C. S. Prosser — Names for the formations, etc. 191 



Akt. XV. — Names for the formations of the Ohio Coal- 

 measures /* by Charles S. Prosser. 



Field work during the past three years has acquainted the 

 writer with the formations composing the Coal-measures of 

 southwestern Pennsylvania, Maryland and northern West Vir- 

 ginia. It was, therefore, quite natural in reviewing the classi- 

 fication of the Ohio formations that those of the Coal-measures 

 should be among the first to be considered. 



The Ohio Geological Reports contain a wealth of statements 

 regarding the details of the formations and some that are 

 conflicting. The writer makes no claim to have harmonized 

 these various differences, but he has acquainted himself with 

 the general nature and limits of the formations, so that he is 

 able to compare the Ohio classification with that of the Appa- 

 lachian. 



Without attempting to trace the complete development, the 

 more important features of the classification of the Appalachian 

 Coal-measures may be briefly summarized. 



Henry D. Rogers, in the final report of the First Geological 

 Survey of Pennsylvania, proposed and defined the following 

 divisions of the coal strata, or Serai series as he termed them, 

 which are arranged in descending order : 



Upper Barren Coal-shales. 

 Upper Productive Coal-measures. 

 Lower Barren Coal-shales. 

 Lower Productive Coal-measures. 



Serai conglomerate (or lowest division of the Coal- 

 measures.)! 



Under the description of the divisions the names are slightly 

 modified and there is a lack of uniformity in the wording in 

 the several places in which the names occur, but the following, 

 omitting the conglomerate, is an approximation : 



Newer Coal-shales or Upper Barren group. 

 Upper or Newer Coal-measures. 

 Older Coal-shales or Lower Barren group. 

 Older or Lower Coal-measures. J 



The Lower Barren group was defined as having " for its 

 inferior limit the top of the Upper Freeport coal, and for its 

 superior boundary the bottom of the great Pittsburg bed."§ 

 This also fixed the top of the Lower Coal-measures, the base 



* Presented to the tenth meeting of the Ohio State Academy of Science, 

 Columbus, December 27, 1900. 



f Geology Pennsylvania, vol. i, 1858, p. 109. 



% Ibid., vol. ii, pt. 1, pp. 16-20. §Ibid., p. 19. 



Am. Jour. Sci.— Fourth Series, Vol. XI, No. 63.— March, 1901. 

 13 



