Amount and Timing of Late Genozoic Uplift 

and Tilt of the Central Sierra Nevada, 

California Evidence from the Upper 

San Joaquin River Basin

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1 197
Amount and Timing of Late Cenozoic Uplift 

and Tilt of the Central Sierra Nevada, 

California Evidence from the Upper 

San Joaquin River Basin

By N. KING HUBER

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1197

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1981
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary

GEOLOGICAL SURVEY 

Doyle G. Frederick, Acting Director

Huber, N. King (Norman King), 1926-

Amount and timing of late Cenozoic uplift and 

tilt of the central Sierra Nevada, California— 

evidence from the upper San Joaquin River Basin.

(Geological Survey professional paper ; 1197)

Bibliography: p. 27,23.

1. Geology, Stratigraphic—Cenozoic. 2. Geology, 

—Sierra Nevada Mountains (Calif, and Nev.) 

3. Geology—California--San Joaquin watershed. 

k. Earth movements—Sierra Nevada Mountains (Calif, 

and Nev.) I. Title,, II. Series.

QE690.H76 551.7 T 8'097^ 80-6o68l7

AACR2

Foi sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402
CONTENTS

Page

Abstract_________________________________ 1

Introduction ______________________________ 1

Methods of study and acknowlegments___________ 3

General setting ________________________ 5

Pre-volcanic alluvial deposits ____________________ 5

Trachyandesite of Kennedy Table __________________ 7

Composition and age_____________________ 7

Reconstruction of the lava-flow geometry__________ 9

Areal distribution_______________________ 11

Significance of river meanders________________ 11

Page

Uplift and tilting of the central Sierra Nevada___________ 13

Amount of uplift at Sierran divide ________.____ 13

Post-late Miocene uplift.._______________ 13

Pre-late Miocene uplift ________________ 16

Timing of post-late Miocene uplift ______________ 17

Summary of uplift history ___________________ 18

Differential uplift and the eastern escarpment_____————— 19

Incision of the San Joaquin canyon..___________——__ 21

Uplift and glaciation - some time constraints ___________ 25

References cited____________________________ 27

ILLUSTRATIONS

Page

FIGURES 1-4. Maps showing:

1. Generalized topographic contours of central California————————————————————————————————— 2

2. The upper San Joaquin River and vicinity._____________________———————————————————— 4

3. Distribution of Tertiary units in Friant area.______——————————————————————————————————— 6

4. Distribution and radiometric ages of quartz-latite welded tuff east of Mono Lake —————————————————— 9

5. Diagram showing reconstruction of geometry of trachyandesite of Kennedy Table—————————————————— 10

6. Map showing postulated original extent of trachyandesite of Kennedy Table ..———————————————————— 12 

7-11. Diagrams showing:

7. Uplift of Sierran drainage divide at Deadman Pass _—————————————————————————————————— 13

8. Reconstruction of lO-m.y.-old profile of upper San Joaquin River _______———————————————————— 14

9. Uplift and tilt of central Sierra Nevada by rigid-block and warped-block models——————————————————— 15

10. Uplift of the central Sierra Nevada _________________———————————————————————————— 19

11. Rate of uplift of the central Sierra Nevada_______—————————————————————————————————— 19

12. Map showing major faults east of Deadman Pass_________—————————————————————————————————— 20

13. Longitudinal profile of San Joaquin River in Sierra Nevada_________________——————————————————— 21

14. Cross sections of San Joaquin River canyon in Sierra Nevada ________________——————————————————— 22

TABLES

Page

TABLE 1. Potassium-argon age determinations________________________________________________ 8

2. Chemical analysis of quartz-latite welded tuff, pumice, and trachyandesite of Kennedy Table ———„__„—————— 9

3. Comparison of uplift, downcutting and ratio of downcutting to uplift near Pine Flat and Deadman Pass_.„.————— 24

III

AMOUNT AND TIMING OF LATE CENOZOIC UPLIFT AND TILT OF THE 

CENTRAL SIERRA NEVADA, CALIFORNIA EVIDENCE FROM THE 

UPPER SAN JOAQUIN RIVER BASIN

ByN. KINGHUBER

ABSTRACT

The upper San Joaquin River is unique among the rivers that drain 

the western slope of the Sierra Nevada in that it flowed westward across the present crest of the range until as recently as about 3.2 million years ago. Portions of the history of the river and of the topographic development of the central Sierra Nevada can be deciphered 

from tilted stratigraphic planes at the east margin of the Central Valley and dated volcanic rocks within and east of the upper San Joaquin River's present drainage basin. Uplift of the central Sierra 

Nevada was probably underway by 25 m.y. ago, but at a relatively 

low rate, probably not exceeding about 0.03 mm/yr at the present 

drainage divide at Deadman Pass. Uplift proceeded at an increasing 

rate, and is an estimated 0.3 mm/yr at present; the rate may still be 

increasing. Total uplift at Deadman Pass in the past 50 m.y. is estimated to be about 3450 m, of which two-thirds took place in the last 

10 m.y. and one-fourth in the last 3 m.y. Of these estimates, the 

amounts of pre-10 m.y. uplift and post-3 m.y. uplift are the most 

speculative. Highlights of the uplift history, ignoring qualifications 

discussed in the text, include:

1. During deposition of the Eocene lone Formation in the Central Valley, perhaps 50 m.y. ago, the San Joaquin River drained a significant area to the east of the range. Because major peaks on 

either side of the San Joaquin canyon presently rise only 450- 

750 m above the projected Eocene local base level, relief in the 

area was comparatively low.

2. Between 50 and 10 m.y. ago, uplift of about 1300 m occurred at the 

site of Deadman Pass on the present Sierran drainage divide. 

Major peaks stand 1500 to 1700 m above the 10-m.y. local base 

level, indicating that relief had increased. The stream profile at 

the site of Deadman Pass was about 900 m above sea level 10 

m.y. ago.

3. After it began, uplift and westward tilt of the range accelerated; by 

somewhat more than 3 m.y. ago, the site of Deadman Pass had 

been uplifted an additional 1200 m, and incision of the inner 

canyon of the San Joaquin River in response to uplift was well 

advanced.

4. About 3.2 m.y. ago, the San Joaquin River was beheaded by the 

eruption of basalt that filled the channel near Deadman Pass. 

Water previously flowing in this channel was probably diverted 

into the already-forming Owens Valley graben.

5. An additional 950 m of uplift at Deadman Pass took place after 

about 3 m.y. ago, for a total of 2150 m since about 10 m.y. ago. 

Until about 3 m.y. ago, the area east of Deadman Pass probably 

rose along with the Sierran block, but then lagged behind it, resulting in relative downward displacement along faults east of 

Deadman Pass of about 1100 m.

6. Partial infilling of the inner canyon by basalt and the greatly reduced stream discharge, particularly in the Middle Fork, which 

had been the main trunk of the river, greatly reduced rates of 

canyon downcutting by stream erosion in the last 3 m.y. Glacial 

erosion consequently was the dominant mechanism for removal 

of the basalt, additional incision into prevolcanic bedrock, and

enhancement of the concavity of the longitudinal stream profile 

upstream from Mammoth Pool Dam.

7. The elevation of the Sierra Nevada 3 m.y. ago may not have been 

high enough to permit extensive glaciation at that time. The lag 

deposit at Deadman Pass, previously described as a till, may be 

of nonglacial origin.

INTRODUCTION

Late Cenozoic uplift and westward tilting of the 

Sierra Nevada was convincingly demonstrated by the 

pioneering studies of Whitney (1880), Ransome 

(1898), Lindgren (1911), and others. Christensen 

(1966, p. 178), however, emphasized that "the view 

that the Sierra was tilted toward the west as a rigid, 

unitary block is valid only for the area north of the 

Tuolumne River, and not for the southern Sierra," and 

that "the amount of tilt and magnitude of uplift of the 

crest decrease from the latitude of the Tuolumne River 

northward to Lake Tahoe." He also noted that "in the 

southern Sierra Nevada the record is less clear, but it 

appears that part of the range rose by translation as 

well as rotation, with warping and faulting along the 

western margin as well as along the eastern." Data 

from the upper San Joaquin River drainage basin east 

of the Central Valley (fig. l), however, suggest that tilt 

is the dominant effect at least that far south, although 

between the Tuolumne and San Joaquin Rivers there is 

a change in tilt azimuth from west-southwest at the 

Tuolumne to southwest at the San Joaquin (see Christensen, 1966, fig. 3). The fundamental difference in uplift behavior of the southern Sierra, noted by Christensen, appears to take place south of the upper San Joaquin drainage basin.

Since Lindgren's work (l91l), many later workers 

have attempted to quantify the amount and timing of 

the uplift and tilting of the Sierra, mostly by trying to 

reconstruct stream profiles and erosion surfaces for 

successive epochs of the Cenozoic. Classic among such 

studies was that of Matthes (l930a, I960), whose data 

were derived mainly from the Merced and San Joaquin 

River basins. Such efforts were summarized and enlarged upon by Christensen (1966), who concluded that 

"the last major increment of uplift began in the inter-
LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

val between 9 and 3 m.y. ago." Furthermore, he endorsed Dalrymple's (1964) conclusion that in the upper 

San Joaquin drainage basin at least, uplift had begun 

long enough before 3.6 m.y. ago and had been of sufficient magnitude by that time not only to initiate 

Matthes' (I930a, 1960) Canyon stage of erosion, but 

also to incise the Canyon stage deep into the preceding 

Mountain Valley stage, as indicated by 3.6-m.y.-old 

volcanic flows within the canyon. Christensen (1966) 

also concluded that the Sierra had reached its present 

elevation by the late Pliocene.

Another line of evidence cited by Christensen to 

suggest that major uplift had occurred earlier than 3 

m.y. ago is that of ancient pollen and spores. A spore 

and pollen flora from elevations of 2925 and 3025 m on 

San Joaquin Mountain near the head of the San Joaquin River was assigned a late Pliocene age by Axelrod 

and Ting (i960), which is supported by an age of 3.2 

m.y. for basalt overlying the fossiliferous strata (Huber 

and Rinehart, 1967). The flora contains pollen of trees 

that exist over a wide range of altitudes, but Axelrod 

and Ting (i960) concluded that it accumulated at a

123° 122° 121° 120° 119° 118°

39°

38°

37°

36° -

FIGURE 1.—Generalized topographic contour map of central California. Contour interval 2000 ft (610 m); 1000-ft (305 m) contour is 

supplementary. From Christensen (1966). "Upper" San Joaquin River is that part east of Central Valley.
INTRODUCTION

moderate altitude of a thousand meters or so and was 

subsequently uplifted during the Pleistocene. Christensen (1966, p. 172) pointed out that the mere presence 

of pollen grains from trees of a high-altitude environment indicates an elevated source area somewhere in 

the general region whereas the middle- and lowaltitude varieties could have been transported by prevailing winds from lower elevations on the western 

slope of the range, and he suggested that "the Sierra 

Nevada stood at approximately its present elevation 

during late Pliocene time." If the calculations presented in this study are credible, a compromise conclusion is warranted: 3 m.y. ago the collection sites had an 

elevation of about 2040 m and the Ritter Range, 8 km 

to the west with elevations of 3100 m or more, probably 

was high enough to supply the appropriate highaltitude pollen.

Grant, McCleary, and Blum (1977) reported that on 

the east side of the Central Valley between the 

Mokelumne and Merced Rivers, bedding planes of formations ranging in age from about 22 m.y. (Valley 

Springs Formation) through 9 m.y. (Table Mountain 

Latite) to about 5 m.y. (Mehrten Formation) in age 

have approximately the same dip. This led them to conclude that the Sierra Nevada was relatively stable during this time interval and that the major uplift of the 

Sierra Nevada began tilting the rocks along the east 

side of the Central Valley about 5 m.y. ago. They also 

concluded that uplift has taken place at a relatively 

uniform rate over the past 5 m.y., but their sparse data 

are only suggestive.

The most recent review of uplift timing is by Slemmons, Van Wormer, Bell, and Silberman (1979), who 

contributed some new data based on uplift of radiometrically dated volcanic rocks in the Carson Pass-Sonora 

Pass section of the north-central Sierra Nevada. They 

concluded that although minor uplift was taking place 

as long ago as the Oligocene, the "main uplift" in that 

area began about 17 m.y. ago, accelerated during the 

late Cenozoic, and continues today.

Hay (1976) invoked plate-tectonic theory to speculate 

that the late Cenozoic uplift of the Sierra began with 

the advent of the San Andreas transform fault system 

and was "***accelerated about 4.5 m.y. ago in response 

to the northward migration of the Mendocino triple 

junction and the increased rate of motion between the 

North American and Pacific plates." Although this 

scenario is appealing, he brought no new data into the 

argument, and any estimates of the actual timing of 

the uplift should be based on more direct evidence.

It is possible that uplift was started somewhat earlier 

in the southern part of the range and progressed 

northward with time (see, for example, Hay, 1976; 

Crough and Thompson, 1977).

The preuplift San Joaquin River headed at least as 

far east as the present Mono Lake basin, possibly 

farther north or east in Nevada, and its course across 

the west slope of the Sierra Nevada has changed little 

since the Eocene, when the lone Formation was deposited in the Central Valley. It is this continuity of course 

that makes the San Joaquin River especially useful in 

reconstructing Sierran tectonics for at least part of the 

range, as all of the rivers north of Yosemite had their 

courses drastically altered by extensive Oligocene and 

Miocene volcanism. Three stratigraphic markers are 

available for structural analysis: the lone Formation; a 

10-m.y.-old lava flow capping a group of table mountains east of Friant; and an alluvial fan on the Kings 

River east of Fresno. Several critically located and 

dated volcanic units within the drainage basin help 

provide additional time constraints.

The San Joaquin River was beheaded at the present 

Sierran divide about 3.2 m.y. ago by a combination of 

volcanic activity and relative down-faulting to the east. 

The cumulative displacement on the eastern rangefront fault system is approximately equivalent to the 

amount of post-3 m.y. uplift at this locality.

Estimates of the total amount of uplift at the divide 

depend upon choice of a model involving tilt of a rigid 

block or of one involving broad doming with a decrease 

in amount of tilt eastward from a hinge line. In either 

case the hinge line is assumed to lie at the east margin 

of the Central Valley near Friant at the intersection of 

the tilted stratigraphic planes of the lone Formation 

(approximately 50 m.y. old) and the table mountain 

complex (10 m.y. old) at a present elevation of approximately 150 m above sea level (fig. 2). The simple tilt 

model yields a maximum post-10-m.y. uplift value at 

Deadman Pass on the present drainage divide of approximately 2150 m. A dome model would yield a 

somewhat lower but undetermined uplift value. Using 

present-day elevations in the range, correlative calculations permit estimation of pre-uplift elevations and relief. For example, if the uniform tilt model is applied to 

Mount Ritter, now at 4010 m, this peak would have had 

an elevation 10 m.y. ago of about 2000 m associated 

with a local relief of about 1050 m (these figures do not 

allow for erosional lowering of the mountain). This report will develop the rationale and present the analysis 

leading to these conclusions. It will not consider possible causes or mechanisms for the uplift.

METHODS OF STUDY AND ACKNOWLEDGMENTS

Many of the calculations in this report are based on 

graphic reconstruction of stream base levels and longitudinal profiles at a scale of 1:62,500 (with vertical 

exaggeration of about 10x) based upon 15' topographic 

quadrangle maps with contour intervals of 80 feet
LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA 

120° 119°

LONG VALLEY

Deadman Pass 

Mammoth

FIGURE 2.—"Upper" San Joaquin River and vicinity. The 500-ft (150-m) contour marks approximate east margin of Central VaDey and 

assumed hinge line for Sierran tilt. Main trunk of upper San Joaquin river emphasized by heavier line weight.
PRE-VOLCANIC ALLUVIAL DEPOSITS

(24.4 m), except for the Clovis quadrangle with a 50- 

foot (15.2 m) interval. The profiles were projected onto 

a vertical plane oriented N. 40 E., thus the slope depicted for any given reach will be greater than the actual stream gradient as measured along the stream 

bed. Because the topographic maps used in this study 

are contoured in U. S. customary units rather than 

metric units, the customary units were used in most 

calculations regarding uplift of the range. An unrealistic number of significant figures was retained to avoid 

multiple rounding errors during sequential calculations, but after the results were converted to the metric 

system, they were rounded to avoid an unwarranted 

aura of accuracy; even then, the conclusions are not 

necessarily as accurate as the numbers might imply. 

Because of the rounding, some of the results as presented may not sum properly. In converting elevation 

data to the metric system, figures have not been significantly rounded so that one can reconvert for use 

with the topographic maps.

J. C. Von Essen and M. L. Silberman of the U. S. 

Geological Survey and G. H. Curtis and R. E. Drake of 

the University of California, Berkeley, supplied 

potassium-argon age determinations. All age determinations cited from the literature have been recalculated 

using the new constants given in table 1 and are thus 

about 2.5 percent older than those in the original 

source. In age discussions, the Miocene-Pliocene 

boundary is considered to be at about 5 m.y. B. P. (Van 

Couvering, 1978). I have benefited greatly from discussions and data supplied by many of my colleagues, in 

particular J. A. Bartow, P. C. Bateman, M. M. Clark, D. 

S. Harwood, E. J. Helley, R. J. Janda, D. E. Marchand, 

and G. I. Smith; naturally I remain responsible for any 

errors in interpretation.

GENERAL SETTING

The trachyandesite of Kennedy Table is exposed in 

the upper San Joaquin River drainage basin in the 

western foothills of the Sierra Nevada east of Friant 

(fig. 3). The trachyandesite, together with underlying 

stream-deposited sand and gravel, marks the location 

of a late Miocene channel of the San Joaquin River. 

The trachyandesite is more resistant to weathering and 

erosion than the granitic rock that makes up most of 

the subjacent bedrock in this vicinity. Preferential erosion of the granitic rock since the eruption of the 

trachyandesite, coupled with uplift and tilting of the 

Sierra Nevada, has left erosional remnants of the 

trachyandesite and underlying gravel standing as a 

series of flat-topped "table" mountains, a classic 

example of topographic inversion. These table mountains allow one to reconstruct partially the drainage

pattern of the late Miocene San Joaquin River, and the 

plane defined by the tops of the table mountains and 

its upstream projection allow estimates to be made of 

contemporary relief and the amount of uplift and tilt of 

the Sierra Nevada since the eruption of the 

trachyandesite. Such estimates have been made by 

Dalrymple (1963), Christensen (1966), and Bateman 

and Wahrhaftig (1966).

Janda (1966) included the trachyandesite (his 

"basalt") as a member of his proposed Auberry Formation, the remainder of which is made up of the underlying late Miocene alluvial deposits. Marchand (1976) 

followed this usage in a preliminary report. The 

trachyandesite flow, however, is the product of a single 

geologic event of short duration and because of its usefulness as a stratigraphic marker, it warrants its own 

geologic name. Trachyandesite of Kennedy Table is 

here used because Kennedy Table provides the largest 

areal exposure of the trachyandesite flow. This supersedes my informal name, San Joaquin table mountain 

andesite flow, used in a preliminary report (Huber, 

1977). Inasmuch as the name Auberry Formation has 

not been proposed nor the unit described in a formal 

publication, the name will not be used further in this 

report, and the alluvial deposits beneath the 

trachyandesite flow will simply be referred to as prevolcanic alluvial deposits.

PRE-VOLCANIC ALLUVIAL DEPOSITS

Late Miocene alluvial deposits can be traced discontinuously beneath the trachyandesite of Kennedy Table 

from the unnamed table northeast of Table Mountain 

(fig. 3) westward to where the deposits disappear beneath alluvial deposits of the Turlock Lake Formation 

of Pleistocene age at the margin of the Central Valley 

(Marchand, 1976). Recognition of pre-volcanic alluvial 

deposits east of the unnamed table is hampered by the 

presence of extensive talus aprons that generally conceal the base of the trachyandesite at Kennedy Table 

and Squaw Leap.

The easternmost "exposures" of the alluvial deposits 

consist mostly of scattered cobbles observed downslope 

from the generally concealed base of the lava flow; the 

alluvial deposits are probably quite thin and actual 

outcrops are uncommon. Near the west end of the exposures of the pre-volcanic alluvial deposits, about 3 

km east of where they dip beneath younger alluvium, 

the deposits consist of about 45 m of interbedded 

stream gravels, silts and water-laid volcanic ash, overlying granodiorite (Janda, 1966). This section, on the 

south side of the ridge north of Little Dry Creek, is the 

type section for Janda's Auberry Formation and presumably reflects an interbedded mixture of channel
6

LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

gravels and finer grained flood-plain deposits. Approximately 42 m of similar material is exposed on the 

north side of the same ridge, but the base of the deposit is concealed there.

On the west side of the San Joaquin River, west and 

north of exposures of the lone Formation, are scattered 

areas underlain by sediments that Janda (1966) and 

Marchand (1976) included with the pre-volcanic alluvial deposits (the lower cart of their Auberry Formation). This correlation is incompatible with physiographic evidence and is now questioned by Marchand 

(oral commun., 1979). The true stratigraphic position 

of these sediments has not been established.

Abundant pumice pebbles and cobbles occur in a 

pumice-rich layer exposed in the pre-volcanic alluvium 

on the north side of the ridge north of Little Dry Creek. 

The abundance of the pumice pebbles within a discrete 

horizon of the alluvial deposit suggests that they were

37°10' 119°45' 119°40' 119°35' 119°30'

37°05' -

37°00' -

36e55' 

FIGURE 3

Trachyandesite of 

Kennedy Table

-Distribution of Tertiary units in Friant area. Modified from Macdonald (1941), Marchand (1976), and Bateman and Busacca (i960,

in press).
TRACHYANDESITE OF KENNEDY TABLE

probably deposited shortly after the eruption of the 

pumice at a time when the pumice was a major component of the stream bedload. Potassium-argon ages of 

10.9 and 11.3 m.y. have been obtained on biotite and 

plagioclase from this pumice (table 1, sample A-7), and 

thus the volcanic source for the pumice is probably 

somewhat more than 11 m.y. old. There is no source for 

pumice of this age and composition within the 

present-day drainage basin of the San Joaquin River, 

therefore it must have come from east of the present 

drainage divide.

The only likely source of pumice of this general age 

and composition known east of the drainage divide is a 

welded tuff that occurs discontinuously over an area of 

about 400 km2 east of Mono Lake (Gilbert and others, 

1968). An analysis of a sample of this welded tuff (table 2, sample GM-41) collected from the northwest 

corner of the Glass Mountain quadrangle (Krauskopf 

and Bateman, 1977) compares very favorably with that 

of pumice pebble, especially when recalculated water 

free (table 2, sample A-7). The water-free recalculation 

takes into account the high water content of the pumice 

pebble, which has probably been in a ground-water 

saturated environment for a least several million years, 

as it was when collected.

For the unnamed welded tuff east of Mono Lake, Gilbert, Christensen, Al-Rawi, and Lajoie (1968) presented 12 K-Ar age determinations ranging from 11.4 to 

12.2 m.y. (fig. 4). Multiple ash-flow units are present 

and mineralogy varies, so that at least some of the age 

spread may represent real age differences. The closest 

other tuff of similar composition in the region, which is 

exposed north of Mono Lake, has been correlated with 

the Eureka Valley Tuff, for which more than 10 ages of 

9.0-10.3 m.y. have been reported (recalculated from 

Noble and others, 1974). This tuff appears to be significantly younger than the unnamed tuff and the alluvial pumice, and it was erupted from the Little Walker 

caldera, east of Sonora Pass (Noble and others, 1974), 

which is less likely to have contributed significant alluvial material to the San Joaquin River drainage. Furthermore, the alluvial pumice north of Little Dry Creek 

was buried by the 10-m.y. old trachyandesite of Kennedy Table before the eruption of most of the Eureka 

Valley Tuff (see later section). As the ages determined 

on plagioclase and biotite from the pumice pebble are 

discordant, argon loss is suggested, and the older age 

(11.3 m.y.) should be taken as a minimum. The actual 

age perhaps is closer to that determined for the unnamed welded tuff.

In summary, a source for the late Miocene alluvial 

pumice exposed beneath the complex of table mountains near Friant has not been positively identified, but 

it must have come from east of the present Sierran

drainage divide, and the welded tuff east of Mono Lake 

appears to be the most likely source. In addition, the 

abundant pumice and associated fine silt in the alluvial 

deposits suggest that the original stream gradient at 

the depositional site was low and that the site was near 

the margin of the late Miocene Central Valley. The 

coarser gravel also present would represent flood-stage 

deposits.

TRACHYANDESITE OF KENNEDY TABLE 

COMPOSITION AND AGE

The trachyandesite of Kennedy Table was originally 

described as an olivine basalt (Macdonald, 1941), and 

subsequent references have followed this designation. 

Unfortunately, Macdonald's description was apparently 

the basis for a subsequent miscorrelation of the lava 

flow with an olivine-basalt plug at Sugarloaf Hill in 

Jose Basin, whose location is approximately on the upstream projection of the flow (Dalrymple, 1963). Macdonald (1941) mapped that part of the trachyandesite 

within the Clovis 15' quadrangle, and Bateman and 

Busacca (1980, in press) mapped that part within the 

Millerton Lake 15' quadrangle.

The trachyandesite is a dark-gray, finely porphyritic 

rock with intersertal texture. The dominant phenocrysts are 2- to 5-mm plagioclase laths with average 

composition about Anes. Microphenocrysts are of 

clinopyroxene and minor olivine. The groundmass includes plagioclase, clinopyroxene, opaque minerals, 

and dark-brown glass with dusty inclusions. Stained 

slabs show that potassium is confined to the matrix, 

probably chiefly in the glass.

The Kennedy Table lava flow is designated a 

trachyandesite on the basis of its chemical composition 

(table 2) using the classification of Rittmann (1952). 

Although there are other bodies of trachyandesite in 

the central Sierra Nevada, few have as high a silica 

content as the Kennedy Table flow, and only two other 

bodies are known in the upper San Joaquin drainage 

basin. One body occurs east of the Devils Postpile, but 

it is of Pleistocene age (Huber and Rinehart, 1967; 

Huber, 1977). The second occurrence is an intrusive 

volcanic neck near the community of Big Creek (Bateman and Lockwood, 1976). However, the latter volcanic 

rock differs significantly from the trachyandesite of 

Kennedy Table in the content of all other major oxides 

as well as in mineralogy, notably a high olivine content. 

Thus there are no known volcanic flow remnants or 

necks of composition and age similar to the 

trachyandesite of Kennedy Table upslope from the easternmost table mountain remnants at Bug Table and 

Squaw Leap.

The olivine-basalt plug in Jose Basin, previously correlated with the trachyandesite of Kennedy Table, has
8 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

TABLE 1.-Potassium-argon age determinations

[Potassium analyses were done on an I.L. flame photometer using a lithium internal standard. Argon analyses were made using standard techniques of isotope dilution. Ages were calculated 

using the following constants:

40K decay constants: X € =0.572x10' 10yrl; X e ' =8.78xlO' 13yr-l; X f = 4.962x10' Wyr 1 ; abundance ratio: 40K/K = 1.16 7x10 " 4 atom percent.

Analysts: TM-10 through SNV-51, Paul Klock, Scott Morgan. B. Myers, and S.E. Sims; 69-M-ll, M. Cremer and M.L. Silberman; KA-2755 and 2916, KAr lab.. University of California, 

Berkeley (see sample notes)]

4 °Arrad 4 °Arrad Calculated age 

Sample Sample Material K20 (moles/g 40Arraa (millions of 

no. (Percent) xlO'H' (percent) years)

TM-10 Trachyandesite of Plagioclase 0.447 

Kennedy Table .452

Whole rock 2.92 

2.91 

2.94 

2.91

MLC-52 Trachyandesite of Plagioclase .482 

Kennedy Table .484

Whole rock 2.88 

2.89 

2.90

2.88 /

A-7 Pumice pebble beneath Plagioclase .897 

trachyandesite of .883 

Kennedy Table

Biotite 7.71 1 

7.67 1

SNV-41 Basalt at Rancheria Whole rock 4.62 . Creek 4.60 ' 

4.62

4.58 J

0.4495 0.6161 15 9.5±0.2

• 2.92 4.372 76 10.4±0.2

.483 .7057 11 10.1 ±0.5

1 > 2.888 4.196 66 10.1 ±0.2

1

.890 1.458 54 11.3±0.2

7.69 12.15 24 10.9 ±0.2

> 4.61 2.123 42 3.20±0.06

I

SNV-54 Basalt pebble from Whole rock 2.248 V 

Kings River fan 2.248 I 2 246 1 21g 75 3.76±0.08

2^239 )

SNV-51 Dacite pebble from Biotite 8.38 

Kings River fan 8.34

69-M-ll Dacite from Windy Hornblende 1.289 

Peak 1.295

Biotite 5.45 

5.18

KA-2755 Basalt from Stony Whole rock 2.14 

Flat 

KA-2916 Rhyolite tuff from Sanidine 8.125 

Alpers Canyon

Sample locations and notes:

8.36 4.854 11.5 4.03±0.12

. 1.292 .838 14 4.5±0.4

5.32 3.351 13 4.4±0.4

1.048 35 3.40+0.06 

16.58 98 11. 7 ±0.1

TM-10 Millerton Lake 15' quadrangle, Calif., lat 37°06'N, long 199°36'W. (Huber, 1977). 

MLC-52 Millerton Lake West 7i ' quadrangle, Calif., lat 37°01'N, long 119°38'W. (Huber, 1977). 

A-7 Friant7i' quadrangle, Calif., lat 36 °57'N, long 119°41'W. (Huber, 1977). 

SNV-41 Tehipite Dome 15' quadrangle, Calif., lat 36°58'N, long 118°55'W. 

SNV-54 Piedra 7i ' quadrangle, Calif., lat 36°46'N, long 119°30'W. 

SNV-51 Piedra 7i ' quadrangle, Calif., lat 36°46'N, long 1 19°30'W. 

69-M-ll MarionPeak 15' quadrangle, Calif., lat 36 °59'N, long 118 °37'W. Collected by J. G. Moore. 

KA-2755 Miramonte 7$' quadrangle. Calif., lat36°43'N, long 119°2'W. Age data courtesy of G. H. Curtis andR. E. Drake, Univ. California, Berkeley (Moore and others, 

1979). 

KA-2916 Cowtrack Mountain 15' quadrangle, Calif., lat 37 °45'N, long 1 18 °56'W. Collected by R. A. Bailey and E. W. Hildreth. Age data courtesy of G. H. Curtis and R. E. 

Drake, Univ. California, Berkeley (written commun., 1979).
TRACHYANDESITE OF KENNEDY TABLE

a potassium-argon age of 9.8 m.y. (recalculated from 

Dalrymple, 1963), and this age has commonly been 

cited as the age of the trachyandesite flow. The correlation is no longer tenable because of compositional differences. New data indicate an age of approximately 10 

m.y. for the trachyandesite (table l). This new age in 

itself is not sufficiently different enough from the previously assumed age to compromise seriously the calculations regarding relief and uplift of the Sierra Nevada 

made by Dalrymple (1963) and Christensen (1966), in 

spite of the miscorrelation.

Late Cenozoic volcanic rocks in this part of the Sierra 

fall into two main age groups, 3-4 m.y. and 9-11 m.y.; 

the younger group is more abundant geographically if 

not in volume. The trachyandesite of Kennedy Table is 

the only dated lava flow within the older group. All 

other dated rocks within this group, of which there are 

only three in the San Joaquin drainage, are basaltic 

dikes or volcanic necks; erosion since their emplacement has removed any of their extrusive equivalents. 

To my knowledge these intrusive rocks and the 

trachyandesite of Kennedy Table are the southernmost 

dated rocks of the 9-11-m.y. age group in the Sierra 

Nevada. Other volcanic rocks in this age group occur

TABLE 2.-Chemical analyses of quartz-latite welded tuff, pumice, and 

trachyandesite of Kennedy Table

(GM-41 and A-7: x-ray spectrographic analyses by L. F. Espos; chemical analyses of FeO, 

H20, and C02 by M. J. Cremer. MLc-52 and TM-10: X-ray spectrographic analysis by V. 

G. Mossotti and B. W King; chemical analyses of FeO, H20 and C02 by J- H. Tillman]

Field no.1 

Lab. no.

Si02

A1203

Fe203

FeO

MgO

CaO

Na20

K20

H20+ 

H20-

TK)2

P205

MnO

CO

TotalS

Welded tuff 

GM-41 

M -131678

63.03

16.80

3.08

1.30

110

2.46

3.93

5.35

.41

.36

.89

25

.066

.29

027

Pumice Welded tuff 

A-7 GM-412 

M-131679

61.08

17.03

2.47

1.67

1.09

2.79

2.75

4.85

4.21 

.99

£1

.26

.074

.06

.011

6413

17.09

313

1.32

112

2.50

4.00

5.44

.91

25

.067

.027

Pumice

A-72

64.37

17.95

2.60

1.76

115

2.94

2.90

511

S5

21

.078

.012

Trachyandesite

MLc-52 

M131275

57.57

18.67

2.20

3.47

2.36

6.29

412

3.27

.66 

12

1.08

.47

10

.03

.005

TM-10 

M131272

5712

18.55

2.44

3.24

2.35

6.31

4.02

3.29

.79 

.70

1.06

.46

.096

.03

.006

Total 99.34 10015 99.98 99.99 100.4 100.44

Cr

Ni

Ba

Sr

V

Sc

Y

39 ppm

14

1500

230

400

40

10

31

36 ppm

15

1300

220

490

40

11

44

16 ppm

1350

96

980

174

16

23

16 ppm

1450

101

1000

165

15

20

1GM-41: Welded tuff from sec. 36, T. 2 N., R. 29 E., Glass Mountain 15' quadrangle, 

California; A-7: Pumice pebble from steam gravel beneath trachyandesite of Kennedy 

Table, sec. 21, T. 11 S., R. 21 E., Friant 71' quadrangle, California; MLc-52: Trachyandesite from sec. 35, T. 10 S., R. 21 E., Millerton Lake 15' quadrangle, California; TM-10: 

Trachyandesite from sec. 32, T. 9 S., R. 22 E., Millerton Lake 15' quadrangle, California.

^Recalculated less H20 and C02 .

from the Tuolumne drainage northward and include a 

latite, dated at 9.2 m.y. (recalculated from Dalrymple, 

1964), which makes up another Table Mountain west of 

Sonora, also a classic example of topographic 

inversion.

The eruptive source of the trachyandesite is unknown. The composition of the trachyandesite, unique 

for this part of the Sierra, rules out as a source any of 

the known late Cenozoic volcanic necks and plugs in 

adjacent areas of the San Joaquin drainage (Huber, 

1977). Inasmuch as the flow must have originally covered at least 95 km2 to a depth of as much as 60 m, the 

source must have been significant. The entire area has 

now been mapped geologically in considerable detail 

(l :62,500), and it is unlikely that any major possible 

source has been overlooked. I believe that the lava flow 

ponded and covered its own source, which was most 

likely in the area of Kennedy Table.

RECONSTRUCTION OF THE IAVA-FLOW GEOMETRY

Similarities in texture and composition of rocks from 

each of the table mountain remnants, as well as their 

difference from other volcanic rocks in the region, indicate that together they make up a volcanic unit. 

Macdonald (1941) thought that he could recognize two 

flows on Table Mountain, apparently because of the 

presence of two zones of columnar jointing, one 0 above 

the other. However, excellent exposures at the north

119°

38°

FIGURE 4.—Distribution and radiometric ages ot quartz-latite welded 

tuff in "11-m.y." age group east of Mono Lake (Gilbert and 

others, 1968). Ages indicated have been recalculated using new 

decay constants. Alpers Canyon is location of rhyolite welded tuff 

(table 1).
10 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

end of Table Mountain and the south end of the adjacent unnamed table (both north of Macdonald's map 

area) make it clear that the trachyandesite is a single 

flow with individual columnar zones related to the 

upper and lower parts of the flow and grading inward 

to a blocky jointed center. Bateman and Busacca 

(1980, in press) also found no evidence for more than 

one flow either here, at Kennedy Table, or elsewhere in 

the Millerton Lake 15' quadrangle (P. C. Bateman, oral 

commun., 1977). Thus the trachyandesite of Kennedy 

Table is the result of a single eruption, and reconstruction of its original surface and distribution need not be 

complicated by the possibility of several flows with differing geometry.

The present attitude of a plane that closely approximates the original upper surface of the trachyandesite 

lava flow can be determined by contouring elevations 

on the least eroded parts of the table mountain remnants, a procedure that yields surprisingly uniform results. For a flow distance of 15 km the plane has a slope 

of about 24.3 m/km and a dip azimuth of S. 40° W. 

(fig. 5). This azimuth closely approximates the average 

trend of both the present and the late Miocene San 

Joaquin River; its projection 94 km northeastward 

from Friant Dam crosses the present drainage divide 

only 5 km south of Deadman Pass, the site of the late 

Miocene river crossing of the present divide. Because 

of this concidence I assume that this azimuth approximates the actual direction of tilt for this segment of the 

Sierra in the last 10 m.y., and in further reconstructions in this report all data points are projected onto a 

vertical plane with this azimuth. This azimuth differs by 

about 10° from one (S. 50° W.) obtained by drawing a 

line through Friant Dam perpendicular to elevation

contours generalized for the Sierra Nevada by Smith 

(1964). Distances measured along one projection 

rather than the other would only differ by 1.5 percent, 

an amount probably of little significance considering 

the imprecision of the data.

The upper surface of the lava flow appears to define a 

rather uniform plane as far west as the last control 

point at Table Mountain. No faulting of the flow surface was recognized. Data points on the base of the 

flow, however, indicate a decreasing gradient westward 

from 27.1 m/km in the Bug Table-Squaw Leap area to 

22.3 m/km for the exposures north of Little Dry Creek; 

this gradient change presumably reflects a westward 

decrease in the gradient of the pre-volcanic San Joaquin River (fig. 5). The stream profile represented by 

the base of the lava flow is a projection rather than a 

true longitudinal profile that follows the stream course, 

and the gradients determined from it are greater than 

actual ones. In an alluviated area, such a projected 

gradient might best be thought of as the gradient of 

the river flood plain rather than that of the active 

channel itself, and thus it represents the broader surface over which the lava flow was spread.

The lower gradient of 22.3 m/km at the west end of 

the trachyandesite exposures occurs where the prevolcanic alluvium reaches thicknesses greater than 40 m, 

consists in part of pumice and fine silt, and can 

reasonably be considered to be part of the flood plain 

of the late Miocene San Joaquin River where it was 

probably graded to the newly evolving Central Valley. I 

assume that the gradient at this locale 10 m.y. ago was 

about 1 m/km, similar to that of the present San Joaquin River where it is graded to the present Central 

Valley axis below Friant Dam (Marchand and Allwardt,

METERS

1200 H

Estimated maximum original 

upstream extent of lava flow

10 15 20 

DISTANCE, IN KILOMETERS

25 30

FIGURE 5.—Reconstruction of upper and lower surfaces of trachyandesite of Kennedy Table. Also shown is projection of conglomerate horizon 

in lone Formation and present-day profile of San Joaquin River. All data are projected onto a vertical plane striking N. 40° E. Vertical 

exaggeration about 10 X.
TRACHYANDESITE OF KENNEDY TABLE 11

1980, in press). Control points from the base of the 

lava flow indicate that this assumed gradient increased 

to nearly 6 m/km some 23 km to the northeast in the 

vicinity of Squaw Leap (fig. 5). The change in gradient 

over this reach is not gradual but takes place rather abruptly near Table Mountain, on either side of which the 

gradient is relatively uniform. I interpret the Table 

Mountain area, therefore, as being the approximate 

point at which the lO-m.y.-old San Joaquin River became graded to the Central Valley area within a reentrant of that valley into low foothills existing at that 

time. That this abrupt change does not represent a 

superimposed flexure is demonstrated by the absence 

of a similar feature on the upper surface of the lava 

flow. Northeast of the gradient change, the prevolcanic alluvial deposits appear to be thinner, and locally the lava flow rests directly upon weathered granitic 

bedrock.

AREAL DISTRIBUTION

The trachyandesite of Kennedy Table is interpreted 

as a single lava flow. Reconstruction of the original extent of the flow requires fitting its remaining erosional 

remnants into a reasonable physiographic setting.

The arcuate shape of some of the table remnants, 

particularly Table Mountain and the unnamed table to 

the northeast, suggests that they might reflect meander patterns of the prevolcanic stream. Most previous 

workers appear to have adopted this hypothesis although it has not been explicitly stated, except perhaps 

by Wahrhaftig (I965a, p. 124): "the basalt [sic] apparently flowed down a winding former valley of the San 

Joaquin River." The overall distribution of the 

trachyandesite suggests, however, that the lava filled a 

much broader valley and that the fortuitous shapes of 

some of the table remnants is a result of erosion controlled instead by a meandering stream superimposed 

upon the newly erupted lava flow.

The presence of well-developed columnar joints indicates that the lava flow ponded and solidified in place, 

a circumstance that means the lava filled the preexisting stream valley to a relatively even level and developed a relatively flat upper surface. It also suggests 

that the stream gradient, at least at the west end of the 

flow, was low, reinforcing the conclusion drawn from 

the nature of the underlying alluvial deposits.

Ponding of the lava flow would provide a hydraulic 

head for driving lava from the eruptive source into the 

main river valley upstream and into tributaries, such as 

that at Squaw Leap, until hydrostatic equilibrium was 

reached. This situation makes possible a reasonable reconstruction of the possible original extent of the lava 

flow and of its upper surface.

The minimum original extent of the trachyandesite of

Kennedy Table can be obtained by simply circumscribing the area of present outcrop, treating several outlying segments as the result of backflow into tributary 

valleys. Such an area as enclosed by the short-dash line 

on figure 6 includes about 95 km2 . If one envisions a 

wider, more mature, pre-volcanic valley, the areal extent of the lava flow could have been considerably 

greater. The area enclosed by the long-dash line on figure 6 includes the outcrops on Pincushion and Crook 

Mountains as part of the main-valley flow rather than 

tributary back-up, and allows for up-valley flow as far 

as consistent with the eastward projection of the upper 

flow surface, about to Redinger Dam. This area of 

about 250 km2 does not include any westward extension beyond the water gap between the cuesta of lone 

Formation south of Little Table Mountain and the ridge 

of metamorphic rock at Owens Mountain. The hachured 

line on figure 6 indicates areas higher than the plane of 

the present flow top and limits the location of the prevolcanic San Joaquin River, although it does not allow 

for erosion since 10 m.y. ago. The meander pattern of 

the present San Joaquin River east of Friant suggests 

that the lava did indeed flow into a fairly broad valley 

and that the larger original areal extent of the flow is 

more likely.

SIGNIFICANCE OF RIVER MEANDERS

The meanders of the San Joaquin River where it 

traverses the Sierra foothills from Redinger Dam to the 

Friant Dam are of large wavelength^ and amplitude 

(fig.6). The meanders also exhibit a complex sinuousity with northeastward downstream components, which 

exceed 1 km in three places, opposite to the mean slope 

direction. This pattern indicates that the meanders 

must have developed their present configuration on a 

low-gradient surface prior to subsequent uplift and tilting of the river channel, long before the present river 

gradient was established. The meanders were probably 

formed shortly after the river flowed out over the newly 

erupted trachyandesite of Kennedy Table, which provided a new low-gradient surface several kilometers 

wide within the preexisting late Miocene valley of the 

San Joaquin River.

The meanders are incised into bedrock for the entire 

length of the channel eastward from Friant Dam, but it 

is likely that their geometry was established in alluvial 

material spread out by the river as it flowed with a reduced gradient over the new surface for much of the 

length of the lava flow. Drawing on the experimental 

work of Gardner (1975), Schumm (197?) noted that 

one way incised meanders can form is by base-level 

lowering or nearly vertical uplift. In the case of the San 

Joaquin River, its bed would have been uplifted nearly
12 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

vertically and instantaneously an amount equal to the 

thickness of the lava flow, resulting in what would be 

equivalent to a base-level lowering at the western distal 

end of the flow. Quoting Schumm (1977, p. 200-201):

*** a lowering of base level causes headward incision up the meander 

pattern. Following rejuvenation, a nickpoint will migrate upstream and will follow the existing channel pattern to form incised meanders in the underlying bedrock. However, as headward erosion progresses along a given meander, the 

downstream limb of the meander encounters bedrock first, 

and is then locked in position. The upstream limb of the 

meander, still on alluvium, continues to shift downstream as 

part of a normal downvalley sweep of the meander pattern, 

and the meander loop is deformed. By the time the upstream 

limbs of the meanders became fixed in bedrock, a very deformed meander usually had developed.

This mechanism would explain the "deformed" meanders of the San Joaquin, which look very much like the 

incised meanders of the Goosenecks of the San Juan 

River on the Colorado Plateau, illustrated as examples 

by Schumm. This meander pattern also suggests that 

the original extent of the lava flow included most of the 

area occupied by the present meander belt, the larger 

of the two areas indicated in figure 6.

Lateral migration of the river within the highly resistant lava flow would be difficult, and the meander pattern once established was probably rapidly incised into 

the trachyandesite and subsequently into the underlying deeply weathered granitic rocks. That the granitic 

rocks were deeply weathered by post-Eocene time is 

shown by the abundance of quartz grains and 

feldspar-derived clay and the absence of granitic pebbles in the Eocene lone Formation and the relative rar37°15' 119°45' 119°30'

37°00'

•P-

/Mountain\*^ ^ / ^)\ 

\V^VJ &

j~r Pincushion \ \J /

I

012345 KILOMETERS i i i i i i

FIGURE 6.—Postulated original extent of trachyandesite of Kennedy 

Table. Dark areas show present outcrop; short-dash line indicates 

minimum extent; long-dash line probable extent. Hachured line 

indicates areas presently above plane defined by top of

trachyandesite. Hachured double line indicates cuestas of lone 

Formation, the east edges of which are above that plane. Millerton Lake and other reservoirs omitted to emphasize pre-reservoir 

meander pattern of San Joaquin River.
UPLIFT AND TILTING OF THE CENTRAL SIERRA NEVADA 13

ity of granitic pebbles in the late Miocene gravels underlying the lava flow. The lava flow itself was eroded 

chiefly by undercutting and spalling of joint blocks as 

shown by continued existence of remnant surfaces 

nearly approximating the original surface of the flow.

With accelerated uplift of the Sierra Nevada, channel 

downcutting would also have been accelerated. There 

was, of course, some lateral cutting and meander migration, as shown by local asymmetry of the canyon 

walls at some meander bends, such as at Horseshoe 

Bend north of Auberry, but such migration appears to 

have been insufficient to greatly alter the original 

meander pattern, and the canyon as a whole has surprisingly symmetrical cross sections for a stream with 

meanders of such large wavelength.

"Meander length is empirically related to the square 

root of effective or dominant discharge" (Leopold and 

others, 1964, p. 296). Other factors remaining constant, discharge in turn is directly proportional to the 

area of the drainage basin. Between Friant Dam and 

Redinger Lake, a straight-line distance of about 30 km, 

meander wavelengths range from 4.2 to 5.6 km, with 

an average of 4.6 km. For the present San Joaquin 

drainage basin of 4340 km2 this is an order of magnitude larger than that to be expected on the basis of 

data from alluvial channels (Leopold and others, 1964, 

fig. 7-48). Although the meanders under consideration 

are in bedrock rather than alluvium, Dury (1977) concluded that "meanders in bedrock, however great the 

distorting influence of structure, tend to be geometrically similar to alluvial meanders, in every respect except that of being ingrown." Direct comparison between alluvial- and bedrock-channel meanders is probably not without pitfalls, but it appears that the initial 

meanders developed upon the surface of the newly 

erupted lava flow were formed by a stream with a 

larger discharge and drainage basin than the present 

stream, which would be the case if the stream at that 

time headed east of the present Sierran drainage divide. In summary, the meander wavelength suggests 

that the stream discharge was higher than at present 

and their sinuosity suggests that the stream gradient 

was low.

UPLIFT AND TILTING OF THE CENTRAL SIERRA 

NEVADA

AMOUNT OF UPLIFT AT SIERRAN DIVIDE

Previous estimates of the amount of uplift of the Sierran divide mostly have been based upon the reconstruction of former stream profiles. This method has 

been useful; indeed, stream profiles will be used to 

help decipher uplift history in this report. However, I 

have used an additional method of estimating uplift

that involves establishing a base-level plane independent of variable stream gradients within the interior of 

the range. Much of the foregoing discussion regarding 

the geometry and physiographic setting of the 

trachyandesite and the underlying alluvial deposits has 

been a preamble to the use of such a method.

POST-LATE MIOCENE UPLIFT

Several lines of evidence have been developed—the 

fine-grained and locally pumiceous nature of some of 

the alluvial deposits, the planar and broad lateral extent of the trachyandesite lava flow, and the postvolcanic stream-meander pattern—that collectively 

suggest that the late Miocene San Joaquin River had a 

very low gradient near the site of the westernmost exposures of the pre-volcanic alluvial deposits north of 

Little Dry Creek. I assume that this site was near the 

margin of the Central Valley 10 m.y. ago, as it is today, 

and that the river was essentially graded to the local 

base level of that valley, with a gradient possibly as low 

asl m/km.

If the original late Miocene "base-level" gradient is 

taken as 1 m/km and the present gradient of the contact between the alluvium and the overlying lava flow is 

22.3 m/km at the same site, then the base-level plane, 

has been rotated from its near-horizontal position 

through an angle that would increase its slope by 21.3 

m/km (about 1.2°) (fig. 7). For purposes of calculation, the hinge line for the rotation is taken as the point 

at which the base-level plane intersects a plane defined 

by the upper conglomerate horizon of the lone Formation on Little Table Mountain about 1.5 km west of the 

westernmost outcrop of the late Miocene alluvium. 

Such a rotation, based upon tilting of the Sierra as a 

rigid block, results in an uplift of the site of the present 

drainage divide at Deadman Pass, some 100 km from 

the hinge line, of about 2,150 m, regardless of what the 

stream profile might have been like in the interior part 

of the range.

Subtracting uplift of 2,150 m from the present elevation of Deadman Pass (3,040 m) yields an elevation 

about 10 m.y. ago of about 900 m at the present drainBase-level plane: original slope=1m/km

Horizontal plane

-100.7 kmHinge line 

south of Friant

VERTICAL EXAGGERATION X 10 Deadman 

Pass

FIGURE 7.—Uplift of Sierran drainage divide at Deadman Pass calculated by rotation of late Miocene base-level plane, assuming tilting 

as a rigid block.
14 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

age divide. Mount Ritter, some 6 km to the west and 

the highest peak in the area, would have had an elevation of about 2,000 m, not allowing for post-10-m.y. 

erosion.

This calculated amount of uplift is considered to be a 

maximum for at least two reasons. Any increase allowed for the original gradient of the lO-m.y.-old baselevel plane would lessen the amount of uplift necessary 

to rotate that plane into its present position (by about 

100 m for each m/km increase in original gradient). 

Also, the concept of tilting the Sierra as a rigid block 

is, of course, only a first approximation. Any tendency 

for broad doming rather than simple tilt in the region 

of the Sierra crest would result in a convex-upward 

warping of the base-level plane in which the rotation 

measured at the hinge line would decrease eastward, 

resulting in less uplift at the crest than that calculated. 

Subtracting a lesser amount of uplift from the present 

elevation would mean the Deadman Pass region was at 

a correspondingly higher elevation 10 m.y. ago.

The amount of uplift calculated above does not depend upon reconstruction of the longitudinal profile of 

the lO-m.y.-old San Joaquin River within the interior of 

the range. However, such a reconstruction provides additional constraints on the amount of uplift and is particularly instructive because reconstruction of the 

trachyandesite lava-flow geometry in this study provides more realistic estimates of both original and 

present slopes of at least parts of the 10-m.y.-old profile than those used by Christensen (1966).

I started with the assumption discussed above that 

the gradient of the river 10 m.y. ago was about 1 m/km 

where it entered the Central Valley. Data from the base 

of the trachyandesite lava flow indicate that the gradient increased to about 6 m/km some 24 km to the 

east in the vicinity of Squaw Leap (fig. 5); this is the 

easternmost empirically determined value. Longitudinal stream profiles are normally concave upward and increase in gradient headward, except for reversals 

caused by anomalous streambed conditions or structural factors, and I would expect the San Joaquin River 

to do likewise, at least within the Sierran structural 

block. At a minimum, then, the profile would reach an 

elevation of 650 m at the site of Deadman Pass if projected eastward from Squaw Leap with no increase in 

gradient (fig. 8). When rotated to reflect the present 

gradient of the profile at Squaw Leap, the profile elevation at Deadman Pass, 2150 m higher, would be at 2800 

m. This projection places the profile lower than the actual surface within which the inner canyon was incised 

in response to later uplift of the range and indicates 

that the lO-m.y.-old stream profile must have increased 

in gradient eastward from Squaw Leap.

The lO-m.y.-old profile should probably have a present elevation closer to 3,050 m at Deadman Pass if the 

channel south of Deadman Pass, filled with 3.2-m.y.- 

old basalt, mostly represents incision below the 10- 

m.y.-old profile (see fig. 14). I think that condition is 

reasonable because although uplift began before 10 

m.y. ago, canyon incision would be accelerated by the 

increased rate of uplift after 10 m.y. ago. To reach 

3,050 m would require the stream profile to climb an 

additional 225 m east of Squaw Leap beyond the level 

reached by a projection assuming no increase in gradient. This would amount to an increase in average 

gradient east of Squaw Leap of 2.9 m/km for an average original gradient of 8.6 m/km between Squaw 

Leap and Deadman Pass. The actual stream gradients 

measured along the stream channel would be appreciably less than these projected values that ignore additional stream length due to meanders. The average projected gradient for the entire reach between Friant and 

Deadman Pass would be about 7.4 m/km as compared 

with 14.6 m/km for the 3.2-m.y.-old profile and 22.9 

m/km for the profile of the present San Joaquin River 

(see fig. 13).

I do not have a fully satisfactory method of testing 

the reasonableness of this reconstructed profile for 10 

m.y. ago, particularly inasmuch as it totally ignores 

that part of the stream profile east of Deadman Pass, 

which, as I will suggest in a later section, may well have 

had a lower gradient. However, it does fit the general 

pre-uplift physiographic setting, in which case a post10-m.y. uplift of about 2150 m (7050 ft) appears to be 

compatible with that setting, and I shall use this figure 

for further calculations.

If my interpretation of the present elevation of the 

lO-m.y.-old stream profile as being at about 3050 m at 

Deadman Pass is reasonable, it puts constraints on the

VERTICAL EXAGGERATION

FIGURE 8.— Reconstruction of lO-m.y.-old profile of upper San Joaquin River projected to vertical plane striking N. 40° E. Elevation 

drop of 730 m between Deadman Pass and hinge line allows for increase in gradient east from Squaw Leap whereas 500-m drop does 

not.
UPLIFT AND TILTING OF THE CENTRAL SIERRA NEVADA 15

model of tilting. The present position of the profile is 

the sum of pre-10-m.y. elevation and post-10-m.y. uplift. Uplift involving warping of the profile (and consequently the base-level plane) would require the profile to reach its present elevation at Deadman Pass 

from a greater original height, that is, with less uplift 

than that calculated for the rigid-block model (fig. 9). 

However, the higher original elevation for the profile at 

Deadman Pass would require a higher average stream 

gradient westward from there to the Central Valley 10 

m.y. ago. For example, if the amount of post-10-m.y. 

uplift was two-thirds of that calculated for the rigidMETERS

900 Original elevation

Base-level plane

|- 3050 After uplift 

2150 Uplift

A. Uplift by rigid-block model

1620 Original elevation

Base-level plane

3050 After uplift

1430 Uplift

B. Uplift by warped-block model

FIGURE 9.—Differences in uplift and tilt of central Sierra Nevada. Elevation of 10-m.y.-old stream profile is assumed to be 3050 m at 

Deadman Pass. Vertical scale and curvatures greatly exaggerated 

to emphasize differences. A, Rigid-block model. B, Warpedblock model. Uplift for warped-block model arbitrarily reduced by 

one-third from that calculated for rigid-block model.

block model, both the elevation at Deadman Pass and 

he average stream gradient 10 m.y. ago would be 

nearly double that calculated herein. In fact the gradient would be equal to that calculated for the 3.2- 

m.y.-old stream profile, and the amount of uplift would 

be only slightly greater than the amount of pre-10-m.y. 

uplift to be calculated in the next section. This example 

is undoubtedly too extreme and does not negate the 

possibility of some warping of the tilted block and consequently some reduction in the amount of uplift required. I believe such reduction, however, to be small 

relative to the total uplift calculated and will ignore it 

in further calculations realizing that my uplift calculations probably represent maximum values requiring 

some undetermined correction factor.

The 10-m.y.-old stream profile for the San Joaquin 

River as reconstructed in this report differs from that 

of Christensen (1966), particularly in its upper reach, 

a difference that highlights the problems in estimating 

uplift from profiles reconstructed without some control 

at the upper end. The westernmost segments of the two 

reconstructions have similar average gradients, and 

both profiles intersect the basalt knob at Sugarloaf Hill 

in Jose Basin, fortuitously in mine and by design in 

his, as he accepted Dalrymple's (1963) and Wahrhaftig's (I965a; 1965b) correlation of that basalt with the 

trachyandesite of Kennedy Table. For the segment east 

of Jose Basin, however, my reconstructed profile continues to increase in gradient while Christensen's decreases abruptly from an average of 26.5 m/km to an 

average 17 m/km, the latter gradient adopted from 

Matthes' (i960) "Pliocene" profile, even though he 

recognized that Matthes' profile in the western reach 

does not coincide with thelO-m.y.-old profile being reconstructed ("Pliocene" of Matthes would probably fall 

within the late Miocene of current usage). Christensen 

(1966, p. 169) then concluded that this change in gradient "may represent a warp along the western margin 

of the range, a departure from the rigid tilting to the 

north," a situation for which there is considerable evidence further south.

Christensen's gradient of 17 m/km is unrealistically 

low, however, as it produces a profile that intersects 

bedrock in the present streambed about 11 km (projected distance) west of Deadman Pass, an impossible 

situation if the lO-m.y.-old San Joaquin River headed 

east of Deadman Pass, as I believe I have adequately 

demonstrated. Any realistic profile reconstruction, 

therefore, must not only clear pre-volcanic bedrock at 

Deadman Pass, but also must allow for channel 

downcutting between 10 and 3+ m.y. ago, as I have attempted to show in my reconstruction. I do not imply 

that there was no warping of the 10-m.y.-old profile 

during uplift of the range, even though none is shown
16 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

in my reconstruction, but only that the elevation of any 

reconstructed profile must be constrained by physiographic considerations, past and present, in the Deadman Pass area. As a matter of fact, a flattening of the 

profile in the Deadman Pass area would simplify relations between the Sierran block and the area to the 

east, as discussed elsewhere in this report, but I have 

not been able to devise a method to determine how 

much warping might be reasonable.

Christensen's use of an overly low gradient for the 

present position of the lO-m.y.-old profile would naturally result in a low uplift estimate by his method, but 

his concurrent use of unrealistically low initial gradients partially compensates. His minimum estimated 

initial gradient of an average 1.06 m/km for the entire 

reach from Friant to the crest (Christensen, 1966, 

table l) is virtually identical to that used for the baselevel plane in this study. Because the average gradient 

of his uplifted profile is nearly as great as the amount 

of base-level tilt in this study, his maximum uplift estimate of 2070 m (6800 ft) approaches that calculated 

herein.

PRE-LATE MIOCENE UPLIFT

Several lines of evidence point to considerable uplift 

of the central Sierra Nevada prior to 10 m.y. ago. The 

reconstructed San Joaquin River profile of 10 m.y. ago 

drops roughly 750 m in the 100 km between Deadman 

Pass and the Central Valley. As local relief was more 

than 1000 m within the proto-Sierra Nevada being 

traversed, appreciable incision of the stream is indicated by that time (see fig. 13). Similar relief characterizes the terrane over which the 9-m.y.-old Eureka 

Valley Tuff was deposited in the Tuolumne River drainage basin to the north (N. K. Huber, mapping in progress, 1979). It is difficult to imagine such a gradient 

and incision for a reach of stream graded to a local 

base level unless some sort of stream rejuvenation, 

such as uplift, had taken place. The fact that the 

Eocene lone Formation west of Friant has a greater 

present dip than the trachyandesite lava flow also 

suggests appreciable uplift of the Sierra before 10 m.y. 

ago and provides a means of estimating the amount of 

that uplift.

Calculations in the previous section result in estimates of perhaps 2150 m of uplift at Deadman Pass on 

the Sierran divide since about 10 m.y. ago, utilizing a 

base-level plane derived from the trachyandesite of 

Kennedy Table and the underlying alluvial deposits. 

The westernmost exposure of these deposits is on strike 

with exposures of the lone Formation of Eocene age. 

The lone Formation, which forms the cuesta of Little 

Table Mountain( fig. 3), is armored by a resistant conglomerate horizon, and reconstruction from remnants

of that horizon yields a plane dipping 35 m/km in a S. 

40° W. direction, the same direction determined for the 

dip of the trachyandesite. This plane has a gradient 12.7 

m/km greater than that of the late Miocene deposits 

and indicates a significant amount of tilting at the 

margin of the Central Valley between deposition of the 

two formations. The absolute age of the lone Formation 

has not been established, but if a correlation with the 

Domengine Formation and the Ulatisian foraminifer 

stage is accepted (Repenning, I960), then its age is 

probably about 50 m.y. (Brabb and others, 1977, fig. 

2). The lone Formation thus serves as a stratigraphic 

plane about five times as old as the trachyandesite. 

This age is not critical to determining the amount of 

pre-10-m.y. uplift, only the timing and rate.

The stratigraphic plane defined by the lone Formation can only be reconstructed over a dip-distance of a 

little more than 3 km. Thus projection of this plane 

eastward into the Sierra is considerably more speculative than that for the trachyandesite. The difference in 

dip for the two planes suggests an uplift at Deadman 

Pass of about 1300 m during the 40 m.y. or so between 

deposition of the lone Formation and eruption of the 

trachyandesite, again on the basis of tilting as a rigid 

block. The initial dip for the lone Formation at this locality cannot easily be determined, and because of 

other uncertainties, this amount of uplift should be 

viewed as no more than a gross estimate. This amount 

probably should also be viewed as a maximum value 

inasmuch as there is some evidence for flexure along 

the east margin of the Central Valley farther north (D. 

E. Marchand, written commun., 1979). Therefore, dips 

on the lone Formation near Friant and elsewhere 

should be viewed in that context, and projections of 

such dips toward the range crest could be considerably 

in error. Nevertheless, the data suggest that considerable uplift, perhaps an amount as much as half of the 

post-10-m.y. uplift, took place before 10 m.y. ago. The 

total post-lone uplift would then be about 3450 m.

Marchand and Allwardt (1980, in press), in summarizing the Tertiary stratigraphy for the northeastern 

San Joaquin Valley, noted that the lone, Valley 

Springs, Mehrten, and Laguna Formations dip southwest at successively lower gradients, and they concluded that this represents deformation closely related 

to tectonic events in the Sierra Nevada. The age of the 

trachyandesite of Kennedy Table is similar to that of 

the Table Mountain Latite near Sonora, about 9.2 m.y. 

(recalculated from Dalrymple, 1964); the latite is 

within the Mehrten Formation as here used. Thus, gradient data for the Valley Springs Formation, at about 

20 to 23 m.y., would be useful. Unfortunately, reliable 

data do not seem to be readily available.

Marchand and Allwardt (1980, in press, table l) give
UPLIFT AND TILTING OF THE CENTRAL SIERRA NEVADA 17

"gradients" of 17.7 m/km andl8.9 m/km for the Valley 

Springs and Mehrten Formations along the Merced 

River some 50 km northwest of Friant. The Mehrten 

slope is from Arkley (1962), who does not state how it 

was obtained, and the Valley Springs figure is for the 

reconstructed eroded surface of the Valley Springs 

Formation rather than on a stratigraphic horizon that 

might help reconstruct primary dip (D. E. Marchand, 

oral commun., 1979). If the present slope of the Valley 

Springs and Mehrten Formations even approached 

being similar, that fact would suggest that the Sierra 

Nevada was tectonically relatively quiet between 20 and 

10 m.y. ago. Grant, McCleary, andBlum (1977, table l) 

present data from the Mokelumne drainage, an additional 50 km farther northwest, indicating similar dips 

for the Valley Springs and Mehrten Formations in that 

locality, but as they do not indicate how the data were 

obtained or what parts of the formations are represented, the significance of their data is uncertain. In 

summary, although the statigraphic data are equivocal, 

they suggest not only that pre-late Miocene uplift of the 

Sierra Nevada was significant, but that the uplift resulting in the present elevation of the range began before 10 m.y. ago.

TIMING OF POST-IATE MIOCENE UPLIFT

The preceding sections developed the thesis that most 

of the present elevation of the central Sierra Nevada 

resulted from uplift that occurred later than 10 m.y. 

ago, although it began earlier. Dalrymple (1964) was 

the first to propose that a major part of the incision of 

the inner canyon of the San Joaquin River took place 

before about 3.6 m.y. ago; he based his conclusion on 

several K-Ar age determinations on basalt that cascaded into the canyon. Inasmuch as the canyon grew in 

response to accelerated uplift of the range in the late 

Cenozoic, it is clear that by 3.6 m.y. ago uplift had not 

only begun but was of sufficient magnitude to permit 

cutting the canyon to more than half of its present 

depth below the river's profile of 10 m.y. ago (see figs. 

13 and 14). It should be kept in mind that present 

basalt outcrops are erosional remnants on the canyon 

walls and only provide a minimum figure for the depth 

of the canyon at the time of their eruption. Two of the 

basalts shown within the canyon and on the upland surface in figure 14 have been dated: 3.6 m.y. near Pine 

Flat and 3.4 m.y. near Snake Meadow (Dalrymple, 

1964). All of these basalt flows (excluding that at 

Deadman Pass, discussed later) are assumed to be of 

approximately the same age; except for late Pleistocene 

basalt, such as at the Devils Postpile, all seven basalt 

flows that have been dated in the upper San Joaquin 

drainage basin have ages from 3.4-3.9 m.y., all have

similar physiographic settings, and all probably are 

part of a discrete eruptive cycle.

Some additional control on the timing of uplift and 

tilting can be obtained from Pliocene gravel deposits in 

the Central Valley that occur both north and south of 

the San Joaquin River. The China Hat Gravel Member, 

a remnant of an alluvial fan deposit south of the 

Merced River, is considered by Marchand and Allwardt 

(1980, in press) to be "the uppermost member of the 

upper unit of the Laguna Formation." They believe the 

Laguna Formation to be of late Pliocene age from 

stratigraphic and paleontological data. It unconformably overlies the Mehrten Formation, is truncated by the 

North Merced pediment of latest Pliocene or earliest 

Pleistocene age, and contains a vertebrate fauna of 

latest Hemphillian age, possibly transitional into Blancan (Marchand and Allwardt, 1980, in press). South of 

the Merced River, the China Hat Gravel Member slopes 

southwest at about 10.5 m/km, half the gradient of the 

Mehrten at 18.9 m/km (Marchand and Allwardt, 1980, 

in press, table l); this slope suggests appreciable tilting between deposition of the two units.

On the north side of the Kings River, where it enters 

the Central Valley, there are several erosional remnants that Macdonald (1941) mapped as a"high terrace" 

deposit. The deposit originally covered a broad area 

there, and perhaps it is more properly an alluvial fan 

than a terrace. Segments of the present surface of the 

largest remnant, on Kirkman Hill north of Centerville, 

appear to approximate the plane of the original surface, which slopes westward at about 13.2 m/km. This 

slope is only slightly greater than that for the China 

Hat Gravel Member south of the Merced River, and the 

two deposits may be correlative in age. The coarseness 

of the two gravels in comparison to all younger deposits is another basis for possible correlation ( D. E. 

Marchand, written commun., 1979).

The surface of the fan north of the Kings River is 

mantled with abundant basalt and dacite pebbles and 

cobbles although they appear to be absent from 

stratigraphically lower parts of the deposit. In a count 

of all pebbles and cobbles 3 cm and larger on a surface 

of 10 m2 , more than 50 percent were of Cenozoic volcanic rock; basalt was somewhat more abundant than 

dacite and andesite combined. This result shows that 

during the final period of active deposition on the fan, 

before its tilting and incision, late Cenozoic volcanic 

rocks made up a large proportion of the stream bedload, presumably during and shortly after the eruption 

of these rocks somewhat more than 3 m.y. ago.

A dacite cobble collected from the surface of the fan 

has been dated at 4.0 m.y. (table l) so the uppermost 

depositional surface of the fan could be no older than 

that. The dacite cobble is petrologically similar to da-
18 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

cite exposed at Windy Peak on the Middle Fork Kings 

River in the Marion Peak quadrangle (Moore, 1978), 

for which ages of 4.4 and 4.5 m.y. have been obtained 

(table 1). A slightly younger limit for the age of the active fan is derived from a basalt cobble collected from 

the fan surface and dated at 3.8 m.y. (tablel).

The only other age determinations for volcanic rocks 

in the Kings River drainage basin of which I am aware 

are 3.4 m.y. for an andesite at Stony Flat on Mill Creek 

(table 1; Moore and others, 1979) and 3.2 m.y. for a 

basalt at Rancheria Creek, tributary to the North Fork 

Kings River (table l). The latter area is probably the 

site of what was the largest volume of 3- to 4-m.y.-old 

volcanic rocks in the Kings River drainage basin and 

could have been the major source area for most of the 

basalt cobbles on the fan at Kirkman Hill. If so, these 

dates provide a maximum age of about 3.2 m.y. for the 

active Kirkman Hill fan.

Arkley (1962) estimated an original gradient for the 

China Hat Gravel Member of 3.8 m/km. If a similar 

original gradient is assumed for the fan north of the 

Kings River, then this fan has been tilted by about 9.4 

m/km to reach its present slope, presumably during 

the past 3 m.y. or so. Assuming that a similar amount 

of tilt during the same interval took place on the San 

Joaquin River some 27 km to the northwest, the calculated resultant uplift at Deadman Pass is about 950 m, 

or about 45 percent of the total post-10-m.y. uplift of 

2150 ml have inferred above.

Along the Merced River, gradients of reconstructed 

depositional or erosional surfaces associated with late 

Tertiary and Quaternary deposits consistently decrease 

with decreasing age; such gradients suggest continuing 

uplift and tilt up to the present time (Marchand, 1977, 

p. 39 and table A; Marchand and Allwardt, 1980, in 

press, table l).

Along the upper San Joaquin River, the 0.6-m.y.-old 

Friant Pumice Member of the Turlock Lake Formation 

provides the only radiometrically dated Pleistocene unit 

of stratigraphic usefulness (Janda, 1965, 1966). Reconstruction from scattered outcrops yields a 

"minimum average slope" of 2.75 m/km for this unit 

(Janda, 1966, p. 237) at the present time in the Friant 

area. The fine ash appears to have been deposited on a 

flood plain with a low gradient; for purposes of calculation I am assuming that the original gradient did not 

exceed 1 m/km, as I assumed for the ll-m.y.-old 

pumice deposit. This results in a post-depositional tilt 

of 1.75 m/km, which translates into 175 m of uplift at 

Deadman Pass in the last 600,000 years. This amount 

of uplift, which is roughly one-fifth of the 950 m of 

post-3-m.y. uplift calculated above, would have taken 

place during about one-fifth of the elapsed time and 

thus supports the concept of continued uplift at a fairly 

uniform rate.

SUMMARY OF UPLIFT HISTORY

The meager geologic control for reconstruction of 

Sierran uplift makes estimation of uplift amounts difficult, and calculation of uplift rates is of uncertain validity. Some of the conclusions derived in this study are 

based on assumptions that are difficult or impossible to 

verify, and I hope that I have qualified them accordingly. Though I have not attempted to place error estimates on my uplift data, I suggest that they probably 

represent maximum values that will decrease with departure from the rigid-block tilt model.

Slemmons, Van Wormer, Bell, and Silberman (1979) 

recently presented uplift estimates for the Carson 

Pass-Sonora Pass area of the north-central Sierra 

Nevada, centered about 55 km north of Deadman Pass. 

Although most of their estimates include a range of 

values, their data are difficult to evaluate as there is no 

indication as to how they were obtained or what the 

range signifies. In an earlier study Slemmons (1953) 

estimated various amounts of tilt determined largely 

from reconstructed stream profiles correlated with volcanic episodes, and these estimates probably form the 

basis for the more recent uplift estimates. Uplift estimates based on tilt depend, of course, on distance from 

an assumed hinge line, and thus they will vary from 

place to place within the mountain range. The estimates of uplift for the Carson Pass-Sonora Pass area, 

therefore, may not represent sequential events at a 

given site, a necessary requirement if sequential uplift 

rates are to be determined. Nevertheless, it is instructive to compare their data with that for Deadman Pass 

in an attempt to develop an overall uplift history.

Uplift estimates plotted against time produce strikingly similar curves for the Carson Pass-Sonora Pass 

area and the Deadman Pass area, differing chiefly in 

magnitude and rate of uplift (figs. 10 and 11). These 

"smooth" uplift curves should probably have perturbations in uplift that are reflected by various erosion 

stages or surfaces within the Sierra and pulses of 

sedimentation in the Central Valley, but these perturbations cannot be discerned with the available data. 

The curves indicate that uplift of the central Sierra 

Nevada was well underway 10 m.y. ago, having begun 

perhaps more than 25 m.y. ago. Uplift began slowly 

and has increased in rate more or less continuously to 

the present, although the sparseness of data may conceal fluctuations. Data from the Carson Pass-Sonora 

Pass area suggest an increase in average rate of uplift 

from about 0.02 mm/yr, 25 m.y. ago, to about 0.16 

mm/yr at present. The data for the Deadman Pass area 

suggest that the average rate of uplift in that area underwent a greater increase from about 0.03 mm/yr, 25 

m.y. ago, to about 0.35 mm/yr at present. The total 

amount of uplift increases from an estimated 2000 m in
DIFFERENTIAL UPLIFT AND THE EASTERN ESCARPMENT 19

the Carson Pass-Sonora Pass region to perhaps as 

much as 3450 m in the Deadman Pass area. Uplift undoubtedly was even greater farther south in the Mount 

Whitney area, but late Cenozoic stratigraphic markers 

are not available for similar calculations in that area.

If the uplift curves in figures 10 and 11 have even 

qualitative validity, they indicate that the Sierra 

Nevada is still rising, and at a possibly increasing rate.

DIFFERENTIAL UPLIFT 

AND THE EASTERN ESCARPMENT

Matthes (l930b, I960) was the first to conclude from 

his study of stream profiles and upland erosion surfaces that during the late Tertiary a major fork 

(perhaps the main channel) of the San Joaquin River 

had its source east of the present drainage divide, and 

he believed that it was beheaded by the formation of a 

fault escarpment on the east side of that divide. Pumice 

pebbles and cobbles that must have been derived from 

east of the present Sierran divide occur in lO-m.y.-old 

alluvial deposits at the margin of the Central Valley 

and confirm that the San Joaquin River flowed across 

the site of the present divide at that time. Erwin (1934) 

apparently accepted the concept of a throughgoing 

drainage in this locality, and he suggested that the 

basalt exposed locally on the San Joaquin Mountain 

ridge may have flowed down this ancient drainage and 

was later uplifted along the fault-bounded range front. 

Subsequent mapping has delineated the probable location of such a basalt-filled channel just south of Deadman Pass (Huber and Rinehart, 1965; 1967). This 

3.2-m.y.-old basalt, slightly younger quartz latite, the 

0.7-m.y.-old Bishop Tuff and related rocks, the rhyolite 

of the Mono Craters, and extensive alluvial and lacusfc 5oo

z

"1000

Q

61500

Q

Z

uj2000

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£3000

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D 3500

EXPLANATION

- Uplift at Deadman Pass

• — — Uplift in Carson PassSonora Pass area

50 45 40 35 30 25 20 15 10 5 

TIME, IN MILLIONS OF YEARS BEFORE PRESENT

FIGURE 10.—Uplift of crest of central Sierra Nevada at Deadman Pass 

and in Carson Pass-Sonora Pass area. Data for Carson Pass-Sonora 

Pass area were presented as a range in uplift or time (Slemmons 

and other, 1979); dashed line represents an arbitrary average.

trine deposits in the Mono Lake basin now cover much of 

the area that might have drained into the older San 

Joaquin River. If this drainage area found a new outlet, 

it most likely drained southward into Owens Valley.

The Long Valley and Mono Valley structural basins 

now interrupt the continuity of pre-existing volcanic 

strata, and the area between these basins and that to 

the east is broken by numerous faults and warps (Gilbert, 1941; Gilbert and others, 1968; Krauskopf and 

Bateman, 1977; Bailey and Koeppen, 1977) that document considerable deformation of the volcanic rocks. In 

spite of this deformation, segments of a surface 11 m.y. 

old or older can be reconstructed from scattered outcrops of welded tuff (fig. 4). The base of the westernmost outcrops of tuff of this age mapped east of 

Mono Lake lies at about 2135 to 2195 m (Gilbert and 

others, 1968). Ten kilometers to the south, similar tuff 

lies at about 2135 m in the northwest corner of the 

Glass Mountain quadrangle (Krauskopf and Bateman, 

1977). Another 30 km to the southwest, Bailey and 

Koeppen (1977) mapped a small area of welded tuff 

(welded tuff of Alpers Canyon) at about 2195 m elevation on the north side of Long Valley caldera; this tuff 

was recently dated at 11 m.y. (table l). The latter tuff is 

rhyolite whereas the tuffs to the northeast are quartz 

latite; thus these tuffs are not all parts of a single eruptive sheet. Nevertheless, the tuffs collectively define 

parts of a surface of moderate relief that existed about 

11 m.y. ago, and although this surface has since been 

badly faulted and disrupted, the area east of this part 

of the Sierran escarpment appears to have acted independently of the Sierran block and in particular has 

not been a part of the westward tilting of that block.

.40 

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EXPLANATION

Rate of uplift at Deadman Pass

Rate of uplift in Carson 

Pass-Sonora Pass area

30 25 20 15 10 5 

TIME, IN MILLIONS OF YEARS BEFORE PRESENT

FIGURE 11.—Rate of uplift of crest of central Sierra Nevada at Deadman Pass and in Carson Pass-Sonora Pass area. Curves based on 

graphic differentiation of uplift curves in figure 10.
20 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

Displacement along the east boundary of the Sierran 

block is commonly distributed over a series of subparallel faults. In the Deadman Pass area, the two most 

important of these are the Hartley Springs fault and an 

unnamed fault about 2 km east of Deadman Pass (fig. 

12). The Hartley Springs fault, the best documented, 

displaces 3.2-m.y.-old basalt down to the east by 450 m 

and the 0.7-m.y.-old Bishop Tuff by about 300 m 

(Bailey and others, 1976). However, for the speculative 

calculations that follow, I shall assume that the westernmost of these two faults marks the boundary of the 

Sierran block and that all the cumulative displacement 

occurred on it.

Using methods described above, I have calculated the 

total post-10-m.y. uplift of the range at the site of the 

unnamed fault east of Deadman Pass at about 2200 m. 

Projection of the 10-m.y. elevation of the stream profile 

at Deadman Pass (900 m) 2 km farther northeast 

yields a pre-uplift elevation of about 920 m at this site. 

Projected 13 km farther northeast, the profile 10 m.y. 

ago would have an elevation of about 1100 m at the location of the welded tuff of Alpers Canyon north of 

Long Valley caldera, and the tuff itself would have been 

at a similar elevation or higher, depending on its topographic setting relative to the San Joaquin River. 

Subtracting a minimum value of 1100 m from the present elevation of 2200 m for the tuff results in a 

maximum value of 1100 m for post-10-m.y. uplift of the 

tuff. Over the past 10 m.y., then, the Sierran block has 

been uplifted 2200 m at the site of the frontal fault east 

of Deadman Pass, the area immediately to the east has 

been uplifted a maximum of 1100 m, and displacement 

on the fault(s) is a minimum of 1100 m. This conclusion 

has only local validity, if any, because much of the area 

east of the Sierra Nevada has reacted to tectonism as a 

maze of independent blocks.

When did displacement on the frontal faults in the 

Deadman Pass area begin? If I extrapolate already 

speculative calculations, I can come up with some 

bounding limits. If I assume that 55 percent of the total 

post-10-m.y. uplift occurred before 3 m.y. ago, then the 

San Joaquin River profile at the site of the frontal fault 

would have an elevation of 2100 m at about 3 m.y. ago, 

nearly as high as the present elevation of the welded 

tuff of Alpers Canyon some 13 km to the east and upstream. The tuff would therefore have been near or 

above its present elevation 3 m.y. ago. As the Sierran 

block was subsequently uplifted an additional 1000 m at 

the site of the frontal fault, while the tuff remained at 

approximately the same elevation it was 3 m.y. ago, 

displacement on the frontal fault system must have 

begun sometime about 3 m.y. ago. That displacement 

on this system began before 0.7 m.y. ago is indicated 

by greater displacement of 3.2-m.y.-old basalt than of 

the Bishop Tuff on the Hartley Springs fault strand.

I Mono Craters J 

V / 

/

(• II

Deadman 

Pass Jr

LONG VALLEY 

CALDERA

/

Round Valley

P#

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/

10 20 KILOMETERS

FIGURE 12.— Major faults east of Deadman Pass in Long Valley-Mono 

basin area. Bar and ball on downthrown side of fault. Dotted lines 

represent extent of Mono Craters ring structure and Long Valley 

caldera. After Bailey and others (1976).
INCISION OF THE SAN JOAQUIN CANYON 21

The 1100 m calculated as if all displacement took 

place at the frontal fault just east of Deadman Pass is a 

minimum value tied to uplift calculations, and it is undoubtedly less than the cumulative displacement on 

faults in the frontal system. Nevertheless, 300 m of 

post-Bishop Tuff displacement on the Hartley Springs 

strand in less than the last 0.7 m.y., a significant part 

of the total, suggests that the rate of fault displacement is being maintained or even increased. Caution 

must be used in attempting to tie all of this to continued rates of Sierran uplift, however, as the area east 

of Deadman Pass may be undergoing some downward 

adjustment in the absolute sense.

If these speculations are approximately correct, they 

suggest that the area immediately east of Deadman 

Pass was uplifted as part of the Sierran block until 

about 3 m.y. ago, after which it broke free and remained behind as the Sierran block continued to rise. It 

is possible that the eastern area followed, but at a 

lower rate, and then underwent some later downward 

displacement in the absolute sense. Matthes (l930a, p. 

29) noted these possibilities when he stated that 

"Owens Valley and the other desert regions adjoining 

the range on the east and south dropped back or else 

suffered but slight uplifts as compared with the mountain block."

The Deadman Pass area is atypical of much of the 

eastern Sierran escarpment, located as it is in an embayment within the Sierran block with a relatively 

broad area of moderate relief to the northeast, and my 

calculations cannot readily be extended to other parts 

of the escarpment. To the southeast in Owens Valley, 

for example, displacement on the frontal fault system is 

much greater, is concentrated in a narrower zone, and 

probably began earlier than at Deadman Pass. Indeed, 

new radiometric data indicate that the southern Owens 

Valley basin was forming at least 6 m. y. ago (Bacon 

and others, 1979; Giovannetti, 1979), although its development probably also lagged behind initial uplift of 

the Sierran block. Downfaulting of the Owens Valley 

graben in the absolute sense also was more important, 

inasmuch as buried bedrock surfaces are in places 

below sea level (von Huene and others, 1963; Bateman, 

1965).

INCISION OF THE SAN JOAQUIN CANYON

In its course down the west slope of the Sierra 

Nevada, the San Joaquin River flows in a canyon that 

has been deeply incised into a gentler upland erosion 

surface (figs. 13 and 14). Incision of the canyon was

METERS 

4000-

3000-

1000-

FEET 

14,000

^ 12,000

-10,000

-8000

-6000

-4000

-2000

EXPLANATION

* Elevation of prominent peak on either side of canyon

• Lowermost outcrop of Pliocene basalt

Profile of San Joaquin River 

© 3 m.y. old or older 

@ 10 m.y. old with no increase in gradient east

of Squaw Leap 

(D 10 m.y. old elevation of 3050 m (10,000 ft)

at Deadman Pass

A-J Location of cross section, figure 14

<o Trachyandesite lava flow, 

g> including projection east 

x of Squaw Leap

Stream turns 

into projected 

section

Fish Creek

T North Fork San Joaquin River 

Pine Flat 

Granite Creek

South Fork San Joaquin River 

Downstream limit of late Pleistocene glaciers 

Mammoth Pool Dam 

Downstream limit of Pleistocene glaciers

D E F G H I j

10 15 MILES

10

i 

15 20 KILOMETERS

FIGURE 13.—Longitudinal profile of San Joaquin River in Sierra Nevada, projected onto vertical plane striking N. 40° E. Reconstructed profiles

for late Miocene and Pliocene channels also shown.
22 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

NW

Deadman Quartz latite and Minaret 

" surficial materials Summit

SE

J @101 km

Basalt (3.2 m.y.)

Surficial materials

SW

Middle Fork 

San Joaquin River

Middle Fork Deadman

LONG VALLEY

CALDERA 

Son Joaquin River ^s — — — J — • — • — — x£3s«^^ Surficial materials

Basalt (3.2 m.y.)

I @ 99.8 km

NE

NW

Stairway 

Pass

H@ 88.5 km

Pumice

Tb

Middle Fork Quaternary basalt 

Son Joaquin River SE

Stairway 

NW Pass

G @ 85.3 km

Middle Fork Fish 

___Sgn cfooguin River Creek

VABM 

9302

SE

Projected from near Snake meadow 

1 km downstream from section

Nw Granite Creek

__ basin

_

Tb

Cattle 

Mountain Son Joaquin River

Tb

SE

FIGURE 14.—See description on opposite page.
INCISION OF THE SAN JOAQUIN CANYON 23

NW

Tb

Jackass 

Rock

E @ 67.6 km

NW

Shuteye Peak Kaiser Ridge

Musick Mountain

Mile High 

Curve Son Joaquin River

NW

C @ 41 km

Kennedy 

NW Table San Joaquin River

B @ 21.2 km

S.q"f"^ Trachyandesite SE

— 1000

— 800

— 600

—400 

r-200

NW Hulbert 

Mountain

Pincushion SE

Mountain 

San Joaquin River ^ Trachyandesitie

1234

KILOMETERS 

VERTICAL EXAGGERATION X 2.64

A @ 12.9 km

FIGURE 14.—Cross sections of San Joaquin River canyon in Sierra Nevada. Projected distances from hinge line indicated for each section (see 

fig. 13 for location). Section J is view of west face of Deadman Pass ridge and shows basalt-filled Pliocene channel crossing present divide 

south of Deadman Pass. On sections C through J, short-dash line indicates lO-m.y.-old Miocene stream profile reconstructed with no increase in gradient east of Squaw Leap; long-dash line profile with elevation of 3050 m (10,000 ft) at Deadman Pass. Actual profile assumed 

to lie between these lines. Section I shows fault with arrows showing direction of relative movement. Tb, Pliocene basalt.
24 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

presumably initiated by late Cenozoic uplift and westward tilting of the range, which significantly increased 

the gradient and rejuvenated the river. The 3.6-m.y. - 

old basalt that cascaded into the canyon near Pine Flat 

at the junction of the North and Middle Forks of the 

river indicates that a major part of the uplift and incision took place before its eruption. The amount of preand post-basalt uplift at this location can be estimated 

in a manner similar to that used at Deadman Pass assuming that 55 percent of the post-10-m.y. uplift occurred before about 3 m.y. ago when the Kings River fan 

was abandoned; the results are shown in table 3.

The basalt near Pine Flat also can be used to estimate 

the relative amount of channel downcutting during approximately the same time intervals (table 3). Such estimates utilize the lO-m.y.-old stream profile as reconstructed above. Because the lowest preserved outcrop 

of basalt in the canyon may not represent the lowest 

original extent, the 10-to-3.6-m.y. estimate of 

downcutting should be considered a minimum value 

and the post-3.6-m.y. estimate a maximum. Whereas 

the post-3.6-m.y. estimate results from a direct measurement between the basalt elevation and the present 

canyon bottom, the pre-3.6-m.y. estimate depends 

upon the accuracy of the reconstruction of the 10- 

m.y.-old stream profile.

Schumm (1963), in his study of rates of orogeny and 

denudation, pointed out that denudation following uplift takes place by two processes, channel incision and 

hillslope erosion. The first process may be rapid 

enough to keep up with uplift, but the second is much 

less likely to lower interfluvial areas at the same pace. 

Slow uplift may allow landforms to remain in an 

equilibrium state, but a range of faster uplift rates in 

relation to denudation will allow channel cutting to 

dominate the erosional regime. In particular, "when 

rocks are very resistant, channel incision will be relatively much greater than hillslope erosion and a narrow 

canyon is formed" (Schumm, 1963, p. 12). Incision of 

the San Joaquin canyon appears to follow this pattern,

as broad, slightly eroded upland surfaces still remain.

After rejuvenation of a drainage basin by increase in 

overall gradient, the zone of maximum erosion migrates toward the head of the basin. As this occurs, 

stream profiles, gradients, and sediment yields will 

change accordingly, with increasing concavity of the 

profile migrating upstream (Schumm, 1977, p. 69-71). 

The results of this process are evident in the canyon of 

the San Joaquin River, as the lO-m.y.-old, 3-m.y.-old, 

and present stream profiles show successively greater 

concavity. For the interval 10-3 m.y., this change is reflected by differences in the ratio of downcutting to uplift as determined near Pine Flat and Deadman Pass 

(table 3). At Pine Flat the amount of downcutting is 

more than three-quarters that of uplift whereas at 

Deadman Pass it drops to less than half. The ratio of 

downcutting to uplift during this time interval continues to increase downstream from Pine Flat, but the 

reach with the maximum amount of downcutting or incision of the canyon probably is about 16 km west of 

Pine Flat below the junction of the South Fork; there 

an additional 1165 km2 is added to the drainage basin.

Both the amount of downcutting and the 

downcutting-uplift ratio decrease eastward from Pine 

Flat, but the pre-basalt channel near Deadman Pass 

still represents a significant incision below the preuplift surface, and the upstream end of the increase in 

gradient due to uplift must be to the east of Deadman 

Pass. As the 10- and 3-m.y. profiles are thus converging, simple eastward projection would cause them to 

intersect about 30 km east of Deadman Pass. However, 

I believe that both the 10-m.y. and 3-m.y. profiles 

should both decrease in slope east of Deadman Pass 

and merge into the gentler headwater drainage basin 

that once fed the river from beyond the area of appreciable tilt.

The beheading of the San Joaquin River about 3.2 

m.y. ago by the eruption of basalt into the river channel near Deadman Pass resulted in an abrupt and drastic change in stream dynamics downstream in the reTABLE 3.-Comparison of uplift, downcutting, and ratio of downcutting to uplift near Pine Flat and Deadman Pass

Near Pine Flat (78 km from hinge line)

Time 

span

10 m.y. to

About 3 m.y. ago

Total..,. _ ... _ ........ _ .......

(m)

....................... 900

.--——.-_-.—..-... 750

Uplift

(percent)

55 

45 

100

(m)

700 

260 

960

Downcutting

(percent)

73 

27

Too

Ratio of 

D/U 

( percent)

77 

35

(m)

1200 

950 

2150

Near Deadman Pass ( 100 km from hinge line)

Uplift

(percent)

55 

45

Too

(m)

490 

180 

670

Downcutting

(percent)

73 

27

Too

Ratio of 

D/U 

( percent)

40 

19

NOTES. —Assumptions for calculations:

For uplift: Total post-10-m.y. uplift is about 2150 m (7050 ft) at Deadman Pass and post-3-m.y. uplift is 45% of total. 

For downcutting: lO-m.y.-old stream profile now at about 3050 m (10,000 ft) at Deadman Pass.

Age differences between 3-m.y.-old fan, 3.6-m.y. basalt at Pine Flat, and 3.2-m.y. basalt at Deadman Pass are ignored.

Downcutting is of pre-Cenozoic bedrock and does not consider necessary removal of Pliocene and Pleistocene volcanic rock from canyon.
UPLIFT AND GLACIATION-SOME TIME CONSTRAINTS 25

maining part of the San Joaquin as well as a forced 

change in outlet for the drainage system remaining to 

the east. I think it likely that the headwater system 

soon breached what was probably a low divide on its 

southern side and was diverted into the Owens Valley 

drainage where it possibly was a factor in initiating increased discharge about this time into the OwensChina-Searles Lakes system (Smith, 1977; 1978a; 

1978b; Smith and others, 1980, in press).

An outlet from Mono Lake through Adobe Valley to 

Owens Valley existed during the Tahoe Glaciation 

(Putnam, 1950), and it is likely that such overflow occurred earlier whenever a lake of sufficient size existed 

in the Mono basin. Hubbs and Miller (1948, p. 79) concluded that the distribution of a distinctive fish fauna 

"calls for a former connection between the Lahontan 

and Death Valley flu vial-pluvial systems, and the most 

plausible route for such a connection is through the 

Mono basin" sometime in the past. Lake sediments 

near the east margin of Mono basin were deposited between 3 and 4 m.y. ago, according to radiometric dates 

on associated volcanic materials (Gilbert and others, 

1968, p. 290). Freshwater mollusks and fish collected 

from these sediments indicate external drainage for 

the basin at that time.

The present San Joaquin drainage basin upstream 

from Friant Dam has an area of 4340 km2 . The size of 

the area to the east that formerly contributed to the 

total San Joaquin discharge is unknown, but it could 

easily have been of equivalent size or larger. With the 

loss of this eastern area, the discharge at Friant was 

significantly reduced even though the eastern area may 

not have received as much precipitation as the Sierra 

block.

For the reach of the San Joaquin that we have been 

examining in some detail, however, the loss in discharge was even greater, as the drainage area upstream from Pine Flat was reduced from perhaps 4000 

km2 or more to about 455 km2 . The drainage area upstream from the location on the San Joaquin River west 

of Deadman Pass used for the downcutting estimate in 

table 3 would have been reduced to a mere 65 km2 .

The reduced erosive power of the stream resulting 

from reduced discharge should be reflected in reduced 

downcutting and a reduction in the ratio of downcutting to continued uplift, as indicated in table 3 for the 

past 3 m.y. period. However, the differences in preand post-3-m.y. data only partly reflect reduced stream 

discharge because other complicating factors are of 

considerable importance. The Pliocene basalt that disrupted the drainage must itself be removed from the 

pre-existing channel before downcutting into basement 

rock (which is what table 3 estimates) can continue. At 

Pine Flat the reach involved is not long and a great volume of basalt may not have been present, but a considerable volume of basalt must have filled the Middle 

Fork valley west of Deadman Pass. With the 

available discharge, roughly equivalent to that of today, removal of the basalt by stream erosion alone 

would have been slow and it is likely that it was only 

accomplished through glaciation. After the Sherwin 

Glaciation, somewhat more than 0.7 m.y. ago, downcutting was again interrupted when the Middle Fork valley 

was blocked by the eruption of the tuff of Reds Meadow 

and basalt of the Devils Postpile (Huber and Rinehart, 

1967; Bailey and Koeppen, 1977). These volcanic rocks 

were largely removed by subsequent glaciation, but locally the stream still flows over basalt, as at Rainbow 

Falls, and, at this locality, bedrock downcutting by the 

stream itself appears to be almost negligible at the 

present time.

With the competence of the beheaded San Joaquin 

River greatly reduced, glacial erosion thus must have 

been responsible both for removal of late Pliocene and 

Pleistocene volcanic rocks erupted into the river canyon 

and for most of the further downcutting of the canyon 

into pre-Cenozoic bedrock in the upper reaches of the 

drainage basin, including both the Pine Flat and 

Deadman Pass localities in table 3. The dominance of 

glacial over fluvial erosion is reflected in the greater 

tendency toward U-shaped valleys in the upper reaches 

and in the present stream profile. The present profile 

consists of two concave-upward segments interrupted 

by a convex segment in the vicinity of Mammoth Pool 

Dam (fig. 13). The convex segment marks the approximate downstream limit of glaciers in the main canyon 

during the Pleistocene, and I interpret the upstream 

concavity in the profile as reflecting glacial erosion 

superimposed upon fluvial erosion.

UPLIFT AND GIACIATIONSOME TIME CONSTRAINTS

Three major episodes of glaciation in the Sierra 

Nevada are recognized at the general latitude of Deadman Pass. In addition to the well-documented multiple 

sequence of late Pleistocene advances, these include 

the Sherwin, whose deposits are overlain by the 0.7- 

m.y.-old Bishop Tuff, and the McGee, which overlies 

2.7-m.y.-old basalt (Dalrymple, 1963; Dalrymple and 

others, 1965). A fourth and older episode, represented 

by the so-called Deadman Pass Till, which lies between 

volcanic units dated at 3.2 and 2.8 m.y. ago, has been 

proposed by Curry (1966, 1971). (All ages cited have 

been recalculated.)

Most workers have accepted a glacial origin for the 

lag deposit on McGee Mountain, about 24 km southeast of Deadman Pass, and for many years the McGee
26 LATE CENOZOIC UPLIFT AND TILT OF CENTRAL SIERRA NEVADA, CALIFORNIA

Till was widely regarded as the oldest known till in the 

eastern Sierra Nevada (Putnam,1962) although an absolute age for it still is far from established.

C. D. Rinehart and I mapped a lag deposit of unsorted debris in the saddle at Deadman Pass and referred to it as a glacial deposit (Huber and Rinehart, 

1965). We did not assign this deposit to any specific 

glaciation, but considered it to be pre-Wisconsin because of its physiographic position above the probable 

limits of glaciers in the San Joaquin drainage basin 

considered to be of Wisconsin age. We initially thought 

the lag deposit to be a till on the basis of a superficial 

examination of varied clasts, some of which we thought 

to have been derived from the topographically higher 

Ritter Range to the west, a likely source direction if 

they were transported by a glacier that filled the valley 

of the Middle Fork of the San Joaquin River. Curry 

(1966,1971) also thought that he recognized clasts derived from the west. The lag deposit overlies basalt 

dated at about 3.2 m.y. (Dalrymple, 1964), and it in 

turn was shown by Curry to be overlain by a quartzlatite flow dated at about 2.8 m.y. ago, and on this 

basis he concluded that there had been a glaciation in 

this part of the Sierra Nevada about 3 m.y. ago.

On a revisit to the Deadman Pass locality in 1978, I 

recognized that large clasts that I had previously 

thought to be of metavolcanic crystal tuff from the Ritter Range instead were of a distinctive hypabyssal intrusive rock with quartz and feldspar phenocrysts that 

crops out north of Deadman Pass on the east side of the 

San Joaquin Mountain ridge; Rinehart and I had included this intrusive rock with the quartz monzonite of 

Lee Vining Canyon on the geologic map of the Devils 

Postpile quadrangle (Huber and Rinehart, 1965). 

Other clasts on Deadman Pass and along the east side 

of the San Joaquin Mountain ridge, including vesicular 

basalt and Paleozoic metamorphic rocks, could be derived locally a short distance north of Deadman Pass; 

granitic clasts did not appear to be definitive and no 

Ritter Range rocks were positively identified. Patches 

of "Deadman Pass Till" mapped by Curry (1971) above 

the dated basalt on both the east and west flanks of the 

ridge south of Deadman Pass contain clasts similar to 

those at Deadman Pass; I could find no Ritter Range 

lithologies. Derivation of the clasts from the north 

rather than from the west would not appear to be compatible with a glacial origin for the lag deposit but 

perhaps would be compatible with some sort of a 

debris-flow origin; indeed Curry (1971) has described 

volcanic mudflow deposits (lahars) north of Deadman 

Pass. The origin of the lag deposit is thus uncertain.

A glacial deposit that Rinehart and I (Huber and 

Rinehart, 1965) mapped at the north end of the San 

Joaquin' Mountain ridge subsequently was included by

Curry (1971) in his "Deadman Pass Till." I revisited 

this locality in 1980 and recognized abundant clasts of 

metavolcanic breccia from the Ritter Range and 

granodiorite from the Thousand Island Lake basin; 

these clasts indicate derivation from the west. However, there is no evidence to suggest that this glacial 

deposit is older than the quartz latite and I consider it 

to be much younger, perhaps as young as Tahoe in age. 

If I am correct, then this glacial deposit has no bearing 

on the problem of the origin of the Deadman Pass deposit and need not be considered further in that 

context.

The uplift calculations in this report provide additional constraints for possible glacial episodes. Particularly significant is the conclusion that 3 m.y. ago the 

Sierra Nevada in the vicinity of Deadman Pass was 

about 950 m lower than now, leaving the site of Deadman Pass at about 2075 m and Mount Ritter at 3100 m. 

Is this elevation high enough to permit glaciation at 

that time?

Wahrhaftig and Birman (1965) reconstructed the extent of the mountain icecap during the Tahoe Glaciation and contoured the climatic firn limit, based on 

summit altitudes of lowest peaks to have had glaciers 

on their south-facing sides, which they place at about 

3350 m in the Deadman Pass-Ritter Range area. Under 

those conditions, Mount Ritter would not have been 

high enough to sustain glaciers 3 m.y. ago. Using a different parameter, the climatic snow line, the lower 

limit of perennial snow on fully exposed flat surfaces, 

now estimated to be at 4,500 m, was probably only 

about 750 m lower during the Wisconsin glacial 

maximum (Wahrhaftig and Birman, 1965), an amount 

less than the 950 m lower elevation of the range 3 m.y. 

ago. Thus even if climatic conditions were somewhat 

more severe 3 m.y. ago than during the Wisconsin 

Glaciation, elevations in the summit areas west of the 

Deadman Pass region were probably too low to produce 

other than marginal cirque glaciers, and a glaciation of 

the extent of the proposed Deadman Pass Glaciation 

appears unlikely. This conclusion is based on an uplift 

value near the maximum calculated. However, even 

using an uplift value 300 m less, about the minimum 

permitted by calculations based on stream profile reconstructions at Deadman Pass, or some value in between, elevations in the Deadman Pass area might still 

have been only marginal for glaciation 3 m.y. ago.

The deep-sea temperature record indicates global 

cold cycles centered around 2.5 and 1.5 m.y. ago 

(Beard, 1969), and a number of workers have 

suggested that perhaps the McGee Glaciation occurred 

during the cycle 1.5 m.y. ago (Cox, 1968; Birkeland and 

others, 1971). If the rate of post-3-m.y. uplift was 

reasonably uniform, the Sierra Nevada might still not
REFERENCES CITED 27

have been high enough to sustain major glaciation 2.5 

m.y. ago, but probably it would have been high enough 

1.5 m.y. ago, at least in the north-facing cirque area 

feeding into McGee Creek. Thus although my uplift 

calculations could preclude glaciation in the present vicinity of Deadman Pass 3 m.y. ago, they would not preclude the McGee Glaciation if it occurred 1.5 m.y. ago.

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