192 



ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



in the inorganic environment. If this be true, the beginning of a new 

 geological interval of time is marked by the change in the inorganic world 

 which will lead by slow degrees and a multiplicity of processes to the de- 

 velopment or immigration into a definite area, of new forms of life. The 

 interval begins with the establishment of new conditions permitting the 

 establishment of a new life in sufficient abundance to be recognized as con- 

 stituting a new fauna, faunule, or flora. On the other hand, it is very pos- 

 sible that the establishment of new conditions might be followed by the 

 immediate introduction of a new fauna or flora by immigration. These 

 ideas are in strict consonance with the determination of geological intervals 

 on the principles of diastrophism. If any progressive criteria can be de- 

 tected and traced which reveal such a change in the inorganic world, then 

 the evidence from life may be better understood and even in some measure 

 anticipated. 



The commonly obscure and neglected evidence of climatic change induced 

 by the slow and unimpressive uplift of the continent is the one here used, 

 and, as shown above, the progress of the changed climate is recorded in the 

 line which marks the beginning of red sediments and which cuts obliquely 

 across the stratigraphic column. The persistence of the climatic conditions 

 on the east while they migrated west gives the resultant deposits a wedge- 

 shape (see figs. 5 and 6). 



Texas, OWa. Kans. 



Mo. 



111. Ind. Ohio Ohio.W.Va. Penn. 



Duokard 

 Monongahda . 

 Coneroaugh 



FIG. 7. Diagram illustrating in a schematic way the relative position of the sediments formed 

 under Permo-Carboniferous conditions. The land was rising from east to west, but there 

 was continuous sedimentation in the eastern region at the western edge of the rising land of 

 Appalachia. As the land rose slowly the red beds spread toward the west, occupying rela- 

 tively higher positions in the stratigraphic column. It is difficult to illustrate the actual 

 conditions in the diagram, because the " red beds conditions " were advancing, but the wavy 

 lines indicate the surface of the ground relative to these conditions. In Pennsylvania and 

 West Virginia deposition was continuous during the conditions. In Illinois and Indiana 

 deposition had ceased by the time the conditions reached that far west; in Kansas, Oklahoma, 

 and Texas " red- bed conditions" reached the region in time to affect only the uppermost 

 Paleozoic deposits. The upper limit of the red-bed conditions is not known, and so the 

 upper limit of the wedge is indicated by a dotted line. 



By all the commonly accepted canons of correlation and by its strati- 

 graphic position the Dunkard, with its typical Permo-Carboniferous flora, 

 fauna, of invertebrates, and single reported vertebrate (Edaphosaurus) , is 

 the very approximate equivalent of the Wichita-Clear Fork beds of Texas, 

 but both red beds and Permo-Carboniferous vertebrates are found far below 

 the Dunkard in West Virginia and Pennsylvania. They are, however, well 

 within the limits of "Permo-Carboniferous conditions" in those States. 



