476 H. ^'. SHIMEE PERMO-TRIASSIC OF XOETHAVESTERX ARIZONA 



(7. XATAJO SPRIXG 



From the Grand Canyon to just north of the Little Colorado Kiver, at 



Tanners Crossing, the trail rests upon the Upper Kaibab limestone : north 



of this, through the Painted Desert to Cedar Eidge. it runs over the 



Moenkopi and Shinarump, ^hile to the north of Cedar Eidge, and thus 



to Xavajo Spring, it again runs largely over the upper Kaibab limestone. 



Contact between the Kaibab and Moenkopi was frequently noticed from 



Cedar Eidge north. Immediately to the south of Xavajo Spring occurs 



the f olloTving typical section : 



Feet 



1. Red Moenkopi shales. 



2. Greenish shales (included with the Moenkopi » 5 



3. Kaibab limestone S 



The upper 2 feet of this limestone contain much limestone breccia, 

 while its uppermost surface is slightly uneven. As the junction of the 

 Kaibab and Moenkopi thus give indications of an erosion interval and the 

 strata have similar dips, the contact of the strata is a disconformable 

 one. 



e. HOUSE ROCK T ALLEY 



From Xavajo Spring to Lees Terry the trail passes over the Kaibab 

 and Moenkopi beds in approximately equal proportions; and again, west 

 of the Colorado Eiver, to the southwest of Lees Ferry, for some 10 miles. 

 Beyond this to House Eock Valley it runs entirely upon the sands of the 

 ]\Ioenkopi and Shinarump. These sands and clays mantle the hard 

 Kaibab limestone only for several miles to the south of the trail, as they 

 do to the west of the Echo Cliff trail : beyond this the rapid erosion caused 

 by the deep Colorado Eiver has in most cases removed these softer strata. 

 This rapid erosion causes numerous land slides in both the Vermilion 

 Cliffs and Echo Cliffs. 



The upper Kaibab limestone is well exposed along the western edge of 

 House Eock Valley. The following section was made at the southern 

 end of this valley, in a canyon immediately west of House Eock Eanch. 

 This canyon is cut into the east Kaibab Monocline, the great fold, which, 

 carrying these strata upward to the west to an elevation of 2,500-4,000 

 feet higher than the ^larble Platform, forms the Kaibab Plateau. The 

 winding canyon was apparently made by a meandering stream let dowii 

 upon this ancient monocline by the plateau-like Pliocene upheaval. This 

 section, like the others, was made from the top downward. 



Feet 

 1. Brownish rellow limestone 14 



