PRE-MISSISSIPPIAN STRATIGRAPHY AND PROVENANCE OF THE NORTH SLOPE OF ARCTIC ALASKA: A RECORD OF IAPETUS CLOSURE AND STRIKE-SLIP DEFORMATION ALONG THE NORTHERN MARGIN OF LAURENTIA

Pre-Mississippian rocks of the North Slope subterrane of the Arctic Alaska–Chukotka microplate are exposed throughout the northeastern Brooks Range of Alaska and Yukon and comprise at least four major tectono-stratigraphic packages: 1) a Neoproterozoic (Tonian)–Early Devonian platformal carbonate succession; 2) an Ediacaran–Ordovician(?) mixed carbonate and siliciclastic passive margin succession; 3) a late Cambrian–Early Devonian(?) allochthonous oceanic assemblage (Whale Mountain allochthon); and 4) an early Cambrian–Silurian volcanic arc succession (Doonerak arc complex). New geological, geochronological, and geochemical data collected from the Doonerak fenster and northeastern Brooks Range suggest that these discrete tectono-stratigraphic units were assembled in a long-lived and potentially oblique accretionary event that coincided with phases of Taconic–Caledonian–Ellesmerian tectonism (~490–400 Ma). U-Pb geochronologic and Hf isotopic analyses on zircon from mafic and volcaniclastic rocks from the Doonerak fenster indicate that the volcanic arc complex records juvenile Ordovician–Silurian island arc magmatism outboard of the Laurentian margin. In the northeastern Brooks Range, new detrital zircon U-Pb and Hf isotopic data, coupled with structural and stratigraphic relationships, indicate that the Ediacaran–Ordovician passive margin succession may have been juxtaposed with the now dismembered late Cambrian–Early Devonian(?) Whale Mountain allochthon in an accretionary prism sometime between the Ordovician–Middle Devonian. Here, we propose that the Doonerak arc complex and Whale Mountain allochthon were amalgamated in a highly oblique collisional event that converted the northeastern passive margin of Laurentia into an active strike-slip orogen. These stratigraphic, geochronologic, and structural relationships position the discrete tectono-stratigraphic packages of the North Slope subterrane along strike with the Clements Markham fold belt and Pearya terrane of Ellesmere Island during the closure of the northernmost tract of the Iapetus Ocean.