Middle Eocene-Oligocene broken foreland evolution in the Andean Calchaqui Valley, Nw Argentina: Insights from stratigraphic, structural, and provenance studies.

C. DEL PAPA; HONGN, F.; POWELL, J.; PAYROLA, P.; DO CAMPO, M.; STRECKER, M.; PETRINOVIC, I.; SCHMITT, A.; PEREYRA, R.

BASIN RESEARCH

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 vol. 25 p. 574 - 593

0950-091X

The evolution of Paleogene Andean forelands in NW Argentina remains amatter of continuing debate because the geological complexity of the areasinvolved makes it difficult to apply classical foreland models. Two end-membermodels have been proposed: a simple W-E migrating foreland model and abroken foreland model. We present stratigraphic, sedimentological, andstructural data from the Paleogene Quebrada de los Colorados (QLC)Formation, in the Cordillera Oriental, against the background of these differentmodels. The unconformities, growth-structures, and changes in provenance andpaleoflow directions all indicate deposition of the QLC Formation in atectonically active basin. Paleo-structures- both west and east vergent - rootedin basement blocks, controlled the deposition and distribution of the QLCFormation. The timing of sedimentation (~middle Eocene - early Miocene) andthe variability in provenance indicate that the main source areas for this basinwere disparate basement blocks uplifted during Paleogene shortening, and inparticular the uplifted areas that resulted from the exhumation of the ComplejoEruptivo Oire that delimited the eastern margin of the proto-Puna, and from theearly exhumation of the Cretaceous-Paleogene Salta Basin. A comparison ofthe Quebrada de los Colorados Basin pattern with those of the Paleogenebasins in the Puna, in the thin-skinned Sierras Subandinas, and in the thickskinnedSanta Bárbara System, highlights the presence of discrete depocentersthat reflect the early compartmentalization of the broken foreland rather than thethrust belt migration toward the foreland. The early Tertiary foreland evolution ofthe southern central Andes is represented by a zone ~250km wide comprisingseveral deformation belts (Domeyko, Arizaro, Pastos Grandes and Calchaquí),in which inherited upper crustal heterogeneities promoted doubly-vergentstructures. Clastic deposition took place along these basement uplifts, initiallyas interconnected and open-drainage basins and subsequently as isolated, andat times coalesced, basins with internal drainage.