54 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



Mesozoic molluscs as a Trigonia, an ammonite, and a baculite (?), he un- 

 doubtedly was correct in referring the bed containing them to the Creta- 

 ceous, but it seems very unlikely that all of the great variety of rocks cor- 

 related by Gabb with this fossiliferous limestone are of the same age. 

 Alberti 1 found Cretaceous fossils near Guayubin. 



East of the Azua-Bani road at Monte Mamon there are two hills, Cerros 

 los Pifiones, the backbone of which is a vertical ledge of limestone, 3 or 4 

 meters thick, striking N. 10° W. On the east side of the ledge is dark gray 

 shale. Both hills are capped by a nearly horizontal deposit of loosely ce- 

 mented conglomerate having a calcareous matrix ("caliche"). Fora- 

 minifera from one of these hills were examined by Doctor Cushman, who 

 submits the following memorandum regarding them: 



Station 8612. Very peculiar material. I have not yet been able to make out whether 

 this is Cretaceous or Eocene. If Eocene, these species are different from those of any 

 Eocene known previously in the West Indies. I have nc good Cretaceous specimens with 

 which to compaie them. 



If this rock is Cretaceous, as seems probable, much of the shale and 

 limestone exposed along Rio Ocoa below San Jose de Ocoa and in Loma 

 el Numero, which appear to be part of the same formation, is probably of 

 Cretaceous age. Limestone containing indistinct mollusks, fragments of 

 which are scattered along the ascent of Loma de Portezuela on the trail 

 from Azua to San Jose 1 de Ocoa about 200 meters above the foot of the 

 mountain, may be part of the same formation. 



Dense, hard, dark-blue banded, slightly magnesian calcareous argillite, 

 which breaks into rectangular fragments, underlies the Eocene limestone 

 in the front range of the Cordillera Septentrional near Damajagua, north- 

 west of Navarrete. As fragments of this rock are included in the Eocene 

 limestone they must at least be older than upper Eocene. This rock 

 closely resembles certain parts of the Cretaceous formations in Porto Rico 

 and the Virgin Islands and is regarded as of Cretaceous age. 



Cretaceous rocks were noted at two localities near Gurabo, in the Prov- 

 ince of Monte Cristi. The sedimentary rocks south of the village of Gu- 

 rabo probably abut against the schists in fault contact. The schist is 

 similar to that on Rio Mao above Bulla but is more metamorphosed and 

 finely banded. The following descending sequence of beds, which strike 

 N. 60° W. and dip 75° NE., was crossed in traveling southwest beyond the 

 contact with the schist: (1) reddish-brown shales, sandstone, and dark 

 gray limestone, which contain a network of white calcite seams and poorly 

 preserved fossils (station 10274; for list of fossils see p. 55); (2) limestone 

 conglomerate; (3) amygdaloidal basalt; (4) more limestone. 



The level valley floor of Arroyo Clavijo, which is about 3 kilometers 

 west of Gurabo and stands about 288 meters above sea level, is composed 



1 Alberti y Bosch, N., Apuntes para la prehietoria de Quisqueya, torn. 1, p. 27, La Vega, 1912. 



