GEOLOGY AND PALEONTOLOGY OP THE SCHOHARIE VALLEY 103 



capiped by the Cobleskill limestone. Hartmagel holds that the 

 total thickness in this region is approximately 40 feet.^ 



One of the most accessible exposures of this formation is on the 

 left bank of the Schoharie, a short distance above the Fair street 

 l)ridge (Gebhard bridge) on the Gebhard farm. Here several 

 excavations have been made in search of ore, and the upper part 

 of the shales, together with the overlying Cobleskill, are well ex- 

 posed. This locality has long been known for the pyrite crystals 

 which can here be obtained, while the upper beds have yielded 

 arsenopyrite.^ 



Near Mix and O'Reilly's quarry northeast of Schoharie, Hart- 

 nagel's measurement showed 27 feet of these shales. This gives 

 a decrease of 13 feet in a distance of five miles. At this point, 

 near the crusher, the contact with the underlying sandstone is 

 well exposed, the two series of strata being absolutely conform- 

 able. The surface of the sandstone, exposed for several hundred 

 yards, appears to be a perfectly normal deposition surface, and no 

 trace of erosion, such as we might expect if there was an interval 

 covering Lower and Middle Siluric time, is visible. Moreover the 

 •sandstone is pyritiferous like the shale, and no fragments of the 

 lower rock are found in the Brayman shales. Neither does the 

 surface of the top sandstone layer show traces of weathering 

 before the deposition of the Brayman shales. 



It is inconceivable that the surface of this sandstone, even if worn 

 down to a uniform stratum, should be swept absolutely clean 

 before the shales were deposited-, so that no fragments of sand- 

 stone are found in the shale. It is clear that all the facts point 

 to the intimate relationship between the upper beds of sandstone 

 and the Brayman shales, making these sandstones of Upper 

 Siluric (Salina) age. The unconformable contact between these 

 sandstones and the Champlainic beds (Lorraine) must be looked 

 for some distance down in the sandstone series. 



The most easterly extension of the Brayman shales, so far as 

 has been observed, is according to Hartnagel ..." near 



^LoG. cit. p. 114, 



2 This information was furnished me by Prin. Solomon Sias of Schoharie. 



