PALEOMAGNETISMO Y FÁBRICA MAGNÉTICA DE IGNIMBRITAS DEL JURÁSICO SUPERIOR DEL SUR DE PATAGONIA

PUIGDOMENECH C.G.; RENDA E.; SOMOZA R.; VIZAN H.; TAYLOR G.K.; FERNANDEZ R.; RODRIGUEZ AMENABAR C.

Congreso; Bienal Latinmag 2016; 2016

We report paleomagnetic and AMS results from seventeen sites of ca 153 Ma ignimbrites in the Deseadomassif, southern Patagonia. AMS results are variable, with the magnetic fabric controlled by ferromagneticminerals in some of the units and paramagnetic minerals in other units. Directional AMS data reveal thedominance of oblate to triaxial ellipsoids, that in most cases, can be used to explore the local directionof transport from the imbrication of the magnetic foliation and subordinately from the direction of themagnetic lineation.Although the paleomagnetic results may not fully averaged out the secular variation of the paleofield,the computed time-averaged paleomagnetic vector yields a paleopole (Lat. 86° S, Long. 55° E, dp= 12°,dm= 16°) indistinguishable from Jurassic and Cretaceous poles of South America, strongly suggesting thatPatagonia has been in its present-day position with respect to the main continent since at least the LateJurassic. The paleomagnetic data point to a long period (ca 65 Ma.) of ultra-slow polar wander for SouthAmerica. The results further indicate that ~155 Ma poles from South America (Patagonia) and North Americaare compatible with a GAD geometry of the paleofield if appropriate plate reconstructions are applied. TheSouth American poles suggest nonoccurrence of a true polar wander episode in the Late Jurassic.