The Ediacaran-Cambrian Apparent Polar Wander Path for the Río de la Plata craton: implications for the assembly of Western Gondwana

AUGUSTO RAPALINI; LEDA SÁNCHEZ BETUCCI; RICARDO TRINDADE; DANIEL POIRÉ; DANIEL RICHARTE; ANA LOSSADA; ERIC TOHVER

Congreso; Meeting of the Americas 2010; 2010

American Geophysical Union

st1:*{behavior:url(#ieooui) } The assembly of Gondwana in the Late Proterozoic to Early Paleozoic was a fundamental paleogeographic and tectonic process that had deep implications for the geologic, climatic and biologic evolution of the Earth. Multidisciplinary data gathered in the last two decades have significantly advanced our knowledge of the assembly of this supercontinent and a view of a protracted and complex process is widely accepted. Unraveling the kinematics of this event relies heavily on precise and reliable paleomagnetic data. To fulfill this requirement is a daunting task since ideally independent Late Proterozoic apparent polar wander paths should be obtained for each of the dozens of crustal blocks that may have had an independent kinematic history before Gondwana amalgamation. In the last two decades a slow but steady increase in number and quality of Proterozoic paleomagnetic data has been evident. On this basis some partial tests of different paleogeographic reconstructions have been performed putting constraints on the different tectonic models under consideration. The available paleomagnetic database for the Río de La Plata (RP) craton for the Ediacaran-Cambrian interval is presented and compared with coeval data from other Gondwana blocks. Twelve paleomagnetic pole positions define a broad apparent polar wander path (APWP) for this craton for the 600-500 Ma interval. The available data suggest a long APWP, but with the craton remaining at intermediate to low latitudes throughout the whole time span. Comparison with recent data from the Congo-Sao Francisco (CSF) craton suggests that both blocks were already a single plate by ca. 575 Ma. Models that propose these two cratons attached to Laurentia during this time interval are not supported by the paleomagnetic database. Consistency with poles from Australia and Arabia from ca. 540 Ma suggests that for those times large parts of Gondwana were already assembled. However, doubts concerning the relationship between the Kalahari and Amazonia cratons with RP-CSF have not been answered yet. A single pole from Amazonia older than 600 Ma suggests a a paleogeographic separation from the RP, while by ca. 525 Ma both blocks were already together. Scarce data from Kalahari hamper any significant conclusion, although an Early Cambrian amalgamation of this craton cannot be ruled out on the basis of the available information. Provenence of the Pampia and Antofalla blocks as a fragment of Kalahari can augment the scarce Cambrian paleomagnetic data from these terranes.