66 NEW YORK STATE MUSEUM 



SUMMARY 



The conclusions obtained in the preceding paper are : 

 i The lower part of the black shale belt of the lower Mohawk 

 valley hitherto referred to the Utica shale is of Trenton age and 

 therefore here distinguished as Canajoharie shale from its typical 

 outcrop at Canajoharie. The Canajoharie shale corresponds 

 roughly to the lower and possibly middle Trenton of Trenton Falls 

 and probably belongs in large part between the two. It disappears 

 westward and is eastward cut off by the Hoffmans Ferry fault, but 

 reappears north of Schenectady from under the Schenectady beds 

 and eastward in the folded shales of the Hudson valley, where it 

 is recognized in the Rural Cemetery beds, formerly referred by the 

 author to the Magog shale of Canada. This belt can in the Hudson 

 valley be followed northward through Saratoga county to Hudson 

 Falls, where it rests on Glens Falls (basal Trenton) limestone. 



2 The typical Utica shale seems to disappear entirely as it 

 approaches the Hudson valley, probably through nondeposition. 



3 The Frankfort shale is absent in the lower Mohawk valley. 

 The shales, hitherto referred there to the Frankfort formation, are 

 of older age. The Frankfort formation, in its restricted conception, 

 soon disappears to the east of the type section near Utica, probably 

 by overlap, and does not seem to have at all extended into the Hud- 

 son and Champlain valleys. According to its meager faunule it 

 corresponds to the middle division of the Eden shale at Cincinnati 

 and it may also include the upper Eden. 



4 The so-called Frankfort beds of the lower Mohawk have fur- 

 nished a large fauna that is very distinct from that of the Frankfort 

 shale. Its most striking elements are the eurypterids and the sea- 

 weed Sphenophycus, but it also contains a number of species that 

 indicate that it can not be younger than upper Trenton age and 

 probably belongs mainly below the upper Trenton. Since these beds 

 are connected by transitional beds with the underlying Canajoharie 

 shale of lower and middle Trenton age, the inference of their middle 

 and upper Trenton age is also supported by the stratigraphic rela- 

 tions. The formation is therefore here given a new name, the 

 Schenectady formation. This formation attains a great thickness 

 (approximately 2000 feet) in the lower Mohawk region, but does 

 not extend far westward and ends abruptly eastward against the 

 folded region. It is characterized by numerous intercalations of 

 " bluestone," a calcareous sandstone, by mud-cracks, rapid horizontal 

 alteration of sediments and other features which indicate nearness 

 of the coast. This coast was probably to the east and the great 



