64 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



chiefly by sandy shales.* Comparison with the section at Westernport, 

 in Maryland, shows that the Sharon is less important there. 



WESTERN COUNTIES OF PENNSYLVANIA 



Returning now to the northern line, Warren county is west from Mc- 

 Kean, along the New York border. Only isolated patches of the Potts- 

 ville remain north and west from the Allegheny river, but some extensive 

 areas are found in the southeastern part of the county. Mr Carll has 

 shown that the lower member of the Pottsville, the Sharon-Olean con- 

 glomerate, disappears abruptly in the northeast corner of the county. 

 At the u Pass," about 8 miles west from the McKean line and 7 miles 

 south from the New York line, the section is 



Feet 



Sandstone 60 



Conglomerate 25 



Shenango shales 30 



Logan (Shenango) sandstone 



whereas at barely one mile northward the conglomerate has disap- 

 peared, and the sandstone rests directly on the Shenango shale. East- 

 ward from the Pass the conglomerate is soon lost, and it is absent for 

 about 2 miles, reappearing at the Quaker Hill mines, where it is very 

 thin. It increases toward the south of east, becoming 8 feet within a 

 mile, where it is but 5 feet above the Logan, and reaching 20 feet at a 

 mile farther east. The overlying sandstone is regarded by Mr Carll as 

 equivalent to the Kinzua (Connoquenessing) sandstone of McKean. 

 The Sharon is persistent westwardly, for it is present in an outlier within 

 Sugar Grove township, 16 miles west from the Pass and about 5 miles 

 south from the New York boundary. 



At the Pass the Connoquenessing and Sharon are in contact, but at 

 the Quaker Hill mines, about 2 miles east, they are separated by 



Feet. Inches 



Shales 40 



Coal 3 



Shale 4 9 



Coal 1 6 to 2 feet. 



Shale 10 



in all, about 47 feet. The shale between the coal layers is often replaced 

 in part by conglomerate, in which the pebbles, like those of the Sharon 

 conglomerate below, are coated with carbonaceous matter. This curious 

 little basin, containing not more than 50 acres, shows a dip from all 



* George C Martin : Maryland Geological Survey. The Geology of Garrett County, 1902, p. 103. 



