Pre-Carboniferous Tectonostratigraphic Subdivisions of Cape Breton Island, Nova Scotia
DOI:
https://doi.org/10.4138/1610Abstract
Cape Breton Island can be divided Into four zones on the basis of contrasting stratigraphy, metamorphism, and plutonism. A Southeastern zone Is characterized by late Precambrian volcanism and plutonism, followed by Cambro-Ordovlclan rift-basin sedimentation and minor volcanism. The Bras d'Or zone to the northwest Is underlain by gneissic basement and overlying platforms! (carbonate and clastic) sedimentary rocks. Intruded by mainly late Precambrian and Ordovician(?) granitoid rocks. The Highlands zone has a gneissic core flanked by typically lower grade sedimentary and volcanic rocks of probable Precambrian age intruded by diverse and abundant dioritic to granitic plutons ranging In age from Precambrian to Carboniferous. The Northwestern Highlands zone has gneissic basement Intruded by varied plutonlc rocks Including anorthosite and syenite, the latter of Grenvillian age. The nature and significance of the boundaries between these zones are as yet uncertain, but only the Southeastern and Bras d'Or zones are considered to be part of the Avalon Terrane. RÉSUMÉ Des contrastes de stratigraphie métamorphlsme et plutonIsme permettent de dIviser l'ile du Cap-Breton en quatre zones. Un zone sud-est se distinque par tin volcanisme et un plutonisme tardi-précambriens auzquels succedent, au Cambro-Ordovlcien, une sédimentation basslnale de type rift et un faible volcanisme. Au Nord-Ouest, la zone de Bras d'Or comporte un socle gneissique sur lequel s’est effectuée une sédimentation nèritique (terrigຘne et à carbonates). le tout injectè de granitoides prlnclpalement tardi-précambriens et ordovlciens(?). La zone de Highlands englobe un noyau gneissique ceinture de roches sédimentalres et volcaniques auzquels s'est typiquement imprimé un métamorphisme de faible intensité et qui sont probablement d'âge précambrien. Ceuz-ci sont tous recoupés par d'abondants plutons dioritiques et granitiques divers dont l'âge s'écbelonne du Précambrien au Caronifère. La zone de Northwestern Highlands renferme un socle de gneiss recoupé par diverses roches plutoniques dont l'anorthosite et la syenite, cette dernière étant d'âge grenvillen. Le doute subsiste encore en ce qui regarde la nature et la signification des frontières entre ces zones; cependant seules la zone sud-est et la zone de Bras d'Or sont conslderées comme appartenant à la lanière d'Avalon. [Traduit par le journal]Downloads
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