Biostratigraphic and biogeographic constraints on the Carboniferous to Jurassic Cache Creek Terrane in central British Columbia
Résumé
Conodonts, radiolarians, foramlnlferids, and corals provide essential blochronologi cal constraints on the geology and tectonics of the Cache Creek Terrane In the Nechako region, central British Columbia. Conodont collections are assigned to 20 faunas ranging in age from Bashkirian (Late Carboniferous) to Norian (Late Triassic), radiolarian collections are grouped into 5 intervals ranging from Gzhelian (Late Carboniferous) to Toarcian (Early Jurassic); 11 fusulinacean assemblages range from Bashkirian to Wordian (Middle Permian); and two coral faunas are of Bashkirian and Wordian age. These fossils collectively document a tong and relatively complete history of complex sedimentary events within the Cache Creek complex that included two major carbonate buildups in the Late Carboniferous (Pope limestone) and Middle Permian (Copley limestone); basaltic eruptions during the Bashkirian and Wordian; the onset of ocean chert sedimentation close to the Carboniferous-Permian boundary and its persistence through the Late Triassic (Sowchea succession); latest Permian and Early Triassic mixed clastics and volcanics (Kloch Lake succession); Middle and Late Triassic reworking of carbonates into breccias (Whitefish limestone) including cave-fill in older limestones (Necostle breccia); and fine-grained clastic sedimentafon persisting Into the lower Jurassic (Tezzeron succession).
Tethyan, eastern Pacific and/or low latitude biogeographic attributes of the Cache Creek faunas are most notable In the Gzhelian (Upper Carboniferous fusulinaceans), Artinskian (lower Permian conodonts), Wordian (Middle Permian fusulinaceans, corals, and conodonts), and Ladinian (Middle Triassic conodonts and radiolarians).