BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 25, pp. 215-218, PL. 9 JUNE 18, 1914 



EVIDENCE OF A GLACIAL DAM IN THE ALLEGHENY EIVER 

 BETWEEN WARREN, PENNSYLVANIA, AND TIONESTA ^ 



BY G. FKEDERICK WRIGHT 



{Presented hy title before the Society January 1, 191Jf) 



CONTENTS 



Page 



The observable field data as to upper drainage 215 



The southern drainage 216 



Conclusions 218 



The observable Field Data as to upper Drainage 



The portion of the Allegheny River Valley between Warren, Pennsyl- 

 vania, and Tionesta presents some of the most puzzling and important 

 glacial phenomena bearing on the interval of time separating the earliest 

 from the latest advances of glacial ice. The moraine traced by Lewis and 

 Wright here falls several miles short of reaching the Allegheny River at 

 Warren. But older glacial deposits are found several miles south of the 

 Allegheny about the headwaters of Tionesta Creek, at Stoneham and 

 Clarendon. These are evidently waterlaid, and fill a broad valley open- 

 ing north into the Allegheny about two miles above Warren. The glacial 

 deposits at Clarendon are 308 feet thick. The upper 60 feet consist of 

 gravel containing a noticeable amount of granitic material. This is 

 underlain by 148 feet of sand containing a small amount of gravel. Be- 

 neath this there are 100 feet of clay, in which there is an occasional 

 stratum of logs. The rock-bottom at Clarendon is 160 feet below the 

 present level of the Allegheny at Warren. The descent of the rock-floor 

 in this valley is 125 feet in the 12 miles from Sheffield to Warren, while 

 the descent of the rock-floor in the Conewango Valley is 130 feet from 

 Warren to the State line. This would demonstrate that the preglacial 

 drainage was through the Conewango, were it not that at places the rock- 

 bottom of the Allegheny below Warren toward the mouth of Brokenstraw 

 Creek at Irvine is a few feet lower than it is at Warren, and the depth 



1 Manuscript received by the Secretary of the Society February 17, 1914. 



(215) 



