232 GEOLOGY OF THE I^ARRAGANSETT BASIN. 



SOUTHERN HALF OF THE ISLAND, SOUTH OF ROUND SWAMP. 



SHALE BEOION. 



The most northern outcrop of the Conanicut shales is in a small 

 embayment north of Potters Cove, about 1,800 feet south of the old ferrj^ 

 They are here very thin and fissile. They are again exposed for quite a 

 long distance along the northern part of Potters Cove. At its southern 

 extremity, and thence all around the margin of Freebodys Hill and beyond 

 Jamestown Ferry, there is an almost continuous exposure, the outcrops 

 ceasing about half a mile south of the ferry point. At Taylors Point the 

 shale contains quartzitic layers. If these are original interstratified sandstone 

 layers there has been much lateral crumpling. Nevertheless, the beds show 

 a generally low dip. Along the eastern shore of Freebodys Hill there is 

 distinct color banding, accompanied by considerable crumpling. The most 

 northern of the outcrops of the shales along the western shore lies within 

 half a mile north of the western Jamestown ferry. Thence outcrops occur 

 at more or less frequent intervals as far as the marshy land, a short distance 

 south of the western ferry; then, after a short interval, along the eastern 

 shore of Mackerel Cove. Shales occur again a third of a mile south of the 

 western ferry, along the southern margin of Dutch Island Harbor, on the 

 northern edge of the southern half of Conanicut, east of the pond near 

 Fox Hill. South of Fox Hill they occur again at the end of a beach about 

 a sixth of a mile long. Here they are very glistening and are filled with 

 some ferruginous mineral, not closely examined in the field, but probably 

 pyrite. Thence the same shales are found around the entire margin of this 

 part of the island, around Beaver Tail Head, thence northward into Mack- 

 erel Cove to its northern extremity, and thence from the eastern end of the 

 sand bar connecting the two parts of the island, down the eastern side of 

 the cove, to a point where a small stream enters the cove. 



Two minette dikes cut the Conanicut shales in the southern half of 

 the island. One dike extends from the northern side of Hulls Cove to the 

 northern edge of Austins Hollow ; the other extends from Lions Head to 

 the Southern edge of Austins Hollow. 



The color of the Conanicut shales is somewhat variable. Where dry 

 and long exposed to the action of weathering they are lighter in color, 

 verging toward greenish, with a tint of blue or brown; where wet they 



