406 Ward — Geology of the Little Colorado Valley. 



glomerates more rarely at the top. But in addition to these 

 the Shinarump Conglomerate embraces other classes of beds. 

 There is a well-stratified layer of thirmish sandstone shales 

 that is often seen immediately under the heavy sandstone cap. 

 Some of these shales have a grayish color and are highly 

 argillaceous. These layers tend to thicken even within the 

 formation itself, but especially farther out, and what is more 

 significant, they often become transformed into a bluish white 

 marl. This condition can be seen between the beds of con- 

 glomerate in places where the Shinarump Conglomerate is 

 comparatively thin, as in the lower valley of the Little Colo- 

 rado, where it is only about 300 feet in thickness. This 

 feature is not very prominent, but at other places, as in the 

 Petrified Forest region where the Shinarump attains its maxi- 

 mum thickness of TOO or 800 feet, this tendency on the part 

 of certain beds to become transformed into marls is the most 

 marked feature of the formation. The marls here occupy 

 much more than half of the beds. They are very varied in 

 color, showing besides the white and blue tints a great variety 

 of darker ones such as pink, purple, and buff. These heavy 

 marl beds, of which there may be several in the same cliff, 

 are interstratified between conglomerates, coarse gravels, and 

 cross-bedded sandstones, all of which taken together form the 

 beautifully banded cliffs that are seen throughout the Petrified 

 Forest, and especially along its northern flank. It thus 

 becomes necessary to include under one designation all of 

 these varying beds, which often change the one into the other 

 even at the same horizon within short distances, and rather 

 than adopt a new name I have preferred to call them all the 

 Shinarump Conglomerate. 



It remains to mention certain minor features, which are not 

 universal, 'but which, nevertheless, have considerable import- 

 ance. In the lower Little Colorado Valley there occur numer- 

 ous somewhat calcareous clay lenses, the lime taking the form 

 of bright white stripes, while the clay is usually purple or 

 pink. These are very distinct objects and vary in size from 

 lenses 10 or even 20 feet in length to small lenticular blocks or 

 somewhat oval or even spherical clay balls or pellets. These 

 calcareous clay inclusions are scarcely seen farther to the south- 

 east, but on Ped Butte they are well marked and here the 

 clay becomes brilliant red and constitutes a true paint stone. 

 Another fact to be noted in connection with the Shinarump 

 Conglomerate is that at certain localities, and notably on Red 

 Butte, there is at its base a clear indication of a transition to 

 the Moencopie beds. The conglomerates proper are under- 

 lain by argillaceous shales closely resembling those of the 

 Moencopie beds, but beneath these is a sandstone ledge which 

 cannot be referred to the lower division, as it is more or less 



