GEOLOGY OF SARATOGA SPRINGS AND VICINITY 49 



for the most part. Its uniform, carbonaceous, fine grained char- 

 acter is the most distinguishing feature of the formation. 



Much of the shale contains pyrite which, becoming oxydized, fills 

 the cleavage and bedding planes in some places with rusty brown 

 films and produces efflorescences of alum salts on the protected walls 

 of clifTs, as about Ballston Spa, and is probably also responsible for 

 the occurrence of sulphuretted hydrogen in some of the springs. 

 In some cases the graptolites were found very well preserved in 

 pyrite. 



These shales are fiat on the two quadrangles here described, and 

 are not involved in the intensive folding and overthrusting that has 

 affected the Georgian, Normanskill and Snake Hill beds, although 

 they may dip steeply near the fault planes. Owing to their uniform 

 softness and fiat position, they have not only been very deeply 

 eroded but also fail to form ridges of folded harder beds, as the 

 other shale formations of the region do. Outcrops are therefore 

 extremely scarce in the entire belt, occurring only where the creeks 

 have accidentally reached a higher part of the shale surface, that 

 for the most part is deeply buried under drift. Since practically 

 every outcrop of this shale is fossiliferous, most outcrops are marked 

 on the map as fossil localities. 



On the Saratoga quadrangle the most important outcrops are 

 a])out Ballston Spa where the Kayaderosseras fiows between cliffs 

 of this shale loo feet high. A few small outcrops sufficient to 

 demonstrate the areal extent of the formation were observed in 

 the bed of the Glowegee and its branches, in the southwest corner 

 of the Saratoga map, and another in the creek bed at the Geyser 

 and Carlsbad springs 2 miles southwest of Saratoga Springs. Thence 

 northeastward all rock is hopelessly buried under sand until the 

 Snook kill is reached, which in its upper branches exposes shale 

 cliffs at the foot of Mt McGregor and falls and flows over Cana- 

 joharie rock for several miles north of Gansevoort. It again reaches 

 bedrock about 4 miles above the mouth of the creek. 



The thickness of this formation could not be determined in the 

 area here mapped from the facts at hand. We know, however, that 

 not more than 15 miles to the southwest it is not less than iioo feet 

 and there is no reason why it should originally have greatly di- 

 minished toward Saratoga county, this direction lying in line with 

 the probable axis of the trough in which deposition took place. 

 Since, however, the shale in this region was earlier uncovered by 

 erosion than the belt at the foot of the Helderberg escarpment, it 



