Introduction Volcanic activity from subduction of the Cocos plate is common along the plate margin that forms the Colombian Andes. Tephra deposits commonly coyer the Andes in Colombia, and they are usually attributed to the chain of active volcanoes along the Western and Cordillera Central, however volcanic activity to the east in the Cordillera Oriental has generally been dismissed. Recently, however, several authors have proposed that the volcanic rocks that occur in the localities of Paipa and Iza in the Cordillera Oriental originated from the subduction of the Caribbean plate. (Taboada, et al., 2000, Faure et al., 2003). Here we present data to support the existence of a thick, 20-40m, layer of volcanic ashes that most likely originated from volcanoes in the Cordillera Oriental. These newly discovered tephra deposits are partiaUy covered by a thinner layer of volcanic ash falls that in fact originated to the west from volcanoes of the Cordillera Central. One of the important aspects of these volcanic deposits is that their age is poorly known and as such, it is difficult to determine stratigraphie position and regional relationships. The recognition of Volcanic activity in the area during the last 5 to 10 million years must have increased the thermal gradient of the area therefore cause a significant impact in the timing of oil generation and oil migration in the Eastern Cordillera and Eastern Foothills.