78 DEPARTMENT OF TEE INTERIOR 



2 GEORGE V„ A. 1912 

 At the head of Starvation canyon the section is slightly different:— 



Top, conformable base of Kintla formation. 



500 feet. — The staple, thin-bedded, buff-weathering silicious dolomite. 

 35 " Basic, amygdaloidal lava. 



50 " Medium to thin-bedded reddish and gray, interbedded sandstone and 

 argillites, with thin intercalations of buff-weathering dolomitic rock. 



585 feet. 



Base, conformable top of Purcell Lava. 



Of the two columnar sections the former is to be regarded as the more 

 typical for the Boundary belt. The intercalated bed of lava represents a quite 

 local outflow, not found in sections a few miles to the eastward, nor anywhere 

 in the Galton range. 



The basal red beds of the formation are similar in character to the upper- 

 most strata of the Siyeh formation and are like common phases of the Kintla. 

 Ripple-marks and especially sun-cracks are common here as in all other strata 

 below the base of the Kintla formation. 



Under the microscope the most common rock of the Sheppard is seen to be 

 a highly impure, very finely granular, homogeneous mass of carbonate. It occurs 

 in the form of pale brownish grains, varying from 0-005 mm. or less to 0-03 mm. 

 in diameter and averaging about 0-02 mm. The larger grains often show 

 rhombohedral outlines. These are enclosed in a fine-grained base of anhedral 

 carbonate grains, quartz, sericite, and probably feldspar fragments of minute 

 size. Along with these fairly determinable constituents the base carries a con- 

 siderable amount of colourless, nearly isotropic material, which seems to be 

 identical with the cement found in the Siyeh limestone and certain phases of 

 the Altyn dolomite. As in the latter rocks, this material must carry much of 

 the combined water, which here forms nearly two per cent of the whole rock. 



The specific gravity of the dominant phase, as represented in three fresh 

 specimens, ranges from 2-695 to 2-785. 



A type-specimen (No. 1301) collected at the head of Starvation creek, has 

 been analyzed by Professor Dittrich, with result as follows : 



Analysis of Sheppard impure dolomite. 



Mol. 



SiO„ 24-61 -410 



ALA 6-84 -067 



Fe.,O s -58 -004 



Feb 2-01 -028 



MgO 13-34 -334 



CaO 19-14 -342 



Na 2 -62 -010 



ICO 2-07 -022 



ILO at 110°C -24 



JLO above 110°C 1-76 -098 



CO, 28-89 -656 



100-10 

 Sp.gr 2-779 



