Radiolarian occurrences, Canadian Cordillera

Radiolarian investigations linked to geological mapping in the Canadian Cordillera has led to generate an important database with extended geographic and chronologic ranges (Table). Within the Cordillera, radiolarians are known so far from the Ordovician to the Cretaceous (radiolarians lived from Cambrian to the present). In Mesozoic time, marine terranes accreted to the North American margin contain large quantities of radiolarian-bearing rocks, such as the Cache Creek terrane which crops out over 1500 km along the Cordillera from Southern British Columbia to the Yukon (see map). These results (Cordey, 1998) show the age-younging of accreted oceanic basin towards the W in relation to the progressive amalgamation of terranes along the North-American margin during the Phanerozoic, supporting the process of continental accretion.



In southern British Columbia, the Bridge River terrane (Table and Map) contains radiolarian chert ranging in age from Early Carboniferous to Middle/Late Jurassic, or nearly 200 million years. This is one of the longest accumulation of radiolarian chert known in the world; it provides evidence for the long lifespan of proto-Pacific ocean basins, and therefore of potentially immense areas of oceanic crust that must have disappeared by subduction beneath the North American continent in Paleozoic and Mesozoic times.


Location map from: "Long-lived Panthalassic remnant: the Bridge River accretionary complex, Canadian Cordillera, by F. Cordey and P. Schiarizza, Geology, 1993, v. 21, p. 263-266". Radiolarian localities range in age from Early Carboniferous to Middle Jurassic.