DETRITAL ZIRCON U/Pb AGE DETERMINATION: UNDERSTANDING THE PROVENANCE OF THE LATE- CRETACEOUS SHUMAGIN FORMATION, ALASKA

The Chugach-Prince William (CPW) terrane is an Upper Cretaceous to Eocene accretionary complex exposed for ~2200 km in southern Alaska, extending from Baranof Island in the east to Sanak Island in the west. One of the thickest subduction-related accretionary complexes in the world, the CPW terrane is composed of deep-water flysch and associated volcanic rocks and is intruded by near-trench plutons of the 62-50 Ma Sanak-Baranof belt. The location of the accretion of the CPW is a matter of debate. There are two prevailing hypotheses for the location of the CPW at the time of its intrusion by the SanakBaranof belt: either the CPW was formed in situ as the result of accretion related to the subduction of the now subducted Resurrection Plate (Hauessler et al., 2003); or the CPW formed further to the south and has since been translated northward, parallel to the coast (Cowan, 2003). These scenarios would result in distinctly different source regions for the sediment of the CPW flysch, therefore, an understanding of the provenance of the different units in the CPW can help to constrain the location of the CPW at the time of its accretion.