4(>-J 



Report of the State Gteologist. 



Small patches occur west of Stone Bridge, northeast of Bellvale, northwest <»f 

 Monroe and northeast of Highland Mills. The two important areas are the 

 one west of Cornwall station, and the belt along the western side of Shaw an- 

 gunk mountain. In the latter belt are recognized the Tentaculite, Lower 

 Pentamerus, Shaly and Upper Pentamerus members. In the Cornwall area, 

 the Shaly, Pentamerus and Tentaculite are met with. The Scutella limestone 

 is not found in the county. As the characters of these beds are so 

 different at the various localities, they are best described in the paragraphs 

 treating of these regions. 



Oriskany Sandstone. The two belts of Oriskany which occur within 

 the comity present widely different characters. The western belt forms the 

 western part of the llelderberg ridge, which extends up the Ne\ ersink valley 

 from Port Jervis. It consists of fine-grained shaly sandstones and impure 

 limestones, the latter often containing many fossils. The limestones weather 

 to a soft red rock, from which the fossils may often be dug with a knife. The 

 beds dip to the westward under the Esopus slates and Pleistocene deposits of 

 the Neversink valley, but the bedding is almost everywhere obscured, and 

 there is present a pronounced cleavage, which causes the rock to split into 

 verv thin layers. The cleavage generally dips steeply to the east. There are 

 also often present cherty bands containing fossils. The Oriskany forms 

 narrow ridges, and the thickness of the formation is about 125 feet. 



The second Oriskany area is along the western side of Bellvale and 

 Skunnemunk mountains, where it affords a fine-grained red or gray quartzite, 

 which changes locally to a conglomerate. It is underlaid by the Heidelberg 

 limestone in places, and in turn dips conformably under the Monroe shales. 

 About one hundred feet are exjwsed. The grey limestone is every where 

 traversed by innumerable cracks, which produce an extensive and character- 

 istic pile of debris around each outcrop. The red quartzite does not 

 contain these slit-like cavities, which are probably joint cracks. The 

 conglomerate appears in association with the gneiss knobs northwest of 

 Skunnemunk. 



Esopus Slate. This formation consists of black or bluish grey shaly 

 sandstones, grits and black slates. It occurs only in the eastern part of Deer 

 Park township, on the western side of the llelderberg ridge, where it rests 

 on the Oriskany sandstone. The formation gives rise to small narrow ridges, 

 which may possibly represent step-faults. The probable thickness is about 

 7<><> feet, if there are no faults as above mentioned. All the members have a 

 strong easterly dipping cleavage, which makes a sharp angle with the usually 



