334 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



the north side canyon. For this mountain mass formed of a lower 

 group of northward facing cliffs and the ridges and peaks above, the 

 name Sedgwick is proposed in recognition of the great English geolo- 

 gist Adam Sedgwick, whose work on the early Paleozoic formations 

 of Wales gave the first clear separation of the Cambrian rocks from 

 the superjacent post-Cambrian formations. Sedgwick's great rival, 

 Murchison, is commemorated by Mount Murchison, and adjoining 

 that mountain we now have Mount Sedgwick. 



The measured stratigraphic section begins above at the summit 

 of the Upper Cambrian Sullivan formation, the massive upper lime- 

 stones of which constitute high cliffs above the cliffs of the subjacent 

 Cathedral (Middle Cambrian) limestone. The section terminates be- 

 low in the quartzitic sandstones of the Lower Cambrian St. Piran 

 formation, which are exposed on the north side of the Sififleur River 

 Valley opposite Siffleur Mountain. 



The Lyell, Mons, and Sarbach formations are present above the 

 Sullivan and beneath the Devonian limestones, but they were not 

 studied or measured, as the object of this section was to obtain data 

 to fill in the break between the base of the section at Glacier Lake 

 and the pre-Upper Cambrian formation beneath. The Glacier Lake 

 section terminates below with a thin-bedded, bluish-black limestone 

 referred to the Murchison formation of the Upper Cambrian, the 

 stratigraphic position of which in relation to the Middle Cambrian 

 was unknown, owing to the fact that debris covered all but the upper 

 portion of the formation. In the Siffieur section the Murchison 

 formation was found to be conformably above the Middle Cambrian 

 Cathedral limestone, and to occupy the position of the Stephen 

 formation of the Mount Bosworth and Mount Stephen sections. Only 

 fragments of fossils were found in it. It has a thickness of nearly 

 500 feet (152.4 m.) and is succeeded by the Arctomys formation. 

 The great Eldon formation, 2,728 feet (831.5 m.) thick, of the 

 Mount Bosworth and Mount Stephen sections, is not present between 

 the Murchison and the superjacent Arctomys formation. 



UPPER CAMBRIAN 

 Lyell Formation ^ 



This is represented by a cliff of limestone that rises to form 

 the highest points of the ridge above and south of the 

 Siffleur River. The limestone in view was estimated 

 to have a thickness of 400 feet (121. 9 m.). 



^ The cliffs above the Sullivan formation were difficult of access, and as 

 the purpose of making the section was accomplished below, an estimate was 

 made of the thickness of the lower division of the Lyell. 



