ransome: the ray quadrangle 381 



the Ray quadrangle it is 15 feet thick and contains abundant 

 well-rounded pebbles, some of which are quart zite. In the 

 vicinity of Roosevelt, 35 miles northwest of Ray, the conglomer- 

 ate rests on granite and is 30 feet thick with well-rounded pebbles 

 up to 9 inches in diameter. The same conglomerate has been 

 recognized in the Santa Catalina Range about 45 miles south- 

 southeast of Ray, where its thickness at one locality was esti- 

 mated at about 12 feet. The original distribution of this basal 

 conglomerate over an area at least 85 miles from northwest to 

 southeast and at least 40 miles wide is well established. In some 

 places weathered, disintegrated, and recemented granitic detritus, 

 or arkose, lies between the conglomerate aitd the pre-Cambrian 

 granite. 



Pioneer shale. Overlying the Scanlan conglomerate conform- 

 ably is the Pioneer shale, its type locahty being Pioneer Moun- 

 tain in the northeastern part of the Ray quadrangle, although 

 the name was first applied in the Globe report.- 



As a rule the Pioneer formation consists of dark reddish brown, 

 more or less arenaceous shale composed largely of fine arkosic 

 detritus with little or no calcareous material. At many places 

 the shale grades downward into arkosic sandstone and in the 

 Apache Mountains, northeast of Globe, 200 feet of this sand- 

 stone intervenes between the Scanlan conglomerate and the 

 typical shale. Near Roosevelt the lower part of the formation 

 consists of alternating beds of sandstone and shale. Abundant 

 round or elliptical spots, of light-buff or greenish color, are 

 highly characteristic of the shale. The average thickness of 

 the Pioneer formation in the Ray quadrangle is about 150 feet. 

 It is 200 feet thick, however, in the northeastern part of the 

 quadrangle. In the canyon of Salt River, below the Roosevelt 

 dam, the formation has an estimated thickness of 250 feet. 



Barnes conglomerate. The Barnes conglomerate, first described 

 in the Globe report^ takes its name from Barnes Peak in the 

 northwest part of the Globe quadrangle. In its typical develop- 

 ment it consists of smooth pebbles of white quartz and of hard 



2 Op. cit., p. 31. 

 ^ Op. cit., p. 31. 



