MISSISSIPPIAN. 415 



The Shenango sandstone has been followed by Dr. White into Trumbull County of Ohio, 

 where it is about 15 feet thick and rests on 80 feet of Meadville shales. Prof. Orton regards the 

 Logan sandstone of Ohio as the Shenango sandstone but includes also in the equivalence the 

 overlying Shenango shales of White, which, as will appear in the second chapter, must be con- 

 sidered with the Mauch Chunk. 



The Logan, in Ohio, is double, sandstone above and conglomerate below, at the typical 

 localities. Followed into Ohio from Pennsylvania the rock becomes finer, the sandstone 

 becoming shale and the conglomerate sandstone. In the counties of Knox, Holmes, Richland, 

 and Coshocton the sandstone is represented by the Olive shales of M. C. Read, which are upward 

 of 200 feet thick, but farther south the mass becomes a fawn-colored even-bedded fine-grained 

 sandstone. The conglomerate gains in coarseness westward and southward, beiag a coarse 

 rock in Wayne, Holmes, Coshocton, Knox, Licking, Fairfield, Hocking, Vinton, and Ross 

 counties, which, as Prof. Orton observes, mark "the northwestern arc of the sea boundary in 

 Sub-Carboniferous time." The conglomerate is not always continuous, there being usually, as 

 Prof. C. L. Herrick has shown, two beds of congloiiierate separated by layers of fine sandstone 

 or even of shale. The pebbles are usually flat, small, and of practically uniform size. Southward 

 from Ross County, along the western outcrop, the rock is less coarse and it ceases to be conglom- 

 erate before reaching the Ohio River, where it is the upper portion of the Kentucky Knobstone. 

 The Logan rests upon the Cuyahoga shales of Orton, varying from 150 to 400 feet, with the 

 Buena Vista sandstone at the base, a persistent bed, identified with the Sharpsville of White 

 and continuous from the Pennsylvania line around the outcrop to the Ohio River at Buena 

 Vista. Below this is the Berea shale, regarded as the equivalent of White's Orangeville, and at 

 the base is the Berea grit, continuous from Lake Erie to the Ohio River, 50 to 75 feet thick, a 

 fine sandstone at the north but somewhat argillaceous at the south. This ripple-marked 

 sandstone is thought by Prof. Orton to be equivalent to the upper part of White's Oil Lake 

 group. ° This rests on the Bedford shales. Herrick has shown that the Logan does not extend 

 so far northward as do the Cuyahoga shales. 



At this point may be inserted a table of approximate correlations worked out 

 by Stevenson/**'' between the Appalachian Basin and the Mississippian section of 

 the Mississippi Valley: 



Lower Carboniferous: 



Shenango and Upper Meadville Northwestern Pennsylvania . . . . ' 



Logan, including Waverly shales Ohio Keokuk Bur- 

 Upper 400 feet of Bedford and Huntingdon Eastern Pennsylvania > lington, and 



Coal-beaiing shales and sandstone Virginia Kinderhook. 



Upper plate of Big Injun West Virginia 



Upper Knobstone of Kentucky Keokuk and 



Biirlington. 



Protean of Saftord Tennessee i 



Lauderdale of McCalley Alabama jKeokuk. 



Lowest Port Payne of Hayes Georgia and eastern Alabama - - - 1 , 



Lowest Newman of Campbell Tennessee and Virginia jUndetermmed . 



The Waverly group of Ohio has recently been traced across Ohio River into 

 Kentucky and certain variations of stratigraphy have been described by Morse and 

 Foerste,^^ who recognize the formations distinguished in Ohio (Bedford, Berea, 

 Sunbury, Cuyahoga, Blackhand, and Logan, in ascending order) but find that the 

 strata below the Cuyahoga thin out toward the south and west and also lose such 

 arenaceous partings as they had at the Ohio. The littoral formations of the Waverly 



o Orton, E., Ohio Survey Repts., vol. 7, 1893, pp. 28 et seq. 



