1877.] OOl [Ashburner. 



in the cementing material of the sediment. This is readily shown by the 

 rapid weathering of not only the shale but also the harder sandstone strata 

 in the cuts along the E. B, T. R. R. 



Professor Rogers (Final Report Vol. I, page 141) says of the Chemung : 

 " This formation, remarkable for its general uniformity of composition, 

 appears to have its maximum development in the region of the Juniata 

 near Huntingdon, half way across the Appalachian chain, where its thiclc- 

 ness is 3200 feet." Without reference to its thickness and character in 

 otlier localities our measurement of its thickness (1950 feet) near Hunting- 

 don seems to show that tlie above generalization is hardly well founded. 



The Chemung formation makes both ridges and valleys. The upper part 

 forms a ridge parallel to the mountain of X. The valleys are generally 

 narrow and sharp, for the most part running parallel with the strike. 



Portage rocks make also ridges and valleys, the ridges not as promi- 

 nent as in the Chemung, and the valleys and ravines more irregular, not 

 having such a great tendency to be parallel with the strike of the rocks. 



The mass contains no strata of economical importance. Some of the 

 sandstones are quarried to a limited extent for building stone. Tlie sand- 

 stones and conglomerates forming ilie "oil sands" of north-western Penn- 

 sylvania, which are perhaps cotemporant'ous with the Chemung Epoch, 

 have no representative at Broad Top. 



Genesee (Cadent Upper) Slate. 



Thickness : (Nos. 70 to 67 inclusive) 325 feet. 



Character : Consists of olive, slaty and shaly sandstone alternating with 

 brownisligray flaggy sandstone and dark olive shale ; toward the lower 

 part the sandstone strata disappear, and the shale becomes more argilla- 

 ceous, until finally at the bottom we have dark olive fissile slate with occa- 

 sional seams of a bright brown-colored sandstone from 2 to 4 inches thick. 

 Tlie shale and slate are slightly bituminous and stained with iron. 



These rocks form valleys and are of no economical importance. 



Hamilton (Cadent) Shale. 



Thickness : (N"os. 66 to 63 inclusive) 635 feet. 



Character : Consists in the upper prcrt of gray sandstone flags and shales ; 

 toward the central part the sandstones predominate in a three-fold charac- 

 ter of massive, flaggy and slaty, to the exclusion of the shale. Surf\ices of 

 the sandstones are stained with iron and contain the following fossils : 

 Aoieulopecten priiiceps, Chonetes mwronatus and Chonetes coronata, Gram- 

 mysia, Spirifer granuUfern, Spirifer mucronatus, TentacuUtes, and 

 Aljce, more particularlji- Spiropliyton caudagalli. 



In the loioer part the sandstone is not so massive, being more flaggy and 

 shaly ; the flaggy sandstone at times becoming quite calcareous, and is 

 very much stained with iron. Shale alternates with sandstone, and 

 toward the bottom predominates, being of a gray and dark olive color, 

 sometimes tliinly laminated and fissile. 



