The Shinumo Area. 373 



writer is also indebted for the identification of Cambrian 

 fossils, for a list of the Cambrian fossils found in the region, 

 and for assistance in interpreting the stratigraphy. 



To Professor Joseph Barrell, to Professor Charles Schu- 

 chert, and to Professor Louis V. Pirsson, all of Yale University, 

 the most sincere thanks are due for continued interest and 

 advice during all stages of the work. To Mr. W. W. Bass the 

 writer is indebted for material assistance and guidance during 

 his work in the field. 



Geologic Nomenclature. — The geologic names employed in 

 this article are revised names recently authorized by the 

 United States Geological Survey, with the exception of those of 

 the Cambrian, which as yet have not been formally revised. 

 The first table below gives the rock formations of the Shinumo 

 area in terms of the revised terminology, while the second 

 table gives the equivalent of the newer in the older nomen- 

 clature. 



I. 



Geologic column of the Shinumo Area. 

 System Series Group Formation 



f f Kaibab limestone 



Pennsylvanian Aubrey _ - \ Coconino sandstone 



Carboniferous \ ^ Supai formation 



I Pennsylvanian and -d ^ n -d -i n v . 



[ Mississippian Redwa11 " Redwall hmestone 



(Unconformity of erosion without uniformity of dip) 



( Acadian ( " Marbled limestone" 



Cambrian .. -J. , , s ara t p-an^ "' ^onto _. 1 " Tonto shale" 



° '' (" Tonto sandstone " 



(Great angular unconformity) 



Algonkian Grand Canyon . _ . Unkar 



(Greatest angular unconformity) 

 Archean Vishnu 



IT. 



Classic Nomenclature of the reports of 

 Revised Nomenclature Duttp?i, Gilbert, and Walcott. 



Formation Formation Group 



Kaibab limestone Cherty limestone -- ) tt a "u 



Coconino sandstone.... Cross-bedded sandstone ._ j Upper Aubre y 



Supai formation. . . ... Lower Aubrey sandstone. _ Lower Aubrey 



Reel wall limestone Redwall limestone, Red wall 



"Marbled limestone" .. Marbled limestone .. ) TT m 



"Tonto shale" Tonto shale j- Upper Tonto 



" Tonto sandstone " Tonto sandstone Lower Tonto 



