Ashburner.] OO^ [Feh. 16, 



No. VII. Oriskany {Meridian) Sandstone. 



• 



At Three Springs, Nos. 45, 44 and 43 Thickness 58 feet. 



At Orbisonia " 150 ± " 



The upper part is composed of a coarse-grained ferruginous and calcare- 

 ous sandstone containing a great deal of iron toward the top, and is sur- 

 mounted by a bed of ochreous clay. 



The central portion is made up of a loose, friable sandstone containing 

 pebbles the size of a pea, larger than any found in the upper or lower parts. 



The lower pitrt con?i\sis of a coarse-grained, arenaceous sandstone more 

 fragile than any toward the top of the mass, and breaking into more ir- 

 regular shapes. The sandstone contains a great deal of ferruginous matter 

 and the surfaces are at times coated with peroxide of iron. 



The epoch contains the following fossils : Cyrtoccras €xpansus,Bahnania 

 micrurus, Eatonia peculiaris, Mejamhonia lamellosa, Orthis hipparionyx, 

 Platyceras ventricosa, Pterinea texilis, Rensselceria marylandica, Rensselce- 

 ria ovalis, Rensselceria ovoides, Spirifer arenosus and Spirifer arrectus. 



Tlie species of marine life found in the lower Helderberg limestone 

 seems to have been cut off by the changes which ushered in the Oriskany 

 Epoch, a group of fossils peculiar to it assuming their place. Most of the 

 fossils are remains of moUusks, no vertebrates or remains of land plants 

 have yet been found. So far Paleontology seems to assign a distinct place 

 to the Oriskany between the Silurian and Devonian ages. Viewing the 

 dynamical conditions attending the deposition of the Devonian age Dr. 

 Newberry places the Oriskany at its base; and says : "The Devonian 

 rocks of Ohio form a circle of deposits, which records an invasion of the 

 land by the sea, and presents in its series of strata, a history of the succes- 

 sive stages of that invasion ; first, the mechanical sediment of the Oriskany ; 

 then the Corniferous limestone, the deposit of the open sea ; then mixed 

 mechanical and organic materials ; the mechanical sediments finally pre 

 dominating and indicating a return to land conditions over all the eastern 

 portirnofthe continent." 



The epoch is ridge making, and has three horizons of economical im- 

 portance : 



1st. Upper ore bed, occurring at the upper limit of the sandstone. This 

 bed is seldom workable in Pennsylvania, but is very productive in the 

 valley of the James river, Virginia. In many localities the mass consists 

 merely of the upper strata of the sandstone strongly impregnated with per- 

 oxide of iron. 



2d. In the Juniata Valley where the Oriskany is friable and contains 

 little or no iron, it affords a valuable sand for glass manufacture. 



3d. Lower ore bed, occurring at the junction of the coarser and more 

 arenaceous strata at the bottom of the sandstone with the soft, calcareous 

 yellow layers beneath it. Tliis bed is worked by the Rockhill Iron and 

 Coal Company near Orbisonia and in Hill Valley. 



