Geochemistry of the Mesozoic bedded cherts of Central Baja California (Vizcaino-Cedros-San Benito): implications for paleogeographic reconstruction of an old oceanic basin |
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| Authors: | Claude Rangin Michel Steinberg Chantal Bonnot-Courtois |
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| Institution: | Laboratoire de Géologie Structurale, LA 215, UniversitéPierre et Marie Curie, 4 place Jussieu, 75230 Paris Cédex 05France;Laboratoire de Géochimie des Roches Sédimentaires, ERA 765, Ba?t. 504, UniversitéParis-Sud, 91405 Orsay CédexFrance |
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| Abstract: | In central Baja California (Vizcaino Peninsula, and Cedros and San Benito Islands) two distinct radiolarian bedded chert sequences of late Triassic and late Jurassic/lowermost Cretaceous age, can be differentiated on lithostratigraphic and geochemical criteria.These bedded chert sequences are part of the conformable sedimentary cover of more or less dismembered ophiolites, which are overthrusted by the San Andrès-Cedros volcanic arc system of middle late Jurassic age.Major and trace elements permit paleogeographic zonation of the late Jurassic/lowermost Cretaceous radiolarites lying conformably upon ophiolites considered as fragments of an oceanic basin floor which developed westward of the San Andrès volcanic arc. Progressive accretion of this oceanic basin floor, along the continental margin is supported by the fact that the more distal radiolarian chert sequences belong to the lowermost structural units of this area. |
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