Biostratigraphic and biogeographic constraints on the Carboniferous to Jurassic Cache Creek Terrane in central British Columbia

Abstract

Conodonts, radiolarians, foraminiferids, and corals provide constraints on the geology and tectonics of the Nechako region. They also support the notion that the Cache Creek Terrane is allochthonous with respect to the North American craton. The 177 conodont collections, assigned to 20 faunas, range in age from Bashkirian (Late Carboniferous) to Norian (Late Triassic); 70 radiolarian collections representing 12 zones range from Gzhelian (Late Carboniferous) to Toarcian (Early Jurassic); 335 collections assigned to 11 fusulinacean assemblages (with associated foram-algal associations) range from Bashkirian to Wordian (Middle Permian); and two coral faunas are of Bashkirian and Wordian age. The fossils document a long but sporadic history of sedimentary events within the Cache Creek Complex that included two major carbonate buildups in the Late Carboniferous (Pope limestone) and Middle Permian (Copley limestone), punctuated by intervening Early Permian deepening; basaltic eruptions during the mid Carboniferous and mid Permian; the onset of oceanic 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 (Whitefish limestone), including cavity fill in older limestones (Necoslie breccia), and fine-grained clastic sedimentation extending into the Early Jurassic (Tezzeron succession). Tethyan, eastern Pacific, and (or) low-latitude biogeographic attributes of the faunas are noted in the Gzhelian (fusulines), Artinskian (conodonts, fusulines), Wordian (fusulines, corals, conodonts), and Ladinian (conodonts, radiolarians). The Cache Creek Terrane lay far to the west of the North American continent during these times.

Deep seismic reflection constraints on Paleogene crustal extension in the south-central Intermontane belt, British Columbia

“…The Cache Creek terrane comprises Mississippian to Early Jurassic imbricated oceanic igneous rocks, limestones, cherts, and mudstones developed on oceanic islands or plateaus, and accretionary assemblages Orchard et al 2001). Ophiolite sequences and overthrust ultramafic rocks, which form the shallowest structural level, have been identified in several parts of the terrane , and the terrane is interpreted to be a stack of thrust sheets that form a westward thinning wedge over Stikinia.…”

Logan Medallist 1. Seeking the Suture: The Coast-Cascade Conundrum

“…The only clearly 'exotic' faunas (as opposed to individual species) of Permian through Middle Jurassic age occur in the accretionary complexes that form the Cache Creek and Bridge River terranes in Canada, and the innermost part of the Chugach terrane (McHugh Complex) in southern Alaska (Clark 1971, p. A54;Monger and Ross 1971;Cordey 1996;Orchard et al 2001). These faunas are akin to those today in eastern, southeastern and central Asia and probably lived far out in Panthalassa, and in Paleotethys and Tethys oceans.…”

“…Both the Bridge River and Cache Creek terranes are considered to be remnants of the floor of Panthalassa (Cordey et al 1992;Cordey and Schiarizza 1993;Cordey 1996;Orchard et al 2001). In southern British Columbia they are separated from one another by rocks of the TyaughtonMethow basin and Cenozoic volcanic rocks and by the Yalakom and FraserStraight Creek faults, but father north the Cache Creek lies entirely within the Intermontane superterrane, sandwiched between Stikinia and Quesnellia (Figs.…”

Early Triassic peritidal carbonate sedimentation on a Panthalassan seamount: the Jesmond succession, Cache Creek Terrane, British Columbia, Canada

“…1; Gabrielse et al 1991). As a whole, the Cache Creek Terrane comprises an oceanic assemblage containing Mississippian to Upper Triassic carbonates, Pennsylvanian to Jurassic radiolarian ribbonchert and basaltic rocks, and Permian to Middle Jurassic mudstone and graywacke, along with ultramafic rocks and blueschist Struik et al 2001;Orchard et al 2001). All the terrane rocks have been severely sheared and contorted, and their stratigraphic continuity is commonly disrupted.…”