THE ORIGIN OF RED BEDS 243 



high" 1 between Karakir and Keriya River, in the southern border 

 of the Takla Makan Desert, Chinese Turkestan. Some 40 or 50 

 miles farther north is the district described in the following passage : 

 "..-.. ridge after ridge of sand, fifty to one hundred feet high. 

 .... Their gently sloping backs to windward were gray with a 

 cover of rather coarse sand, while their steep fronts to leeward were 

 pale brick-red with the fine sand of the main desert." 2 



There are in the Red Beds of the western states no sandstones 

 of this type of such great thickness as that of the Nefood sands, 

 yet the possibility must be recognized that there may be local 

 sandstone members of this origin in the series. A region dry 

 enough to admit of the production of great bodies of gypsum might 

 easily be transgressed by shifting sands; or the two types of deposi- 

 tion might exist side by side, as they do today in the region of 

 Lop Nor and Takla Makan. The coarsely cross-bedded sandstones 

 of the Chugwater formation along the eastern base of the Wind 

 River Range in Wyoming, for instance, will bear further inves- 

 tigation with this possibility in mind. 



EVIDENCE OF FEATURES OTHER THAN COLOR AS TO THE CONDITIONS 

 UNDER WHICH THE RED BEDS WERE DEPOSITED 



The wide range in grain shown by the Red Beds of various 

 parts of the West, and the varying quantity of non-clastic sedi- 

 ments in the group, show that a variety of conditions existed in this 

 region during the time the Red Beds were accumulating, as is 

 to be expected from the great extent of the group. What the 

 varying relations were will be pointed out as accurately as possible 

 in the following pages. 



Evidence of conglomerates as to the sites of land-masses. — Con- 

 glomerates, by the pebbles which they contain, display more clearly 

 than other sediments the source of their component materials. We 

 can therefore determine with some confidence the sites of the land- 

 masses which gave rise to the Red Beds, where these are con- 

 glomeratic. In southeastern Oklahoma, Beede 3 has presented 

 facts to show that the lower Red Beds sediments were derived from 



1 Huntington, op. cit., pp. 183-84. 



2 Ibid., pp. 184-85. J Op. cit. 



