Geological Survey Bulletin 613 Guidebook of the Western United States: Part C. The Santa Fe Route

From Goffs the railway runs nearly due southwest for many miles (see sheet 22, p. 158), descending continuously into one of the great interior basins that are characteristic of a large part of southeastern California. The slope is covered with a thick mantle of gravel and sand, constituting a typical desert plain from which detached mountain ranges rise abruptly at intervals. These ranges have steep sides, are deeply recessed by canyons, and have remarkably ragged or pinnacled summits. The plain slopes up toward the mountain and is built of the products of their disintegration. The deposits are thick, for they have been accumulating for a long time and every rain causes a local flood that carries the rock waste farther and farther down the slopes and at the same time adds a new supply from the mountain sides.

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

There are many instructive illustrations of the relations of these desert plains from Needles all the way across southern California, but some of the most impressive ones are in the region southwest of Goffs. Rain is infrequent in this region, as the average total precipitation is considerably less than 6 inches a year. However, much of the rain falls in remarkably heavy showers, or cloudbursts, which quickly flood the drainageways with a swiftly flowing body of water sufficiently powerful to roll large bowlders and to transport a vast amount of fine material far down the slope. These floods are exceedingly troublesome to the railway company, which must make long deflection ditches and dikes to prevent serious washouts. Work of this sort along the Santa Fe lines in the desert region has been as large an item of expense as flood protection and repair in regions where there are large rivers subject to freshets. The run-off is very rapid m the deserts, because the rocks are bare, the soil is hard, and most of the slopes are steep. Very little water passes underground, and springs, even in the mountains, are exceedingly rare. Much water, however, is lost by evaporation.

Fenner is on a desert plain or flat-bottomed valley of considerable width. (See Pl. XXXIX, p. 150.) A few miles to the east rises the high mountain range which begins at Goffs and extends far to the south. Its higher part, southeast of Danby, is known as Old Woman Mountain. This range consists largely of granites but also includes some limestone which has been mostly altered to marble by the intrusion of igneous rocks. The heat and pressure of these intrusions are the agencies which have effected this change. The process is one of crystallization, the massive or earthy limestone changing into an aggregation of crystals, usually white, to form marble.

PLATE XXXIX.—DESERT AT FENNER, CAL. View southeastward to Piute Mountains. Knob of rhyolite in left middle distance.

The prominent range known as the Providence Mountains, west and northwest of Fenner, consists of a thick mass of limestones and other sedimentary rocks (Cambrian, Devonian, and Carboniferous) lying on granites and cut by thick bodies of monzonite and rhyolite, These mountains are the south end of a great north-south divide which separates the Las Vegas and Colorado valleys on the east from the deserts on the west and which in general seems to be an important but little understood geologic boundary in this region. In its northern extension, known as the Charleston Range, near Good Springs, there are rich mines of lead and zinc, and a remarkable deposit of gold, platinum, and palladium ore has recently been discovered. The range contains also interesting stratified formations not found to the west in southern California. The southwestern course of the railway from Needles to Cadiz was determined for the purpose of paralleling the east side and getting around the south end of this range, which is reached at Cadiz.

The basin about Fenner is probably underlain by later volcanic rocks, portions of which protrude above the plain in many small buttes. One of these is a mile northeast of the station, and a group of them occurs about 10 miles due west of Fenner. They consist of rhyolite, a fine-grained brown glassy-looking rock, much of which contains cindery fragments and many vesicular cavities caused by the steam included at the time of outflow. In the midst of these rhyolite hills, 10 miles west of Fenner, there is an outcrop of pure white marble which some time may have economic importance.

From Fenner to Danby the railway descends the valley near its center. A short distance to the west rises a high ridge known as Clipper Mountain,¹ which consists mainly of a thick succession of Tertiary volcanic rocks, which lie on gneiss that crops out extensively at the north end of the range. This ridge is about 10 miles long and some of its peaks rise more than 1,500 feet above the surrounding plain. The rigged slopes of Clipper Mountain present a great variety of strong colors, mostly yellow and brown, due to the oxidation of the tuffs and other rocks.

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¹The rocks of Clipper Mountain are principally tuffs and agglomerates, interbedded with many thick flows of light-colored lava (rhyolite) and penetrated by a number of thick stocks of this and other igneous rocks. The tuff and ash beds near the top are capped by a thick sheet of black lava (basalt), which dips northwestward. Small masses of this kind of lava also appear at several points in the plain south and southwest of the mountain, but these are probably of later age than the summit cap. The agglomerate, tuff and ash of this succession were ejected from volcanic vents and probably accumulated very rapidly, with intervals in which eruptions of rhyolite and other lavas flowed over their surface, The final eruption was the sheet of black lava (basalt) now capping Clipper Mountain, which probably flowed out at the same time as the sheets capping Signal Peak, north of Goffs, and Black Top, southwest of Goffs, The same succession also constitutes the high ridge extending through Vontrigger to the east slope of the Providence Mountains northwest of Fenner.

Southeastern California presents the record of a varied succession of events, mostly of igneous activity on a land surface, during later geologic time. Great masses of molten rock were intruded through the various older sedimentary rocks, followed at intervals by the outflow of lavas and the ejection of fragmental volcanic material. Some of these volcanic outbursts were so recent that they appear to have been almost within the historic period. The largest bodies of lava, however, were accumulated in middle and later Tertiary time, when a vast amount of fragmental material was thrown out of numerous vents of various kinds and spread over a wide area. These formed thick deposits of breccias, which consist mostly of fragments of lava, tuff, or finer grained ejected material of the nature of ash and cinders, in part mixed with large volumes of fine volcanic ash. Most of this ejected matter was piled up as it fell, but in some places water had a part in its distribution, and from some of the vents there also came extensive mudflows. At intervals and from place to place there were great outflows of lavas of various kinds, which spread widely over the surface of the deposits of fragmental material, and subsequently were buried beneath accumulations of breccia, tuff, and ash. In general, the order of rocks erupted in Tertiary time has been latite, rhyolite, diabase rhyolite, and several varieties of basalt. The configuration of the region was probably much smoother at that time than it is now, for in general the old rock surface on which the volcanic deposits lie appears to be smooth at most localities. In places, however, ridges of older rocks protruded which were not covered by the volcanic materials. After the main period of volcanic action in Tertiary time the region was uplifted and the beds broken and tilted. It is from the erosion of this irregular surface by streams and other agencies that most of the present land forms are derived. In places the uplifted volcanic rocks have been removed, laying bare the underlying older rocks. Several times after the uplift there were extensive eruptions of later lavas some of them accompanied by the ejection of tuff, ash, and other fragmental material.

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By the judicious use of a small amount of water and fertilizer, date palms, cottonwoods, and various other plants have been cultivated at Danby, making the place an oasis in the desert. Water is obtained from a well, and an additional supply is brought by a pipe from a spring 4 miles to the northwest, where a tunnel has been run into the hillside in such a way as to gather the water seeping from a small fissure in the volcanic rocks. Clipper Mountain, with its bright-colored slopes and steep pinnacles of volcanic rocks, is a conspicuous feature north of Danby station. Five or six miles east of Danby are the Piute Mountains, and to the southeast rises Old Woman Mountain, both ranges presenting long, bare slopes and rugged peaks of granite.

From Danby to Siam, a distance of 7 miles, the railway descends the broad desert valley on a southwesterly course. Southeast of milepost 640 several scattered knobs¹ of volcanic rock rise from the desert a short distance east of the tracks. These are outliers of Ship Mountain, a short but prominent range which continues to a point 7 or 8 miles southeast of Siam. A deposit of volcanic ash and some associated tuff in the ridge 3 miles east of Siam is about 100 feet thick, and portions of it are snowy white and sufficiently pure to be serviceable as polishing powder. Material of this character is used in many of the cleansing powders now on the market.

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¹The knobs just east of milepost 640 consist of rhyolite, but farther back there is a small knob of basalt, and still farther southeast rises a prominent tabular mass in which a thick sheet of lava (basalt) caps a deposit of volcanic ash, overlying a thick body of angular fragments of gneiss. The sheet of basalt dips northeastward and passes beneath the desert plain, which is here about 10 miles wide and which extends to the west foot of Old Woman Mountain.

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A short distance south of Siam there is considerable limestone, most of which has been changed to marble by the heat of intruded granite. This marble constitutes a high ridge 2 miles southeast of Siam and several outlying knobs west of the foot of the ridge at intervals southward for 2-1/2 miles. The marble is cut off to the north as well as to the south and southeast by the granite constituting the central portion of Ship Mountain. In the Siam mine, 2 miles southeast of Siam, which was worked for several years, considerable gold and copper ore was found along or near the contact of the marble and granite. In places in the altered limestone east of Siam there are seams and pockets of yellow and red ocher of excellent quality. This material is extensively used for paints.

North of the railway beyond Siam are the Iron Mountains, a narrow but prominent range which is in general a southward continuation of the Providence Mountains. To pass the south end of this range the railway has to be deflected far southward in its course beyond Goffs.

At milepost 646 the railway passes the south end of the Iron Mountains¹ and bears slightly north of west to Cadiz. Along the west side of the mountains is a westward-facing cliff of the sandstone and limestone, surmounting rugged slopes of granite. At a point on the mountain slope 2 miles northeast of Cadiz a quarry has been opened in dark Cambrian limestone, which yields a material of attractive appearance, but it has not yet been shipped to any great extent.

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¹The Iron Mountains present a considerable variety of rocks, including pre-Cambrian granite and overlying quartzites, limestones and shales of Cambrian to Carboniferous age. These are cut by masses of intrusive rocks which have altered most of the limestone to marble. In places thick deposits of volcanic ash and tuff lie on the older rocks and are in turn overlain by a thick sheet of black lava (basalt), capped by a sheet of light-colored lava (rhyolite). The sheets of lava cap a succession of high eastward-sloping ridges on the summit and east side of the range, 6 to 8 miles north of the railway.

The granite crops out extensively in the two gaps near the south end of the range. It is overlain in ridges north and south of these gaps by rocks of Cambrian age, consisting of a basal quartzite with a thick body of overlying limestone and shale, all dipping steeply to the east. From the vicinity of milepost 645, which is about halfway between Siam and Cadiz, the contact of these sedimentary rocks on the granite is visible about half a mile northwest of the track, as shown in figure 37. The contact and the beds all dip at a moderate angle to the east. The granite has a wave-worn surface, and the beds were deposited on this surface when it was a sea bottom, a fact which establishes the age of the granite as pre-Cambrian. A small knob a short distance west of milepost 644 is of rhyolite, like the knobs east of Siam and others farther north on the east side of the Iron Mountains.

FIGURE 37.—Sketch section showing quartzite (hard sandstone) on granite at south end of the Iron Mountains, southwest of Siam, Cal., looking north.

This is the southernmost place at which Cambrian fossils have been found and apparently the southernmost outcrop of the Paleozoic rocks in this region.

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At Cadiz the main line is joined by a branch from Phoenix, Ariz., which crosses Colorado River at Parker, 60 miles below Needles, and rises with easy grade over the divide that separates the river valley from the long basin extending to Cadiz and beyond. One branch of this basin is followed by the main line of the railway from Goffs to Cadiz, far down its slope.

From Cadiz westward the course of the track is somewhat north of west, through the center of a series of wide basins bordered on both sides by high mountain ranges. The bottom of this basin is reached between Bengal and Amboy, at an elevation of 613 feet, a descent of 1,975 feet from the divide east of Goffs. The origin of this basin has not been fully ascertained, but as the depression is completely surrounded by a rock rim it can not be due entirely to erosion and probably has resulted from tilting of a portion of an old stream valley.

The bottom of the general basin consists of a series of broad saucer-like hollows or playas¹ in which lakes usually form when the rainfall is sufficiently heavy. Because evaporation is fairly rapid and the precipitation meager, these lakes soon dry, leaving their dissolved salts, such as sodium chloride and calcium sulphate, together with more or less fine sediment. These accumulations have been in progress for a long time, and there is now a thick body of them forming the floor of the basin. Sodium chloride (common salt) exists in large amount, and there is also considerable gypsum. These deposits are quarried extensively east of Amboy. At Saltus siding, near milepost 657, there is a salt refinery a short distance south of the railway, which ordinarily produces a car or two of salt a day. The salt is mined 4 miles farther south, in the lowest part of the basin, and brought by the company's railway to the works, where it is refined for market. The mining is done by open pits. The salt is covered by a few feet of sand, under which the nearly white rock salt forms a pavement of wide extent. It is in several layers, separated by thin deposits of silt, and from 5 to 7 feet of it is taken out at most places.

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¹A playa is a shallow, flat-floored depression, characteristic of valleys having no regular drainage to the sea, in which storm waters collect and evaporate. It may be a shallow lake or a salt-incrusted mud flat.

In his description of the ancient Lake Lahontan, in Nevada, Russell writes:

"The scenery on the larger playas is peculiar and is usually desolate in the extreme but is not without its charm. In crossing these wastes the traveler may ride for miles over a perfectly level floor, with an unbroken sky line before him and not an object in sight to cast a shadow on the ocean-like expanse. Mirages, which may be seen almost every day on these heated deserts, give strange fanciful forms to the mountains and sometimes transfigure them beyond recognition. A pack train crossing the desert a few miles distant may appear like some strange caravan of grotesque beasts fording a shallow lake, the shores of which advance as one rides away. The monotony of midday on the desert is thus broken by elusive forms that are ever changing and suggest a thousand fancies which divert the attention from the fatigues of the journey. The cool evenings and mornings in these arid regions, when the purple shadows of distant mountains are thrown across the plain, have a charm that is unknown beneath more humid skies, and the profound stillness of the night in these solitudes is always impressive.

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The gypsum occurs in irregular bodies, one of which crops out along the railway from milepost 657 nearly to Amboy. It forms a white crusty surface with protruding lumps of harder masses of the mineral. A short distance north of the track, as well as at Amboy, it is covered by wash from the mountain slopes. Just south of milepost 659 there are extensive pits 6 to 8 feet deep in which the gypsum is obtained. It is carried by a small railway to the plaster mill at Amboy, where it is heated to expel the water and ground to the fine powder known as plaster of Paris.

Amboy is dependent on the plaster mill and a few mines in the mountains. A stage line which runs to Dale, a mining camp 45 miles to the south, crosses the lowest part of the basin near the salt deposit and goes through a pass or depression in the Sheep Hole Mountains, which are about 11 miles distant. These mountains consist of granite and schist of pre-Cambrian age and form a part of the topographic barrier of granite and other igneous rocks which borders the south side of the valleys traversed by the railway as far as Barstow.

The Marble Mountains, constituting the north rim of the basin a few miles north of Amboy, consist mainly of coarse-grained granites, mostly light gray, penetrated by large bodies of dark coarse-grained quartz monzonite. Many masses of limestone altered to white marble occur north and northeast of Amboy. At one locality 4 miles north of Amboy considerable iron ore has replaced the limestone near the igneous contact. In the foothills of this range 2-1/2 miles north of Amboy there is a low ridge of light-colored lava (rhyolite), and a short distance northwest of this a large rounded hill of fine-grained, dark-colored rock (diorite), probably much older than the lavas. A mile east of these knobs is a small pit in light-colored clay which has been used for mixing with the plaster at the Amboy mill. This clay is probably part of the mass of earlier sediments that underlie the valley and are here upturned along the foot of the mountain rim. A 700-foot well in Amboy is reported to be entirely in sand and gravel and to have yielded only salt water, which occurred in considerable volumes, especially near the surface. At a depth of 70 feet it penetrated a deposit of gypsum.

Summer temperatures in this part of the desert are very high, those at Amboy often exceeding 120° F. However, the mean annual temperature at Amboy is much less than that of places at lower altitudes farther south within our borders, a maximum of 130° having been recorded at Salton, in the Colorado Desert. The rainfall in the desert region of southeastern California to Barstow and beyond is very small, averaging only about 5 inches a year. West of Amboy the train passes a series of rather recent volcanic cones and lava flows.

In the center of the basin, not far southwest of Amboy, there is a fine cinder cone on an extensive sheet of black lava (basalt). This lava is, geologically, very recent and may have flowed out over the bottom of the basin within the last thousand years. It covers a nearly circular area about 5 miles in diameter. Its surface is remarkably rough, being covered with large blisters, most of them broken, and it has many caverns where the hot lava has run out at lower levels as it congealed at the surface. All the rock is black, practically unchanged by weathering, and full of vesicles or small holes, due to the escape of steam carried by the molten lava. The edge of the sheet is irregular, just as the lava congealed at the margin of the flow. At milepost 664 the railway is at the north edge of the lava, which it follows for a mile or more to the west, affording an exceptionally interesting and instructive view of the flow and cone. The cone, which is near the center of the flow, about 2 miles south of milepost 664, is about 200 feet high. It consists of a pile of black or dark-gray cinders or pumice, with a large crater in the center. In its southwest side there is a deep breach, from which extends a thin later sheet of lava that flowed out over the main sheet. This accumulation of cinders marks the later stage of the eruption, when the vent sputtered out a shower of cinders and fragments of lava frothing with steam bubbles. At the same time there were ejected occasional bombs of more or less completely consolidated lava, which are now embedded in the cinder. This volcano and the one at Pisgah, 43 miles farther west, are exceptionally good examples of a modern lava flow, and many features of both are visible from the train. The structural relations of flows of this character are shown in figure 38.

FIGURE 38.—Ideal section through a recent lava field and vent.

From Amboy to Bagdad the railway line begins to rise gradually on the west slope of the basin.

All trains stop at Bagdad for water and fuel oil. The water is brought daily on a train of 20 tank cars filled from springs at Newberry, 56 miles to the west. Deep borings at Bagdad and at other points in the basin have obtained only salt water.¹ A short distance north of Bagdad is a low ridge which extends far to the northwest. It consists of dark massive igneous rock (quartz monzonite), overlain by volcanic tuffs and sheets of lava (rhyolite). About 9 miles north of Bagdad are the Marble Mountains, already mentioned. In this range is located the Orange Blossom mine (in granite aplite), which has yielded copper ore carrying more or less gold.

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¹In preserving for the traveler the water supply of this desert country the cactus plays an interesting part. The roots of this distinctly American plant extend widely, for the most part at 2 to 4 inches below the surface, so that they suck up a quantity of water from the soil very quickly after a rain. Once stored in its tissues this water is retained by the cactus with great tenacity. Water absorbed by plants is evaporated through their green surface. Most of the cactuses have leaves, but as a rule the leaves are minute or even microscopic and the structure of their cells is such as to hinder transpiration and conserve the water stored. In the walls of the cells are thin sievelike places which permit the easy passage of water from one cell to another throughout the interior. A barrel cactus was found to contain 96 per cent of its weight of water. The water contained in cactuses is often palatable, but not invariably so. It is interesting to note that those in which the water is nauseous are lees protected by spines than those whose juice is sweet and tempting. In experimenting with desert mice it was found that they will not drink water, a fact which suggests that they secure moisture from the plants they consume, or possibly they have a special means of separating moisture from the air. The spines of the cactus are straight or curved, hairy or feathery, and grouped in starry clusters or in rows. They have been used for fishhooks, needles, and combs and in various other ingenious ways by the primitive tribes. The flowers of the cactus vary in form, and most of them are extremely beautiful. The different species display brilliant tints of purple, yellow, orange, and rose. Some open by day; others by night. Many of the species bear edible fruits, and the seeds of some are used by the Indians for food.

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South of Bagdad there is a desert plain 8 miles across, partly filled on the east with the lava sheet. West of this sheet the flat contains salty and gypsum-bearing deposits, mixed with more or less fine sand. This is the west end of the basin which contains the salt and gypsum east and south of Amboy but which, just west of Amboy, is floored with lava. On the south side of the basin rises a prominent ridge of volcanic rocks of supposed Tertiary age, consisting of agglomerate and tuff associated with large bodies of light-colored lavas (latite and rhyolite). An old lead-silver mine in this range has produced considerable high-grade ore from a vein that is exceptionally well exposed at the surface. Three miles farther south is the high range known as the Bullion Mountains, which consists of igneous rocks of various kinds.

West of Bagdad the train begins to climb rapidly out of the basin along the slopes of cinder cones and masses of black lava (basalt) lying on older granitic rocks. Halfway between mileposts 672 and 673 a small black hill south of the railway is evidently the remnant of a cone or larger mass of basalt. Near milepost 674 there is in view just north of the track a large cone made up of inclined beds of reddish cinder.

Another similar cone is also visible a few miles farther northeast. As the train ascends the slope to the north it approaches hills and ridges of volcanic tuff and ash, overlain in places by flows of basalt. A mile south of milepost 678 several small, low black knobs rise out of the desert plain, probably the remnants of an old crater or a flow of lava (basalt), considerably eroded and buried by sand and gravel. West of Siberia siding the railway makes some long, sweeping horseshoe curves in rising on the slope of the basin. These curves give fine views back into the wide basin, in which the cinder cone near Amboy is a prominent feature. At Klondike siding (milepost 682) an altitude of 1,652 feet is attained. To the northeast are hills of volcanic tuff and ash, and one long butte capped with black lava (basalt). To the southwest is a group of hills of tuff with bodies of light-colored lava (rhyolite), which extends for some distance west.

At milepost 684 the railway is just south of hills of volcanic tuff, capped with basalt, and just south of the track is the end of a lava flow at a lower level, upon which the train runs within a short distance. At the next milepost the lava of this flow is exposed in railway cuts. It occupies a saddle or wide valley which extends westward past Ash Hill siding. Here the train passes over a divide (altitude 1,944 feet) in a depression between the hills, to the north and south, which rise a hundred feet higher. The entire surface of the divide, as well as the adjoining slopes, is covered with a lava flow (basalt) of relatively recent age though not nearly so recent as the one in the basin near Amboy. The lava extends down the west slope also nearly to Ludlow; its source was probably in the hills north of Ash Hill siding, but no evidence of a crater was noted in that area.