GEOLOGY OF SARATOGA SPRINGS AND VICINITY 99 



The fossils which are most frequently met with in the shales 

 are : the graptolites Corynoides gracilis, Dicrano- 

 graptus nicholsoni, Diplograptus amplexi- 

 caulis, D. amplexicaulis var. pertenuis, Clima- 

 cograptus spiniferus, and the little gastropod A r c h i - 

 nacella orbiculata and little lamellibranchs of the genera 

 Clidophorus and Ctenodonta, while the limestone and grit bands 

 contain the brachiopods Dalmanella testudinaria, 

 Plectambonites sericeus, fragments of Rafinesquina 

 and crinoid joints. Rarely a larger fauna of mollusks and trilobites 

 occurs, as at Snake hill, and some places in Albany county. Also 

 worms similar to those described from the Canajoharie shale are 

 frequently seen. 



The frequent occurrence of Dicranograptus nichol- 

 soni typus which is not found in the Normanskill shale, appears 

 to us especially characteristic of this formation, especially about 

 Saratoga lake, while Lasiograptus eucharis, which is 

 extremely common in the Canajoharie shale, is here less frequently 

 met with. 



Correlation. From the fauna of the Snake Hill beds it can be 

 inferred that the formation is of early Trenton age and roughly 

 corresponds to the lower and perhaps part of the middle Trenton. 

 It probably rests upon the upper division of the Normanskill shale 

 and is the youngest of the rock formations of the Levis basin that 

 by overthrusting and intensive folding have been pushed westward 

 into contact with the formations of the Mohawk-Champlain basin 

 (see diagram, page 140). 



STRUCTURAL GEOLOGY OF THE SHALE BELT 

 BY R. RUEDEMANN 



The principal structural feature of the shale belt of the two 

 quadrangles finds its expression in the contrast of the flat-lying 

 or but slightly dipping shales of the western trough and the in- 

 tensely folded and crumpled condition of all the rocks east of this 

 belt. 



The boundary line between the folded and flat shale areas co- 

 incides very nearly with that between the Canajoharie and Snake 

 Hill shales, not only on the two quadrangles here described, but in 

 the entire inner lowland extending from the Helderberg cuesta 

 to the Adirondacks and then into the Champlain basin and presum- 

 ably farther north. It docs not coincide exactly because in some 



