THE EARLY NEOPROTEROZOIC SEDIMENTARY SUCCESSION-B OF NORTHWESTERN LAURENTIA - CORRELATIONS AND PALEOGEOGRAPHIC SIGNIFICANCE

The Mesoproterozoic-Neoproterozoic stratigraphic record of ancestral N orth America (Laurentia) comprises three, unconformity-bounded sedimen tary successions that are termed, from oldest to youngest, A, B, and C . Recent and ongoing detailed stratigraphic studies of Succession B, a long with improved geochronology, allow extension and refinement of ex isting correlation schemes for northwestern Canada and Alaska, Success ion B strata include the Shaler Supergroup of the Amundsen Basin, Mack enzie Mountains supergroup of the Mackenzie Mountains fold belt, Pingu icula group of the Wernecke Mountains inlier, Fifteenmile group of the Ogilvie Mountains inliers, and the lower Tindir Group of Tatonduk inl ier.(1) The Katakturuk Dolomite, in the northeast Brooks Range of Alas ka, is included with Succession B on the basis of platformal character , geochronology, and inferred paleogeographic affinity. The framework for regional lithostratigraphic correlation of Succession B is built o n recognition of four distinctive lithostratigraphic assemblages: two thick stromatolitic platformal carbonate assemblages separated by two largely subaerial siliciclastic assemblages, The correlation is suppor ted by geochronology of detrital zircons from the upper quartzarenite assemblage, which indicates a maximum age of ca, 1000 Ma for the lower part of Succession B, These rocks are interpreted to be remnants of a northwesterly trending (present coordinates) early Neoproterozoic bas in-margin promontory (Amundsen-Ogilvie-Mackenzie platform) that develo ped within an intracratonic basin on the northwest margin of Laurentia . The Neoproterozoic stratigraphic record of northwestern North Americ a hears striking similarity to contemporaneous stratigraphy on other c ontinents, particularly in the Amadeus Basin and Adelaide fold belt of central and southern Australia, Reconstructions of the Neoproterozoic supercontinent juxtapose the eastern margin of ancestral Australia ag ainst the western margin of Laurentia during the time these strata wer e being deposited, The Amundsen-Ogilvie-Mackenzie platform consequentl y mag represent a segment (of the margin) of a large intracratonic bas in that rifted apart ,vith the breakup of the supercontinent during th e latest Proterozoic. This hypothesis provides a template for future s equence stratigraphic, chemostratigraphic, biostratigraphic, paleomagn etic, and geochronologic comparisons and has implications for predicti ve economic geology in both areas.