Assembly of Pampia to the SW Gondwana margin: A case of strike-slip docking?

SPAGNUOLO, CECILIA M.; RAPALINI, AUGUSTO E.; ASTINI, RICARDO A.

GONDWANA RESEARCH

ELSEVIER SCIENCE BV

Año: 2012 vol. 21 p. 406 - 421

1342-937X

Different hypotheses have been proposed to account for the geologic evolution of the southwestern margin ofGondwana in the Early Paleozoic, involving accretion and displacement of different terranes in a protractedconvergent margin. In order to constrain and understand the kinematic and paleogeographic evolution of thePampia terrane a paleomagnetic study was carried out in different Cambrian to Devonian units of the EasternCordillera (Cordillera Oriental) and the Interandean Zone (Interandino) of NW Argentina. Paleomagneticpoles from the Campanario Formation (Middle to Upper Cambrian): 1.5°N 1.9°E A95=9.2° K=37.46 N=8;and Santa Rosita Formation (Lower Ordovician): 8.6°N 355.3°E A95=10.1° K=26.78 n=9, representative ofthe Pampia terrane, are interpreted to indicate a Late Cambrian significant displacement with respect to theRío de la Plata and other Gondwana cratons. A model, compatible with several geological evidences thatexplains this displacement in the framework of the final stages of Gondwana assembly is presented. Wepropose a simple dextral strike-slip kinematic model in which Pampia and Antofalla (−Arequipa?) blocksmoved during Late Cambrian times from a position at the present southern border of the Kalahari craton intoits final position next to the Rio de la Plata craton by the Early Ordovician.