LOWER SILURIC SHALES OF THE MOHAWK VALLEY 57 



arenaceous shale containing plenty of iron pyrite " is found between 

 the top of the Indian Ladder beds and the waterlime. This bed 

 corresponds in its lithic character and aspect, position and especially 

 also in the strong pyrite content so much to the Brayman shale, 

 that it is a fair inference to consider it as the last eastern trace of 

 the formation/ It is here as sharply separated from the overlying 

 waterlime (Rondout waterlime), as it is from the Cobleskill beds 

 at Schoharie and it is likewise sharply separated from the underlying 

 Indian Ladder beds. 



Extending so far east beyond the Cobleskill limestone, it is non- 

 contiguous with the latter and independent from it; but it is also 

 to be noted that the bed overlies both the Schenectady shale (at 

 Schoharie) and the Indian Ladder beds at the Indian Ladder, which 

 would seem to make it independent from the Schenectady shale. 



Westward from the typical outcrops of the Brayman shale in 

 the Helderberg recesses of the Schoharie creek and Cobleskill, we 

 are not aware of any other outcrops but that at Sharon Springs 

 exposing the contact of the " Frankfort " shale with the overlying 

 beds. At Sharon Springs, both Mr Hartnagel and the writer have 

 noted that the basal beds of the waterlime (corresponding to either 

 the Bertie waterlime or the Camillus) are largely composed of 

 greenish, olive and bluish clay shale resembling the Brayman shale, 

 but lacking the pyrites, and apparently passing by gradation into the 

 typical waterlime. The inference would be that in this locality, 

 which is 10 miles northeast of the Central Bridge outcrop, where 

 the Brayman shale is 27 feet thick, the Brayman shale is merged 

 into the lower Salina beds and this is probably the most potent argu- 

 ment that can be brought forward for a correlation of the Brayman 

 shale with the Salina beds, especially since the thickness of the water- 

 lime at Sharon Springs (about 30 feet) roughly corresponds to that 

 of the Brayman shale at Brayman and Central Bridge. 



But the absence of the pyrite in the basal waterlime at Sharon 

 Springs and the restriction of the bluish shales to the base would 

 suggest that we here have possibly reworked Brayman shales be- 

 fore us. 



Mr Hartnagel has observed that most formations overlying the 

 Frankfort shales are charged with the iron pyrite at their base, as 



1 Harris (Bull. Am. Pal. no. 19, p. 25) has indeed compared the hed 

 with the Brayman shale, while Grabau (title, p. 292) considers it as the 

 " basal clastic beds of the Rondout." 



