10 Annals of the Carnegie Museum. 



Lakes and Swamps. — There are several small mountain lakes in the 

 paramos near the crest of the Sierra Nevada, fed by the melting snow- 

 fields above, and feeding in their turn certain of the rivers which take 

 their rise here. Aside from these, there are no true lakes in this 

 region, but only lagoons at various points along the coast. Isolated 

 marshes occur at intervals in connection with these, while the entire 

 country surrounding the Cienaga Grande is one immense marsh, and 

 during the rainy season is often completely overflowed for several 

 miles inland. 



Geological History. 4 



In general structure and in the character of its rock formations 

 the Sierra Nevada de Santa Marta resembles most other sections of 

 old land found in the Caribbean region (northern Venezuela, the West 

 Indies, and Central America), and there is reason to believe that at 

 one time it constituted a part of the Antillean land mass, of which the 

 islands of Curasao, Aruba, etc., are also remnants. At any rate, it is 

 a very old section of the earth's crust, having been elevated above sea- 

 level since the beginning of the Palaeozoic (at least), and not there- 

 after submerged. The region east and south of the Sierra Nevada 

 was probably covered by the sea in the Mesozoic, surely during the 

 Cretaceous, as evidenced by the presence of marine deposits of that 

 age. Subsequently, this region was elevated above the sea, and the 

 Sierra de Perija (Sierra Negra) was folded up. The folding did not 

 extend to the Sierra Nevada, except in its northeastern part. This 

 movement took place in the second half of the Tertiary, as is known to 

 be the case with the Andean uplift in general, while the region to the 

 east of the Sierra Nevada was land already in the first part of the 

 Tertiary. 



The two mountain systems, therefore, are entirely distinct and inde- 

 pendent in their respective origins, the Sierra Nevada being very old 

 (geologically speaking), the Sierra de Perija (a branch of the Andean 

 system) very young; only at the northern end of the latter did the 

 forces which caused its elevation slightly encroach upon the older 

 mountain. All the evidence goes to show that all through the Ter- 

 tiary and thereafter the valley of the Rio Cesar (and its northern con- 

 tinuation) has been in existence, and that at no time could it have 



4 Ex Sievers, by Dr. Arnold E. Ortmann. 



