HR: 15:30h
AN: GP34A-01 INVITED     [Abstracts]
TI: Paleomagnetic Constraints on the Neoproterozoic Evolution of West Gondwana
AU: * Trindade, R I
EM: rtrindad@iag.usp.br
AF: Universidade de Sao Paulo, Rua do Matao, 1226, Sao Paulo, SP 05508-090 Brazil
AB: In order to constrain the paleogeographic evolution of West Gondwana, an updated paleomagnetic database for Africa and South America is presented. The most striking feature that sorts out from the compilation is the contrasting evolution of most western Gondwana blocks with respect to Amazonia and the other Rodinian affiliates surrounding Laurentia. In our configuration they are separated from Laurentia and surrounding blocks by the Brasiliano Ocean which starts to close at around 940 Ma. The assembly of most of these blocks seems to have been accomplished by 630 Ma as indicated by the coincidence of their paleomagnetic poles, and the collisional ages recorded throughout the western Gondwana. On the other hand, paleomagnetic evidence is compatible with a Rodinian affiliation of Amazonia. In contrast to the other considered cratons, Amazonia seems to have joined the western Gondwana comparatively late, in the Early Cambrian, after rifting away from Laurentia at the end of Proterozoic times. In such scenario, the western Gondwana was formed through at least two distinct orogenic episodes comprising the assembly of central blocks around the Congo-Sao Francisco craton at ~630 Ma, which have collided later with Amazonia, Rio Apa, and Pampean blocks at ~520 Ma.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1527 Paleomagnetism applied to geologic processes
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2005 Joint Assembly