Thrust-front zone of the Precordillera, Argentina; a thick-skinned triangle zone

The frontal thrust zone of the Precordillera thrust belt of western Argentina only superficially resembles a classical Alberta-style triangle zone. In this thick-skinned triangle zone, the thrust front is the result of interaction between the eastward-verging, thin-skinned Central Precordillera and the westward-verging, thick-skinned Eastern Precordillera system. The western boundary, formed by the Niquivil thrust plate, has been refolded and faulted by thrust faults from the Eastern Precordillera at several localities. The deformation is still active. We divide the thick-skinned triangle zone into three segments based on the system's activity: independent, late interfering, and collision zones. Balanced cross sections across a thick-skinned triangle zone show a uniform shortening for the Eastern Precordillera ( approximately 17 km). The structural geometry suggests multiple reactivation of the main faults. The thick-skinned triangle zone began to grow after 2.6 Ma and is still active. Episodic and alternating opposing movement is controlled by buttressing of the thin-skinned thrust system against the basement structures of the Eastern Precordillera.