PALEOGEOGRAPHY AND CORRELATION OF LATE PALEOZOIC CRATONIC MARGIN TECTONO-STRATIGRAPHIC UNITS FROM NEVADA TO WESTERN CANADA

The NW Pangea margin was tectonically active during the late Paleozoic and Early Triassic. Tectonic events between the latest Devonian Antler to the latest Permian Sonoma orogeny have been documented in Nevada. Many of these events, as recognized by the generation of unconformities, can be correlated into W. Canada using conodont biostratigraphy. These events are best recognized in the latest Pennsylvanian to Permian succession cropping out in east-central BC and in the subsurface of west-central Alberta and can be linked to tectonism in pericratonic terranes located in central BC and the Yukon. Along much of the Canadian margin, during this time, cool-water deposition with sparse biota prevailed, including spiculitic and phosphatic dolo-siltstone, secondary chert, and cool-water conodonts of the Johnston Canyon and Ranger Canyon formations. However, basins with a distinct history were generated locally on the cratonic margin. The Kisosowin Sea was generated during the Late Pennsylvanian and Early Permian (=C6 and P1 events; Strathearn Basin, NV) by extension and localized uplift that protected the sea from cold upwelling water. Belcourt Formation carbonate within the Kisosowin Sea includes a McCloud fauna of fusulinaceans, corals, and Palaeoaplysina. The depocentre shifted eastward during Artinskian to Kungurian to form the Peace River Basin, presumably by renewed extension (=P2 event; Dry Mountain Trough, NV). Throughout this Kasimovian to Kungurian interval, a west-facing arc (=pericratonic terranes; Yukon-Tanana and Quesnellia) migrated seaward as a broad back-arc Slide Mountain Ocean formed. An angular unconformity is locally recognized below the Middle Permian Fantasque and Ranger Canyon formations (=P4 event; Park City/Phosphoria Basin, NV). These units are both thin and widespread, and may mark a tectonically quiet interval when the Slide Mountain Ocean was widest. Deposition of the Fantasque Formation shifted westward during the late Capitanian as a result of a major sea-level lowstand. Subsequent transgressive deposits are recorded only locally because of significant basin reorganization during the Late Permian, but are widespread by the Early Triassic Montney Formation. At the same time, pericratonic terranes record a dramatic shift to an east-facing zone and Slide Mountain closure.