Date of Award

2007

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Peter O. Koons

Second Committee Member

Scott E. Johnson

Third Committee Member

Terry L. Pavlis

Abstract

Plate boundary corners 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 corner environment. 3D numerical models show corner 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 thrusts 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.

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