The Palestina Fault, Colombia
The Palestina fault is an inactive right-lateral wrench fault more than 350 km long in the largely metamorphic and igneous terrain of the northern Central Cordillera of the Colombian Andes. It strikes north to north-northeast, nearly parallel to the regional Andean structures. Much of the fault is followed by straight canyons 50 to 600 m deep. A zone of breccia and mylonite less than 50 m thick marks the fault. Rock is intensely fractured within 50 m of this breccia zone. Deformational effects of the Palestina include large fault-block slivers of megabreccia and drag “tails” that contain some allochthonous material. A gravity profile across the Palestina shows no associated anomaly. Horizontal displacement on the Palestina of 27.7 km is well documented because the fault has offset ten unique lithologic, metamorphic, and structural features that have been mapped on both blocks. These offset features are: marble, quartzite, feldspathic and aluminous gneiss, diorite, zones of diorite mixed with Precambrian gneiss, hornblende gabbro, Cretaceous shale, metamorphic isograds, a major wrench fault, and several minor faults. The Palestina fault is only one of several recently recognized wrench faults in the northern Central Cordillera, and its documentation should call attention to the possible importance of these features in the tectonics of the area. Published analyses of wrench-fault tectonics in northern Colombia and Venezuela assume a genetic relationship between all the wrench faults: they originated in response to a single unchanging regional stress system. A more meaningful analysis might result from the individual study of smaller geographic areas and consideration of the relative ages of the wrench faults.