TIIK OLDER MESOZOIC OF AKIZOXA. 25 



appear in tli'cat foivo in the valley of Lcroiix \\ asli. llci'c tlicv cover an 

 area of nearly 100 square miles and form two ureal amphitheatei's of 

 veritable badlands. The <x,ivn\ \'ariety and symmelry in (he foi'm of 

 these hutles and I'idfjes, liowever, as well as (he variegated and iridescent 

 colors tha( pr(>vail, rendei- (hem a magnihcent spectacle. They can he 

 seen from lh(> soudieast for a distance of 20 miles as a white line. Viewed 

 from th(^ top of the mesa otit of which they have been carved, th(> denuda- 

 tion having been ai'res(ed at a particular poini, they reveal more com- 

 pletel}' than at any olhei' place the true character of this memljer. In 

 the Petrified Forest the Leroux Ijeds are also well developed, and the 

 \-ariegated marls ai'e found only half a mile east of the Lower Forest. 

 The buttes her(> are rather large and well tleveloped, and Ijones of the 

 Belodont occui- in them. Li the northern part of the Petrified Forest 

 region the variegated marls lie somewhat farther to the east. What is 

 called the Middle Forest lies in the midst of them, and the petrified wood, 

 as everybody has oljserved, differs here considerably in its constitution 

 and coloration from that of the Upper and Low(>r forests, which lie in the 

 horizon of the conglomerate member. 



As was remarked when treating of the conglomerates, these variegated 

 marls are actuall>' foiuid stratified between the sandstones by the trans- 

 formation of certain sliales into marls. If these beds are carefully traced 

 a short distance in the direction of the dip they will be seen to thicken 

 very rapidly and soon to take on the character of the true variegated marls. 

 As they start from underneath a bed of sandstone which caps the conglom- 

 erates, and which does not so readily pass into marl, the btittes that are 

 first formed are usually topped out 1 jy a block of this sandstone, and it is 

 necessary to proceed some distance farther in the direction of the clip to 

 reach a point where the sandstones disappeai'. This, however, ultimately 

 takes place and the marl beds thicken to such an extent that they have to 

 be regarded as virtually overlying the conglomerates. In fact, in the 

 bed of the Moencopie Wash, on both sides of which these beds are so well 

 developed, the conglomerates can he seen distinctly passing under the 

 marls. 



For the purposes of our expedition the variegated marls constituted 

 the most impoi-tant subdivision of the entire group. But as we have 

 seen, their maximum thickness is about 400 feet, and there remain still 



