1 6 NEW YORK STATE MUSEUM 



are very pronounced. They can not be said to characterize the 

 Cobleskill dolomite since they occur, though not so abundantly, in 

 the other dolomites, particularly in the Fiddler's Green limestone. 

 The stylolite markings are described by Vanuxem in his report in 

 1840; he calls them Epsomites and says they are due to the crystal- 

 lization of epsom salts or magnesium sulphate in the limestone 

 muds.' Several other explanations have been offered to account 

 for these peculiar markings but none of them are altogether 

 satisfactory. 2 



The best exposures of the Cobleskill dolomite and Bertie water- 

 lime on the Syracuse quadrangle are at the Miller and Heard gyp- 

 sum quarries a mile south of Lyndon and a half mile north of White 

 lake; and in the ravine south of Chrysler's station on the Auburn 

 suburban line. Other good exposures of the same rocks are on the 

 hill above Manlius Center, on the electric line north of Jamesville, 

 and at several localities near the western margin of the map. 



- At Cobleskill, the type locality for this limestone, it is about 6 feel 

 thick, the same as at Syracuse. It thins out to some extent in On- 

 tario county to the west and then increases in thickness to 14 feet 

 in Erie county, where it is known as the " bullhead " or " pumpkin " 

 limestone. In the older reports it is the " Coralline limestone "of 

 Hall, with which it was correlated by Hartnagel in 1902. Previous 

 to that time it was considered part of the Manlius limestone in the 

 Syracuse area. 



RONDOUT WATERLIME 



The upper portion of the dolomite beds has been correlated by 

 Hartnagel with the Rondout waterlimes. In this locality it com- 

 prises a greater thickness than the Bertie and Cobleskill beds com- 

 bined. By greater lithologic changes it indicates a greater change 

 in geographic conditions than do the others. So far as this area is 

 concerned, it marks a long, fluctuating, transitional stage from the 

 gray argillaceous dolomites of the underlying groups to the more 

 compact, less magnesian, blue limestones of the overlying Manlius 

 formation. 



The Rondout of this region consists of gray dolomites inter- 

 stratified with shaly layers grading, in places, into argillaceous shales. 

 The upper part of the bed contains many finely straticulate layers 

 with narrow bands of more calcareous limestone. Some of the 

 layers near the base are richly impregnated with celestite crystals, 



*Nat. Hist. N. Y„ Geol. Surv. Third District, 1842. 

 2 Am. Jour. Sci., 4:142, 1897. 



m 



