RELATIONSHIP BETWEEN TECTONIC AND PALEOENVIROMENTAL EVOLUTION IN THE TRES CRUCES FORELAND BASIN, NORTHWEST ARGENTINA.

GALLI, C.I.; VILLALBA ULBERICH, J.P.

Viena

Conferencia; Session TS4.5/GM4.5/SSP3.19 - The Andean foreland basins: Tectonics, climate, surface processes, and georesources.; 2018

EGU 2018 General Assembly

The foreland basin of the Central Andes in NW Argentina is formed by partially unconnected basins limited by uneven high ranges. The Tres Cruces Basin is located in the foothills of the Central Andes in NW Argentina in the Eastern Cordillera. This basin resulted from a Cretaceous to Paleogene rifting event (Salta Rift Basin) and from Neogene foreland basin stages (Tres Cruces Basin) to Quaternary intermountain Basin. For this study field data, seismic reflection, lithostratigraphic, paleoenviroment evolution, paleocurrents and satellite images have been interpreted. The propagation of deformation in this sector of the Andes is influenced by inherited structures (e.g. Cretaceous extensional faults), which have been reactivated during Andean compression as high angle and oblique reverse faults. Deformation does not advance regularly throughout the foreland in a normal forward sequence but jumps across inherited faults. Fault reactivation has resulted in uplift of basement cored ranges and hanging wall anticlines that divided the foreland into small basins. The Tres Cruces basin show many characteristics of the broken foreland basin models. Analysis of the Tres Cruces Basin along the seismic line, integrates a new lithostratigraphy, subsidence analysis, new interpretations of seismic lines and a balanced cross-section.The integration of internal features of syntectonic units from the analysis of sedimentary columns, the paleocurrents analysis and the restored basin geometry allow us to link the basin evolution history related to orogenic growth (spatial/temporal loading configuration). In this context, the Tres Cruces Basin is located in Northwestern of Argentina on the western margin of the Eastern Cordillera and exhibit a sedimentary fill that would be expected for a foreland basin with an orogenic wedge advancing eastward. Three units can be distinguished: Casa Grande, Rio Grande and Pisungo Formations. Casa Grande Formation has a very difficult contact with Lumbrera Formation. In some places is transitional, in others erosional or by a progressive unconformity. Rio Grande Formation is transitional to Casa Grande in most of the areas and by an unconformity in the East of the basin. The beginning of Pisungo Formation is related with an increment of the size of the clasts and by the presence of Santa Bárbara Subgroup as a member of clasts. The paleoenvironment evolves from a meandering system (Casa Grande Formation), into a braided system (Río Grande Formation) to a proximal alluvial fans composed by debris flows (Pisungo Formation), showing a progradation from a distal to a proximal environment with a progressive decrease of the accommodation space.