift and efficient glacial erosion has produced the remarkable relief in the St. Elias Mountains and also contributes to very high exhumation rates (>4 mm/yr). The new bedrock ages presented in this study include 125 new thermochronometric ages from 43 samples including apatite and zircon (U-Th)/He and fission track ages. The youngest ages (<6 Ma AHe; <15 Ma AFT; <40 ZHe; <60 ZFT) are confined within the Seward and Hubbard Glacier catchments and sharply transition to older ages (>15 Ma AHe; >70 Ma AFT; >100 Ma ZHe and ZFT) north and east of the Hubbard Glacier. The cooling ages record a series of tectonic events including late Mesozoic and early Cenozoic terrane accretion, Paleocene and Eocene cooling related to spreading ridge subduction, and mid Eocene to Present exhumation due to Yakutat subduction and collision. New ages provide evidence for the Border Ranges Fault as the backstop to deformation prior to ~20 Ma but strain reorganization since ~20 Ma has produced differential exhumation north of the Border Ranges Fault suggests strain transfer along the postulated Totschunda-Connector Fault. Tectonic and surface process interactions are explored in order to explain the variation between exhumation beneath the Seward and Hubbard Glaciers and exhumation of ice-free ridges at higher elevation. Effective glacial erosion enhances exhumation and likely produces an elevated geothermal gradient beneath large glaciers. Rapid exhumation beneath glaciers could have initiated positive feedbacks between crustal and surface processes at ~6 Ma but exhumation rates appear to have decreased since ~2 Ma, preventing a tectonic aneurysm from fully developing.
Eva Enkelmann, Ph.D. habil. (Committee Chair)
Craig Dietsch, Ph.D. (Committee Member)
Dylan Ward, Ph.D. (Committee Member)
135 p.
Geology
St Elias; exhumation; thermochronology; Alaska; Yukon; Yakutat collision

Recommended Citations

Citations

  • Piestrzeniewicz, A. (2015). From terrane accretion to glacial erosion: Characterizing the evolution of the St. Elias orogen in southeast Alaska and southwest Yukon using low-temperature thermochronology [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439279821

    APA Style (7th edition)

  • Piestrzeniewicz, Adam. From terrane accretion to glacial erosion: Characterizing the evolution of the St. Elias orogen in southeast Alaska and southwest Yukon using low-temperature thermochronology. 2015. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439279821.

    MLA Style (8th edition)

  • Piestrzeniewicz, Adam. "From terrane accretion to glacial erosion: Characterizing the evolution of the St. Elias orogen in southeast Alaska and southwest Yukon using low-temperature thermochronology." Master's thesis, University of Cincinnati, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439279821

    Chicago Manual of Style (17th edition)

ucin1439279821
325
© 2015, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.