Scfiuchert — Cambrian of the Grand Canyon of Arizona. 365 



thickness near Hermit camp of about 200 feet (fig. 4). 

 Elsewhere it varies between 100 and 250 feet. Within 

 the inner gorge it is a cliff maker and especially so in its 

 lower two thirds ; otherwise it determines the floor of 

 the Tonto platform. The lower 150 feet consists of 

 coarse, brownish, much cross-bedded sandstones that are 

 often slightly glauconitic, followed by 25 feet of finer 

 grained brown and glauconitic sandstones with shale 



Fig. 5. 



Fig. 5. Contact between Tapeats sandstone (T) and Vishnu series (II) near 

 Hermit camp. Distance along contact about 40 feet. 



beds. At the' top is a white cross-bedded sandstone 

 about 25 feet thick, and here was seen very rarely a 

 fragment of an obolid shell. 



The basal bed of the Tapeats, about 1 foot in thick- 

 ness, has many slightly worn subangular pieces of quartz 

 averaging about an inch across. The stratum is, how- 

 ever, a jumble of small and large pieces of the Vishnu up 

 to one foot in length, consisting of hard and soft rocks 

 lying in the shallow depressions of the ancient peneplain. 



