250 C. W. TOM LIN SON 



The large and varied vertebrate fauna which has now been 

 described from the clastic members of the Red Beds series in various 

 parts of the Southwest 1 includes no forms requiring other than 

 a land or fresh-water habitat, with the exception of fish remains 

 in some of the marine beds just mentioned. In general, then, it 

 is true that the paleontological evidence corroborates the purely 

 stratigraphic and lithologic evidence for a continental origin for 

 at least the greater part of the Red Beds. In certain places and 

 at certain horizons the fossil remains, both plant and animal, are 

 sufficiently abundant and of such types as to eliminate the possi- 

 bility of extreme aridity as a continuously prevalent condition. 

 The bone beds and petrified forests of northeastern Arizona, for 

 instance, prove that during the time of deposition of the Shinarump 

 group, 2 at least, there was a water supply in that vicinity sufficient 

 to permit the support of abundant land life, both vegetable and 

 animal. It is possible, however, that this water supply was derived 

 from precipitation in a distant region, like the waters of the Nile 

 delta. In the underlying Permian, which contains more salt and 

 gypsum than the other members of the series in this district, 

 vertebrate remains are absent. The Permian of the neighboring 

 Kanab Plateau has yielded an extensive invertebrate fauna 3 sug- 

 gesting brackish-water environment. 4 



Summary. — The most salient of the facts and inferences brought 

 out by the foregoing discussion of the significance of features other 

 than color as to the conditions of deposition of the Red Beds may 

 be summarized as follows: (i) rapid erosion on land-masses of 

 considerable relief; (2) decomposition not complete in advance of 

 transportation; (3) sediments diminishing in thickness and in 

 coarseness of grain away from sources of material, and clastic 



1 See especially various publications by S. \V. Williston in the Journal of Geology, 

 1903-13- 



2 L. F. Ward, "Geology of the Little Colorado Valley," Am. Jour. Sci., 4th 

 Ser., XII (1901), 401-13. On p. 405 is the following statement: "The Shinarump 

 constitutes the horizon of siliciiied trunks and there is no part of it in which fossil 

 wood does not occur in great abundance." 



3 See C. D. Walcott, "The Permian ai^d Other Paleozoic Groups of the Kanab 

 Valley, Arizona," Am. Jour. Set., 3d Ser., XX (1880), ::i. 



4 Interpretation by Eliot Blackwelder (personal communication). 



