166 GEOLOGY OF THE NARRAGANSETT BASIN. 



blocks too small for building purposes. (See fig. 19.) This zone of jointed 

 rock widens from not more than 2 feet at the present surface to 10 or 12 

 feet at a depth of 20 feet. 



Section from Watchemocket Cove to Riverside. The 1'Ocks which appeal' ill the qUai*- 



ries above described come to the seashore in bold cliffs between Watche- 

 mocket Cove and Riverside, and in a few places the natural section has 

 been made clearer by railway cuts. About 100 feet in thickness of Carbon- 

 iferous sandstones, conglomerates, and shales are exposed along this section, 

 in the form of a broad, flat syncline from Watchemocket Cove to near Pom- 

 ham Rock, where the strata become vertical and are much disturbed, at one 

 point the sandstone beds having been reduced to breccia. The strata just 

 south of Silver Spring form terraces overlooking the bay. Northeastward 

 from Pomham Rock and Riverside the same strata are seen inland in the 

 three ridges indicated on the topographic map. In the eastern one of 

 these long, low ridges, the sandy conglomerates dip northwestward at a 

 very low angle, but the strata in the westernmost of the ridges dip steeply 

 east, being along the line of the Pomham anticline. Northeastward, at a 

 point about a mile due east from Vue de 1' Eau, the strata turn more to the 

 eastward, as if in the canoe end of a syncline. (See fig. 20.) 



Fig. 20. — Geological section from Watchemocket Cove to Riverside, Rhode Island, showing the attitude of the Carbonifer- 

 ous strata. A, Kettle Point; B, Squantum; C, Silver Spring; D, Pomham Rock; E, Riverside; F, Outcrop near 

 Sherman Station. 



South of Riverside the rocks are not well exposed. The details of 

 stratigraphy along this shore are sufficiently illustrated in the following 

 notes: 



Halsey Farm section at Silver Spring. A few rods SOUtll of Silver Spring Station 



the following section was measured in the bluff at Halsey Farm: 

 Section in bluff near Silver Spring Station, Rhode Island. 



Feet. 



Sandstone and conglomerate (at top) 40 



Conglomerate with pebbles of quartzite and granite 6 



Sandstone (to bottom) 4 



These strata are approximately horizontal, but farther east they dip 

 eastwardly, and westward across the railroad track they dip as high as 



