L. V. Pirsson — Geology of Conanicut Island. 367 



silver-gray to varieties dark chocolate to black in tone. The 

 light varieties are well exposed along the eastern shore as at 

 Potter's Point where the dark varieties also occur in thin beds. 

 The darker varieties occur also along the shores of Mackerel 

 Cove. Frequently the two are interbedded in extremely thin 

 layers but an inch or so in thickness, which cut across at an 

 angle by the planes of cleavage gives a peculiar ribboned 

 appearance to the outcrops, this being well shown along the 

 east shore of Mackerel Cove in B 5, fig. 2. The dark shales 

 sometimes contain small garnets in vast numbers and some- 

 times staurolite, while the green shales do not as they are 

 deficient or wholly wanting in lime as shown by the analysis 

 given later. There are also at X, fig. 1, a few outcrops of a 

 pudding stone or rather coarse conglomerate and also of some 

 micaceous sandstones. 



When we attempt, however, to unravel the stratigraphy of 

 these beds we are met by great difficulties ; as before said, there 

 are no outcrops except at the shores; here however, with few 

 exceptions, they are either exposures of the planes of slaty 

 cleavage on which the strike of the beds may be seen but from 

 which their dip cannot be determined, or of such a nature that 

 neither strike nor dip can be told. In general, so far as can be 

 made out, the strike of the beds on Conanicut is north and 

 south and the dip east. Along the shore from the ferry to 

 Potter's Point, the strike is nearly north and south — the dip 

 cannot be safely told ; at Potter's Point the strike changes with 

 a short radius and runs out under the water in a northeast 

 direction. At this point a large number of small faults with 

 small displacements can be seen. Along the Beaver-tail por- 

 tion of the island the strike is about north and south, the dip 

 which varies considerably to the east. The same is true along 

 the east shore of Mackerel Cove the dip varying from 10°-30° ; 

 at a point nearly at the top of B 5 there is a small but excel- 

 lent exposure which shows the beds bent into a half circle with 

 radius of little more than a foot, the convex side to the east ; 

 this must have been an overfold and gives evidence of the 

 great amount of distortion the beds have suffered. At X, fig. 1, 

 an excellent exposure of the rocks 

 is found. A section at this point 

 from the water's edge to the bank 

 under which the rocks disappear is 

 given in fig. 3. The strike is 

 north and south, the dip east. At 

 this point along the shore the dip 

 may be seen to have great varia- 

 tion. The cleavage is parallel to 

 the bedding and the beds have 



1 Conglomerate. 



2 Black fissile shales. 



3 Micaceous sandstone. 



4 Shales. 



