LATER TERTIARY (MIOCENE AND PLIOCENE). 801 



successively accumulated through several geologic epochs and may ultimately be 

 classified into several distinct terranes. Hill"^^ says: 



For the present, however, we shall recognize but two principal stages — an older one, to which 

 the name of Kingston will be applied, and a newer one, which will be called the Montego. 



The Kingston formation is the oldest of the formations of old gravel and other alluvium 

 occurring upon the plains of the Liguanea type. This is the formation upon which the city of 

 Kingston and suburbs are built, including the strip of land known as the Palisades, and the 

 plain extending back of Kingston to the foot of the mountains. * * * The material con- 

 sists of bowlders, gravel, and pebble of varying sizes, usually very angular, and representing 

 every known material of the Blue Mountain series. These are embedded in a matrix of dull 

 red arenaceous clay, producing a chocolate soil and derived from the Minho beds so conspicu- 

 ously exposed in situ in the mountains north of Kingston. 



The thickness of this formation is unknown, but over 200 feet are exposed in the thalweg 

 of Hope River, and probably fully this thickness is concealed. It is even likely that it may be 

 nearly a thousand feet in places. * * * 



As a whole, it represents excessive deposition, first as estuarine or littoral material during 

 an epoch when the coasts were submerged, and later talus deposits of subsequent epochs, when 

 • the land was rapidly rising and stream erosion was very active, as discussed more fully in another 

 part of this paper. The alluvial deposits in the bottom of the larger interior basins are also 

 closely synchronous with the Kingston formation, and it is probable that these basins are 

 products of the same great erosion epoch which preceded the Kingston deposition. 



Fossils are generally missing from the Kingston formation; speculation concerning its age 

 must be founded entirely upon stratigraphical relations. In our opinion it is clearly older 

 than the elevated reefs of the Barbican and Hopewell formations, of presumable Pleistocene 

 age, and yoimger than the Bowden formation, being nearly allied by position to the age of the 

 Manchioneal, which we consider Pliocene. 



The present beds of both the Hope and the Cobre rivers deeply indent the Kingston for- 

 mation, cutting far below the surface of the plain. The alluvium of these stream valleys and 

 their general level constitute distinct deposits which are later described under the head of the 

 Montego formation. 



In his further description Hill gives many details regarding the elevated reefs 

 and miscellaneous coastal formations contemporaneous with them. 



E 19. SANTO DOMINGO AND PORTO MCO. 



Gabb ^^^^ placed the Tertiary of northern Santo Domingo in the Miocene and 

 probably that of Porto Rico as of the same age. Regarding Santo Domingo Gabb 

 says: 



All of that part of the island which lies north of the Cibao Mountains, except a part of the 

 peninsula of Samana, is made up of Tertiary rocks, usually bordered by a narrow strip of more 

 modern age. They also form one or two insignificant deposits on the south side about San 

 Cristobal and the Nizao, and are said further to cover a part or all of the valley of the lakes 

 running to Port au Prince in Haiti. The work of the geological survey not having extended to 

 the latter region I shall confine my observations to the others. 



The district covered by this formation in the north, including its extension into Haiti, 

 toward Cape Haitien on the west, and into Samana and south of the bay east, is little less than 

 150 miles long, although, cutting off these prolongations, it forms a compact area of about 100 

 miles long by 30 miles wide, or say, in round numbers, about 3,000 square miles. It abuts 

 against and even overlaps the lower foothills of the central chain, underlies the whole valley 

 of the Yaqui and Yuna, makes up the entire northern or Monte Cristi Range, and sends others 

 48011°— 12 51 



