Paleomagnetic study of Mesozoic magmatic arc rocks in NW Antarctic Peninsula. Tectonic implications.

COSENTINO, N. J.; TASSONE, A.; VILAS, J. F.

Buenos Aires

Conferencia; XXXI SCAR Delegates 2010; 2010

Scientific Committee on Antarctic Research

Antarctic Peninsula?s paleogeographic evolution since Gondwana?s fragmentation isstill a subject of debate. This is so for two main reasons: the fact that the Scotia plate got inthe way between the South America and Antarctica plates many millions of years afterGondwana?s break-up, destroying the ocean floor?s magnetic anomalies between these twoplates in the process, and the fact that only a reduced amount of paleomagnetic data existsfor Antarctic Peninsula. A thorough paleomagnetic sampling of Cierva Point?s Late Jurassic ?Early Cretaceous magmatic arc rocks has been carried out, located in the Danco coastnorthwest of the peninsula (at coordinates 64°09?S and 60°57?W). Remanent magnetizationof the samples was studied, along with the magnetic mineralogy and the anisotropy ofmagnetic susceptibility (AMS). A trustworthy 150 ? 120 Ma paleomagnetic pole (78,1°S;55,8°E; dp = 8,7°; dm =9,9°; N = 9) was obtained. The comparison between this pole andcoeval reference poles for East Antarctica suggests no latitudinal relative net motion betweenAntarctic Peninsula and cratonic East Antarctica and a ~ 40 ? 65° clockwise relative netrotation, since then until these days. These results are in accordance with pre-existing rigidplate tectonic cinematic models for Gondwana?s break-up based on Weddell Sea?s ocean-floor spreading reconstructions using magnetic anomalies.