THE ORIGIN OF RED BEDS 175 



Another source of heat which might be suggested is that of 

 igneous intrusions. The absence of igneous rocks in the greater 

 part of the western Red Beds, including the regions where drilling 

 has shown the colors to be unchanged at depth, proves that this has 

 not been a factor of widespread importance. Heat due to regional 

 metamorphism or to structural deformation of any sort must like- 

 wise be discredited here, as the Red Beds are substantially flat- 

 lying over vast areas, and are nowhere intensely deformed or 

 metamorphosed, except locally in the immediate neighborhood of 

 igneous bodies. 1 That compression due to the weight of overlying 

 sediments may have created sufficient heat for the accomplishment 

 of extensive dehydration must be recognized as a possibility, 

 although in many areas where the Red Beds occur the requisite 

 overlying sediments are not known ever to have existed, and the 

 uppermost members of the series in these localities are as brilliantly 

 red as any below them. Furthermore, pressure creates heat only 

 by the performance of mechanical work, and microscopic study of 

 the Red Beds reveals no evidence of internal deformation. 



Crosby 2 concludes that the process of dehydration of ferric oxide 

 is largely a spontaneous one, which goes on independently of any 

 outside influence whatsoever, though aided by high temperatures. 

 He states as evidence in support of this hypothesis that the red 

 sedimentary formations and the red iron ores of the world occur in 

 the older systems chiefly, while in the younger systems ferruginous 

 formations and ores are commonly yellow. There are, however, 

 many exceptions to this rule, such as the buff Cambrian sandstones 

 of the Mississippi Valley, the modern red residual iron ores of Cuba, 

 and the dark-red hematitic bog ores in Sweden and elsewhere; and 

 furthermore, the dehydration of the pre-Cambrian red sandstones 

 and argillites may be attributed in some cases partly to regional 

 metamorphism, which has not affected the younger beds. 



Richardson 3 has given much weight to this "essentially spon- 

 taneous" process. He states that "the dehydration of ferric 

 hydrates tends to go on under ordinary conditions without any 

 unusual cause." 4 "This has been repeatedly demonstrated by 

 experiment. ' ' s But none of the experimenters to whom Richardson 



1 See p. 168. - Op. cit. 3 op. cit., p. 392. « Ibid. = Ibid. 



