970 NEW YORK STATE MUSEUM 



Above the Cuba sandstone lentil the Chemung is composed 

 of green and brownish argillaceous and sandy shales, inter- 

 bedded here and there with thin shaly sandstones. With the 

 probable exception of certain dark purplish shales to be 

 described presently, the individual beds of neither the shales 

 nor the shaly sandstones usually retain their thickness or 

 individuality or possess any lithologic character that would 

 enable any one of them to be traced and identified for any dis- 

 tance. The nearest approach to persistency in these variable 

 beds is found in a sandy zone about 200 feet above the Cuba 

 sandstone. A number of quarries have been opened in the 

 past on some argillaceous samdstones at this horizon. The 

 stone is fine grained and soft and is more accurately described 

 perhaps, as a shaly sandstone that varies into an indurated 

 mudstone. When exposed to the weather the outside scales 

 off or cracks and seams develop, so that in each quarry 

 opened it was soon found to lack durability. All these quarries 

 are abandoned today but at intervals along either valley wall 

 of Oil and Olean creeks from one a few miles above Hinsdale 

 that furnished material for locks for the old state canal to 

 ones to the west and to the south of Olean may be ]seen the 

 old openings. But even this sandy zone, persistent as it is 

 as a whole, well illustrates the variability in detail of these 

 Chemung strata for often in one quarry face there is visible 

 a complete change along the bedding plane from one lithologic 

 phase to another, so that as a whole these Chemung shales and 

 argillaceous sandstones are only regular in their irregularity 

 and intergradation. 



The one exception as regards the rapid variability of these 

 shales is found in certain dark purple or chocolate colored 

 shales about 325 to 350 feet below the top of the Chemung. 

 These are largely sandy and interbedded with thin plates of 

 very shaly sandstone often of about the same color. They 

 sometimes have a reddish cast but it is always a very dark 

 brick red never a bright red. They seem to be widely persistent 

 and are found in many well borings to the south. Their top 

 Occurs in the Dennis well at Bradford Pa. at a depth of 712 feet 



In a few places south of Cuba some faint traces of oolitic 

 iron ore are found in the shales a hundred feet or more above 



