Geological Survey Professional Paper 17 Preliminary Report on the Geology and Water Resources of Nebraska West of the One Hundred and Third Meridian

General features.—The region is a typical portion of the Great Plains, which extend far eastward from the foot of the Rocky Mountains. To the south this portion of the plains is traversed by the deep, broad valley of North Platte River and the smaller valleys of Niobrara River and Lodgepole Creek; to the north, at the Valleys of White River and Hat Creek, it gives place to lowlands extending to Cheyenne River at the southern foot of the Black Hills. The northern edge of the plains presented toward these lowlands is marked by a great escarpment, or line of steep slopes, which is known as Pine Ridge. It begins in Wyoming and is the most conspicuous topographic feature in northwestern Nebraska.

Pl. XI has for its base a topographic map of the region, with contour lines 100 feet apart. These contour lines indicate heights above the sea, and they are numbered accordingly. The lines for every even 500 feet are made heavier than the others. Contour lines are lines of equal elevation, consequently they are drawn along the slopes of valleys like level irrigation ditches, in this case 100 feet apart vertically, extending up the side valleys, and running out around the points of projections. They encircle detached hills, and an isolated hill rising 500 feet above the plain would be indicated by five of the 100-foot contour lines. From the foregoing statement, it will be seen that contour lines are crowded near together on steep slopes, but are widely separated on the plains and in the river bottoms. Thus, they indicate the shape of the land as well as its elevation.

For Banner, Scotts Bluff, and portions of Cheyenne and Sioux counties, the contour map is based on the detailed maps, with 20-foot contour lines, of the Scotts Bluff,a Camp Clarke,a and Whistle Creek quadrangles of the United States Geological Survey. In other portions of the region it has been necessary to employ barometer readings and local observations extending from points of known heights on the several railroad lines. These approximate data are distinguished on the map by broken contour lines.

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aTopographic maps of these two quadrangles have recently been issued by the Survey and may be obtained by remitting 10 cents (5 cents for each) to the Director, United States Geological Survey, Washington, D. C.

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Pl. II is a view of a relief map of Nebraska, which also shows the configuration of this area.

PLATE II.—RELIEF MAP OF NEBRASKA. (click on image for a PDF version)

High table.—The original surface of the region to which this report relates was a relatively smooth plain, which sloped gently to the east. This plain was uplifted in early Pleistocene time, and the rivers extending across it excavated valleys of greater or less width and depth, soon giving rise to the broader features of the present configuration. The remains of the plain lie between the valleys, where they constitute wide areas of high table-lands, smooth or very gently rolling in contour, and sloping to the east. The widest areas of this table lie on each side of the valley of Lodgepole Creek, and extend north from the Valley of North Platte River to the great escarpment of Pine Ridge, where there is an abrupt descent of over 1,000 feet to a region of low rolling plains which extend to Cheyenne River at the southern foot of the Black Hills. Some features of this great escarpment are shown in Pls. II, VIII, XVII, and XXI. The broad area of table terminating in Pine Ridge is traversed by the wide, shallow valley of the Niobrara, south of which it is surmounted by irregular zones of sand hills. The edge of the table descending to the valley of North Platte River presents steep slopes deeply notched by canyons. Next south, there is an outlying area of the high plain, preserved as a long; high, narrow ridge lying between the valleys of Pumpkinseed Creek and North Platte River. This ridge is so narrow and so deeply invaded by canyons that it has lost the flat-topped character, except in a few small areas in its widest portions. Its summits, however, in many cases rise to the plateau level. The ridge owes its isolation to a former channel of Horse Creek, which at one time flowed through the Pumpkinseed Valley. Eight miles south, across the valley of Pumpkinseed Creek, a branch of North Platte River, rises the steep face of the wide area of high table-land extending to the valley of Lodgepole Creek, and continuing beyond that valley far into Colorado. The altitudes on the table-land average about 4,300 feet along the one hundred and third meridian, and increase to nearly 5,000 feet in the vicinity of the Wyoming line. In the southwestern portion of Banner County, and again in the extreme southwestern portion of the State, the altitudes somewhat exceed 5,300 feet. Here is found the highest land in the State. Scotts Bluff has the reputation of being the highest point, but its altitude is only 4,662 feet. Wildcat Mountain, which has shared the claim as the highest point, is 5,038 feet, or fully 300 feet lower than the highest points on the high table along the Wyoming line.

North Platte Valley.—The region is traversed near its center by the broad valley of North Platte River, a stream which enters the State from Wyoming and carries the drainage of a wide area in the Rocky Mountains. This valley has been excavated from the plain which, as before stated, originally extended unbroken entirely across the western Nebraska region. The depth of the valley averages in the greater part about 700 feet, and its width varies from 10 to 15 miles. The slopes along its sides present many irregularities. There is first a broad flat along the river, which rises only a few feet above the water. This flat merges into irregular terraces, rising for about 200 feet, with slopes of varying degrees of steepness. Then come steep-sided projections of high lands extending from the edge of the high table above and separated by canyons which are cut into the margin of the table for some distance. These canyons have been excavated by small streams which flow into Platte River in times of heavier rainfall. The higher slopes of the valley are marked by cliffs and buttes of varied form and height, which often are very imposing in appearance. On the south side of the valley there rises an irregular ridge of striking prominence, cut off from the main high table to the south by the wide valley of Pumpkinseed Creek. The greater part of this ridge varies in width from 3 to 6 miles, with long projecting spurs and occasional outlying buttes. Its crest is relatively uniform in height, about 800 feet above the bottom of the Platte Valley. In the vicinity of the Wyoming line its altitude diminishes greatly, but it is practically isolated from the high tables southward. The main axis of the ridge is about 7 miles south of the river, but several spurs extend nearly to the river. One of these terminates in Chimney Rock, shown in Pl. XXIV; another at Castle Rock, shown in Pl. XXXII; and a third at Scotts Bluff, shown in Pl. III. To the east this ridge terminates in two outlying buttes, known as Courthouse and Jail rocks, shown in Pls. IV and V. It also sends a branch ridge out into the Pumpkinseed Valley, on which there are some particularly high knobs, one of which is known as Wildcat Mountain and the other as Hogback Mountain, in which an altitude of somewhat over 5,000 feet is attained. The western part of the ridge has an altitude of 4,860 feet. Scotts Bluff has an altitude of 4,662 feet and Courthouse Rock 4,100 feet. The ridge is deeply invaded by numerous canyons, which have cut away nearly all its original tabular surface. Toward its eastern extremity its lower slopes bear extensive accumulations of sand hills, notably in the region south of Camp Clarke.

PLATE III.—SCOTTS BLUFF, FROM NORTH SIDE OF NORTH PLATE RIVER. Dome Rock in the distance.

The Pumpkinseed Valley south of this ridge is elevated somewhat above the valley of North Platte River, into which it opens at Lapeer. It varies in width from 7 to 12 miles. It is characterized by gentle slopes, which extend north to the steep slopes and buttes of the ridge above described, and to the south to the cliffs and canyons at the edge of the high table. Lawrence Fork, the principal branch of Pumpkinseed Creek, occupies a valley which heads to the south and west on the surface of the table-lands.

Lodgepole Valley.—Lodgepole Creek has cut a narrow, steepsided trough in the plains to a depth averaging 300 feet. The valley contains a flat which has a declivity of about 17 feet to the mile, having an altitude of about 4,100 feet on the one hundred and third meridian and nearly 5,000 feet at the Wyoming line. Its average width varies from 1-1/2 to 3 miles. The principal branch is Sidney Draw, the two forks of which rise on the table-land in the vicinity of the Colorado line.

Niobrara Valley.—The Niobrara River flows in a wide, relatively shallow valley, high up on the table-lands lying between the valley of North Platte River and the crest of Pine Ridge. It enters Nebraska from Wyoming, flows southeast for 20 miles, and then nearly due east. At the Wyoming line its altitude is about 4,700 feet, and at the one hundred and third meridian about 3,900 feet, which indicates a gradient of 13 feet to the mile. The valley bottom is seldom over half a mile in width, with gentle slopes interrupted by occasional low cliffs. The bottom of the valley is only from 400 to 500 feet below the crest of Pine Ridge, and it is uniformly about 400 feet above the level of North Platte River along a north-northeast and south-southwest line, while to the north the lowlands beyond Pine Ridge are at altitudes about 600 feet lower than Niobrara River.

PLATE IV.—COURTHOUSE AND JAIL ROCKS, FROM THE SOUTH. Courthouse Rock irrigation canal in the foreground.

White River Valley.—White River rises in Pine Ridge, near Harrison, at an altitude of about 4,800 feet, or several hundred feet higher than Niobrara River, a short distance to the southwest. It flows to the east, and has excavated a gorge in the northern face of Pine Ridge, which has a fall of 1,100 feet in the first 20 miles, a declivity of 55 feet to the mile. Near Crawford the valley of White River merges into the rolling plains at the foot of Pine Ridge, and then extends northeast as a wide, shallow depression among rolling hills, in which its declivity is only 20 feet to the mile. Its altitude at the one hundred and third meridian is about 3,100 feet. The river receives many streams from the deep canyons in the northern front of Pine Ridge, and a number of intermittent creeks from the rolling country northward.

PLATE V.—JAIL ROCK, FROM THE WEST.

Hat Creek Basin.—Hat Creek is a branch of the South Fork of Cheyenne River. It rises in a canyon in the north front of Pine Ridge, in Sioux County, and receives numerous branches also heading in this front. To the east, where Pine Ridge trends southeast and passes around toward the head of White River, the divide between the Hat Creek and White River drainages is a low, narrow ridge, which projects from the spur of Pine Ridge near Adelia, and extends far to the northeast into South Dakota. The highest points on this divide beyond Round Top, the high spur of Pine Ridge, are some outlying mounds, of which the most conspicuous is the Sugar Loaf, due north of Adelia. Where the ridge is crossed by the Burlington and Missouri River Railroad, north-northwest of Adelia, the altitude is 3,816 feet. From the Sugar Loaf northeast the ridge is moderately high for some distance, and then gradually diminishes in height. It is crossed by the Deadwood line of the Fremont, Elkhorn and Missouri Valley Railway at an altitude of about 3,650 feet.

The upper portion of the Hat Creek Basin consists of deep canyons extending far into the north front of Pine Ridge. The sides of these canyons rapidly diminish in height to the north, and soon give place to a region of low rolling hills having a generally gentle slope northward. On the South Dakota line the altitude of Hat Creek is about 3,500 feet.

PLATE VI.—SMOKESTACK ROCK, FROM THE EAST. Showing outliers of conglomerate in Arikaree formation.

Sand hills.—There is in this portion of western Nebraska a narrow extension of the great sand-hill area of Nebraska. The hills are comprised in a series of detached groups that lie mainly in the northern portion of Cheyenne and the south-central portion of Sioux counties and cover an area of about 300 square miles. Their distribution is shown on the map, Pl. XI. The hills are mainly from 50 to 150 feet in height, and the areas consist of assemblages of irregular dunes with intervening basins and valleys. In T. 26, R. 55, and T. 27, R. 56, there are some exceptionally high sand hills, which rise somewhat over 5,000 feet in altitude, or from 200 to 250 feet above the surrounding plain. The lower dunes are in greater part covered with a scanty growth of grass, but there are many areas of considerable extent in which the sand is bare and loose. These localities are generally "blowouts" on the northwest slopes of the larger dunes. There is an extensive local sand-hill area along the south side of the valley of North Platte River, on the slopes south of Camp Clarke, which extends as far eastward as the vicinity of Courthouse Rock, The width of this belt is but 5 miles at most, and its length about 15 miles. An area of smaller size lies just west of Chimney Rock.

PLATE VII.—A (top), "TWIN SISTERS," BANNER COUNTY, NEBR. B (bottom), WIND EROSION IN GERING FORMATION, BANNER COUNTY, NEBR.

PLATE VIII.—NORTH FACE OF PINE RIDGE, LOOKING NORTHEAST OVER HAT CREEK BASIN. Showing cliffs of Arikaree formation. Badlands in Brule clay in the distance. (From photograph by E. H. Barbour, University of Nebraska.)