Mississippian Ocean Island Basalts from the Western Palaeo-Pacific Ocean in the Cache Creek Terrane of British Columbia

Abstract

The Cache Creek terrane of the North American Cordillera comprises a subduction melange of limestone and basalt (Monger 1977). Separating accreted terranes which originated marginal to the continent (Eastern Assemblage and Greater Stikinia from fragments of Gondwana in the Greater Wrangellia composite terrane (Fig. 1), it is the only Cordilleran remnant of a basin the entire width of the Paleo-Pacific Ocean. The strata represent a series of ocean islands and fringing reefs which collided with North America in the Late Triassic (Monger 1977). Tethyan faunas indicate an equatorial western Pacific position from the Mississippian to Permian, with the implication that the origin of the islands is related to events along the eastern margin of Gondwana.