48 NEW YORK STATE MUSEUM ' 



River age. Ruedemann has termed this Hmestone the Glens Falls 

 limestone, since its fauna has shown it to he below beds of the 

 Trenton Falls section.^ 



THE CANAJOHARIE SHALE 

 BY R. RUEDEMANN 



The Canajoharie shale is the surface rock in the southernmost 

 area of the Saratoga quadrangle and thence extends northeast, 

 occupying the area between the Snake Hill formation of the eastern 

 trough and the McGregor fault and its branches. West of Sara- 

 toga it rests directly on the basal or Glens Falls limestone and south- 

 ward the formation strikes toward the Mohawk river near which 

 it passes under the Schenectady beds. Northward from the Schuy- 

 lerville quadrangle it has not been traced beyond Glens Falls, the 

 constituent divisions of the shale belt north of the Hudson valley . 

 having not yet been differentiated. J 



This formation, which is most typically developed in the Mohawk ^ 

 valley, has been fully described by the writer in Bulletin 162. It \ 

 consists almost entirely of soft black, carbonaceous, more or less 

 calcareous, argillaceous shales and is therefore quite distinct in its 

 lithologic characters from the Normanskill-Snake Hill group, al- 

 though where it has become involved in the folding, as in 

 Albany county, it may through cleavage and slickensided 

 slip planes become quite similar to some of the darker shales 

 of the latter formations. It lacks, however, the smooth, lighter 

 colored, gray, greenish and bluish purely argillaceous shales so preva- 

 lent in them, and the black Canajoharie shale weathers a character- 

 istic light drab, like the Utica shale, while the dark shales of the 

 Normanskill-Snake Hill weather grayish brown or spotted or 

 whitish when somewhat siliceous. Nor does the Canajoharie con- 

 tain any trace of the white weathering chert beds and grit of the 

 shales of the eastern trough. A sandstone bed 2 to 3 feet thick was 

 observed in only one case in the Snook kill below Gansevoort, 

 although thinner layers of somewhat sandy shale are sometimes met 

 with. On the other hand there frequently occur harder, bluish gray 

 mud beds indurated by calcite which are mostly 3 to 6 inches but 

 sometimes 3 to 4 feet thick, as in the bank of the Kayaderosseras 

 creek above Ballston Spa. These mud beds break conchoidal or 

 lumpy and are very fine grained. The shale is fissile and splintery 



1 N. Y. State Mus. Bui. 162, p. 22. 



