THE ANTHRACITE STRIP 41 



sandstones and shales.* Within the main body of the field, eastward 

 from the place of division, the Pottsville retains the same general fea- 

 tures to a little beyond Tremont. The thickness here on the southerly 

 side of the field is from 1,100 to 1,200 feet, but on the north side the 

 cross section indicates perhaps 200 feet additional. Near Pottsville the 

 thickness in Sharp mountain is given as 1,200 to 1,350 feet, near Tama- 

 qua as 850 to 1,130 feet, while in the Panther Creek district at the east- 

 ern end the variations are extreme. The difference in measurement re- 

 ported by the several observers is due in great part to disagreement 

 respecting the plane of division between Mauch Chunk and Pottsville. 

 Some incline to take the highest red bed as marking the top of the Low r er 

 Carboniferous, while others carry Pottsville to the plane at which coarse, 

 more or less conglomerate beds first appear. The latter seems to be the 

 better plane as marking the beginning of land elevation at the east. The 

 division into coarse Upper and less coarse Lower Pottsville continues 

 throughout, but there is much more conglomerate at the east and the 

 shales of the west are replaced there by sandstone. 



Mr David White states that the pebbles in the lower part of the Potts- 

 ville within this field are rounded imperfectly, subangular fragments 

 being not rare in the lower third. Quartz pebbles predominate, but those 

 of sandstone and shale are not infrequent. The coarseness increases to- 

 ward the east, pebbles at the west rarely being larger than a goose's egg, 

 whereas at Hacklebarney tunnel the diameter is sometimes 5 or 6 inches. 

 Higher up in the section the pebbles are better rounded and polished, 

 the rocks become more arenaceous, the shales disappear, so that in the 

 upper 200 to 300 feet the conglomerate is massive, white, persistent, and 

 lithologically comparable to the Homewood of western Pennsylvania/)" 



Western Middle field. — The Mahanoy basins form the southern strip of 

 this field, and extend eastwardly beyond the Shamokin or northerly 

 basins, which in their turn have a greater extension toward the west. 

 The Mahanoy near its eastern extremity is practically in contact with 

 the Broad Mountain district of the southern field. 



Within the Mahanoy basins the Pottsville is from 830 to 850 feet 

 thick, very coarse in the upper 600 feet, while the lower portion is only 

 moderately coarse, containing some sandstone and shale, though in the 

 western portion conglomerates are found throughout the section. The 

 thickness in the Shamokin basins is from 800 to 600 feet. At the west- 

 ern end it is about 750 feet and the' rocks are almost wholly coarse con- 



* H. D. Rogers : Geology of Pennsylvania, vol. ii, 1858, pp. 191-193. The chief study of the anthra- 

 cite region, as given in Rogers's report, was by James D. Whelpley and Peter W. Sheafer, but no 

 reference is made to them in the body of the report. 



t David White : Op. cit.. pp. 764, 765. 



