. Bulletin of the Geological Society of America. Geology. m A. W. G&ABAU TYPES OF SEDIMENTARY OVERLAP the eastern outcrops in Pennsylvania has been accepted as the equivalent of that in the western counties, as though the westward decrease were due merely to lessened thickness in each of the subdivisions. It must be clear, however, . . that the loss in thickness is due very largely to disappearance of the lower members of the section, as is the case also southward from central Kentucky and southern Virginia, so that in Alabama and much of Tennessee only the uppermost beds remain. A new cor
. Bulletin of the Geological Society of America. Geology. m A. W. G&ABAU TYPES OF SEDIMENTARY OVERLAP the eastern outcrops in Pennsylvania has been accepted as the equivalent of that in the western counties, as though the westward decrease were due merely to lessened thickness in each of the subdivisions. It must be clear, however, . . that the loss in thickness is due very largely to disappearance of the lower members of the section, as is the case also southward from central Kentucky and southern Virginia, so that in Alabama and much of Tennessee only the uppermost beds remain. A new correlation appears to be ;* The general change in the character of the sediments from conglom- erates and coarse sandstones in the east to shales in the west is also emphasized by Stevenson. The relationships of these deposits may be expressed in the following diagram: ^rsn. Figure 14.—Relation of Waverley and Chemung Formations to the Pocono and Catskill. The Mauch Chunk.—The Mauch Chunk period of Appalachian history seems to have been a period of more stationary conditions, accompanied by some subsidence, as shown by the fact that fine sediments characterize the formation throughout, and also by the presence of extensive marine limestones. In the northern Appalachians heavy non-marine sediments still Thus in the type region 2,168 feet of red shales, with some sandstones in the upper part, constitute this formation. A little north of Mauch Chunk, Pennsylvania, the formation of this name has a thickness of 3,342 feet and consists almost wholly of red shales. In the Broad Top region of Huntingdon county, Pennsylvania, the basal part of the Mauch Chunk consists of 141 feet of shales and sand- stones, followed by 49 feet of limestone (Greenbrier), and this by 910 feet of sandstones and shales. In northeastern Lycoming county, 30 miles from Mauch Chunk, the base of the formation consists of 120 feet of shales, followed by 75 feet of marine limestone a
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