GEOLOGY AND GEOLOGIC HISTORY. 53 



northward. On the descent toward La Cruz bedded tuffs, somewhat 

 copper-stained in places, strike N. 35° E. Near La Cruz there is siliceous 

 tuff, which dips steeply south west ward. A few kilometers beyond La 

 Cruz there are tuff and impure limestone, which dip very steeply eastward. 

 About 1 kilometer farther on shale and sandstone stand vertical or dip 

 steeply westward. Similar rock occurs between this point and Joca. 

 Near Guayajayuco there are many minor flexures, but the general strike of 

 the beds is N. 50° W. The rock in the gorge of Rio Guayajayuco where 

 first seen is flaggy blue sandstone. Farther downstream there is a slaty 

 shale, which weathers to gray splintery rock of schistose appearance. The 

 beds strike N. 35° W., and stand vertical or dip eastward at a high angle. 

 The trail passes over greenish shale for several kilometers and then again 

 descends into the river canyon. Here the rock resembles dark-blue veined 

 and sheared slate, in which most of the veins run at right angles to the 

 slaty cleavage. The rock is similar to the blue phyllite on Rio Yaguajal 

 near Sabaneta. Loma Vieja is composed of the same kind of rock. The 

 slaty cleavage on its north slope strikes N. 40° W., approximately at right 

 angles to the bedding. Near the highest point reached on the trail the 

 cleavage strikes N. 50° W. and dips 60° E., but the bedding strikes north 

 and dips 30° W. At a point on the southwest slope the bedding strikes 

 N. 30° W. and dips 70° W. On the lower part of this slope and in the valley 

 of Rio Joca the rock is a bluish quartzitic slate containing thin layers of 

 limestone, which is in part recrystallized into rather coarse-grained marble. 



SAMANA PENINSULA. 



Rocks of the basal complex make up the greater part of Samana Penin- 

 sula. The rocks seen in place in this area are micaceous schists and schis- 

 tose limestones, but pebbles of pegmatites, felsites, and other igneous rocks 

 included in younger conglomerates probably had their source somewhere on 

 the peninsula. The predominant rock on the south slope of the moun- 

 tains is hard, fairly pure, moderately schistose limestone. Some of the 

 rock on the top of Loma las Cafiitas at Sanchez is marble. The strike of 

 the schistosity of all the formations in the basal complex is in general east, 

 parallel to the trend of the peninsula. 



CRETACEOUS SYSTEM. 



Rocks of Cretaceous age are supposed to make up a large part of the 

 basal complex, but they have not been discriminated from formations that 

 may be older. Gabb 1 collected a few poorly preserved fossils from earthy 

 pebbly limestone at two localities on Rio Nigua, probably somewhere 

 between San Cristobal and Santa Maria, but he does not give the exact 

 localities. As the species collected by Gabb include such characteristically 



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

 n. s., pp. 86-87, 1873. 



