Ashburner.l •->'^^ (Feb. 16, 



alternating with red shale and containing occasional beds of fossiliferous, 

 shaly limestone. 



The Salina group tliins in this district to the south-east, being thicker 

 on tlie Jacks Mountain range than it is along Blacklog Mountain. It 

 makes a valley and is of no economical value. 



Niagara Limestone. 



The Niagara limestone seems to be without a representative in Penn- 

 sylvania. 



In a section which was constructed through Jacks Mountain at Mount 

 Union, a limestone bed 3 feet thick was located 232 feet above the top of 

 the Clinton red shale, which was supposed to be the representative of the 

 Niagara limestone ; the intervening space between this and the Clinton 

 being filled with a soft, argillaceous, calcareous shale. The occurrence of 

 the Niagara limestone here, as well as at Logan Gap 25 miles to the north- 

 east, where a similar bed 4 feet thick was found, is extremely doubtful. 

 A careful search for its representative at Rockhill Gap in Blacklog Moun- 

 tain, and on each side of the Jacks Mountain anticlinal at Three Springs, 

 and Saltillo, failed to bring it to light. It is questionable in the author's 

 mind whether the Niagara measures which form such a marked feature 

 in the geology of northern New York has in this section of Pennsylvania 

 a distinct representative. While this epoch seems to be vacant in our 

 paleozoic column, the Salina rocks, which occur directly above the Niagara, 

 seem to be totally different in character from the New York strata, where 

 they are composed of shales, marls and marly sandstones with impure lime- 

 stone ; ours being almost entirely destitute of fossils. Is it not possible 

 that the strata which are included between the bottom of the Water lime 

 shale and the top of the Clinton red shale represent equally or conjointly 

 the Salina and Niagara groups of New York '? 



No. V. Clinton {Surgent) Shales. 



SalMllo. Orhisoniii. 



1. Red shale (Nos. 21, 2C and 19) Thickness 270 feet. 233 feet. 



2. Upper olive shale (Nos. 18 to 15 inclusive) " 162 " 163 



3. Ore sandstone and fossil ore (Nos. 14to 11) " 42 " 54 zb " 



4. Lower olive shale (Nos. 10 and 9) " " 660 



1. The upper part of the red shale consists of silicious massive red shale 

 having a rhombohedral fracture. Toward the lower part the red ghale be- 

 comes more argillaceous and contains thin alternations of gray and green 

 calcareous shale, while at the bottom there are beds of red shaly sandstone 

 having seams of calcitc running through the mass. 



2. The Upper olive shale consists of yellow, olive and gray calcareous 

 shale containing seams of blue fossiliferous limestone ; the lower part form- 

 ing tlie hanging wall of the fossil ore beds is composed of a light yellow 

 argillaceous lime shale. 



3. The fossil iron ore beds occurring above the ore sandstone have been 

 extensively developed in Rockhill Gap by the Rockhill Iron and Coal Co. 



