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| Yakutat terrane | |
|---|---|
| Name | Yakutat terrane |
| Type | Terrane |
| Region | Alaska |
| Country | United States |
| Coordinates | 59°32′N 139°44′W |
Yakutat terrane is an exotic crustal fragment located along the northern Gulf of Alaska and adjacent portions of southern Alaska and western Canada. It is notable for its thick sedimentary and ophiolitic sequences, high rates of uplift, and active tectonic interactions with the North American Plate, the Pacific Plate, and the Alaska Range orogenic system. Research on the terrane integrates field mapping, geochronology, paleontology, and geodesy conducted by institutions and agencies across the Pacific Rim.
The terrane comprises a composite assemblage of volcanic, plutonic, metamorphic, and sedimentary units including Mesozoic to Cenozoic strata, mélange, and accretionary prism materials mapped in coastal exposures and alpine outcrops by teams from United States Geological Survey, University of Alaska Fairbanks, Geological Survey of Canada, Smithsonian Institution, and international collaborators such as University of British Columbia. Lithologies include basaltic and andesitic volcanic rocks, pelagic cherts, radiolarian-bearing siliceous rocks, submarine gravels, turbidites, and exotic blocks of ultramafic rocks interpreted as ophiolite fragments studied using techniques from Massachusetts Institute of Technology, Stanford University, California Institute of Technology, and University of Washington. Igneous intrusions and plutons within the terrane have been dated using U-Pb zircon methods at facilities like Lamont–Doherty Earth Observatory and Oak Ridge National Laboratory, linking magmatism to regional arc systems and back-arc basins recorded in work by Geological Society of America, American Geophysical Union, and European Geosciences Union.
The Yakutat crustal block migrated and accreted during Mesozoic and Cenozoic time through processes documented in plate kinematic reconstructions by researchers at Scripps Institution of Oceanography and NOAA. Convergence between the terrane and the North American Plate involved interaction with the Pacific Plate, Kula Plate, and possible remnants of the Farallon Plate, with episodes of strike-slip and transpressional deformation tied to regional structures such as the Denali Fault, Fairweather Fault, and the Queen Charlotte Fault. Paleomagnetic studies from Princeton University and University of California, Berkeley provide constraints on paleolatitude changes, while thermochronology from Yale University and University of Colorado Boulder documents rapid exhumation and cooling associated with collision and uplift that influenced the development of the Chugach Mountains, Saint Elias Mountains, and the Alaska Range. Accretion processes have been modeled in numerical simulations by groups at ETH Zurich and University of Tokyo, and field correlations use mapping standards from British Geological Survey.
The terrane extends from coastal regions near Yakutat Bay eastward and inland beneath glaciers and icefields that are part of the St. Elias Mountains and across parts of the Copper River Basin and southern Yukon margin as interpreted in compilations by USGS National Geologic Map Database and Geological Survey of Canada Open File. Boundaries are defined by major faults and suture zones identified in seismic reflection profiles acquired by USGS, National Oceanic and Atmospheric Administration, and academic cruises from University of Alaska Museum of the North and international partners including GEBCO projects. Surface expression includes moraines and fjords examined by teams from NASA, National Snow and Ice Data Center, and mountaineering reports archived at Alaska Maritime National Wildlife Refuge and Glacier Bay National Park and Preserve.
Stratigraphic sections contain fossil assemblages studied by paleontologists at Smithsonian Institution National Museum of Natural History, University of California Museum of Paleontology, and Royal Ontario Museum that include Cretaceous ammonoids, Eocene foraminifera, and radiolarian faunas used for biostratigraphic zonation and correlation with coeval sequences in British Columbia, Washington (state), and Alaska Peninsula. Key fossiliferous horizons have been reported in publications associated with Paleontological Society, Journal of Paleontology, and university theses from University of Alaska Southeast. Microfossil analyses using scanning electron microscopy facilities at Carnegie Institution for Science and stable isotope labs at Caltech provide paleoenvironmental reconstructions tying depositional settings to global events recorded by Deep Sea Drilling Project and Integrated Ocean Drilling Program reference sections.
The terrane region is seismically active, producing earthquakes recorded by networks operated by Alaska Earthquake Center, Pacific Northwest Seismic Network, and International Seismological Centre. Megathrust and crustal earthquakes along nearby subduction zones and strike-slip faults have generated tsunamis, landslides, and glacier-related hazards documented in reports by FEMA, USGS Earthquake Hazards Program, and hazard assessments prepared by Alaska Division of Geological & Geophysical Surveys. Ground deformation measured by GPS arrays and interferometric synthetic aperture radar from European Space Agency and NASA Jet Propulsion Laboratory reveal rates of convergence and uplift that influence glacial dynamics monitored by National Park Service and World Glacier Monitoring Service.
The Yakutat assemblage hosts mineral occurrences including placer gold, copper, molybdenum, and potential hydrocarbon-bearing strata investigated by industry groups such as BP, ExxonMobil, and exploration firms working with data from US Minerals Management Service and licensing overseen in part by Alaska Department of Natural Resources. Aggregates, dimension stone, and strategic minerals have been evaluated in economic assessments by U.S. Bureau of Land Management, Natural Resources Canada, and consulting firms linked to Society of Economic Geologists and American Institute of Professional Geologists. Resource development considerations balance conservation and indigenous land-use claims involving organizations like Central Council of the Tlingit and Haida Indian Tribes of Alaska and Yukon First Nations, with environmental review frameworks administered under statutes similar to those enforced by Environmental Protection Agency and provincial counterparts.
Category:Terranes Category:Geology of Alaska Category:Geology of British Columbia