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GRAND CANYON SECTION 
Taken in its several parts, its Periodic subdivisions if you 
please, this Grand Canyon succession is not supremely impressive, 
in this land of gigantic relief features. There are hundreds of 
sections in this region that are far more imposing. There are 
thicker sections, fuller sections, more illuminating sections, in al¬ 
most any one of the thousand and one desert ranges which stud 
the vast Great Basin plains. It is probably because of the ease of 
distant vision that so exclusive attention is devoted to the Grand 
Canyon section, and that distraction from so many better and near¬ 
by sections is so prevalent. But this very ease of acquired large 
perspective clouds the effort for intensive investigation. Only the 
general features strike the fancy. Were it not for the Grand 
Canyon section the stratigraphy of the entire Southwest would 
have been long ago unravelled and understood, instead of being 
as now virtually in the same uncertain state as it was when first 
brought in to public notice three-quarters of a century ago. 
It is not disparagement of any of the work done in the Canyon 
region to point out some of its stratigraphic limitations. It is not 
decrying the unrivalled spectacle to compare its strata with better 
outcroppings of neighboring localities. It is not detracting one 
whit from its scenic prestige to note some of its terranal short¬ 
comings, or to record where nearby they may be replaced. Most 
urgent desideratum is the establishment of the completest geologic 
record of that vast expanse which we designate commonly as the 
Southwest. 
The geological formations of the Grand Canyon resolve 
themselves into three major groups: The gray rim-rock, the Red 
Wall, and the black crystalline basement supporting the inner 
gorge. The rim-rock appears to represent ^lid Carbonic deposi¬ 
tion. It is the layer termed the Kaibab limestone, which, 500 
feet thick in the Canyon, develops immensely to the eastward, 
until in New Mexico it attains a thickness more than tenfold 
that figure, and where it carries an abundant Missourian fauna. 
The bottom of the Kaibab limestone marks a notable uncon¬ 
formity, although no mention is ever made of the fact in the 
literature relating to the region. It is one of the great uncon¬ 
formities of the North American continent. Everywhere it bevels 
the entire Paleozoic succession beneath, the Proterozoic sediments, 
