During 1987 and 1988, a major field project sponsored by Tenneco was undertaken along the west flank of the Cordillera Oriental of Colombia between Alpujarra (between the Neiva and Girardot Sub-Basins) and the Middle Magdalena Basin (Cimitarra area). An important result of this study was the documentation of pronounced regional variation in the age, thickness, and facies of the Cretaceous section. The maximum thickness estimated was 7 km for the Bogota-Villeta section, with ages as old as Berriasian. This section can be divided