Brachiopod biostratigraphy of the middle Ordovician Cow Head and Table Head groups, western Newfoundland

Brachiopods from shallow-water limestone boulders in beds 12, 13, and 14 of the allochthonous Cow Head Group belong in the earliest Whiterockian Orthidiella Zone. Brachiopods of the autochthonous intertidal to deep-water Table Head Group are equivalent to those of the younger Whiterockian Anomalorthis Zone. The Cow Head is older than the Table Head.Integration of the brachiopod data from western Newfoundland with those from the type Whiterockian in Nevada, combined with the evidence of graptolites from both areas, indicates that the Orthidiella Zone spans the Australian Castlemainian, Yapeenian, and lower Darriwilian Dal zones.