Ailing — Problems of Adirondack Precambrian. 67 



camptonite, fractured longitudinally to allow a second 

 and later dike of hornblende camptonite to intrude. 

 This was about 3 feet wide. This in turn split to allow a 

 third dike to sandwich its way in. This is a typical bos- 

 tonite dike 2 feet in width. Each dike has developed chill 

 phases upon its neighbor; a narrow contact zone of 

 several inches occurs between the porphyritic diabase 

 and hornblende camptonite. A more ideal exposure to 

 show the age relations of the dike rocks cannot be 

 imagined. 



The Age of the Faulting in the Adirondacks. 



It has impressed the writer that the faults are not all 

 of the same age. With such complex geology as is shown 

 in the region it would seem remarkable if the faults had 

 been contemporaneous. Positive proof of various ages 

 was secured in the Saratoga sheet on the property of the 

 Graphite Products Corporation, 4 miles north of Sara- 

 toga Springs. The graphite schist occurs as two (and 

 possibly as three) outcrops due to repetition by faulting. 

 The fault lines run east and west, which are abruptly 

 cut off by the north and south fault (McGregor fault) 

 that brings the Canajoharie shale in contact with Gren- 

 ville. Thus there is post-Grenville-pre-Cambrian fault- 

 ing as well as that occurring since Cambrian times. A 

 mile south of the town of Saranac, one of the unusual 

 gabbroic dikes has re-cemented a fault zone in the anor- 

 thosite; engulfing brecciated fragments as xenoliths 

 demonstrating pre-gabbroic dike faulting. "When the 

 region is made the subject of a serious physiographic 

 study the relative ages of the faults should be kept in 

 mind. 



Summary. 



The following points were brought to light or empha- 

 sized during a detailed investigation of the Adirondack 

 Graphite Deposits during 1917 and 1918 : 



1. That the Grenville strata have been extensively 

 isoclinally folded. 



2. That the stratigraphic units formerly proposed in 

 attempting to put the Grenville in order are too large, 

 but when smaller units and the graphite schists are taken 

 as a basis, then it is possible to do something with the 



