Mr. De la Beche on the Geology of Jamaica. 193 



I am however inclined to consider some of the limestones which M. Humboldt 

 refers to the Jura limestone (oolite formation) as analogous to the Jamaica 

 white limestone, the compact beds of which, as I have before stated, very 

 much resemble those of the Jura in miner alogical structure ; and I am the 

 more inclined to adopt this opinion as M. Humboldt does not mention that he 

 found any characteristic fossils in the Jura-looking limestones of America, 

 which might lead us to conclude that the formations were distinct. He states 

 that he observed many whitish limestones, in part lithographic, in the equi- 

 noctial zone of America. These limestones occur at the cavern of Caripe (on 

 the S. E. of Cumana) ; on the coast of New Barcelona (Venezuela) ; at the 

 island of Cuba (between the Havanna and Batabano, and between La Trini- 

 dad and the Boca del Rio Guarabo) ; and among the central mountains of 

 Mexico (plains of Salamanca, and defile of Batas). The limestone formation 

 of the New Barcelona coast contains thin beds of hornstone passing into 

 flinty slate, a circumstance also observable at Zacatecas in Mexico. This is 

 somewhat analogous to the nodules of chert contained in the white marl of the 

 white limestone formation between Annotto Bay and Buff Bay. 



M. Humboldt says* : " in the vast steppes of Venezuela, near Tisnao, the 

 gres rouge supports, as it appeared to me, a lithographic limestone analogous 

 to the Jura limestone. This also occurs in Mexico, in the plains of Temas- 

 catio, to the south-west of Guanaxuato. At the northern extremity of the 

 valley of Mexico (between the Hacienda del Salto, Batas, and Puerto de 

 Reyes) a grayish blue limestone formation, containing gypsum, and support- 

 ing a calcareous breccia, appeared to me to belong to the Jura limestone, not- 

 withstanding the proximity of the tertiary marls (Desague de Huehuetoque,) 

 among which the bones of fossil elephants are found." This Jura-looking 

 limestone is also mentioned as occurring at the Caymana islands. While 

 sailing close to the south-eastern shore of Cuba for some distance, I observed 

 that the mountains presented white cliffs precisely resembling those of the 

 white limestone of Jamaica. Should these Jura-looking limestone rocks 

 turn out to be of the same age with the Jamaica white limestones, the latter 

 would appear to have been extensively deposited in this part of the world. 

 That it was so, is by no means improbable ; for the Jamaica white limestone 

 formation does not consist of a few thin beds, which might have belonged to 

 a small local deposit, but constitutes an extensive formation, which cannot be 

 less in some places than from 2000 to 3000 feet thick. 



In addition to the above rocks which M. Humboldt refers to the Jura lime- 



* Essai Geognostique sur le Gisement des Roches, p. 291. 



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