GALLATIN VALLEY. 29 



N. 10° W. The upper part of this drainage is located on the upper shale 

 belt in the Cambrian, but leaves it lower down the slope. The upper shale 

 belt may be traced across country by its influence on the topography, form- 

 ing saddles where it crosses spurs which trend north, and giving rise to 

 lateral drainage channels, feeding larger ones running north, or forming 

 basin-like depressions with sink holes, as already noted. 



The head of the gulch cut in the shale belt just mentioned is not shown 

 on the map, but it is quite strongly marked, being narrow and deep and trend- 

 ing north, and receiving the drainage of the small pond southeast of the larger 

 lake noted above. The west wall of this gulch is formed of the lowest 

 belt of Flathead limestone, with the lower micaceous shales of the Flathead 

 formation to the west. At the spot where the drainage from the small pond 

 falls into the deep gulch, these strata are inverted, dipping 60° or 70° W.; 

 strike, north and south. Hence the lower beds appear to overlie the upper 

 ones. The gneiss is only a short distance west. The inverted beds can be 

 traced northward into vertical beds, and then into others dipping toward 

 the northeast. To the south the inverted beds continue in the same position 

 until they abut against the gneiss. It is evident that there has been some 

 faulting and displacement of the basal formations for a short distance in the 

 neighborhood of the unconformity just mentioned. 



The portion of the high ridge east of the shale gulch and the ponds 

 previously mentioned is in general a syncline with a flat anticlinal fold at 

 its northern end, which is south of the saddle crossed by the fault to be 

 described. The dip of the strata, which are very steep near the gneiss, 

 changes from almost 45° NE. to 15° farther north, flattening to the syncline 

 already mentioned. The axis of the synclinal fold is somewhat west of 

 north, and the same fold may be observed to the southeast of this ridge. 

 Southeast of the southern end of the ridge a drainage channel follows the 

 line of the upper shale belt in a southeast direction. The southern side of 

 this drainage is formed of the lowest massive belt of limestone, and south of 

 this parallel gulches have been worn in the lower shale belts. These drain 

 either through cuts across the belt of massive limestone or in sink holes 

 beneath it. Here again the strata are inverted, with a dip of 50° to 80° 

 SW., changing in places to vertical and also to steep dips to the northeast. 

 Near where the gneiss ridge .is faulted by the north-south fault, the basal 

 beds of the sedimentary series are inverted, with dip of 20° to 50° SW., 



