176 EDWARD STEIDTMANN 
Cambrian Flathead quartzite. This relation is expressed by angu- 
lar disconformity of bedding and by a basal conglomerate. The 
Belt formations of this area are correlated with those of the Walcott’s 
Belt Mountain section. The only difficulty in this correlation lies in 
the absence in the Philipsburg district of beds equivalent to the 
Greyson shale. The Beltian succession of the. Philipsburg district 
is as follows: 
Unconformity 
Spokane shales—Shale and sandstone, the prevailing in upper portion, color 
chiefly red, some cracks, and ripple marks, 5,000 feet 
Greyson shales—Apparently. lacking, may be included in Newland 
Newland limestone—Thin-bedded, more or less siliceous and ferruginous pass- 
ing into shale, generally buff on weathered surface. 
Shallow water markings in upper part, 4,000 feet 
Ravilli quartzite—Gray with some dark bluish and greenish shale, 2,000 feet 
Prichard shales—Dark bluish interbedded with sandstone, rusty brown ‘on 
weather surface, 5,000+ feet 
Neipart quartzite—Light colored. Base not exposed. 1,o0o0o+feet 
Finlay reports that the pre-Cambrian rocks of the Colorado 
Springs quadrangle consist chiefly of the Pikes Peak granite in 
which are minor inclusions of acid gneisses and schists. Two 
other granites and some pegmatite and syenite dikes are included 
in the pre-Cambrian. 
Haynes? finds the following pre-Cambrian rocks in the vicinity 
of Three Forks, Montana: 
Empire shale—Even-bedded green shales, interlayered with quartzite. Thick- 
ness, 800 feet, ( ?) 
Spokane formation—Well-stratified red and green slates interlayered with 
mud cracked and ripple-marked sandstone. Thick- 
ness, 1,650-+ feet. 
From studies of the Wardner district quartzite, Hershey* adds 
the Cataldo to the base of Calkins’ Belt section. 
1G. I. Finlay, ‘‘Description of the Colorado Springs Quadrangle, Colorado,” 
U.S. Geol. Surv., Folio 203 (1916), 17 pp., 7 pls., 9 figs. 
2W. P. Haynes, ‘‘The Lombard Overthrust and Related Geological Features,” 
Jour. Geol., Vol. XXIV (1916), pp. 269-90, 11 figs. 
30. H. Hershey, ‘‘The Belt and Pelona Series,” Am. Jour. Sci., 4th Ser., 
Vol. XXXIV (1912), pp. 263-73- 
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