Major crustal rotations in the Andean margin: Paleomagnetic results from the Coastal Cordillera of northern Chile

摘要: Paleomagnetic analyses of Mesozoic lavas and dike swarms from the northern Chilean Coastal Cordillera, between 25.4°S 26.4°S, reveal a clockwise rotation about 42°. Magnetizations lava flows andesitic-basaltic composition Middle Jurassic La Negra Formation pass both fold reversal tests are interpreted as prefolding remanences. Five to Early Cretaceous age yield similar directions that obtained Formation. Four five have mixed polarity, suggesting they too carry primary or very early remanence. The structural setting dikes suggests not suffered any substantial tilting nonvertical axes since acquisition area is believed been consequence transpressional deformation mid–Late age, post-100 Ma, associated with abandonment Jurassic–Early magmatic arc in this region its eastward migration form new former back region. This younger located east Cordillera lies Central Valley sense consistent other paleomagnetic data Chile southern Bolivia, south Arica Deflection Andean margin, although it largest yet reported. To north Deflection, studies report counterclockwise rotations, several large-scale models proposed explain overall pattern rotations. Models include oroclinal bending an originally straight differential shortening across margin at preexisting bend which subsequently tightened by passive limbs bend, distributed shear throughout oblique convergence bend. In contrast these models, workers argued better explained terms localized situ We review light our results present domino-type model blocks bounded left-lateral faults rotating response mid-Late transpression within crustal scale zone. observed strike-slip fault systems identified Cordillera.