INTERPRETATION OF ENVIRONMENTAL CONDITIONS 207 



Monongahela the area showed a very considerable expansion, though in neither 

 case equahng that of the Washington or lower reds of the Conemaugh and in 

 each very much less than that of Pittsburgh reds of the same formation. _ After 

 the deposition of the Uniontown coal bed their area diminished, and during the 

 Washington and Greene the reds became less and less important, appearing at 

 least in, for the most part, thin and rather widely separated deposits, though 

 occasionally, as in Marshall of West Virginia and northern Greene of Penn- 

 sylvania, they attain considerable local importance." 



D. INTERPRETATION OF CONDITIONS IN THE WESTERN 

 PART OF THE EASTERN PROVINCE. 



In eastern Kentucky there are some red and purple shales at the level, 

 approximatetly, of the upper Conemaugh and the lower Monongahela. 

 These are probably the last traces of the more important red beds in West 

 Virginia and Ohio. In western Kentucky, Illinois, and Indiana the red 

 beds do not appear, except for a single local patch just above the coal vii 

 in Illinois. The break in the series of Pennsylvanian deposits caused by the 

 Cincinnati dome makes the exact correlation of the beds in the two parts of 

 the Southern Subprovince impossible, but, as shown in the correlation table, 

 page 48, the deposits in Illinois and Indiana above the probable Mononga- 

 hela-Dunkard line are unchanged in character from those below. It is 

 apparent that the uppermost beds preserved were deposited under condi- 

 tions quite similar to those which prevailed in Pennsylvania and West 

 Virginia during Allegheny and lower Conemaugh time. The advancing 

 climatic change had not reached as far west as these localities when the beds 

 were deposited, although they are at a much higher stratigraphic level 

 than the middle Conemaugh. 



The meaning of the vertebrate-bearing bed near Danville, Illinois, and 

 the river-channel sandstones of Merom, Indiana, have been discussed by the 

 author in Publication 207 of the Carnegie Institution, pages 77 to 80; the 

 evidence shown in this paper of the gradual rise of the land from the east 

 and the migration of the environment toward the west strengthens the sug- 

 gestion made long ago that the Permo-Carboniferous vertebrates found near 

 Danville were embedded in the clays of an excavation of Permo-Carbonifer- 

 ous time in the exposed deposits of Pennsylvanian age. As an alternate 

 hypothesis the absence of the characteristic red deposits of Permo-Carboni- 

 ferous conditions in this region may well be explained by the lack of any 

 adjacent high land from which such deposits could have been derived and 

 the fact that in this lower land the increase of aridity and lowering of 

 temperature were not sufficiently pronounced to destroy an abundant vege- 

 tation the debris from which would have been deposited with the bodies of 

 the animals whose bones are preserved and have reduced any ferric oxide to 

 the ferrous condition, with consequent loss of red color. The extensive 



