THE ANTHRACITE STRIP 47 



two beds of impure limestone, 2 and 3 feet thick, at 175 and 500 feet re- 

 spectively below the Pottsville, in which he sees the representative of the 

 upper limestone, which becomes so important beyond the Alleghen}^ 

 mountains.* These upper limestones were not seen in Bedford county 

 b}^ Stevenson, but the lower limestone is persistent there and is present 

 at the northern end of the Mount Savage synclinal, where it shows dis- 

 tinctly the curious current bedding which characterizes it at all expo- 

 sures farther west.f 



Little information is available for localities along the easterly front of 

 the Allegheny ])lateau in Pennsylvania. R. H. Sanders's section, in 

 Blair count}^, gives the thickness as 283 feet and shows no trace of lime- 

 stone, I a condition difficult of explanation in view of observations on all 

 sides. Edward Miller found near the Old Portage, in the same county, 

 30 feet of limestone, containing "so large a proportion of silex that it 

 forms good mortar without any admixture of sand," which can be no 

 other than the lower Mauch Chunk limestone, the silicious limestone of 

 southwestern Pennsylvania. § Where the Potomac issues from the Alle- 

 ghanies in Maryland, one has C. C. O'Harra's section, which shows 



Feet 



Mauch Chunk shales 800 



Greenbrier limestone 227 



a total of 1,107 feet. The Mauch Chunk is mostly red shale, but above 

 the middle is a greenish, soft, flaggy sandstone about 100 feet thick, and 

 at the base a brecciated sandstone 4 feet. The Greenbrier is limestone, 

 with thin shales, 70 feet; shales and sandstones, 113 feet, and a silicious 

 limestone, 38 feet, which rests directly on the Pocono.|| Evidently the 

 section varies notabl}^ for within a short distance Rogers reported from 

 Western port: 



Feet Inches 



1. Red sandstones and shales , 650 



2. Limestone, conglomerate, fossiliferous 4 6 



3. Red shale, with a little sandstone 184 11 



4. Silicious limestone, oolitic bands 46 7 



5. Red shale sandstone, some limestone 15 5 



6. Silicious limestone, diagonally bedded weathers like coarse 



freestone 14 4 



7. Limestone 7 



Total 918 9 



*I. C. White : Geology of Huntingdon county (T 3), 1885, pp. 75-76. 



t J. J. Stevenson, vol. T 2, p. 102. 



t R. H. Sanders, cited by Franklin Piatt : Geology of Blair county (T), 1881, p. 13. 



g Edward Miller: Transactions of the Geological Society of Pennsylvania, 1835, vol. i, p. 254, 



II C. C. O'Harra: Maryland Geological Survey, Allegany county, pp. 110-113. 



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



