ALBERT

Description: Wrangel Island represents a small but unique exposure of Neoproterozoic basement and its upper Paleozoic and Mesozoic cover within the mostly unexplored East Siberian Shelf. Its geology is critical for testing the continuity of stratigraphic units and structures across the Chukchi Sea from Alaska to Arctic Russia, for evaluating the hydrocarbon potential of this offshore region, and for constraining paleogeography and plate reconstructions of the Arctic. Upper Paleozoic platform carbonates and shales on Wrangel likely match those of the Chukchi Shelf and adjacent North Slope of Alaska (e.g., Sherwood et al., 2002), but Triassic basinal turbidites contrast with Alaska's thin shelfal units. Detrital zircon suites from upper Paleozoic strata on Wrangel reveal that local basement-derived detritus (∼500–800 Ma) decreases up section, replaced by 900–2000-Ma zircon populations compatible with a Baltic shield provenance. Cambrian–Ordovician–Silurian zircons (∼420–490 Ma) are present in lesser abundance in most samples and are inferred to have been derived from the Arctic part of the Caledonide belt. Triassic detrital zircon suites contrast with those from underlying strata: Precambrian zircons have less of an age range (1700–2000 Ma), and Devonian and younger (〈400 Ma) zircons are much more abundant. This change reflects breakup of the carbonate platform during Permian–Triassic rifting, with zircon age populations in Triassic strata compatible with sediment sources in the Urals, Taimyr, and Siberia. Detrital zircon data suggest that Wrangel Island, Chukotka, and northern Alaska (the Arctic Alaska-Chukotka microplate) restore against the Lomonosov Ridge upon closure of the Amerasia Basin and to the edge of the Barents Shelf after closing the Eurasia Basin. The detrital zircon data thus suggest that the Barents Shelf lays close to the paleo-Pacific margin in the early Mesozoic and that subduction-driven tectonics may have been a greater factor in the evolution of the Amerasia Basin of the Arctic than previously suspected. Elizabeth L. Miller has been a professor of structural geology and tectonics at Stanford University since 1979, where she teaches classes in field methods and geology, regional tectonics, structural geology, petrography, microstructures, and rock deformation. Her research interests include shortening and extension-related deformational processes in continental crust and their link to plate motions and magmatism, with focus on the U.S. Cordillera, Alaska, northeast Russia, and the Arctic. More information on her Arctic research can be found at http://pangea.stanford.edu/research/groups/structure/. George Gehrels is a professor at the University of Arizona with interests in tectonics and geochronology. His research activities focus on the evolution of collisional and accretionary orogenic belts and on the development of U-Pb geochronologic techniques. Current projects include field and geochronologic studies of terranes and magmatic assemblages in southeast Alaska, British Columbia, the Himalaya of Nepal, Tibet, the Andes in Argentina and Chile, and the Grand Canyon. He is the codirector of the Arizona LaserChron Center, an National Science Foundation facility that enables researchers to generate U-Th-Pb geochronologic information and also drives the development of new U-Th-Pb geochronologic methods. Victoria Pease is an associate professor of tectonics at Stockholm University, Sweden, where she conducts research in Arctic tectonics, with a focus on provenance investigations. She leads international expeditions throughout the circum-Arctic region, including Arctic Eurasia, Svalbard, northern Greenland, and Arctic Canada. She received her Ph.D. from Oxford University (England) and was a postdoctoral researcher at Uppsala University (Sweden). Sergey Sokolov is the head of the Laboratory of Tectonics of the Oceans and Peri-oceanic Zones at the Geological Institute of the Russian Academy of Sciences in Moscow. His interests lie in the geology and tectonics of the Pacific continental margins where he and his research group conduct field-based, multidisciplinary research on ophiolites, accretionary complexes, island-arcs, and metamorphic complexes. Recent areas of interest include Koryak-Kamchatka, Chukotka, and the South Anyui zone and the Arctic.