DANIEL I. AXELROD Dept. Geology, University of California, Los Angeles, Calif.

Post- Uplift of the Sierra Nevada, California

Abstract: Reconstructed stream profiles and paleo- The postulate of a high Tertiary barrier, and of botanical evidence suggest that in the Yosemite only 4000 (Yosemite sector) to 2000 feet (Lake region altitude increased approximately 4000 feet Tahoe sector) uplift in the raises prob- following the Broad Valley stage. Since this was lems: the Tertiary section has defied erosion; fine- preceded by a 2500- to 3000-foot uplift of the Late grained sediments were deposited well up in the Pliocene ("") surface during the range and at its summit; formations were deposited Plio-Pleistocene transition, total post-Pliocene up- across the crest; Tertiary rivers and basalt flowed lift is about 6500-7000 feet. across the summit; faulting and warping of dated With similar methods, divergent results have sections and erosion surfaces show post-Pliocene been reported for the Lake Tahoe sector. The uplift of 4000-9000 feet; and the scarps have re- presence in the summit region of de- sisted erosion. These "problems" disappear if the ciduous hardwood forests typical of mild-tem- range originated as a major post-Pliocene topo- perate climate, the absence there of montane graphic barrier. conifers, the spatial relations of the Miocene forest Two basic weaknesses to the method of de- zones, and the regional pattern of climate they sug- termining Tertiary altitude from ancient stream gest all imply altitudes near 2000 feet. Recon- profiles are: (1) The assumption that certain well- structed stream profiles indicate an altitude of graded stretches of the ancient streams had pretilt 5000-7000 feet. These results are tested for plausi- slopes equal to those of well-graded parts of the bility by utilizing (1) sea-surface temperatures to modern rivers does not agree with the nature of calculate temperature and, hence, climate, at any the Tertiary sediments in the range. (2) Recurrent altitude postulated for the Sierran summit and (2) tectonism during the Tertiary tilted the basement sequences of later Tertiary floras on opposite sides and Tertiary river channels, giving them gradients of the barrier to determine the magnitude of the more nearly like those of present-day streams, and, rain shadow. Both lines of evidence suggest only hence, the illusion that the range has not been up- low altitude lifted appreciably since Eocene.

CONTENTS Introduction 184 Formations deposited across summit area ... 192 Acknowledgments 184 Origin of scarps 192 Yosemite region 184 Displacement on scarps 193 Introductory remarks 184 Uplift from stream profiles 193 Erosion surfaces for determining uplift . . . .184 Introductory remarks 193 Ages of erosion surfaces 185 Graded rivers 193 Total uplift 186 Tertiary tectonism 195 Amount 186 Conclusion 195 Evidence in Mount Whitney region 186 References cited 196 Matthes' Sierran upwarp 187 Lake Tahoe region 187 Figure Introductory remarks 187 1. Topographic relations of erosion surfaces in the Paleobotanical evidence for low relief 188 Sierra Nevada 185 and related modern forests 188 2. Comparison of rainfall trend on opposite sides Altitudinal belts of vegetation 188 of the Sierran axis during later Tertiary . 191 Regional climatic pattern 189 Tests for plausibility of results 189 Table Marine paleotempcratures 189 1. Major Sierran erosion surfaces, their correlation No rain shadow, no high relief 191 and age 185 High Tertiary relief makes geologic problems . 192 2. Late Miocene sea-surface temperature and in- Introductory remarks 192 ferred climatic change with increasing alti- Preservation of Tertiary section 192 tude 190

Geological Society of America Bulletin, v. 73, p. 183-198, 2 figs., February 1962 183

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paleotemperatures for the marine Miocene of INTRODUCTION central California. The amount of post-Pliocene uplift of the Sierra Nevada has been estimated recently by YOSEMITE REGION two different methods. Following Matthes' (1930) approach, Hudson (1960) recalculated Introductory Remarks the gradients of the Merced and American Hudson's estimate of 3930-feet uplift in the rivers during the Broad Valley stage. Com- Yosemite region following the Broad Valley parison with the gradients of the modern stage is only 70 feet less than that indicated by streams led him to conclude that after the fossil floras in the eastern part of the region Broad Valley stage the summit of the range (Axelrod and Ting, 1960a). His doubt as to the increased its altitude approximately 4000 feet value of paleobotanic and paleoclimatic evi- in the Yosemite region and about 2000 feet in dence as an indicator of ancient topography the Lake Tahoe area 135 miles north. Taken results from the fact that his conclusion does in conjunction with his earlier work dealing not agree with that reached in an early study with the gradients of Eocene streams (Hudson, (Axelrod, 1957a) which suggested that the 1955), he concluded that the Sierra Nevada Sierra Nevada probably was uplifted on the had an altitude of approximately 9000 feet in order of 6000-8000 feet since the Tertiary. The the Yosemite area and about 5000 feet in the discrepancy exists because Hudson used a dif- Tahoe sector, from the Eocene to the Pleisto- ferent erosion surface from that I used as a cene. He notes (Hudson, 1960, p. 1571) that datum plane from which to measure the dis- these conclusions differ substantially from those placement. based on paleobotanical evidence provided by Tertiary floras in the Sierra Nevada and ad- Erosion Surfaces for Determining Uplift jacent areas to the east and west (Axelrod, The amount of post-Pliocene uplift in the 1957a; Axelrod, 1957B). His estimates also dif- range can be determined from either of the two fer from those derived from more recent studies major erosion surfaces (Table 1). These surfaces of the late Pliocene (Axelrod and Ting, 1960a) are best preserved on the Kern Plateau south and (Axelrod and Ting, 1961) of Mount Whitney (Fig. 1A), an area that was floras from the Sierra Nevada. largely nonglaciated. Lawson (1904) first de- The writer believes it appropriate to review scribed and named them the Subsummit the problem of the post-Pliocene, and also the plateau and High Valley surface. The Sub- Tertiary, altitude of the range, because, con- summit plateau is separated from the High trary to Hudson's statement (p. 1571), the Valley by 2500 feet of relief that represents conclusions reached from paleobotanical evi- approximately the amount of initial uplift in dence do not differ wholly from those he in- that region. The High Valley is trenched 3000 ferred. Since we are in agreement as to the feet by the canyon of the Kern River, which amount of post-Broad Valley uplift following reflects the second major period of uplift1. the Early Pleistocene in the Yosemite region Knopf (1918) added materially to our under- but do differ substantially in our estimates of standing of their geomorphic and structural re- uplift in the Lake Tahoe sector (Granite Chief, lations, and Matthes (1950b) renamed these Donner Summit), these areas are discussed ancient landscapes the Boreal (Subsummit) and separately. Chagoopa (High Valley). The Boreal and Chagoopa surfaces have been ACKNOWLEDGMENTS traced into the Yosemite region. Knopf (1918) Many of the new data summarized here followed them from the Kern Plateau north- come from current studies of the late Cenozoic microfossil floras of California and the Tertiary 1 This includes both the Mountain Valley and Canyon floras of Nevada, research projects that have stages of the Yosemite and San Joaquin areas. The been generously supported by the National Mountain Valley stage, which is also represented in the Kern River Canyon area, appears to be no more than an Science Foundation. initial cycle in the development of the Canyon stage. For their careful and thoughtful appraisal Its age is not precisely known, but it is approximately of the manuscript, I am indebted to Cordell mid-Pleistocene, not Pliocene as Matthes supposed. Durrell and William C. Putnam. Thanks are Work currently under way in the San Joaquin basin also due Clarence A. Hall, Jr., for the revised should provide a more precise date.

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ward for 90 miles into the High Sierra near Bishop where they are also separated by 2500 feet. In the region on the windward side of the range, 20-30 miles west, Birrnan (1956, unpub. Ph.D. thesis, Univ. California, Los Angeles) recognized three similar geomorphic (unnamed) features: remnants of a high upland surface, a rolling middle plateau region 2500-3000 feet lower in altitude, and the canyon of the San Joaquin River that deeply trenches the latter. He notes that a few remnants of the high up- land surface are covered with basalt and that the intermediate plateau region is locally k 6 = 9 blanketed by a younger basalt. Closely similar -5 -d 8 8 relations are displayed in the area 30 miles u $3 8 .z 0 3 s 0 w north, in the upper San Joaquin River basin at =:. - S -2 0, zz ffi 28-5 2 Boreal

Figure 1. Topographic relations of erosion sur- faces in the Sierra Nevada. (A) Kern Plateau region (after Matthes 1950b). (B) Yosemite-San Joaquin River region (adapted from Matthes, 1960)

the southeast corner of Yosemite National Park (Erwin, 1934). In a posthumous paper, Matthes (1960) not only identifies two major upland surfaces in the San Joaquin River basin, he confidently correlates them with the two oldest cycles in the Yosemite region (Matthes, 1930)-the "Eocene" and Broad Valley (Fig. 1B). He also traced them onto the east slope of the range near Bishop, where Knopf (1918) had previously identified them as the Sub- summit ( = "Eocene," =Boreal) and High Valley ( =Broad Valley, = Chagoopa) surfaces that are so well displayed on the Kern Plateau (Fig. 1A; Table 1). Ages of Erosion Su&es The ages of these surfaces have long been in doubt because they are carved chiefly across pre-Tertiary granitic and metamorphic rocks. The Boreal has been considered Cretaceous and Eocene, the Chagoopa as Miocene, Pliocene,

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and (Table 1). The oldest surface (1959). This conclusion is supported by the age that Matthes recognized in the Yosemite re- of three fossil floras recovered recently from gion, which he referred to an "Eocene" cycle lake beds on the Chagoopa surface. They repre- of erosion, is represented by isolated benches sent a conifer forest similar to that now making and relict summits in the higher parts of the up the ecotone between yellow pine and fir range and in the uplands bordering Yosemite forests in the southern Cascades of Oregon, and Valley (Matthes, 1930, Figs. 9-11). It repre- which survives under a moist, cool temperate sents the Boreal surface (=Subsummit) be- climate. These floras lived during the McGee- cause it can be traced into the summit region Glacier Point glacial stage, which appears to farther east, and thence southward. Sedimen- be contemporaneous with the Kansan of the tary rocks associated with the oldest basalt that central United States (Axelrod and Ting, locally covers this surface at an altitude of 1960a; 1960b; 1961). 10,000 feet in the summit area near San Joaquin Mountain have yielded a late Pliocene Total Uplift flora (Axelrod and Ting, 1960a).2 Amount. The datum plane for comparing Matthes termed the succeeding geomorphic Hudson's estimate of the amount of post- events the Broad Valley, Mountain Valley, and Pliocene uplift in the Yosemite area with that Canyon stages, considered by him as Miocene, inferred from paleobotanical evidence is the Pliocene, and earliest Quaternary, respec- Broad Valley surface in the Yosemite region tively.3 The Broad Valley stage, which Hudson and the corresponding Chagoopa surface in the used as a datum for measuring uplift, corre- range to the south and east. Paleobotanical sponds to the Chagoopa stage in the southern evidence suggests that in the Yosemite region Sierra Nevada. Hudson (1960, p. 1555) prop- the Broad Valley surface was uplifted ap- erly notes that this is an early Pleistocene—not proximately 4000 feet (Axelrod and Ting, a Miocene—surface. He shows that, contrary 1960a); Hudson's estimate is 3930 feet. to Matthes' belief, the surface does not under- Whereas Hudson confined his estimate to lie the fossiliferous upper Miocene andesitic movement since the Broad Valley stage, Axel- sediments at Tuolumne Table Mountain, but rod (1957a; Axelrod and Ting, 1960a) cal- truncates the Miocene and Pliocene volcanic culated the altitude of the late Pliocene Boreal rocks in the central to northern part of the surface and the amount of subsequent uplift. range. Hudson dates the surface as early This accounts for the apparent discrepancy in Pleistocene on the basis of its relations to our figures for total post-Pliocene uplift. Evi- formations of approximately this age in the dence provided by the late Pliocene San lower foothill belt described by Davis and Hall Joaquin Mountain flora, now at an altitude of 10,000 feet in the eastern Yosemite region, 2 The report on the late Pliocene floras east of the shows that the crest could not have had a pre- Sierra Nevada (Axelrod and Ting, 1960a) includes an Broad Valley altitude of 9000 feet, as Hudson error in terms of the erosion surfaces and their correla- maintains. The flora is preserved on the Boreal tion. The Boreal surface of the southern Sierra Nevada surface and represents a middle altitude, yellow corresponds to Matthes' unnamed "Eocene" surface in pine forest. Clearly, if the area stood at 9000 the Yosemite region, not to the Broad Valley stage. feet, species representing subalpine forests and Similarly, the Chagoopa of the southern Sierra cor- responds to the Broad Valley stage of the Yosemite-San arctic-alpine meadows would have dominated Joaquin region, not to the Mountain Valley stage the flora. Thus, owing to rejuvenation, which (Table 1). elevated the Boreal ("Eocene") surface 2500- The error stems from the fact that the basalt at San 3000 feet at the close of the Pliocene and/or Joaquin Mountain is not on the Broad Valley surface, in the earliest Pleistocene, accelerated erosion as both Matthes and Erwin report. It lies on the older carved the Broad Valley surface. Hence the Boreal ("Eocene") surface which has been down- total post-Pliocene uplift in the high Yosemite dropped on a north-trending fault that traverses the region is approximately 6500-7000 feet. 4000 west side of San Joaquin Mountain to give the illusion feet (Hudson's 3930 feet) applies only to up- that it is on the Broad Valley surface which is well exposed across the valley (Axelrod and Ting, 1960a, lift following the Broad Valley stage. PI. 2). Evidence in Mount Whitney region. These ^ Since the Mountain Valley and Canyon stages are results agree with conclusions reached from cur- not directly involved with the problem of determining rent studies in the Mount Whitney region, the amount of post-Broad Valley uplift, they are not which also indicate that uplift increased south discussed here. of the Yosemite sector. Spore-pollen floras pre-

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served in deposits of several old lake basins on of 11,000 feet, it would support patches of the Chagoopa surface on the Kern Plateau at subalpine forest and arctic-alpine meadows. altitudes of 6100-9000 feet are dominated by Late Pliocene floras occur in sediments at lo- trees that make up the yellow pine and fir calities (Owens Gorge, Haiwee, Darwin Sum- forests in northern California and adjacent mit) close to the crest of the presumed arch, Oregon (Axelrod and Ting, 1960b; 1961) which and early Pleistocene floras are known from are typically found in a moist, cool-temperate sites (Alabama Hills, Little Lake) high on the climate. Floras recovered from sediments on upper flanks of the hypothetical arch. The late the granitic basement at Alabama Hills and Pliocene floras represent yellow pine forests Little Lake at the base of the Sierran scarp in typical of a mild-temperate climate of middle southern Owens Valley, and now at altitudes altitudes, the early Pleistocene represent forests of 3500-4000 feet, are similar to those on the typical of a cool-temperate climate like that of Kern Plateau. Clearly, at the time of deposition the transition from yellow pine to fir forests. the floras now in Owens Valley must have had Obviously there has been no upwarp such as essentially the same altitude as those on the Matthes visualized, and Owens Valley is not Kern Plateau: all of them represent vegetation the collapsed crest of a regional anticline. like that now found in the transition from Two other lines of evidence are also incon- yellow pine to fir forests. The erosion surface sistent with Matthes' interpretation: (1) on which the sediments rest in the graben at Hopper (1947, p. 430) showed that, if a great Alabama Hills and at Little Lake must, there- regional anticline existed, deep canyons would fore, be the displaced counterpart of that have scoured its east flank. They would be which is now stranded locally at the top of the represented today by deep canyons, glaciated Sierran scarp, and which extends across the in their upper part and extending from the summit divide as the Chagoopa surface. Since east flanks of the White-Inyo Mountains across Chagoopa surface floras are of McGee age the summit of the range, and there would be (=Kansan), post-Kansan displacement on the clear evidence that they had extended farther scarp below Mount Whitney is approximately west but had been truncated at the site of the 6000 feet. An additional 2500-3000-foot dis- collapsed arch. Canyons of this sort are not placement in the Pliocene-Pleistocene transi- present, and the small glaciated valleys in the tion accounts for uplift of the higher Boreal high White Mountains have cirques that head landscape. Thus, the total post-Pliocene dis- on the east slope. (2) Rapid uplift of the placement at Mount Whitney is approximately Sierra Nevada of 6000 feet at the close of the 9000 feet. To judge from the nature of the Pliocene, as suggested by Matthes, would in- floras, Alabama Hills remained relatively sta- troduce much colder water into the shallow tionary with respect to the Sierran front which San Joaquin marine embayment at the west has been displaced upward. At Little Lake, 40 base of the range; this probably would be re- miles south, post-Kansan displacement is about flected by an increase in cool-water forms in 3000 feet, and total post-Pliocene uplift is ap- the late Pliocene marine fauna. Actually, the proximately 5500 feet (Axelrod and Ting, faunas record a rise in temperature at this time 1961). (Durham, 1950). Matthes' Sierran upwarp. The late Pliocene and early Pleistocene microfossil floras (Axelrod LAKE TAHOE REGION and Ting, 1960a; 1961) provide ample evidence to show that Matthes' ideas with respect to the Introductory Remarks nature and amount of deformation are un- Hudson calculates that uplift at Granite tenable. Matthes (1950a, p. 48-50, Fig. 3) Chief, west of the north end of Lake Tahoe, thought that at the close of the Pliocene the was approximately 2000 feet; this gives a Sierra Nevada was deformed into a great arch, pretilt height of about 7000 feet as compared encompassing the neighboring ranges (Inyo with 9000 feet today. This estimate agrees Mountains, White Mountains) to the east. The generally with his earlier result at Donner crest of the arch at that time had altitudes near Summit, 8 miles north (Hudson, 1955) as cal- 11,000 feet, which he thought was sufficient for culated from stream profiles of the Eocene glaciation. He imagined that the crest col- Yuba River, which gives a pretilt altitude of lapsed during the Pleistocene to form Owens approximately 5000 feet as compared with 7000 Valley and related grabens at the east base of today. By contrast, paleobotanical evidence the Sierra. If the summit region had altitudes suggests that uplift was from two to nearly

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three times greater (Axelrod, 1956; 1957a)— central and northern Sierran summit region uplift at Donner Summit is estimated at ap- represent communities similar to those that proximately 5000 feet, and at Carson Pass, 45 contribute now to the lower deciduous hard- miles south, it is near 7000 feet. Prior to out- wood forest zones in the eastern United States lining two independent and wholly adequate and eastern Asia, the fossil floras presumably bases for testing these divergent results, it is had generally similar altitudinal relations. None necessary to summarize some new paleobotanic of these floras includes montane conifers, as and paleoclimatic evidence that reinforces the might be expected if the sites of deposition earlier inference of only a low topographic were at high altitudes or even moderately high barrier. ones. This agrees with the regional relations of the Sierran floras to Miocene floras of the Co- Paleobotanic Evidence for Low Relief lumbia Plateau and northern Great Basin. The Fossil and related modern forests. The later floras that are dominated by deciduous hard- Miocene floras of the central to northern high woods lived in lowland areas, chiefly within Sierra Nevada are dominated by mild-tem- 1000 feet of sea level. Those that include mod- perate, deciduous hardwoods and a few warm- erate numbers of montane conifers associated temperate evergreens. For example, the Mo- with the dominant hardwoods occurred at hawk flora (alt. 4500 feet), at the east base of moderately higher levels, chiefly below 3000 the north Sierran crest, includes species of feet (Chaney and Axelrod, 1959). magnolia (Magnolia), avocado (Persea), hickory Altitudinal belt's of vegetation. If the Mio- (Garya), sweetgum (Liquidambar), black oak cene Sierra Nevada had been high, then several (Quercus), madrone (Arbutus), and rattan vine different forest belts would have occupied its (Berchemia). The Carson Pass flora (alt. 9100 slopes much as they do at present, changing ft.), on the summit at timberline, has swamp their composition in response to cooler climate cottonwood (Populus), lingnut (Pterocarya), at higher altitudes. Floras in the summit sec- sweetgum (Liquidambar), avocado (Persea), tion would thus differ considerably from those persimmon (Diospyros), sourgum (Nyssa) and on the lower piedmont. sycamore (Platanus). The Ebbets Pass flora The Denton Creek flora, collected by Prof. (alt. 8250 ft.), from a region of subalpine forest, Cordell Durrell from the Mohawk graben 40 is dominated by avocado (Persea). The Niagara miles northwest of Lake Tahoe, occurs at an Creek flora (alt. 7000 ft.), at the lower margin altitude of 5200 feet. It is very similar to the of the fir forest west of Sonora Pass, contains Table Mountain flora (Condit, 1944) from the swamp cypress (Taxodiuni), swamp cotton- foothill belt 150 miles south, which is now at wood (Populus), magnolia (Magnolia), sweet an altitude of 2200 feet but then lived within gum (Liquidambar), birch (Betula), and lingnut 500 feet of sea level. Both floras are dominated (Pterocarya). The species in these floras find by the same species of oak, hickory, and elm, their nearest modern relatives in the tem- and there are several other species in common, perate parts of the eastern United States and including mountain mahogany (Cercocarpus), eastern Asia. These regions, characterized by avocado (Persea), and maple (Acer). Woodland ample rainfall distributed throughout the , and chaparral plants are less common at Denton are great refuges for the Arcto-Tertiary Geo- Creek, and the Denton Creek has some plants flora that migrated slowly southward across (Liquidambar, Diospyros, Prunus) that are not Holarctica during the Tertiary, as recognized now known at Table Mountain. Such differ- by Asa Gray nearly a century ago. Plants in ences are to be expected in view of the position the deciduous forests of the lower piedmont of Denton Creek flora farther north at a slightly and foothill belt of the Appalachian Mountains higher (ca. 500 feet) altitude. The floras are show considerable relationship to the Miocene sufficiently similar to indicate that they repre- floras of the Sierra Nevada, as do the very sent essentially the same vegetation zone; similar and closely related forests of central therefore, they must have lived at nearly the Japan and Korea. In both regions montane same altitude. Obviously, if the Sierra Nevada conifers become increasingly common at alti- had had considerable altitude at the close of tudes near 2500-3000 feet and form mixed the Miocene, the climatic differences between coniferous-deciduous forests at middle alti- its upper and lower parts would have resulted tudes. At levels near 4500 to 5000 feet they in totally different floras at Denton Creek and are replaced by subalpine forests of fir and Table Mountain. spruce. Since the Miocene floras from the This paleobotanic evidence for only low

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altitude in the northern part of the range is to Niagara Creek, now at 7000 feet. The well- consistent with the geologic relations. Durrell's drained coastal plain and rolling hills in the (1959) detailed study of the Tertiary strati- lower Blue Ridge region have forests largely graphy of the Blairsden quadrangle northwest dominated by deciduous hardwoods, but with of Lake Tahoe shows that the region was es- a sprinkling of warm-temperate trees, such as sentially a peneplain during the , persimmon, magnolia, and avocado. These Miocene, and Pliocene, because continuous forests resemble those that have been recovered sheets of volcanic and sedimentary rocks were from the San Pablo localities in west-central deposited across the site of the present range. California and from the foothill belt to the The stratigraphic and structural relations of very summit of the Miocene Sierra Nevada. the Tertiary rocks indicate that the present re- Important changes take place with increasing lief is due to faulting that followed extravasa- altitude in the Blue Ridge. They owe not so tion of the Warner Basalt, which is no older much to the increased precipitation, but to the than late Pliocene. Such a recent date for the 3.6°F. decrease in temperature that occurs northern part of the topographic barrier is con- with each additional 1000 feet of altitude.4 sistent with evidence southward in the range. The change is reflected in the appearance of Regional climatic pattern. The paleoclimatic mixed coniferous-deciduous hardwood forests indications of Miocene floras can be determined from 2000 to 4500 feet and by their replace- rather accurately because the fossil plants are ment at higher levels by subalpine forests and similar to species that make up present-day associated communities; neither the mixed communities whose climatic requirements are forests nor the subalpine forests have counter- known. As shown earlier (Axelrod, 1957a, p. parts in the Miocene Sierra Nevada. Clearly, 37, Fig. 5), if the rainfall estimates for the not much more than 2000 feet could have Miocene floras of the region are plotted on a separated the Miocene floras at sea level from map, the regional pattern of isohyets is con- those in the Sierran summit region. Otherwise, sistent with generally low relief. the temperature change accompanying higher A further basis for interpreting regional altitude would result in forests differing as climate and altitude in the Miocene Sierra is widely in composition as the forests in the provided by a comparison of the Miocene middle and upper Blue Ridge differ from those floras with a transect from coastal Carolina into in the surrounding lowlands which resemble the Blue Ridge. Many of the Miocene Sierran the Miocene floras from coast-central California fossil plants have their nearest counterparts and the Sierran summit region. The fact that living there, and the region has a precipitation all the Miocene floras represent deciduous regime much like that inferred for central hardwood forests with warm-temperate ever- California. Further, the crest of the Blue Ridge greens obviously means that they have gener- stands at 5000-7000 feet, which is the altitude ally similar temperature requirements; they postulated by Hudson for the Sierra Nevada could not have been widely separated in in the Lake Tahoe region during the Miocene. altitude. In the Carolina-Blue Ridge area, rainfall in- creases from 45-50 inches along the coast and Tests for Plausibility of Results low coastal plain to near 60 inches in the lower Marine paleotemperatures. Miocene sea- foothill belt and rises to 80 inches in the higher surface temperatures, as inferred from shallow- parts of the range. Temperature shows a water molluscan faunas, provide an independ- corresponding gradient in response to in- ent means for calculating the decrease in creasing altitude; summers are cooler and temperature with increasing altitude on land winters colder at higher levels. Vegetation in areas immediately adjacent to the sea and, responds to these changes and exhibits a hence, for determining the nature of climate striking similarity to the Miocene of California along the Sierran crest at any postulated from the coast into the Sierra Nevada. In the altitude. If the Sierra Nevada was generally east, swamp cypress (Taxodium) forests extend low, as suggested by the fossil floras, a rather from the coast inland to generally low altitudes. mild climate would have typified the summit This parallels the Taxodium community repre- sented in the San Pablo flora (Condit, 1938) 4 This is a normal lapse rate, and it is also thought to that lived near the shore (Loma Ranch florule) have been present in California during Miocene time in west-central California and extended inland owing to the much weakened subtropical high-pressure (Corral Hollow florule) into the Sierra Nevada system.

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section. However, if the range was high, as shallow-water molluscan faunas preserved in indicated by reconstructions of ancient stream the marine section suggest by analogy with profiles, more extreme conditions would have living forms that sea-surface temperature was prevailed. approximately 66.2°F. (19°C.) in summer and A shallow sea occupied much of the area of 59°F. (15°C.) in winter (Hall, 1960; also oral coastal California south of the San Francisco communication)—estimates that agree closely Bay region and also the San Joaquin Valley with those inferred from the warm-temperate during late Miocene (Cierbo-Neroly). The character of the fossil floras in the same section. Coast Ranges had not yet been elevated to In utilizing these temperature values for form a major climatic barrier, and the Sierran estimating conditions along the Sierran sum- piedmont graded west to the strand. The mit, it must be recalled that summer climate

TABLE 2. LATE MIOCENE SEA-SURFACE TEMPERATURE AND INFERRED CLIMATIC CHANCE WITH INCREASING ALTITUDE Summer Winter Effective ET of Climate Altitude (feet) temp. (F.°) temp. (F.°) temp. (ET)* boundary

warm temperate — s.l. 66.2 59.0 60.8 59.9 = 375 ft.

mild temperate — 1000 66.2 55.4 58.4

59.0 51.8 56.1 - 2000 ft.

cool temperate — 3000 55.4 48.2 53.7 52.8 = 3375 ft.

subalpine — 4000 51.8 44.6 51.3

50.0 - 4920 ft. — 5000 48.2 41.0 48.8 tundra — 6000 44.6 37.4 46.4 45.4 = 6375 ft.

— 7000 41.0 33.8 44.0

polar — 8000 37.4 30.2 41.6

9000 33.8 26.2 39.0 * Effective temperature "measures warmth by denning a sliding scale specifying temperatures at the beginning and end of a warm period, and the duration of that period. The double relation between temperature and time fol- lows from the proportional weighting that has been given to summer and winter temperature, thus incorporating the principle of seasonal rather than annual warmth (Bailey, 1961)."

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in this region is now controlled by a great sub- precipitation would occur on the leeward side tropical high-pressure system. Not only does it of a high range than on the windward; con- create clear skies and abundant sunshine, but versely, a low range would not greatly affect descending air—abiabatically warmed—pre- the trend toward decreased precipitation to vents the decrease in temperature that nor- leeward. The rainfall indications of the late mally occurs with altitude. The lapse rate in Tertiary floras in western California and west- this region is approximately 2°F. per 1000 feet ern Nevada are shown in Figure 2; for a today; this results in the displacement of discussion of their composition, paleoecology, forests to higher altitudes than might other- climatic indications, and age, see Axelrod wise be necessary to support them. During the (1944a; 1944b; 1944c; 1944d; 1950; 1956; Miocene the high-pressure system was greatly 1957a; 1957b), Axelrod and Ting (1960a), and weakened, thus allowing ample summer precipi- Condit (1938). tation and with it convectional cooling creating a normal lapse rate from sea level upward. Using a normal temperature decrease of 3.6°F. WESTERN NEVADA per 1000 feet, it is possible to calculate the temperature at any altitude on the seaward slope of the central Sierra Nevada during the late Miocene (Table 2). The data show that mild-temperate climates ranged upward to altitudes near 2000 feet; cold-temperate climate was between 2000-3375 feet; subalpine from 3375-4920 feet; tundra late I early I middle! late from 4920-6375 feet, and polar climate existed Miocene | Pliocene

above 6375 feet. Clearly, if the north-central WESTERN CALIFORNIA part of the range had an altitude of 7000 feet iNeroly during the Miocene, as Hudson suggests, there would be no forests in the summit section. However, as we have seen, Miocene floras of mild-temperate aspect grew in the crestal areas north (Mohawk flora) and south (Carson Pass flora) of the Lake Tahoe region and also nearly to the Yosemite area (Ebbets Pass flora, Niagara Creek flora) where the range was at late early I middle I late 9000 feet according to estimates from recon- Miocene Pliocene structed stream profiles. The altitudinal rela- Figure 2. Comparison of rainfall trend on op- tions of climate, as inferred from sea-surface posite sides of the Sierran axis during the later Tertiary. Vertical bars represent, within 5 temperatures, thus agree closely with those inches, average precipitation indicated by floras deduced earlier from paleobotanical evidence (from Axelrod and Ting, 1960a) (Axelrod, 1957a), and is supported by discov- eries of three new floras (Denton Creek, Ebbets Pass, Niagara Creek) in the summit area. These There was a steady and continuous decrease floras must have occurred at altitudes of not in precipitation on both the leeward and wind- much greater than 2000 feet, because they lived ward sides of the Sierra Nevada into the under mild-temperate, not subalpine, tundra, middle Pliocene, the driest part of the Tertiary or polar climate. (Axelrod, 1948). More significantly, there was No rain shadow, no high relief. The high a marked increase in rainfall in each region Sierran barrier that Hudson postulates for the during the late Pliocene, as shown by the later Tertiary should be detectable by compar- change from live oak woodland to yellow pine ing the rainfall indications of sequences of forests. The essentially identical precipitation floras on opposite sides of the range. Since the trend recorded by sequences of floras on oppo- subtropical high-pressure system was strength- site sides of the Sierra Nevada from late ening during this interval, rainfall was gradually Miocene into late Pliocene seems to demand lessening and becoming more seasonally dis- only low relief. If the Sierra Nevada had an tributed. During a given interval of time, altitude of approximately 9000 feet in the therefore, an increasingly greater decrease in Yosemite area and 7000 feet in the Lake Tahoe

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sector, as Hudson suggests, there would have the Tertiary, however, much of the section been important differences in rainfall and, would be preserved—and it is. hence, in vegetation on the leeward and wind- ward sides during the later Tertiary at least. Formations Deposited Across Summit Area The differences that do exist between the floras In the Blairsden quadrangle of the northern of the regions seem explicable by a low barrier Sierra Nevada, Durrell (1959) has demon- and by differences in altitude between the strated that five Tertiary formations were western floras near sea level and those on the deposited as nearly continuous sheets across low Nevada plateau. the present summit section of the range, that each was separated by periods of faulting and HIGH TERTIARY RELIEF MAKES erosion, and that each was deposited on a nearly GEOLOGIC PROBLEMS level surface. Deformation that accounts for the present relief followed extravasation of the Introductory Remarks Warner Basalt, which appears to be late Plio- The belief that high relief has existed along cene. the Sierran axis since Eocene time is not con- Warner Basalt not only covers lower Pliocene sistent with geologic evidence that points to andesite in the Truckee basin and areas to the its recent elevation by faulting and warping. east but covers also the west flank of the Sierra Readers of some of the following remarks may Nevada north and south of Donner Summit; well reply that movement is only relative, and it apparently was extruded as a sheet across the that the examples do not demonstrate the region. From Donner Pass eastward to the absolute sense of movement on the Sierran lower end of Donner Lake (6 miles), fully 3100 block. In my opinion, such an argument is feet of structural relief developed following invalid: the fossil floras are composed of plants extravasation of the basalt (Daley and Poole, closely similar to those making up modern 1949, unpub. MA thesis, Univ. California, Los communities whose climatic and topographic Angeles). relations provide a sound basis for reconstruct- In the high Yosemite sector upper Pliocene ing altitude during the later Cenozoic. As basalt flowed west across the present summit summarized above, paleobotanic and paleo- of the range (Erwin, 1934), an event not climatic data have established several datum compatible with high relief. The fossil micro- planes (altitudes) at different times which flora recovered from sediments interbedded demonstrate that the Sierran block moved with the lower basalt flows provides evidence upward at the close of the Tertiary, not only for only moderate altitude, as the flora repre- relatively with respect to the regions at the sents a humid yellow-pine forest. By contrast, east and west, but absolutely with respect to the site now is at 10,000 feet in an area of them and to sea level. subalpine forest (Axelrod and Ting, 1960a). Preservation of Tertiary Section Origin of Scarps Postulated high relief for the Sierra Nevada The belief that the Sierran crest stood near is inconsistent with the persistence of its 9000 feet in the Yosemite sector (and presuma- Tertiary cover of rather poorly indurated bly higher southward) and close to 7000 feet sedimentary and volcanic rocks. To maintain in the Lake Tahoe sector (Granite Chief) is at a range with altitudes from 9000 feet in the variance with the scarps on the east front that Yosemite area (and presumably higher south- tower 4000-6000 feet (at the south) above the ward) to 7000 feet in the Lake Tahoe sector grabens at the base of the range. Obviously, during an extended period (-Plio- the scarps have not been in existence since the cene) of warm climate characterized by rapid, early Tertiary, for they soon would have been deep-chemical weathering and heavy rainfall worn down. Nor can they be due to the collapse well distributed through the year would require of a great arch that extended east to encompass continued uplift to offset the effects of erosion. part (or all) of the Great Basin. Fossil plants, Under such conditions, to judge from known fish, mammals, and fresh-water invertebrates and inferred rates of erosion, the Tertiary cover all indicate only low to moderate relief for the would be quickly stripped from a high range region. This is true not only of the re- of the sort Hudson reconstructs. With generally covered from basins well to the east of the low relief and moderate tectonic activity during Sierra Nevada but also of those collected from

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sites along the axes of presumed upwarps such now occur on the Sierran block and in the as Owens Valley. The scarps are Pleistocene in Owens trough, post-Pliocene uplift at Mount age, and major movement has occurred on Whitney is on the order of 9000 feet, of which several occasions. 6000 feet is post-Kansan (Axelrod and Ting, 1960b; 1961). Displacement on Scarps In the Carson Range east of Lake Tahoe, UPLIFT FROM STREAM PROFILES lower Pliocene andesite has been displaced from near 5300 feet in Washoe Valley to Introductory Remarks 10,000 feet on Mount Rose (Gianella, 1933, The question may be raised as to whether p. 115, Fig. 19). Along the same scarp 35 miles the method utilized by Hudson (1955; 1960) south, a small patch of andesite at 10,600 feet is wholly adequate to indicate the altitude of on Jobs Peak finds its counterpart in Carson the Sierra Nevada during different stages in Valley at 5000 feet. Movement is post-late its history. It is based (Hudson, 1960, p. 1557) Pliocene. . . . "on the assumption that certain evenly The scarp of the Sierra Nevada west of Lake graded stretches of the Broad valley channel Tahoe extends from Granite Chief (alt. 9008 had pretilt gradients equal to those of the feet) southward to near Pyramid Peak (alt. smooth, subjacent parts of the modern stream. 10,020 feet). Post-late Pliocene displacement This will seem unwarranted to those who may has been on the order of 4000 feet at the north regard the present Merced as a poorly graded to 5000 feet at the south. river and accept Matthes' idea (1930, p. 44) Late Eocene auriferous gravels deposited in that the Broad valley channel was 'well graded.' a river channel fully 3 miles broad are truncated . . . The modern channel appears to be no less on the Honey Lake scarp south of Susanville. 'well graded' than the Broad valley channel; The 2500-foot scarp is post-Pliocene, for it the writer believes that part of it is better developed after upper Pliocene Warner Basalt graded than the ancient stream. Below Merced erupted over a nearly peneplaned surface. Falls (alt. 350 ft.) the present stream, in its Eocene auriferous gravels are truncated at course across the Tertiary belt, is flanked by an altitude of near 9000 feet in the Carson terraces whose gradients are essentially the Range and reappear to the east in the Virginia same as the adjacent parts of the river. This Range, several thousand feet lower (Gianella, according to Woodford (1951, p. 816) is a 1933, p. 113, Fig. 18; 1936). Displacement is criterion for a graded stream." post-basalt (late Pliocene). At McGee Mountain near Mammoth, Cali- Graded Rivers fornia, McGee till ( = Kansan) and the upper If the Merced is a graded stream so then is Pliocene basalt on which it rests have been nearly every other river in the world, and the displaced 4000 feet, and possibly more, as the existence of river-terrace deposits in their displaced section lies in Long Valley under a lower stretches provides no indication of the cover of Quaternary sedimentary and volcanic gradient of the stream in its source areas nor no rocks of unknown thickness (Putnam, 1960). indication of relief in the region. Terrace The position of the basalt on the Boreal surface deposits border rivers in areas of essentially no suggests that displacement here has been about relief (Mississippi River), in areas of low to 6500 feet since late Pliocene. moderate relief (Salinas River), in areas of high At Coyote Ridge, a few miles southwest of relief (Merced River), and in areas of extreme Bishop, the Chagoopa surface is covered with relief (Brahamaputra River). The crucial point the most extensive area of McGee till now is not whether a river has reached grade in its known in the range. The surface, till-covered lower reaches but the gradients (slope) of the in its middle and higher parts, has been up- stream in the middle and upper mountain warped at least 5500 feet—from 4500 feet on sections. In such areas the Merced and other the floor of Owens Valley at Bishop Creek to Sierran rivers now occupy the entire floor of the 10,000 feet at Coyote Flat. great V gorges they have excavated. Deposits Fossil microfloras are preserved in sediments throughout their channels are of only the that cover the old erosion surfaces in the south- coarsest sort except for occasional small tran- ern part of the range. Judging from the displace- sient sand bars on the river bends. These rivers ment of essentially identical forest zones which deposit only fine materials well out in front

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of the range, chiefly in areas below 400-500 down moderate gradients at times of very high feet in altitude. Where such rivers as the discharge by torrential flooding from regularly Stanislaus (below Knights Ferry), Tuolumne recurring heavy tropical storms that swept over (at Le Grand), and Merced (at Merced Falls) the Eocene Sierra Nevada. leave the Sierran basement section, they have The finely laminated ashy Miocene clays at deposited river terraces considerably coarser Mohawk (alt. 4500 feet), Indian Diggings (alt. (regularly large-boulder conglomerate) than 3300 feet), and Remington Hill (alt. 3800 feet) the Eocene (lone), Miocene (Valley Springs), and the nearly varved clays and associated fine Pliocene (Mehrten), and Pleistocene (Turlock sands at Table Mountain (alt. 2200 feet) Lake; Riverbank; Modesto) formations on obviously were not laid down by rivers with which they rest. The gradients of these recent gradients approaching those of the present terraces are essentially the same as the adjacent Sierran streams; the late Miocene rivers proba- parts of the rivers, as Hudson states, but the bly were near grade at sites that are now well modern streams obviously have a much steeper up in the present range. This is suggested by gradient than the Tertiary rivers. the Niagara Creek section (alt. 7000 feet), The Tertiary rivers not only deposited finer composed of well-sorted, cross-bedded river material at the base of the range than do the sands and gravel beds. Fifteen miles west the modern streams, they flowed in broader valleys section is chiefly silty sand and silty clay—here and deposited well-sorted sand, silt, and pebble it is as fine as the finer deposits represented in beds at sites that are now well up in the present the Pleistocene section well out in front of the range, and even at its summit. For example, the Sierra, in the Riverbank and Turlock Lake Eocene deposits were laid down by large rivers, formations, for example (Davis and Hall, some of which drained across the Sierran axis 1959). The Miocene sediments deposited at at various points. The river channels are com- sites now high up in the range obviously are monly up to a mile wide; the modern streams very different from those in the present Stanis- are not more than a few tens of yards wide. The laus River near Niagara Creek; there its bed most extensively preserved deposit, on the is a nearly impassable giant-boulder jungle. scarp above Susanville, occupied a channel 3-4 By any standards, the Miocene streams must miles wide. Its sediments evidently grade west have had gradients considerably lower than into the Montgomery Creek formation (chiefly those of the present streams. We can agree with well-sorted, cross-bedded sandstone and shale) Hudson and Woodford that the Stanislaus, which was laid down on a broad flood plain not Merced, and other Sierran streams are graded far from sea level. Neither the finely laminated today because they have river-terrace deposits clays at Chalk Bluffs nor the carbonaceous along their lower courses. But this is no basis sandstones at La Porte find a counterpart in for supposing that the Tertiary river channels the deposits of the modern Sierran rivers or in had gradients approaching those of the present rivers of other mountainous regions. Sediments streams. Particle size of Tertiary sediments resembling the Eocene section of the Sierra found well up in the range is like that found Nevada are deposited regularly in areas of low in Quaternary sediments in the lowest foothill to moderate relief; the floras preserved in them belt, an area where streams have a low gradient support this conclusion. The reader may well and are at grade. raise the point that such a topography is not As for the early Pleistocene, there is good consistent with the coarse conglomerates in the reason to suggest that the ancestral Merced Eocene channels. Largely for this reason Hud- River also flowed in its Broad Valley topogra- son (1960, p. 1566) felt that the rather close phy in the Yosemite area at a lower gradient correlation between the size of the largest than did the Merced, and that it was approach- boulders in the Eocene Yuba and the modern ing grade well up in the range. This is suggested Yuba River channels supported the evidence by not only the width of the valley (15 miles for high relief suggested by reconstructed at Yosemite) and its low slopes, as Matthes stream profiles. The coarse clasts do not demand noted, but by the sediments deposited in its high relief. Some of them may well have been lower course. The cutting of the Broad Valley derived from active, low, discontinuous scarps stage can be correlated apparently with the paralleling the axis of the range, and also from deposition of the Turlock Lake Formation in steeper side valleys; Hudson (1960) notes that the lower foothill belt (Hudson, 1960). This some of the largest clasts have had local sources. formation includes some pebble conglomerate, The remainder were probably transported but most of it is sandstone, claystone, and

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siltstone. By contrast, the river-terrace deposits that cover it are chiefly boulder conglomerate CONCLUSION r^, and coarse sand. Undoubtedly, if the Merced is Paleobotanical evidence suggests that thes graded today, during the Broad Valley stage Sierra Nevada came into existence as a maj<3it it must have had a much lower gradient. topographic barrier after the close of the Thus, the deposition of fine-grained Eocene, Pliocene: (/) Miocene floras from the summit; Miocene, and Pliocene sediments found well section that are now at altitudes of 5000-90QO up in the range and the character of Pleistocene feet resemble modern forests in areas of onty1 sediments on its piedmont are consistent with low to moderate relief, chiefly less than 209$ generally low to moderate relief. Hudson's feet; (2) deciduous hardwood Miocene forests (1960, p. 1566) argument for high relief, based from the summit region are similar to those in- on the size of the largest boulders in the Eocene the foothill area, a relation that could not exist and present Yuba River channels, gives us an if relief was high and (3) late Pliocene and' index neither to gradient nor to relief. early Pleistocene floras from altitudes near 9000-10,000 feet resemble modern forests at Tertiary Tectonism only moderate altitudes today. Recent detailed mapping in the summit Paleoclimatic evidence is consistent with section of the Sierra is providing evidence that low to moderate relief until the close of the faulting occurred throughout most of the Tertiary: (7) the regional pattern of rainfall Tertiary. For example, in the Blairsden area in distribution during the Miocene and Pliocene the northern Sierra Nevada, Durrell (1959) discloses no major topographic barrier; (2) has shown that there were six major periods of the rainfall and especially the temperature faulting and erosion prior to that which ac- gradients up the windward Sierran slope during counts for the present relief (post-Warner the Miocene were not great; (3) calculations Basalt). My investigations of the complex from Miocene sea-surface temperature, as in- structure in the Tertiary section north and ferred from shallow-water molluscan faunas, south of Carson Pass show a somewhat similar show that a range of low-to-moderate relief story, with six periods of faulting and one of would have supported the mild-temperate, synclinal folding, each followed by a period of deciduous hardwood forests that are recorded considerable erosion. Whereas movements in in the summit section; and (4) the rainfall the Blairsden area occurred during the latest trend on opposite sides of the range was Eocene, Oligocene, Miocene, and Pliocene, at essentially identical during the Miocene and Carson Pass most of it was Miocene. At La- Pliocene, thus providing no evidence of the Porte there is clear evidence for an uncon- rain shadow that a high barrier would have formity in the upper Eocene section (Potbury, produced. 1935), and the older Eocene channels at Chalk Geologic evidence supports recency of up- Bluffs also record uplift during that epoch lift: (7) several Tertiary formations were (MacGinitie, 1941). No doubt there was con- deposited as continuous sheets across the siderable additional Tertiary diastrophism that northern summit section; (2) late Pliocene has not yet been discovered in the range. All basalt flowed through a seaward-draining valley of this movement must have tilted the base- that extended across the present high Yosemite ment section, as well as the Eocene stream summit area; (3) the deposition of finer-grained channels that lie on it which Hudson used to sediments throughout the Tertiary in broad measure uplift. Tilting of the Sierran block valleys not only at the base of the range, but at the close of the Pliocene (uplift of Boreal at sites well up in the range, and even at its surface) also increased the slope of the Eocene summit, seems consistent with relief much channels. These movements would give the lower than that of today; (4) the persistence channels gradients closer to those of the stream of a thick Tertiary cover of volcanic and profiles reconstructed for the Broad Valley sedimentary rocks requires low relief from stage and of the modern streams. Thus, di- Eocene to the Pleistocene; (5) there are 4000- astrophism may largely account for Hudson's 6000 foot scarps of youthful topography; and measurements that reveal a near approach of (6) truncated and warped erosion surfaces of the Eocene pretilt surface to that of modern late Pliocene and early Pleistocene ages indicate streams and, hence, account for his suggestion uplift of 5000-9000 feet. that the Sierra Nevada has been a high barrier These data do not support the suggestion since Eocene time. that the range assumed its present proportions

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because of the post-Broad Valley (=Kansan) draining across the range. The similar size of uplift of a range that had stood near 9000 feet the largest clasts in the Eocene and modern (Yosemite) and 7000 feet (Tahoe) through the Sierran rivers provides no index to gradient; Tertiary. This estimate, based chiefly on recon- transport may have been controlled by heavy structed stream profiles, may be inaccurate for floods during heavy tropical storms that gave possibly two reasons: (1) The basic assumption the rivers exceptionally high discharge. (2) that the present streams are as well graded as The initial gradients of the Tertiary stream those of the Tertiary is at variance with the channels were increased recurrently during fine-grained character of the Tertiary sediments Eocene and later epochs owing to diastrophism. from the base to the summit of the range, is at Thus, they now appear to have long profiles variance with the morphology of the stream that do not differ appreciably from those of the valleys, and is at variance with the size of the modern Sierran rivers. Tertiary channels, which in several areas were

REFERENCES CITED Axelrod, D. I., 1944a, The Black Hawk Ranch flora (California): Carnegie Inst. Washington Pub. 553, p. 91-102 1944b, The Mulholland flora (California): Carnegie Inst. Washington Pub. 553, p. 103-146 1944c, The Sonoma flora (California): Carnegie Inst. Washington Pub. 553, p. 167-206 1944d, The Pliocene sequence in central California: Carnegie Inst. Washington Pub. 553, p. 207-224 1948, Climate and evolution in western North America during Middle Pliocene time: Evolution, v. 2, p. 127-144 1950, A Sonoma florule from Napa, California: Carnegie Inst. Washington Pub. 590, p. 23-71 1956, Mio-Pliocene floras from west-central Nevada: Univ. Calif. Pub. Geol. Sci., v. 33, p. 1-322 1957a, Late Tertiary floras and the Sierra Nevadan uplift: Geol. Soc. America Bull., v. 68, p. 19-45 1957b, Paleoclimate as a measure of isostasy: Am. Jour. Sci., v. 255, p. 690-696 Axelrod, D. I., and Ting, W. S., 1960a, Late Pliocene floras east of the Sierra Nevada: Univ. Calif. Pub. Geol. Sci., v. 39, p. 1-118 1960b, Pleistocene floras from the Chagoopa surface, southern Sierra Nevada (Abstract): Geol. Soc. America Bull., v. 71, p. 1819 1961, Early Pleistocene floras from the Chagoopa surface, southern Sierra Nevada: Univ. Calif. Pub. Geol. Sci., v. 39, p. 119-194 Bailey, Harry P., 1961, A method of determining the warmth and temperateness of climate: Geografisker Annaler, v. 42, p. 1-16 Chancy, R. W., and Axelrod, D. I., 1959, Miocene floras of the Columbia Plateau: Carnegie Inst. Wash- ington Pub. 617, p. 1-237 Condit, C., 1938, The San Pablo flora of West Central California: Carnegie Inst. Washington Pub. 476, p. 217-268 1944, The Table Mountain flora (California): Carnegie Inst. Washington Pub. 553, p. 57-90 Davis, S. N., and Hall, F. R., 1959, Water quality of eastern Stanislaus and northern Merced counties, California: Stanford Univ. Pub. Geol. Sci., v. 6 (no. 1), p. 1-112 Durham, J. W., 1950, Cenozoic marine climates of the Pacific Coast: Geol. Soc. America Bull., v. 61, p. 1243-1264 Durrell, C., 1959, Tertiary stratigraphy of the Blairsden quadrangle, Plumas County, California: Univ. Calif. Pub. Geol. Sci., v. 34, p. 161-192 Erwin, H. D., 1934, Geology and mineral resources of northeastern Madera County, California: Calif. Jour. Mines Geology, v. 30, p. 7-78 Gianella, V. P., 1933, Itinerary, Reno to Walley Hot Springs and return, p. 108-116, in Middle Cali- fornia and western Nevada; 16th Internat. Geol. Cong., U. S., 1933, Guidebook 16, Excursion C-l 1936, Geology of the Silver City district and the southern portion of the Comstock Lode, Nevada: Univ. Nevada Bull. Nev. State Bur. Mines and Mackay School of Mines, v. 30, no. 9, p. 1-105 Hall, C. A., Jr., 1960, Displaced Miocene molluscan provinces along the San Andreas fault, California: Univ. Calif. Pub. Geol. Sci., v. 34, p. 281-308

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Hopper, R. H., 1947, Geologic section from the Sierra Nevada to Death Valley, California: Geol. Soc. America Bull., v. 58, p. 393-432 Hudson, F. S., 1955, Measurement of the deformation of the Sierra Nevada, California, since Middle Eocene: Geol. Soc. America Bull., v. 66, p. 835-870 1960, Post-Pliocene uplift of the Sierra Nevada, California: Geol. Soc. America Bull., v. 71, p. 1547- 1574 Knopf, A., 1918, A geologic reconnaissance of the Inyo Range and the eastern slope of the southern Sierra Nevada, California; with a section on the stratigraphy of the Inyo Range, by E. Kirk: U. S. Geological Survey Prof. Paper 110, p. 1-130 Lawson, A. C., 1904, Geomorphogeny of the upper Kern basin: Calif. Univ. Dept. Geology Bull., v. 3, p. 291-376 MacGinitie, H. D., 1941, A Middle Eocene flora from the central Sierra Nevada: Carnegie Inst. Wash- ington Pub. 534, p. 1-178 Matthes, F. E., 1930, Geologic history of the Yosemite Valley, with a chapter on the granitic rocks by F. C. Calkins: U. S. Geol. Surv. Prof. Paper 160, p. 1-137 (F. Fryxell, Editor), 1950a, The Incomparable Valley, a geologic interpretation of the Yosemite: Berkeley, Univ. Calif. Press, 160 p. (F. Fryxell, Editor), 1950b, Sequoia National Park, a geological album: Berkeley, Univ. Calif. Press, 136 p. 1960, Reconnaissance of the geomorphology and glacial geology of the San Joaquin basin, Sierra Nevada, California: U. S. Geol. Surv. Prof. Paper 329, p. 1-62 Potbury, S., 1935, The LaPorte flora of Plumas County, California: Carnegie Inst. Washington Pub. 465, p. 29-81 Putnam, W. C., 1960, Faulting and Pleistocene glaciation in the east-central Sierra Nevada of California, U. S. A.: 21st Internat. Geol. Cong. Rept., pt. 21, p. 270-274

MANUSCRIPT RECEIVED BY THE SECRETARY OF THE SOCIETY, APRIL 4, 1961

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