HR: 1340h
AN: GP33A-0091    [Abstracts]
TI: Paleomagnetic Evidence for a Transpressional Grenville Orogen: Sinistral Offsets Between Amazonia and Laurentia Point to an Evolving Rodinia
AU: * Tohver, E
EM: etohver@usp.br
AF: Universidade de Sao Paulo, Instituto de Geociencias - GMG Rua do Lago, 562, Sao Paulo, SP 05508-080 Brazil
AU: * Tohver, E
EM: etohver@usp.br
AF: Universidade de Sao Paulo, Instituto de Astronomia e Geofisica Rua do Matao, 1226 Cidade Universit ria, Sao Paulo, SP 05508-900 Brazil
AU: D'Agrella Filho, M
EM: dagrella@iag.usp.br
AF: Universidade de Sao Paulo, Instituto de Astronomia e Geofisica Rua do Matao, 1226 Cidade Universit ria, Sao Paulo, SP 05508-900 Brazil
AU: Orestes Santos, J
EM: orestes1@uol.com.br
AF: Geological Survey of Brazil (CPRM), Rua Banco da Provıncia, 105, Porto Alegre, RS 90110-150 Brazil
AU: Elming, S
EM: sten-ake.elming@sb.luth.se
AF: Lulea University of Technology, Department of Applied Geophysics, Lule†, 95187 Sweden
AU: Trindade, R I
EM: rtrindad@iag.usp.br
AF: Universidade de Sao Paulo, Instituto de Geociencias - GMG Rua do Lago, 562, Sao Paulo, SP 05508-080 Brazil
AU: Teixeira, W
EM: wteixeir@usp.br
AF: Universidade de Sao Paulo, Instituto de Geociencias - GMG Rua do Lago, 562, Sao Paulo, SP 05508-080 Brazil
AB: We report three new paleomagnetic poles from the Amazon craton for the Meso/Neoproterozoic Grenvillian interval, a period notable for the eponymous continental collision that affected the eastern margin of Laurentia. The poles were derived from study of ca.1230 Ma mafic sills (Figueira Branca ­V 40Ar/39Ar biotite), the 1149 ,b7 Ma sediments of the Aguapeí Gp. (U-Pb SHRIMP analysis of authigenic xenotime) and the ca.980 Ma basaltic dykes and flat-lying flows (40Ar/39Ar biotite) that intrude and overlie the Aguapeí Gp. sediments. These new data define a skeletal apparent polar wander path marked by a counterclockwise loop, similar to that observed for North America and Baltica. A pole-by-pole comparison of the Amazon and North American data demonstrates the evolving paleogeographic affinity of these two continents, marked by the large-scale strike-slip movement of Amazonia relative to Laurentia. The 3000 km of sinistral offset between these two continents is substantiated by a 200 Ma record of sinistral transpression recorded in the 1.2-1.15 Ga deformation of basement rocks of the Amazon craton, the 1.1 Ga Nova Brasilandia belt, and the 1.05-1.0 Ga Sunsas belt of eastern Bolivia. Our observations suggest that transpressional collision of the Amazon craton and Laurentia was responsible for the bulk of Grenvillian deformation, as opposed to the multiple continents required by other Rodinia models.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 8103 Continental cratons
DE: 8104 Continental margins: convergent
DE: 9619 Precambrian
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005