1G2 



(m THE TOrOGI^APIlY AND (JEOLOGV 



CHAPTER X. 

 Geology of the monte cristi kange. 



The Monte Cristi range occupies about half the area covei'ed hj the Miocene 

 rocks, and although it shows these strata bent and cut through in innumerable places 

 by deep canons, it gives us no new facts relative to them. Deposited further otf 

 shore, although probably not in much deeper w^ater, its rocks are nearly devoid of 

 fossils, and except in the highest bed where a few foraminifera serve to identify 

 them, they might be searched from one end of the i-angc to the other without yielding 

 positive evide]ice of their geological age. This is partly due also to the fact that the 

 blue shale from which the greater part of the fossils is obtained changes its lithological 

 character somewhat, and does not seem to have been at the time of its deposition so 

 favorable to the existence of mollusca life. But this can only account in part for the 

 absence of fossils, because the superjacent beds, lithologically identical with those 

 nearer the ancient shoi'e, are equally or almost as barren. Among the large collections 

 of these objects made diu-ing the progress of our work, almost the only ones obtained 

 north of the valley were a few corals and mollusca from the hill of Monte Cristi and 

 from the little adjoining island of Cayo Publico. I found a few very imperfect 

 fragments of small ci'ustaceans in the shale near Limon ; but elsewhere over the 

 more than a thousand square miles examined, no other fossils were discovered by 

 either my assistants or myself. 



Fortunately the rocks retain their general lithological characters so well preserved 

 that there is no difficulty in identifying any part of the formation, and the structure 

 of the chain is so simple that the labor of deciphering the various sections is com- 

 paratively trifling. Although there is no heavy folding or great disturbance in the 

 range, there is a marked difference in all the sections I have been able to make out 

 across it. There is no one well-deflned anticlinal axis or single line of upheaval. The 

 elevating force seems to have acted simultaneously under the entire mass, but with 

 various degrees of intensity in the middle or at either margin. Monte Cristi is raised 

 vertically almost a thousand feet. Thirty or forty miles east all of the force was 

 expended on the northern margin; north of Santiago it acted most markedly near the 

 middle, while north of Moca- ihe southern edge alone is disturbed ; and again north 

 of Macoris, the greatest upheaval took place north of the summit of the range. AYest 

 of Puerto Plata the metamorphosed cretaceous slates reach the surface, lifting the 



