Resumo

BORDONARO, Osvaldo L. Trilobites laurénticos de la Formación La Laja (Cámbrico), Precordillera de San Juan, Argentina: un aporte biogeográfico al modelo alóctono de Precordillera. Rev. Asoc. Geol. Argent. [online]. 2016, vol.73, n.4, pp.457-467. ISSN 0004-4822.

The biogeographic distribution of 14 laurentian ptychoparioid trilobite of the La Laja Formation, Middle Cambrian (Series 3) from the San Juan Precordillera, western Argentina is analyzed. The trilobites were endemic Laurentian species with restricted access to open oceans that inhabited the inner parts of the carbonate platform that rimmed the North American craton. Its presence in the restricted carbonatic platform of the Argentine Precordillera and its absence in the carbonatic facies of East Gondwana, particularly in Antarctica - Australia, are incompatible with dispersal by oceanic equatorial currents across an Iapetus open ocean in a Cuyania para- autochthonous gondwanan model. Instead, it is compatible with peri-laurentian dispersion in an allochthonous laurentian model, but only if Cuyania was environmentally connected to southern Laurentia. A modified allochthonous Laurentian model where the northern Cuyania is physically and environmentally connected to the southern Appalachians is proposed to explain the dispersion of endemic faunas without having to cross an open ocean.

Palavras-chave : Biogeography; Trilobites; Cambrian; Precordillera; Argentina.

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