A. J. Jukes Browne — High Continental Elevation. 561 



VI. — The Date of the High Continental Elevation of America. 

 By A. J. Jukes Browne, B.A., F.G.S. 



THE proofs of a much greater elevation of trie American continent 

 at no very distant geological date, which have been communi- 

 cated to the Geol. Mag. by Prof. J. W. Spencer 1 and Mr. W. 

 Upham, 2 are very interesting, and Mr. Upham's suggestion that this 

 great elevation occurred in Pliocene and early Pleistocene time is a 

 taking one. He thinks the culmination of the uplift coincided with 

 the Glacial period, and was to a large extent the cause of that period ; 

 if he is right, we are forced to infer that there has been a post-Glacial 

 submergence to the extent of over 3000 feet over the whole region, 

 including the Gulf of Mexico. There is, however, a difficulty in 

 this supposition, to which I beg to call Mr. Upham's attention. 



The raised coral-reefs of the West Indies indicate a recent 

 upheaval of the whole Caribbean region. In the west of Cuba these 

 reefs occur up to 1200 feet, on the testimony of Prof. Agassiz, 3 who 

 found recent species of corals in them at that height between Havana 

 and Matanzas, and up to 1800 feet near Baracoa on the testimony of 

 Mr. W. O. Crosby. 4 In Guadaloupe and Barbadoes they occur up to 

 heights of 1300 and 1100 feet respectively, while the lowest terraces 

 consist of soft and unconsolidated coral rock containing recent species 

 of shells in a fresh-looking condition. It is clear in fact that there 

 has been a regional uplift of this area to the extent of at least 

 1300 and probahly 2000 feet in Pleistocene times, and that there 

 has been no subsequent subsidence. Moreover, this area of elevation 

 certainly included Yucatan, which lies on the south side of the Gulf 

 of Mexico. 



Now if the whole North American continent, including a part 

 now covered by the Gulf of Mexico, has subsided 3000 feet since 

 the Glacial period, it is strange to find proofs of contemporaneous 

 elevation over the whole Caribbean region with a distance of only 

 400 to 500 miles between them. That there should have been in 

 such recent times a differential movement sinking the northern 

 part of the Gulf of Mexico through 3000 feet and raising its southern 

 shores through more than 1300 feet, is rather a large demand on our 

 belief. 



It is Mr. Upham who must face this difficult}', for Prof. Spencer 

 was careful not to fix the exact date of the high continental period, 

 and only speaks of its culmination "in the later Tertiary, before 

 the Pleistocene period/' Now it happens that the Caribbean region 

 affords evidence of a great depression preceding the elevation above 

 mentioned. Thus in Jamaica the " White Limestone " is in part 

 of deep-water origin, it covers a very large area in the island and is 

 regarded as being of Pliocene age. Again, the Oceanic deposits of 

 Barbadoes seem to indicate a subsidence of at least 6,000 feet, for 

 they rest on shallow-water deposits, and consist of consolidated 

 oozes comparable to those which are now found at depths of 



1 May Number, p. 208. 2 November Number, p. 492. 



3 See Tbree Cruises of tbe Blake, vol. i. p. 71. 



4 Proc. Boston Nat. Hist. Soc. vol. xxii. p. 126. 



ECDADE III. VOL. VII. — NO. XII. 36 



