Ar-39Ar geochronology of hydrothermal veins in sedimentary rocks of the Paja Formation (lower cretaceous) southern of the Santander department (Cordillera Oriental, Colombia)

Abstract

The K mica aggregates of vein filling, cutting through the organic calcareous mudstone of the Paja Formation (Lower Cretáceous) that crops out to the south of the Dpto. de Santander, register the main hydrothermal event associated to their formation. Their 40Ar-39Ar age is about 54 Ma, corresponding to the early Eocene. Such hydrothermal event is related in time and space with The Guamito thrust fault, which may have served as channel for the escape of deep
migratory fluids. In this context, the mentioned hydrothermal-deformation episode is an important additional event within the complex geological history that takes place prior to the clímax of the pre-Andean orogeny in the middle Eocene.