Imbricate architecture of the upper Paleozoic to Jurassic oceanic Cache Creek Terrane, central British Columbia

Abstract

Upper Paleozoic to Lower Jurassic oceanic rocks of the Cache Creek Terrane near Fort St. James, in central British Columbia, form a stack of thrust sheets cut by steeply dipping strike-slip faults. Paleontologically dated upper Paleozoic strata include bioclastic shallow-water limestone and ribbon chert. Isotopically dated Permian rocks consist of tonalite sills and stocks and rhyolite flows intercalated with basalt flows. Paleontologically dated lower Mesozoic rocks include greywacke, sandstone, siltstone, argillite, ribbon chert, conglomerate, limestone, and basalt tuff. Trembleur Ultramafite unit of the Cache Creek Complex, in places part of an ophiolite suite, forms thrust sheets and klippen that overlie lower Mesozoic sedimentary rocks. Sedimentological, lithochemical, paleontological, petrological, and textural comparisons with other areas and established models demonstrate that Cache Creek Terrane is an accretionary complex, a structurally stacked assemblage of rocks that originated in diverse and disparate oceanic paleoenvironments. These environments include spreading ridge, oceanic plateau, atoll, trench fill, and possibly arc. Internal imbrication of the terrane is as young as Early Jurassic, as determined from fossil evidence, and the minimum age of obduction of the thrust stack westward onto Stikine Terrane is Middle Jurassic, as determined from dating of a crosscutting pluton. Triassic blueschist and eclogite of Cache Creek Terrane are interpreted to have been primarily uplifted to upper crustal levels during Triassic subduction. Cache Creek Terrane, as a remnant of that subduction process, and caught in the collision between Stikine and Quesnel terranes, marks the position of a lithosphere-scale suture zone, the Pinchi Suture.

Timing of Cache Creek Ocean closure: insights from new Jurassic radiolarian ages in British Columbia and Yukon and their significance for Canadian Cordillera tectonics

“…Within the Tezzeron succession, a limy siltstone unit located near the south end of Pinchi Lake contains an Early Jurassic radiolarian assemblage (J4, Fig. 2, Table 1) previously reported by Orchard et al (2001) and Struik et al (2001). It is composed of Emiluvia?…”

Necoslie breccia: mixed conodont fauna-bearing neptunian dyke in Carboniferous-Permian seamount-capping oceanic buildup (Pope succession, Cache Creek Complex, central British Columbia)

“…The sand-sized sparite particles are mostly comminuted crinoid debris and lithic fragments of limestone of uncertain affinity. It is noted that no limestone-type which correlates lithologically with the matrix-forming clastic limestone is documented throughout the entire Pope succession , or in the lower to upper Middle Permian Copley limestone and or in the lower Upper Permian to lower Middle Triassic Kloch Lake succession Struik et al 2001).…”

“…The Cache Creek Complex of central British Columbia is subdivided into the seven units The Pope succession consists predominantly of Bashkirian to Asselian shallow-marine limestone and a minor amount extent of ribbon-bedded chert, and basaltic breccia and volcaniclastic rocks Struik et al 2001). The rocks of the Pope succession are defined as an oceanic rock assemblage, totally devoid of land-derived clastic grains.…”

“…Thick line with tooth in map A denotes eastern limit of Cordilleran deformation, and P, J, and S in map B represent Mt.Pope, Fort St. James, and Spad Lake, respectively. Base maps both for A and B afterStruik et al (2001).…”

The northern termination of the Cache Creek terrane in Yukon: Middle Triassic arc activity and Jurassic–Cretaceous structural imbrication

“…The Intermontane terranes consist of mid-Paleozoic to early Mesozoic arc terranes (Yukon-Tanana, Stikinia, and Quesnellia) that developed in the peri-Laurentian realm (Nelson et al 2013), and the Cache Creek terrane, which formed as an accretionary complex in the forearc region of Stikinia and Quesnellia (Fig. 1, inset;Monger and Nokleberg 1996;Struik et al 2001). The Cache Creek terrane consists of fragments of oceanic crust, seamounts with limestone caps, arc crust, supra-subduction zone ophiolite, pelagic sedimentary rocks, and is overlain by synorogenic clastic Final version published as: Bickerton, L., Colpron, M., Gibson, H. D., Thorkelson, D., & Crowley, J. L. (2020).…”