The Jáchal river cross-section revisited (Andes of Argentina, 30°S): Constraints from the chronology and geometry of neogene synorogenic deposits

摘要: Abstract In the southern Central Andes, between 27 and 33°S, a flab-slab subduction has been established since last 10 Ma. This particular geometry proposed to control eastward migration of deformation, with Precordillera fold-and-thrust belt development uplift foreland Sierras Pampeanas basement blocks. this study, we present 190 km-long structural section, across easternmost Cordillera Frontal, westernmost sector Pampeanas, revise both previous kinematic models, relationship establishment flat-slab deformation in foreland. For purpose, integrate published sedimentological data new analysis. Our forward model is fed back by: (i) geometries Neogene deformed beds throughout Precordillera, such as sedimentary wedges angular unconformities; (ii) flexural subsidence due topographic loads for each step, constrained by measured stratigraphic sections; (iii) revised chronostratigraphy correlation chart Cenozoic units; and, (iv) recent constraints on ages activity faults. allows us build that considers timing main structure its sedimentation, producing better geometrical, paleogeographical than proposals. The results modelling are presented six different evolutionary stages. During first stage, 19 15 Ma, eastern Frontal uplifted, associated Rodeo-Iglesia proximal basin, low Bermejo distal basin. second 15 12 Ma, Western took place, creation shallow detachment beneath third 12 8 Ma, was beginning pulse Valle Fertil range. next 8 5 Ma, rapidly deformed. Between 5 2 Ma, almost ceased, focus contractional shifted Eastern Precordillera. 2 Ma phase characterized strike-slip basin key amount total shortening, 66 km (35%), calculated cross-section, significantly less previously proposed, shallower (∼6.5 km vs 16 km) models. point connect ramp-plane detachment, suggested, but allowing at same time generation observed