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

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

Buenos Aires

Conferencia; SCAR XXXI. .4 th Open Science Conference; 2010

Dirección Nacional del Antártico

Antarctic Peninsula’s paleogeographic evolution since Gondwana’s fragmentation is still a subject of debate. This is so for two main reasons: the fact that the Scotia plate got in the way between the South America and Antarctica plates many millions of years after Gondwana’s break-up, destroying the ocean floor’s magnetic anomalies between these two plates in the process, and the fact that only a reduced amount of paleomagnetic data exists for 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 coast northwest of the peninsula (at coordinates 64°09’S and 60°57’W). Remanent magnetization of the samples was studied, along with the magnetic mineralogy and magnetic susceptibility anisotropy. 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 and coeval reference poles for East Antarctica suggests no latitudinal relative net motion between Antarctic Peninsula and cratonic East Antarctica and a ~ 40 – 65° clockwise relative net rotation, since then until these days. These results are in accordance with pre-existing rigid plate tectonic cinematic models for Gondwana’s break-up based on Weddell Sea’s ocean-floor spreading reconstructions using magnetic anomalies.