| OCR Text |
Show 270 GEOLOGY OF THE HIGH PLATEAUS a broad valley parallel to the one just left. This has been named Moraine Valley, from a rather large and conspicuous relic of glacial times, which could not escape observation because it is so well preserved and tells its story so plainly. It fills a lateral valley, heading near the summit of Mount Terrill and extending eastward into the broader expanse of Moraine Valley. It is covered with pools and lakelets bowered with aspen and spruce, and has the ordinary terminal character where its proper bed opens into Moraine Valley; beyond which no traces of glaciation are recognizable. The altitude of the termination is very nearly 9,000 feet, showing the same general fact which has already been spoken of, that the glaciers did not, in this part of the country descend to low levels, but were confined to the highest parts of the region. In the northern part of Moraine Valley the sedimentary beds are occasionally revealed in insulated exposures surrounded by trachytic and ande-sitic beds in an advanced stage of decay. They are of Tertiary age and are found on the western side of the valley, where considerable spaces are uncovered. They dip slightly towards the east, being, in fact, the eastern branch of an anticlinal swell, while the beds of Summit Valley form the western branch and Mount Terrill occupies the summit. (See Sec. 3, Atlas Sheet No. 6.) Their Tertiary age is inferred from their position, but no fossils have been obtained from them. The volcanic rocks of the northern part of the valley seem to have been of much greater volume formerly than at present, and to have been much wasted by erosion, though it is also inferred that they were never so extensive and massive here as to the southward. They are all, so far as observed, trachytic; some of them belonging to the dark hornblendic division, others to the sanidin division, the latter predominating upon the western side of the valley. The principal drainage is to the southward, running parallel for a considerable distance to that from Summit Valley, and at length the two unite and form a noble stream as large as the Sevier, which has volume enough to reach the Colorado. The northern part of the valley is drained by a few rills, which find their way into Gunnison Valley to the northeast and thence through Salina Canon to the Sevier. Thus the divide between the |
