1877.1 04:J [Ashburner, 



The surfaces of some of the sandstone strata contain a fine exhibition of 

 ripple marks and impressions of fucoids and characteristic Chemung 

 fossils, Spirifer lUsjuncta, Rhynchonella, &c. 



Thirteen feet from the bottom occurs a brown ferruginous sandstone, 

 No. 101, weathering readily on the surfaces from the oxidation of the iron, 

 the representative of the Larry's Creek ore, which has a continuous range 

 through parts of Lycoming, Clinton and Tioga counties. It attains its 

 maximum thickness on Larry's Creek in Lycoming County, where 

 the principal bed is 3 feet thick. In some localities it resembles closely 

 the Cleveland ore of Yorkshire, England. In this portion of the State the 

 bed is not workable. 



No. VIII. 



Chemung ( Vergent) shales. 



Thickness (Nos. 95 to 85 inclusive), 1860 feet 



Portage ( Vergent) flags. i = 3310' 



Thickness (Nos. 84 to 71 inclusive), 1450 feet 



The limits of the Chemung and Portage taken together are well defined, 

 the upper being topped by the transition strata at the base of the red 

 Catskill, and the lower by the olive slaty and slialy sandstone of the 

 Hamilton period. The horizon between the two epochs is not as well 

 defined and it has been located rather arbitrarily. There are certain large 

 distinctions between the two which it may be well to notice before 

 describing each in detail. 



Both are made up of alternations of shales and sandstones. In the Che- 

 mung the strata are more silicious, while in the Portage they are more 

 argillaceous. In the latter the sandstone is always finer grained and the 

 shale more clayey than in the former. The Portage sandstones are flaggy 

 and at times very shaly, and their alternations with the shale are very fre- 

 quent, although the individual strata are quite thin, the shale predomi- 

 nating. The sandstones of the Chemung are more massive, occur in 

 thicker strata, their alternations with the shale are less frequent and they 

 seem to contain more ferruginous matter, and more micaceous specks. The 

 Chemung strata, particularly the shaly sandstones toward the top, are 

 replete with marine mollusca, particularly brachiopods, while the Portage 

 is extremely poor in fossil life, with the exception of crinoid stems and sea 

 weeds, or fucoids ; although the occurrence of fossil fucoids would not dis- 

 tinguish the epoch, since they are also very abundant in the upper part of 

 the Chemung, but possibly the two are of different types. 



The upper part of the Ghemung is composed of olive-brown and gray 

 massive and sometimes argillaceous sandstone alternating with flaggy 

 sandstone, and red and green shale, both shale and sandstone containing fer- 

 ruginous specks. 



The central portion of the epoch is made up principally of brown, red 

 and gray sandstone and shale : the sandstone is probably more massive than 



PnOC. AMER. PHILOS. SOC. XVI. 99. 3q 



