PALEOMAGNETIC CONSTRAINTS ON THE ORIGIN OF PATAGONIA: WHERE DO WE STAND TODAY

RAPALINI, AUGUSTO E.; MARTÍNEZ DOPICO, CARMEN; LÓPEZ DE LUCHI, MÓNICA; ANTONIO, PAUL; FRANCESCHINIS, PABLO R.

Río de Janeiro

Congreso; LatinMag VII Biennal Meeting; 2023

Asociación Latinoamericana de Paleomagnetismo y Geomagnetismo

After four decades of investigations and disputes, whether Patagonia is anautochthonous block to Gondwana or collided against this megacontinent margin atsome time during the Paleozoic is still a matter of controversy. Since the early 1990´spaleomagnetic studies have been carried out on Paleozoic rocks exposed mainly in theNorth Patagonian Massif (NPM) to test these opposite models. However, progress hasbeen slow due to paucity of exposures of suitable rocks. Seven paleomagnetic poleswith ages ranging from the Late Ordovician to the Late Permian have been published.Some of them do not fulfill several of the accepted reliability criteria, while othersappear as more robust. A comparison of these pole positions with the referenceapparent polar wander path for Gondwana in the Paleozoic suggests that the NPM wasat paleolatitudes compatible with those corresponding to SW Gondwana since the LateOrdovician. This can be taken as evidence in favor of an autochthonous orpara-autochthonous origin of NPM with respect to Gondwana. A single paleomagneticpole of Late Carboniferous age that might represent a southern Patagonian block iscompatible with an allochthonous position near Eastern Antarctica, howeveruncertainties in age and position of the pole are large enough to turn any tectonicinterpretation inconclusive. A hypothetical location of the whole of Patagonia close tothe Transantarctic Mountains in the Cambrian cannot be tested with the availablepaleomagnetic data.