THE SHExXANGO 95 



the last exposures ; but the landward advance was much more marked 

 at the south, where the thickness of the sandstones and shales is very 

 great, even where the Tuscumbia and Loioan have almost disappeared, 

 while in Alabama the advance was so great as to push the shore evi- 

 dently almost to the fall-line of the streams, for there the sands are 

 coarser and in such quantity as to be the characteristic feature from 

 central Alabama northward to within 50 miles of the Tennessee border 

 on the western side of the area; which leads to the supposition that 

 the land area southward and westward was much greater than has been 

 supposed. The outlet to the ocean may have been in Tennessee. 



The water area at the close of the Maxville extended farther south 

 and west than at any time after the middle of the Upper Silurian, for 

 the Maxville overlaps the whole Devonian and even the earlier mem- 

 bers ef the Mississippian. The greatest thickness is in the equivalent 

 of the Pennsylvania Anthracite strip, though it does not coincide with 

 that of the Devonian. Apparentl}^ the depth of water was not con- 

 siderable in any portion, except possibly in the Cumberland plateau of 

 Tennessee, for at most localities the limestone is very impure and the 

 deposit was interrupted several times by sandstones. 



THE SHENANGO 



The Shenango overlaps the Maxville in Pennsylvania and reaches 

 northward, almost to the line of New York. At, the west it barely crosses 

 the Ohio line and the boundary lies but little beyond Pennsylvania 

 to the southern line of that state. In West Virginia the Shenango is 

 wanting in Wetzel, Tyler, Pleasants, Ritchie, most of Doddridge and 

 Wood counties, is very thin in the northern Panhandle, and is very ir- 

 regular in many other counties of the state. The Maxville underlies 

 the Coal Measures directly in Ohio, and in Kentucky the western limit 

 of Shenango is at some distance east from that of the Maxville. In 

 western Pennsylvania, as shown l)y oil-well records, the Shenango is 

 very thin, rarely exceeding 100 feet and often wanting. Even in the 

 Allegheny area of that state it is insignificant, the whole Mauch Chunk 

 section varying from 75 feet in Tioga to 300 feet in Blair, and appar- 

 ently not much more in Somerset county ; but farther south, under the 

 Briery Viaduct axis. White found 370 feet, while on the Potomac it is 

 not less than 650 feet. In the Anthracite strip it is 75 feet at Scranton, 

 and increases southwardly to about 600 feet or more in the southern 

 field. 



Under West Virginia, along the line of the Pennsylvania Alleghenies 

 and westward it decreases rapidly, but along a line somewhat farther 



XIII— Bull. Geol. Soc. Am., Vol. 14, 1902 



