PRELIMINARY REPORT OF THE FIELD-WORK OF THE UNITED STATES GEOLOGICAL AND GEO- UNDER THE DIRECTION OF PROF. F. V. HAYDEN, OFFICE OF THE UNITED STATES GEOLOGICAL AND Washington, D. C., December 1, 1877. SIR: I have the honor to submit the following preliminary report on the operations in the field of the Survey under my charge during the season of 1877. On the completion of the survey of Colorado last year, it was determined that the work of the United States Geological and Geographical Survey of the Territories under my direction should continue northward into Wyoming and Idaho. The belt of country including the Pacific Railroad having been explored and mapped in detail by the Survey of the Fortieth Parallel, under Clarence King, esq., it was deemed best to commence at the northern line of that work, and continue northward and westward, taking for the season of 1877 the country from Fort Steele, Wyoming Territory, to Ogden, Utah, or, more exactly, from longitude 1070 to 1120, and northward to the Yellowstone Park. The primary triangulation party, in charge of Mr. A. D. Wilson, Chief Topographer of the Survey, took the field from Rawlins Springs, Wyo. Near this point a base line was measured with great accuracy, from which a net-work of triangles was extended over the country to the north and west, locating, at intervals of from twenty to thirty miles, some prominent peaks, upon which stone monuments were built, in order that the topographers could recognize the points thus fixed for them. Upon these points was based the system of secondary triangulation. From the base at Rawlins, the work was carried northward to the Sweetwater Mountains, and thence to the Wind River Range. Upon some of the more prominent peaks of the latter range, such as Frémont's Peak, the stations were made with much difficulty, owing to the great masses of snow found there during the month of June, when the party was working. From this range the work was carried across the Green River Basin to the mountains on the west and north, where several stations were made. The work was resumed to the west as far as Fort Hall, Idaho, and thence south to the vicinity of Bear Lake, where another base, or base of verification, was measured; thence south as far as Ogden and Evanston, connecting with the triangulation of the Fortieth Parallel Survey at these points. From Evanston the party marched eastward, making some stations north of the railroad, thus bringing the work back to the point of beginning, Rawlins Springs, where the party was disbanded for the season. The system of triangulation employed during the past season was essentially the same as that carried over Colorado. The triangulation is all-important, as the topographical work depends entirely upon it, and the geologist can do but little without an accurate map. Thus the topographical as well as the geological maps are dependent upon a good system of primary triangulation. In addition to the primary-triangulation party already referred to, there were three fully equipped divisions for topographical and geolog. ical work, and another, under the direction of Dr. C. A. White, for critical palæontological work. The area assigned to the Green River division, under the direction of Mr. Henry Gannett, was rectangle No. 56, which is limited on the east and west by the meridians of 109° 30′ and 1120 and on the north and south by the parallels of 430 and 41° 45'. This is an area of about 11,000 square miles, lying in parts of Wyoming, Utah, and Idaho. The party took the field at Green River City, Wyo., on June 1. They first surveyed the drainage of Green River Basin. For this purpose they traveled up the Big Sandy, a large eastern branch of the Green, to the foot of the Wind River Mountains; thence crossing the head of the basin, fording the large and rapidly rising streams which make up the New Fork of the Green, they reached the main Green, and traveled down its western bank, going in to Granger, Wyo., on the Union Pacific Railroad, for supplies on June 23. The Green River Basin is a broad, flat, almost unbroken expanse, covered mainly with sage, among which considerable grass is scattered. Its greatest width in this district is about 50 miles, and its length reaches nearly a hundred. Its area within the district is not far from 3,000 square miles. The river-bottoms of the Green and its brauches, excepting the Big Sandy, are everywhere broad and beautiful, well covered with grasses, and shaded by magnificent groves of cottonwood. For agricultural purposes these bottom-lands are very valuable, while the limitless expanse of bunch-land would afford grazing to enormous herds of cattle. The Big Sandy is in low cañon through most of its course. Leaving Granger, the party next surveyed the broken, hilly country lying between the basin and the upper course of Bear River, north of Hariis's Fork. Following this belt northward, these hills develop into mountains of considerable importance about those large branches of the Snake known as John Day's and Salt Rivers. The party surveyed this belt northward to the north line, whence, turning westward, they mapped the basin of the Blackfoot and the valleys of the Portneuf; thence going in to Fort Hall, early in August, for further supplies of provisions. Taking up this section of the district in the order in which it was worked, it will be noted that the valley of Harris's Fork is fine agricultural land; that the hills about its head, separating it from the Bear, are rounded and grass-covered, affording a magnificent stock-range. As the hills increase in size and assume the dignity of mountains, the grass gives place to heavy pine and spruce timber of fine quality. John Day's River flows in a cañon valley, heavily timbered. The valley of Salt River is nearly ten miles in width and of the finest quality of land. West of this valley are high, broken hills, separating Salt River from the Black foot. The latter stream pursues a devious course in a great plain of basalt, diversified by buttes and extinct craters. Along the river are fine meadows, alternating with large swamps. The whole basin is covered with the best of grass. West of this basin the Blackfoot is separated from the Portneuf, here flowing south, by a range of low, grass-covered hills. The valley of the Upper Portneuf is at least eight miles broad, and is valuable for agriculture or grazing. West of it is a high range of mountains, through which, lower down, the Portneuf cuts its way into another broad valley, in which it flows to the north. This valley is floored with basalt, and is almost valueless. From Fort Hall the party proceeded to survey the country drained by the Bear and its tributaries, proceeding generally from the east westward. The country is a succession of parallel valleys, separated by ranges of bare, grass-covered hills or timbered mountains. The most eastern of these valleys is on the upper waters of the Bear. It is nearly ten miles wide, of good soil, and easily irrigated. The only drawback to agricultural pursuits is the elevation, 6,000 to 6,500 feet, which, in this latitude, indicates severe winters. Next westward is Bear Lake Valley. Here the cultivable area is at the head and foot of the lake, besides a narrow strip on its west border. Below the lake, the valley extends on to the northward for many miles down the Bear, and is very broad and fertile. The elevation of this valley is 5,500 to 6,000 feet. Further westward we encounter the Bear River Range, a broad belt of mountains reaching nearly to 10,000 feet in height, and heavily timbered. Beyond is Cache Valley, one of the finest areas of farming-land west of the Missouri. The elevation is 4,500 to 5,000 feet. grain, nearly all garden-vegetables and many fruits are raised in this valley. Besides A broken range of mountains separates this valley from that of the Malade. The latter has about the same elevation as Cache Valley, and is almost equally fine. Beyond it is a range of grass-covered hills, separating it from Blue Creek Valley. The valleys of the Bear are peopled mainly by Mormons; very few Gentiles indeed are to be found there. Mormon settlements, of greater or less extent, are to be found all along the Bear, from its mouth nearly to Randolph. Malade Valley is but sparsely settled as yet. Cache Valley contains several good-sized towns; the eastern part of the valley is quite closely settled. The valley of Bear Lake contains several good-sized towns, but above that settlements are scarce. The party left the field at Ogden, Utah, on September 30, having been in the field just four months. The area surveyed was between 12,000 and 13,000 square miles; 347 stations and locations were made; 53 of the stations, being important ones, were marked with stone monuments for future reference. The geological work of Dr. A. C. Peale in the Green River district connected directly with the eastern edge of the Sweetwater district. With the exception of a small area of granite along the southwestern side of the Wind River Mountains, and some basaltic flows in the northwestern portion of the district, the rocks are sedimentary, including the rocks from the Carboniferous to very late Tertiary age. The first month of the season was occupied mainly with the survey of the Green River Basin. Leaving Green River City, the river was followed to the mouth of the Big Sandy, a shallow, muddy stream, rising in the southwestern slopes of the Wind River Mountains. Both on Green River and the Big Sandy the prevailing formation is the Green River Tertiary group, consisting of clays, marls, and calcareous sandstones, forming bluffs on the rivers. These [strata continue uninterruptedly westward, inclining eastward from the hills west of Green River. Toward the southern part of the district remains of the Bridger clays are seen, forming buttes on the Green River beds. They are the outlines of the extensive Bridger areas that extend southward. On the southwest slopes of the Wind River Mountains there are abundant evidences of comparatively recent glacial action. The next area taken up was that lying between Green River and the Bear, with a strip along the northern edge of the district, reaching westward beyond Fort Hall. The mountains west of Green River are composed mainly of Carbonif erous limestones. Toward the north they form two beautiful ranges on John Day's River and Salt River, separated by a valley in which rocks of Jurassic and Cretaceous age outcrop. Between the mountains and the Green River Basin is a range of hills of Jurassic and Cretaceous age. On the east of these is the Wasatch group of Tertiary, resting unconformably on the Jurassic hills. Farther north the Wasatch beds cover the Jurassic and Lower Cretaceous strata, extending partly over the Laramie Cretaceous, with which it is unconformable. Carboniferous fossils were obtained from limestone bowlders in a conglomerate at the base of the Wasatch. These were derived, without doubt, from the Carboniferous mountains to the westward, which formed the shore-line of the ancient lakes in which these beds were deposited. An arm of this lake extended up Harris's Fork of Green River. The Green River and Wasatch beds here are horizontal, the former containing abundant remains of insects and fish. Good collections were obtained at several localities. The region of the Blackfoot River, in the northern portion of the district, is covered in the lowest portions with flows of basalt. These had their origin between the Blackfoot, Bear, and Portneuf Rivers. A number of the craters still remain. One of these, south of the Blackfoot, is very distinct, rising 200 feet above the general level. It is about 130 yards in diameter, and has a circular depression on the summit. The pouring out of this basalt must have occurred either during or immediately prior to our present period, as there has been little if any change in the surface since the eruption. The Blackfoot, Portneuf, and Bear all have the basalt in their valleys. Cu the Portneuf it extends almost to the Suake River plain, showing as a narrow belt. Its surface slopes, but not so much as the present bed of the stream. In some places the volcanic rock appears to have pushed the river to the western side of the valley. The lower valley of the Portneuf is interesting from the fact that it is the probable ancient outlet of the great lake that once filled the Salt Lake Basin. At the head of Marsh Creek, which occupies the valley, continuing directly south from that of the Lower Portneuf, is the lowest pass between the Great Basin and the drainage of the Columbia. In fact, so low and flat is it that a marsh directly connects the two streams, one flowing to the Bear and the other to the Portneuf and Snake Rivers. The bend of Bear River at Soda Springs is one of the most remarkable features of the whole district. Rising in the Uintah Mountains, Bear River flows northward for over two hundred miles, and at Soda Springs bends abruptly and flows southward toward Salt Lake. After it emerges from the gap west of Soda Springs, it flows out into a wide valley which opens directly into that of the Upper Portuenf. In this valley the divide between the two rivers is only a basalt plain, and in the eruption of this lava we may look for the clew to the extraordinary course of Bear River. North of the bend of Bear River the mountains consist of isolated masses of Jurassic and Carboniferous rocks, the general strike of the rocks being northwest and southeast. There are several interesting folds in the rocks of this region. The interesting springs at Soda Springs were carefully examined. The latter half of the season was devoted to Bear River, Bear Lake, and Cache and Malade Valleys. The Upper Bear River Valley has a wide drift-covered bottom. The hills on the east side soon develop into mountains as we go north. Formations from the Carboniferous up to the Wasatch Tertiary are represented, the latter resting on the upturned edges of the older rocks. On the west the same unconformability is seen, the area of Wasatch extending farther north. The beds consist of variegated sandstones and conglomerates. Bear Lake Valley has a range of low hills on the east, at the foot of which the lake leaves but a narrow margin. The waters of the lake occupy an area that is probably underlaid by several folds. The Bear River Mountains are composed of Silurian and Carboniferous rocks, limestones, and quartzites. The edges of the strata face the east, but as we go west we soon cross a synclinal fold, the western side of which rises into high peaks on the east side of Cache Valley. The base of the range facing Cache Valley is Silurian. It is abrupt, and the basset edges of the strata give it extreme ruggedness. In the cañous of the streams coming from the range, saw-mills have been erected, and now supply the flourishing towns of the valley. Numerous lime-kilns also furnish them with a good quality of lime, the limestone being derived from the adjacent rocks. There is but little doubt that the waters which once filled the Salt Lake Basin covered also the broad Cache Valley. The modern Tertiary deposits are found jutting against the mountains, and seem to pass gradually into the more recent deposits found in the central portion of the valley. The clays, sands, and marls of these modern beds are beautifully exposed along Bear River, which cuts its way across the northwestern part of the valley. On the west the mountains are broken or isolated ranges, which seem to have risen above the waters of the old lake as islands. The terraces are well marked on their sides, connecting with the Salt Lake Valley through the gap of Bear River. West of this gap, and extending northward, is the Malade Valley. It is broad and filled with modern lake deposits. Silurian rocks outcrop on the east and Carboniferous on the west. At the divide between the Malade and Marsh Creek is another of the old outlets of the ancient Salt Lake when its waters were at the highest level. Although the area surveyed was large, (13,000 square miles,) good collections of fossils were made and data obtained for the elucidation of many interesting problems in relation to the age of the mountains. The entire district is of great interest to the geologist. Coal-outcrops were noted at a number of places on the Upper Bear River and its tributaries, and on some of the branches of Green River. At one locality between Twin Creek, a branch of the Bear, and Harris's Fork, a tributary of Green River, there are some twenty-nine coal beds, separated by sandstones and clays, the aggregate thickness being 315 feet. The beds of coal are from 1 foot to 48 feet thick. This locality has been called the "Mammoth Vein." The area allotted for examination to the Sweetwater division, under the direction of Mr. G. B. Chittenden, covering atlas-sheet No. 57, is bounded on the east by the meridian 107°, and on the west by that of |
