Time and Mechansim(s) of accretion of the Laurentia-derived Argentine Precordillers

  • Thomas, William (PI)

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The Precordillera in northwestern Argentina is an exotic Laurentian (North American) terrane that collided with and was accreted to western Gondwana (South America). General consensus holds that the Precordillera was rifted from the Ouachita embayment of southern Laurentia, and the Precordillera arguably has the best-constrained original location of any known exotic continental terrane. For that reason, the Precordillera provides a place to address fundamental questions of mechanisms and rates of transfer of a continental terrane from one continent to another. In addition, the Precordillera may serve as model for processes and responses that characterize the collision of a microcontinent (small plate) with a continent. Finally, the history of the transfer of the Precordillera from Laurentia to Gondwana is an important constraint on global paleogeographic reconstructions. Even with the consensus both for the original location of the Argentine Precordillera in the Ouachita embayment and for collision of the Precordillera with western Gondwana, interpretations of the time of collision differ from Middle-Late Ordovician to Silurian-Devonian. Middle-Late Ordovician events are recognized in each of the interpretations, but those events are considered to represent collision with Gondwana in some interpretations and to represent rifting from Laurentia in others. New data gathered in this research help to constrain both the timing and mechanism(s) of collision of the Precordillera with Gondwana. This research integrates the history of subsidence and sedimentary filling of the Precordillera foreland basin in the context of temporal and mechanical links to the Famatina volcanic arc and a continental suture zone between the rocks of western Gondwana and the eastern Precordillera. Specifically, the research is examining the subsidence history of the basin, role of high-relief fault blocks as sources of carbonate olistoliths, significance of possible fault blocks for extension or transpression/transtension, provenance of igneous and metamorphic clasts, patterns of clastic sediment dispersal on Precordillera platform, relation of Famatina arch and suture zone to basin subsidence and sediment progradation on platform, and relation of succession to southern Laurentia.
Effective start/end date3/1/032/28/07


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