THE ORIGIN OF RED BEDS 



A "STUDY OF THE CONDITIONS OF ORIGIN OF THE PERMO- 



CARBONIFEROUS AND TRIASSIC RED BEDS OF 



THE WESTERN UNITED STATES 



C. VV. TOMLINSON 



University of Minnesota 



PART II 



CONDITIONS OF DEPOSITION OF RED CLASTIC SEDIMENTS: 

 MODERN TYPES 



Seven distinct types of partly or wholly clastic modern red 

 sediments have come to the attention of the writer, some of which, 

 however, are closely related. The occurrence of each one of these 

 types and its application to the Red Beds of the western United 

 States is discussed in the following paragraphs. 



Red clay of the deep-sea bottom. — -This material is invariably very 

 fine-grained, it contains little or no terrigenous matter of any kind, 

 and it accumulates very slowly indeed, so that a thickness of it 

 comparable to the total thickness of shales in any series of the 

 western Red Beds is practically inconceivable. Nearly every part 

 of all the series included in the Red Beds group exhibits incon- 

 testable evidence of shallow-water deposition, while the oceanic 

 red clays are exclusively abysmal deposits. Such arguments could 

 be multiplied almost indefinitely; it is quite clear that deep-sea 

 red clay is not related to our problem in any way whatsoever. 



Stream deposits derived from pre-existing Red Beds. — This type 

 of deposits is illustrated by the flood-plain deposits of the Red 

 River of the South, in Texas, Oklahoma, and Louisiana. This 

 type cannot be dismissed so easily, for there are yet in existence 

 masses of pre-Cambrian red sediments within the possible drainage 

 areas tributary to some of the areas of the Red Beds. One objection 

 to this source for the ferruginous matter of the Red Beds is that 

 there were other sources for the sediments in question, nearer than 



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