Geological Survey Bulletin 611 Guidebook of the Western United States: Part A

SHEET No. 8. (click on image for an enlargement in a new window)

About half a mile east of the station at New Salem (see sheet 8, p. 60) the lignite mine of the Dakota Products Co. has been in operation for a number of years. The bed of lignite mined is 5 feet thick and lies about 30 feet below the surface.² West of New Salem, which is situated on the surface of the upland plain, the railway goes down a small ravine in which scattered granite bowlders can be seen from the car window for a distance of 5 miles, or as far as milepost 33. Beyond this point no bowlders can be seen, but careful examination of the surrounding upland has shown that they are present as far to the southwest as Almont.

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²The lignite bed is reached by a slope, and from the bottom of the slope the workings extend north about 2,100 feet. The lignite bed is almost horizontal. It ranges in thickness from 4-1/2 to 6 feet and is underlain by a bed of gray clay. Most of the lignite produced at this mine is either hauled by wagon to the surrounding country and used by the farmers or shipped by rail to the neighboring towns. North Dakota lignite represents one of the early stages in the transformation of vegetable matter into coal. The products of the various stages now recognized are (1) wood, (2) peat, (3) lignite, (4) subbituminous coal, (5) bituminous coal, (6) semibituminous coal, (7) semianthracite, and (8) anthracite. Much of the lignite is woody, and frequently logs and stumps are found in the mines. It is generally brown, and the woody parts will bend without breaking. The lignite of this State, as it comes from the mine, carries about 40 per cent of water. It will readily dry down to 8 or 10 per cent if stored in a dry place with good ventilation, but in so doing it shrinks and falls to pieces. This falling to pieces is generally called slacking (from its likeness to the slacking of lime, though lime slacks by taking up moisture and lignite by parting with it), and the process takes place rapidly where it is exposed to alternate moisture and dryness.

Manifestly a fuel containing 40 per cent of water can not be shipped any great distance, as the purchaser can not afford to pay transportation charges on so much water. The lignite is also difficult to handle on account of the slacking or breaking up, and when stored it is likely to ignite spontaneously by its rapid combination with the oxygen of the atmosphere or of water. Altogether it is far from an ideal fuel, though very useful for domestic purposes in this treeless country. Although lignite is a poor fuel for raising steam, it is well adapted to making producer gas that can be used economically in a gas engine for the production of power, and probably in the future it will be utilized largely in this way. The chief difficulty at present is that there is only a small demand in this thinly settled country for power, and hence there would be little market for the product, but it is possible that with the growing use of long-distance transmission lines the lignite could be utilized for the production of electric power at the mine and the current carried to distant towns and cities or even to ranches for utilization. Lignite has been found to be an excellent fuel for burning brick and is now used extensively at Dickinson and other towns in the State for that purpose.

Lignite occurs most abundantly in the Fort Union formation (the lowest formation in the Eocene series of the Tertiary system), which underlies almost all the western part of North Dakota. It is estimated that the State contains the enormous amount of 697,900,000,000 short tons of lignite in beds over 3 feet thick and within 1,000 feet of the surface, and it seems probable that there is workable lignite within this limit under every section of the land in the western part of the State. It is difficult to form an idea of a mass containing even 1,000,000 tons, and hence the figures given above are practically impossible of comprehension, but if the amount is put in the form of a cube a better conception of its magnitude may be obtained. The lignite of the State, if gathered into one mass in the compact form in which it lies in the ground, would make a cube 5 miles long, 5 miles broad, and 5 miles high. Such a cube would cover nearly a township of land and would be almost as high as the highest mountain on the globe.

The lignite, although of poor quality and at present used only in a small way, constitutes a vast fuel resource which will in time become of great value, not only to the individual citizens of the State but to the corporations that are seeking power for use in manufacturing or in transportation.

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Some 10 years ago several lignite mines were in operation at Sims, but now all but one of these are closed and abandoned. The bed of lignite mined here is 7 or 8 feet thick, and in drilling a deep well for water four other beds having thicknesses of about 5 feet each were found. According to the log of this well there is 29 feet of lignite below the surface at Sims in beds thick enough to work, and the lowest is at a depth of 710 feet.

Below Sims the railway follows the small valley of Hailstorm Creek and affords no general view of the country. Just east of Almont the valley of Hailstorm Creek joins that of Muddy Creek, which the railway, making a sharp turn to the right, ascends practically to its head. This valley shows excellent examples of stream meanders, the creek making great loops whose ends in places nearly connect.

About 11 miles from Almont, at milepost 51, there are on the right (north) about a mile distant many knobs and spurs having a bright-red color. When examined closely the color is seen to run in more or less regular horizontal bands, like the rock, but it is not continuous, and in places it affects the whole hillside. This color is due to the burning of beds of lignite, which has baked and reddened the originally dark strata on either side, as clays originally brown or gray in color turn red when burned into brick.¹

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¹All through the lignite region and the fields of low-grade coal of the Rocky Mountains and Great Plains the coal beds have burned extensively along their outcrops, the resulting red color giving a touch of brightness to some otherwise dull and monotonous landscapes. In some places the burning has been just sufficient to color the shale and sandstone to a bright red, but in others, where the lignite bed is thicker or where more than one bed has burned, the heat has been so intense that the rocks have been melted into a sort of slag or scoria, good examples of which will be seen farther west. When a thick bed of coal or lignite burns, the overlying material settles, and frequently great cracks are formed, out of which issue smoke and steam from the burning lignite below. An example of such cracking is shown in Plate IV, B (p. 52).

As the lignite retains much of its original woody character it ignites readily when dry, and the fires may have begun in any one of several ways. For instance, they may have been started by prairie fires, by lightning, by camp fires, or even by alternate wetting and drying, which causes very rapid oxidation and a consequent rise in temperature. The last suggestion may appear improbable, but the writer has seen a large pile of low-grade coal take fire after a rain and be entirely consumed. The burning of a dump of waste material is a common experience at many mines, and rarely is the fire started by man. Once started, the burning of a coal bed will continue as long as air is available. Near the outcrop the coal burns readily, but back under cover the amount of air is not sufficient for combustion and the fire dies out. Many coal and lignite beds are burning to-day, and it is possible that one may be seen in the badlands called Pyramid Park, farther west, near Sully Springs, N. Dak.

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PLATE IV.—A (top), BADLANDS IN THE VICINITY OF MANDAN, N. DAK. These are not so rugged or picturesque as those to be seen further west, where the precipitation is less. B (bottom,) CRACKS PRODUCED BY THE BURNING OF A BED OF LIGNITE. Where a bed of lignite many feet thick burns, the sandstone or shale overlying it breaks down, forming large cracks through which steam and smoke issue as long as the lignite is on fire.

The success of dry farming has led to the settlement of almost all of western North Dakota, and towns have sprung up along the railroads like magic. Glenullen is one of the newer towns, and from its general appearance it is evident that in this region dry farming is a success. Although grassy slopes or fields of grain predominate in this part of the State, the appearance at intervals of bare knobs or buttes indicates that everywhere under the surface are the same lignite-bearing rocks that were seen farther east, those of the Fort Union formation. These rocks, when searched carefully, are found to contain many impressions of fossil leaves which show that the sands and muds, now hardened to rock, were laid down in shallow water near a land surface upon which trees and smaller plants grew in abundance. Where the land was swampy the vegetation was covered as it fell and in time was changed into lignite. In this part of the country the lignite is generally concealed by the grassy slopes, but farther west many beds are exposed in the hillsides. The fossil plants of the Fort Union formation indicate very different conditions during the Eocene epoch from those which prevail to-day. A brief sketch of the flora, together with an interpretation of its meaning, is given below by F. H. Knowlton.¹

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¹As the traveler rides mile after mile over the almost barren plains of Dakota and eastern Montana and sees them shimmering in the heat of midsummer, with only an occasional cottonwood or box elder along the streams or sprawling, stunted junipers on the rocky slopes to relieve the monotony, he finds it difficult indeed to realize that this country once supported a vegetation as luxuriant and varied as that now growing in any of the Southern States. However, it will require only a brief examination of the rocks to convince him of the truth of this statement, as they contain in many places the remains of vast numbers of branches, leaves, fruits, and even a flower here and there. Fossil remains have aptly been called the illustrations in the world's history, of which the pages are the layers of rock forming the outer part of the crust of the earth. It is the purpose now to look at a few of these illustrations and by this means restore in imagination the ancient vegetation.

Fossil plants are very abundant in the Fort Union formation and are found in the sandstone, in the harder concretions or lenses, and in the clay between the sandstone beds. Most of them, especially those in clay, are preserved with remarkable fidelity. About 300 species have been described, and it is probable that the total number may be found to reach 500 or more species.

Beginning with the plants of the most simple structure, we may first consider the ferns. One of the most abundant and widespread forms, having been found at hundreds of localities, is the beautiful sensitive fern Onoclea. This can not be distinguished from the living species, which now grows so widely over eastern North America. There is also a chain fern (Woodwardia) very closely resembling a living species, and numbers of others that are more or less closely related to forms now growing in the Eastern States.

The conifers, though not numerous in species, were very abundant and were of the types that must have been of rather imposing appearance. The most abundant form is a redwood (Sequoia) that is very closely related to the redwood which is now confined to the coast regions of California. There was also another Sequoia nearly related to the big trees of California, but it was not so abundant as the other form. With these was a cypress (Taxodium) that must have been much more beautiful than the common cypress of our southern swamps. There was also a cedar (Thuya), with delicate juniper-like foliage, that must have been very numerous, as its fossil remains are widespread in the Fort Union formation. In strange contrast to these conifers is what appears to have been the immediate ancestor of the celebrated ginkgo, or maiden-hair tree of China and Japan. The ginkgo has had in many ways a more wonderful geologic history than any other tree now living, as it has come down to us practically unchanged from earliest Mesozoic time. It apparently saw its heyday during what is known as the Jurassic period (see table on p. 2), when it was widely spread from the Arctic regions over most of the globe, but since that time it has been gradually dwindling until it is now represented by a single living species in Japan and China. It is regarded as a sacred tree in the Far East and as such is planted about the temples and sanctuaries, but there is great doubt as to its existence in a truly wild state. It is not likely to become extinct, however, for its fascinating history and curious fernlike foliage (see fig. 6) have made it of so great interest that it has been extensively planted in many parts of the world, notably southern Europe and eastern United States. It is a familiar shade tree on the streets of Washington, D, C.

FIGURE 6.—Ginkgo leaf.

Among the so-called higher flowering plants there were many grass and sedge-like plants during Fort Union time, but none that were very conspicuous or otherwise remarkable. Other monocotyledonous plants included a fan palm with leaves that must have been 5 or 6 feet across, which once grew along the lower reaches of Yellowstone River in Montana, as shown on Plate XI, B (p. 75).

The plants with deciduous leaves (dicotyledons) flourished in great numbers in Fort Union time, as they do now. They included trees of many kinds, shrubs, vines, and probably herbs of more humble growth. Among the trees one of the most abundant types as regards kinds as well as individuals was the poplar (Populus). These were of an ancient type, with small rounded or heart-shaped leaves, and were most closely related to the living quaking aspen. Of the willow several species are known. Oaks of several kinds were present, as well as two species of hazelnut, both of which are still living in the eastern United States and Canada. Walnut, allied to our common black walnut, was present, together with sycamores so like the living species as to be separated with difficulty. Figs were present, though not so numerous in North Dakota as they were in other areas where the same formation prevails, notably in Colorado. There were also elms, maples, birches, alders, dogwoods, hickories, box elders, buckthorns, viburnums, wax berries, witch-hazels, horse-chestnuts, bittersweets, and many that are without common names.

From this abundant flora it is evident that what is now an almost treeless plain was then covered with splendid forests of hardwoods, interspersed with scattered conifers and ginkgos. From the presence of numerous and in many places thick beds of lignite it is clear that there were great swamps, and that these must have continued with but little change for long periods of time. It has been estimated that the product of heavily timbered woodland, when compressed to the specific gravity of coal, would only amount to about one-fourth of an inch in thickness during a century. If this statement is even approximately correct, it is easy to calculate that a 4-foot bed of coal must have required about 20,000 years for its accumulation.

Except for the presence of palms and an occasional fig, it might be presumed that the climate was not greatly different from that now prevailing on the Atlantic slope of North America—that is, cool temperate. The palms which are found in the lower part of the formation imply, so far as the present distribution of palms indicates, a somewhat warmer climate, just as the numerous thick beds of lignite throughout the formation imply long-continued marsh conditions.

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The railway gradually ascends the valley of Muddy Creek, and if the traveler is not looking carefully he will cross the divide and enter the valley of Knife River without being aware that he has passed out of the valley in which he has been traveling from Almont. As a matter of fact the two valleys are continuous, and it seems probable that originally the drainage from the vicinity of the summit at Antelope came into Muddy Creek, but that some change has occurred by which the drainage about Hebron has been turned northward into Knife River. The details of this change have not been worked out, but it was doubtless caused by glaciers which crossed Missouri River and extended to the southwest as far as this valley, damming the streams and compelling them to find new outlets.

Hebron, one of the new towns of western North Dakota, is the center of a prosperous agricultural district and is noted for the manufacture of fire and pressed brick, the clay for which is derived from the Fort Union formation. The bed of clay utilized is at least 50 feet thick. Beyond Hebron the railway follows the broad, open valley of Knife River to its head, where there is a steep climb to the summit of the dividing ridge between that stream and Heart River on the southwest. The highest point is reached a short distance beyond Antelope, where a good view can be obtained of the upland surface of this part of North Dakota. The surface is gently undulating, but here and there on the principal divides there is a high knob that has not been reduced by erosion to the general level. The sides of these knobs are generally bare, and they have been sculptured by the rain, the frost, and the wind into most beautiful and intricate forms. (See Pl. V, p. 53.)

PLATE V.—A (top), B (bottom), EROSION FORMS OF NORTH DAKOTA. As soon as the turf is removed from the sides of the ridges and hills the slopes are cut rapidly by the rain. Each little trickle of water cuts a hole vertically through the sand or clay, producing a surface which, when seen from above, resembles a gigantic sponge. Its general appearance is shown in the upper view. When erosion has reached a more advanced stage. The hill may be reduced to an isolated butte, as shown in the lower view, and the sides are covered with the most delicate tracery.

West of the summit the surface descends to Richardton, the largest town between Mandan and Dickinson. This town has grown up as a result of the success of dry farming. It is attractively situated on the rolling upland plateau of western North Dakota and has abundant supplies of clay and lignite ready to be utilized in the building of a large town.

From Richardton the railway winds through a gently rolling country and gradually descends to Heart River, which is reached at the village of Gladstone. Here the railway is in the same valley that it left a few miles west of Mandan, but the climb out of the valley and the descent back in again saved the railway several miles of track, although it involves some rather heavy grades.

The valley of Heart River is comparatively narrow and is bounded by steep bluffs in which the rocks of the Fort Union formation are well exposed. At the little village of Lehigh (see Lehigh. sheet 9, p. 64) a lignite mine has been in operation for a number of years. The bed of lignite, which is from 6 to 7 feet thick, lies horizontal and is reached by an entry driven into the hillside. The workings extend 2,000 feet or more into the hill, and the lignite is brought to the tipple in cars hauled by horses.¹

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¹The lignite as it comes from the mine contains about 42 per cent of moisture, but on drying parts with most of it, the percentage being reduced to about 10. The composition of an average sample of this lignite after it had been dried at a temperature of 86° to 95° F. until the sample attained a constant weight is as follows: Moisture, 9.1 per cent; volatile matter, 38.2 per cent; fixed carbon, 42.1 per cent; ash, 10.6 per cent. Its heating value is 9,640 British thermal units. A British thermal unit is the amount of heat required to raise 1 pound of water 1° F., or it may be considered as the ratio of weight of coal burned to the weight of water that will be raised 1° by the burning of the coal. Thus the burning of 1 pound of air-dried Lehigh lignite would raise the temperature of 9,640 pounds of water 1°. Coals range in their heating value from the amount given in this analysis, which is about the lowest, to as much as 15,500 British thermal units, a value shown by the best Pocahontas and New River coals of West Virginia.

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