Uppermost Cambrian and Lower Ordovician acritarchs and Lower Ordovician Chitinozoans from Wilcox Pass, Alberta

Organic-walled microfossils from Wilcox Pass, in the southern Canadian Rocky Mountains, are described from 65I.9 m of mainly shallow water marine carbonate deposits belonging to the Survey Peak Formation, the Outram Formation, and the lowest 32 m of the Skoki Formation. Three new acritarch species are described: Acrum? jasperense, Aryballomorpha albertana, and Athabascaella sunwaptana. The species Corollasphaeridium wilcoxianum Martin in Dean and Martin, I982 is emended. Six acritarch-based units (microfloras AUI-AU6), the second of which is proposed formally as the Corollasphaeridium wilcoxianum Zone, contain badly to moderately well preserved material, and range from uppermost Upper Cambrian to Lower Ordovician. Poorly represented chitinozoans from the Arenig are grouped in one unit (microfauna CUI). Fossil age control is determined mainly on the basis of the trilobite succession. Palynological data extend from 0.9 m below strata dated as Corbinia apopsis Subzone of the Saukia Zone to 30.3 m above strata belonging to trilobite zone 1. In the lowest member of the Survey Peak Formation, two of the three conodont zones whose bases are being considered for defining the Cambrian-Ordovician systemic boundary are also used in dating. The C. wilcoxianum Zone, which is close to the Cambrian-Ordovician boundary, and microflora AU5b, from the upper Tremadoc, trilobite zones D toE, indicate correlation between the northern shelf of Laurentia and the northern border of the Sino-Korean platform, northeastern China. Two index acritarchs, Aryballomorpha grootaertii (Martin) emend. Martin and Yin, I988 and Athabascaella playjordii (Martin) emend. Martin and Yin, 1988 occur in the Lower Ordovician of Laurentia and northeastern China and of bland, Sweden, which was part of Baltica in the Ordovician.