078 NEW rC UK STATE MUSEUM 



Salamanca conglomerate lentil. A comparison of these figures 

 shows that this thickness frequently varies irregularly and 

 very materially within short distances. The interval from the 

 top of the Salamanca to the top of the Cattaraugus near Flat- 

 iron is 65 feet, southwest of Knapp's creek it is about 145 feet. 

 In the Dennis well at Bradford Pa. it is 84 feet. At the head 

 of Chipmunk creek it is about 90 feet. East of Chipmunk it 

 is 110 feet in one place and in another near by more than 145 

 feet. At the head of Leonard brook it is 180 feet, northward 

 at the head of Baillett brook it is 220 feet, while still north 

 beyond the Allegheny it is only 100 feet on the knob east of 

 Carrollton. In several places in the Limestone-Irish brook 

 region it is 100 feet or less while just north of Rice brook it 

 is at least 230 feet. On the southeast side of upper Bed House 

 brook it is 110 feet while on the northwest side it is over 210 

 feet. At the triangulation station southeast of Salamanca it is 

 215 feet or less, a mile and a half north it is 240 feet or more. 

 It is not thought probable that mere local variations in the 

 thickness of the strata of the Cattaraugus could be rapid 

 enough and great enough to account for the irregular varia- 

 tions that have just been mentioned in the thickness of that 

 part of this formation which lies above the Salamanca con- 

 glomerate lentil. It seems more probable that the upper 

 surface of the Cattaraugus is irregular because of erosion and 

 that there is consequently an unconformity at this point repre- 

 senting an erosion interval between the Cattaraugus and the 

 succeeding Oswayo. 



CARBONIC FORMATIONS 



Oswayo beds 

 Composition. The close of the Cattaraugus stage was marked 

 by the cessation of the deposition of red shales in this region. 

 After what is believed to have been an erosion interval it was 

 followed by the deposition of olive-green to rusty colored 

 sandy shales, with here and there thin sandstone layers with 

 limonitic seams or incrustations. These greenish, limonitic 

 shales constitute the Oswayo formation. Its thickness varies 

 from 1G0 to 250 feet, the average being near the latter number. 

 Conditions now became more favorable to the existence of 

 life and, in contrast to the usual barrenness of the red shales 



