Kinematics of Tertiary to Quaternary intracontinental deformation of upper crust in the Eastern Cordillera, southern Central Andes, NW Argentina

摘要

To elucidate factors controlling the geometry of, and kinematics associated with, prominent upper-crustal structures in the Eastern Cordillera of NW Argentina, structural analyses of key areas were complemented by fault slip analysis, remote sensing and 3D representation of prominent faults. The analyses revealed that deformation during Tertiary to Quaternary times was accomplished mostly by prominent orogen-parallel reverse faults, the geometry of which was significantly influenced by Paleozoic and Cretaceous planar structures. Locally, this deformation was preceded by kilometer-scale doming of upper-crustal rocks. Analysis of 767 brittle faults at 67 stations in the studied areas indicates that local upper-crustal doming and orogen-parallel reverse faults formed chiefly under NW-SE and E-W shortening. Shortening directions inferred from fault slip data portray the kinematics of first-order faults and folds. More specifically, shortening directions are mostly uniform with respect to first-order structures. Age and kinematics of deformation inferred from brittle fault analysis in the study areas is consistent with equivalent data compiled from other parts of the Eastern Cordillera, Puna and Pampean Ranges. Collectively, the data is at variance with hypotheses relating late Tertiary to Quaternary deformation in the Eastern Cordillera to plate (boundary) kinematics. The kinematics of intracontinental deformation in the southern Central Andes points to deformation partitioning of upper crust as a consequence of bulk E-W shortening. We, therefore, caution the usage of brittle fault-kinematics in continental interiors as an indication for plate-kinematic changes.