THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Aet. XLIIL— Geology of the Little Colorado Valley;* by 

 Lestee F. Ward. 



The geology of the Grand Canyon region of northern 

 Arizona has received much attention on the part of geologists 

 and considerable has been written on the higher beds of Meso- 

 zoic age that lie to the eastward in Marble Canyon and farther 

 north, but very little study seems to have been made of the 

 Little Colorado Yalley above the point at the north end of the 

 Colorado Plateau, where it broadens out into a plain. The 

 strata of the Grand Canyon up to and including the junction 

 of the Little Colorado with the Colorado River, consist, as all 

 know, entirely of Paleozoic and pre-Paleozoic rocks, and it is 

 the Carboniferous limestones, or sometimes sandstones (Upper 

 Aubrey), that occupy the surface of both the Colorado and the 

 Kaibab plateaus. But the entire system dips sensibly to the 

 northeast and at any point some distance back from the canyon 

 remnants of Mesozoic rocks occur for many miles before 

 reaching the bed of the Little Colorado. That river, there- 

 fore, practically flows for almost its entire length over Mesozoic 

 strata, but these do not attain their great development except 

 on the northeastern slope of the valley. Here they form sev- 

 eral series of terraces, rising one above another as one recedes 

 from the river, and forming at their maximum development 

 lofty and picturesque escarpments, with brilliantly colored 

 stratification, rivaling in many respects the Grand Canyon 

 itself. The broad arid plains that lie to the southwest of these 

 cliffs have received the name of the Painted Desert, from the 

 circumstance that from any point on this desert these painted 

 cliffs are always in full view. From a great distance they may 



* Published by permission of the Director of the United States Geological 

 Survey. 



Am. Jour. Scl— Fourth Series, Vol. XII, No. 72.— December, 1901. 

 28 



