CONICET | Buscador de Institutos y Recursos Humanos

The Loncopué Trough is located in the hinterland Andean zone between 36◦30 and 39◦S. It constitutes a topographic low bounded by normal faults and filled by lavas and sediments less than 5Ma old. Reprocessed seismic lines show wedge-like depocenters up to 1700m deep associated with high-angle faults, correlated with the 2717Ma Cura Mallín basin deposits, and buried beneath Pliocene to Quaternary successions and Late Miocene foreland sequences. The southern Central Andes seem to have been under extension in the hinterland zone some 27Ma ago and again at approximately 5Ma ago. This last extensional period could have been the product of slab steepening after a shallow subduction cycle in the area, although other alternatives are discussed. Orogenic wedge topography, altered by the first extensional stage in the area, was recovered through Late Miocene inversion, and was associated with foreland sequences. However, since the last extension (<5 Ma) the Andes have not recovered their characteristiccontractional behavior that controlled past orogenic growth.