EASTERN COUNTIES OF ALLEGHENY PLATEAU 49 



but he places only the upper shales in the Mauch Chunk. The lime- 

 stone was not observed at any locality north or west from that locality ; 

 the shales grow thinner northward, so that in northwest Cameron, and 

 even at some localities within western Clinton, they appear to be absent. 

 Doctor Chance is inclined to doubt whether the shales ever reached the 

 western side of Elk county, west from Cameron. Shale is present in 

 Center county, south from Clinton, at Snowshoe, where it is at least 100 

 feet thick. "^ The condition in Potter county, north from Clinton, is not 

 sharply defined, and Ashburner was unwilling to draw the line between 

 Pocono and Mauch Chunk, giving for the whole interval of Mauch 

 Chunk and upper Pocono only 70 feet.f Franklin Piatt also hesitated 

 to mark any boundary and contented himself with the remark in many 

 places that the Mauch Chunk is very thin. Clearly the upper shale has 

 disappeared. 



Ashburner reports 40 to 50 feet of Mauch Chunk in Cameron county 

 and in the greater part of Elk, but at the western side of the latter 

 county the thickness is but 10 to 15 feel, with no red shale. In Forest 

 county, west from Elk, he finds some red shale in the 70 feet below the 

 Pottsville, but in McKean, north from Elk, he finds the Mauch Chunk 

 50 feet thick on the Cameron border and decreasing northward until it 

 becomes a dark, often coaly shale, varying from 5 to 10 feet.;!: 



Returning southwardly and entering Clearfield county from the south- 

 western side of Clinton, one finds few exposures. Doctor Chance in this 

 county and W. G. Piatt in the ad joininpj county of Jefferson were unable 

 to make any satisfactory measurements. Doctor Chance gives 125 feet 

 as probably the extreme thickness for Clearfield.§ The anticlines, 

 which rise so high farther south, are too gentle here to bring up much 

 of the Mississippian. 



Cambria lies south from Clearfield and west from Blair, extending 

 eastward to the crest of the Alleghenies. Mr Piatt observed the Mauch 

 Chunk beds on the Allegheny slope, but reached the bottom only where 

 the Conemaugh river cuts the Viaduct axis in the south central part of 

 the county, where he estimated the total thickness at 200 feet. A partial 

 section shows 1 1 



Feet 



Red and olive shales and sandstone 96 



Silicious limestone, exposed 10 



* H. M. Chance : Geology of Clinton county (G 4), 1880, pp. 94-96, 125. 

 tC. A. Ashburner: Geology of Potter county (G 3), 1880, p. 104. 

 tC. A. Ashburner : Geology of McKean county (R), 1880, pp. 63-64. 



gH. M. Chance: A revision of the bituminous Coal Measures of Clearfield county (H 7), 1884, 

 p. 14. 

 II W. G. Piatt : Report of progress in Cambria and Somerset district, part i (H 2), 1877, p. 46, 



