Tectonic implications of a paleomagnetic study of mesozoic magmatic arc rocks in northwest Antarctic Peninsula

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

San Francisco

Conferencia; 2010 AGU Fall Meeting; 2010

AGU

Antarctic Peninsula?s paleogeographic evolution sinceGondwana?s fragmentation is still a subject of debate. This is sofor two main reasons: the fact that the Scotia plate got in the waybetween the South America and Antarctica plates many millions of yearsafter Gondwana?s break-up, destroying the ocean floor?smagnetic anomalies between these two plates in the process, and the factthat only a reduced amount of paleomagnetic data exists for AntarcticPeninsula. A thorough paleomagnetic sampling of Cierva Point?sLate Jurassic - Early Cretaceous magmatic arc rocks has been carriedout, located in the Danco coast northwest of the peninsula (atcoordinates 64°09?S and 60°57?W). Remanentmagnetization of the samples was studied, along with the magneticmineralogy and the anisotropy of magnetic susceptibility (AMS). Twopaleomagnetic poles were obtained, one of age 150-120 Ma (76.5°S;49.2°E; dp = 7.6°; dm =8.7°; N = 11) and another one of age100-90 Ma (82.4°S; 148.3°E; dp = 3.6°; dm = 4.1°; N =19). The comparison between these poles and coeval reference poles forEast Antarctica suggests a counter-clockwise net rotation of AntarticPeninsula with respect to East Antarctica of between 70° and 45°between 150-120 Ma and 100 Ma, after which no further relative movementtook place. These results are in accordance with pre-existing rigidplate tectonic cinematic models for Gondwana?s break-up based onWeddell Sea?s ocean-floor spreading reconstructions using magneticanomalies.