p^^j^] GEOLOGY SECTION NO. 9. 219 



made these beds were entirely concealed. All the beds below Ko. 52 

 are probably to be referred to the Carboniferous and Permian systems, 

 although I cannot so refer them positively as there were no fossils found 

 to prove it. The red-beds (Triassic?) have a thickness of about 1,500 

 feet, which is about the same as we found east of the mountains. Cre- 

 taceous jSTo. 1 (Dakota group) is somewhat thinner, while the Jurassic (?) 

 between has about the same thickness as seen heretofore. The entire 

 thickness of the Cretaceous as shown here (beds 61 to 73 inclusive) is 

 over 2,000 feet. The beds have about the same characters as the analo- 

 gous beds east of the mountains. The illustration Fig. 1, Plate VI, car- 

 ries the section still farther to the eastward. Around the northern end 

 of the ridge "A" (trachyte) are, as indicated by the debris, Cretaceous 

 shales. No definite exposure was observed, and it was impossible to 

 tell whether or not the shales extended around to the eastern side, and 

 if they did, in what direction they inclined. On the east of the ridge is 

 a grass-covered valley (7i) about a mile in width, from which, going east- 

 ward, we ascend a low hill rising about 200 feet above the valley. On 

 the west side of this hill are outcrops of trachyte, seemingly stratified 

 and dipping toward the east. ; On reaching the summit we find that it 

 is plateau-like, cut into low hills by small gullies. Crossing toward the 

 eastward in one of these gullies, the following beds are exposed (the 

 point I in the illustration) from below upward : 



1. Volcanic breccia. 



2. Sandstone. 



3. Volcanic breccia. 



4. Breccia looking very sandy. 



The entire thickness is not more than 50 or 60 feet. The dip here, how- 

 ever, is not to the east, but west. The angle of inclination is only 20°. Be- 

 tween the points Tc and I is, therefore, a synclinal fold. The sandstone is a 

 dark greenish brown, very much metamorphosed ; some of the layers 

 look like a volcanic sandstone. The breccia seems to be inters tratified 

 in places, but is probably, in part, intruded, as in some places the sand- 

 stones on both sides are much changed. Still farther east, at the point 

 m, are similar beds, with the dip once more to the eastward. From this 

 point we descend into a broad valley, in which the beds are, for the most 

 part, covered up. Here are a few small lakes, with no outlet, and the 

 ground about them is covered with alkali. The valley is somewhat roll- 

 ing in character, not uniformly level, but having a gradual slope to the 

 east. It is underlaid by sandstones, and is a mile in width. On the 

 eastern side, on ascending a low ridge rising about 40 feet above the 

 valley, an outcrop of white shaly sandstones is seen, below which is vol- 

 canic breccia. The dip here is south 80° west; so the valley we have 

 just crossed {n) is another synclinal. The angle of dip is about 25° or 

 30°. There are three or four of these low ridges that are parallel to each 

 other ; the general strike being north 10° west. The first two, at o, in the 

 section, form an anticlinal. From m to n are exposures of light-gray 

 sandstones, somewhat fine grained, with interlaminated coarser sand- 

 stones of a dark-brownish color. The outcrops are not very decided. At 

 0, in a bed of rather coarse sandstone, I found fossil leaves, among which 

 Professor Lesquereus has recognized Rliamniis Poldiamis, Platanus Hay- 

 denii, and a fragment of a leaf of a Quercus new to this country, and 

 related to Quercus Eeerii, Al. Br. The flora, he says, is Lower Tertiary, 

 and represents the lignitic gToup. From o to p is a distance of about 

 an eighth of a mile. From the latter point we have a meadow-like val- 

 ley about a mile in width, from which we ascend granitic hills. This 

 valley is another synclinal axis. The hills are at B in the section, and 



