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  1. The Upper Cretaceous to Paleocene Yakutat Group contains a flysch unit and a mélange unit with an unknown source terrane. The provenance of detrital zircons may be the key to understanding the age of clastic units, their source terrane, and correlative rocks along the margin. Two samples were collected from remote and difficult to access areas in Glacier Bay National Park, and these samples can be compared to samples from Harlequin Lake, Russell Fiord, and Yakutat Bay to the north. We dated detrital zircons using standard LA-ICPMS methodology. A sample of Yakutat Group flysch (YGf) from the Grand Plateau Glacier is from quartzofeldspathic turbidites adjacent to the Grand Plateau pluton. It has an MDA of ~66 Ma (Maastrichtian-Paleocene), and the grain-age distribution is dominated by a broad mid-Cretaceous population with ages from ~91 to ~114 Ma, it also has a Jurassic component at ~166. A unique attribute of this sample is that 23% of the zircons are Precambrian with a bimodal population at ~1397 Ma and ~1702 Ma. A sample of sandstone from the Yakutat Group mélange (YGm) from Lituya Bay, was collected from an assemblage of dark lithic sandstones interbedded with basalt, and dark-gray bedded chert. This sample has an MDA of ~108 (Albian), and its grain-age distribution is dominated (88%)by Jurassic dates ranging from ~156 to ~188 Ma. Both samples can be correlated to similar dated units in the area in and around Yakutat Bay. The YGf sample is correlative to the primary zircon facies common to arkosic rocks in both the Yakutat Group flysch and mélange, which we refer to as the Russell zircon facies, with an MDA range from 61-72 Ma, and distinctive Precambrian populations. The YGm sample is more complicated, but it appears to belong to the Shelter Cove zircon facies, dominated by mid-Cretaceous lithic sandstones that occur only in the mélange. The Yakutat terrane has been translated along the margin of the Cordillera, and candidate correlative rocks are to the south. We are intrigued that similar facies with similar grain-age distributions occur in the Western Mélange Belt in the North Cascades foothills in WA. We evaluate the correlation and connection between the Yakutat and the WMB and post Paleocene translation of part of this once contiguous unit. 
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  2. This six-student project focused on the geology of the Chugach and Prince William terranes in northern Prince William Sound, Alaska. The Chugach-Prince William (CPW) composite terrane is a Mesozoic- Tertiary accretionary complex that is well exposed for ~2200 km in southern Alaska and is inferred to be one of the thickest accretionary complexes in the world (Plafker et al., 1994; Cowan, 2003). The CPW terrane is bounded to the north by the Border Ranges fault, which shows abundant evidence of Tertiary dextral strike slip faulting, and inboard terranes of the Wrangellia composite terrane (Peninsular, Wrangellia, Alexander) (Pavlis, 1982; Cowan, 2003; Roeske et al., 2003). Throughout much of the 2200 km long belt of the CPW terrane it is bounded by the offshore modern accretionary complex of the Alaskan margin, but east of Prince William Sound the Yakutat block is colliding into the CPW and this young collision has significantly affected uplift and exhumation of inboard rocks. 
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  3. Cooling ages of tectonic blocks between the Yakutat microplate and the Fairweather transform boundary fault reveal exhumation due to strike-slip faulting and subsequent collision into this tectonic corner. The Yakutat and Boundary faults are splay faults that define tectonic panels with bounding faults that have evidence of both reverse and strike-slip motion, and they are parallel to the northern end of the Fairweather fault. Uplift and exhumation simultaneous with strike-slip motion have been significant since the late Miocene. The blocks are part of an actively deforming tectonic corner, as indicated by the ~14–1.5 m of coseismic uplift from the M 8.1 Yakutat Bay earthquake of 1899 and 4 m of strike-slip motion in the M 7.9 Lituya Bay earthquake in 1958 along the Fairweather fault. New apatite (U-Th-Sm)/He (AHe) and zircon (U-Th)/He (ZHe) data reveal that the Boundary block and the Russell Fiord block have different cooling histories since the Miocene, and thus the Boundary fault that separates them is an important tectonic boundary. Upper Cretaceous to Paleocene flysch of the Russell Fiord block experienced a thermal event at 50 Ma, then a relatively long period of burial until the late Miocene when initial exhumation resulted in ZHe ages between 7 and 3 Ma, and then very rapid exhumation in the last 1–1.5 m.y. Exhumation of the Russell Fiord block was accommodated by reverse faulting along the Yakutat fault and the newly proposed Calahonda fault, which is parallel to the Yakutat fault. The Eocene schist of Nunatak Fiord and 54–53 Ma Mount Stamy and Mount Draper granites in the Boundary block have AHe and ZHe cooling ages that indicate distinct and very rapid cooling between ca. 5 Ma and ca. 2 Ma. Rocks of the Chugach Metamorphic Complex to the northeast of the Fairweather fault and in the fault zone were brought up from 10–12 km at extremely high rates (>5 km/m.y.) since ca. 3 Ma, which implies a significant component of dip-slip motion along the Fairweather fault. The adjacent rocks of the Boundary block were exhumed with similar rates and from similar depths during the early Pliocene, when they may have been located 220–250 km farther south near Baranof Island. The profound and significant exhumation of the three tectonic blocks in the last 5 m.y. has probably been driven by uplift and erosional exhumation due to contraction as rocks collide into this tectonic corner. The documented spatial and temporal pattern of exhumation is in agreement with the southward shift of focused exhumation at the St. Elias syntaxial corner and the southeast propagation of the fold-and thrust belt. 
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