Evidence of a glacial dam in the Allegheny River between Warren, Pennsylvania, and Tionesta
The observable Field Data as to upper Drainage The portion of the Allegheny River Valley between Warren, Pennsylvania, 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 opening 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. Beneath this there are 100 feet of . . .