12 NEW YORK STATE MUSEUM 



Canada, but nothing is really known about the lands from which 

 they were derived by weathering and erosion. Measurements have 

 shown that the Grenville series is very thick — some miles at least. 

 A remarkable feature of the strata is the presence of numerous 

 flakes of graphite in certain of the layers. Graphite (crystallized 

 carbon) which occurs under such conditions is quite certainly of 

 organic origin, and thus we may be sure that organisms of some 

 kind, probably very primitive t}^es, must have inhabited the waters 

 in which the Grenville strata accumulated. 



Description by areas. Areas in the town of Thurman. The 

 largest displays of Grenville within the quadrangle occur in the town 

 of Thurman where there are five areas of small size, as indicated 

 on the accompanying geologic map. Largest of all is the area of 

 about I square mile in which the village of Athol is located. Judg- 

 ing by the exposures, much of this Grenville is crystalline limestone 

 closely involved with other metamorphosed strata. Of special in- 

 terest are the big exposures of limestone a little below the bridge 

 at the southern end of Athol village. Number Nine creek has there 

 cut a small gorge into the limestone. At one place an opening, 

 known as " The Cave " by the inhabitants for miles around, is per- 

 haps 20 feet wide near the creek level. It has been formed by the 

 erosive and dissolving effect of water upon the limestone. Above 

 the road a little east of the bridge another cave with two small open- 

 ings lies along the contact of limestone and granite, the latter rock 

 forming the roof. In this case the weak limestone has been dis- 

 solved out from under the resistant granite. The limestone of this 

 vicinity is medium to moderately coarse-grained, usually with grains 

 of green pyroxene and scattering flakes of graphite. Due to con- 

 siderable pressure upon the plastic mass during the intrusion of the 

 granite, the stratification is more or less obscure and notably con- 

 torted, while thin layers of green pyroxenic gneiss have been 

 mostly pulled to pieces giving the appearance of inclusions in the 

 limestone. A few small dikes of granite, pegmatite and silexite cut 

 this limestone. Similar limestone outcrops by the road in the west- 

 ern part of the village. In the bed of the creek in the northern 

 part of the village there is a big ledge of crystalline limestone rich 

 in pyroxene and graphite directly associated with considerable 

 hornblende-garnet gneiss, the latter evidently representing original 

 shale which has been thoroughly metamorphosed. 



Interesting exposures occur in the vicinity of the road corners 

 just west of Athol. Within an eighth of a mile both north and 



