234 GLACIAL FORMATIONS OF EKIE AND OHIO BASINS. 



As shown in Chapter III, it probably constituted the main western tributary 

 of the old Upper Allegheny. For a few miles west of the Allegheny there is 

 an open valley with low terraces of Wisconsin gravel standing only a few feet 

 above Brokenstraw Creek. On its borders there are rock shelves carrying 

 patches of gravel connected with the old drift, such as appear along the Alle- 

 gheny. The uplands north of Brokenstraw Creek, and also uplands farther 

 east along the north side of the Allegheny, are covered with a thin but nearly 

 continuous sheet of very stony drift, including a liberal supply of small 

 bowlders. These deposits have been noted at altitudes 600 feet or more above 

 the valleys, or fully 1,800 feet above tide. South of Brokenstraw Valley, 

 from its mouth up to G-arland, there seems to be very little upland drift, and 

 it is possible that a small unglaciated tract appears between this valley and 

 the Allegheny. 



From Garland southwestward to Titusville there is a lowland known as 

 Grand Valley, which is filled deeply with drift. It is not certain that it 

 was drained by a single stream. On the whole it seems more probable, as 

 noted in Chapter III, that the northeastern end discharged eastward to the old 

 Upper Allegheny, and the southwestern end westward, past Titusville, to the 

 old Miiddy Creek. The old divide may be buried to a depth of 200 feet. 

 At Newton, which stands near the present divide in this lowland, a well 

 penetrated 2<S3 feet of gravelly drift and entered rock at about 1,125 feet 

 above tide, which is slightly above the level of the rock floor of the 

 ' Allegheny a few miles to the east. At Grand Valley station a well reached 

 rock at 204 feet, the altitude of the rock floor there being about 1,140 feet 

 above tide. A well 1 mile southwest of Grand Valley penetrated 220 feet of 

 drift, reaching rock at a level scarcely more than 1,100 feet above tide. 

 About 3 miles east of Titusville drift deposits are heavy on the south border 

 of this valley. One well on ground about 350 feet higher than Titusville, 

 or 1,550 feet above tide, reached a depth of 235 feet without entering rock. 

 The lowland in that vicinity was so nearly filled with drift that the present 

 drainage line. Pine Creek, departs from the old line and cuts across the 

 face of the old north bluff. 



On the south side of Grand Valley drift deposits are heavy along tlie 

 line of old valleys to their heads, but seem to be light on the intervening 

 uplands. The wells in these valleys often pass through 100 feet or more 

 of drift within a mile north of their heads, at altitudes of 1,600 to 1,700 feet 



