Abstract

Ten samples from a 160 m section through the lower Whittaker Formation yielded Red River Province conodonts as well as a shelly macrofossil assemblage representing the "Arctic Ordovician fauna." Both the microfossils and macrofossils have strong affinities with taxa represented in strata of Cincinnatian age in the western Midcontinent Province of North America.Conodont-based graphic correlation of section W-1 with a Composite Standard Section developed for midcontinental United States indicates that the lower Whittaker Formation on the east flank of the Redstone Arch represents nearly the entire Cincinnatian Series. Trilobites of the Ceraurus mackenziensis Zone occur in strata correlative with the upper Edenian and those of the Whittakerites planatus Zone first appear at or just below the projected base of the Maysvillian Stage. The age of the Ceraurinella necra Zone is still uncertain but is likely to be early Edenian.Thaerodonta recedens (Sardeson) and other elements of the BighorniaThaerodonta fauna also debut in uppermost Edenian or lowermost Maysvillian strata. The morphology of Sowerbyella redstonensis n.sp. and Thaerodonta recedens from the lower Whittaker Formation indicates that the common ancestor of early Thaerodonta species may have arisen during latest Edenian time. The first appearance of Thaerodonta may constitute a useful biostratigraphic datum throughout the Red River Province. The strongly Thaerodonta-like species, Sowerbyella redstonensis n.sp., is described from silicified material of mid-Edenian age.

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