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CHARLES BUTTS 



as mentioned above, and these occur in a cut about ij miles south- 

 west of Duncansville where the recently constructed branch of the 

 Pennsylvania Railroad diverges from the course of the old Portage 

 Road. (See Fig. 3.) East of this point also are almost continuous 

 exposures of the underlying rock for a thickness of many hundred 

 feet, but no Chemung fossils could be found. No effort was made 

 to trace this boundary farther to the southwest. 



Chemung formation. — The Chemung formation follows conform- 



FiG. 8 



ably upon the Nunda to which it is, in its lower part, very similar 

 in lithologic character, but from which it is sharply distinguished 

 througliout by paleontologic characteristics. As stated in the descrip- 

 tion of the railroad section above, the lower limit of this formation 

 is placed at the lowest horizon at which Chemung fossils are found. 

 Its upper limit is the bottom of the distinctly differentiated rocks of 

 the Catskill formation. As shown on the profile section, the forma- 

 tion outcrops for i mile along the Pennsylyania Railroad, its bottom 

 being about 2^ miles and its top 3^ miles west of Altoona. Fig. 8 



