Ward — Geology of the Little Colorado Valley. 411 



from the underlying beds, but the limestone ledge is ultimately 

 reached and is sharp and definite. It has a thickness of about 

 10 feet. Over it lie very heavy beds of calcareous materials 

 beginning as mortar beds, such as I have described, but soon 

 taking on more symmetrical forms, closely resembling the marl 

 buttes of the valley below. The color also changes, and many 

 of the buttes are, in whole or in part, of a deep blue or a lively 

 purple. These constitute here the highest beds of the Shina- 

 rump and fossil wood is abundant throughout. Much the same 

 conditions prevail in the Petrified Forest region, but the devel- 

 opment is here much less extensive. 



The Painted Desert Beds. 



It remains to consider the third and highest series of the 

 Older Mesozoic of Arizona. As already stated, these constitute 

 the elevated cliffs that bound the valley of the Little Colorado 

 on the northeast. Although broken through in many places, 

 and practically wanting for long distances, they still constitute 

 what may be regarded as a great wall separating the valley 

 from the region of high mesas that lie in the Moqui and Navajo 

 country. As these beds seem to contain no fossil remains, and 

 as they are throughout the greater part of their extent practi- 

 cally inaccessible from the absence of water, their detailed study 

 has been neglected, and I was able to acquaint myself with 

 them only imperfectly and at a few points. 



There is, however, no place where they are better developed 

 than directly east of Tanner's Crossing, where we remained 

 longest, and on several occasions the attempt was made to reach 

 them from our camp and to examine them closely. Enough 

 was learned to justify the positive statement that they consist 

 almost entirely of sandstones, perfectly stratified, the different 

 layers differing mainly in color, thickness, and fineness of struc- 

 ture. The great central portion constituting the escarpment 

 and having a thickness of about 800 feet is, within these limita- 

 tions, practically homogeneous. The series begins, however, with 

 a bed of orange red sandstone, highly argillaceous, and soft in 

 structure, easily eroded, and readily yielding to the influence 

 of the wind. It has a thickness of about 100 feet and in the 

 lower Colorado region stretches across the broad valley at the 

 base of the escarpment and lies directly upon the uppermost 

 limestones of the Shinarump. Here it forms picturesque and 

 fantastic buttes and chimneys standing out upon the plain. It 

 occurs in the same position overlying the Shinarump on Le 

 Roux Wash and forming the top of the mesa which overlooks 

 the amphitheatres that I have described. It is also seen above 

 the Shinarump series to the east of the Petrified Forest. It is 

 therefore probably safe to assume that this bed is continuous 

 from Echo Cliffs to the boundary line of New Mexico. 



