162 J. J. STEVENSON CAEBONIFEROUS OF APPALACHIAN BASIN 



this one finds local sandstones, but they are unimportant. In the south- 

 ern portion of the basin, on the contrary, the interval above the Wash- 

 ington coal bed is characterized by great sandstones, the Marietta of 

 Doctor White, which appear in their greatest development toward the 

 southwest outcrop, though they are prominent features across West Vir- 

 ginia, extending northward to midway in the state. 



The limestones of the Washington are quite as perplexing as those of 

 the Monongahela and they are confined to a smaller area. They attain 

 great thickness in central and southern Washington of Pennsylvania, 

 become comparatively insignificant southward in Greene county, and 

 practically disappear very soon in West Virginia. Limestone is most 

 abundant above the Washington coal bed, and in many places the mass is 

 largely calcareous shale. Few layers yield good lime, but the Upper 

 Washington limestone is ordinarily very good. Fossils of any sort are 

 very few, but occasionally one finds a great abundance of bivalve crusta- 

 ceans, usually thought to be of fresh-water types. Fish remains occur 

 plentifully in shales associated with some of the limestones, and they, 

 too, are probably fresh-water, as some of the genera are the same with 

 those found in the cannel of Linton, Ohio. Inroads of the sea are not 

 clearly shown. A shale containing some marine forms is reported from 

 one locality in West Virginia, but this is at the very bottom of the forma- 

 tion. One of the Washington limestones shows obscure markings like 

 fragments of brachiopods, but they are wholly indefinite and the evidence 

 seems to point to final exclusion of the sea from the contracting basin. 

 The limestones of the Washington bear much more resemblance to cal- 

 careous muds than do those of the Monongahela, but it is difficult to dis- 

 cover the source whence they were derived. 



During the Washington the crustal movements were sluggish within 

 the basin of deposition. Thin streaks of coal extend over great areas, 

 many of them showing complex structure; but toward the close the 

 movements became more pronoimced, and during the early portion of 

 the Greene the deep portion of the basin was confined to Greene county 

 of Pennsylvania and a narrow strip adjoining at the west in West Vir- 

 ginia. A comparison of sections shows that in southern Washington 

 county, following the Greene County line eastward, the interval from 

 the Upper Washington to the Nineveh limestone varies from 150 to 180 

 feet, each of these measurements being obtained twice, those of 180 

 being separated by one of 150, showing two shallow troughs cut by this 

 east-and-west line; but within half a dozen miles southwardly, in the 

 central part of Greene county, the interval increases, becoming 300 to 

 313 feet with a number of new limestones and coal beds. The chief 



