1897-98]- LATE FORMATIONS AND GREAT CHANGES OF LEVEL IN JAMAICA. 343 



various age from the Tertiary, in very small part, to the Archaean, and 

 also from other rocks as well as from limestones. Although the sources 

 of the materials were so varied, yet the formation presents a remarkable 

 degree of uniformity, such as indeed arises from the decay of most 

 rocks. 



Owing to like successions in the geological scale, with the same 

 breaks above and below, the writer desires to strongly emphasize the 

 apparent equivalency in separated regions, between the Layton of 

 Jamaica, the Matanzas of Cuba, and the Lafayette of the Southern 

 States, with corresponding series in Santo Domingo and the Windward 

 Islands. The varied succession of events which has occurred since the 

 Layton epoch, places it a long way back in actual time ; and the 

 physical successions and interruptions continued alike in Jamaica, Cuba, 

 and the Southern States. 



On the continent, there are indications that some of the marine beds 

 of Florida and the Lafayette loams and gravels are of the same age, 

 but derived from different sources. Prof. W. J. McGee, the great 

 exponent of the Lafayette formations, and Dr. W. H. Dall, as well as 

 the writer, all provisionally classify the Lafayette as belonging to the~ 

 close of the Pliocene period, especially as the formation is older than 

 the glacial deposits, where first they occur in contact in New Jersey. 

 From this consideration the Layton epoch has been placed at the 

 close of the Pliocene period. The sequence of events will be better 

 understood as we proceed. But, if others prefer to regard the Layton 

 series, on account of its recent fauna, as belonging to the Pleistocene 

 period, it is physically immaterial and only suggests a greater duration 

 of Pleistocene time ; and they can transfer the author's references from 

 the late Pliocene to an early Pleistocene epoch. The submergence of 

 the Lafayette, Matanzas, and Layton epochs may have commenced a 

 little earlier in one locality than another, and also ended later, but the 

 formation seems to constitute a geological unit. 



The absence of the Mio-Pliocene formations from Jamaica, and in- 

 deed from the West Indies, followed by the Layton series, is manifestly 

 due to those general elevations preventing their accumulation, for older 

 Pliocene deposits occur on the Tehuantepec Isthmus of Mexico, which 

 should have theoretically been depressed at the time of the West 

 Indian elevation ; and such has been found to have obtained. 



