EASTERN COUNTIES OF ALLEGHENY PLATEAU 57 



The Johnson Run sandstone is massive and finegrained; it is the 

 Homewood sandstone of Doctor White's type section. The Kinzua is 

 less massive, but more or less pebbly. It is the representative of White's 

 Connoquenessing sandstones and occasionally shows a trace of the 

 Quakertown coal and shale. The Olean is the Sharon sandstone; it is 

 often very coarsely conglomerate, but the coarser portions are lenticular. 

 This is the rock forming the rock city at Olean, in Cattaraugus county 

 of New York. The Alton group is the Mercer group of White, and the 

 Alton coals are strictly equivalent to his Mercer and Tionesta coal beds, 

 They are often three in number within McKean county, at times of 

 workable thickness, but usually of little value, as much because of im- 

 purities as of abrupt variations in thickness.* 



The dearth of information respecting Clearfield county, south from 

 Cameron and Elk, is remarkable. The formation is above the streams 

 at many localities, but apparently exposures admitting of measurement 

 are exceedingly rare. Mr Franklin Piatt estimates the thickness of Potts- 

 ville at not less than 200 feet in Boggs township of Clearfield, where the 

 rock is a white quartzose sandstone with much massive fine conglom- 

 erate. Doctor Chance states that in Bell township of the same county 

 the pebbles are at times large as a hen's egg. Coal is reported at several 

 localities as occurring in the upper third, evidently some member of the 

 Mercer group.f 



In Jefferson county Mr Piatt J was able to recognize the Homewood 

 sandstone, the Mercer shales, and the Upper Connoquenessing sandstone. 

 The Homewood is usually coarse and massive with, in many places, 

 white quartz pebbles varying in size from pea to hen's egg. It makes 

 " rock cities " and has an extreme thickness of 60 feet. The Mercer 

 shales are 30 to 80 feet thick, with one to three coal beds, the upper 

 never more than 8 feet below the Homewood. No limestones are here. 

 The Connoquenessing sandstone is 125 feet thick at one locality ; but 

 evidently Mr Piatt entertained some doubt respecting the exact relations 

 of this great sandstone, as he discovered at one locality a red shale at 

 about 100 feet below the top of the Homewood which bears much resem- 

 blance to Shenango. 



Doctor White § gives the record of a boring at Brookville which goes 

 far to strengthen Mr Piatt's evident doubt, for the thickness assigned to 



*C A. Ashburner: Geology of McKean County (R), 1880, pp. 49-59; Geology of Elk County 

 (RR), 1885, pp. 69, 127. 

 A. W. Sheafer : Geology of Cameron County (RR), p. 48. 



|H. M. Chance : Rev. of Bit. Coal Measures of Clearfield County (H 7), 1884, pp. 109, 115. 

 t W. G. Piatt : Jefferson County (H 7), 1881, pp. xxxiii, 84, 90, 125, 158, 165, 173-174, 186, 194-195, 196. 

 § I, C. White : U. S. Geological Survey Bulletin 65, p. 183. 



