624 CHARLES BUTTS 



On the New Portage Branch of the Pennsylvania Railroad the 

 contact of the Hamilton and Genesee shale can be closely located 

 about I mile northwest of Newry, where fragments of limestone full 

 of Hamilton fossils were found at the base of an outcrop of the Gene- 

 see black shale. The same contact is well exposed in the road 

 between Claysburg and Queen on the crest of a spur \ mile northeast 

 of Smoky Run. At this point also a thin, impure limestone with 

 Hamilton fossils occurs at the base of the black shale. The thick- 

 ness of the Hamilton can be determined only approximately, since 

 in none of the sections studied could the bottom be determined, 

 nor were there a sufficient number of exposures to afford a reliable 

 determination of the average dip. In Altoona the upper part of the 

 formation is exposed, as already described. The dip of this part is 

 52° to the northwest. At the corner of Fifteenth Street and Sixth 

 Avenue the black shale of the formation was exposed in excavating 

 for the foundation of a schoolhouse. The shale at this point is ver- 

 tical, as shown on the profile section. It is possible that nearer the 

 bottom of the formation in Altoona the shale is overturned. From 

 the meager date at hand it seems that the average dip of 70"^ to the 

 northwest would be' a probable estimate for the formation, assuming 

 that there are no faults or strong variations of dip. The distance 

 between the Oriskany sandstone in the southeast part of Altoona. 

 and the bottom of the Genesee shale at Fourteenth Street and Thir- 

 teenth Avenue, described above, is, by the city map, about 3,300 

 feet, normal to the strike of the rocks. This space is occupied by the 

 Hamilton and Marcellus formations in which the broad Logan Val- 

 ley has been eroded. Calculating from the width of the outcrop 

 and the assumed dip of 70°, the result is 3,100 feet for the thickness 

 of the Hamilton and Marcellus in the Altoona section. 



Genesee shale. — This is a well-defined stratum of black clay shale 

 lying conformably between the Hamilton formation below and the 

 Nunda formation above, and on account of its distinctive character 

 it is important as a horizon-marker in the region. The shale is very 

 fissile, cleaying easily into thin plates and flakes. Its black color is 

 probably due to the presence of carbonaceous matter, as in the type 

 region of western New York. As in the type region, it also contains 

 rather plentiful calcareous concretions. Indeed, the formation pre- 



