DEVONIAN AND CARBONIFEROUS IN NEW YORK 523 



made to trace these formations southward and westward into McKean and Warren 

 counties, Pennsylvania. 



Age of Rocks and Pkobi.kms involved 



The Paleozoic i-ocks exposed in the quadrangle extend from about the middle of 

 the Chemuno; up into the Carboniferous. They consequently include the Catskill 

 or its equivalent in the Upper Devonian and the boundary or transition between 

 the Devonian and the Carboniferous. To the eastward in both New York and 

 Pennsylvania the distribution of the Chemung, the Catskill, aud the Carboniferous 

 rocks and their relationship to each other have received much study. To the 

 southward in Pennsylvania the Carboniferous rocks have been studied and the 

 Lower Carboniferous traced northward toward this region. To the west in Ohio 

 the Carboniferous and Waverly have been studied and traced eastward for some 

 distance into northwestern Pennsylvania. The Olean-Salamanca region, however, 

 has been an unknown meeting ground into which, when attempts were made to 

 trace beds that were distinct to the east, the south, or the west, the tracings be- 

 came indistinct and the correlations uncertain. 



Topography 



Topographically the region is a maturely dissected one. The hills rise with 

 steep slopes to an elevation of 500 to 1,000 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, so that exposures are concealed and the work 

 of the geologist is made difficult and slow. 



Structure 



The dominant structure is that of flat-lying beds dipping gently a little west of 

 south at about 30 feet per mile. Here and there the dip is locally increased or 

 decreased, and in the Glean and eastern Salamanca area, just south of the Alle- 

 ghany river, it is for a short distance reversed. Some minor folding occurs in the 

 Olean conglomerate on the ridge between Flatiron rock and Knapps creek. This 

 folding is entirely taken up in the 1,800 feet of shales that intervene_between the 

 Olean conglomerate and the Bradford oil sand, which is penetrated 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. 



Formations 

 chemung shales and 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 up- 

 ward some 700 to 750 feet. Of these the very lowest beds consist of 30 or 40 feet 

 of fine olive green, argillaceous shales seen best exposed near Cuba. 



Immediately above these shales there is a sandstone 10 to 15 feet thick, most 

 prominently exposed in and north of Cuba in a number of quarry openings. It is 

 a medium to coarse grained, somewhat arkosic sandstone, usually of a light cream 



