MHiTE.] SUMMARY OF CONCLUSIONS. 917 



11. Further paleobotanio study of the Pottsville formation appears 

 to fully confirm the earlier conclusion, based on the examination of 

 the plants, that the thinner sections of the formation along- the north- 

 ern and western borders of the Appalachian trough do not contain beds 

 as old as those in the lower portions of the thick sections along the 

 eastern border, e. g., in the Schuylkill and Great Flat Top regions. 

 The positions of the respective Jtloras in the sections plainh^ indicate a 

 transo-ression of the sea toward the north and west during- Pottsville 

 time. 



1'2. Both lithologically and paleontologically the Pottsville forma- 

 tion constitutes a division of the Carboniferous coordinate with the 

 "Lower Coal Measures," "Allegheny series," etc. As such it forms 

 the lower member of what may, in a broad sense, be termed the 

 Mesocarboniferous in the Appalachian province. 



13. The lowest beds in the thickest sections, which appear to be 

 continuous by transition with the deposition of the Mauch Chunk red 

 shales, are perhaps to be regarded as coarse, coast-detrital redeposi- 

 tions, contemporaneous with the uppermost beds of red shale or other 

 marine Lower Carboniferous sediments in other regions. The flora 

 of the Lower Lykens division appears to be contemporaneous, in part 

 at least, with that of the Ostrau-Waldenburg (Culm) beds of the Old 

 AYorld. The flora of the Sewanee zone of the Upper Lykens division 

 is perhaps contained in the Millstone grit of Canada and portions of 

 the Old World coal fields, while it is probable that the Upper Inter- 

 mediate division is contemporaneous with a part of the Lower Coal 

 Measures (Westphalian) of Europe.' 



li. The flora of the Pottsville formation is so far identical, in both 

 its generic and its specific composition, with that from the supposed 

 middle Devonian beds at St. John, New Brunswick, as to leave no 

 room for a great difference in the age of the latter. In fact, the 

 plants from the "fern ledges" include a flora essentially equivalent 

 to that of the Sewanee zone, which appears to be represented by a 

 portion of the section at St. John. 



15. Owing to the hitherto unrecognized presence of an overthrust 

 in Sharp Mountain in the vicinity of Lorberry Gap,^ and the conse- 

 quent misidentification of the less valuable coals in Lorberry and 

 Fishing Creek gaps with the Lykens coals, the boundary of the low- 

 est Lykens coal has been represented from Fishing Creek Gap west- 

 ward, on the State mine maps, as close to or north of the crest of 



'The base of the LgwerCoal Measures or Allegheny series m this country appears paleontologically 

 to be nearer the stage of the Middle Coal Measures of Great Britain, or the upper zone of the West- 

 phalian in continental Europe. 



-The discovery of the fault at Lorberry and Fishing Creek gaps was tlic direct result of the testi- 

 mony of the fossil plants, which was later completely corroborated by tlie ordinary stratigraphic 

 method. 



