HR: 14:15h
AN: GP33A-04    [Abstracts]
TI: Exploring the Tectonic Behavior of Patagonia During the Breakup of Gondwana: A Paleomagnetic Approach
AU: * Somoza, R
EM: somoza@gl.fcen.uba.ar
AF: Universidad de Buenos Aires, Dpto. Geologia, Pabellon 2, Cdad. Universitaria, Buenos Aires, C1428EHA Argentina
AU: Taylor, G K
EM: G.Taylor@plymouth.ac.uk
AF: University of Plymouth, Dep. Geological Sciences, Drake Circus, Plymouth, PL4 8AA United Kingdom
AU: Vizan, H
EM: haroldo@gl.fcen.uba.ar
AF: Universidad de Buenos Aires, Dpto. Geologia, Pabellon 2, Cdad. Universitaria, Buenos Aires, C1428EHA Argentina
AB: Recent paleogeographical models for southwest Gondwana place the Malvinas/Falkland islands in connection with the Cape Fold Belt in South Africa. This reconstruction is further supported by a large clockwise rotation (ca. 100°) paleomagnetically detected in Early Jurassic dolerites from the islands. The regional extent of this rotation is, however, still unknown. This led us to investigate the pre-Jurassic paleomagnetic record of the Deseado Massif, the closest continental region to the Malvinas/Falkland Islands, to determine whether it too records a Jurassic-Cretaceous rotation history. We sampled Upper Triassic and Jurassic units, both sedimentary and intrusive. The results suggest the occurrence of clockwise vertical-axis rotations comparable in both magnitude and sense to those previously detected farther north in Upper Jurassic-Lower Cretaceous rocks from the North Patagonian Massif but having considerably smaller magnitude than those in the Falklands/Malvinas. This latter contrast suggests that the intervening region between the Deseado Massif and the islands, in the present Argentine shelf, would has been a zone of major structural discontinuity, although offshore exploration did not identify any such zone yet. Alternatively it may have been a zone of distributed deformation with rotation decreasing westward. In any case, the continuity of rotations within Patagonia requires further investigation to determine its pre-breakup configuration and later kinematics. This may contribute in clarifying the microplates' puzzle of southwest Gondwana.
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1527 Paleomagnetism applied to geologic processes
DE: 8109 Continental tectonics--extensional (0905)
DE: 9325 Atlantic Ocean
DE: 9360 South America
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2005 Joint Assembly