GRANITIC ROCKS OF THE YOSEMITE VALLEY AREA, CALIFORNIA*
By FRANK C. CALKINS
U.S. Geological Survey, Menlo Park, California, and
DALLAS L. PECK
U.S. Geological Survey, Menlo Park, California
BRIEF HISTORY OF DISCOVERY AND GEOLOGIC INVESTIGATIONS
The Yosemite Valley was discovered by William Penn Abrams in 1849, but it first became well known when it was rediscovered in 1851 by the Mariposa Battalion, under the leadership of Major James D. Savage, while pursuing the Indian tribe called the "U-zu-ma-ti" (meaning "grizzly bear"), led by Chief Tenaya. The members of the Battalion gave the valley the name that they understood to be that of the tribe; the Indians themselves called it "Ahwahnee", meaning "deep, grassy valley". The valley achieved national fame through the writings of Dr. Lafeyette Bunnell, James Hutchings, John Muir, the Reverend Thomas Starr King, and others. In 1864 an area that included the Yosemite Valley and also the Mariposa Grove was set aside by the Federal Government as the Yosemite Grant; this area was administered by California until 1905, when it was included in the much larger Yosemite National Park, which had been established in 1890.
Geologic investigations in the Yosemite Valley region, most of which have been summarized by Matthes (1930, p. 4-7), were begun in the early 1860's by J. D. Whitney, State Geologist of California, who was assisted by Clarence King. Whitney (1868) and King (1874) concluded that the valley was formed by faulting so recent that the valley walls had not been greatly modified by subsequent erosion. In the late 1860's and later this view was challenged by W. P. Blake (1867), John Muir (his extensive bibliography was published in the Sierra Club Bull. vol. 10, p. 41-54, 1916, but see particularly Muir, 1874 and 1875), and Joseph LeConte (1873), who attributed the formation of the valley to glacial and stream erosion. The general extent of the Sierra Nevada composite batholith was described in the 19th century in geologic reports and folios by H. W. Turner, Waldemar Lindgren, and others, but detailed study of this vast intrusive complex is still going on and may continue for years to come. Near the turn of the century Turner began to map the geology of the Yosemite and Mount Lyell quadrangles, but was never able to complete this difficult assignment. Shortly before World War I, F. E. Matthes and F. C. Calkins began a highly detailed study of the physiography and bedrock geology of the Yosemite Valley area and a less detailed mapping of surrounding areas in the Sierra Nevada (1930), but the complex bedrock geology of the valley has not even yet been fully mapped. Ernst Cloos (1936) plotted structural features in the granitic rocks of the Yosemite region, Blackwelder (1931, p. 907-909; 1939) related the glacial stages to those of the eastern flank of the Sierra Nevada; and Curtis and others (1958) obtained potassium-argon ages of some of the granitic rocks.
The rocks in which the Yosemite Valley was carved belong almost wholly to the great Sierra Nevada composite batholith, which extends continuously along the range for about 400 miles and has a maximum breadth of about 100 miles. The rocks of this batholith were intruded into sedimentary and volcanic rocks of early Paleozoic to Mesozoic (Late Jurassic) age. As shown by Bateman and others (in press) it was emplaced along the axis of a synclinorium in those layered rocks. The prebatholithic rocks are not represented in the Yosemite Valley except by a few small masses not visible from the valley floor, but the roads from the west pass through them for many miles on the way to El Portal (see description by Clark in this guidebook), and they are widely exposed on the east side of the batholith along the crest of the range. Rinehart and others, (1959), found that pre-batholithic rocks they mapped in the Devils Postpile and Mount Morrison quadrangles have a total thickness of about 60,000 feet. The lower half of the stratigraphic column there consists of sparsely fossiliferous Ordovician to Permian (?) hornfels, metamorphosed calcareous sandstone, slate, and marble; these are overlain conformably by about the same thickness of metamorphosed pyroclastics and lavas, with a few minor interbeds of calcareous and tuffaceous rocks which have yielded fossils of Early Jurassic age.
It needs to be emphasized that the Sierra Nevada batholith is composite. Some people fail to realize how complex it is, and what a long and eventful history it has had. At least seven irregular intrusive bodies such as are commonly called stocks, are exposed in the walls of Yosemite Valley and the Merced Gorge, and measurements of potassium-argon ratios indicate that the oldest and youngest of these differ in age by about 12 million years, though all of them were intruded in Cretaceous time. The stocks are cut, moreover, by dikes and irregular sheets of at least half a dozen other kinds of rocksnot counting pegmatites and aplites. On the nearby uplands, moreover, within the area drained by tributaries of the Merced and the headwaters of the Tuolumne, one can see exposures of many other intrusive bodies, large and small. If this area gives us anything like a fair sample, the Sierra Nevada batholith was formed by scores, if not hundreds, of distinct intrusions, and the making of it may have taken something like 15,000,000 years.
Brief descriptions are given below of the intrusive rocks exposed in the valley and the gorge, and also of two others that are closely related to the rock forming the falls of the eastern part of the valley, but that could not be reached without going eastward to the Tuolumne Meadows. The distribution of the major intrusive rock units in the Yosemite Valley area is roughly shown in figure 1.
The rocks that form relatively large bodies exposed in the Yosemite Valley and in line with it to the east and west may be assigned to two series, the western and the Tuolumne intrusive series. The western intrusive series, which is the older, forms the walls of the western half of the valley, and of the canyon of the Merced down to El Portal. The younger rocks of the Tuolumne intrusive series are exposed in the eastern half of the Yosemite Valley and in the high country still farther east, which is drained in part by the Tuolumne River. The rocks of both series are cut by aplites and pegmatites, which will not be described and which are not included in the group to be considered next.
Generally intermediate in age and position between the intrusive bodies, of large to moderate size, that have been assigned to the western and Tuolumne series, there are a great many dikes, sills, and small irregular bodies that do not clearly belong to either series. All of them are probably younger than any rock of the western series. None is now known to be younger than any rock of the Tuolumne intrusive series, but one or two of them could be. Because of these uncertainties, combined with the fact that no potassium-argon ratios have been determined for any of these minor intrusive bodies it seems expedient to put them in a separate group. In the petrographic summary they are placed between the western and Tuolumne series. They are for the most part at least intermediate in age between the two, and are mainly exposed in the middle part of the valley.
The extreme complexity of the intrusive pattern in the Cathedral Rocks and El Capitan suggeststhough it does not provethat a local subsidence occurred in the area crossed by the middle part of the valley, perhaps shortly after the intrusion of the western series was completed. Such a mechanism could help to account for the generally flat-lying attitude of the intrusive bodies of Bridalveil granite; withdrawal of support would have tended to open approximately horizontal fissures into which magmas would be injected from a pluton that has not been identified and may not be exposed. But subsidence would also have opened steep fissures to be filled by dikes. There is evidence, also, that sulfide-bearing solutions arose along some of the steep fissures, for here, and nowhere else in the Yosemite Valley area, some of the rocks contain a little pyrite, the weathering of which produced iron oxides that have locally imparted a red color to the outcrops, especially on the southwestern slopes of the Cathedral Rocks. In a few places, moreover, a very little molybdenite has been found.
Western Intrusive Series
The sequence of intrusion within the western series is not fully known. Field relations prove that the Taft granite is its youngest member, that it was preceded by El Capitan granite, and that El Capitan was preceded by both the diorite of the Rockslides and the granite of Arch Rock. No field evidence had been obtained, however, regarding the relative ages of the granite of Arch Rock, the above-mentioned diorite, and the granodiorite of The Gateway. Potassium-argon ratios obtained by Curtis and others (1958) indicate that the granite of Arch Rock is older than the granodiorite of The Gateway, and the latter rock older than El Capitan granite. This dating of the granite of Arch Rock seems questionable because it does not accord with the usual order in an intrusive seriesthat of increasing silica content. It is nevertheless provisionally accepted in the petrographic summary, in which the diorite of the Rockslides is assumedagain provisionallyto be the oldest member of the series.
Minor Intrusive Bodies
The order in which the small bodies were intruded is not fully known and may never be completely worked out. We do not even know how many different kinds of rock they consist of, and only a few are described herein, in an order that represents the best guess we can make regarding their relative age. The one that occupies the largest areas on the map (fig. 1) is the Bridalveil granite. This cuts nearly all of several rocks with which it is in contact, but although it is widely exposed on the south side of the valley, especially in the Cathedral Rocks and along Bridalveil Creek, it has not been positively identified on the north side. The youngest of all these rocks may be the diorite forming the "Map of North America," on the face of El Capitan, which cuts across a dike, sloping upward toward the east, of a gray rock that is probably Leaning Tower quartz monzonite. This diorite does not differ much from the diorite of the Rockslides except in being generally finer grained. As we have provisionally regarded the older diorite as the oldest member of the western series, the younger diorite is possibly to be regarded as the oldest member of the Tuolumne intrusive series; for the present, however, it is not described as such.
Tuolumne Intrusive Series
After having had to confess how much we don't know about the order of intrusion in the western series and the minor intrusive bodies, it is a relief to come to the Tuolumne intrusive series. For here the sequence of intrusion is clearly shown by field relations, and confirmed by measurements of potassium-argon ratios in all four members. The order of intrusion appears, also, to be that of increasing silica content, which is commonly regarded as the normal order; this however is as yet uncertain because of a lack of analyses. The outcrops of the four members, moreover, are roughly concentric in the central part of the area occupied by the series, the latest member being in the center. Because this series is so definitely a unit, we briefly describe it as a whole, even though only its two oldest and outermost membersthe Sentinel granodiorite and the Half Dome quartz monzoniteare exposed in the Yosemite Valley. In the Yosemite Valley one cannot even see the porphyritic facies of the Half Dome quartz monzonite into which the non-porphyritic facies, exposed around the head of the Yosemite Valley and in Half Dome itself, grades near Tenaya Lake. The porphyritic Half Dome quartz monzonite is cut in that vicinity by dikes of the Cathedral Peak granite, and one can see from the valley floor, in the cliff west of the Royal Arches, flat-lying tongues of streaky Half Dome quartz monzonite extending into the Sentinel granodiorite. A little farther west, in the Castle Cliffs, the granodiorite is intruded into the El Capitan granite in an extremely complex fashion, forming a pattern that has to be greatly generalized even at a scale of 1:24,000 and could merely be suggested in figure 1. Little of this pattern can be seen from the floor of the Yosemite Valley; it is better exposed along Yosemite Creek above its falls and on the upland south of Glacier Point.
The following short descriptions do not aim to do much more than help those interested to distinguish the principal rocks from one another. The rocks described by Calkins (1930, p. 120-129), are here called by the names used in that publication. These names are largely based on megascopic rather than microscopic features, and some of them do not depend as much as some petrographers would like upon relative abundance of potassium feldspar and plagioclase. The dominant rock of El Capitan, for example, was called by H. W. Turner (1900, p. 304, 308) El Capitan granite, and that name has come into general use. It is based on the fact that the dominant facies of the rock contains abundant and conspicuous potassium feldspar and quartz, and only a small proportion of its one ferromagnesian mineral, biotite. Roughly quantitative measurements of mineral composition indicate, however, that the dominant rock of this intrusive mass is a quartz monzonite if the feldspar ratio is made the criterion, though it contains more quartz than most quartz monzonites.
The rocks are listed in what is regarded as their most probable order of agethe oldest first. Whenever the age of a rock has been estimated from the potassium-argon ratio by Curtis and others (1958, p. 7), the result, in millions of years, is given at the end of the description as "K/Ar agem.y."
Rocks of the Western Intrusive Series
Diorite of the Rockslides. General color very dark greenish-gray. Texture varies from very coarse to medium-grained. Chief minerals plagioclase and hornblende, the latter being the more conspicuous; most specimens also contain subordinate quartz, potassium feldspar, and biotite, and some contain a little augite. The rock may be in part a metagabbro.
Granite of Arch Rock. Medium-light-gray, medium-grained, non-porphyritic. Plagioclase predominates over potassium feldspar, which is generally poikilitic, as can be seen by reflections from cleavage faces. Quartz moderately abundant. In most of the rock the only ferromagnesian mineral is biotite (subhedral to anhedral), but a little hornblende is present in some places.
K/Ar age 95.3 m.y.
Granodiorite (or Quartz Diorite) of The Gateway. Dark-gray, medium-grained. Potassium feldspar subordinate; some of the rock does not contain any. Biotite is fairly abundant, hornblende less abundant but everywhere present.
K/Ar age 92.9 m.y.
El Capitan Granite. Light-gray, medium-coarse-grained. Some is vaguely porphyritic, with phenocrysts of potassium feldspar. Plagioclase is more abundant but in smaller grains. Quartz is conspicuous. Biotite, in moderate quantity, is the only ferromagnesian mineral, though a little hornblende may occur in marginal facies:
K/Ar age 92.2 m.y.
Taft Granite. Very light gray, medium-grained. Typical facies finer-grained and more uniform than El Capitan granite and not porphyritic, but a rock that may be a porphyritic facies of the Taft, exposed near the east portal of the Wawona tunnel, contains phenocrysts of potassium feldspar. Plagioclase, potassium feldspar, and quartz about equally abundant; biotite scarce.
Rocks of Minor Intrusive Bodies
Leaning Tower Quartz Monzonite. Color medium-gray; texture medium-grained granular. Contains biotite and less hornblende; these are largely in clusters, about 10 mm in maximum diameter, which give the rock a characteristic speckled appearance.
Bridalveil Granite. Medium-gray; the fresh rock has a slightly bluish tinge. Fine-grained, granular. Biotite moderately abundant, in small, evenly distributed flakes which give the rock a "pepper-and-salt" appearance.
Quartz-Mica Diorite. Medium-dark gray, medium-fine-grained, granular. All consists mainly of plagioclase, quartz, and biotite; most contains subordinate potassium feldspar and some contains a little hornblende. Not shown in figure 1.
Diorite of the "Map of North America". Similar to the diorite of the Rockslides but finer-grained. Represented by the same pattern as the diorite of the Rockslides.
Rocks of the Tuolumne Intrusive Series
Sentinel Granodiorite. Generally medium-dark gray and medium-grained granular, but varies rather widely in both color and texture. Near contacts with El Capitan granite the rock tends to be darker than elsewhere and more or less foliated. Plagioclase predominates over potassium feldspar; quartz is inconspicuous. Biotite is fairly abundant and hornblende only a little less so; both are In irregular grains tending to cluster together.
K/Ar age 86.4 m.y.
Half Dome Quartz Monzonite. Lighter-colored and more uniform in both color and texture than the Sentinel granodiorite. Its potassium feldspar, though only about half as abundant as plagioclase, is more conspicuous because in larger crystals. In a porphyritic facies exposed near Lake Tenayanot seen from the Yosemite Valley there are numerous phenocrysts of potassium feldspar. Biotite and hornblende are less abundant than in the Sentinel granodiorite, and both tend to form discrete, fairly regular crystals.
K/Ar age 84.1 m.y.
Cathedral Peak Granite. A light-gray rock, characterized by numerous large phenocrysts of potassium feldspar (some as much as 2 inches long) in a medium-grained granular groundmass consisting of both feldspars, much quartz, a moderate amount of biotite, and a little hornblende. Not exposed in the area of figure 1, but boulders of this rock in the moraines of Yosemite Valley are among the evidences for glaciation of the Sierra Nevada.
K/Ar age 83.7 m.y.
Johnson Granite Porphyry. A porphyritic rock, lighter-colored and finer-grained than the Cathedral Peak granite; contains a little biotite but no hornblende. Not exposed in the Yosemite Valley.
The major features of the Yosemite Valley are due to erosion by streams and glaciers, whose handiwork was described at length in Matthes's classic paper (1930) and has been summarized in another section of this guidebook. But sculptural detail, in this area as in any other, depends to a large extent on the material that erosional agencies had to deal withon what rocks they encountered as they worked downward. If the bedrock in the upper-middle part of the Merced basin had been of uniform composition and structure, erosion would never have produced a Yosemite Valley. One reason for the astonishing variety of sculpture that causes the Yosemite to stand unrivalled in the Sierra Nevada or anywhere else for the magnificence of its falls, cliffs, and domes, all displayed within a distance of about 7 miles, is the varied nature of the rocks in which it was carved. The differences that matter in this regard are differences in susceptibility to erosion. These are not due mainly to differences in hardness, which are not very great. There are greater differences in resistance to weathering, but these again would not have had very much effect if the rocks had all been jointed to the same extent. The great contrasts in topographic expression arise from the different degrees to which the various rocks have been jointed. Broadly speaking, the more siliceous rocks of the Yosemite Valley are less jointed than the less siliceous rocks. It has been thought, however, that in other areas texture rather than composition is the determining factor, the finer-grained rocks being the more closely jointed. The degree of jointing in the various intrusive rocks may therefore be the resultant effect of both factors in combination. El Capitan, whose southeast face is one of the highest unbroken cliffs in the world, consists chiefly of two of the most siliceous rocks that form large intrusive bodies in this areanamely El Capitan and Taft granitesand these determine its character even though they are cut by many small bodies of less siliceous rocks. The Cathedral Rocks and the Leaning Tower also probably stand out as they do because, though of extremely complicated makeup, they consist mainly of siliceous rocks. El Capitan granite is one of the most abundant materials in them, and the minor intrusive bodies here consist mainly of Bridalveil granite. Half Dome, the greatest monolith of all, and also the other prominent domes overlooking the eastern part of the valley, consist of the Half Dome quartz monzonite. This rock, judging from its mineral composition, appears to be a little less siliceous than El Capitan granite, but it is not cut by any rocks that are less siliceous, and this fact may help to account for its almost complete lack of joints. It is indeed cut by many narrow dikes of pegmatite and aplite, but these are more siliceous and even more resistant than the dominant rock, so that great numbers of them stand out in relief on the southern slope of Half Dome.
The Half Dome quartz monzonite is mainly in huge masses almost free from joints, and these have disintegrated for the most part by exfoliation, which occurs here on a grand scale. That is why this rock forms nearly all the domes; the single exception is Sentinel Dome, which consists of El Capitan granite. The Royal Arches reveal a cross section of exfoliation cracks in the quartz monzonite that are too far below the surface to form the tops of domes.
The rock nearest in composition to the Half Dome quartz monzoniteon the less siliceous sideis the Sentinel granodiorite, which is cut by numerous joints. The lower part of the cliff east of Glacier Point consists of unjointed Half Dome quartz monzonite, but this is overlain, on an intrusive contact sloping gently westward, by the granodiorite, which is considerably jointed; in fact the eye can trace the contact quite closely, from a viewpoint near the Ahwahnee Hotel, by noting this difference in structure. Many of the joints in the granodiorite strike about east-northeast and are nearly vertical; joints of this character have mainly determined the form of Sentinel Rock. The sheer cliff below Glacier is developed along vertical joints that trend almost due east. In the zone where there are complex intrusive relations between this granodiorite and El Capitan granite, the amount of jointing largely depends on which rock is the more abundant.
The least siliceous of the principal intrusive rocks is the diorite of the Rockslides, and although rather coarse grained on the average it is by far the most closely jointed. For this reason it is exposed in only one large area, above the lower part of the Big Oak Flat Road, where it is cut by countless irregular joints, both steep and flat-lying; many of the flat ones are injected with sheets of light-colored intrusive rock. The diorite is held up here by a backing of Taft granite, which forms the upland surface immediately to the north. Turtleback Dome and Elephant Rock, south of the river, consist mainly of El Capitan granite.
The slope on the west side of the Merced Gorge consists mainly of the granite of Arch Rock. This is intermediate in composition between El Capitan granite and the diorite of the Rockslides, and it is likewise intermediate between them in the character of its jointing, though in both respects it resembles El Capitan granite more closely than it does the diorite. It is here cut by fairly numerous joints, most of which strike northeastward and are nearly vertical but somewhat irregular.
The large taluses on the sides of the Yosemite Valley contribute greatly to the variety of its sculpture, because they present so striking a contrast with the cliffs and "points" in which the bedrock extends nearly to the valley floor. There is reason to believe that the taluses are largely underlain by rocks that are closely jointed, so that their surfaces receded more rapidly than those of rocks containing few joints. The moderately large talus around the mouth of Indian Canyon is presumably underlain in large part by Sentinel granodiorite. The bedrock under the three largest talusesthe Rockslides and the taluses east and west of Bridalveil Canyonis probably made up in considerable part of diorite. The Rockslides are flanked on the west by the largest exposures of the older diorite, and it seems likely that their eastern part covers an area in which the diorite receded all the way northward to its contact with El Capitan granite. Diorite is exposed in many places around the borders of the taluses on the south side of the valley east and west of Bridalveil Canyon; some of it can be seen near the east portal of the Wawona Tunnel.
One of the strangest features of the Yosemite Valley's topography is the manner in which the lower part of Bridalveil Canyon projects beyond the general course of the valley's southern wall. Bridalveil Fall springs from the end of what might almost be likened to a gigantic flumethough a very lop-sided one, since the Cathedral Rocks, on its northeast side, are of much greater bulk than the Leaning Tower, on its southwest side. This abnormal relation of relief to drainage appears to be partly explainable on the hypothesis that the rocks along Bridalveil Creek are much more siliceous, on the whole, than those underlying the great aprons of talus to the east and west.
So much for the topographic features whose character expresses jointing or the lack of it. But some notches and other depressions were eroded along more persistent fractures that may somewhat arbitrarily be distinguished as fissures.1 Fissures, and fissure zones, cut across all kinds of rocks, even those in which there are few joints. They were doubtless formed by local concentration of strain, and there was probably some movement along them, though none have been shown to be large faults. Since many of the features due to fissuring were well described by Matthes (1930, p. 111-114) only a few of the more important will be noted here.
The west side of El Capitan is bounded by a north-south fissure zone in the lower part of which there is a basic dike, and the next main drainage way must have been eroded along another fissure zone that strikes northeastward. The middle Cathedral Rock is separated from the others by deep notches eroded along steep fissures that also strike about northeast, and the Cathedral Spires are probably bounded by vertical fissures. The Three Brothers, two miles northeast of El Capitan, which consist mainly of El Capitan granite, are separated from one another by two fissures, or master joints, that dip about 45° W.
The great monolithic mass of Half Dome itself is bounded on the northwest by a smooth, nearly vertical 2,000-foot cliff that must form the wall of a fissure, presumably the southeasternmost in a fissure zone that determined the course of Tenaya Creek. The Half Dome quartz monzonite is also cut by at least one gently dipping fissure that slants downward to the north in the lower part of the southwest face of Liberty Cap.
Steep fissures probably determined the location of many of the cliffs bordering the Yosemite Valley. The valley itself may have been eroded along a complex fissure zone which is now mostly concealed by alluvium; the two fissures that separate the Cathedral Rocks from one another may belong to this zone.
Bateman, P. B., Clark, L. D., Huber, N. K., Moore, J. G., and Rinehart, C. D., in press, The Sierra Nevada batholitha synthesis of recent work across the central part: U.S. Geol. Survey Prof. Paper.
Blackwelder, Eliot, 1931, Pleistocene glaciation in the Sierra Nevada and Basin Ranges: Geol. Soc. America Bull., v. 42, p. 865-922.
Blackwelder, Eliot, 1939, Contribution to the history of glaciation in the Yosemite region (abstract): Geol. Soc. America Bull., v. 50, p. 1947.
Blake, W. P., 1867, Sur l'action des anciéns glaciers dans la Sierra Nevada de Californie et sur l'origine de la Vallée de Yosemite: Compt. Rend., v. 65, p. 179-181.
Calkins, F. C., 1930, The granite rocks of the Yosemite Region, in Matthes, F. E., Geologic history of the Yosemite Valley: U.S. Geol. Survey Prof. Paper 160, p. 120-129.
Cloos, Ernst, 1936, Der Sierra-Nevada-Pluton in Californien: Neues Jahrb., B-B. 76, Heft 3, Abt. B, p. 355-450.
Curtis, G. H., Evernden, J. F., and Lipson, J., 1958, Age determination of some granitic rocks in California by the Potassium-Argon method: California Div. Mines Spec. Rept. 54, 16 p.
King, Clarence, 1874, Mountaineering in the Sierra Nevada, 4th Ed.: Boston, James R. Osgood and Co., 308 p.
LeConte, Joseph, 1873, On some of the ancient glaciers of the Sierras: Am. Jour. Sci., 3rd ser., v. 5, p. 325-342.
Matthes, F. E., 1930, Geologic history of the Yosemite Valley: U.S. Geol. Survey Prof. Paper 160, 137 p.
Muir, John, 1874 and 1875, Studies in the Sierra: Overland Monthly, v. 12, p. 393-403, 489-500; v. 13, p. 67-79, 174-184, 393-402, 530-540; and v. 14, p. 64-73.
Rinehart, C. D., Ross, D. C., and Huber, N. K., 1959, Paleozoic and Mesozoic fossils in a thick stratigraphic section in the eastern Sierra Nevada, California: Geol. Soc. America Bull., v. 70, p. 941-946.
Turner, H. W., 1900, The Pleistocene geology of the south central Sierra Nevada with especial reference to the origin of Yosemite Valley: Calif. Acad. Sci., Proceed., v. 3, p. 261-321.
Whitney, J. D., 1868, The Yosemite book; a description of the Yosemite Valley and the adjacent region of the Sierra Nevada, and of the big trees of California: California Geol. Survey, 116 p.
Last Updated: 03-Aug-2009