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Show 206 north and south^ as will be seen by examination of the map. We will commence at the lower or north end of the cation, and follow up through the several continuous sections and note the principal points of interest. At c c, the Carboniferous limestones appear with their peculiar type of weathering. The. distant hills are underlaid by the granitic or meta-morphic rocks. The limestones seem to have dropped down so that a fault of some importance exists. These Oarbouiferons limestones rest on Silurian beds. In Section No. 2,' still farther up the canon, we find the Silurian arenaceous limestones forming a rugged escarpment at the base, while on the rather rounded hills the Carboniferous limestones crop out These hills rise about 1,000 feet above the bed of the river. We thus see that the metamorphic rocks, the Carboniferous and Silurian limestones, present three qnite distinct types or forms of erosion, thus giving considerable variety to the scenery. In Section No. 3, Plate V, the Siluriau beds overlaid with Carboniferous limestones continue and pass over the summits of the hills, while from beneath them rise up the reddish feldspathic quartzites, which have weathered into peculiar sharp pinnacles. The river runs for about three miles through a narrow gorge, with vertical walls on either side rising up a thousand feet or more, beset with these sharp angular pinnacles. Above this point, the surface features are softened down, the rocks partially covered with earth, but cropping out iu numerous places. On looking at the geological map of Montana, & c, prepared from the results of the Survey in 1872, it will be seen that there is a small stream . flowing into the West Gallatin on the west side, one branch of which rises in Lone Mountain, and the other branch in the Sphynx. Near the mouth of this stream, a high ridge of limestone crosses the Gallatin with a trend about northwest and southeast. On the east side of the Gallatin, the sharp ridges rise up to a height of 1,500 to 2,000 feet, with an inclination 50° southwest. Section No. 5, Plate VI, shows this ridge as it appears on the east side of the river, with the somewhat . rounded granitic hills below, on which the limestones lean. The river has cut its channel directly through this ridge, and on the bottom, the worn edges of the upturned shales may be traced across the channel with perfect distinctness. In the section we see the Carboniferous limestones at b underlaid with Silurian rocks, resting directly on the granites; and lying against the Carboniferous beds are the Jurassic at c e, and at d patches of Cretaceous, which seem to have dropped dowu, as* it were, iu a sort of Jurassic synclinal. The Silurian and Carboniferous, with a portion of the Jurassic group, appear to have been lifted up by a vertical force that broke the beds as if they were layers of lumber. In the depression which seems to have been produced by this movement, the Jurassic and Cretaceous beds are seen; but at a distance of about five miles, where, as shown in section No. 6, the Carboniferous limestones rise from beneath the Jurassic in a nearly horizontal position, it would appear that the elevation of the metamorphic rocks, pushing off, as it were, from the sides the sedimentary beds, produced a depression which formed an excellent reservoir for the drainage of the higher lands around, thus giving origin to a stream of water on both sides of the Gallatin. In the background in section 5, we see the group of volcauic peaks which form the divide between the Gallatin and the Yellowstone Rivers. In section 6, the rounded grassy character of the summits of the hills shows the more yielding nature of the Jurassic beds. It is not certain that the true red beds 1 occur in this immediate vicinity. In section 7, we find another dropping- j down or faulting of the strata. At b the Carboniferous limestones are | |
