82 DEPARTMENT OF TEE INTERIOR 



2 GEORGE V., A. 1912 



to the sheet occurring in the Sheppard. Though this lava bed of the Kintla 

 has been traced six miles to the westward, it is known to have formed but a 

 single, local outflow of magma, lacking the singular persistence of the Purcell 

 Lava. 



Above the lava, in the Kintla formation, is a thickness of 300 feet of 

 mixed beds: — dominant thin-bedded and purplish sandstone and argillite, in 

 which are intercalated thin beds of light gray silicified (cherty) oolite, weath- 

 ering buff; and thin beds of grayish white compact magnesian sandstone also 

 weathering buff. About 100 feet above the lava there are two conspicuous beds 

 of gray concretionary limestone which weathers gray. Like the oolitic dolomite 

 these gray bands have their complete homologues in the upper part of the Siyeh 

 formation. Above the 300-foot band of variegated sediments the section dis- 

 closed 460 feet of more homogeneous bright red to brownish and purplish thin- 

 bedded argillite and sandstone; the dominant rock is argillite. 



As noted by Willis, erosion has removed an unknown portion of these 

 sediments and 820 feet is, therefore, a minimum estimate of their thickness. 

 The section at the head of Starvation creek canyon, six miles to the west-north- 

 west, afforded only 610 feet of strata in addition to the forty-foot sheet of 

 amygdaloid. In that section the basal sixty-foot variegated argillite is reduced 

 to ten feet of reddish -brown quartzite. The succession is similar to that of 

 the type section but the gray limestone bands were not found and the oolitic 

 structure was not observed in the magnesian interbeds. 



The columnar section for the type locality may be noted : — 



Columnar section of Kintla formation. 



Top, erosion-surface. 



460 feet. — Relatively homogeneous, thin-bedded, bright red, purplish and brownish red argillite and 



subordinate quartzitic sandstone. 

 300 ii Heterogeneous, thin-bedded, red argillite (dominant) and sandstone, gray and brownish 

 sandstone, magnesian, oolitic limestone and gray concretionary limestone. 

 40 ii Amygdaloid. 

 60 " Thin-bedded red argillite, with thin intercalations of magnesian quartzite. 



860 feet. 



Base, conformable top of Sheppard formation. 



A special feature of the argillites is the great abundance of casts of salt- 

 crystals described by Dawson and Willis. The casts represent both complete 

 cubes and the hopper shape of skeleton crystals. (Plate 11.) The cubes are of 

 all sizes up to those 4 cm. or more in diameter. Ripple-marks and sun-cracks, 

 especially the latter, are likewise very abundant. Thin-bedding and minute 

 jointing have rendered the argillites highly fissile; the mountain peaks com- 

 posed of this formation are usually covered with a fine-textured, creeping fels- 

 senmeer which often, over large areas, completely covers the ledges of rock in 

 place. 



