Paleomagnetism of Mesozoic magmatic bodies of the Fuegian Cordillera: Implications for the formation of the Patagonian Orocline

RAPALINI A.; PERONI J. I.; LUPPO T.; TASSONE A.; CERREDO M.E.; ESTEBAN F.; LIPPAI H.; VILAS J.F.

GEOLOGICAL SOCIETY OF LONDON SPECIAL PUBLICATION

Geological Society of London

Año: 2016 vol. 425 p. 65 - 80

0305-8719

It is not known whether the Patagonian Orocline, i.e. the major bend of the southern Andes at the southern tip of South America, is a primary or secondary feature. Paleomagnetic data along the Patagonian Orocline are still too scarce to provide a reliable and unambiguous answer to this question. New paleomagnetic results on Late Jurassic to Late Cretaceous magmatic units along the central segment of the Fuegian Cordillera are reported. Data from four Late Cretaceous small intrusions and three sites on Late Jurassic-Early Cretaceous metabasalts and metagabbros showed counterclockwise (ccw) declination deviations between 21° and 46° with respect to South America. From these and previous data a picture of a nearly homogeneous post- Late Cretaceous regional rotation of the central Fuegian Cordillera is suggested. This supports a model of nearly 30° of ccw secondary bending of the Patagonian Orocline since the Late Cretaceous (72 Ma). Lack of rotation of post-50 Ma sedimentary rocksexposed to the north of our study region, and larger rotations (of around 90°) reported to the south of it suggest that a geographical and/or temporal progression of rotation values from south to north in the Fuegian part of the Patagonian Orocline should be investigated.