428 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



At the south end of Fort Mountain the descending section beneath 

 the Cambrian conglomerate is as follows, as measured on the east 

 side of Corral Creek Canyon, 4 miles northeast of Laggan : 



CAMBRIAN CONGLOMERATE 

 Unconformity 



ALGONKIAN 



HECTOR FORMATION: 



Feet 



1. Dark-gray to black, finely arenaceous (siliceous) shale breaking 



down on weathered slopes, or sometimes forming low ragged 

 cliffs beneath conglomerate. Upper surface slightly eroded.. 520 



2. Greenish, finely arenaceous shale, with bands of reddish-colored 



shale. At no feet down a layer of fine interformational con- 

 glomerate occurs, with a finely arenaceous, greenish-colored 

 matrix that includes thin layers of pinkish, compact limestone 

 that weathers more rapidh^ than the matrix 120 



3. Purple-colored, finely arenaceous or siliceous shale 140 



4. Greenish-colored, finely arenaceous or siliceous shale 40 



5. Massive-bedded conglomerate. Matrix a coarse sandstone, with 



quartz pebbles and fragments of gray pinkish limestone 27 



This is evidently a deposit made from material brought down 

 by a river reaching back into the hills of that epoch. The 

 presence of the limestone is very important, as it indicates 

 limestones below any exposures of the pre-Cambrian rocks 

 of the Bow Valle}'. In places the matrix is coarse-grained 

 and in others a fine-grained sandstone. The limestone frag- 

 ments are small and those of sandstone usually larger, some 

 being 12 inches across. 



6. Reddish purple, arenaceous, siliceous shale, with greenish bands. 455 

 This shale is widely distributed and often folded and broken 



in exposures along the valley. 



CORRAL CREEK FORMATION: 



1. Coarse-grained, light-gray sandstone in massive layers, with 



some of the layers a fine quartz conglomerate. Estimated. . . 120 

 The outcrop of this bed is usually concealed by debris. 



2. Hard, quartzitic sandstones that break down on exposure to 



weather. Estimated 1,200+ 



An anticline and general disturbance of the strata at this point 

 breaks the downward continuity of the section. 



On the west side of Corral Creek Valley and south of the syn- 

 cline of Cambrian limestones and sandstones of Mount Richardson 

 and Ptarmigan Peak the strata of the Hector and Corral Creek 

 formations are displaced by thrusts and folds, so that the section is 

 broken and imperfect. The same is true of the pre-Cambrian forma- 

 tions south of the base of Fort Mountain. 



