Conodonts of the Table Head Formation (Middle Ordovician), western Newfoundland

Stouge, Svend (1980) Conodonts of the Table Head Formation (Middle Ordovician), western Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

On the Great Northern Peninsula, western Newfoundland, the transqressive Table Head Formation (Middle Ordovician) overlies the Lower Ordovician St. George Group. The Table Head strata are overlain by carbonate breccias and easterly derived flysch deposits. The Table Head sediments include limestones, mainly rubbly, with dolostones at the base (lower Table Head), overlain by limestones interbedded with shales (middle Table Head) and black graptolitiferous shales at the top (upper Table Head). The lower Table Head limestones represent the last platform carbonate deposit before the bank foundered probably due to the emplacement of Lower Ordovician allochthons in western Newfoundland. -- The formation has been studied in detail from eight localities in the area from Bellburns community in the south to St. John Island in the north. Additional information from localities on Port au Port Peninsula and Hare Bay is included. The Table Head sediments all along on the west coast of Newfoundland compare with those in the study area. The thickness of the different units varies considerably and reaches its maximum at Table Point. The detailed investigation of the rocks revealed that carbonate accumulation was interrupted by "catastrophic" downwarps of the shelf. These may be related to the emplacement of the allochthons. -- A total of approximately 17,000 conodonts was recorded within the study area. An additional 3,000 were recorded from elsewhere in western Newfoundland. The conodont fauna is described in multi-element taxonomy, and a supragenetic classification is applied. 35 genera and Panderodontidae, and the new recognized family Cornuodontidae n. fam.. -- Two phylo-zones and four biointerval-zones are defined. The phylo-zones are based on phylogenetically related and facies independent species of Histiodella. The species from the basal lower Table Head on Newfoundland belong to Midcontinent Fauna 4, and are correlative with strata from North America. The conodonts reinforce trilobite and cephalopod data that indicate a late Whiterockian (early Llanvirnian age for these strata. The North Atlantic Province conodonts from the middle Table Head have a number of species in common with the Eoplacognathus suecicus Zone of Scandinavia. The top of the middle Table Head at Table Point may be as young as the E. suecicus-P. sulcatus Subzone. -- The Table Head strata accumulated in lagoonal, shelf (inner-outer) and slope environments. The lateral distribution of conodonts can be directly related to these depositional environments, and a sequence of three biofacies and sub-biofacies is introduced. The lagoonal (Midcontinent Province) and slope (North Atlantic Province) biofacies are distinct, whereas the shelf biofacies is less distinct. The occurrence of occasional invaders from the open oceanic biofacies can be related to the oscillating transgression.

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