THE DEVONIAN SECTION NEAR ALTOONA, PA. 629 



shows the character of the Chemung rocks about 3 miles west of 

 Altoona, and also the fault mentioned on p 624. 



The total thickness of this formation in the section just described 

 is over 2,500 feet. In the lower 1,400 feet the rocks are gray or 

 green, sandy or clay shale, with a small proportion of gray sand- 

 stone, generally in thin layers in the shale, but occasionally in a 

 stratum 50 feet thick; in the. upper 1,000 feet the rocks are charac- 



FlG. 9 



terized by a large proportion of chocolate shale and by thin layers 

 of chocolate sandstone. 



Fossils occur in the topmost layers of the Chemung within a few 

 feet of the bright red shale and sandstone of the Catskill formation. 



Catskill formation. — This formation overhes the Chemung con- 

 formably. The top of the Catskill cannot be very definitely deter- 

 mined in the railroad section. The red shale shown in the profile 

 section about 1,400 feet east of Kittanning Point probably is not far 

 from the top, since it is apparently followed above by prevaihngly 

 gray shale and sandstone of the Pocono formation at the base of the 



