Early Ordovician (Arenig) conodonts from St. Pauls Inlet and Martin Point, Cow Head Group, Western Newfoundland

• Main Author: Johnston, David Ian
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1986
• Subjects: Bradshaw; Cow Head; Green Point; Martin Point; Sergeeva; St. Pauls; St. Pauls Inlet; The Toe; Newfoundland
• Online Access: https://research.library.mun.ca/6841/; https://research.library.mun.ca/6841/1/DavidIanJohnston.pdf; https://research.library.mun.ca/6841/3/DavidIanJohnston.pdf

The Middle Cambrian to Middle Ordovician Cow Head Group, Newfoundland, was deposited at the toe-of-slope and continental rise of a passive margin adjacent to a carbonate platform. Early Ordovician (Arenig) strata are characterized by massive megaconglomerates interbedded with deep-water carbonates and siliciclastics and minor conglomerate. The St. Pauls Inlet and Martin Point sections are interpreted as intermediate and distal facies, respectively, of this sequence. Arenig strata in these and in other Cow Head sections of the St. Pauls Member of the Green Point Formation record the transition from a tectonically passive to a tectonically active margin. In the Middle Ordovician these rocks were thrust over coeval platform strata. -- Previous conodont investigations focused entirely on sections on the Cow Head Peninsula. This study is an investigation of the biostratigraphy, paleoecology, and the taxonomy of Arenig conodont faunas from bedded strata of both the St. Pauls Inlet and Martin Point sections.- Each section was measured and sampled intensively, with 3.5 kg. samples taken at approximately 1 m intervals. The majority of processed samples were limestones which were dissolved in 10-15% acetic acid, and then sieved, separated, and picked for conodonts. A total of 35.659 conodont elements were recovered from 64 limestone and shale samples. -- Apparatuses of Lenodus Sergeeva, Oistodella Bradshaw, and Spinodus Dzik are described. The occurrence of Oepikodus communis Ethington and Clark below the first occurrence of O. evae (Lindstrom) supports the hypothesis that these species belong to separate lineages. Morphologic evidence from Cow Head material supports the assignment of elements resembling 'Scolopodus' gracilis Ethington and Clark s.f. to monoelemental species of Parapanderodus Stouge. Periodon flabellum evolves gradually into Periodon aculeatus, with early, intermediate, and late forms of the latter species recognized. The triangulariform element of Protoprioniodus papiliosus van Wamel is recognized as ...