Smithsonian miscellaneous collections . t terrane, which at this locality does not show itstypical development, but consists largely of and grits com-posed of Archean debris. In the south end of this range, but a few milesdistant from the former exposures, the Belt terrane is entirely wanting, andthe Cambrian rests directly on the Archean schists, as it does at Neihart. The ^ Bull. Geol. Soc. America, Vol. 10, pp. 210-215. 286 SMITHSONIAN MISCELLANEOUS COLLECTIONS \OL. 64 character of the Belt beds indicates, moreover, that the Cambrian overlapsthe Belt (Period) shoreline. Fo
Smithsonian miscellaneous collections . t terrane, which at this locality does not show itstypical development, but consists largely of and grits com-posed of Archean debris. In the south end of this range, but a few milesdistant from the former exposures, the Belt terrane is entirely wanting, andthe Cambrian rests directly on the Archean schists, as it does at Neihart. The ^ Bull. Geol. Soc. America, Vol. 10, pp. 210-215. 286 SMITHSONIAN MISCELLANEOUS COLLECTIONS \OL. 64 character of the Belt beds indicates, moreover, that the Cambrian overlapsthe Belt (Period) shoreline. Forty miles southeast of Neihart, in the DeepCreek and Grayson Creek sections, on the southwestern slope of the Big BeltMountains, the Flathead rests on the Spokane shales, but at a higher horizonthan at the head of Sawmill Canyon. Twenty-two miles north-northeast ofDeep Creek in Whites Canyon, the full thickness of the Grayson shale andalso about 1,000 feet of the (Algonkian) Helena limestone occur beneath theCambrian sandstones. , rJ.,. LZI CAMB/f/y4 /VSANDSTONE HELfNAL/MESrO/ve Fig. 12. — Unconformity betweenHelena Limestone and Cambrian Flat-head Sandstone. The locality indicatedis miles southeast of the suburb ofLenox, and 2 miles southeast of the Capi-tol building at Helena. Montana. Crossing the valley of the Missouri River from Whites Canyon directlywestward 10 miles to the Spokane Hills, on the west side of the river, onefinds a syncline of Cambrian resting directly on the red Spokane westward on the same line to the city of Helena, a distance of 14miles, the Cambrian sandstones are found resting on shales 250 feet above CAMBRIANSAf^DSTONE HELENAUMESTONE ?.:l:v^:l ^••M^::?:^::-;l .:;:;i:;;v:i:- ?.•.ivv-I:.- ^vhi--t,-^ ^::L:.:::|:V::.V:: J>^ ^^i^O^V? ?-:\ ? X .? I ??^- ? \.-. :i-A =^L-E^^^h: 1 1 1 1 1 1 1 1 1 Jl 1 1 [ 1 1 1 1 i I \ 1 1 J Ill f 1 / 1 1 1 1 1 1 1 1 III 1 II 1 1 1 1 Fig. 13. — Unconformity betweenMarsh Shale and Ca
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