REPORT OF TEE CHIEF ASTRONOMER 163 



SESSIONAL PAPER No. 25a 



particular horizon-marker is evident. The mountains covering at least three 

 thousand square miles show, at frequent intervals, the outcrops of the lava- 

 No other horizon is more competent to demonstrate the stratigraphic equiva- 

 lence of the Lewis, Galton, and Purcell series in their respective upper por- 

 tions. 



The correlation of the three eastern series is further facilitated by the- 

 occurrence, in all three, of magnesian strata characterized by the peculiar 

 molar-tooth structure, which becomes prominent at a horizon about a thousand 

 feet or more below tbe Purcell Lava. This structure is dominant in the Siyeh 

 dolomite, a formation unmistakably recognized in the Galton series (with 

 about the same thickness as in the Lewis series) where the Siyeh forma- 

 tion was first described. The molar-tooth rock with all its typical features 

 also occurs in the eastern half of the Boundary belt crossing the Purcell 

 range. In that region the rock occurs in the form of relatively thin. 

 strata that interrupt the staple silicious sedimentaries of the Kitchener quartz- 

 ite. The recurrence of such a highly special structure and the fact that the 

 Kitchener quartzite and the Siyeh formation in the Galton and Lewis ranges 

 are capped by conformable and contemporaneous flows of the Purcell Lava, 

 are principal indications that the Siyeh formation must be correlated with the 

 upper part of the thick Kitchener formation. 



The equivalence of most of the members of the Lewis and Galton series 

 is otherwise very manifest in the field. The thin-bedded, silicious dolomite 

 of the upper Altyn on Oil creek is well matched in its leading lithological 

 characters as well as in stratigraphic position by the thin-bedded, dolomitic 

 quartzite and dolomite of the upper Altyn on Mt. Hefty and at other points 

 in the Galton range. The reddish-brown beds of the Hefty formation match 

 the lowermost, rusty beds of the Appekunny. The greater part of the Appek- 

 unny formation is almost identical in composition with the middle member of 

 the MacDonald formation. The 1,580 feet of Grinnell red argillites and sand- 

 stones correspond to the 1,200 feet of red argillites and sandstones in the Wig- 

 wam formation and the rusty-brown and reddish beds of the upper member of the 

 MacDonald. The homogeneous, dolomitic quartzite of the Sheppard formation 

 is, in part, paralleled by similar strata in the lowermost 125 feet of the Gateway 

 formation. The red argillites and sandstones of the Kintla match the red 

 sandstones and argillites of the Phillips. Abundant casts of salt-crystals, 

 sun-cracks and ripple-marks, showing special conditions of origin, are charac- 

 teristic of the Gateway, Phillips, and Kintla beds at many horizons in each 

 formation, and are also to be found in the red argillitic beds of the Sheppard 

 formation. In the Lewis and Clarke ranges at the Boundary, erosion has 

 destroyed the equivalent of the Roosville formation, if beds of that age were 

 ever laid down in the region east of the Flathead river. Half of the upper 

 Altyn beds, the whole of the middle and lower Altyn, and the Waterton argil- 

 lite are not represented in the Galton section, because neither upturning or 

 erosion has exposed these older rocks in the Galton range. 



25a— vol. ii— 11-1- 



