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full text is available online.
| Document ID: | GEO2007-003 |
| Document Type: | Thesis |
| Author: | Adam Daniel Barker |
| E-mail Address: | |
| URN: | |
| Title: | 3D Mechanical Evolution of the Plate Boundary Corner in SE Alaska |
| Degree: | M.S. |
| Department: | Earth Sciences |
| Committee Chair: | Peter O. Koons, Professor of Earth Sciences, Advisor |
| Chair's E-mail: | |
| Committee Members: | Scott E. Johnson, Professor of Earth Sciences ; Terry L. Pavlis, Professor of Geological Sciences, University of Texas at El Paso |
| Subjects: | Plate tectonics -- Alaska |
| Date of Defense: | 2007 |
| Availability: |
Abstract
Plate boundary comers generate a complex architecture to accommodate the transition from oblique lateral accretion to normal convergence. Geologically recent (5-10 Ma) convergence of the Pacific-Yakutat-North America system has created an early-stage analog to comer convergence characteristic of other comer systems (i.e. Himalayan Eastern Syntaxis). Numerical and analog models have been developed to simulate the early stages of oblique terrane collision in a convergent comer environment. 3D numerical models show comer convergence partitioned into a steep, narrow two-sided mountain wedge along the lateral accretion zone that changes to a wider zone of shortening bounded by inboard and outboard directed thmsts along the frontal accretion boundary. Contraction rates through the frontal accretion zone lessen grading into the strike slip lateral boundary where shear strain rate is intensified. Clockwise rotation of structures also occurs at the transition from shortening to oblique slip. Sandbox analog model results show predominant clockwise rotation along the lateral accretion zone indicating dextral displacement and a larger zone of shortening along the convergent frontal accretion zone. Deformation across the frontal accretion zone wedge shifts from dextral convergence near the corner to the east, normal convergence in the middle, and sinistral convergence to the west. Further strain concentration along with thermal weakening of the brittle crust occurs with focused erosion leading to aneurysm behavior, which is characterized by increased concentration of strain into the exhumed area.
Barker, Adam Daniel, University of Maine, GEO2007-003
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