324 B. WILLIS — LEWIS AND LIVINGSTON RANGES, MONTANA 



The Siyeh limestone forms the mass of mount Siyeh, at the head of 

 Canyon creek, a tributary which enters Swift Current at Altyn from the 

 south. It constitutes the upper part of all the principal summits of 

 Lewis range north of mount Siyeh, including mounts Gould, Wilbur, 

 Merritt, and Cleveland. It extends beyond Watertpn lake westward into 

 the Livington range and forms the massive peaks between Waterton and 

 North Fork drainage lines. Above upper Kintla lake it is sculptured in 

 the splendid heights of Kintla peak and the Boundary mountains. 



An exceedingly characteristic and general feature of the Siyeh lime- 

 stone is the occurrence of an intrusive sheet of diorite, which is found 

 throughout the area examined, with an approximately uniform thick- 

 ness of 60 to 100 feet. The dikes by which this sheet was fed traversed 

 the formation, following the vertical joint planes with offsets. The con- 

 ditions of intrusion appear to have been extraordinarily uniform. The 

 rock is described in more detail in the accompanying note by Mr Finlay : 



The top of the Siyeh limestone, considered as a lithologic formation 

 over that part of the area where it was observed, coincides with an ex- 

 trusive igneous sheet, which was clearly erupted prior to the deposition 

 of the succeeding strata, and exhibits the ropy flow structures incident 

 to flow and cooling at the surface. The rock is of a rhyolitic nature. 



Sheppard quartzite. — A distinctly sandy phase of deposition succeeding 

 the extrusive rhyolitic eruption has resulted in a quartzite which is very 

 roughly estimated to have a thickness of 700 feet. It forms the crest 

 of Lewis range in the vicinity of mount Cleveland and Sheppard glacier 

 between Belly river and Flattop mountain. It has not been studied in 

 detail, but is recognized as a distinct division of the series. 



Kintla argillite. — The highest beds of the ancient sequence of strata 

 found in this part of the range are deep red argillaceous quartzites and 

 silicious shales, with marked white quartzites and occasional calcareous 

 beds. They are named the Kintla formation from their occurrence in 

 mountains on the 49th parallel, northeast of Upper Kintla lake. They 

 also form conspicuous peaks west of Little Kootna creek. The Kintla 

 formation closely resembles the Grinnell, and represents a recurrence of 

 conditions favorable to deposition of extremely muddy, ferruginous 

 sediment. The presence of casts of salt crystals is apparently significant 

 of aridity, as the red character is of subaerial oxidation. The formation 

 has an observed thickness of 800 feet, but no overlying rocks were found. 

 Its total thickness is not known, and the series remains incomplete. 



CA BB ONIFEB O US— YA KIN IK A K LIMES TONE 



It having been determined by the work of McConnell and Dawson to 

 the north and by that of Weed and Walcott to the south that the main 

 range of the Rockies carries a great thickness of Carboniferous lime- 



