GEOLOGY OF THE PROVINCES OF BARAHONA AND AZUA. 223 



La Vigia, a ridge of hard, gray limestone about 300 meters high. No 

 fossils were found in this limestone, but its topographic prominence and its 

 lithology indicates that it is of early Tertiary age. 



The character of the Miocene sandy beds and early Tertiary limestone is 

 well shown along Rio Via north of Azua, where the following notes were 

 made by Doctor Cooke: The "old series," of Eocene or Oligocene age, is 

 exposed near the second waterfall above Azua, about 5 kilometers from 

 that town, where there is a massive bed of limestone conglomerate, probably 

 not over 15 meters thick, containing pebbles of greenish rock. Super- 

 imposed on this bed is a thicker massive blue-gray limestone containing 

 thin beds of shale. The rocks are greatly sheared and are cut by minor 

 overthrust faults, and the entire section is repeated by a larger overthrust 

 fault. The strike, although variable, is in general northwest, and the dip 

 varies from vertical to northeast. 



Downstream from the "old series," and apparently dipping beneath it, 

 there is a massive conglomerate, composed chiefly of limestone pebbles, 

 which grades southward into conglomeratic sandstone interbedded with 

 clay-shale, the relative proportion of the clay shale increasing toward the 

 south. About one kilometer from Azua there is a vertical bed of yellow 

 nodular coraliferous limestone, the fossils in which are undoubtedly of 

 Miocene age. (See list on pp. 157-158, station 8664.) These beds gen- 

 erally dip north or northeast at a high angle and exhibit many small faults. 

 The sequence of strata found here suggests that the beds may be overturned. 



The Azua Oil Field. 



GENERAL FEATURES. 



The so-called Azua oil field is about 4 kilometers northwest of the town, 

 at a place known as Higuerito. The seepage of oil and the salt springs 

 at this place have been known for a long time and have in recent years 

 attracted the attention and commanded the efforts of many exploiters. Six 

 holes have been drilled, several of which produced some oil. The land is 

 within a concession now owned by the Santo Domingo Investment and 

 Development Co., which is continuing the exploratory work. There is con- 

 siderable difference of opinion as to the results obtained in the earlier wells. 



The rock near the principal oil seep consists of conglomerate, coarse 

 sandstone, and sandy shale, all sparingly fossiliferous. The conglomerate 

 contains fragments of branching corals that suggest forms found to the 

 west, in the lower strata of the Miocene deposits along Rio Yaque del Sur. 

 The beds exposed here closely resemble the Miocene beds exposed near 

 Quita Coraza, along Rio Yaque del Sur, and their Miocene age is shown by 

 the fossils in the richly fossiliferous strata in the same series to the south- 

 east, along Rio Via. The topography of the areas near the seepages is 



