130 J. W. SPENCER — RECONSTRUCTION OF ANTILLEAN CONTINENT. 



fayette formation, which supplied materials for the newer deposit, which 

 is like the Zapata. The fossiliferous sands and the coquino found in the 

 wells of Saint Augustine, and some marls in southern Florida, are prob- 

 ably of Columbia age, distantly removed from the source of the non- 

 fossiliferous red loams, which were rapidly laid down nearer the sources 

 of mechanical materials. 



In the Antilles geologists have not hitherto (Geographical Evolution of 

 Cuba) differentiated the Zapata formation. Gabb includes it with his 

 post- Pliocene " coast limestone " of San Domingo. In Jamaica it is sim- 

 ply called the " alluvium " or the " older alluvium," although in both 

 islands it is from 200 to 300 feet thick. Its position and specialization on 

 the continent were largely the result of the classic labors of Mr. W J 

 McGee, who has surveyed it from New Jersey to Mexico. The geologic 

 forces acting on this widespread formation have progressed quietly over 

 an enormous area of the continent and the Greater Antilles, and in the 

 Lesser Antilles it may, perhaps, be found represented by limestones in 

 places and by clastic deposits in others. The absence of great elevation 

 (probably nowhere exceeding 700 feet or 800 feet) further convinces the 

 writer that the continental oscillations were becoming moderately uni- 

 form over a very great area, and this reduces the geology to simplicity ; 

 but in the mid-Pleistocene subsidence which lowered the Antillean 

 continent, the ridge of Central America became prominent — an undu- 

 lation of less than one degree, including orogenic movements, being 

 sufficient. 



Whether the Zapata formation extends over the divides in Central 

 America or not is an important question, for that settles the date of the 

 final separation of the Pacific waters from the Antillean seas, but the 

 gravels filling the old valleys in Nicaragua, according to Mr J. Crawford^ 

 occur up to altitudes of 500 feet, and it is not improbable that they are of 

 the same age as the Zapata deposits. Under any circumstances, the con- 

 tinent was lost from the date of the Zapata subsidence, which was in the 

 mid-Pleistocene epoch. 



Reelevation of the Lands at the close of the Pleistocene Period. 



From the Zapata subsidence the Antilles rose from 150 to 200 feet above 

 the modern altitude. Then the streams cut out canyons to the depths 

 named, and made many new outlets to the bays, excavated in part out 

 of the Matanzas limestones, but closed by the Zapata loams and gravels. 

 This elevation somewhat enlarged the land area, and increased it to about 

 the proportions shown on the shaded portions of the accompanying map. 

 The Bahamas formed two or three large islands, but neither these nor 



