432 A. W. GRABAU PALEOZOIC DELTA DEPOSITS OF NORTH AMERICA 



permitted extensive oxidation of the iron componnds in the sands and 

 the rock-floor while they were being transportated or during and after 

 deposition. Studies in desert regions have shown that such oxidation is 

 extensively carried on under arid climatic conditions, with a depressed 

 water table and a scarcity or absence of vegetation. That oxidized 

 beds can be contemporaneous with white, gray, or even black non-oxi- 

 dized beds admits of no doubt, nor that one may merge into the other. 

 Such oxidized beds are not always red at the time of their formation. 

 Indeed, it is more likely that oxidation is always accompanied by a cer- 

 tain amount of hydration, the result being an ochery or yellow tint. 

 Dehydration and the corresponding change to a red color is, as shown by 

 Crosby, a process of ageing, and may take place subsequent even to burial 

 of the oxidized strata. 47 Now, it can only be an exceptional and pecu- 

 liarly local series of conditions, which will permit extensive oxidation 

 away from the source of supply, while near it no such oxidation oc- 

 curs. It is scarcely conceivable that river-spread sediments over a broad 

 emerged area at the foot of a highland region should fail of oxidation in 

 the first 100 miles of their area of sedimentation, but be thoroughly oxi- 

 dized throughout a thickness of over 1,000 feet in the second belt or a 

 distance of 200 miles from the source. Elvers m.a,y perhaps carry sedi- 

 ment from a region of oxidation, through a region where vegetation pre- 

 vents such oxidation and deposit them beyond this point as oxidized 

 sediments, but in any case the region from which the supply is derived 

 is the chief one to suffer oxidation. 



If these conclusions are sound, we must consider that the red Queens- 

 ton shales of the Niagara region are contemporaneous with the red sedi- 

 ments of the Appalachian region, unless we assume that the former are a 

 secondary deposit, the material being derived from the erosion of the 

 older beds. Against such a supposition, however, the relative uniformity 

 of lithic character of the Queenston beds, their thickness, and especially 

 their uniform color, as well as their relation to the inclosing rocks, form 

 a strong argument. A further argument that the beds of western New 

 York were deposited under conditions of aridity is shown by the occur- 

 rence in them of saline waters, this being, indeed, the lowest saliniferous 

 horizon of western New York. I believe that there can be no question 

 but that the Queenston and Juniata are contemporaneous sediments. It 

 is, of course, true that red sedimentation* began earlier in the Appala- 



47 For a full discussion and citation of literature see Barrell. Bull. Geol. Soc. Am., 

 vol. 23, p. 416 et seq. Also A. W. Grabau : Principles of Stratigraphy, A. G. Seiler & 

 Co., 1913. 



* By this term is to he understood the deposition of oxidized sediments, which subse- 

 quently may by dehydration assume a red color, and not that the sediments were neces- 

 sarily red at the time of formation. 



