Biostratigraphy of the lower Ordovician Chitinozoa of Western Newfoundland, Canada

Batten, Randy S. R. (2000) Biostratigraphy of the lower Ordovician Chitinozoa of Western Newfoundland, Canada. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Cow Head Group of western Newfoundland, lying exposed within shoreline sections between Bonne Bay and Portland Creek, represents an allochthonous sediment apron or toe deposit at the base of an ancient carbonate-rich continental margin. While it has been studied extensively for a variety of fossil species, few accounts exist for chitinozoa in this stratigraphically important section. For this study, a detailed analysis of samples from 6 sections across the Lower Ordovician Cow Head Group recovered 32 species of well-preserved chitinozoan. In addition, 22 taxa of uncertain specific designation have been identified which represent 9 genera (Amphorachitina, Belonechitina, Conochitina, Desmochitina, Eremochitina, Lagenochitina, Laufeldochitina, Rhabdochitina, and Tanuchitina), and include several species that have never been documented firom western Newfoundland. -- Frequent occurrence of biostratigraphically useful species (Amphorachitina conifundas, Conochitina brevis, Conochitina langei, Conochitina raymondi, Conochitina symmetrica, Lagenochitina esthonica and Lagenochitina destombesi) indicate 4 Lower Ordovician chitinozoan biozones (Amphorachitina conifundas Zone, Conochitina symmetrica Zone, Lagenochitina esthonica / Conochitina raymondi Zone, Conochitina langei / Conochitina brevis Zone), and 2 proposed biozones {Cyathochitina dispar Zone, Laufeldochitina sp. Zone) that are unique to Newfoundland. Together, these zones span the upper Tremadoc through the entire Arenig, and correlate well with equivalent sections from North America, Europe, north Africa and Australia. While Amphorachitina conifundas and Lagenochitina destombesi have not previously been reported within North American sections, their persistence in western Newfoundland establishes a strong affinity between Laurentian and Gondwanan sections that has not been documented within eastern Canada. -- A preliminary investigation of species distribution suggests a number of taxa (Conochitina, Rhabdochitina and Lagenochitina spp.) may show preference for either shallow (proximal) or deep water (distal) deposits along the lower carbonate slope of the Cow Head Group. Whether this reflects either physical reworking and sediment transport, or the result of ecological influences is largely speculative. From the present study it is clear that the distributional controls on chitinozoa within the Cow Head Group are indeed complex, and likely influenced by an array of sedimentological and biological processes.

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