1897-98]- LATE FORMATIONS AND GREAT CHANGES OF LEVEL IN JAMAICA. 325 



LATE FORMATIONS AND GREAT CHANGES OF LEVEL 



IN JAMAICA. 



By J. W. Spencer, M.A., Ph.D. 



(Read February ^th, 18^8), 



CONTENTS. 



Introduction. 



General Topography. 



Hydrography off the Coast. 



Geological Basement of Jamaica. 



Older Miocene History. — "The White Limestones." 



The Mio-Pliocene History. — Epoch of Elevation ; The Layton Formation ; Com- 

 parison with the Matanzas and Lafayette Series and its Ag-e. 



Pleistocene History. — Epoch of Elevation ; The Lig-uanea Formation ; Com- 

 parison with the Zapata and Columbia Series. 



Modern History.^ — Epoch of Elevation ; Terraces ; Coral Reefs ; Beaches ; 

 Alluvium ; a Review of Erosion Features since the Miocene Period ; Faulted (?) Basins ; 

 Terrestrial Oscillations ; Table of the Later Geological Succession in Jamaica. 



INTRODUCTION. 



This paper has for its object the special study of erosion features and 

 the character of the later geological formations of Jamaica, and the 

 characteristics of the adjacent seas which throw additional light upon 

 the great changes of level of the region. The investigation refers only to 

 the insular region, and is a sequel to the " Geological Evolution of Cuba," 

 and " the Reconstruction of the Antillean Continent," wherein there 

 has been collected evidence of the great changes of level of land and sea 

 in recent geological times, producing mutations of the physical geo- 

 graphy of a large portion of the American continent, the consequent 

 changes in climate and the effects on the distribution of life. This 

 paper is mostly descriptive, and strongly confirms the doctrines set 

 forth in the earlier papers. 



GENERAL TOPOGRAPHY. 



Jamaica is 135 miles long with a maximum breadth of 50 miles, but 

 with slightly submerged banks increasing its width to 60 miles (Map, 



