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NEW YORK STATE MUSEUM 



stratigraphic unit, has led him to substitute for these unsatis- 

 factory designations the name Cobleskill, 1 as it is along this creek 

 near Howes Cave that the outcrops of this limestone are most 

 typical. 



Section at Howes Cave 



The accompanying section will serve to indicate the strati- 

 graphic relations of the Cobleskill at Howes Cave. Directly 

 beneath the Cobleskill the Salina shales are exposed with a thick- 

 ness of 34 feet. The contact with the Lorraine beds can not be 

 observed at this place, but in the bed of a small stream 1 mile 

 farther north the contact is seen to be deceptively conformable. 

 From observations made at this place, the thickness of the Salina 

 at Howes Cave can not be far from 40 feet. The characters of 

 these shales are quite uniform. In color they vary from a light 

 gray to green. They break readily and soon crumple. The most 

 conspicuous feature is the presence of nodular iron pyrites in 

 such quantities that at Schoharie they were once mined. These 

 shales have been quarried and sold for plaster, but, unlike beds 

 of the Salina of western New York, they contain only traces 

 of gypsum. Their value as a plaster seems to be due to the oxida- 

 tion and decomposition of the iron pyrites, the sulfur of the 

 pyrites combining with oxygen and water, forming sulfuric acid. 

 The acid attacks the carbonate of lime present, forming lime 

 sulfate, which, with the addition of two parts of water, gives 

 gypsum. 



Folding and slight displacements of these shales are often seen, 

 specially near their lower portion. These, however, appear to be 

 only local developments. There is no transition into the Cobles- 

 kill. The line of demarcation is very strongly defined. The soft 

 shales, weathering away beneath, sometimes leave the Cobles- 

 kill as a projecting ledge. These same features are observed 

 farther east at Schoharie, where the formation has a thickness 

 of 27 feet, having thinned 13 feet in a distance of 5 miles. The 

 most easterly extension of these shales that has been observed is 

 near Gallupville, 5 miles east of Schoharie, showing that the 

 extreme eastern extension of the great Salina beds of New York 



1 U. S. N. Y. Sec. Rep't. Regents Bui. 59. 1902. p. r42. 



