About the presence of pre-Cretaceous and Post- Girón (Jura-Triassic) faults, in the western Flank of the Santander Massif (Eastern Cordillera, Colombia)

Abstract

Two faults in which it has been pointed out the existen ce of a movement previous to the Cretacic and posterior to the Girón (Jura-Triassic) were studied. One of them (Aratoca's Fault) has not had any movement after the Cretacic and it is unconformably covered by the Cretacic. The other one (Matanza's Fault ) again was in movement after the Cretacic, having moved in opposed direction to the irritial movement ; this fact is indicated by the sudden disappearance of the Giron E of such fault. These pre-cretacic fauIts have pararelism with the general post-cretacic faulting. Also Matanza's fauIt shows the existence of faults with double movement pre and post-cretacic, this together with the analysis of disposition of overthrust sides in the post-cretacic fauIts, demostrates that the double movement of the Matanza's fault is not an isolated fact buy probably makes up a general feature of the tectonic of this region. Therefore after the Girón or during its own deposition, took place a period of distention with formation of normal faults which can he related to the tilting affecting the Girón and with the formation of a depressed area between the Macizo of Santander and the Colombian Cordillera Central; the great part of these fauIts moved as thrust faults with posteriority to the Cretacic and they are tied to tbe stage of folding of the Cordillera Oriental