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

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

BOLLETTINO DI GEOFISICA TEORICA ED APPLICATA

ISTITUTO NAZIONALE DI OCEANOGRAFIA E DI GEOFISICA

Lugar: Trieste; Año: 2010 vol. 51 p. 130 - 134

0006-6729

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 (AP). A paleomagnetic sampling of Cierva Point’s Late Jurassic – Early Cretaceous magmatic arc rocks has been carried out; the studied area is located in the Danco coast northwest of the peninsula, at coordinates 64°09’S and 60°57’W (Fig. 1), within a protected area (ZAEP 134) which also includes the argentinian base Primavera. A number of different rigid-plate cinematic models have been proposed for Antarctica since Gondwana’s break-up. One of these (Ghidella et al., 2002) 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). This model does not take into consideration relative movement between AP and SAM, and does not generate any overlapping between these continental masses. Considering this model to be correct, the comparison between SAM’s reference poles and this study’s average poles (Fig. 7) 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 (Fig. 8) suggests a regional counter-clockwise rotation of AP with respect to EANT between 150-120 My and 100 My, after which no more relative motion takes place. Paleogeographic reconstructions according to the Konig & Jokat (2006) plate model give credence to these results.