968 NEW YORK STATE MUSEUM 



gions southward and westward in McKean and Warren counties 

 Pennsylvania. 



Topography. Topographically the region is a maturely dis- 

 sected one. The hills rise with steep slopes to an elevation of 

 500 to 1000 feet above the main stream levels. The northern 

 portion of the two quadrangles is glaciated and exposures of 

 rock in place are infrequent. Much of the southern portion 

 and of the reconnaissance area in Pennsylvania is wild and 

 wooded, and overgrown in many places with a dense tangle of 

 bushes, briers and vines that both conceals exposures and ren- 

 ders the work of the geologist difficult and slow. 



Structure. The dominant structure is that of flat lying beds 

 dipping gently a little west of south at an average rate of 

 about 30 feet a mile. Here and there the dip is locally increased 

 or decreased and in the Olean and eastern Salamanca area just 

 south of the Allegheny river it is for a short distance reversed. 

 Some sharp minor folding occurs in the Olean conglomerate 

 south of Olean along the high ridge extending from Flatiron 

 rock to Knapp's creek and beyond. This folding is entirely 

 taken up in the 1800 feet of shales that intervene between the 

 Olean conglomerate and the Bradford oil sand which is pene- 

 trated by many wells at this depth and shows no sign of folding. 

 In the Salamanca region some low rolls or folds with northeast- 

 southwest axes were noted by Mr Fuller. 



STRATIGRAPHY 

 DEVONIC FORMATIONS 



Chemung beds 



Description of Chemung shales and of Cuba sandstone lentil. The 

 oldest rocks in the region are those near stream level in the 

 northeastern part of the Olean quadrangle. They are typical 

 Chemung shales and extend upward some 700 to 750 feet. Of 

 these the very lowest beds consist of 30 or 40 feet of fine olive- 

 green, argillaceous shale, seen best exposed in railway and other 

 cuttings near Cuba. An excellent exposure may be seen a few 

 yards east of the Erie depot at Cuba. In the railway cut 20 feet 

 of it are exposed and nearly 20 feet more may be seen in the 

 gutter by the side of the street leading down into the town. It 

 is here fine grained and weathers into very small fragments. 



