Paleogene foreland evolution in the Puna - Cordillera Oriental regions, NW Argentina

CECILIA DEL PAPA,; HONGN, F.; PAYROLA, P.; PETRINOVIC, I.; DO CAMPO, M.; POWELL, J.

Mendoza, Argentina

Congreso; International Sedimentary Congress; 2010

Asociación Internacional de Sedimentología

The identifications of tectonically significant features like distinct unconformity surfaces and growth-strata, along with the study of the stratigraphic record linked to structural analysis and vertical and lateral distribution of arc/backarc volcanism are proxies to constrain the history of mountain formation and foreland basin evolution. Due to its recorded history and evidence for uplifting of a non-collisional plateau, the origin of the Central Andes is a matter of controversy and constant research. Former research proposed a migration of deformation and exhumation in time and space southward (along-strike) and eastward (across-strike), consequently it is possible to track the chronology of mountain ranges formation and basin shifting cratonward. According to this, progressive propagation of sedimentation-deformation toward the east was proposed from the Cordillera Domeyko (Chile) in the Cretaceous-Paleocene to the Altiplano-Puna (Argentina) in the Oligocene, and subsequently to the Cordillera Oriental and Sierras Subandinas in the Middle Miocene. However, new investigation in the last years documented that the Andean deformation and sedimentation started in the Cretaceous time in Chile, but since the Eocene it expanded simultaneously within the Cordillera Domeyko, in the Puna (Pastos Grandes-Arizaro depozones) and in the Valles Calchaquíes – Cordillera Oriental. Current hypotheses consider that the Paleogene foreland deposits in the Puna and in the transition between Puna-Cordillera Oriental represent sedimentation in a wedge-top depozone basin as it has been already suggested for Bolivia. However structural analyzes revealed basement-involvement in deformation both in forethrust and backthrust styles. Also nearly 1500 – 2000 meters of preserved coarsening upward successions with mainly local provenance along with the presence of growth-strata and intraformational unconformities are evidence of active deformation and the existence of incipient relief dividing depozones. The described features support the idea that several belts of Paleogene deformation started simultaneously in a broad - 300 km across-strike - in which related depocenters accommodated the main sediment input. Toward the east (eastern portion of the Cordillera Oriental and Santa Bárbara System), the presumed Paleogene foredeep sedimentation is recorded in nearly 300 meters thick of mainly fine-grained sediments. The overall data suggest the existence of a series of Paleogene meridional depocenters analogous to compressional basins and ranges compatible with a scenario fitting a wedge-top basin model. Nevertheless some of the features mentioned also suggest that an alternative intermontane basin model should be considered.