HILL: GEOLOGY OF JAMAICA. 171 



Mountain Series have great development where they constitute the 

 highest mountain summits, the Pico del Yaqui, reaching an altitude 

 of 9,684 feet (2,955 meters) according to Schomburgk. They are also 

 probably the nucleal material of the Republic of Haiti, and its two 

 westward extending peninsulas. This formation has been described 

 by Gabb ^ as the Sierra group, and his descriptions in every way 

 coincide with it as it occurs in Jamaica, except that it contains some 

 gravel of different material. 



The occurrence of these rocks in the islands to the east of San 

 Domingo is based upon the descriptions given by Cleve in his ex- 

 cellent work on the Northeastern West Indian Islands. ^ He has 

 described, as the ^' Bluebeache " from St. Thomas,^ a formation fully 

 6,000 feet in thickness consisting of stratified conglomerates and tuffs 

 largely made up of hornblendic igneous material, which he says also 

 occurs beneath the white limestone formations, on the north side of 

 Porto Rico,* and which he considers probably of Cretaceous age. He 

 has also described the same formation from the Virgin Islands to the 

 eastward. 



This formation, which is over 5,000 feet in thickness in Jamaica 

 and 6,000 feet in St. Thomas, is the most important landmark in 



Henneken, Gabb, and Tippenhauer present prospective views of the general geology 

 successively controverting in a more or less degree the previous observations. 



Gabb's report on the Geology of San Domingo, notwithstanding its value, 

 presents a confusion of data concerning the Tertiary sequence and the white 

 limestones in general, very similar to that concerning allied formations in Jamaica. 

 After careful study of the work I am of the opinion that he has failed to interpret 

 correctly the stratigraphy of these formations. There can be no doubt that he has 

 confused the two great littorals, the equivalents of the Richmond and Bowden, and 

 classified with the Coast Limestone all the limestone formations from the INIont- 

 pelier to the elevated reefs inclusive. Furthermore, tliese errors upon his part 

 have led to some very broad generalizations which are utterly untenable. 



Of tliese writers Gabb has given by far the largest and oftenest quoted report, 

 while Tippenhauer gives the latest and best general summary (Die Insel Haiti, 

 Leipzig, 1893). The recent researches of Bergt, noted on a later page, alleging 

 the possible existence of an older plexus of Pre-Cretaceous rocks were not pub- 

 lished at the time of Tippenhauer's contribution. While Tippenhauer's age con- 

 clusions are not always reliable, the sequence which he gives of the rocks is the 

 first logical presentation thereof, and presents a remarkable analogy to the general 

 Jamaican sequence as set forth by us, as will be seen by the section on page 172. 



1 Topography and Geology of San Domingo, p. 83, and unpublished manu- 

 script in the library of the U. S. Geological Survey. 



2 Kongl. Svenska Vetenskaps-Akademiens Handiingar, Bandet 9, No. 12, 1870. 



3 Geology of the Northeastern West Indian Islands, 1871, p. 4. 

 * Ibid., pp. 14, 15. 



