252 C. IF. TOM LIN SON 



limonitic ferruginous soils and the dehydration thereof during 

 transportation. The development of ferruginous soils is the chief 

 prerequisite to the deposition of Red Beds of the western type. 



The areas from which the Red Beds derived their materials 

 certainly included uplands, and in part at least they are known to 

 have been possessed of fairly rugged relief; they were therefore 

 in all probability the sites of more abundant rain than fell upon the 

 plains or delta flats upon which the Red Beds were in large part 

 deposited. The combination of well-watered highlands with less 

 humid or semi-arid lowlands furnishes the conditions for the devel- 

 opment of red soils, and at the same time provides for the trans- 

 portation and deposition of the sediments derived from them, 

 without extensive hydration or reduction of the ferric oxide con- 

 stituent during the transfer. 



An unusually extensive development of red soils during the 

 time of deposition of the Red Beds might have been due, in some 

 part at least, to the higher proportion of oxygen inferred by 

 Chamberlin and Salisbury 1 to have existed in the atmosphere at 

 this time. 



SUMMARY 



The several steps which have been followed in the interpreta- 

 tion of the color of the Red Beds, and the results obtained, may be 

 summarized as follows: 



i. The ferruginous matter which gives the Red Beds their 

 color has been present in the series in very nearly its present dis- 

 tribution and arrangement since the time of sedimentation. 



2. This material has suffered no extensive change of ferrous 

 to ferric iron, or vice versa, since the time of sedimentation; the 

 proportion and present distribution of these compounds in the 

 series were influenced most largely by the original' distribution of 

 organic matter. 



3. Changes in the degree of hydration of the ferric oxide in the 

 Red Beds since sedimentation probably have not been of great 

 importance; and hydration probably has been quite as active as 

 the reverse process during this time. 



1 T. C. Chamberlin and R. D. Salisbury, Geology (New York: Henry Holt & Co., 

 1909), II, 665. 



