Abstract

Stratigraphic sections were measured in the very complete coastal exposures around Port-au-Choix village in western Newfoundland. A formal stratigraphic subdivision of the Ordovician St. George Group into three formations is proposed. They are, from oldest to youngest: the Barbace Point Formation, a 21 + m thick unit of dense dolostone, showing diagenetic solution features; the Catoche Formation, 100 m thick, consisting of well bedded limestones with shallow-water indications; the Port-au-Choix Formation, 35 m thick, massive sugary dolostones grading into silty dolostones, with diagenetic solution features. Detailed descriptions of all new formations are given, as well as the rationale behind this new nomenclature. The Early Ordovician depositional history of the area is seen as a succession of two erosional and depositional cycles, not completely preserved in the record, whereby the Barbace Point Formation was subjected to subaerial erosion, creating a hiatus between this formation and the overlying Catoche Formation; the latter represents the beginning of a new depositional cycle which was possibly interrupted before the youngest Port-au-Choix Formation was deposited. After Port-au-Choix times, renewed erosion took place before the Table Head Group was formed.

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