Devonian Stratigraphy of the Moose River Basin, James Bay Lowland, Ontario, Canada

Abstract The Moose River Basin is an intracratonic Paleozoic sedimentary basin underlying the James Bay Lowland of northeastern Ontario and containing strata ranging from Ordovician to Upper Devonian age. Except along the mildly deformed eastern margin strata are generally flat-lying. Devonian carbonates, shales, evaporites and minor sandstones comprise the upper 400 metres of the Paleozoic succession. A thin sequence of unconsolidated Jurassic and Cretaceous clastic sediments overlies the Devonian rocks in the southeastern part of the basin and the entire region is blanketed by Pleistocene glacial deposits and Recent marine clays. The Devonian succession comprises, in ascending order: Lower Devonian Kenogami River (upper part only; dolomitic limestone), Stooping River (mainly limestone) and Sextant (sandstones and shales) Formations; Middle Devonian Kwataboahegan (limestone), Moose River (carbonates, evaporites), Murray Island (limestone) and Williams Island (shale, carbonates) Formations; and the Upper Devonian Long Rapids Formation (black shale, mudstone, minor carbonates). The apparently simple stratigraphy is complicated by lateral facies variations, including a continental to marine transition among the Lower Devonian formations, and biohermal development in the Kwataboahegan Formation. The Long Rapids Formation is of particular interest, as recent conodont-brachiopod studies suggest that both the Givetian-Frasnian (Middle-Upper Devonian) and Frasnian-Famennian boundaries occur within the unit.