The fracture patterns of the Tin Tin anticline: Fracturing process during the foreland evolution in the Calchaquí Valley, northwestern Argentina

- Fractures of the Yacoraite Formation of northwestern Argentina are analyzed.
- Fracturing processes are related to the thrust belt-foreland system in NW Argentina.
- Extension fractures were formed prior to small-scale faults.
- All fractures were formed before folding and thrusting stage.

We present a field-based work which illustrates the fracture patterns of the carbonate-silicoclastic Yacoraite Formation in the Tin Tin anticline, a basement fault-related fold located in southern part of the Eastern Cordillera, northwestern Argentina. The fracture patterns include small-scale strike-slip faults (vertical shear fractures and en echelon arrays), thrust faults, extension fractures (joints, veins and normal faults) and stylolites. Extensional mesostructures were formed by along-foreland stretching, prior to the contractional ones that were formed by the layer-parallel shortening mechanism. Furthermore, all fractures are interpreted to be formed before or at the early stages of folding and thrusting during the Andean contraction, all of them belonging to the Eocene thrust belt-foreland system at the Calchaquí Valley of northwestern Argentina.