Paleomagnetic study of Mesozoic magmatic arc rocks at Cierva Point, northwest Antarctic Peninsula

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

Melbourne

Conferencia; XXV IUGG General Assembly; 2011

IUGG

A thorough paleomagnetic sampling of the Late Jurassic–Early Cretaceous rocks at Cierva Point (NW of the Antarctic Peninsula -AP-) has been carried out. The area’s outcrops consist of plutonic rocks emplaced in acid volcaniclastic rocks of the the Antarctic Peninsula Volcanic Group widespread in the northern AP. The age of the volcaniclastic rocks is assigned to the interval 162-153 My, based on a correlation with similar outcrops of that age, in an area close to Cierva Point. The plutonic intrusion is inferred younger because of its field relations with the host rock, and older than 95 My. Several rigid-plate cinematic models have been proposed for Antarctica since Gondwana’s break-up. One of these calculates its rotation poles from four interval poles between 160 and 83 My, which are obtained from magnetic and gravimetric lineations in western Weddell under the assumption that they represented movement between Antarctica and South America (SAM). Considering this model to be correct, the comparison between SAM’s reference poles and this study’s average poles suggests a net local counter-clockwise rotation with respect to a vertical axis of 61-47° between 150-120 My and 100-90 My. If, on the other hand, the poles obtained in this study are considered trustful paleomagnetic poles, the comparison between these and the reference East Antarctica (EANT) paleopoles of the same age suggests a regional counter-clockwise rotation of AP with respect to EANT between 150-120 My and 100 My, after which no relative motion would have taken place.