VARIATION AND EQUIVALENCE OF SANDSTONE 467 



the great northward bend of the river carries the coal high in 

 the hill slopes at Queen Shoal and then allows it to descend to 

 near water level at the mouth of Little Sycamore Creek. The 

 writer is very willing to testify to the general accuracy of Dr. 

 White's work, but he is not willing to have the evidence of fossil 

 plants impeached in the eyes of the public by stratigraphic evi- 

 dence of this character. 



According to fossil plants the Clendenin coal probably 

 belongs to the Kittanning group and the plants collected near 

 Clay ^ from a horizon about 300 feet above the flint are related 

 to the Freeport flora. Although Dr. White calls these two beds 

 the same, a glance at the accompanying sectio'ns shows that the 

 stratigraphic evidence is against such a correlation, and that the 

 plant-bearing bed of Clay is distinctly above the Clendenin coal ; 

 therefore the latter may be the representative of the Freeport 

 group, if the Clendenin coal belongs to the Kittanning horizon. 



A comparison of the sections given in Fig. 2 shows clearly 

 that the observed increase in thickness of the sandy series in 

 •the direction of Clay is not due to the great expansion of the 

 formation, but to the addition of coarse conglomeratic members 

 to the top of the original section. These extra members appear 

 first as thin beds of conglomerate in shaly material above the 

 Charleston sandstone proper ; they thicken gradually to the east, 

 and finally merge not only with each other, but also with the 

 underlying sandstone formation. 



This gives a distinctly sandy series at Clay, which can be 

 traced continuously in outcrop to Charleston, but which mani- 

 festly does not represent the same time interval as the Charles- 

 ton sandstone at the type locality. The uppermost bed at Clay 

 is very much younger than the uppermost bed at Charleston, 

 • and if similar changes occur north of Clay, it is possible for 

 the sandstone to be as young as Mahoning on the Pennsylvania 

 line. 



The variation in the sandstone between Charleston and Clay 

 appear to be limited to its upper part, but beyond the latter 

 place the writer feels assured that a similar change occurs at 



'David White, op. cit., pp. 170-73. 



