428 II E. Gregory — Shinarump Conglomerate. 



mation, which is the equivalent of the Shinarump of Powell." 



"Although perhaps the most prominent feature of this forma- 

 tion is the so-called conglomerate, which sometimes is in truth 

 deserving of that name, and contains somewhat large but always 

 well-worn pebbles and cobbles derived from underlying forma- 

 tions, it rarely happens that this aspect of the beds constitutes the 

 major portion of them. In the first place, the conglomerate tends 

 to shade off into coarse gravels and then into true sandstones. 

 These sandstones are of a light color, contrasting strongly with 

 the dark-brown sandstones of the Moencopie already described. 

 They are, moreover, always more or less cross-bedded and usually 

 exhibit lines of pebbles running through them in various direc- 

 tions. These are true sandstones, very hard, devoid of alumina, 

 and scarcely affected by the winds, so that their angles are 

 usually sharp and the ledges they form are abrupt and jagged. 

 Although the sandstones proper generally occur lower down, there 

 is no uniformity in this arrangement, and sandstones are often 

 found in the middle and conglomerates more rarely at the top. 

 But in addition to these the Lithodendron member embraces other 

 classes of beds. There is a well-stratified layer of thinnish 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 member 

 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 conglomerate in places 

 where the Lithodendron beds are comparatively thin, as in the 

 lower valley of the Little Colorado, where they are only about 

 300 feet in thickness. This feature is not very prominent, but at 

 other places, as in the Petrified Forest region, where the Litho- 

 dendron beds attain their maximum thickness of 700 or 800 feet, 

 this tendency on the part of certain beds to become transformed 

 into marls is the most marked feature of the member. 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 beds, 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 w T hich taken together form the 

 beautifully banded cliffs that are seen throughout the Petrified 

 Forest, especially along its northern flank. It thus becomes neces- 

 sary 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." — (Ward, IT. S. Geol. Surv.,Mon. XLVIII, 

 pp. 20-21. 



It is evident that the Lithodendron member of Ward and 

 the original Shinarump conglomerate of Powell lack not only 

 family but racial likeness. I fully agree with Cross* that such 

 * Jour. Geol., xvi, pp. 111-112, 1908. 



