Geological Survey Bulletin 612 Guidebook of the Western United States: Part B

SHEET No. 22. (click on image for an enlargement in a new window)

Fernley (see sheet 22, p. 202) is one of the more recently developed agricultural settlements resulting from the Truckee-Carson reclamation project. The ditch from Truckee River runs along a hillside a considerable distance south of the railroad and from it water is supplied for irrigating some very promising bench lands. Good water for domestic use is found in wells 100 or 200 feet deep. From Fernley a recently finished line of the Southern Pacific, known as the Fernley-Lassen branch, extends north and northwest into California. Here also the traveler crosses the divide between two modern subdivisions of the former Lahontan basin, going from a basin tributary to Carson Sink into the valley of Truckee River, whence all natural drainage passes northward toward Pyramid and Winemucca lakes. As a part of the Truckee-Carson project, a part of the Truckee River water has been artificially diverted over the Fernley divide into the Carson and Humboldt basins.

Truckee River, named from the Indian guide of Gen. Frémont, flows through the old town of Wadsworth just beyond Fernley and 100 or more feet below the present railroad grade. The original route of the Central Pacific passed down into this valley, and Wadsworth was one of the important stations on it. Now, however, the railroad swings to the south to maintain an even grade on the westward climb along upper Truckee River.

Truckee River rises in Lake Tahoe and is of greater purity and subject to less fluctuation than any other stream that enters the Lahontan basin. At Wadsworth the Truckee makes a bend to the north and then flows through a narrow and canyon-like channel for 18 or 20 miles to Pyramid and Winnemucca lakes, where its waters are evaporated. Wadsworth was formerly a trading post and also served as an Indian agency and fort. Pyramid Lake is still included in an Indian reservation, the present Indian agency being situated at the south end of the lake near the mouth of Truckee River. The Indians are mostly of the Piute tribe. There are many references to Wadsworth in the history of the early events in this part of the country.

West of Wadsworth a backward view down to the narrow bottom lands along the river presents a pleasing contrast to the rocky barrenness of the hills on either side, at least during the summer, when a stream of clear water glitters amid green fields and trees. The train soon enters the Virginia Range and the canyon of the Truckee, which gradually narrows upstream. The rocks exposed in the canyon walls are mostly lavas, including volcanic flows and interbedded layers of volcanic tuff or ash, representing successive periods of volcanic activity. The lavas are of varied character, including light-gray rhyolite, darker andesite, and black basalt. At lower elevations along the bottom of the canyon are white, even-bedded clays, lying horizontal, which were left by the receding waters of Lake Lahontan. These clays rise to the maximum level reached by the former lake waters, about 4,400 feet above present sea level.

Between mileposts 273 and 272 the mining district of Olinghouse¹ may be seen, though it is at some distance across the canyon to the north or northwest. This district is now reached by way of Wadsworth.

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¹The White Horse or Olinghouse district lies on the east side of the Virginia Range and covers about 6 square miles. The prevailing country rock is andesitic lava. The district has yielded fine ore specimens and has shipped some good ore, but on the whole it has not been very productive.

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Opposite milepost 265 are the reservoir and diversion dam (Pl. XLII, p. 188) by which Truckee River water is taken into the ditch of the Truckee-Carson reclamation project. Unassorted and unconsolidated deposits of bowlders, gravel, and sand exposed in some of the railroad cuts are recent river deposits. The somber coloring of these barren rocky slopes is very characteristic of the Nevada desert ranges, particularly of the volcanic regions. Rock cuts along the railroad expose also some materials of brilliant hues, principally weathered volcanic tuffs belonging to the succession of lavas of which the Virginia Range is mainly composed.

PLATE XLII.—UNITED STATES RECLAMATION SERVICE DAM ON TRUCKEE RIVER IN THE VIRGINIA RANGE, BELOW RENO, NEV. Terraces of Lake Lahontan beds in foreground, a broad, low alluvial fan at the mouth of the gulch, and somber-looking hils covered with broken fragments of Tertiary lavas. Photograph furnished by Southern Pacific Co.

Gilpin (a sidetrack) is in the midst of almost continuous rock cuts and cliffs, mostly in basalt and basaltic tuffs. The channel here is so narrow that little or no cultivation is possible along the stream. At low elevations near the river channel the horizontal white lake beds are clearly exposed across the valley.

Derby was formerly the junction of the original route, which passed by way of Wadsworth, with the present line, but the old track down the south side of the river has now been taken up and the grade is used as a public road. West of Derby the canyon narrows and its walls become higher, consisting of continuous bluffs that show the lava flow rocks and interbedded layers of ash, including deposits of white tuff and diatomaceous earth, which appear as conspicuous white earthy bands at a number of places, both high and low, on the slopes. The successive flows of dark lava show here in the steep bluffs across the river, on the south side of the canyon.

The line between Storey and Washoe counties follows the channel of Truckee River, and county-line posts are seen at one end or the other of the bridges.

Clark is a minor station in the canyon and is the point of departure for the Ramsay mining district,¹ in the Virginia Range, to the south. West of Clark the Lake Lahontan clays are exhibited in cuts along the railroad. These extend to a siding named Ditho (elevation 4,304 feet), where the last remnants of such deposits are found, the track level at this point being almost exactly coincident with the uppermost level reached by the waters of the old lake. This is therefore the western limit of the former Lake Lahontan, whose basin the railroad has been continuously crossing from a point at exactly the same level in the Humboldt Valley near Golconda.

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¹Ramsay, a town of about 100 inhabitants, is 17 miles south-southeast of Clark station, with which it is connected by a good road traversed by a daily stage. The country rock is Tertiary lava (andesite and a little rhyolite). Several mines have shipped some gold ore, but the production has not been large.

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For several miles beyond Ditho remnants of a very recent though prehistoric lava flow may be seen in the river valley. The flow is a layer, apparently 10 to 20 feet thick, of dense black basalt, which lies chiefly along the very bottom of the valley. It is exposed in cross section at several places by the cutting of the river and along the old railroad grades, which lie slightly above the present route. This lava has flowed down since the valley attained practically its present form.

West of Hafed, a sidetrack opposite a ranch on the valley bottom, some good examples of columnar jointing in the basalt lava are exposed just above the railroad track. (See footnote, p. 121.) Volcanic tuff, both coarse and fine, apparently underlies the basalt and forms bluffs. To the west the river channel narrows again and is bordered on both sides by steep rocky ridges and spurs.

Vista, an old station and group of section houses, is at the upper end of the canyon in the Virginia Range, and immediately beyond it the Truckee Meadows spread out broad and flat. The extreme lower part of the meadows near the entrance to the canyon is marshy, from a cause explained in the footnote on page 189. The many prospects of the Wedekind mining district may be seen in the low foothills at the margin of the valley to the north. The district has never produced much ore.

The city of Sparks was named after John Sparks, governor of Nevada from 1903 to 1906. Although the second city in Nevada in population, it is primarily a railroad division point and contains the Southern Pacific Co.'s shops and roundhouses. A stop of 15 or 20 minutes is usually made at the railroad offices and shops, where a huge mountain-climbing locomotive is substituted for the ordinary one. After another stop at the passenger station, three-fourths of a mile farther on, the train proceeds westward 2-1/2 miles across the open valley to Reno.¹

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¹To the westbound traveler the view to the rear across the Truckee Meadows toward the narrow gorge by which Truckee River passes through the Virginia Range is suggestive of many events in the geologic history of this general region. The Virginia Range illustrates the block-fault structure that characterizes the ranges of the Great Basin. Its front stands like a great wall along the lower edge of the meadows, almost no foothills intervening between mountain and plain. The steeper part of the mountain front is trenched by gulches or canyons and is connected with the level plain at its foot by short slopes of talus and small alluvial fans. These worls of erosion and deposition, however, do not obscure the fact that the range is essentially an uplifted block of the earth's crust, and the valley below, now buried by river flood-plain deposits, is a relatively downthrown block. (See fig. 16.)

FIGURE 16.—Diagrammatic cross section showing the geologic structure of the Virginia Range in its relation to Truckee Meadows.

The mountains around the Truckee Meadows are broken by a narrow gorge through which Truckee River escapes. This gorge, now deep and narrow and worn into solid rock through the most of its course, has undoubtedly been cut by the river. It seems that such a channel may have been developed in one of two ways. Either Truckee River, dammed by the rise of a mountain ridge across its path, formed a lake and, after an outlet had been established by overflow at some low point on the margin, gradually wore this down into a canyon, or else the river, having established its channel across low-lying plains that existed before the mountains were uplifted, simply maintained its course by cutting down its channel as fast as the mountain barrier rose. That the latter hypothesis is the true one appears from the following considerations. If the site of the Truckee Meadows had ever been dammed to a considerable depth by uplift of the Virginia Range, the lake waters would have soon found an outlet through a low pass to the north, reaching Pyramid Lake by a more direct course than they now take. There is, however, no sign of such a channel nor of traces of shore lines about the valley to indicate that the lake ever rose to this height.

The uplift of the ranges in the Great Basin and of the Sierra Nevada, which is now near at hand, is a comparatively recent event as reckoned on the geologic time scale. (The term uplift is used only in a relative sense; it does not necessarily imply actual uplift. Some apparent uplifts may be due to a sinking of adjacent valley areas.) These mountain-building movements began late in the Tertiary period and have continued even down to the present day. Little by little blocks of the surface crust readjust themselves, and here and there earthquakes or the opening of fissures at the surface signify the gradual slipping of one fragment of the earth's crust against another. Probably the movements that uplifted the higher mountain ranges took place in the past in much the same gradual manner as to-day. The east front of the Sierra is now an earthquake zone, in which are felt occasional shocks and tremors due to movements in the earth's crust, and these appear to come periodically. They may be frequent for a period covering several months, which may be followed by a period of relative quiescence.

The Truckee Meadows may have been intermittently a shallow lake and a meadow. At present the river is flowing over volcanic bedrock at the entrance to the canyon, on the east, while the valley above is occupied by alluvium and possibly some lake beds. The ground water, following the general course of the stream, rises as it encounters the natural rock dam at the entrance to the canyon, making the lands above the canyon entrance marshy.

The mountains around the Truckee Meadows are composed of sedimentary rocks that are probably Mesozoic or possibly in part Paleozoic igneous, and metamorphic rocks, and lavas and associated sedimentary deposits of Tertiary or later age. The pre-Tertiary rocks were exposed for a long period to weathering and erosion before the Tertiary sediments were laid down upon them. In Tertiary time an extensive series of volcanic flows was poured out, accompanied by showers of volcanic ash and the accumulation of fresh-water lake or marsh deposits. These materials, with the deposits spread by running streams, form the later group of geologic formations here represented. The geologic column in the vicinity of Reno is very incomplete—that is, long periods of geologic time are unrepresented here in the record preserved by rock formations. Although some deposits may have been laid down during these periods and later entirely worn away, it may be inferred in general that the land surface in this vicinity was elevated and that by erosion its rocks were contributing to sedimentation in other parts of the region.

The lavas are principally andesites of varied mineralogic composition, but the series includes also much rhyolite and some basalt. All the lavas are inter-bedded with layers of volcanic ash, tuff, or tuff-breccia, the last consisting of angular lava fragments thrown out from the volcanic vents. Most of the lavas are Tertiary, but some are more recent.

The foregoing summary of volcanic activity applies especially to the eastern Sierra foothill belt, but it is broadly applicable to the whole western part of the Great Basin province. Moreover, the lavas here described are undoubtedly related directly to the extensive flows that spread out over the Sierra, although the later sedimentary record west of the Sierra divide is entirely distinct from that in the Great Basin.

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The largest city in Nevada is Reno, the seat of Washoe County, which has long been the principal commercial and industrial center of western Nevada. From this point the Virginia & Truckee Railroad runs south to Carson (31 miles), the State capital, and to Virginia City (52 miles), the locality of the famous Comstock lode, with the discovery of which Nevada's mining history began.¹ To the north the Nevada-California-Oregon Railway reaches Alturas (184 miles), in the northeast corner of California, and has lately been extended to Lakeview (238 miles), across the line in Oregon. Reno is the seat of the Nevada State University, which includes the Mackay School of Mines. Its manufactures include flour, foundry and machine-shop products, packed meats, and beer. Farming and stock raising are important industries in this vicinity, particularly in the Truckee Meadows and in the broad expanse of open valleys lying to the south, in the upper Carson Valley.

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¹Virginia City (Pl. XLIII) is in the Virginia Range near its crest, only 12 to 15 miles south of the canyon through which the railroad crosses these mountains. Ten years after the first gold excitement in California prospectors began to search the stream channels of Nevada. They found "pay dirt" along Carson River and traced these gravels far upstream. In January, 1859, prospectors followed these gold gravels to their source high on the slopes of Mount Davidson, and as washings from the loose surface croppings yielded rich returns, they dug down to bedrock. Then it was that the lode was discovered. A rush of prospectors followed, and Virginia City rapidly grew into one of the principal towns of the far West. In 1870 a narrow-gage branch railroad, 52 miles in length, was completed from Reno. This has been referred to as the most prosperous railroad in the country in its day, as it was said for a time to have regularly operated 40 trains a day over its 52 miles of crooked track. As the workings were deepened the ingress of hot water and the high underground temperature made mining difficult. The mines were in part drained by the Sutro tunnel, a notable engineering feat for that time. Work in the deeper levels is rendered possible only by the constant forcing of large volumes of air through the entries and a liberal use of ice water, both for drinking and for bathing, by the men, who work in very short shifts.

PLATE XLIII.—VIRGINIA CITY, NEV., ON THE FAMOUS COMSTOCK LODE. This lode is worked through deep shafts, one of which is under the building having four smokestakes, in the center of the picture. Photograph by Souhtern Pacific Co.

The Comstock lode is a great fissure vein, 4 miles long, along a line of faulting in the Tertiary eruptive rocks (chiefly andesite) of the Virginia Range. It crops out on the east side of Mount Davidson. The mountain range but not the summit may be seen in clear weather from Reno by looking up the open valley to the southeast. The ore, which is of high grade, carries silver and gold in quartz. In the old days it occurred typically in great bodies called "bonanzas." The district was noted for the large scale on which everything connected with the mining, including the speculation, was carried on. The size of the old dumps and the kind of machinery employed show even those who are used to mining that great things were done here. About $400,000,000 in gold and silver, in the ratio, by value, of 2 of gold to 3 of silver, has been taken out of the Comstock. Considerable ore is still being mined, but the great bonanzas have been worked out, and Virginia City is a melancholy wreck of what was once a lively town of some 20,000 people.

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Reno lies near the extreme western edge of Nevada and of the Great Basin, at the foot of the Sierra Nevada. Here Truckee River emerges from the foothills of the high mountains and flows out into the open Truckee Meadows. Now, as in the early pioneer days, Reno is a landmark in the journey across the continent. Here ends the long stretch of desert, and here the high timbered slopes of the Sierra Nevada, with their streams of fresh running water, appear near at hand. On the site of the present city a road house was erected in 1859 for the accommodation of travelers and freight teams on their way to and from California. By 1863 this place had become known as Lakes Crossing, and five years later it was chosen as a site for a station by the Central Pacific Railway. The name Reno was given to it at that time in honor of Gen. Jesse Lee Reno, a Federal officer of the Civil War. It became an important point of distribution for this part of Nevada, particularly for the adjacent towns and camps, which included the already famous Comstock.

Carson, the capital of Nevada, lies about 30 miles to the south and, like Reno, stands in a broad, fertile valley at the eastern base of the Carson Range, a front range of the main Sierra. This is the upper valley of Carson River, which, like the Truckee, flows eastward into the Great Basin.

About 10 miles south of Reno on the road to Carson is a group of hot springs known as Steamboat Springs. These and other hot-spring waters along the Sierra front have their origin in the heated depths of the earth, and come up along fault fissures generally parallel with the Sierra. The ground around Steamboat Springs has been built up by silica deposited by the hot waters, as a low ridge of white sinter, which is a conspicuous feature in the landscape. Many of the pools are actually at boiling temperature, and in cool weather clouds of steam rise from them.¹

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¹Steamboat Springs, Nev., has figured prominently in discussions of the origin of ore deposits. The waters of these springs contain the precious metals in minute quantities, and the sinter deposited by them contains several minerals that are common constituents of ores, as well as small quantities of many of the rarer metallic constituents of ore deposits, including gold and silver. Such springs, therefore, suggest that many and perhaps most ore-bearing veins have been formed by hot waters rising from great depths, which have brought their metal contents up in solution and deposited them in open spaces or fissures in the rocks through which the waters passed, the deposition of some ores being influenced by chemical reaction with the surrounding rock. Many ore deposits are undoubtedly formed in other ways, for some are unquestionably of sedimentary origin and the metal content of some others has been carried down, redeposited, and concentrated by rain water that descended into the earth's crust; but the "hydrothermal" origin—that is, their deposition from ascending hot water—of many of the more valuable ore deposits is indicated by the close relation observed at many places between mineral veins and eruptive rocks. Thermal waters are believed to be, in part at least, given off by slowly cooling and solidifying masses of igneous rock (magma) deep within the earth.

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Leaving Reno the railroad runs west along the north side of Truckee River, here again confined in a canyon, which, however, is not so narrow or steep as the canyon in the Virginia Range. The river is bordered on both sides by a succession of terraces, the uppermost of which is several hundred feet above the river bottom. In the outskirts of Reno, on the north side of the track, there is a clay pit and brick plant, and beyond them are large pits that have been excavated in the river terraces for sand and gravel to be used in construction work. The site of Reno and much of the valley to the west is overspread by deposits of bowlder and gravel left by the river during the period of terrace building. The open lands at the foot of the high mountains permitted the streams to spread out and deposit the load of bowlders and finer sediments that they had washed through the steeper and narrower parts of their channels above.

Projecting in places from beneath the nearly horizontal terrace deposits are regularly bedded, tilted sedimentary rocks, the only unaltered sediments of the Reno region known to be older than Quaternary. They belong to a series of fresh-water deposits called the Truckee formation, generally considered of Miocene age. These beds, which consist of clay, gravel, sand, and a peculiar white earth, are finely exhibited in conspicuous white bluffs 2 to 4 miles west of Reno, and are worthy of particular notice, for the chalk-white earth of which they are so largely composed here occurs in unusual quantity. This chalk-white material consists largely of microscopic shells, or frustules, as they are called, of one-celled plants known as diatoms,¹ once included under the general name Infusoria. These remains have collected here in numbers so immense as to form deposits hundreds of feet thick and in places make up almost the entire mass of the rock. This mass of fossil diatoms, or diatomaceous earth, formerly called infusorial earth, is white and looks like chalk but differs from chalk in that it is composed of silica instead of lime carbonate. It has also been called tripolite, from Tripoli, where a similar deposit is found. It is so light that it will almost float on water.

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¹Diatoms are of many different forms and inhabit both fresh and salt water. They consist of single isolated cells, or of strings of cells attached in linear succession or in zigzag chains. Those that compose the beds west of Reno are entirely of fresh-water origin. All diatoms secrete siliceous shells about their living parts, each shell consisting of two valves, which fit together like a pill box and its cover. Seen under the microscope they exhibit marvelous beauty and delicacy of structure. The myriads of such shells that accumulate after the death of these plants may form large deposits, although the individual shells are so minute as to be undiscernible by the unaided vision. Diatomaceous earth is used largely as a scouring or polishing powder, to which it is well adapted because of the hardness and sharpness of the individual grains and their uniform fineness. It also has uses dependent on its absorptive properties and has been so used in the manufacture of dynamite. As it is a poor conductor of heat and very light it is valuable as a packing for safes, steam pipes, and boilers, and for the manufacture of fire-proofing materials. No use seems to have been yet made of the deposits near Reno.

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Near Lawton's hot springs granite projects through the sediments, and the fresh rock is exposed in cuts along the railroad. The outcrop is characteristic of rock of this type, consisting of weather-rounded joint blocks that look like big bowlders but are really a part of the solid rock in place. Beyond the granite stream banks and railroad cuts reveal gravel, sand, and bowlder deposits, generally coarse and ill assorted but with nearly horizontal bedding. These are old river deposits, cut into by later deepening of the river channel.

At the bridges near milepost 234, by which the wagon road and railroad cross the river, and particularly at the wagon bridge over the railroad, is an interesting exposure of some of the tilted Tertiary strata. Here the beds consist of shale and sandstone and justify their usual designation as "lake beds" by their uniform thin bedding or lamination. They contain abundant and well-preserved impressions of leaves and grasses. These beds are believed to represent the Miocene epoch of Tertiary time. Beyond the bridge these sediments are again covered by terrace deposits.

Verdi is a lumber town whose history dates back to the days of the Comstock, before the coming of the railroad, when many of the timbers that went up to the mines were brought from this part of the mountains and hauled by way of Reno. West of Verdi, stretching north and south as far as the eye can see, is the steep front of the Sierra Nevada, this part of which is known as the Carson Range. The front is determined primarily by faults. (See explanation of formation of Wasatch Range, in footnote on p. 100.) The Truckee emerges from the mountain front after traversing a narrow canyon, steeper and more rocky than any part of its lower course. Scattered timber here clothes the mountain flanks, extending down even to the railroad and river although, of course, all the older and larger trees were long ago cut away. The green pines with their long needles and the growth of underbrush afford a welcome change from the monotonous barrenness, of the ranges and plains of the Great Basin. There is some cultivation in a small way along the narrow strip of river bottom lands.

On leaving Verdi the railroad turns southward up into the Truckee Canyon which soon becomes so narrow that there is not room for both railroad and wagon road, the latter diverging northward and crossing the range 10 miles or more farther north. The wagon road joins the railroad again at Truckee. The rocks in the canyon walls are Tertiary lavas, mainly andesites, and for some distance the supposedly Cretaceous granite, or a related rock, appears beneath these lavas along the river gorge. It is not always possible at a distance to distinguish between these two classes of rocks.

A few miles beyond Verdi the train passes a post marking the California-Nevada State line, and about half a mile beyond it is a sign-board and railroad siding marked Calvada, a name derived from those of the two States. This place is in a southward stretch of the canyon, so that the State line is crossed at a slight angle only a short distance west of the longitude of Verdi.