42 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



glomerate. The character and thickness of the formation show com- 

 paratively little variation throughout, though the field extends west- 

 wardly almost as far as the northern prong of the southern, from which 

 it is separated by not more than fifteen miles. The most notable feature 

 is the great decrease in thickness of the lower or less coarse division. 



Eastern Middle field. — The western half of this field overlaps the western 

 Middle as far as the eastern portion of the Mahanoy basins, while the 

 eastern half extends a little way beyond the eastern point of the South- 

 ern. The nearest approach to the western field is in the Silver Creek 

 basins, where one is barely 2 miles from the Mahanoy. 



The Pottsville is but 300 to 400 feet thick in the Silver Creek basins — 

 a rapid decrease from the 830 feet in the eastern Mahanoy basin, only 

 2 or 3 miles away at the south. In the Beaver Meadow basins, north 

 from the last, the mass is a conglomerate, almost 300 feet, interrupted 

 only by a thin coal bed and a bed of black shale. In the Green Moun- 

 tain basin, west from the last, the thickness is the same, but the bottom 

 100 feet is less coarse. The Hazleton basins, north from Beaver meadow, 

 show 290 to 300 feet of Pottsville ; Black creek and Big Black Creek 

 basins show coarse sandstones and conglomerates, about 200 feet at the 

 west, but increasing eastward to about 290 feet. Still farther north, in 

 the Woodville-Cross Creek basins, one finds at the eastern end 260 feet, 

 mostly conglomerate ; near Drifton, borings show much variation — 

 200 to 260 feet — in some cases practically conglomerate throughout; in 

 others, some shales and sandstones. Farther west, in the Little Black 

 Creek basins, the thickness is not far from 240 feet, and the rock is 

 mostly conglomerate, while northward, in the Upper Lehigh and Pond 

 Creek basins, the thickness becomes 180 and then 165 feet — sandstone 

 above and conglomerate below. Evidently the whole of the lower 

 division and not a little of the upper division have disappeared. 



Northern field. — The western division of this field is about 12 miles 

 north from the nearest point in the eastern Middle and about 32 miles 

 from the southern border of the Southern field. 



According to Mr Smith, the Pottsville is 60 feet thick at the western 

 extremity of the field, but increases eastwardly until it becomes 250 feet 

 near Nanticoke. The rock is very coarse, the pebbles ordinarily as large 

 as a hickory nut, but in many localities as large as a hen's egg. Farther 

 eastward, near Wilkesbarre, the thickness is not far from 200 feet, Mr 

 Winslow's section, in Solomon's gap, showing 220 feet of conglomerate 

 broken only by 14 feet of sandstone and 3 feet of shale. In the Pittston 

 region the thickness is from 163 to 235 feet, while in the Scranton region 

 it varies from 250 feet on the southerly side of the field to 230 at Scranton 

 and about 200 on the northwesterly side. Thus far the rocks have been 



