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Faunal and stratigrgraphic study of Upper Paleozoic rocks of Vancouver Island, British Columbia Yole, Raymond William

Abstract

Paleozoic rocks of Vancouver Island are exposed in three major belts: the China Creek-Saltspring, the Home Lake-Cameron River, and the Buttle Lake-Big Interior belts. Stratigraphic sequences in these three belts are grossly similar, though differing in detail. The Paleozoic rocks of each belt are correlated with the Sicker Group, originally defined in the southern part of the China Creek-Saltspring belt. Within the Sicker Group, two major lithological units are recognized, and are referred to as the Lower and Upper Divisions of the group. The base of the Sicker Group has not been seen. The upper contact of the group appears to be anpaunconformity, above which Upper Triassic volcanic and sedimentary rocks of the Vancouver Group occur. The Lower Division consists mainly of volcanic rocks and non-calcareous clastic rocks. In the Upper Division, limestones and thin-bedded cherty sediments predominate. The major unit within the Upper Division of the Buttle Lake-Big Interior belt is a limestone formation (named herein) of 1000 to 1100 feet maximum thickness. Thin-bedded, fine-grained non-calcareous rocks of unknown age, tentatively included within the Sicker Group Upper Division, conformably overlie the limestone at certain localities. A rich fauna of brachiopods, bryozoans, molluscs, corals and foraminifers has been found in the Upper Division. A meagre flora of algae and fragments of vascular plants is present in a locally-developed basal sandstone of the Upper Division. At least 42 genera, represented by 52 species, have been recognized in the Upper Division fauna; many fossils remain to be identified. Four of the brachiopod species are regarded as new. Faunas similar to that of the Upper Division of the Sicker Group have been listed or described from other northern Cordilleran regions. Correlation is thus suggested with the Permian Coyote Butte Formation of central Oregon, the Black Mountain Formation of northwestern Washington, part of the Cache Creek Group of mainland British Columbia, and parts of the Permo-Carboniferous successions of Alaska and Yukon Territory. Permian faunas of the Arctic Archipelago, Greenland, Spitsbergen and northwestern Russia contain many genera and some species in common with the fauna of the Sicker Group. Species of Hor-ridonia, Spiriferella and Kochiproductus are particularly significant in this regard, linking the Sicker Group fauna with the "Arctic Permian" and "Russian" boreal faunas. Despite the strong boreal affinities of the Vancouver Island fauna, however, relationships also with western Pacific equatorial faunas are suggested by certain brachio-pods and many of the bryozoans. The faunal relationships thus established, and the presence of certain diagnostic brachiopods and tentatively identified fusulinids, indicate the age of the Upper Division of the Sicker Group to be Early Permian (Wolfcampian-Leonardian). The evident mixing in the Permian fauna of Vancouver Island of elements of boreal and equatorial faunas prohibits conclusive bio-geographic analysis at the present stage of investigation. The present evidence of faunal distributions is also inconclusive with respect to the assessment of theories of continental drift and polar wandering. Lower Division rocks represent deposits of a moderately deep gulf or basin on the continental borderland, formed during a period marked by tectonic and volcanic activity. Diminishing crustal unrest culminated in the shoaling waters and carbonate deposits characteristic of the Upper Division.

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