sections 473 



Description of Sections 



IN GENERAL 



The following sections are described in order from those at the south- 

 east to the ones at the northwest. 



a. FROM THE MOGOLLONS TO FLAGSTAFF 



As we traveled from the Basin Eegion (figure 1 ) northward up Oak 

 Creek, the steep plateau escarpment gave excellent sections in the Permian 

 shales and sandstones. The brick-red shales and sandstones of the Supai 

 formation at the foot of the escarpment are overlain by the cross-bedded, 

 gray Coconino sandstone at the plateau's edge, which in turn, farther to 

 the north, dip under the thin, beveled, southern edge of the Kaibab 

 limestone. In the plateau escarpment the upper fifty feet of the Supai 

 are heavily cross-bedded, while the transition to the Coconino is an 

 alternation of red and white sandstone beds. The surface of the plateau 

 from the Eim to Flagstaff is at intervals covered with volcanic debris, 

 concealing the underlying sediments. This dotting by recent volcanic 

 cones and lava flows is characteristic of the entire plateau region of west- 

 ern Xew ]\Iexico and northern Arizona. The surface sedimentary rocks, 

 from a few miles north of the Eim to Flagstaff, are the yellowish to gray 

 lower Kaibab limestone. Two miles directly south of Flagstaff, beside 

 the trail, ledges of this limestone yielded 



Cf. Pustula nehraskensis (Owen) r 

 Composita suMiUta (Hall) r 



Allorisma terminale Hall c 



&. WALNL'T CANYON 



Walnut Canyon is 8 miles southeast of Flagstaff and within the San 

 Francisco Mountain Forest Eeserve. The narrow canyon has been cut 

 into a rolling upland to a depth of 370 feet. For a detailed lithologic 

 section the reader is referred to the article in the American Anthropolo- 

 gist noted above. Briefly, from above downward, the section is as fol- 

 lows : 



Feet 

 1. Alternating yellowish to gray dolomites and limestones 285 



The lower 150 feet contain the most conspicuous strata of the canyon: 

 three prominent projecting ledges, with faces rounded by erosion, and 

 beneath each a continuous cave zone. It is in these caves that the cele- 

 brated cliff-dwellings occur. From these 285 feet the following fossils 

 were identified : 



