Response of intracontinental deformation in the central Andes to late Cenozoic reorganization of South American Plate motions

Abstract

New stratigraphic, chronologic, and fault kinematic data from the Quebrada del Toro in northwestern Argentina provide a detailed view of late Cenozoic kinematic reorganization in the southern central Andes. The Quebrada del Toro is a thrust‐bounded basin filled with 2 km of synorogenic clastic deposits, ranging in age from early Miocene to Holocene. As observed elsewhere in northwestern Argentina, faults in the Quebrada del Toro record an early phase of horizontal NW‐SE contraction (beginning between early and late Miocene and ending after 0.98 Ma) and a later phase of horizontal NE‐SW contraction (beginning between late Miocene and 4.17 Ma and still active). These results require both kinematic regimes to have been active between 4.17 and 0.98 Ma, compatible with timing and kinematic data from the adjacent central Andes and best explained by a temporal pattern of serial recurrence of the kinematic regimes. A hypothesis that intraplate deformation in the central Andes is driven by the absolute motion of the South American Plate with respect to the hotspot reference frame is tested by comparing Quebrada del Toro kinematics to plate reconstructions and space‐based geodetic results. Nazca‐South America relative motion and absolute Nazca Plate motion show consistent azimuths throughout the past 20.5 Myr. In contrast, absolute South American Plate motion azimuths mimic the changing contraction directions determined from intraplate Andean faults. Although the timing of the South American Plate motion change is poorly resolved by current data, it is compatible with the Quebrada del Toro data. Absolute upper plate motion might control intraplate kinematics along many of the Earth's convergent margins.