Provenance of the Neogene to Holocene sediments drilled by IODP Expedition 341 in the Gulf of Alaska. A single grain geochemical and geochronological study of the glacially influenced denudation history of the evolving St. Elias Orogen using heavy mineral

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The proposed case study investigates the temporal and spatial evolution of the large-scale mass transfer from the St. Elias Orogen, the highest coastal mountain belt on Earth, to the Gulf of Alaska over the last ca. 10 Ma. The targets are sands, silts and diamicts from two sites on the proximal and distal Surveyor Fan, respectively, drilled in the course of IODP Expedition 341 in 2013. The tools applied include single-grain geochemical analysis of heavy minerals. Initial geochemical data on hornblende, garnet and zircon point to a derivation mainly from the Chugach Terrane. The combination with U-Pb age dating of zircon with 40Ar-39Ar age dating of hornblende will allow for constraining the temporal link between onshore denudation and offshore deposition. In the 3rd project year applied for here we plan to concentrate on the provenance evolution during the Mid-Pleistocene Transition (MPT) by applying the same set of tools to a high resolution study of closely spaced samples of Site U1417. The MPT coincides with increased uplift of the St. Elias orogen and accelerated erosion of the mountain belt. This high-resolution approach will provide detailed information helping to reconstruct the relationship of climate change and changing erosion patterns across a major climate transition.