GEOCHRONOLOGICAL, GEOCHEMICAL, AND SEDIMENTOLOGICAL CONSTRAINTS ON THE EARLY PALEOZOIC HISTORY OF THE NORTH SLOPE OF ARCTIC ALASKA

The composite Arctic Alaska–Chukotka terrane covers an estimated 3,000,000 square kilometers of the Arctic, encompassing the Brooks Range and North Slope of Alaska, the Chukotka Peninsula and Wrangel Island of Arctic Russia, and the adjacent continental shelves of the Beaufort and Chukchi Seas. Despite decades of research inspired by testing conflicting models for Mesozoic Arctic tectonic reconstructions, the pre-Carboniferous origin and displacement history of the Arctic Alaska–Chukotka terrane and its relationship to the northwestern margin of Laurentia remain controversial. Many studies have suggested an exotic, non-Laurentian origin for portions of the Arctic Alaska–Chukotka terrane based on paleobiogeographic affinities of mega- and microfossils and various geochronological constraints. However, we have documented early Paleozoic fossil collections and detrital zircon geochronology from sedimentary successions in northeastern Alaska that suggest a Laurentian origin for the North Slope of Arctic Alaska. We also concentrate on the Neoproterozoic–Ordovician carbonate platform succession from the North Slope to refute the existence of an angular unconformity between the Neoproterozoic Katakturuk Dolomite and Cambro–Ordovician Nanook Limestone and provide new evidence for significant uplift and subaerial exposure prior to deposition of the Lower Devonian Mt. Copleston Limestone. Together, these data demonstrate that the Arctic Alaska–Chukotka terrane is composed of multiple unique continental fragments whose amalgamation can be linked to Caledonian–Ellesmerian terrane juxtaposition along northern Laurentia and provide a new explanation for the enigmatic detritus in the Ellesmerian clastic wedge of the Canadian Arctic islands.