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Indiana University Studies 



crossed by streams. The upper Magdalena has cut into these Cor- 

 dilleras lengthwise so that it runs between two of its chains north 

 as far as Honda. At Honda the Magdalena cuts thru the western- 

 most chain of the Cordillera of Bogota and flows into the depression 

 (fault?) between the central Cordillera and the Cordillera of Bogo- 

 ta. Towards the north the Cordillera widens and then divides 

 into several chains separated by plains. The westernmost one of 

 these is the Sierra de Perija, which extends to the Sierra Nevada 

 de Santa Marta. The middle chains are replaced on the north by 

 Lake Maracaibo, the eastern largest one becomes the Cordillera 

 of Merida, which ends at the depression of Barquisimeto be- 

 yond which are the Caribbean mountains, the coast Cordilleras 

 of Venezuela. 



The Cordillera of Bogota, aside from a few quarternary de- 

 posits laid down after the formation of the Andes, consists prob- 

 ably entirely of cretaceous sedimentary rocks. The youngest 

 rocks, the Guaduas layers, may be tertiary. A few rocks older 

 than the cretaceous are the half crystalline blue and green slates 

 with quarzite and quarzitic conglomerate seen near Quetame. 

 The southern part of the Cordillera of Bogota are simple erect, or 

 slightly inclined, mountain folds, comparable to the Jura. The 

 westernmost ones consist of the Guaduas layers and are the 

 youngest. During the entire cretaceous, and perhaps part of the 

 tertiary, it was submerged. The formation of the mountains 

 probably began in the tertiary and did not produce notable modi- 

 fication in the quarternary. 



The fourth of the Cordilleras of Colombia is the coast Cor- 

 dillera. This is the youngest of the great mountain chains of 

 Colombia. It has also been studied by Hettner, 3 and I cannot 

 do better than present an abstract of this paper. 



The coast Cordillera begins at the bay of Buenaventura and 

 extends thru more than three degrees to the slight depression of 

 the Truando which separates it from the mountains of Darien. It 

 reaches a maximum height of 1,800 m., but ordinarily does not 

 exceed 1,000 m. Near the middle there are really two chains 

 between which the Baudo flows. The western slope is very steep, 

 the distance between the crest and the ocean being, in some 

 places, only a few hundred feet. According to Karsten, the 

 rocks of the coast Cordilleras bear fossil species of shells and cor- 

 als that still live in the Pacific Ocean at the base of these moun- 



3 Die Andcn dcs ucsllichen Cclumbiens. Petermanns Mittheil, 1893, p. 129. 



