64 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



more closely than it resembles the Tabera formation. Its softness and 

 lack of alteration and its comparatively slight deformation suggest an age 

 considerably later than that of the Tabera formation. 



The relations of the Cevicos limestone to the basalt that forms the 

 Loma de los Palos have not been ascertained, but it seems probable that 

 the limestone is younger and was deposited upon the basalt. Wherever 

 beds of limestone have been observed they are very nearly horizontal, 

 although they probably slope gently northward or northeastward. The 

 massive reef-limestone that covers the Cevicos limestone to the north is 

 evidently younger, but whether the reef was deposited conformably upon 

 the Cevicos limestone or whether there is a stratigraphic break between was 

 not determined. 



In the bank of Arroyo Blanco outcrops of creamy yellow limestone, 

 nodular on weathered surfaces, extend 12 to 15 meters above water level. 

 The bedding is indistinct but appears to be nearly horizontal. Softer and 

 more argillaceous nodular limestone is exposed at about the same altitude 

 in the banks of Arroyo la Mora about 1.5 kilometers east of Arroyo Blanco. 

 This bed contains numerous casts of mollusks, including species of Area, 

 Cardium, and several venerids. The only fossils collected in which the shell 

 substance is preserved are a species of Ostrea and a crushed specimen of 

 Brissopsis antillarum Cotteau. Yellow nodular limestone containing 

 mollusks, corals, and Foraminifera is exposed to a thickness of less than 

 2 meters on the east side of Arroyo Barranca, the first arroyo northeast 

 of Cevicos on the road to Villa Rivas. It is overlain by 12 to 15 meters 

 of yellow loam. Similar rock containing a Pecten, apparently a variety of 

 Pecten vaun Cooke, and other fossils was found on both sides of a 

 stream supposed to be Arroyo Jerguen. The fossils from all these localities 

 are listed on page 110. 



Either the Cevicos limestone or formations similar to it extend eastward 

 for a considerable distance. According to Mr. Ross the south shore of 

 Samana Bay as far east as San Lorenzo Bay is made up of massive pink to 

 white cavernous limestone similar in general appearance to the coral-bear- 

 ing limestone overlying the Cevicos limestone and perhaps identical with 

 it. This rock forms a level plateau like that south of Villa Rivas and 

 probably about as high. According to Gabb * the summit of Loma de los 

 Muertos, 10 kilometers south of Sabana de la Mar, is capped with thick 

 horizontal beds of limestone similar to that near Cevicos. 



In the southern part of the island limestone containing corals of upper 

 Oligocene facies is exposed in the slopes and foothills of Monte Calabaza 

 near San Cristobal and at a place 24 kilometers from Santo Domingo City 

 on the road to San Cristobal. Precise data on the localities and lists of the 

 fossils are given on page 112. 



1 Gabb, W. M., On the topography and geology of Santo Domingo: Am. Philos. Soc. Trans., vol. 15 

 n. s., p. 148, 1873. 



