114 THE DEVONIAN AND CARBONIFEROUS. (bull. 80. 



X. Pocono (Vespertine) sandstone. 



Xd. Upper gray sandstone group 610") 



Xc. New River coal series 313 ( 9 ,„« 



Xb. Middle Conglomerate group 3S0 ( z > 166 



Xa. Lower green sandstone group 830 J 



IX. Catskill (Ponent) Old Red sandstone. 



VIII. Lower Devonian series. 



VIII. D. Chemung A h Transition beds 90 



° } a Olive (Vergeut) shales 860 



VIII. C. Portage (Vergent flags) 1,450 



( c Genessee (Cadeut, upper) slates 325 



VIII. B. Hamilton.*? b Hamilton's Cadeut shale 635 



( a Marcellus (Cadeut, lower) black slate 875 



VIII. A. Upper Helderberg Coruiferous (Postmeridiau) limestone .. 60 



VII. Oriskauy (Meridian) sandstone. 58 



Etc. through the Lower Paleozoic. 



In 1880 Mr. Ashburner completed and published his report 1 on the 

 geology of McKean Couuty. During the reconuoissanoe survey in 1876 

 lie had collected a large number of fossil specimens. He was unable 

 to arrive at any "satisfactory conclusions as to a systematic division 

 of the strata." He " finally decided to group the strata by a study of 

 their lithology, and on this basis to seek to make a connection with 

 sections in those portions of the State where the structure had been 

 clearly defined." 2 Asa result of his studies he published, as one of 

 the sheets, Plate xi. 3 



During the construction of this sheet he indicated the groups of 

 rocks by letters " A, B, O." After it was finished he determined, by 

 comparison with the sections of adjoining counties, the correlations, and 

 tlie highest, A, he called "Pocono," B "Catskill," and C "Chemung." 



In this report the Olean Conglomerate formed the conspicuous base 

 of the Pottsville Conglomerate series, or No. XII of the old classifica- 

 tion. This was, for Ashburner, the base of the Coal Measures and was 

 the equivalent of the Ohio Conglomerate. 4 



Below this conglomerate he reported a series of 500 to 800 feet of rocks 

 which he was obliged to correlate with the Mauch Chunk shales (XI), 

 Pocono sandstone (X), and Red Catskill (IX) of other parts of the State; 

 but the few fossils obtained appeared to him so mingled aud to range 

 so throughout the whole series that he could not subdivide them satis- 

 factorily. Eighteen species, he reported, " are identical with charac- 

 teristic Waverly species," " seven with Chemung species," and he says: 



I am thoroughly convinced that these rocks hold a fauna which is essentially a 

 unit incapable of subdivision, and that this fauna is decidedly of a Subcarbouiferous 

 age. 6 



1 Geol. Survey of Pennsylvania, Report of Progress R : Report on McKean County, and its geological 

 connections with Cameron, Elk, aud Forest Counties, by C A. Ashburner ; pp. 371, 1880. 



2 Report of Progress R., page 29; also see page 292. 



S A series of columnar sections constructed from surface observations and the records of eleven oil 

 wells situated hetween Bradford, in McKean County, and Ridgeway, in Elk County, showing the rela- 

 tion of the Lower Carboniferous coal beds to the Bradford oil-producir g sand and the thickening of 

 the subconglomerate rocks. J. P. Lesley, State geologist; Chas. A. Ashburner, assistant geologist; 

 A. W. Sheafer, aid. 



4 Report of Progress R, pp. 56, 62. 



•Ibid., p. 30. 



