Geological Survey Bulletin 707 Guidebook of the Western United States: Part E. The Denver & Rio Grande Western Route

From Montrose to Delta the railroad follows the valley of Uncompahgre River in a general course a little west of north. The country north of Montrose is more broken than that to the south, so that a general view of the valley can not be obtained from the railroad. Throughout most of the distance from Montrose to Delta the land near the river is well cultivated, but not far back from the river there is generally a line of bluffs on both sides of it, which range in height from 50 to 150 feet. These bluffs are but the fronts of extensive terraces, many of which are well cultivated, but the traveler can see only the barren shale underlying them.

For a short distance out of Montrose there is nothing to interfere with the view to the east, and the great Vernal Mesa, through which Gunnison River has cut its famous canyon, stands out in bold relief. For some distance the fault noted near Cimarron is still present, but apparently about halfway along the mesa the red sandstone beds of the Carboniferous and Triassic systems may be seen from the train as they lap onto the mesa in gentle curves. The mesa here is an arch—an anticline, as it is called by geologists—but the middle of the arch has been planed off by erosion, leaving the granite still at the surface. North of this point there is no fault on the west side of the mesa.

Along the railroad there is a high-tension electric transmission line, which brings electric power from Telluride, in the San Juan Mountains, for lighting Montrose, Delta, and other towns along the road. Olathe (o-lay'the), a place of recent growth, supplied by utilizing the water by the Gunnison tunnel is becoming a horticultural center. In passing along the railroad the traveler will note that the farmers of the valley are troubled in places with strong alkali, which makes the surface as white as if it had been covered by snow. This alkali, which is brought to the surface by flooding, due to overirrigation, makes farming difficult, but it can largely be removed by subsurface drainage.

One of the most promising parts of the valley for agriculture is the called California Mesa, which the traveler may see on the west (left) as he approaches Delta. This mesa is served with water by canals which divert it from Uncompahgre River at a place far up the valley. Delta is the county seat of Delta County and was so named because it stands on the delta formed where Uncompahgre River enters Gunnison River. The south slope of Grand Mesa, the tableland to the north, is one of the most noted fruit-growing regions of western Colorado. The orchards on this southward-facing slope are protected from frost in much the same manner as those at Palisade, so that fine crops of apples, peaches, and other fruit are produced here almost every year. The towns of Hotchkiss, Paonia, Cedaredge, and Austin are particularly noted for their excellent fruit, which is carried to Delta on a standard-gage branch road and thence shipped to other markets. Considerable coal is mined at Somerset, the terminus of this branch, and finds a ready market in the Uncompahgre Valley.

From Cimarron to Delta the railroad runs entirely on the Mancos shale, to which are due the breadth of the valley and the smoothness of its sides. At Delta the shale lies in a great structural trough—a syncline, as it is called by geologists—whose eastern edge rests on the flank of Vernal Mesa and whose western edge rests on the Uncompahgre Plateau. Below Delta the railroad changes its course from west of north to almost due west, and it therefore soon reaches the edge of this shale valley and enters a canyon cut in the underlying sandstone.

A short distance from the station at Delta the railroad crosses Uncompahgre River and then runs along the bank of Gunnison River, which the traveler has not seen since he left Black Canyon. Here the Grand Mesa is in full view to the north (right). All the lower slopes of this mesa are composed of the Mancos shale, which is so soft that it generally forms valleys wherever it is exposed, but the shale in the mesa is protected by overlying sandstone that is capped by a thick sheet of solidified lava (basalt). When this lava was poured out the present lowlands had not been cut, and the whole surface stood at the same level as that of the top of Grand Mesa. The volcano or volcanic vent from which this great flow was ejected has not been definitely located, but it may have been at a considerable distance, for this sheet is probably a part of the great lava flow that covered much of this general region, a flow whose remnants can still be seen on Grand Mesa and Battlement Mesa, to the north, on the Flattops, north of Glenwood Springs, and on other high mesas. If these remnants are not a part of a single flow they are probably parts of independent flows that occurred at about the same time. As the West Elk Mountains, east of Somerset, were a center of great volcanic activity at about this time the lava may have originated there. The striking thing about these lava flows is the enormous amount of erosion that has taken place since they occurred. The date of the flow can be fixed only as some time in the Tertiary period, but it was long enough ago to permit the removal from the valleys of rocks at least a mile in thickness.

The sandstone and interbedded shale immediately below the lava cap in Grand Mesa contain beds of coal and were formerly called the Laramie formation, which belongs at the top of the Upper Cretaceous series (see table, p. II), but now they are known to be older and to correspond with the heavy sandstones that form the Mesa Verde, in the southwestern part of the State, and hence they are called the Mesaverde formation. The same formation carries the coal at Anthracite and Crested Butte, northwest of Gunnison. At that place the coal beds contain coal of high rank, but in the Grand Mesa, which is farther from volcanic disturbances, the coal is of much lower rank, most of it being subbituminous, or what was formerly called "black lignite." A large mine is operated at Somerset, but in that part of the mesa which is visible from the river bank west of Delta coal is mined only for local use.

On the left, but not visible in many places, is the broad upward swell (anticline) known as the Uncompahgre Plateau, which is composed of sandstones that underlie the shale seen about Montrose and Delta. These sandstones will be seen in the canyon between Delta and Grand Junction. Around the margin of the plateau the massive red sandstones are deeply cut by the streams which flow from this upland in rugged canyons that have nearly vertical walls. These canyons are visible from the trains of the Denver & Rio Grande Western Railroad from Delta to the Utah State line. The interior of the plateau is unbroken and consists of a gently undulating upland without marked surface features.

Just after passing Roubideau siding, near milepost 378, the sandstone that underlies the shale makes its appearance. This sandstone, which contains thin beds of coal, has been called the Dakota sandstone, but the best authorities now place it in the bottom of the Mancos shale, and hence the Dakota may not be present. The rocks rise rather steeply in the direction in which the train is moving, and soon variegated shale and maroon sandstone may be seen. These rocks are in part the same as those which the traveler may have seen at many places along the Front Range and which contain the huge dinosaurs described on page 70. A skeleton of one of these dinosaurs was once found across the river from Grand Junction in rocks of the same kind.

At milepost 379 the railroad crosses the river, and from this place to Grand Junction the best views of the canyon may be obtained on the left. In the upper end of the canyon the walls are composed of variegated shale and sandstone of the Gunnison formation,⁵⁵ as shown in Plate LXXVI, B.

---

⁵⁵The Gunnison formation here is composed of three parts, as shown in figure 47. The upper part, which probably corresponds to the Morrison formation of the east side of the range, is visible where the walls are low. It is about 250 feet thick and is made up of variegated shale and soft sandstone. The colors are mostly maroon and green, and in many places the bands of color are very distinct. This part is comparatively soft and consequently forms slopes that lead down from the more resistant sandstone cliffs above. The middle part of the formation is about 100 feet thick and is composed largely of sandstone that is resistant to erosion and therefore stands out as buttresses on the canyon wall with steep or precipitous faces. Although not brightly colored, it has many of the same tints as the overlying shale. The lowest part of the formation is about 130 feet thick and is made up almost entirely of shale, which in the upper part is of a dull slate color but near the bottom has many bands of strong maroon. It is generally soft and forms slopes, but the slopes are steeper than those formed on the uppermost part of the formation.

FIGURE 47.—Rocks forming the canyon wall near Bridgeport.

---

PLATE LXXVI. A (top). CANYON BETWEEN DELTA AND GRAND JUNCTION. General view looking upstream. The rocks dip to the left, away from the Uncompahgre Plateau or arch. The shaly rocks in the top of the canyon walls are of maroon color, and the massive sandstone at the base is brick-red. Photograph by Willis T. Lee. B (middle). BRILLIANTLY COLORED SPUR OF THE CANYON WALL. One of the projecting spurs of the canyon wall near Bridgeport consisting of alternating bands of maroon and green with here and there bands of yellow sandstone. The valley bottom supports a fairly good growth of sage but when water is put on it grows almost any kind of crop. Photograph by Willis V. Lee. C (bottom). CROSS-BEDDED SANDSTONE. The sandstone was once a sand bank in water; the currents coming from the right washed layer after layer of the sand over the crest of the bank and down on its sloping front, making the cross-bedded layers. Photograph by J. K. Hillers.

At first the only part of the Gunnison formation that is seen is the upper shale, which gives to the canyon walls bands of rather strong color, but after watching these colors for several miles one would welcome any change from the ever-present maroon and green. Although the canyon is fairly narrow and there is not much land in it that can be irrigated, several attempts at irrigation on a small scale have been made. The method used employs no dams or ditches but only a current wheel, which is placed in the stream in such a position that the current turns it, and as it is provided with buckets, a small quantity of water is at each revolution lifted from the river to the top of the wheel, where it is automatically dumped into a trough that carries it to the land to be irrigated. Although this is a primitive arrangement it is excellently adapted to the irrigation of small tracts of land. A number of these wheels may be seen in the canyon.