440 STEVENSON— THE FORMATION OF COAL BEDS, [-^ov i, 



Stone and extending upward for 75 feet or more, tells of stream 

 erosions in a great area. That limestone is replaced with sandstone 

 at many places in Pennsylvania is shown by I. C. White. 

 Grimsley^® has described a " washout," which he observed at New 

 Cumberland, on the Ohio River in West Virginia. It involves the 

 Middle Kittanning coal bed and the associated rocks. The course 

 of the " roll " is S. 30° E. The replacing sandstone is exposed 

 along a stream near the town, where it is 1,200 feet wide. Ap- 

 proaching from the west, the coal is cut ofif, its thick underlying 

 clay becomes sandy and the sandstone mass becomes continuous 

 with that below the clay. This valley was filled during deposition 

 of the sandstone which elsewhere forms the roof of the coal bed. 

 Within the " roll," nodular and lenticular masses of coal occur 

 along with numerous long strings, one and a half to 3 inches thick. 

 This cut out was traced for about 2 miles. 



The same horizon is marked by stream cutting in a considerable 

 part of the Hocking Valley coal field of Ohio. The phenomena 

 were described first by E. B. Andrews and at a later date by 

 Orton.^^ The latter is not inclined to believe that the work was 

 done by streams, thinking rather that it was done by the ocean. 



Illustrations of similar conditions are found a'bundantly in coal 

 fields elsewhere. Ashley^'' has described the " Coxville Carbon- 

 iferous river " in Parke county, Indiana, a Coal Measures valley 

 filled with sandstone. It is 600 feet broad and the sandstone is 

 exposed to a depth of 40 feet. On each side the sandstone spreads 

 above the exposure and is seen resting on a coal bed. At another 

 locality, the sandstone is 180 to 190 feet thick. At Silver Island 

 in Fountain county and elsewhere the same features are shown at 

 this horizon. It had been suggested that these, with some others, 

 are parts of a drainage system, but Ashley hesitated to accept this, 

 believing that if it were true there should be evidence of greater 

 unconformity than has been observed. He remarks, however, that 



^* G. P. Grimsley, " Clays, Limestones and Cements," West Virginia Geol. 



Survey, Vol. IIL, 1905, pp. 215, 216. 



"E. Orton, Ohio Geol. Survey, Vol. V., 1884, pp. 936, 937- 



^ G. H. Ashley, " The Coal Deposits of Indiana," Twenty-third Ann. 



Rep. Indiana Geol. Survey, 1899, pp. 272, 2>n, 385, 386, 552, 821, 956, 1261. 



