26 C. D. WALCOTT ALGONKIAN FORMATIONS OF MONTANA 



limited by Mr Bailey Willis, who, in the year 1901, carried out a reconnaissance 

 survey of the boundary belt on the Montana side.* No fossils have, as yet, 

 been found in these old rocks of the Purcell range, but fossils of so-called 

 Algonkian age were discovered in the Altyn limestone." 



In a letter received from Mr Eeginald A. Daly under date of Novem- 

 ber 3 he says of the work of the season of 1905 : 



"In general my section for the Livingston range is quite similar to that of 

 Mr Willis, though I seem to have a greater thickness of the Altyn represented — 

 a thickness deduced at a point where there is no suspicion of any considerable 

 duplication by thrusts. The same formations appear in the Galton range west 

 of the Flathead and yet show systematic contrasts in lithologic characters 

 when compared with the rocks of the Livingston range. These changes are at 

 first, as one goes westward from the Great plains, quite gradual, but they 

 quickly mount in value on the sixty-mile section across the Purcell range. In 

 brief they seem to depend, in the large way, upon distance from the old shore-, 

 line near the crest of the southern Selkirks not far from Priest River, Idaho. 

 The whole section made through these sediments is 150 miles long, i. e., 

 between Priest River and the Lewis thrust. The section is a cross-section, not 

 only with reference to the present mountain axes, but also of the geosynclinal 

 bearing the sediments. In the Selkirks at the Boundary the latter are coarse 

 and heterogeneous; in the Purcells, medium grained and homogeneous (sand- 

 stones, now quartzites) ; in the Galton and Livingston ranges, fine grained and 

 heterogeneous as described by Mr Willis. Thicknesses are very great at all the 

 best sections. I regret to report no fossils except in the Altyn, though I have 

 searched carefully for nearly three seasons. I am of the opinion, however, 

 that the Siyeh limestone is to be correlated with McConnell's Castle Mountain 

 limestone." 



The Creston and Kitchener quartzites appear to belong to the lower 

 portion of the Algonkian section, corresponding to the Prichard siliceous 

 series of the Idaho section, or it may be that the Creston is older than the 

 Prichard. In the diagram of sections I have made a tentative correlation 

 on the basis that all of the Northern Idaho section of Daly is older than 

 the Wallace and Blackfoot calcareous series. 



Source of Sediments 



The great development of limestone, accompanied by fine grained 

 sandstones and shales, in the Belt mountains, the Rocky Mountain front, 

 and westward to Idaho indicate offshore deposits. To the westward Dr 

 Reginald A. Daly found the strata west of the Kootenay, corresponding 

 to the Creston quartzite, formed of conglomerates, grits, and coarse sand- 

 stones, as well as fine grained sandstone. It is also to be noted that 



Bull. Geol. Soc. Am., vol. 13, 1902, p. 305. 



