Present-day structural frame of the Santander Massif and Pamplona Wedge: The interaction of the Northern Andes

Abstract

Based on regional geology and stress tensor analysis from fault slickensides, we propose a structural model to explain the present-day configuration of a crystalline core in the northern Andes of Colombia (the Santander Massif - SM). The SM has undergone transpressional tectonics in a domino-style, controlled by longitudinal sinistral strike-slip faults as the Bucaramanga Fault. The tectonic style also exhibits NE-SW trending transverse inner faults with dextral strike-slip kinematics. The transpressional regime of the SM differs from the compressive regime that characterizes nearby blocks (northern Perijá Range, southern Floresta Massif, and eastern Pamplona Wedge). Transpressional structures result from a regional W-E horizontal compression corresponding to the current stress field as determined here by cross-cutting relations, mainly observed in the Pamplona Wedge. Stress tensors also show maximum horizontal stress (SHmax) in radial pattern towards the wedge deformation front, whose influence spreads over the SM western border. The W-E regional compression also explains the tectonic syntaxes formed by the Pamplona Wedge to the north and the Sierra Nevada de Güicán or El Cocuy to the south. These two areas are characterized by the opposite outward vergence of their compressive deformation fronts.