Conodonts from the Cow Head Group, western Newfoundland

Nowlan, Godfrey S. (1973) Conodonts from the Cow Head Group, western Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

At its type section near the village of Cow Head on the Great Northern Peninsula, Newfoundland, the Cow Head Group consists of carbonate breccias, micrites, graded bioclastic limestones and non-calcareous shales with minor sandstones, shaly limestones and non-calcareous siltstones. Many of the limestones are laminated and bioturbated, and some are partially to completely dolomitised. The section is only 300m. thick and ranges in age from Middle Cambrian to Middle Ordovician. It was transported westward by gravity sliding during the Middle Ordovician and it now overlies shelf facies limestones. The sequence was carefully logged and sampled for conodonts in order to determine the existence and extent of conodont zones, and to define the transition between the Cambrian and Ordovician Systems in terms of conodont biostratigraphy. -- Yields of conodonts from the samples are generally sparse and the faunas are rarely diverse. The conodonts are classified using multielement taxonomy wherever possible, and those elements which do not fit into any known multielement species are listed under form taxonomy. -- The Cow Head Group is divided into 14 Units primarily on the basis of conodonts. No conodonts were recovered from the Middle Cambrian and thus it is correlated on the basis of previously reported trilobite faunas. Reasonable correlation can be made with the conodont zones of Balto-Scandia erected by Lindström and Bergström for the Lower Ordovician, however not all of these zones have been recognised. The zones erected by Lindström for the Volkhovian and Kundan Stages of the Baltic Shield (Baltoniodus triangularis Zone to the Amorphognathus variabilis Zone) are not recognised in the Cow Head sequence. Tentative correlations are likewise made with the Australian Lower Ordovician conodont zones. Only a very poor correlation of the Cow Head Group with the conodont zones of the mid-western United States exists, emphasising the difficulty of correlating cratonic and extra-cratonic conodont faunas. -- The Cow Head Group was deposited near the base of the Lower Paleozoic continental slope of eastern North America. It was laid down as a series of mass gravity slides which flowed from the outer shelf and upper slope into an area of active deposition and redistribution of thin carbonate and non-calcareous muds.

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