INTRODUCTION. 15 



OUTLINE OF RESULTS. 



PHYSIOGRAPHY. 



The major physiographic subdivisions of the Republic were ascertained, 

 and they are systematically described in Chapter III and are mapped on 

 Plate I (opposite p. 26). This work has never been done before. Gabb's 

 description of the topography of Santo Domingo l contains much infor- 

 mation, but it is not presented in a way to bring out clearly the relations 

 between the different features. 



STRATIGRAPHY AND GEOLOGIC CORRELATION. 



Prior to the reconnaissance of 1919 the only geologic formations in the 

 Dominican Republic that had been recorded consisted of beds of Cretaceous, 

 Miocene, and post-Pliocene age. Doctor Carlotta J. Maury, as a result of 

 her investigations in the valley of Rio Yaque del Norte, discriminated there 

 two Miocene formations, the Cercado and Guarabo formations, and pro- 

 posed for them the only two definite names that had been applied to Domi- 

 nican geologic formations. Our examinations have probably yielded 

 knowledge of at least most of the major stratigraphic units, but the basal 

 complex must be more closely studied before it can be clearly understood. 

 It certainly includes rocks of Cretaceous age and probably rocks of pre- 

 Cretaceous age. We obtained additional data on the Cretaceous system 

 and are able to correlate the formation exposed near Sabaneta with the 

 Upper Cretaceous of Cuba, Jamaica, and other islands of the West Indies. 



Among the important additions to knowledge made through the recon- 

 naissance are the recognition of a great thickness of upper Eocene deposits, 

 mostly limestones, the discovery of deposits of both middle and later 

 Oligocene age, and the discovery of an unconformity between the Miocene 

 Baitoa formation and the underlying middle Oligocene Tabera formation. 

 Four additional Miocene formations were recognized in the Cibao Valley, 

 and a late Miocene formation, the Cerros de Sal formation, was discrimi- 

 nated on the north side of Sierra de Bahoruco. Some other additions were 

 also made to the knowledge of the stratigraphy. 



The geologic correlation of the formations in one part of the Republic 

 with those in other parts and with those in other regions must depend 

 principally upon a knowledge of the remains of the organisms they con- 

 tain. The preliminary lists of fossils given in Chapter VI show what was 

 accomplished in acquiring knowledge of this kind, which is not only 

 needed for geologic correlation, but is of great value in solving some 

 problems of economic geology. More detailed investigations of the fossils 

 than has yet been practicable will undoubtedly yield a larger amount of 

 valuable information than that contained in this volume. 



1 See Bibliography, p. 18. 



