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| Format: | Artículo científico |
| Language: | en |
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Universitat de Barcelona
2007
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| Online Access: | https://www.redalyc.org/articulo.oa?id=50550201 |
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Table of Contents:
- The parautochthonous Gondwanan origin of the Cuyania (greater Precordillera) terrane of Argentina: A re-evaluation of evidence used to support an allochthonous Laurentian origin S.C. Finney Ciencias de la Tierra Pb Cuyania Cambrian Argentina Ordovician A substantial, diverse body of evidence has been interpreted as suggesting that the Cuyania terrane of northwesternArgentina, which includes the Argentine Precordillera, rifted from the Ouachita embayment of Laurentia in the EarlyCambrian, drifted across the Iapetus ocean as a microcontinent, and docked with the proto-Andean margin of Gondwanain the Mid to Late Ordovician. This is the so-called Laurentian microcontinent model. However, several lines ofevidence (basement age and affinity, stratigraphic, paleomagnetic and paleobiogeographical records) also point to aparautochthonous origin of this terrane. In this parautochthonous model, Cuyania migrated along a transform faultfrom a position on the southern margin of West Gondwana (present coordinates) in the Mid Ordovician to its modernposition outboard of the Famatina magmatic belt in Devonian time. With regard to basement age and characteristics,recently acquired U-Pb geochronology of detrital zircons from Cambrian and Ordovician sandstones and of zirconsfrom igneous clasts in an Ordovician conglomerate are difficult to explain with the Laurentian model and indicate,instead, a Gondwanan origin of the Cuyania terrane. Furthermore, potential basement rocks of Cuyania of Neoproterozoicto Early Cambrian age and Early Mesoproterozoic age are characteristic of Gondwana, rather than Laurentia.Pb isotopic ratios of Grenvillian-age basement rocks are not only similar to those of Grenvillian basement in Laurentiabut also to those in other areas of West Gondwana. In terms of the stratigraphic record, the similarity of the Cambrian-Ordovician carbonate platform succession of Cuyania to that of Laurentia reflects similar paleolatitude andeustatic histories but not a direct connection. Moreover, the Middle-Upper Ordovician siliciclastic successions ofCuyania do not represent a peripheral foreland basin, but instead were deposited in strike-slip related basins in a transformfault zone. Middle Ordovician K-bentonites do not indicate that Cuyania was approaching the Famatina magmaticarc from the west (modern coordinates), but instead that it was located to the southeast. In light of paleomagneticdata, the Cambrian paleolatitude of Cuyania is consistent not only with the location of the Ouachita embayment ofLaurentia but also with the southern margin of West Gondwana. Finally, most of the paleobiogeographic criteria usedto support the Laurentian model must be reconsidered. Brachiopod and conodont faunas in lower Middle Ordovicianstrata of the Precordillera have many more genera in common with Laurentia than those in Lower Ordovician strata.Cambrian trilobites faunas of Cuyania are of very limited abundance and diversity in comparison to correlative faunasof southeastern Laurentia; many species are endemic to Cuyania; olenellid trilobites considered to be restricted toLaurentia probably had the ability to disperse between paleoplates with similar environments. Mid 2007 artículo científico 1695-6133 https://www.redalyc.org/articulo.oa?id=50550201 en http://www.redalyc.org/revista.oa?id=505 Geologica Acta: an international earth science journal application/pdf Universitat de Barcelona Geologica Acta: an international earth science journal (España) Num.2 Vol.5