Paleogene clockwise tectonic rotations in the forearc of central Andes, Antofagasta region, northern Chile
Résumé
[1] For the Central Valley of northern Chile (Antofagasta region), a paleomagnetic analysis of data from 108 sites, mainly in Mesozoic and Paleogene volcanic rocks, has yielded stable remanent magnetization directions for 86 sites. From these data, we infer clockwise tectonic rotations of up to 65°within the forearc domain of the central Andes. The apparent relationship between tectonic rotations and structural trends suggests that rotations occurred mainly during the Incaic orogenic event of Eocene-early Oligocene age. A few paleomagnetic results obtained in Neogene rocks do not show evidence of clockwise rotations. Hence the development of the Bolivian orocline during late Neogene time cannot be explained by simple bending of the whole margin. These results demonstrate that tectonic rotations within the forearc and pre-Cordillera are key elements of early Andean deformation, which should be taken into account by kinematic models of mountain building in the central Andes.
Mots clés
INDEX TERMS: 1525 Geomagnetism and Paleomagnetism: Paleomagnetism applied to tectonics (regional
global)
8110 Tectonophysics: Continental tectonics-general (0905)
8102 Tectonophysics: Continental contractional orogenic belts
1599 Geomagnetism and Paleomagnetism: General or miscellaneous
9360 Information Related to Geographic Region: South America
KEYWORDS: paleomagnetism
tectonic rotations
central Andes
northern Chile
Paleogene Citation: Arriagada
C
P Roperch
C Mpodozis
G Dupont-Nivet
P
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