MAUCH CHUNK OF LESLEY ; UMBRAL OF ROGERS 45 



place. The discussion of this matter, however, must be deferred until 

 the Mauch Chunk has been described. 



The Mauch Chunk of Lesley; Umbral of Rogers 

 distribution and characteristics of the rocks 



Range of the Mauch Chunk. — The Mauch Chunk embraces the rocks 

 from the top of the Logan to the base of the Potts ville. 



The anthracite strip. — Within the anthracite strip this series consists 

 almost wholl}^ of sandstones and red shale, with here and there thin cal- 

 careous beds which become more conspicuous toward the south. It is pre- 

 served around the anthracite fields of Pennsylvania, around the Broad 

 Top bituminous area, in a petty area eastward within Fulton county, and 

 at the northern end of the Mount Savage synclinal, which extends south- 

 ward into Maryland and the Virginias, where the exposure becomes 

 much more important. As the strike sweeps round toward the west in the 

 anthracite fields, the southern field is the nearest to the old shoreline. 



Mr Winslow's section near Mauch Chunk, at the easterly end of the 

 southern field, shows a thickness of 2,168 feet, the upper 1,662 feet being 

 red shale and sandstone, the lower portion almost wholly shale;* but 

 at a little way farther north he finds 3,342 feetf almost wholly of red 

 shale. I. C. White measured nearly 2,000 feet in the Catawissa valley, 

 but in the southwest portion of the northern field near Shickshinny the 

 thickness has diminished to only 1,200 feet. Eight miles farther eastward 

 he found only 425 feet, the uppermost 100 being greenish sandstone, the 

 rest red and green sandy shale. Thence northward in this basin the 

 red shales disappear atid the mass grows thinner, so that at Scranton 

 the thickness is but 75 feet.l Clearly in this region the Mauch Chunk 

 did not extend into New York. H. D. Rogers, in summing up the char- 

 acter of the Umbral as it is shown around the anthracite fields, says that 

 the more argillaceous portions of the red shale frequently contain some 

 calcareous matter, bands of such matter being found occasionally in the 

 upper portion, but becoming more numerous in the middle and lower 

 portions. This calcareous matter is not in beds, but in nodules scat- 

 tered through the shale. Twelve such beds were observed near Tamaqua, 

 in the southern field, one of them 6 and another 3 feet thick, in which 

 the nodules are very abundant. This description refers especially to the 

 southern and middle fields. In the northern field the calcareous matter 



*J. p. Lesley: A summary description of tlie geology of Pennsylvania (final report), 1895, p. 

 1815. 

 t Final report, p. 1635. 

 X I. C. White : Geology of the Susquehanna region (G 7), 1883, pp. 44-46. 



