MAE^^^-E.] GEOLOGY VICI^'ITY OF HOT SPRINGS. 165 



liill LVIII is abrupt, and sbows iu its upper portions the edges of the 

 sandstones, witli, at the base, some granite and gneiss beneath them, 

 and again, just west, but lying low in the stream, some of apparently 

 the same sandstones, but gently inclining west. In other words, a fault 

 passes at the west base of LVIII, in which the east side has been ele- 

 vated, and which is probably the equivalent of the anticlinal just south, 

 and the fault still farther south, near the Hot Spring road. 



The terraces mantle about the west and north base of LVIII, concealing 

 its sandstones in these directions, but the main ridge of sandstones rest- 

 ing on the gTanites continues on northward to the Grand Itiver. The 

 ridge is not prominent — the sandstones dipping steeper than farther 

 south, reaching 45° — while from it the nearly horizontal lake-beds, which 

 reach high upon it, sweep out between the Grand and Frazier Elvers in 

 many long, low terraces. The ridge of Cretaceous sandstones is lost be- 

 neath these lake-beds near the Grand, where the latter issues from its short 

 cailon through the granite mass below where theEastForkjoins the main 

 stream (?) of the map of the moraines of the Upper Grand. Thesandstone 

 ridge does not appear lying on this granite, the lake beds surrounding it 

 instead. At the north, and just without the ma^j on the right, are the 

 valley of the Upper Grand and the south end of the Medicine Bow 

 ridge. Xear Willow Creek and the Grand the lake-beds predominate 

 also. The north side of the Grand is lined pretty continually with two 

 low terraces of white lake-beds lying from a quarter to a half mile from 

 the stream, the country rising from them in long slopes, and rounded 

 hills lying between it and Willow Creek. A fine, dirty, dark, basaltic 

 lava lies at one or two points on the upper terrace, and appears also to 

 cap the hills, while much of the terraces are covered with lava fragments 

 and jaspery pebbles. The small patches of lava near the mouth of Wil- 

 low Creek occur but little above the stream, and seem to cap low sur- 

 faces, dijiping gently to the northeast. East of these the larger area 

 near the edge of the map is a mesa, or table-hill, capped with lava. (See 

 section.) 



Ascending Willow Creek, the beds of the valley are apparently of the 

 usual lake-beds. Where the dip of 5° east is indicated there occurs, 

 among light-gray sandstones, white marls, and other beds, a more indu- 

 rated bed of semi- compacted gravel, in the composition of which pebbles of 

 lava, often scoriaceous and up to four inches in diameter, enter largely, 

 as well as metamorphic rocks. While considerable false bedding occurs, 

 the general dip seems to be 5° or 10° to the east, a little north. 

 Just above, in some similar light-gray crumbling sandstones, a dip of 

 100-15° northeast was observed. While the hills seem lava-topped, 

 much basaltic lava here occurs iu the valley also. At first a tongue of 

 a dark, decomposing irregular lava touches the river from the north, 

 but above the river is lined more continuously on the north side with a 

 very irregular, red, brown, and black lava rock, bften having the appear- 

 ance of a consolidated mud. On the south, the rounded hills rise more 

 abruptly, but still seem lava-capped. A little farther up the lava occu- 

 pies both banks, and appears as if coming from an extensive flow on the 

 north and east, the eastern tongues of which cap ridges running out to- 

 ward Stillwater Creek. At the north rise hills adjacent to the ]\Iedi- 

 cine Bow ridge, which show somewhat in the section, but which will be 

 referred to later. 



We have seen that between the Frazier and Grand are the long, low 

 terraces, and that they also occupy most of the area drained by the 

 main tributary of the Lower Frazier, and that near the metamorphic 

 rock, at one or two points, they are composed of coarse debris, with 



