L. V. Pirssoii — Geology of Conanicut Island. 369 



interspersed with quartz and feldspar often in micro-pegmatite 

 intergrowth. This grows coarser in grain and a few yards to 

 the south the granite outcrops again. 



Also in D 5 occurs an apophysis which has been thrust out 

 into the sedimentaries. Its outcrops occur along and in the 

 road for a distance of some fifty feet or more and recent work 

 on the road has thrown out some fresh material. This is a 

 line grained light reddish rock and microscopic examination 

 shows it to be a most characteristic and typical micro-pegma- 

 tite. From this point farther to the westward there are no 

 evidences of endomorphic contact in the granite ; it is either 

 covered or the rocks have suffered so from pressure and weath- 

 ering that nothing certain can be deduced. 



ExoinorpMc contact phenomena. — As will be seen by refer- 

 ence to the map, the region of the sedimentaries which has 

 been chiefly affected by the intrusion of the granite is a 

 roughly triangular mass lying in great part, in D 5 and E 5. It 

 is not however the only place where exomorphic evidences of 

 contact are shown. It may be said at this place that every 

 transition can be found between unaltered shales and the most 

 solid of hornstones in contact with the granite, but not how- 

 ever in any one place or exposure. Along the west shore of 

 Mackerel Cove the shales although nearly normal are yet some- 

 what affected having a strongly knotted and speckled look, de- 

 scribed by Dale* as containing " thickly disseminated minute 

 nodules of siderite.'' They often do indeed contain carbo- 

 nates but also at other times small nests of intertwined white 

 mica leaves, secondary quartz, chlorite, etc. It would appear 

 at times as if they might have been pseudomorphs of some 

 former mineral and the whole phenomenon is indeed strongly 

 suggestive of contact metamorphism. In C 4 in the gully cut 

 by the little brook and just west of the new road, green shales 

 or phyllites are found which are very near the normal, the 

 only alteration noticeable being a slight loss of the fissile 

 character together with a somewhat gnarled appearance and 

 the formation of small knotted points. In the ]N".W. corner 

 of D 5 just south of Mr. Green's barn occurs a long outcrop 

 extending towards the south. At the north end the shales 

 although still retaining a fissile character are very much 

 gnarled and toughened and as one proceeds southward they 

 pass within two or three rods into compact hornstones. From 

 this exposure it may be seen that the loss of the shaly charac- 

 ter and transition into hornstone occurs within a very short 

 distance. 



Along the east shore in E 6 the transition is covered and the 

 first outcrop after leaving the shales is a dense slaty rock of a 



* Loc. cit. 



