LOWEK CRETACEOUS. 581 



B-C 18. COLOMBIA. 



We are indebted chiefly to Hermann Karsten/"'' a physician and botanist, for 

 our knowledge of Colombia, and for the portion of that country shown on the map 

 of Noirth America we have followed his text. He distinguishes five terranes, of 

 which the oldest is the Jurassic, recognized at but one locality in New Grenada. 

 The next, the Lower Cretaceous, outcrops extensively throughout the mountains 

 and is distinguished by a great variety of cephalopods. • Karsten suggests that the 

 terrane may probably be divided into two formations owing to the presence of 

 belemnites, Ptychoceras, Humboldtianus KJrst., Ammonites noeggeratii Krst., Am. 

 rothii Krst., Am. santafecinus d'Orb., Am. houssingauUii d'Orb., and Hamites 

 arboledce Krst., in the lower beds, which are principally marls. The third series, 

 that of the Upper [1] Cretaceous, consists of thick deposits of limestones, sand- 

 stones, and siliceous shales and is identified paleontologically by a great number of 

 Rudistes which appear in the eastern portion, and of Polythalamies [Foraminifera], 

 which occur very extensively in the central and western districts. 



Succeeding these Cretaceous formations are Tertiary and Quaternary deposits 

 concerning which Karsten is quoted in Chapter XVII (p. 796) . In introducing his 

 description of the Cretaceous, Karsten refers to the absence of any trace of Paleozoic 

 rocks, and mentions specifically the discovery of Jurassic beds on the upper Mag- 

 dalena in New Grenada. As these beds appear to belong to the Lower Jm-assic 

 (Liassic), it is possible that the Upper Jurassic is represented in the higher strata 

 which underlie the Cretaceous. Karsten states: 



The oldest of the sedimentary formations is a sandy marl of a clear brown or yellowish- 

 red color and distinct stratification. It frequently is of great tliickness and sometimes contains 

 in the upper portion beds of blue or dark limestone which completely replace the marl in the 

 higher sequence. Sometimes a reddish-brown marl which closely resembles the preceding con- 

 tains flakes of mica or fragments of mica schist, as, for example, at Guaduas and at Bucaramanga. 

 The latter marl is, however, probably of more recent date than that which appears in contact 

 with the plutonic rocks and which is very poor in fossils, is without mica, firmer, etc. This 

 nonmicaceous marl occurring in the lower beds is found in all the eastern chain as well as at 

 several places in the central and western chains. It contains the following fossils: Ammonites 

 santafecinus d'Orb., Am. noeggeratii Krst., Am. loussingaultii d'Orb., Ptychoceras Jmmholdti- 

 anus Krst., Crioceras duvalii Lev. var. undulata Krst., and may therefore be regarded as the 

 equivalent of the Neocomien of Europe. At Cumanacoa remains of belemnites occur in a yel- 

 lowish-red marl and in a black calcareous shale which lies upon it. * * * This marl has at 

 Zapatoca a thickness of about 300 meters and is overlain by another bed which is also very 

 thick, of reddish-yellow quartzose sand, that in turn is followed by clay shales and limestones 

 of the horizon of the Gault, rich in fossil remains. The last-named lies upon beds of pebbles 

 and conglomerates derived from these same strata. 



Karsten describes several localities at which these strata appear and continues : 

 Although at the base of the Lower Cretaceous marls and shales predominate, the middle 

 portion of the series consists chiefly of limestones and the upper part of sandstones. These 

 sandstones here and there alternate with thick beds of siliceous shale and include also thin 

 strata of clay shale which are generally white, light, or yellowish in color, and of fine grain. 

 * * * In physical characters the beds resemble the Lower Cretaceous that immediately 

 underlies them, but they may usually be distinguished by the organic remains, especially char- 

 acterized by Inoceramus. The Upper is distinguished by an abundance of Polythalamies, 

 Orbitolina, Robuliaa, Nodosaria, and similar species. In the accompanying limestones one 



