The geologic development of the Bay d'Espoir area, southeastern Newfoundland

Colman-Sadd, S. P. (1974) The geologic development of the Bay d'Espoir area, southeastern Newfoundland. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Bay d'Espoir on the south coast of Newfoundland exposes a section across the southeastern marginal metamorphic belt of the Newfoundland Appalachians. Two major tectonostratigraphic divisions are recognized; in the south the Little Passage Gneisses of the older division (probably Precambrian), consisting of amphibolitic and psammitic gneisses intruded by tonalite, are overlain by metavolcanic and metasedimentary cover rocks of the younger division, the Baie d'Espoir Group (possibly Ordovician). The Little Passage Gneisses have been intruded post-tectonically by a megacrystic potash feldspar granite. Both this granite and the enclosing gneisses are extensively mylonitised and reconstituted close to the contact with the cover rocks and the gneissic foliations have been largely destroyed. -- The Baie d'Espoir Group has undergone two, regionally penetrative deformations, the second of which has produced a major recumbent south-east facing anticline, the Bay d'Espoir Nappe. These deformations are the cause of the mylonitised and reconstituted zone along the contact with the Little Passage Gneisses. Garnetiferous leucocratic granite and associated aplites and pegmatites have intruded the Little Passage Gneisses, the megacrystic granite, and the Baie d'Espoir Group after its first deformation but before its second; the intrusion coincided with the metamorphic climax of the Baie d'Espoir Group. Sheets of this garnetiferous granite have been tightly folded with the reconstituted gneisses near the contact with the cover. -- It is concluded that the gneisses form the basement to the Baie d'Espoir Group and that the contact is now tectonic. Deposition of the Baie d'Espoir Group was along a continental margin which was initially of Atlantic-type but later changed to Andean-type. Deformation was probably caused by continental collision along the line of the Cape Ray Fault and the Lower Palaeozoic outcrop of central Newfoundland. Correlations with similar rocks in the Gander region, central Newfoundland, on the southwest coast of Newfoundland, and in Nova Scotia are proposed.

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