Stratigraphy and palaeontology of the Ordovician Long Point Formation, Port au Port Peninsula, Newfoundland

Weerasinghe, Asoka (1970) Stratigraphy and palaeontology of the Ordovician Long Point Formation, Port au Port Peninsula, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Long Point Formation is present in the north-western part of the Port au Port Peninsula, western Newfoundland. It derives its name from Long Point, a northeastward dagger-like extension of the Peninsula fourteen miles in length. The Formation consists of fossiliferous limestones, sandstones and shales that are well exposed in the coastal cliffs on both sides of Long Point. This thesis presents the results of a study of the stratigraphy and palaeontology of the strata underlying the northern half of Long Point. -- On Long Point, beds of the Long Point Formation strike northeast and dip towards the northwest; the dip decreases from 54 degrees at the southern end of the thesis area to less than 10 degrees at the northern end. The beds are little disturbed by the few minor faults present. -- The Long Point Formation has been divided by the writer and two other graduate students from Memorial University working in adjoining areas into eight members, the names of which are taken from their type localities. The members from oldest to youngest are: Tea Cove, Shorepoint, Portage, Black Duck, LeRoy, Beachpoint, Misty Cove and Lourdes. Only those underlined are represented in the thesis area. The lithology of these members is as follows: Black Duck - grey limestones with occasional shaly partings and some argillaceous beds; LeRoy - blue-grey crystalline limestones with shaly partings; Beachpoint - grey, knobbly limestone interbedded with blue shale; Misty Cove - calcareous sandstone interbedded with blue shale. -- The fossil fauna of the Formation as a whole includes brachiopods, bryozoa, crinoids, gastropods, graptolites, ostracodes, scolecodonts, stromatoporoids, tabulate corals and trilobites. Their relationship to particular members is described and an account is given of all the brachiopods and trilobites collected. Of the other groups present, only the more obvious or common representatives have been described. These include one particularly important form, the tabulate coral Labyrinthites chidlensis which has given rise to small columnar reefs in the Black Duck member. The nature of these reefs and other significant, mainly ecological, aspects of the fauna are discussed. -- Details are given of the stratigraphy of the Long Point Formation. The main part of the succession represents the deposits laid down in a transgressive sea. Marine sedimentation was brought to a close by uplift and the nature of the uppermost beds indicates a change in environmental conditions from marine to deltaic or terrestrial. -- Fossil evidence indicates that the strata of the Long Point Formation probably range from upper Middle Ordovician to lower Upper Ordovician in age. (Upper Wilderness to Upper Barneveld Stages).

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