THE ORIGIN OF RED BEDS 253 



4. The ferruginous matter of the Red Beds was transported 

 and deposited almost, if not quite, wholly as a mechanical sediment, 

 both independently and as a coating upon grains of other material. 



5. The types of sediments probably most important in the Red 

 Beds group are stream deposits, submarine fluviatile deposits, 

 and playa deposits, all predominantly of red color, and all deriving 

 at least the greater part of their ferric oxide from ferruginous 

 residual soils. Of these types the first is by all odds the most 

 important. 



6. The study of characteristics of the Red Beds other than 

 color bears out the conclusion stated in No. 5. 



7. The inauguration and cessation of Red Beds sedimentation 

 probably were connected closely with climatic and topographic 

 changes involved in the orogenic history of the continent. 



The colors which distinguish Red Beds from other series are 

 due to a combination of lithologic, topographic, and climatic fac- 

 tors in the regions of denudation and in those of deposition, which 

 have not been reproduced over so great an area in more recent 

 times. 



It is apparent that, in accordance with Barren's view, 1 "red 

 color in sediments is not in itself an indication of aridity"; for 

 the material of red ferruginous soils may be transported and 

 deposited in regions of high rainfall, or even under the sea, with- 

 out change of color; and red soils themselves develop in regions 

 of heavy rainfall. But since the dehydration of the limonitic 

 material of non-red ferruginous soils, as well as the continuance 

 of the relatively anhydrous condition of the hematitic material of 

 red soils, is favored by aridity in the regions of transportation and 

 deposition, therefore red sediments should form a larger part of the 

 sediments of arid than of humid regions. 



1 Joseph Barrell, "Upper Devonian Delta of the Appalachian Geosyncline," 

 Am. lour. Sci., 4th Ser., XXXVI (1913), 437. 



