Rapid exhumation of ice-covered rocks of the Chugach-St. Elias orogen, Southeast Alaska

摘要

Ongoing oblique collision and flat-slab subduction of the Yakutat terrane has produced Earth's highest coastal mountain range, the Chugach–St. Elias orogen in Southeast Alaska. Massive glaciers and ice fields cause extensive erosion, but also limit access to rocks that allow detailed study of the orogen. Fission track and U/Pb dating of detrital zircon from glacial rivers reveal the exhumation history of the Chugach–St. Elias orogen. Orogenic development started ca. 30 Ma and pulses of exhumation occurred 20 ± 2 Ma and 11 ± 2 Ma. Differential exhumation occurred across major fault zones and the locus of exhumation shifted southward. The ca. 5 Ma cooling ages of detrital zircon in the Pliocene–Pleistocene Yakataga Formation reveal that source rock exhumation was likely associated with faulting along the ice-covered Fairweather fault–Contact fault system.