Upper Paleozoic to Jurassic accretionary complex of the Cache Creek Terrane, central British Columbia

International audienceUpper Paleozoic to Lower Jurassic oceanic rocks of the Cache Creek Terrane near Fort St. lames, in central British Columbia, form a semi-organized thrust imbricated complex cut by steeply dipping striking faults. The terrane consists of Tezzeron succession, Cache Creek Complex and Sitlika Assemblage. Tezzeron succession and lhe sedimentary rocks of the Sitlika assemblage appear to be derived from trench fill sediments wilh a volcanic arc provenance during the Upper Triassic to Lower Jurassic. Cache Creek Complex and the volcanic rocks of Sitlika assemblage were derived from an ocean plate active from Late Carboniferous to Early Jurassic time. The floor of the present accretionary complex consists mainly of Permian to Lower Jurassic greywacke, ribbon cbert and minor limestone. Onto these rocks are thrust ophiolitic successions, ocean island and plateau ultramafite, basalt, and limestone, and mixed arc and oceanic basalt. Some of these units are thrust onto trench fill sequences of the Tezzcron and Sitlika. Unlike a mélange, these thrust sheets have some regional consistency and form orogen parallel belts wilhin the Cache Creek Terrane. In the eastern part of the complex, Triassic blueschist metamorphic rocks appear to form thrust slivers within the regionally lower parts of the complex that include the trench fill successions. These thrust sheet units were amalgamated prior to 165 Ma, as they are truncated by plutons of that age. They must have formed at least in part after the youngest of the sedimentary successions. Toarcian (-190Ma) and incorporate subduction generated blueschist wedges of Triassic age