The evolution of tectonostratigraphic terranes in the southern Central Andes

Paleozoic geodynamic evolution and tectonostratigraphic terranes of northwestern Argentina and northern Chile

In the Ordovician, Gondwana in the area of northwestern Argentina and northern Chile had a west-facing active margin. The evolution of this margin culminated in the Oclóyic orogeny at the end of the Ordovician. An inspection of the available stratigraphical and geochronological data on sedimentary, volcanic and plutonic units of the southern Central Andes of northern Chile and NW Argentina reveals a lull in magmatic and metamorphic activity lasting for c. 100 Ma from the Early Silurian to the early Late Carboniferous. This is interpreted as corresponding to a tectonic scenario in which the present Andean margin was a passive margin of Gondwana. This passive margin developed after the Oclóyic orogeny due to an hitherto unexplained change in plate kinematics. The Late Carboniferous marks the renewed onset of subduction, initiating the Andean plate tectonic setting still prevailant today. The Early Paleozoic evolution of northwestern Argentina and northern Chile and the absence of allochthonous or even exotic terranes contrasts markedly with the accretionary history of central Argentina and central Chile where the Precordillera and Chilenia Terranes docked in the Late Ordovician and Late Devonian, respectively. Models explaining the Late Ordovician Oclóyic orogeny by the collision of Laurentia with western South America during Laurentia's clockwise motion around South America and away from its position in the Neoproterozoic supercontinent are difficult to reconcile with the Paleozoic tectonostratigraphic evolution of the southern Central Andean region.

Bahlburg, H., Hervé, F., Moya, M.C., Bock, B. and Zimmermann, U. (2000): Paleozoic plate tectonic evolution of the western Gondwana margin in northern Chile and northwestern Argentina.- Zeitschrift für Angewandte Geologie SH 1, 345-353.

Bahlburg, H. and Hervé, F. (1997): Paleozoic geodynamic evolution and tectonostratigraphic terranes of northwestern Argentina and northern Chile.- Geological Society of America Bulletin 109, 869-884.