THE OLDER MESOZOIC OF ARIZONA. 33 



This brilliantly colored petrified wood comes chiefly from the true 

 conglomerates; and, as alread}^ remarked, that of the so-called Middle 

 Forest, which lies farther to the east and has weathered out of the varie- 

 gated marls, is less brilliant, though scarcely less abimdant. At the base 

 of these same marls on Leroux Wash, especially at the lower end of the 

 system, great quantities of logs lie out upon the plain. They have a 

 reddish-brown color, are very large, and look at a distance like so many 

 rusty locomotive boilers. They are broken across into sections. Most of 

 the wood at this horizon, however, is not colored, and it has usually 

 undergone a higher degree of disintegration than the harder trunks from 

 the conglomerates. It shows the structure admirably, at least to all out- 

 ward appearances, and the sections are usually split up into a large num- 

 ber of blocks and ultimately reduced to a mass of chips and splinters, 

 which look so natural that they would not be suspected of being petrified 

 unless picked up and examined closely. Many of the smaller buttes seem 

 to have been occasioned by the presence of logs, which weighted the 

 underlying marls and tended to prevent their being washed or blown 

 away. The result is that many of these buttes have such logs lying on 

 their summits, with the disintegrated material rolling down its slopes. 



In my report on the Petrified Forests of Arizona (p. 15) I mentioned 

 the statements made by MolUiausen and Marcou that they had seen 

 trunks standing erect and evidently in place, and I quoted (p. 16) Doc- 

 tor Newberry's conclusion, agreeing with mine, that this phenomenon 

 probably did not occur. So far as the conglomerates are concerned, 

 I have seen no reason for altering this conclusion, although I would not 

 be as positive now as I was then that cases of the kind will not be found. 

 But with regard to the trunks entombed in the variegated marls, or 

 next horizon above the conglomerates, we practically demonstrated 

 that erect stumps do occur in them. Within a quarter of a mile of 

 the butte from which Mr. Brown found the best preserved vertebrate 

 bones there is a small area, probably 30 or 40 acres, which contains 

 a group of twenty or more such stumps. They are low, rarely rising 

 more than 4 feet above the ground, but some of them are large, having 

 a diameter of from 3 to 4 feet. Nearly the entire trunk above these 

 stumps, as well as all the branches, has wholly disappeared, but the 

 ground is strewn with small chips and blocks. It is a somewhat level 



HON XLvm — 05 3 



