BUFFALO PLATEAU. 207 



while the southwestern slopes are largely covered by morainal drift. 

 Within the limits of the Park the gneiss forms the west side of the plateau 

 to within 100 feet of the top, where it is overlain by a horizontal bed of 

 indurated sandstone, which is undoubtedly the basal bed of the Flathead 

 formation. The rock is mottled with red and white streaks and layers, and 

 resembles the beds exposed on the southwestern flank of Bison Peak. 

 The exposure is 100 feet thick, 50 feet of which is vertical cliff. The top 

 of the plateau is generally covered with a growth of pine, but where the 

 sandstone prevails the surface is open and grassy and in strong contrast 

 to the gneissic areas. The summit of the plateau rises gradually to the 

 east to a high ridg-e, trending north. About 100 feet above the quartzite a 

 thinly bedded mottled limestone occurs, the rocks being horizontal. This 

 rock closely resembles the limestones found in the valley of Soda Butte 

 and Slough creeks. The high point (9,100 feet) on this plateau, which 

 lies just within the Park line, is formed of massive limestone that weathers 

 with a very rough surface and shows a few fossils which prove that the 

 beds belong to the Three Forks formation. Two hundred feet below 

 this summit a massive-bedded, coarsely mottled, dark-gray limestone 

 occurs, the strata forming the base of the Gallatin limestone and having' a 

 dip of 3° E. These two prominent beds of massive limestone are readily 

 recognizable horizons, which are as prominent in the Snowy Range, as 

 they are in the Gallatin Mountains. The extreme erosion of the old land 

 surface before the deposition of the volcanic breccias and the Cambrian 

 rocks is well illustrated in this area. Basic breccias rest upon the various 

 beds just noted and also upon the gneiss, and in the valleys and lower 

 slopes at the south end of Buffalo Plateau the volcanic rocks fill hollows in 

 the greatly eroded surface. 



LAMAR VALLEY. 



The valley of Lamar River, which appears to be one of the most ancient 

 drainage ways of the Park, is cut through a variety of rocks, most of which 

 are volcanic. The gneissic rocks are exposed on the south flanks of Speci- 

 men Ridge and are cut through by the river and by its tributary, Slough 

 Creek. On the west the gneiss forms rough and rugged slopes, but near 

 Crystal Creek the rounded bosses of the summit slope gently to the 

 southeast and pass beneath the adjacent rocks. On the south side of Lamar 



