ABSTRACT The Neoproterozoic–Early Devonian platformal succession of the North Slope subterrane, northeastern Brooks Range, Alaska, represents a carbonate-dominated peri-Laurentian continental fragment within the composite Arctic Alaska–Chukotka microplate. The basal ca. 760–720 Ma Mount Weller Group consists of an ~400 m thick mixed siliciclastic and carbonate succession that records the onset of regional extensional tectonism associated with the separation of southeastern Siberia from northern Laurentia during the break-up of Rodinia. These strata are overlain by ca. 720 Ma continental flood basalts of the Kikiktat volcanic rocks, which provide a link between the northeast Brooks Range platformal succession and the ca. 723–717 Ma Franklin large igneous province (LIP) of northern Laurentia. The overlying Sturtian Hula Hula diamictite and Cryogenian–Ediacaran Katakturuk Dolomite record abbreviated thermal subsidence of the northeast Brooks Range platformal succession prior to renewed Ediacaran–early Cambrian extensional tectonism and deposition of the overlying lower Paleozoic Nanook Group (new name). Equivalent strata of the deep-water Cryogenian–lower Cambrian(?) Ikiakpuk Group (new name) are identified herein with new δ 13 C carb and 87 Sr/ 86 Sr isotopic data from the Fourth Range of the northeastern Brooks Range. The Nanook Group is formally divided herein into the Black Dog and Sunset Pass formations, which record isolated peri-Laurentian platformal carbonate sedimentation along the northern margin of Laurentia, in an analogous tectonic position to the modern Bahama Banks. A profound Late Ordovician(?)-Early Devonian unconformity within the platformal succession is marked by subaerial exposure, paleokarst development, and tilting of the northeast Brooks Range peri-Laurentian platformal fragment prior to deposition of the overlying Lower Devonian Mount Copleston Limestone.

ABSTRACT The Neoproterozoic–Early Devonian(?) northeast Brooks Range basinal succession of northern Alaska and Yukon represents a peri-Laurentian deep-marine carbonate and siliciclastic succession within the composite Arctic Alaska–Chukotka microplate. The basal Firth River Group consists of a mixed siliciclastic and carbonate succession that is divided into the informal Redwacke Creek, Malcolm River, and Fish Creek formations. New U-Pb detrital zircon geochronology and δ 13 C carb and 87 Sr/ 86 Sr isotopic data from these strata, in combination with previously reported and new trace fossil discoveries, suggest the Firth River Group is Cryogenian(?)–middle(?) Cambrian in age. These strata interfinger with or are depositionally overlain by the siliciclastic-dominated lower Cambrian–Middle Ordovician(?) Neruokpuk and Leffingwell (new name) formations, which potentially record a distal expression of Cambrian extension and condensed passive margin sedimentation along the northern margin of Laurentia. All of these units are unconformably overlain by the synorogenic Clarence River Group, which is divided into the informal Aichilik and Buckland Hills formations. New U-Pb detrital zircon geochronology and previous macrofossil collections suggest the Clarence River Group is Late Ordovician-Early Devonian(?) in age. Here, we present new sedimentological observations, stratigraphic subdivisions, detrital zircon U-Pb geochronology and Lu-Hf isotope geochemistry, detrital muscovite 40 Ar/ 39 Ar geochronology, and carbonate δ 13 C carb and 87 Sr/ 86 Sr isotope geochemistry from the basinal succession that revise previous tectono-stratigraphic models for this part of Arctic Alaska and support correlations with age-equivalent strata in the Franklinian basin of the Canadian Arctic Islands and Greenland.

ABSTRACT The North Slope subterrane of Arctic Alaska extends from the northeastern Brooks Range of Alaska into adjacent Yukon, Canada, and includes a pre-Mississippian deep-water sedimentary succession that has been historically correlated with units exposed in the Selwyn basin of northwestern Laurentia. Sedimentary provenance data, including Sm-Nd isotopes and major and trace element geochemistry, provide detailed geochemical characterization of the regional pre-Mississippian strata of the North Slope subterrane. Combined with paleontological and geochronological age constraints, these new data record a marked shift in provenance in the Ordovician–Devonian(?) Clarence River Group, evidently linked to an influx of juvenile, arc-derived material. The timing and nature of this provenance change are consistent with early Paleozoic tectonic reconstructions of the Arctic margin that restore the North Slope subterrane to northeastern Laurentia (present coordinates), proximal to the Appalachian-Caledonian orogenic belt. Such a restoration requires significant post-Early Devonian sinistral strike-slip displacement to later incorporate the North Slope subterrane into the composite Arctic Alaska terrane.