THE ORIGIN OF RED BEDS 251 



sediments giving place to non-clastic in the same direction ; (4) flu- 

 viatile deposition most important; (5) all deposits in relatively 

 shallow water, or subaerial; (6) oscillating marine and non-marine 

 conditions at edge, non-marine in most of region of deposition; 

 (7) moderate aridity long continued in some parts of the region 

 of deposition, alternating with less arid conditions in other parts. 

 These conditions coincide to a remarkable degree with those 

 inferred from the study of modern red sediments. 



RELATION OF DIASTROPHISM TO RED BEDS SEDIMENTATION 



It may well be asked at this juncture why it is that earlier 

 Carboniferous elastics underlying the Red Beds of Oklahoma and 

 other states are not similarly colored. The difference in color, 

 since this has been shown to be a feature dating from the time of 

 sedimentation, 1 must be due to differences of some sort in the geo- 

 graphic conditions of the times when the successive series were 

 deposited. One of these differences is the emergence of the plains 

 of deposition. Another may be found in the fact that some, at 

 least, of the highlands from which the Red Beds derived their 

 materials were not in existence in the earlier part of the Paleozoic 

 era. The Arbuckle-Wichita uplift probably dates from the later 

 part of the Pennsylvanian period; and there may have been 

 mountain-building in Colorado at the same time, as the strati- 

 graphic relationships of the scattered Paleozoic sediments in that 

 state seem to indicate. Dr. Blackwelder 2 calls attention in this 

 connection to the fact that the general trend of the Arbuckle- 

 Wichita folding is directly in line with the suspected areas in 

 Colorado. Local climatic changes influencing the type of sedi- 

 mentation may have been brought about by these changes in topog- 

 raphy. The general continental expansion of North America 

 from Pennsylvanian to Jurassic times leads one to expect extreme 

 types of continental climate, including aridity, the localization of 

 which would depend largely on the configuration of the continent. 



The deposition of red sediments derived from ferruginous soils 

 means either the development of red soils and the transportation 

 of the material thereof without hydration, or the development of 



1 See discussion of this point, pp. 162-67, this volume. 



2 Personal communication. 



