COLLABORATIVE RESEARCH: The Fairweather-St. Elias Orogenic System: A Slip-Partitioned Transpressional Orogen?

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9725035 Pavlis A lingering controversy in plate tectonics surrounds the way in which continental crusts interact in collision zones. The arguments center on if and how strain is partitioned among or around several possible crustal blocks. In southeast Alaska the St. Elias collision region includes the largest concentration of high peaks in North America. The conventional explanation for this region is that a continental microplate (the Yakutat block) is converging with the North American plate. An alternative hypothesis holds that slip is partitioned into a strike-slip component and a contractional component allowing a transpressional boundary and that microplates are not involved. This Pavlis and Bruhn study will test these hypotheses by looking for the predictions of the second. In particular, field mapping and structural analysis will be done to evaluate recent an active motion on the predicted strike-slip faults, and examining off-shore seismic reflection data will be analyzed to look for deformation in the predicted off shore fold and thrust belt. The results will bear directly on the resolving the controversy here in Alaska, but will also reveal generic results that will allow generalizing about the behavior of transpressive plate boundaries in general.