A geologic traverse was made by the author in 1939 along the road from Bogota to Villavicencio, a distance of 122 kilometers. The purpose was to attempt to correlate the rocks of the little known east side of the Cordillera Oriental with the better known formations of the Magdalena Valley on the west side of the mountains.

The rocks exposed along the traverse are sedimentary and metamorphic, and range in age from possible Cambrian to Pleistocene; only the Cretaceous rocks yielded abundant fossils. Igneous rocks reported to occur both north and south of the line of traverse were not encountered in this particular section, although the basal conglomerate of the Cretaceous contains fragments of granite.

The formations observed along the road, with their respective ages, are the following: Quetame, Cambrian (?); Vinculo, Devonian (?); Pipiral, Carboniferous (?); Colorado, Permian (?); La Argentina, Cretaceous (?); Caqueza, Cretaceous (Lower Valanginian); Villeta, Cretaceous (Upper Valanginian, Hauterivian, Barremian, and Aptian); Guadalupe, Cretaceous (Middle Albian and Cenomanian); Buena Vista, Tertiary (?); Guaduas, Tertiary, Eocene (?); terraces, Pleistocene.

The principal structural features are the Bogota fault, an overthrust to the west; the Caqueza fault, an overthrust to the east; the San Martin fault, normal, with the westerly block downthrown; the Argentina fault, normal, with the easterly block downthrown; and the Cientoquince fault, an overthrust to the east. In addition, the Guadalupe

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formation is folded into a large, gentle syncline, and all the rocks show a very great number of small folds.

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