GALLATIN VALLEY. 27 



It will be observed that the thicknesses given in the foregoing section to 

 the beds numbered 16 to 19 inclusive differ considerably from those of the 

 Crowfoot Ridge section. The correlation of the beds seems to be correct; 

 the error can not be large either in this or in the estimates of thicknesses, 

 as the white Quadrant sandstones above and the arenaceous Jefferson lime- 

 stones form a check on the work. This difference amounts to nearly 400 

 feet and is believed to occur in the upper beds of the Madison limestones. 



West of Quadrant Mountain and Bannock Peak the range consists of 

 a rugged region drained by the Gallatin River. This stream, which heads 

 in Gallatin Lake at the base of Three River Peak, flows through a valley 

 that is one of the most beautiful parts of the park. Broad open meadows, 

 diversified with clusters of pines and spruces, alternate with small patches 

 of forest that cover the broad valley bottom. To the south the slopes rise 

 steeply to the peaks of Crowfoot Ridge, while bold cliffs of white limestone 

 wall in the valley upon the north. The river flows rapidly, in a succession 

 of rapids and clear pebbly reaches, cutting the heavily bedded limestones 

 that form the valley floor. 



CROWFOOT RIDGE AND GALLATIN VALLEY. 



On the west side of the ridge along which the chief stratigraphic section 

 was studied a branch of Grayling Creek has cut a deep gulch, trending 

 toward the northwest. This follows the outcrop of the Flathead shales, 

 and has the gneiss and steeply dipping basal sandstone on the south side 

 and the massive Paleozoic limestones on the north. About a mile down the 

 gulch a fault crosses the country in a direction east of north, letting down 

 the block of sedimentary rocks and crystalline schists on the west side of 

 the fault, so that the strata dip at a more uniform inclination of 15° to 20°, 

 and also 30°, NE. This throws the basal quartzite at least 800 feet lower 

 down than the west end of the crest of Crowfoot Ridge, and brings the 

 Quadrant quartzite back to the summit of the west spur of Crowfoot Riclge, 

 from which it extends down its northern slope. 



At the western base of the end of this mountain ridge the sedimentary 

 rocks are lost sight of beneath a deep accumulation of glacial drift, which 

 obscures the contact between these rocks and the rhyolite lava that has 

 buried them and the underlying crystalline schists, as already pointed out. 

 The north and south ends of the fault just noticed are lost beneath the 

 same drift. 



