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STATE OF CmiFORNIA
DEPABTMENT OF NATUBAL RESOURCES
GEOLOGY OF THE
BRECKENRIDGE MOUNTAIN
QUADRANGLE
CAUFORNIA
BULLETIN 168
1953
DBnonmiuuuimmiiimBmac i
DIVISION OF MINES
FEKHY BUILDING. SAN FRANaSCO
THE LIBRARY
OF
THE UNIVERSITY
OF CALIFORNIA
DAVIS
STATE OF CALIFORNIA
EARL WARREN, Governor
DEPARTMENT OF NATURAL RESOURCES
WARREN T. HANNUM, Director
DIVISION OF MINES
FERRY BUILDING, SAN FRANCISCO 11
OLAF P. JENKINS, Chief
San Francisco
BULLETIN 168
December 1953
GEOLOGY OF THE
BRECKENRIDGE MOUNTAIN
QUADRANGLE
CALIFORNIA
By T. W. DIBBLEE, JR. and CHARLES W. CHESTERMAN
LIBRARY
UNIVERSl 1 Y OF CALIFORNIA
DAVIS
LETTER OF TRANSMITTAL
To His Excellency
The Honorable Earl Warren
Governor of the State of California
Sir : I have the honor to transmit herewith Bulletin 168, Geology of
the Breckenridge Mountain Quadrangle, California, prepared under the
direction of Olaf P. Jenkins, Chief of the Division of Mines, Department
of Natural Resources. The report is accompanied by a detailed colored
geologic map together with cross sections, charts, and photographs of
the area which lies in the. southern Sierra Nevada about twenty miles
east of Bakersfield in Kern County. This map and its report represent
one of the results of the Division's program of basic geologic mapping.
The senior author, T. W. Dibblee, Jr., has mapped not only this Breck-
enridge Mountain quadrangle, but has mapped many other areas in
the state, including western Santa Barbara County and the Saltdale
quadrange, published by the Division as Bulletins 150 and 160 respec-
tively. The junior author, Charles W. Chesterman, a staff member of
the Division, sampled the complex rocks of the area and made a petro-
graphic study of them to supplement the field investigation.
The Breckenridge Mountain quadrangle contains gold mines and also
tungsten deposits north of Walker Basin. In the southwestern part of
the quadrangle, wells were drilled for oil and two of them have produced
small amounts of heavy petroleum. The earthquakes of 1952, which
caused severe damage in the area of Arvin and Tehaehapi, were, caused
by earth movements along the AVhite Wolf fault. This and other major
faults are actually shown on Breckenridge Mountain quadrangle.
Bulletin 168 should provide basic information for mining, for the
development of oil fields, in the study of other natural resources, and
in structural engineering problems.
Respectfully submitted,
Warren T. Hannum, Director
Department of Natural Resources
August 27, 1953
(3)
CONTENTS
Page
ABSTRACT 7
INTRODUCTION 7
PHYSIOGRAPHY 11
STRATIGRAPHY 13
Pre-Cretaeeous rocks 13
Kernville series 13
Pampa schist 18
Intrusive rocks 22
Hornblende-biotite quartz diorite 22
Biotite quartz diorite 24
Gabbro and g:abbro diorite 28
Hornblendite and other basic rocks 31
Pegmatite dikes and quartz veins 32
Tertiary system 33
Walker formation 33
Bealville fanglomerate 36
Ilmon basalt 37
Freeman-Jewett shale 38
Bena gravels 38
Kern River gravel 40
Volcanic breccia 43
Pleistocene sediments 43
Terrace deposits 43
Alluvium 43
STRUCTURE i 43
Structure of the pre-Cretaceous complex 43
Structure of the Tertiary sediments 44
Faults 44
Structural blocks 50
GEOLOGIC HISTORY 51
MINERAL RESOURCES 53
Oil and Gas 53
Tungsten 54
REFERENCES CITED 55
2—79326
CONTENTS— Continued
Illustrations
Plate 1. Geologic map of Breckenridge Mountain quadrangle In pocket
2. Economic map of Breckenridge Mountain quadrangle In pocket
3. Geologic sections through Breckenridge Mountain quadrangle In pocket
Page
Figure 1. Index map of southern California showing georaorphic provinces and
location of the Breckenridge Mountain quadrangle 8
2. Columnar section, Breckenridge Mountain quadrangle 12
3. Geologic map of the southern Sierra Nevada 14
4. Photo of Kernville series toward northeast 15
~). Photo of limestone member of Kernville series 16
6. Photo of garnet and garnetized limestone zones in Kernville series 17
7. Photo of Kernville schist 18
8. Photo of chiastolite schist of Pampa series 19
9. Photo of chiastolite schist of Pampa series 20
10. View northeast toward Breckenridge Mountain 21
11. Photo of quartz diorite with pegmatite dike 23
12. Photo of quartz diorite with dikes and inclusions . 24
13. Photo of inclusions and faulted pegmatites in hornblende quartz diorite 25
14. Photo of inclusions in quartz diorite 26
15. Photo of inclusions in quartz diorite 27
16. Photo of faulted pegmatite dikes in dark gabbro diorite 28
17. View south across mouth of Caliente Canyon 30
18. Photo of Ilmon lava flow 33
19. Photo of Walker beds 34
20. Photo of Bealville fanglomerate___ 36
21. Photo of Ilmon lava flow 37
22. Photo of Walker beds faulted against Bena gravel 39
23. View across Cottonwood Canyon 40
24. Photo of terrace cut in Bena and underlying granitic rocks 41
25. Photo of Breckenridge Mountain and Walker Basin 42
26. Photo of Walker Basin toward the north 44
27. View north down Havilah Canyon 45
28. View east across scarp of Kern River fault 46
29. Photo of cracks along trace of White Wolf fault 47
30. Photo of cracks in earth between Caliente and Tehachapi Creeks 48
31. Photo of crack in earth above Tunnel 4, Southern Pacific Railroad 49
32. Photo of Tungsten Chief mill 54
GEOLOGY OF THE BRECKENRIDGE MOUNTAIN
QUADRANGLE, CALIFORNIAf
By T. W. Dibblee, Jr.,* and Charles W. Chesterman **
ABSTRACT
The fifteen-minute BreckenriflRe Mountain quadrangle, the center of which lies 20
miles east of Bakersfield, takes in a portion of the southern Sierra Nevada and extends
down to the margin of San Joatiuin ^'alley. The northern half of the quadrangle is a
plateau-like area risinj: gradually from the western foothills to the north-trending
ridge of Rreckenridge Mountain. This rising plateau is ai>ruptly terminated on the
east by a steep escarpment facing the 8,r»(K)-f()(it high valley of Walker Basin. The
southern portion of the quadrangle is likewise a westward-sloping plateau-like area
rising gradually from the San Joaquin Valley at 6r)0 feet in the southwest corner of
the quadrangle, eastward to over r),00() feet elevation ; hut this rising ujiland is
breached by deeply incised canyons and tributaries of Walker Basin and Caliente
Creeks flowing westward into San Joaquin Valley.
Metamorphic rocks of the area are assigned to the Kernville series composed of
schists, quartzites, and crystalline limestone's, of sujiposedly Carboniferous age. and
the Pampa schist of Paleozoic or early Mesozoic age. These metasediments occur
as linear inclusions within plutonic rocks which have invaded them in the northeastern,
southeastern and western portions of the quadrangle.
Plutonic rocks ranging from quartz diorite to gabbro crop out over the greater
part of the quadrangle, and belong to the Sierra Nevada ])atholithic invasion of
supposed late Jurassic age. The dominant rock type is hornblende-hiotite quartz diorite
which usually has some i>lanar foliation, and contains many partly digested remnants
of the metasediments. The quartz diorite grades into, or perhaps is intruded by, a
massive biotite quartz diorite. Gabbro, hornblendite and other ultrabasic rocks occur
as small local intrusions or segregates. The plutonic and metamorphic rocks are cut
by numerous pegmatite dikes in certain areas.
In the western foothills in the vicinity of lower Caliente Canyon, the plutonic-
metamorphic complex is unconformably overlain by about 3,000 feet of Tertiary
sediments. These are: (1) Walker formation, 01igocene(?) ; (2) Ilmon basalt, lower
Miocene; (3) Freeman-Jewett shale, lower Miocene ; (4) Bena gravels, Miocene ; (5)
Bealville fanglomerate, (^ligocene-Miocene (facies of Walker and Bena formations) ;
and (6) Kern River gravels. Pliocene. These are all fluviatile formations with the
exception of the marine Freeman-Jewett shale.
The attitude of the Kernville series exposed in the eastern portion of the quadrangle
is generally vertical with a north-south trend. The Pampa schist exjiosed in the
western portion has the same general attitude but with a strong S-shaped flexure.
The attitude of the foliation and inclusions within the quartz diorite is generally
accordant with that of the enclosing metasediments. The overlying Tertiary sediments
of the western foothill area dip about 20° SW. The Breckenridge Mountain plateau
is a structural block tilted gently westward and elevated along the Breckenridge fault
at the eastern base of this steep mountain front. This fault, a part of the Kern Canyon
fault zone, dies out south of Walker Basin. Several minor normal faults trending
roughly eastward are found at the w-estern border of the quadrangle in the foothill
area. The Edison fault, the largest of these, is traceable for about 9 miles from Caliente
westward and dips about 3.")° N., bringing Tertiary sediments on the north in contact
with granitic rocks on the south. Throw amounts to several thousand feet.
Mineral resources consist of small quantities of tungsten ore (scheelite) mined
from garnetized limestones of the Kernville series exposed northeast of Walker Basin.
Some gold has been found, but not in paying quantities.
INTRODUCTION
The topogTaphic map of Breekenridgre Moimtain qnadranple, issued
by the War Department, U.S. Army Corps of Enoineers in 1944, covers
15 minutes of latitude and longitude on a scale of 1 :62500 (1 inch equals
t Manuscript submifted for publication December, 1952.
• Geologist, Richfield Oil Corporation.
•* Associate Mining Geologist, California Division of Mines.
( 7 )
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
Breckenridge Mt. /
T quadrangl6f
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116°
Figure 1. Index map of southern California showing geomorphic provinces and loca-
tion of the Breckenridge ^Mountain quadrangle. Shown cross-hachured are other recently
published geologic quadrangles of the area.
1 iiiile), or about 242 square miles. The center of the quadrangle is 20
miles due east of Bakersfield, California. Breckenridge Mountain quad-
rangle map includes the northeastern quarter of the old Caliente 30-min-
ute map scale 1 :125000 (1 inch equals 2 miles) , issued in 1905 by the U.S.
Geological Survey.
The southern portion of Breckenridge quadrangle is traversed by the
Southern Pacific-Santa Fe Railroad,* and bj^ U.S. Highway 466, passing
through Bakersfield and Tehachapi. State Highway 178 follows Kern
River Canyon between Bakersfield and Kernville ; the area may also be
entered by several county roads. The only settlements within the quad-
rangle are the railroad town of Caliente and railroad camps of Bealville
and Bena. Bakersfield, population 110,000, is 15 miles west of Beiia.
Industry is confined largely to the raising of beef cattle made possible
by excellent pasture. Part of the area southwest of Caliente is farmed,
as is Walker Basin, where barlev and alfalfa are grown. In the hills
nortlieast of "Walker Basin, small amounts of gold and tungsten have
been produced for many years, and a small amount of lieavy oil was
pumped from shallow wells in the extreme southwest corner of the
quadrangle.
1953] INTRODUCTION 9
Climate and Vegetation. In the Breckenridjj^e Mountain area summers
are warm and dry, and winters are cold with occasional rain or snow, but
local climate and precipitation vary with altitude. In the low foothill
area summers are hot, with daytime temperatures exceedin<>' lOU de<>rees,
and winters are mild except for occasional cold valley fog sometimes
lasting- for weeks. In higher altitudes summers are warm to mild, and
winters are cold. Annual precipitation, which falls mostly during the
winter months, varies from less than 10 inches in the foothill area to
several times that amount in the higher mountains, chiefly in the form
of rain below 3,000 feet and as snow above that lev^l. AVinter storms are
generally accompanied by severe gales in passing over the mountains.
Electrical storms occasionally develop over the mountains during the
summer.
Vegetation within the mapped area varies considerably and is divided
roughly into four zones determined by altitude, all of which grade into
one another. Other factors, such as direction and steepness of slope and
character of the underlying rocks, have some local influence, but are
subordinate to altitude. The four zones of vegetation recognized are as
follows : ( 1 ) lower zone, below 2,000 feet, made up of short grasses and
annuals, and scanty low brush, chiefly burrow bush; (2) lower middle
zone, 2,000 feet to 3,500 feet, grasses, annuals, scattered brush, and oak
timber — chiefly post oak ; (3) upper middle zone, 4,000 feet to 6,000 feet,
same as lower middle zone, but with digger pine and considerable ad-
mixture of brush, chiefly scrub oak, buckthorn and mountain mahogany
in dense, impregnable thickets; and, (4) upper zone, over 6,000 feet, tall
timber made up of black oak, western yellow pine, white pine, and white
fir. Streams throughout the area are lined with arrow-weed, willow.
Cottonwood, sycamore, and live oak.
Junipers and piiions are confined to the mountains east of Walker
Basin and Havilah Canyon.
Rock formations are moderately well exposed over most of the quad-
rangle. Granitic and metamorphic rocks form prominent outcrops in
steep, narrow canyons and generally on south-facing slopes. Summits
and north-facing slopes are generally covered with a thick mantle of
residual soil so that rock outcrops are less prominent.
Procedure. Field mapping was done directly on the Breckenridge
quadrangle base, except in the southwestern portion ; there it was done on
aerial photographs, scale 1 inch equals 1,666 feet (approx. ), and the
geology later transferred to the quadrangle. Field work was carried
on at various times since 1945, by the writer, assisted in the southwest
portion by A. H. Warne. The major part of the field work was done
during May-June 1950. Field work was completed in 33 days.
Achnoivledgments. The writer is indebted to Richfield Oil Corpora-
tion for the use of aerial photographs used in mapping the geology of
the southwestern portion of the quadrangle, and for the permission to
publish the geology of this portion. Acknowledgment is also due A. H.
Warne, who assisted in mapping the southwest portion.
Previous Geologic Work. Little has been published on the geology of
the area covered by Breckenridge Mountain quadrangle, although se-^eral
papers have appeared dealing with the geology of adjoining areas and
10 BRECKENRIDGE MOUNTAIN QUADRANGLE [Bull. 168
with broad physiographic and structural features of the southern Sierra
Nevada.
A study of the geomorphic features of the Kern River Canyon by
Lawson (1904), who first recognized the Kern Canyon fault, was pub-
lished in 1904, and in a later paper (Lawson 1906), he described the
geomorphic features of the Tehachapi area.
Broad structural features of the southern Sierra Nevada were dis-
cussed bv Buwalda (1915, 1920, 1934) ; by Hake (1928) ; and by Locke,
etal. (1940).
The first paper describing various rock units in part of the Kernville
quadrangle was one by Miller (1931). In a later paper Miller and Webb
(1940) mapped the areal geology of this entire quadrangle. Several
papers dealing with the geology of the Isabella dam site have been pub-
lished, including those by Louderback (1916), and Forbes (1931). In
connection with this project, the geology of the Isabella quadrangle has
recently been mapped by Treasher (1949, abst.).
Little has been published on the geologj^ of the western foothill area of
the southern Sierra Nevada, except for the geology of the Tejon Hills
at the extreme southern end (Hoots 1930).
Many papers on the subsurface geology and stratigraphy of the nearby
eastside oil fields of San Joaquin Valley have been published. Godde
(1928) described the general stratigraphy of the area. The geology of
the Mount Poso oil field is described by Wilhelm and Saunders (1927),
of the Round Mountain oil field by Rogers (1943) , of the Edison oil field
by Edwards (1943), Beach (1948), and Hewitt and May (1948).
Geologic Setting. The area covered by'Breckenridge Mountain quad-
rangle lies in the extreme southern portion of the Sierra Nevada and is
made up of a pre-Cretaceous granitic-metamorphic complex typical of
the region.
The plateau-like highland of Breckenridge Mountain is topograph-
ically the extension southward of the Greenhorn IMountains, a north-
trending range which forms the "Western Divide" of the southern
Sierra Nevada. The Greenhorn and Breckenridge Mountains constitute
a fault block tilted gently westward toward San Joaquin Valley which
is roughly bounded on the east by the Kern Canyon fault zone, along
M'hich the Breckenridge Mountain portion has been elevated. The Kern
Canyon fault is traceable for some 50 miles through the southward-
trending portion of Kern Canyon and along the eastern base of Brecken-
ridge Mountain ; it then disappears south of Walker Basin into an area
of low, even-crested mountains.
The mountains of the southern Sierra Nevada, made up of a basement
complex of granitic and metamorphic rocks, slope gently westward to
the San Joaquin Valley foothills, where the basement complex is covered
by Tertiary sedimentary rocks. The surface of the basement and the over-
lying sediments exposed along the foothills slope westward under the
San Joaquin Valley at a more or less uniform angle of 6°. The foothills
are broken by many small normal and vertical faults trending from north
to west. The exposures of Tertiary sediments, continuous for some 25
miles along the foothills, are abruptly terminated on the south by the
Edison fault which brings up the basement complex south of lower
Caliente Canyon.
A short distance southeast of lower Caliente Canyon, just south of
the quadrangle mapped, the San Joaquin Valley foothills abut against a
1953] PHYSIOGRAPHY 11
steep, northwest-slopinf; front that rises abruptly to a mountain plateau.
The plateau reaches a high point of nearly 7,000 feet at Bear Mountain,
and owes its existence to elevation alonp: the White Wolf fault bounding
its straight northwestern base. About 20 miles farther southeast, this
fault is paralleled by the northeast-trending Garlock fault, an active
vertical master fault of left-lateral movement.
PHYSIOGRAPHY
Most of the area in Breckenridge Mountain quadrangle is plateau-like ;
the hills and mountains rise gradually northeastward, with relief ranging
from 650 feet elevation in the extreme southwest corner to 7,544 feet
at Breckenridge Mountain, the highest point. From San Joaquin Valley
the terrain rises gradually north of east, through low foothills at the
western border of the quadrangle, to high, plateau-topped mountains in
the eastern portion, except for local irregularities due to faulting. All
major streams are consequent to this general slope and flow south of
west. The mountains throughout the quadrangle are characterized by
subdued summits and gently sloping flanks. However, the major streams
and their main tributaries are deeplv incised in narrow V-shaped can-
yons. Those such as Kern River, Walker Basin Creek, and Caliente
Creek have deepened their channels about 1,500 or 2,000 feet below the
gently rolling upland surface. Of these, Caliente Creek has developed
a small flood plain where it emerges through the low foothills.
The flat mountain summits and the foothills to which they taper, are
remnants of an earlier erosion surface which had reached the late ma-
turity stage of the first cycle of erosion. Subsequent elevation by west-
ward tilt has caused dissection of this old surface and rejuvenation of
the canyons so that the area is now in the late youth or early maturity
stage of the second cycle of erosion.
Drainage. Kern River flows south westward through a deep, youthful
gorge across the northwest corner of the quadrangle. Cottonwood Creek
drains the southwestern slope of Breckenridge Mountain and flows south-
west through a deep canyon in the lower reaches. Walker Basin Creek
drains the valley of that name and flows southwest through a narrow
gorge into Caliente Creek at Bena. Caliente Creek flows westward through
a narrow canyon, is joined at Caliente by Tehachapi Creek flowing north-
west, and finally opens out through a flood plai^ at Bena into San Joaquin
Valley.
Physiographic Features. Breckenridge Mountain, which covers the
north-central portion of the mapped quadrangle, is roughly a dome-
shaped mountain that has a steep, abrupt eastern slope facing Walker
Basin. The imposing straight eastern front of this mountain is a fault
escarpment ; it rises from an elevation of 3,500 feet at the eastern base
to a high point of 7,544 feet at Breckenridge Mountain within a distance
of about 2 miles. The top of the mountain mass is a gently rolling plateau
averaging 6,500 feet elevation, which slopes southwestward to a much
lower area of mountains at elevations of 3,000 feet to 4,500 feet. The lower
plateau slopes very gradually over a distance of about 6 miles down to
about 2,500 feet at its southwestern margin, beyond which are low foot-
hills made up of easily eroded sediments.
12
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
<
LiJ
LITHOLOGY
DESCRIPTION
O
O
N
O
z
UJ
o
o
o
o
N
O
UJ
_l
Gravel, sand and silt
°V. S-.rea
:-lai3 eravels Ic sands
UNCONFORMITY
BIOTITE
QUARTZ
DIORITE
O
o
(O
M
U)
o
<
en
q:
UJ
3
?
-3
HORNBLENDE
BIOTITE
QUARTZ
DIORITE
GABBRO-
DIORITE
HORNBLENDITE
a
GABBRO
PAMPA
SCHIST
KERNVILLE
SERIES
100* Coarse cobble gravel
600'' Gray sand, silt and
pebble gravel,
500* Coarse pray cobble gravel
1 SCO N FOR MIT Y
Light gray to buff, medium
to coarse, pebbly granitic
sands and gravels with well-
rounded cobbles.
Jqdh
UJ
>
CO
Jgd
Jh
Pp
8000 +
Pk
9000'+
Light brown thin-bedded
sixty to sandy clay shale
1^ — ^
gasi
Walker :
200-2200 'light gray
granitic sandstone &
conglomerate: minor
tuff fragments
Bealville:
.ight gray
'unsorted
boiilder
'angloraerate
of granitic
0-100 Tuff -breccia /debris
650'* Granitic / Upper 200
sandstone, clay, / made up of
conglomerate / diorite debris
■ UNCONFORMITY-
Biotite-quartz diorite:
gray-white, equigranular
medium grained, massive;
biotite in euhedral
crystals.
Biotite hornblende quartz-
diorite: gray, equigranular,
medium grained, foliated;
contains scattered to numerous
dark gray fine grained inclusions.
Gabbro and gabbro-diorite:
dark gray, equigranular, medium
grained, massive.
Hornbiendite, hornblende-gafabro
and other ultra-basic rocks:
black to gray, medium to coarse
grained .
Dark gray mica-schists;
chiastolite mica-schists; chlorite
greenstone schist.
Dark gray mica-schists; minor
gray quartz Ites: fine to coarse
crystalline gray to white lime-
stones .
Figure 2. Columnar section, Breckenridge Mountain quadrangle.
1953] STRATIGRAPHY 13
The area east of the Breckenridge Mountain plateau is part of the block
depressed along the Kern Canyon fault zone. Red Mountain is the west-
ernmost spur of Piute Mountain, a northwest-trending mountain range
about 8,000 feet high lying east of the mapped quadrangle. Red ^lountain
is separated from Breckenridge Mountain by 4,300-foot higli Ilavilah
Pass. South of this pass lies Walker Basin, a triangular alluviated valley
about 3,500 feet in elevation. This valley is the lower portion of a major
canyon draining westward from Piute Mountain, and has become
dammed by uplift of the Breckenridge Mountain block on the west
causing the canyon to become filled with alluvium to form a valley. This
valley drains southwestward through Walker Basin Creek, an antecedent
stream which has eroded deeply into the mountain block during its ele-
vation. The mountains of the southeastern portion of the quadrangle
mapped are an extension of the Breckenridge Mountain plateau ; they
continue eastward south of Walker Basin. This mountainous area is
divided into two main east-west trending ridges by Caliente Canyon ;
the ridges are characterized by subdued, even-crested summits tapering
from 5,000 feet elevation westward to about 2,500 feet, and dropping off
somewhat abruptly to the low foothills west of Caliente.
The low, subdued topography of the foothills of the soutliwestern por-
tion of the quadrangle is due largely to the underlying soft sedimentary
formations which are more easily eroded than the granitic and meta-
morphic rocks of the mountain areas. Nearly all streams draining through
these foothills have developed flood plains. The foothills slope gently
into San Joaquin Valley.
STRATIGRAPHY
Pre-Cretaceous Rocks
Kernville Series
Definition. The name Kernville was proposed by ^Miller (19."U. p.
335), for the metasedimentary series cropping out in the vicinity of
Kernville. This series exposed in Kernville quadrangle Avas mapped as
the Kernville series by Miller and Webb (1940, map). In eastern Breck-
enridge ]\Iountain quadrangle, metasediments identical to the Kernville
series are exposed and are mapped as such.
Distrih}(tion and Thickness. In Breckenridge Mountain quadrangle
the metasediments recognized as the Kernville series crop out near the
eastern border as a continuous band about a mile wide within granitic
rocks on the west slope of Red IMountain. The band passes out of the
quadrangle east of Walker Basin, but swings back in soutli of Caliente
Creek and extends up Devil Canyon where it fingers southward into
many linear inclusions within the invading granitic rocks. The metasedi-
ments in this band are more or less vertical and a total apparent thick-
ness of about 6,000 feet is exposed — if not isoclinally folded.
Lithologic Character. The Kernville series exposed in Breckenridge
Mountain quadrangle is made up largely of mica schist, some interbedded
cuartzite, and lenses of crystalline limestone. The mica scliist is dark
gray, weathers brown-gray, laminated, fine-grained, and has prominent
cleavage. It becomes medium- to coarse-grained adjacent to granitic in-
trusions. Tlie schist is made up largely of biotite, but has some muscovite,
feldspar, and quartz. Microscopically, the schist of the Kernville series
3 — 79326
14
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
Figure 3. Geologic map of the southern Sierra Nevada showing- location of Brecken-
ridge quadrangle.
1953]
STRATIGRAPHY
15
has a crystalloblastic fabric developed through recrystallization of a
pelitie sediment under processes of regional metamorphisni. It is quite
uniform in composition and texture, and consists essentially of quartz,
biotite, muscovite, albite, and garnet. Quartz is one of the most abundant
minerals and occurs in aggreg^ites of equidimensional and elongate grains
that include needle-like crystals and plates of muscovite. Dark brown,
strongly pleochroic biotite in well-oriented plates is also an important
constituent of the schist. Inclusions of zircon with dark pleochroic halos
are common in the biotite. Muscovite occurs in two distinct sizes: (1) as
fairly large porphyroblasts up to 7 millimeters in width and (2) as
small wisp-like plates and flakes less than one millimeter in diameter.
Calcic albite (An4.to Ans) is well developed in multiple-twinned equidi-
mensional grains. Garnet occurs in rounded colorless crystals scattered at
random throughout the sections, but is not an important mineral in
the schist. Quartzite beds are light-gray to bluish-gray, fine-grained,
and occur as interbeds as much as a foot thick.
Figure 4. KernviUe series toward northeast. About a mile and a half northeast of
Tungsten Chief mill. Quartz diorite (?) in background.
Quartzite interbeds are subordinate to the schists, but in some layer*"
they form prominent, though much broken, outcrops. In thin section tLe
quartzite was fount! to be made up of a granoblastic aggregate of quartz,
albite, zoisite, hornblende, muscovite, scheelite, and graphite. Quartz,
the most abundant constituent, forms rounded and elongated grains
whose boundaries are both curved and sutured. Strain shadows are well
developed and serve as an aid in distinguishing quartz from albite, most
of which is untwinned. Hornblende is pale green in color and forms
16
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
•^
Figure 5.
Limestone member of Kernville series. About a mile northeast of Tungsten
Chief mill.
needle-like crystals scattered throughout the sections. Small, angular
grains of colorless zoisite occupy interstices. Feathery crystals and
wisps of muscovite are wrapped around quartz and albite. The albite is
in equidimensional grains. Scheelite, in brown idioblastic crystals, shows
well-developed crystallographic outline. Scattered throughout the sec-
tions are numerous small dustlike particles of graphite.
Limestone, which crops out prominently, occurs as lenses up to 100
feet thick, some of which are traceable for about a mile. The limestone
is light-gray, fine-grained, bedded, but may be white coarsely crystalline
marble, depending on the degree of metamorphism. North of Walker
Basin contact metamorphic action between granitic dikes and impure
limestone of the Kernville series has resulted in the formation of lime-
silicate rocks composed of coarsely crystalline calcite, light-reddish and
brown garnet, quartz, clinozoisite, and minor amounts of scheelite.
Thin sections prepared from hand specimens taken from several zones
of lime-silicate rocks indicate an assemblage of minerals which includes
diopside, clinozoisite, garnet, oligoclase, hornblende, sphene, calcite,
scheelite, and quartz. Clinozoisite, diopside, sphene and garnet are by
far the most abundant minerals present, whereas scheelite, hornblende,
and oligoclase are only locally developed. Calcite and quartz are very
sporadic in their distribution and appear to have developed somewhat
later than the other constituents excepting the scheelite which was one
of the last minerals to form. Garnet is colorless and occurs both as
idioblastic crystals and as irregular grains in granoblastic aggregates.
Clinozoisite in irregular grains exhibits strong anomalous interference
1953]
STRATIGRAPHY
17
colors in shades of brown and bine. Diopside occnrs in ronnded colorless
grains. Calcic oliyoclase, also in rounded grains, shows several types of
twinning-. Sphene is rather abundant as irregular crystals. Scheelite is
pale brown in color and forms idioblastic crystals and rounded grains.
Figure 6. Garnet and garnetized limestone zones in Kernville series.
About a mile northeast of Tungsten Chief mill.
Small isolated inclusions of coarse quartz-mica schist approaching
the texture of gneiss occur throughout the granitic rocks in much of the
quadrangle, especially in the southeastern portion, where they have a
prevailing north strike parallel to the Kernville exposures at the eastern
border. They are undoubtedly incompletely digested remnants of the
Kernville series as shown bj^ a limestone inclusion about a mile long
southwest of Montgomery Canyon. These widespread inclusions of uni-
form attitude suggest that prior to the granitic invasion the Kernville
series within the quadrangle was of tremendous thickness — if not
isoclinally folded.
Age and Correlation. Very little is known concerning the age of the
Kernville series as it has yielded no fossils. Miller and Webb (1940, p.
352), are of the opinion the Kernville series correlates with the Calaveras
18
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
iK^Sc^Hb^BBPr'* *
i*'*^^*^ *
^t^V-v;.' /fill ?^:';
Figure 7. Kernville schist. One mile northeast of Tungsten Chief mill.
of Carboniferous age on the basis of lithologic similarity; and for this
reason the series is tentatively assigned to the Carboniferous.
Pampa Schist
Definition. In the western part of Breekenridge Mountain quadrangle
several isolated pendants of dark mica schist are prominently exposed
in the Cottonwood Canyon drainage area west of Pampa Peak, for which
the schist is named. The formation is possibly a phase of the Kernville
series, but as it is of somewhat different lithology and as its relationship
to the Kernville is obscured by granitic invasions, the Pampa is desig-
nated by a local name.
Distribution and Thickness. The Pampa schist crops out within gra-
nitic rocks as linear inclusions with vertical or near-vertical attitudes.
One of these inclusions, prominently exposed west of Pampa Peak is
about a half mile wide and trends northeast for about 2 miles. To the
north in Cottonwood Canyon, there is a large S-shaped inclusion, half a
mile to a mile wide, that is traceable for five miles. To the northeast in
upper Cottonwood Canyon a linear band as much as 2 miles wide trends
northwestward for about 4 miles. In addition to these three large inclu-
sions there are many small lenticular outcrops.
All inclusions of the Pampa schist are more or less parallel with a
regional northwestward trend except for the S-shaped flexure in Cotton-
wood Canyon. Attitudes are vertical or nearly so. The Pampa schist
appears to be remnants of a once very thick, upturned section invaded
1953]
STRATIGRAPHY
19
-: -^^f^
"^1^'
Figure 8. Chiastolite schist of Pampa series, two miles west of Pampa Peak.
by plutonic rocks. It is not known which side is top or bottom, but in the
flexured inclusion the schist gfenerally dips steeply toward the south and
southwest, suggesting the oldest beds are to the northeast in upper Cotton-
wood Canyon and the youngest may be those west of Pampa Peak. If
these inclusions are parts of a once continuous section not repeated by
isoclinal folding, the total thickness represented must have been in the
neighborhood of 20,000 feet.
Lithologic Character. The Pampa schist is generally similar to the
Kernville schist in the eastern portion of the quadrangle. The Pampa
schist is generally laminated and highly cleavable with platy fracture.
The schist forms dark, jagged outcrops, and commonly shows minute
contortions near granitic intrusions: It is made up largely of muscovite
but contains some biotite, feldspar, and quartz. It is probably of sedi-
mentary origin as suggested by its foliation, which is parallel to the
original bedding. In contrast to the Kernville series, the Pampa schist
contains no limestone, and quartzite is rare.
The most westerly portion of the Pampa schist exposure west of Pampa
Peak is made up of chiastolite or andalusite schist, which forms a member
of about 2,000 feet exposed thickness that is traceable for three-quarters
of a mile. The member again appears about 2 miles northwest in Cotton-
wood Creek. The andalusite schist is the same as the usual Pampa mica
schist, but contains numerous crystals of andalusite (chiastolite) from
an eighth to a quarter of an inch thick and up to several inches long.
20
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
.•«^^ l7lk-i^>
^^:. V ring-
's. -^^\
Figure 9. Chiastolite schist of Pampa series, two miles west of Pampa Peatc.
They are oriented parallel to the cleavage, and have apparently resulted
from an excess of alumina in this member.
In the field and in samples under the microscope one can easily dis-
tinguish the three Pampa schist units: (1) quartz-biotite schist, (2)
quartz-biotite-andalusite schist, and (3) chlorite schist. The first two
rocks are products of regional metamorphism of pelitic sediments in the
biotite zone, and the chlorite schist might very well have been formed
from either a basic tuff or lava flow. Plutonic invasions have further
metamorphosed these rocks, but the action merely resulted in coarsening
of the grains, especially near contacts, rather than mineralogical recon-
stitution.
Under the microscope the quartz-biotite schist shows a well-developed
foliated fabric. Quartz is rather abundant and occurs in rounded equi-
dimensional grains showing wavy extinction. Biotite that is dark brown
in color, strongly pleochroic in shades of dark and light brown, occurs in
single plates evenly distributed and as clusters of smaller crystals. En-
closed in the biotite are small crystals of zircon with dark pleochroic
halos. Calcic oligoelase occurs in equidimensional grains with irregular
boundaries. It is found locally only and is not an important constituent.
Muscovite is unevenly distributed throughout the sections as large
porphyroblastic plates that exhibit no particular orientation and as
aggregates of small shredlike plates and wisps that form swirls around
the quartz grains.
Under the microscope the quartz-biotite-andalusite'-museovite schist,
too, shows a well-developed foliated fabric with large porphyroblasts of
1953] STRATIGRAPHY 21
-*>--. >i. V
'y^.
Figure 10. View northeast toward Breckenridge Mountain. Kern River beds exposed
in hills to left ; Pampa schist and quartz diorite in dark rugged hills to right. Pampa
Peak near extreme right.
andalusite (chiastolite) set in foliated matrix or quartz, garnet, plagio-
clase, and mica. Quartz is very abundant, forming rounded equidimen-
sional grains scattered throughout the sections and granoblastic aggre-
gates of coarse grains lying between the broken ends of large andalusite
crystals. Biotite also is abundant, occurring in dark greenish-brown
idioblastic plates that exhibit strong pleochroism in shades of dark and
light brown. Inclusions of zircon are common, many of them are sur-
rounded by dark pleochroic halos. Andalusite, called chiastolite because
of its symmetrically arranged carbonaceous inclusions, is colorless ; it
occurs in porphyroblasts as much as 2 inches in length, and as irregular
or skeletal crystals having a motheaten appearance. In places the andalu-
site has the appearance of having been replaced in part by quartz, and
it is not uncommon to find plates of muscovite forming incomplete rims
around the andalusite crystals. Muscovite is quite common and forms
colorless plates scattered throughout the sections and also somewhat
coarser plates associated with the coarse-grained quartz between the
broken ends of the andalusite crystals. Both garnet and calcic oligoclase
are present as angular and rounded grains.
The northeastern exposure of the Pampa schist contains a massive
chlorite schist a member about 2,000 feet thick that is exposed between
Rattlesnake and South Fork Cottonwood Creeks. The member is made
up of fine grained, massive, greenish-brown rock with irregular fracture
rarely showing cleavage. It is essentially a "greenstone", but appears to
be made up of finely divided chlorite. Locally it contains veinlets of
22 BRECKENRIDGE MOUNTAIN QUADRANGLE [Bull. 168
calcite and quartz. The member is apparently of volcanic origin, probably
a basalt, but is highly altered.
Age and Correlation. As the Pampa schist has yielded no fossils, its
age is unknown. Its relationship to the Kernville is unknown. All that
can be said is that it is Jurassic or older.
Intrusive Rocks
Plutonic intrusive rocks characteristic of the Sierra Nevada batholith
underlie the greater portion of Breckenridge Mountain quadrangle in
which the major rock type is quartz diorite. The following types of in-
trusive rocks were recognized and mapped : quartz diorite, divided into
two distinct facies — (a) foliated hornblende-biotite quartz diorite; and
(b) massive biotite quartz diorite; gabbro and gabbro-diorite ; horn-
blendite, hornblende diorite and other basic rocks, including small bodies
of gabbro-norite that were examined both in the field and in the labora-
tory.
The quartz diorite forms the major portion of the Sierra Nevada gra-
nitic batholith within the quadrangle ; the basic rock types form local
intrusions or segregates only. All of these intrusives are intimately asso-
ciated and part of the Sierra Nevada batholith invasion is believed to have
occurred in very late Jurassic time.
Hornblende-Biotite Quartz Diorite
Hornblende-biotite quartz diorite, more or less foliated, is the most
widespread facies of the quartz diorite in Breckenridge Mountain quad-
rangle. The rock is widespread throughout the northern portion of the
quadrangle, and extends into the southeastern portion of the quadrangle.
LitJiologic Character. The foliated hornblende-biotite quartz diorite
is an equigranular, light- to medium-gray rock, depending on the amount
of hornblende. It is made up largely of white feldspar and quartz in the
average ratio of about 3 :1. Biotite and hornblende are always present,
but in varying amounts. The dark minerals range from less than 5 per-
cent to about 30 percent of the total mineral content of the rock. The
biotite occurs as small scattered flakes, and the hornblende as elongated
crystals somewhat larger than the other minerals of the rock.
Throughout the entire quadrangle where this rock is well exposed it
exhibits remarkably uniform texture and mineralogical composition,
excepting locally where small inclusions of a finer-grained texture and
an increase in the mafic constituents have developed.
In thin section the hornblende-biotite quartz diorite has a hypidio-
morphic granular texture. Both the biotite and hornblende show several
crystal faces, but the feldspar and quartz are usually anhedral. The
plagioclase is sodic to intermediate andesine (An^s to An43) and makes
up from 45 to 50 percent of the rock by volume. It shows well-developed
complex twinning and in some places a light zoning with only a minor
difference in composition between the zones. Alteration is not marked,
usually to sericite and rarely to kaolin. Quartz is common and averages
between 15 and 20 percent of the rock by volume ; it exhibits strong wavy
extinction. Hornblende makes up about 20 percent of the rock by volume,
but locally it is either in smaller or greater amounts. It is dark brownish-
green to green in color and moderately pleochroic in shades of green,
greenish-brown, and bluish-green. Twinning on the (100) is rare.
1953]
STRATIGRAPHY
23
Figure 11. Quartz diorite with pegmatite dike. Caliente Canyon at intersection of
Walker Basin road.
Biotite usually in dark brown pleoehroic plates makes up to 10 percent
of the rock by volume. Inclusions of magnetite and zircon are common
in the biotite, more so than in the hornblende. Locally a small amount
of colorless diopside occurs, especially as cores surounded by light green
fibrous amphibole. Minor accessory minerals are zircon ■\\tith dark
pleoehroic halos in biotite, sphene, allanite, apatite, and magnetite.
Calcite, kaolin, sericite, and chlorite are the secondary minerals.
The hornblende-biotite quartz diorite is characterized by primary
foliation almost throughout which is most prominent in the darker
phases rich in biotite and hornblende, and poorest or almost absent in
the lighter phases. In some areas it is so prominent as to give the rock
the appearance of gneiss, but the rock is of more or less homogeneous
granular texture rather than being composed of alternating layers of
varying mineralogical content such as characterize true gneiss. The
foliation is generally developed by sub-parallel orientation of mineral
grains in a homogeneous mass. The rock weathers by mechanical disin-
tegration and by exfoliation, and has a tendency to joint or cleave
parallel to the foliation.
The hornblende-biotite quartz diorite commonly contains inclusions
or xenoliths of dark fine-textured dioritic rock in amounts varying from
almost none to 20 percent of the enclosing rock. They occur as lenses of
all sizes, but average about 8 inches across and about 2 inches thick.
They are invariably oriented parallel to the foliation of the host rock.
These inclusions are probably partially digested remnants of the original
metasediments intruded by the hornblende-biotite quartz diorite.
24
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
Figure 12. Quartz diorite with dikes and inclusions. Up Oiler Canyon a mile from
Caliente Canyon.
Biotite Quartz Diorite
The massive biotite quartz diorite almost devoid of hornblende com-
prises the lighter-colored phase of the quartz diorite and forms several
bodies within the mapped quadrangle. The largest mass occurs in the
central portion in the vicinty of lower Walker Basin Canyon. Masses
also occur north of Mount Adelaide, at Red Mountain in the extreme
northeastern portion of the quadrangle, in the Piute Mountain range
to the east, and in the extreme southwestern portion of the quadrangle.
To the north, in Kernville quadrangle, the rock was mapped as the
Isabella granodiorite by Miller and Webb (1940, p. 357), although in a
footnote they state it to be quartz raonzonite on the basis of petrographic
determinations.
Lithologic Character. The biotite quartz diorite is gray-white, me-
dium- to coarse-textured and equigranular. It is massive and rarely
shows foliation. The rock is made up of white feldspar (mainly plagio-
clase) and translucent quartz in the average ratio of about 2:1. Dark
minerals which make up less than 25 percent of the total rock mass
consist of biotite in euhedral hexagonal crystals ranging from an eighth
to nearly half an inch across. Hornblende and other dark minerals are
either absent or occur in very small amounts.
Microscopically the biotite quartz diorite has a hypidiomorphic gran-
ular texture. The plagioclase is sodic andesine (An32 to Auae) which
makes up to 46 percent by volume of the rock. The mineral is complexly
twinned and some grains show poorly defined zonal structure with only a
1953]
STRATIGRAPHY
25
slight difference in composition between the successive zones. Locally the
andesine is altered to sericite, more so at the center of each crystal than
at the margin or outer zone. Minor amounts of microcline are present,
especially in those specimens collected from the quartz diorite exposed
in the northeastern part of the quadrangle. Quartz is usually in rounded
grains in amounts up to 25 percent. Biotite is the commonest mafic
mineral present, although hornblende is locally present and in a few
isolated occurrences it exceeds the biotite in amount. The biotite is in
dark brown to olive-green plates that show strong pleochroism in shades
of brownish-green. In a few sections it is altered to pale green chlorite.
Hornblende, when present, is in bluish-green stumpy prismatic crystals.
Minor accessory minerals include brown tourmaline, sphene, apatite,
magnetite, and zircon with dark pleochroic halos. Chlorite, sericite, and
calcite are secondary minerals.
In Kernville quadrangle, according to Miller and Webb (1940, p.
357), the "Isabella grandiorite" averages the following percentage
composition: quartz, 30; orthoclase or microcline, 30; plagioclase (oligo-
clase-andesine An3o-An4o), 30 ; accessory minerals, 10. The authors (foot-
note, p. 357), state this quartz monzonite to be the most common facies.
However, in samples taken in Breckenridge Mountain quadrangle from
similar-appearing rock, there is less than 5 percent total potash feldspar,
well above 45 percent plagioclase and as much as 25 percent quartz, a com-
position characteristic of quartz diorite. Although the massive biotite
quartz diorite is probably a facies of the foliated hornblende quartz
Figure 13. Inclusions and faulted pegmatites in hornblende quartz diorite. Up Oiler
Canyon four miles north of Caliente Canyon.
26
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
Figure 14.
Inclusions In quartz diorite in Kern River Canyon about a mile down-
stream from moutli of Cow Flat Creek.
diorite and is about the same mineralogical composition except for the
near absence of hornblende, it is fairly distinct and can be mapped as a
unit. Contacts between the two faeies are sharp in some areas ; in others
they are imperceptibly gradational. The two faeies are distinguished
from each other by the massive character of the biotite quartz diorite
faeies, also by its lighter color, scarcity of hornblende, euhedral char-
acter of the biotite, and absence of inclusions and of foliation.
Jointing in the massive quartz diorite is widely and more or less evenly
spaced. South of Pampa Peak two major sets are developed, one trending
N. 50° "VV. and dipping steeplj^ NE, and another at right angles to this
set and generally vertical. The rock weathers readily by mechanical
separation of grains in softer portions and by exfoliation of harder
portions into round outcrops and boulders.
Mode of Intrusion. The foliated hornblende-biotite quartz diorite
and massive biotite quartz diorite are believed to represent two waves
of the Sierran batholithic invasion in this local area, as indicated by
the difference of the two faeies and by the occurrence of many pegmatite
dikes bordering the central mass of massive biotite quartz diorite which
appear to have originated from it. The foliated hornblende-biotite quartz
diorite is the older of the two faeies and appears to have invaded the
metasediments by gradual emplacement lit par lit. The massive biotite
quartz diorite is younger, representing the later and final stage of the
Sierran invasion by massive intrusion of liquid magma.
1953]
STRATIGRAPHY
27
V^ ip i
"i'
Figure 15.
Inclusions in quartz diorite in Kern River Can>on about a mile down-
stream from mouth of Cow Flat Creek.
The manner in which the foliated hornblende-biotite quartz diorite
invaded the metasediments is well shown in all exposures where they
occur as tabular remnarl^ts fingering out into the intrusive rock. This
condition clearly indicates that the magma invaded the metasediments
accordantly along bedding planes, metamorphosing and digesting them
bed by bed. Many inclusions of these metasediments remained in place
as incompletely digested remnants within the quartz diorite. The planar
foliation of the quartz diorite, which is consistently accordant to the
attitude of the unassimilated remnants of the metasediments, is probably
flow-structure, developed by flowage of the magma as it worked up along
bedding planes of the metasediments and assimilated those rocks bed
by bed. The foliation of the plutonic rock is thus of primary origin and
its attitude is relict to that of the original metasediments it invaded;
it indicates that the rock may have been emplaced as a series of sill-like
intrusions by slow, gradual assimilation of the metasediments bed by bed.
The local gradation of the foliated quartz diorite into the massive
quartz diorite indicates that the two magmas in part were intruded simul-
taneously while the occurrence of the massive quartz diorite as irregular
bodies within the foliated quartz diorite indicates the massive quartz dio-
rite to be later, in part. The massive biotite quartz diorite intruded the
pre-existing rocks as a large mass of fluid magma cutting through both
the metasediments and the earlier, perhaps incompletely solidified, foli-
ated quartz diorite, and completely digested the rocks it intruded. The
28
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
manner in which the massive quartz diorite has intruded the metasedi-
ments is superbly shown by field relationships at Red Mountain, and also
west of Pampa Peak. In these areas the quartz diorite was intruded as a
series of dikes fingering into the bedding of the metasediments generally
accordant to the bedding but with some dikes slightly discordant to it.
Some dikes can be seen to intersect or merge with each other.
Gabbro and Gabbro-Diorite
Two exposures of dark-colored gabbro and gabbro-diorite occur within
quartz diorite in the northwestern portion of Breckenridge Mountain
quadrangle. One of these occurs as an irregular body in Kern Canyon
near the extreme northwest corner of the map. The other occurs as a
linear body near Pampa Peak and extends northeastward for some 4
miles.
The gabbro is a massive dark-colored, medium-grained equigranular
rock. It is gray-black on a fresh surface but weathers gray and does not
disintegrate mechanically but tends to exfoliate into round boulders. The
rock is made up of about 50 percent dark to medium-gray plagioclase
feldspar, the remainder being composed of hornblende, pyroxene, and
biotite. The rock varies from gabbro to gabbro-diorite depending on the
percentage of calcic and sodic plagioclases.
Under the microscope the hornblende gabbro-diorite is a medium- to
coarse-grained rock with a hypautomorphic granular texture. Individual
crystals are usually less than 5 millimeters in diameter, although locally
the rock is coarser grained. The feldspar, sodic labradorite (An4s to
•j^*^-
^^
0^-
f'i^/r
^A
/■ r
Figure 16. Faulted pegmatite dikes in dark gabbro-diorite near Richbar, Kern River
Canyon.
1953 J STRATIGRAPHY 29
Anse), constitutes at least 40 to 50 percent of the rock by volume and oc-
curs in subhedral crystals showing complex twinning and poorly defined
zoning. Seeondarj^ alteration of the feldspar is not common, but when
present it is to a cloudy zone of serieite flakes usually at the central part
of the crystal. Augite is present in pale greenish subhedral crystals that
show weak pleochroism. Twinning is common and so is alteration to a pale
greenish amphibole. Augite, although somewhat sporadic in its distribu-
tion, constitutes at least 20 percent of the rock by volume. Hornblende
is strongly pleochroic from pale yellowish to brownish-green, and forms
irregularly shaped prisms, commonl.v twinned. It appears to be in part an
alteration product of the augite and makes up about 25 percent of the
rock by volume. Locally small amounts of dark brown biotite and rounded
quartz are present. Magnetite and zircon are generally inclusions in the
hornblende. Apatite and sphene occur as well shaped crystals with ran-
dom orientation.
In thin sections the gabbro is seen to be a coarse grained rock with an
average grain size of about 5 millimeters. The rock is composed of labra-
dorite (50 percent), hornblende (30 percent), hypersthene (15 percent),
biotite (5 percent), and minor amounts of quartz. The feldspar, sodic
labradorite (An-,2 to An,-,G), forms well twinned crystals showing mul-
tiple twins according to the albite, pericline, and carlsbad laws. The twin-
ning lamellae in a few of the labradorite crystals are bent sufficiently
to suggest minor post-feldspar deformation. Zoning is present but not
distinctly enough to determine ditt'erences in zone composition. The horn-
blende is pleochroic in shades of light green and pale brown and forms
fairly large irregular prisms measuring as much as 10 millimeters in
length. Hypersthene is present in rounded crystals, generally as cores
surrounded by pale green to colorless amphibole. The hypersthene is
slightly pleochroic from pale pink to pale green and contains schiller in-
clusions. Biotite forms dark golden brown subhedral crystals, and quartz,
although generally present in small amounts, forms rounded grains. Zir-
con, magnetite, and apatite are present in small amounts.
Several small bodies of gabbro-norite were found along the road be-
tween Bakersfield and Breckenridge Mountain about 1 mile northeast of
Hoosier Flat. The weathered surface of this rock is pitted due to the
almost complete removal of the feldspar through weathering. In addi-
tion, the rock is generally stained dark greenish brown from iron oxides
released upon weathering of the mafic minerals. The average gabbror
norite is a coarse-grained rock containing about 50 percent labradorite,
15 percent hypersthene, and diopside, 15 percent olivine, 10 percent horn-
blende, 5 percent spinel, and about 5 percent apatite, sphene, magnetite,
and ilmenite. The feldspar is calcic labradorite ( An,;o to An,i,s) and forms
large irregular and rounded crystals showing multiple twinning. It in-
cludes poikilitically rounded crystals of pale greenish diopside and is
surrounded in places by a rim also composed of diopside. Both hyper-
sthene and diopside are present, but with an excess of hypersthene over
diopside. The hypersthene forms rounded and irregular crystals showing
w^ak pleochroism from pale pink to pale green. Schiller structure is well
developed, especially in the larger crystals where one can see the arrange-
ment of thin plates of reddish-brown hematite in parallel lines. The diop-
side is in pale green rounded crystals. Olivine occurs in fairly well
formed crystals that have been somewhat rounded bj' magmatic corro-
30
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
^2 ' •^•^•i'vV"'-;
1953] STRATIGRAPHY 31
sion. Surround injj: many of the olivine crystals are two zones of which
the first is colorless amphibole, and outer or second is a myrmekitic inter-
growth of labradorite and pale green amphibole. In one thin section sev-
eral rounded olivine crystals were found surrounded by a rim of granular
pale green amphibole and bleb-like grains of dark green spinel. The am-
phibole is pale bluish-green hornblende in the form of irregular prisms
and needle-like crystals. Dark green spinel is common. It forms myrme-
kitic intergrowths with the hornblende and also occurs as inclusions in
the feldspar. Zircon, sphene, apatite, and magnetite are rare.
3Iode of Intrusion. The relationship of the gabbro to the enclosing
quartz diorite is not definitely known, but it appears to grade into the
quartz diorite in most places thus making the contact difScult to map.
However, in other places, notably the west side of the exposure in Kern
Canyon, it appears to be cut by numerous stringers of quartz diorite. The
gabbro and gabbro-diorite are therefore probably in part segregates of
the quartz diorite and were probably in part somewhat earlier. They may
represent local basic intrusions during the early stage of the Sierran in-
vasion.
Hornblendite and Other Basic Rocks
Small irregular and linear masses of coarse crystalline hornblendite,
hornblende diorite, and other basic rocks occur within quartz diorite
mainly in the southwestern portion of the quadrangle near Beale Hill.
Another crops out north of Pampa Peak, and another north of Rankin
Ranch on the west side of Walker Basin. The largest exposure which cov-
ers a quarter of a square mile occurs a mile northwest of Beale Hill;
others are much smaller.
The hornblendite and other basic rocks are extremely variable both as
to texture and mineral content. The most common type is coarsely crystal-
line black hornblendite made up of bladed hornblende crystals ranging
from a quarter of an inch to over an inch in length. Microscopically the
hornblendite is composed almost wholly of hornblende with only a minor
amount of andesine and secondary clinozoisite. The hornblende is green-
ish-brown in color and shows weak pleochroic colors in shades of pale
green and brown. In several sections there appears to be at least two
distinct forms of hornblende: (1) light green hornblende which is unal-
tered and (2) pale brown to colorless hornblende that is more or less
altered to clinozoisite. Anthophyllite is also present in small amounts.
Sodic andesine (Ana,;) occurs in small rounded crystals partiall}' altered
to sericite.
Occurring in the hornblendite are several dikelike bodies composed
almost wholly of coarse-grained oligoclase here referred to as leuco-
diorite (Johannsen, 1937). These bodies of leucodiorite do not appear
to represent direct crystallization from the magma, but because of their
cross-cutting relationships to the hornblendite and anthophyllite veins,
and their sharp contacts, they seem to represent intrusions at a later
stage in the igneous cycle (Anderson, 1933).
In thin section the leucodiorite has a hypautomorphic granular tex-
ture. The important feldspar is calcic oligoclase (An24 to Anoe), which
forms large, partially altered anhedral crystals that show both albite
and carlsbad twins. Enclosed within the larger oligoclase crystals are
small rounded grains of fresh untwinned albite. A few pale green pris-
matic crvstals of hornblende mav be found as well as a small amount of
32 BRECKENRIDGE MOUNTAIN QUADRANGLE [Bull. 168
colorless muscovite. Leucodiorite varies to hornblende diorite made up of
coarse crystalline hornblende and white plagioclase in about equal
amounts.
In thin section the hornblende diorite has a hypidimorphic granular
texture and is composed of plagioclase and hornblende in approximately
equal amounts. The feldspar, sodic andesine (Ausg), forms anhedral
crystals that show complex twins and no zoning. Secondary alteration to
sericite is common. Hornblende is pale brownish in color and slightly
pleochroic. It forms irregular stumpy prisms with twinning parallel to
the (100). Minor amounts of sphene, zircon, and magnetite are present
as well as such secondary minerals as sericite, chlorite, and clinozoi-
site. All these rocks are massive and occur as irregular bodies. Associated
with them are thin veinlike zones of greenish actinolite and anthophyllite,
and irregular lenslike bodies of leucodiorite which is composed almost
wholly of oligoclase. All of these basic rocks are probably segregates of
the quartz diorite containing an abundance of moisture as well as mag-
nesium and iron.
Commonly associated with the basic rocks, especially near Beale Hill
and north of Rankin Ranch, are layers of banded hornblende-biotite
gneiss made up of layers rich in hornblende alternating with layers con-
taining less. The banding in these layers is accordant to the foliation of
the enclosing quartz diorite. These are injection gneisses, probably local
phases of the quartz diorite high in water.
Pegmatite Dikes and Quartz Veins
Dikes of granite pegmatite ranging up to 50 feet thick, are locally
present in the granitic rocks; some are traceable for a mile. They are
most prominently developed along the northwestern and southeastern
margins of the large central mass of massive biotite quartz diorite of
lower "Walker Basin Canyon. The dikes appear to originate from this
rock and cut the foliated hornblende-biotite quartz diorite and gabbro
alike. They trend generally northeastward, more or less parallel to the
margins of the massive quartz diorite, and usually dip steeply toward it.
Other occurrences of pegmatite dikes are in the extreme southwest corner
of the quadrangle where there are numerous parallel dikes trending north-
west at the edge of the massive biotite quartz diorite. Then dikes trending
northwest also occur at the edge of the quartz diorite intrusion at Red
Mountain. Several pegmatites crop out on the north side of Kern Canyon
in the gabbro.
The pegmatite is a coarse, very uneven-grained white rock made up of
quartz and white orthoclase feldspar, and some microcline, in anhedral
crystals up to an inch or so in size. Some dikes are made up almost entirely
of milky quartz, others of feldspar. Small to medium-sized flakes of
muscovite and biotite are commonly present. Some dikes, notably two
large ones a mile west of Castro Ranch, and those on the north side of
Kern Canyon, contain crystals of black tourmaline up to 2 inches long
and half an inch thick.
The pegmatite dikes appear to have generated from massive biotite
quartz diorite along the margins of those intrusions and to have pene-
trated the older plutonic rocks into which it has intruded. The pegmatites
represent the latest and final .stage of the Sierran invasion in this area.
Lenticular veins of pure white milky quartz up to several feet thick
crop out in a number of places in the granitic rocks. They are commonly
associated with the pegmatite dikes. The quartz veins are not mineralized.
1953]
STRATIGRAPHY
33
■• *~" 'S'J^ ?-ei. ;-;
Figure 18. Union lava How. Walker beds below. Terrace gravel on Walker to right.
Caliente Wash two and a half miles east of Bena.
Tertiary System
Walker Formation
The name "Walker formation" first appeared in California literature
in a paper on Mt. Poso oil field in which V. H. Wilhelm and L< W.
Saunders, (1928, p. 9), described it as "a series of land-laid beds con-
sisting of sands and shales of characteristic greenish color, made up of
granitic and volcanic material, lying uneonformably below Temblor
Miocene and resting on granite, and penetrated bythree wells where it is
375 to 594 feet in thickness. " The name was again used by H. A. Godde,
(1928, pp. 5-10), in the east side oil fields of Kern County, "for lower
member of Temblor group ; is probably lower Miocene and may be equal
to Vaqueros formation, 0-1,200 feet thick, average 700 feet, uneonform-
ably underlies Temblor formation and rests uneonformably on granite."
The use of the name "Walker formation" for the basal land-laid
sediments of the east side oil fields of Kern County is now well estab-
lished, despite the fact that the name has previously been used in Amer-
ican literature. However, no mention has ever been made of the derivation
of the name nor has an outcrop section been described. This formation is
exposed at several areas in the east side foothills from Pogo Canyon
southward to Caliente Canyon, and reaches its maximum development
in Caliente Canyon.
Distrihuiion and Thickness. Within Breckenridge Mountain quad-
rangle, the continental Walker formation crops out in lower Caliente
34
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
^^'V
Figure 19. Walker beds exposed in cut on Highway U. S. 466, one mile west of Ilmon.
Canyon in the vicinity of the juncture with Walker Basin Creek. The sec-
tion exposed along the southeast bank of Walker Basin Creek, 1 to 2
miles northeast of Bena, may be taken as the type outcrop section of the
Walker formation. Here it consists of about 2,000 feet of terrestrial
sandstone, conglomerate and gritty clay that rests on quartz diorite. The
Walker conformably underlies the Ilmon basalt flow. Southeastward along
strike, the Walker formation thickens to 2,950 feet and grades into
fanglomerate mapped as the Bealville fanglomerate facies. Northwest-
ward from the type section, the Walker thins and extends out of the
quadrangle into Cottonwood Canyon. Only a few erosional remnants of
the Walker occur farther up this canyon within the quadrangle where
it consists of about 200 feet of gravel and sand.
Lithologic Character. The Walker formation is made up of light-gray
to pinkish-gray, well-bedded, moderately indurated granitic sandstone
and conglomerate. Fairly well-rounded pebbles, some of which are as
much as several inches in size, consist of granitic rocks and some
metamorphic rocks such as quartzite, phyllite, schist, and gneiss. Inter-
bedded in minor amounts, are poorly bedded greenish, gritty clays up to
20 feet thick. They resemble old soils and commonly contain small, white
calcareous nodules. Some clays are of a faint reddish tinge, but maroon-
red beds are notably absent in the Walker. Thin layers of gray- white
gritty marl are locally associated with the clays.
1953] STRATIGRAPHY 35
In the type section, the lower 650 feet of Walker formation consists of
interbedded light-jifray, arkosic congflomerate, sandstone and greenish
clay, with pebbles made up almost entirely of p:ranitic and metamorphic
debris. This is overlain by a bed np to 100 feet thick of pinkish-gray tuff
made np largely of angular fragments of white pumice and some of pink
rhyolite with prominent flow structure, averaging about half an inch in
size, but ranging up to 2 inches. The matrix is an ill-sorted light-gray
tuffaceous sandstone. This tuff member is generally well indurated and
is a marker bed traceable for nearly 4 miles in the type area, and again
shows up capping the hills northwest of Caliente ; a similar bed crops out
1 mile southeast of this town. The upper 1,200 feet of Walker formation
overlying the tuff bed in the type section is predominantly arkosic
pinkish-gray sandstone and conglomerate, made up of granitic and some
metamorphic debris, and a minor admixture of tuff fragments in some
layers. Thin interbeds of light reddish and green clays occur locally.
Southeastward, this upper member of the Walker thickens to about
2.000 feet near Ilmon, then grades laterally along strike into the coarse
Bealville fanglomerate.
In Cottonwood Canyon, the Walker formation is only about 200 feet
thick and conformably underlies the Freeman-Jewett shale. The Walker
here is made up largely of light-gray gravels composed of well-rounded
cobbles of granite, metamorphic, and some porphyritic rocks.
Age and Correlation. Silicified fossil wood, chiefly sycamore and oak,
occurs in the upper Walker beds above the tuff bed at several localities
about 2 miles north and 2 miles east of Bena. Fossil leaves of broad-
Jeaved trees have been found at one place on the south bank of Walker
Creek, below the tuff bed. However the age significance of this flora is
not known at this time. At one locality northeast of Bena a gastropod
was found of the genus Helix, a land snail.
In wells drilled on the eastern margin of San Joaquin Valley, the
Walker formation is found to lie above the basement complex and below
the Vedder sand, which in turn underlies the Freeman-Jewett shale
which carries a lower Miocene (Zemorrian) foraminiferal fauna. The
continental Walker formation is thus generally believed to be of lower
Miocene (Zemorrian) or Oligocene (Refugian) age, and is probably cor-
relative with the Tecuva formation at the south end of San Joaquin
Valley.
The lack of red beds in the Walker formation not only in Caliente Can-
5'on, but throughout its areal extent in eastern San Joaquin Valley is
noteworthy. All continental formations of Oligocene-lower Miocene age
throughout the Coast Ranges, and those in the Mojave Desert, such as
the Goler beds (Dibblee 1952) in El Paso Mountains, are made up largely
of red beds. Red coloration in sediments is the result of thorough oxida-
tion of iron salts which is believed to occur in a warm wet-and-dry cli-
mate. The Walker formation was apparently deposited under climatic
conditions unfavorable for complete oxidation of iron salts so that the
red coloration failed to develop. This is suggested by the color change
in its correlative, the Tecuya formation, at the south end of San Joaquin
Valley : the Tecuya formation consists of brilliant red and green beds
west of Grapevine Canyon, but eastward the colors give way to light-
gray and buff such as are characteristic of the Walker formation.
36
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
tri
( \
■i^
I ^ . -^s
. , ^'-
KiGURE 20.
Bealville fanglomerate in cut on U. S. Highway 466, three miles south of
Ihnon.
Bealville Fanglomerate
Definition. The unsorted boulder-gravel facies of both the Walker
and overlying Bena formations exposed in Caliente Canyon are mapped
as the Bealville fanglomerate.
Disfrihution and Thickness. The Bealville fanglomerate is exposed
from the town of Caliente westward along the south side of Caliente Can-
yon into the hills 3 miles south of Bena. The type section is designated as
the section exposed along the highway southward from Union, where the
formation consists of granitic fanglomerate that dips southward and
attains a thickness of over 7,000 feet. AVest of this section, the Bealville
fanglomerate grades laterally into both the Walker and Bena formations.
Lithologic Character. The Bealville fanglomerate in the vicinity of
the tj^pe section is a light-gray loosely consolidated mass of unsorted
granitic rubble made up of semi-rounded boulders of quartz diorite up
to 3 feet in diameter. The formation is a torrential fanglomerate almost
devoid of bedding, so much so that it appears at first glance to be granitic
basement. Only the finer facies made up of smaller boulders and cobbles
show rude bedding in road cuts that reveal the sedimentary origin of the
formation. The upper portion of the fanglomerate adjacent to the Edison
fault is made up largely of rubble of quartz diorite and hornblende diorite
similar to that exposed in place south of the fault. Eastward, in the
vicinity of Caliente, the Bealville fanglomerate becomes less coarse and
1953]
STRATIGRAPHY
37
is predominately a cobble conglomerate made up of rounded granitic
cobbles and boulders in a loose, sandy or greenish clay matrix.
Age and Correlation. The lower portion of the Bealville fanglom-
erate was deposited contemporaneously with the Walker formation of
lower Miocene-OHgocene age, into which it fingers westward. The upper
portion fingers westward into the Bena gravels of lower and middle Mio-
cene age. The formational contact between the Walker and Bena forma-
tions is not traceable through the Bealville fanglomerate.
Ilmon Basalt
Definition. The Ilmon basalt flow lies conformably above the Walker
formation in lower Caliente Canyon.
Distribution and Thickness. The Ilmon lava ranges from less than an
inch in thickness to 100 feet and is traceable through a series of isolated
outcrops from a point 2 miles west of Ilmon station northwestward for
about 3 miles to the west border of the map. Throughout this area, the
lava is overlain by the Bena gravels and sandstone. The most northwest-
erly outcrop of this lava flow is just beyond the western border of the
quadrangle about 3 miles northwest of Bena, where it is about 15 feet
thick and separates Walker formation below from Freeman-Jewett shale
above.
Lithologic Character. The Ilmon lava flow consists of basalt of a very
dark-brown color. It is highly vesicular, containing vesicles averaging
'^l^k
^,
^.^>-i^^-.:j
Figure 21. Ilmon lava flow a mile northeast of Bena. Bena gravel beds above and
Walker beds below. Small fault near left.
38 BRECKENRIDGE MOUNTAIN QUADRANGLE [Bull. 168
about half an inch in diameter, which are evenly distributed" and closely-
spaced. Some are filled or partly filled with secondary calcite. The rock
is dense, but generally shows small phenocrysts of feldspar. The rock is
massive and without flow structure.
Under the microscope the Ilmon lava is seen to be a basalt with a hyaloo-
phitic texture in which laths of plagioclase are set in a microcrystalline
and crystalline groundmass. Intermediate labradorite (Aneo to An64)
forms lath-shaped crystals that show both Carlsbad and albite twins.
Although the feldspar is unaltered, the groundmass appears to be made
up of dark brownish, cloudy, partially devitrified basic glass in which
are set skeletal augite crystals and numerous dustlike particles of mag-
netite. The unaltered augite is pale brown in color.
Age and Correlation. The Ilmon basalt is probably of lower Miocene
(Zemorrian) age, as it lies above the Walker formation (lower Miocene-
Oligocene) and the exposure out of the quadrangle 3 miles northwest of
Bena lies below the Freeman- Jewett shale of lower Miocene (Saucesian-
Zemorrin) age. The Ilmon lava may correlate with the andesite lavas
exposed in Cache Canyon northeast of Tehachapi, the nearest occurrence
of Tertiary volcanic rocks, or possibly with the basalt and dacite flows in
the Tecuya formation at the south end of San Joaquin Valley, all of which
are of lithology similar to the Ilmon lava.
Freeman-Jewett Shale
Definition, Distribution and Thickness. The equivalent of the lower
Miocene Freeman-Jewett silt of the east side San Joaquin Valley oil
fields crops out in Cottonwood Canyon just beyond the western border
of the mapped quadrangle, where it is made up of about 500 feet of
marine clay shale lying conformably between the Bena gravels above
and the Walker formation below. Southeast of this exposure, two out-
crops of this shale, separated by a fault, extend a short distance into the
quadrangle on the south side of the canyon. Southward the shale pinches
out between fluviatile sediments of the Walker and Bena formations.
Lithologic Character. The Freeman-Jewett shale is light grayish-
brown, thin-bedded, somewhat punky, semi-siliceous or diatomaceous,
and of light weight. It commonly contains thin laminae of fine silty sand.
Age and Correlation. The Freeman-Jewett shale encountered in wells
on the east side of San Joaquin Valley carries a lower Miocene (Sauce-
sian-Zemorrian) foraminiferal fauna.
Bena Gravels
Definition. The Bena formation is a series of terrestrial gravels of
lower and middle Miocene age lying conformably above the Walker
formation and Ilmon basalt and unconformably below the Kern River
gravels in lower Caliente Canyon. The Bena formation is the continental
facies of the lower and middle Miocene marine formations of eastern
San Joaquin Valley.
Distribution and Thickness. The hills 3 miles southeast of Bena are
designated as tlie type locality of the Bena gravels, where they attain a
thickness of about 2,500 feet. The formation is also well exposed from
Bena northwestward into Cottonwood Canyon, but only the southeastern
extremity of this exposure lies within the mapped quadrangle.
1953]
STRATIGRAPHY
39
Figure 22. Walker beds faulted against Bena gravel. Two mile.s we.st of Pampa Peak.
Bena gravel on top of ridge, Walker beds on slopes, dipping southwest to the left.
, Lithologic Character. The Bena formation is a poorly consolidated
series of cobble and pebble gravel, arkosic sand, and interbedded gritty
clay, all of fluviatile origin. The pebbles and cobbles making up the
gravels are well-rounded, some as much as a foot in diameter, but average
much less. They are composed mainly of granitic rocks, chiefly quartz
diorite and lesser amounts of gneiss, quartzite, schist, quartz, andesite,
rhyolite, volcanic porphyries, and translucent chert, set in a matrix of
gray to ferruginous rusty-brown sand. The gravels are intimately asso-
ciated with ill-sorted coarse- to fine-grained, pebbly arkosic sands,
usually gray-white but locally iron-stained to rusty buff. Interbedded in
places with the gravel and sand are gray gritty clays.
The type section of the Bena formation has no definite sequence, as
it is made up of a heterogeneous series of gravel, sand, and clay as de-
scribed above, with gravel predominating. However, the lower 1,000 feet
of the type section contains a bed about 100 feet thick of granite boulder
gravel. This layer occurs about 500 feet above the base of the formation.
Another occurs as a thick lens about 500 feet stratigraphically higher,
but is traceable for only half a mile. Southward along strike, the lower
1.000 feet of Bena formation interfingers with and finally grades into
the Bealville granitic fanglomerate as does the underlying Walker
formation.
The Bena formation is practically all of continental origin within
Breckenridge Mountain quadrangle, but marine fossils found at several
localities indicate local marine fingers. The basal sandstone immediately
40
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
Figure 23. View across Cottonwood Canyon. Note Freeman-Jewett shale in
foreground. Two miles west of Pampa Peak.
overlyinw the Union basalt east of Bena appears to be marine, and has
yielded some small pelecypods and some echinoid fragments. The Bena
formation is known to grade rapidly down dip and to the west into forma-
tions of marine origin. This is attested to by wells drilled south of Bena
which encountered marine shale and silt carrying foraminifera and thin-
shelled mollusks at shallow depths. A short distance beyond the western
border of the cjuadrangle in Cottonwood Canyon, the Bena gravels overlie
the Freeman-Jewett shale and grade laterally into the marine Olcese
sandstone and Round Mountain shale to the north.
Age and Correlation. The pelecypod fossils found in the Bena forma-
tion are indeterminate, but the age of the Bena formation is determined
from that of the marine formations into which it grades westward. The
basal portion grades into the Olcese sand, of lower Miocene (Saucesian
or "Temblor") age. The remainder grades into the Round IMountain
shale, of middle Miocene (Relizian-Luisian) age. The "Santa i\Iar-
garita" sand of upper Miocene (^lohiiian) age is not represented in the
mapped area where it is overlapped by the Kern River gravels, but crops
out in the low foothills to the west at and near the mouth of Cottonwood
Canyon, where it in part overlies and in part grades into the Bena gravels.
Kern River Gravel
Definition. The name "Kern River Beds" was first applied by F. M.
Anderson in 1905 (Anderson, 1905, pp. 187-188, 191) to the entire 3,000
1953]
STRATIGRAPHY
41
Figure 2 4.
Terrace cut in Bena and underlying granitic roclis. Nortli side of Caliente
Creek between Bena and llmon.
foot series of sediments, including the marine Miocene, exposed 2 to 6
miles east of Oil City, Kern County. In a later paper (Anderson, 1911,
pp. 95, 111), he redefined as the "Kern River group" the terrigenous
gravels, sands, and clays, including the Kern oil measures of Neocene
age, uneonformably overlying the Miocene "Temblor group". This
usage has generally been followed by later authors (Stevens, 1924, p. 33 ;
Fox, 1929, p. 103; and others), who regard the "Kern River series"
as the unconsolidated continental gravels, sands and clays of Pliocene-
Pleistocene age.
Distribution and ThicJfness. "Within the mapped quadrangle, the
Kern River gravel, of Pliocene age, crops out only in the hills immedi-
ately south of Bena. This exposure extends another mile and a half to
the west out of the quadrangle. The Kern River gravel is extensively
exposed in the low foothills beyond the western border of the map west
of Cottonwood Canyon, and to the northwest, where it dips very gently
west under San Joaquin Valley. A complete section of the Kern River
gravels is about 1,200 feet thick in the foothills, with thickness increasing
down dip into the valley. However, only the lower 600 feet of the Kern
River gravel beds lie within the mapped quadrangle, cropping out in
the hills south of Bena and dipping westward.
Lithologic Character. The Kern River gravel is of terrestrial origin
and is generally poorly bedded, loosely consolidated and of a prevailing
42
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
H '■*i
)^isirf#>Sr.: :..>' ■'- ::
Figure 25. Breckenridge Mountain and Walker Basin.
brown-gray color. The gravel is composed of poorly sorted, rounded to
sub-rounded pebbles, cobbles, and some boulders of a great variety of
rock types, including volcanic debris ranging from rhyolite to basalt,
some porphyritic, some dense, vesicular, or with prominent flow struc-
ture, and a considerable amount of quartzite, granitic rocks, gneiss,
schist, phyllite, quartz, translucent milky chert, and other less common
types. They are set in an ill-sorted gray sandy matrix. In the hills south
of Bena, the basal 500 feet of the Kern River gravel is very coarse, being
made up of large cobbles and boulders up to 2 feet across. This is over-
lain by about 600 feet of gray gravelly sand, of which only the basal
portion lies within the mapped quadrangle. This is in turn overlain by
about 100 feet of coarse cobble gravel which crops out beyond the west
border of the map.
The relationship between the Kern River gravel and the underlying
Bena gravel in the hills south of Bena is probably a disconf ormity. North-
west of Bena, outside the mapped area, the relationship is a slight angular
unconformity in which the Kern River gravel overlaps the "Santa Mar-
garita" onto the underlying Bena gravel up dip with a discordance of
about 10 degrees.
Age and Correlation. The Kern River gravel is the youngest Tertiary
formation on the east side of San Joaquin Valley, and is of Pliocene
age, possibly extending up into the Pleistocene. It is everywhere of con-
tinental origin, although it thickens and becomes fine-grained in the
middle of the valley. It correlates with the non-marine Tulare forma-
tion of the west side of the valley.
1953] STRUCTURE 43
Volcanic Breccia
On the ridge south of Walker Basin 2 miles southeast of Rankin Ranch
is an outcrop of frray volcanic breccia, which appears to lie upon the
quartz diorite with a westerly dip, but may be a volcanic plug. The rock
is made up of angular fragments up to 10 inches long of gray to pink
rhyolite or dacite, some showing prominent flow-structure, in a hard
tuff matrix. In addition to the dacite rubble, there are fragments of
quartz diorite. The rock appears to be pyroclastic and is of somewhat
similar lithology to the rhyolite-dacite breccia in the Bealville f anglom-
erate a mile east-southeast of Caliente, but its isolated occurrence sug-
gests that it is a vent breccia.
Pleistocene Sediments
Terrace Deposits
The largest terrace gravel deposit is on the north side of lower Caliente
Canyon. This deposit ranges up to 100 feet in thickness and consists of
granitic gravel and sand. Its depositional surface, about 100 feet above
the present level of the canyon, is consequently much dissected. Other
terrace gravels of smaller extent occur farther up the canyon, and one
large one is in Tehachapi Canyon a mile east of Bealville. These terrace
gravels are of late Pleistocene age.
Alluvium
Recent alluvium is most extensive in Walker Basin, where it covers an
area of about 6 square miles, at an elevation of over 3,300 feet. The
thickness here is unknown, but probably exceeds 300 feet, and may be
as much as 1.000 feet. The alluvium here consists of granitic pebbly sand
admixed with loamy silt.
Alluvium fills the flood plain of Caliente Canyon and those of some
of its tributaries, the valley of White Wolf Ranch, and Kern Mesa at
the extreme southwest corner of the quadrangle. The alluvium in all
these areas is composed of granitic pebbly sand admixed with silty
loam, and is as much as 150 feet thick.
STRUCTURE
Structure of the Pre-Cretaceous Complex
The metasediments of the southern Sierra Nevada have been so widely
intruded by granitic rocks that little remains of their original structure.
However, the residual inclusions of these old sediments indicate an
attitude with a general north to northwest strike and near-vertical dip.
Except for some local variations discussed below, this attitude is general
throughout the mapped quadrangle.
The band of the Kernville series in the southeastern portion of the
quadrangle strikes east of north and dips steeply east. Northeast of
Walker Basin this band strikes about N. 40° W. and dips very steeply
southwest. In Cottonwood Canyon remnants of the Pampa series indi-
cate an S-shaped flexure in vertical beds concave southward at Castro
Ranch and convex southwestward where Cottonwood Canyon passes
off the map. Dips, though nearly vertical, suggest a south-plunging syn-
cline at Castro Ranch and a southwest-plunging anticlinal nose to
the west.
The attitudes of the foliation in the quartz diorite conform to that of
the various remnants of Kernville and Pampa series wherever they exist
44
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
throughout the quadrangle and are thus believed to infiicate the pre-
existing structure of the metasediments. In general, it may be said that
the dip of the foliation is vertical and trends nearly north-south
in the southern portion of the quadrangle, gradually swinging to north-
west throughout the northern portion of the quadrangle. A local east-
west trend is developed in the northwestern portion of the quadrangle
northward from the Cottonwood Canyon flexure.
Structure of the Tertiary Sediments
The Tertiary sediments exposed in the southwestern foothills in the
vicinity of lower Caliente Canyon are tilted about 20° SW., toward San
Joaquin Valley. In the hills south of lower Caliente Creek the sediments
become folded into a broad, westward-plunging syncline, apparently
from drag on the Edison fault which brings up the basement complex
on the south. In the hills southeast of Ilmon, the beds dip south at in-
creasingly steep angles up to 60°, directly into the Edison fault. South-
east of Caliente these beds become folded into a rather sharp syncline,
a drag fold on the Edison fault as it dies out eastward.
Faults
Kern Canyon Fault. A considerable amount of material has been pub-
lished on the Kern Canyon fault, traceable for some 40 miles northward
from Kernville along Kern Canyon. The geomorphologic features along
Figure 26. Walker Basin toward the north. Breckenridge fault follows west edge of
valley to left.
1953]
STRUCTURE
45
Figure 27. View north down Havilah Canyon. Kern Canyon fault follows canyon
and passes through saddle in distance. Quartz diorite exposures.
this fault have been described in detail by Lawson (1906). Miller and
•Webb (1940) have mapped the fault through Kernville quadrangle and
state that it is a fault line scarp, but arrive at no conclusions regarding
its movement. Recently this fault has been mapped through Isabella
quadrangle by Treasher (1940, abst.) who states that north of Isabella
it is a steep normal fault dipping westward, but southward it reverses
its movement and becomes a steep reverse fault dipping in the same
direction. Despite all the work done on the Kern Canyon fault, little
is known regarding its movement as it lies within rocks of the basement
complex and is a strike fault where it cuts through the Kernville series.
South of Kernville the Kern Canyon fault is traceable slightly west
of south through Bodfish. It extends for about 3 miles up Havilah
Canyon and dies out just south of Havilah Pass. In Havilah Canyon the
fault is largely within quartz diorite but is physiographically well ex-
pressed, forming a long straight scarp just west of the creek and facing
eastward, indicating relative upward movement of the west block.
Breckenridge Fault. About a mile west of the southward-dying Kern
Canyon fault, appears another parallel fault which follows the base of
the steep east slope of Breckenridge Mountain. This fault is named the
Breckenridge fault and is traceable from the northern border of the
quadrangle due southward for about 9 miles to Rankin Ranch where
it dies out. The fault is a member of the Kern Canyon fault zone and
separates the steep eastern front of the Breckenridge Mountain plateau
from the flat valley of Walker Basin. The Breckenridge fault has not
46
BRECKENRIDGE MOUNTAIN QUADRANGLE
[BuU. 168
V'%f^
FlGUIlE
View east across scarp of Kern River fault. .Mouth of Kern River Ganyon.
been found exposed, but its existence is clearly indicated by the abrupt
rise of the Breckenridge Mountain front along a remarkably straight
base. Spurs of this steep mountain front are abruptly terminated along
this line by triangular facets facing Walker Basin, and canyons between
the spurs are narrow, V-shaped and steep, with small alluvial fans at
their mouths. Movement on the fault is mainly if not entirely vertical,
with the west block relatively elevated at least as much as the height of
Breckenridge Mountain above "Walker Basin, or more than 4,000 feet.
The northern portion of the Breckenridge fault appears to divide into
two branches, both of which probably die out at or near the northern
border of the quadrangle. The Breckenridge fault and its northwestern
branch trend generally parallel to the foliation of the quartz diorite in
this area.
Dougherty Fault (?). A marked topographic break extending from
the northwest corner of the mapped quadrangle southeast for about
5 or 6 miles through and perhaps beyond Hoosier Flat suggests the
existence of a fault which will be referred to as the Dougherty fault ( ?).
The topographic evidence of faulting is indicated by an alignment of
saddles on ridges ; canyons, such as Dougherty, following this line, by the
sudden change of course of the Kern River from south to west ; and by
the sudden break in slope between the high upland mass of Breckenridge
Mountain on the northeast and the much lower mountains to the south-
west. Further evidence of faulting along this line is indicated in Kern
1953]
STRUCTURE
47
Figure 29. Cracks along trace of White Wolf fault north of U. S. Highway 466 near
Caliente ; cracks were developed during Tehachapi earthquake of 1952. Photo by Lauren
A. Wright.
Canyon where there is a zone of breeciated rock and some gouge, up to
about 30 feet wide, but it is not clear cut. On the highway near and
parallel to this supposed fault, there is a steep west-dipping plane of
movement bounded by vertically grooved quartz diorite. The plane is
parallel to the local foliation in the quartz diorite, and may thus be a
slippage plane developed along a plane of foliation.
The nature of the movement of the supposed Dougherty fault is not
known, but the topography suggests relative elevation of the northeast
block. This supposed fault is aligned with the Poso Creek fault northwest
of the mapped area, a fault traceable for some 15 miles, but with the
upthrown block on the southwest.
Kern River Fault. The Kern River fault (not to be confused with the
Kern Canyon fault) ; is well developed northwest of the mapped area,
especially at the mouth of Kern Gorge. It is a normal fault that dips
southwest, is traceable for about 15 miles, and forms a very prominent
scarp about 2,000 feet high between granitic mountains on the northeast
and low sedimentary foothills on the southwest. At Kern Gorge, it
dips 55°-60° SW.
The Kern River fault extends about 2 miles east-southeast into Breck-
enridge Mountain quadrangle where it dips 76° to 80° S. and forms the
southern escarpment of Mount Adelaide. The fault is here marked by
about 2 feet of gouge with vertical fault grooves. It occurs within the
foliated quartz diorite, and trends and dips parallel to the foliation of
48
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
Figure 30. Cracks in earth between Caliente and Tehachapi Creeks;
cracks are result of movement during Tehachapi earthquake of 1952.
Widest point in crack is 59 inches ; depth about 6 feet. Photo courtesy
SoutlLcrn Pacific Railroad.
this rock between Mount Adelaide and Kern Gorge. Like the Dougherty
fault ( ?), the Kern River fault appears to have been developed along a
plane of foliation in the quartz diorite.
Cottonwood Canyon Faults. About a mile south of Cottonwood Can-
yon, a normal fault that dips 60° NE. brings a block of quartz diorite and
schist — the schist having a strike parallel to the fault — against southwest-
dipping Tertiary sediments that form the northeastern block. A similar
fault occurring about a mile farther south, has a more easterly trend
parallel to the strike of the schist on the south block.
Within 2 miles beyond the western border of the quadrangle in Cotton-
wood Canyon, there are many minor faults, mostly normal with the up-
thrown blocks on the southwest or west, as indicated by their effect on
the Tertiary sediments. These faults curve around from northwest to
north, and nearly all of them, including those lying within the quad-
rangle, are strike faults following the trend of the Pampa schist around
the Cottonwood Canyon flexure. Such a relationship indicates the faults
have originated along foliation planes in the schist which acted as planes
of slippage during tectonic movements.
1953]
STRUCTURE
49
Figure 31. Crack in earth above Tunnel 4, Southern Pacific Railroad.
Photo courtesy Southern Pacific Railroad.
Bena Faults. About a mile northwest of Bena are two minor faults,
named the Bena faults, trending about N. 70° W. and cutting the Ilmon
basalt. The larger of these is traceable for about half a mile and has a
vertical displacement of about 25 feet, upthrown on the north. This fault
is about vertical.
Ilmon Fault. The Ilmon fault is about 2 miles southwest of Ilmon
station and trends N. 45° W. for about a mile in Bena gravels. This fault
is of doubtful existence, but is suggested by probable displacement of a
boulder conglomerate bed. The upthrown block is probably on the south-
west.
Baker Fault. The Baker fault occurs northwest of Caliente and trends
about N. 45° AV. for at least a mile. It is a normal fault dipping about
65° NE., and brings quartz diorite on the southwest against Walker beds
on the northeast which dip into the fault.
Edison Fault. The Edison fault is a major normal fault dipping
north, and wells drilled west of the mapped quadrangle indicate this
50 BRECKENRIDGE MOUNTAIN QUADRANGLE [Bull. 168
fault to extend, although concealed, for a considerable distance under
San Joaquin Valley southeast of Edison where it trends about N. 60° W.
and bounds the Edison oil field on the north. This fault extends eastward
for about 9 miles into the hills of the southwestern portion of Brecken-
ridge Mountain quadrangle where it is exposed at the surface and trends
roughly east. This fault brings the basement complex up on the south
against Tertiary sediments on the north with maximum displacement of
more than 5,000 feet at the western border of the map, gradually decreas-
ing eastward. The fault is exposed at many places where it is marked by
several feet of mylonite, gouge, and pulverized rock, and dips fro'-'i
28° to 60° N. Its crooked surface trace over the hills is attributed to its
low dip at many places, especially in the western 3 miles where it dips
only 30°.
The Edison fault was definitely active during deposition of the Beal-
ville fanglomerate as the upper portion of this formation adjacent to the
fault is made up of angular rubble of hornblende diorite rocks such as
are exposed on the upthrown southern block. However, in marked con-
trast to the other major faults in the southern Sierra, the Edison fault has
no topographic expression. It is obviously an old, dead fault, probably
active during Oiigocene, Miocene and perhaps Pliocene time, but inactive
since that time.
The low dip of this fault may be attributed to a regional southward tilt
of the area during Pleistocene time when the fault was inactive. This
southward tilt would lessen the dip of this north-dipping fault.
White Wolf Fault. A major fault known as the White Wolf fault
trends about N. 50° E. beyond the southern border of the quadrangle
and bounds the steep northwestern front of Bear Mountain. Relative
upward maximum displacement of the southeastern block amounts to
many thousand feet. This fault was traced for about 3 miles northeast-
ward into Breckenridge Mountain quadrangle northeast of White Wolf
Ranch, and disappears at Tehachapi Creek. It occurs within biotite-
hornblende quartz diorite, but is marked by several feet of gouge and
cruslied rock. The rock on the northwestern or down-thrown block is
highly crushed within a mile of this fault. In marked contrast to the
nearby Edison fault, the White Wolf fault is well expressed topographi-
cally indicating it to have been active during Quaternary time.*
Structural Blocks
The Breckenridge Mountain quadrangle takes in portions of four tec-
tonic blocks within the southern Sierra Nevada, bounded by major faults.
They are :
1. Western block
2. Eastern block
3. White Wolf block
4. Bear Mountain block
Western Block. The major portion of Breckenridge Mountain quad-
rangle lies within the Western or Greenhorn Mountain block of the Sierra
* The recency of activity of the White Wolf fault is attested to by the violent earthquake
of July 21, 1952, which originated on this fault. This developed a discontinuous
.'series of fault fractures at the surface along or near the entire 20-niile known trace
of the White Wolf fault, including the northeastern portion lying within the mapped
Quadrangle. The fractures vary considerably in trend, dip, and movement, but dis-
placements were as great as 3 feet and in general indicated the White Wolf fault to
be of the thrufet or reverse type in which the southeastern block was displaced
upward and northward relative to the northwestern block.
1953] GEOLOGIC HISTORY 51
Nevada and is bounded by the Kern Canyon fault on the east. Within
Breckenridge ^lountain quadrangle, it is a block of basement complex
overlain by Tertiary sediments on its southwestern margin and is
bounded on the east by the Kern Canyon-Breckenridge fault zone and
partially terminated on the south by the Edison fault. The block is
elevated, relative to the Eastern block, along the Kern Canyon-Brecken-
ridge fault zone and tilted gently westward toward San Joaquin Valley.
In the extreme northwestern part of the quadrangle, this block breaks
into several minor blocks separated by the Kern River and Dougherty
faults.
Eastern Block. The Breckenridge Mountain quadrangle takes in only
a very small portion of the Eastern or Main block of the Sierra Nevada
lying between the Kern Canyon and Sierra Nevada faults. This is a
block of basement complex bounded on the west by the Kern Canyon-
Brepkenridge fault zone. "Within the mapped quadrangle, the block in-
cludes Red Mountain on the west flank of Piute Mountain range which
forms the main mass of the southern portion of the Eastern block, Havilah
Pass, and the alluviated valley of Walker Basin.
The southern portion of the Eastern block has been tilted westward,
having been elevated along Piute Range and depressed relative to the
Western block along the Kern Canyon-Breckenridge fault zone. South
of Walker Basin, where the Breckenridge fault dies out, the Eastern and
Western blocks are united.
White Wolf Block. The southwestern portion of the quadrangle takes
in a portion of the White Wolf block, a block of basement rocks between
the Edison and White Wolf faults. The block wedges out east of Beal-
ville where the two faults approach each other, but widens westward into
San Joaquin Valley as the faults diverge. It is tilted gently westward
■along with the adjacent Western block toward San Joaquin Valley.
Bear Mountain Block. Only the extreme northern tip of the uplifted
Bear Mountain block of basement rocks lies within the mapped-quad-
rangle. The block is bounded by the White Wolf fault on the nothwest
and the Garlock fault some 20 miles to the southeast. The Bear Mountain
block is elevated between the two faults and Bear Mountain probably
represents the maximum uplift. Northwestward where the White Wolf
fault dies out, this block ramps into the Western block.
GEOLOGIC HISTORY
Paleozoic (f): Deposition. The Kernville and Pampa series, the old-
est formations in Breckenridge quadrangle, were deposited probably
during late Paleozoic and perhaps early Mesozoic time in a widespread,
open sea as alternating sand, silt, clay, and limestone beds. These sedi-
ments accumulated to a tremendous thickness on a sea floor which must
have subsided continuously during deposition resulting in a very deep
burial of the lower sediments.
Jurassic: Orogeny. After the Kernville and Pampa sediments were
deposited the entire Sierra Nevada region was affected by a great orogeny
known as the Nevadan orogeny at the close of Jurassic time. This dias-
trophism resulted in the entire region emerging from sea and caused
the thick sedimentary series to be tightly compressed into sharp, perhaps
52 BRECKENRIDGE MOUNTAIN QUADRANGLE [Bull. 168
isoclinal folds trending generally north-south, indicating an intense
east-west compressive force. The great depth at which the sediments be-
came infolded resulted in dynamic and thermal metamorphism causing
them to become recrystallized into quartzite, schist, and marble.
The metamorphism of the Kernville and Pampa series was accompanied
or followed by widespread invasion of granitic magmas. These appear to
have been intruded in several waves in which quartz diorite was gradually
emplaced first into the Kernville and Pampa series bed by bed, causing
foliation to develop. Two small stocks of gabbro-diorite were intruded
with the quartz diorite in the western part of the quadrangle. The inva-
sion of these granitic magmas culminated in several large intrusions of
quartz diorite in irregular masses. The granitic invasions became so
widespread as to form the Sierra Nevada batholith leaving only small
pendants of the original Kernville and Pampa series. The Nevadan
orogeny no doubt resulted in the building up of high mountains in the
mapped area as well as throughout the Sierra Nevada region. The de-
velopment of pegmatites along fissures of the crystallized granitic rocks
represents the final stage of the granitic invasion.
Cretaceous-Eocene : Erosion. The Cretaceous-Eocene record is lack-
ing within Breckenriclge Mountain quadrangle. This was a time during
which the mountains that rose during the Nevadan orogeny supposedly
were eroded. There were probably several recurrent periods of uplift
and erosion during this long interval, but the region was reduced to low
relief at the end of Eocene time.
Oligocene: Diastrophism and Deposition. During Oligocene time
much of the southern Sierra Nevada region, including the eastern por-
tion of Breckenridge Mountain quadrangle, was re-elevated into rugged
mountains. Some of the local faults, such as the Edison fault, probably
originated and became active during this disturbance.
The mountains developed during the Oligocene orogeny underwent
erosion by torrential storms, and the eroded rubble was dumped in a
valley emerging from these mountains, at the present site of Caliente
Canyon, to form the Bealville fanglomerate which accumulated to a great
thickness during Oligocene time. Immediately beyond this alluvial fan,
finer material was carried by out-flowing streams into the margin of San
Joaquin Valley and deposited as alluvial gravels and sands of the Walker
formation. Some volcanic explosive activity in a nearby area resulted in
an admixture of pumice fragments and tuffaceous material in the Walker
sediments.
Miocene : Deposition. During Miocene time, the northeastern portion
of Breckenridge Mountain quadrangle continued to undergo erosion, and
deposition of the torrential Bealville fanglomerates continued uninter-
rupted at the present site of Caliente Canyon.
Deposition of the Walker beds was followed by local volcanism result-
ing in the extrusion of the Ilmon basalt at the site of lower Caliente
Canyon. This was in turn followed by accumulation of the Bena alluvial
gravels and sands on the site of the present foothills which was the margin
of the San Joaquin Valley during Miocene time. The local volcanism was
also followed by submergence of the San Joaquin Valley alluvial plain
under a shallow sea which persisted through the Miocene, and which
1953] MINERAL RESOURCES 53
barely extended from the west into Breckenridge Mountain quadrangle
as indicated by the occurrence of the Freeraan-Jewett marine shale under
the Bena gravels and by some local marine sands in the Bena gravels.
The Edison fault continued active through Miocene time and formed a
north-facing scarp between the elevated White Wolf block on the south,
in which plutonie rocks were exposed and undergoing erosion during at
least part of Miocene time, and the depressed block on the north in which
sediments were deposited.
It is not known how much of the area of the mapped quadrangle under-
went deposition during Oliogocene and Miocene time, but it is probable
that Tertiary fluvatile sediments covered most if not all of the south-
western half.
Pliocene: Diastrophism and Deposition. In early Pliocene time, fol-
lowing deposition of the Bena gravels, the region probably was slightly
uplifted, which resulted in erosion of the granitic rocks and the previ-
ously deposited Tertiary sediments. The material eroded was carried
westward and deposited during Pliocene time as terrigenous gravels of
the Kern River formation on the eastern San Joaquin Valley which
emerged from the sea in late Miocene or early Pliocene time to become a
broad alluvial plain.
Pleistocene : Cascadian Orogeny. Early Pleistocene time was a period
of uplift and erosion of the Sierra Nevada region, and constitutes a
major phase of the Cascadian orogeny. During this disturbance the en-
tire area lying within the quadrangle was tilted westward, was eroded,
and the present stream pattern developed. This great regional uplift in-
volved the Tertiary sediments deposited at the margin of San Joaquin
Valley and the area of granitic rocks now exposed south of the Edison
fault causing erosion of both to form the present foothills. The Edison
■fault, active during Tertiary diastrophism and deposition, apparently
was inactive during the Pleistocene orogeny. However, most of the other
major faults and resultant fault blocks probably originated during this
disturbance.
Middle Pleistocene time was apparently a time of relative quiescence
when the Breckenridge Mountain quadrangle as well as much of the
Sierra Nevada region underwent erosion to late maturity or old age
stage of the first cycle of erosion.
Late Pleistocene time was the final and culminating stage of the Cas-
cadian orogeny when the Sierra Nevada region was uplifted to its present
height. Within the mapped quadrangle, the major faults other than the
Edison fault were active during this disturbance resulting in differential
elevation of the fault blocks to their present heights. This re-elevated
region is being eroded mainly by deepening of the stream channels, and is
now in the late youth or early maturity stage of a second cycle of erosion.
MINERAL RESOURCES
Oil and Gas
A total of ten wells has been drilled for oil or gas in Breckenridge
Mountain quadrangle, all in the vicinty of Bena. Most of these were
drilled prior to 1917, so that records are poor or lacking.
In sec. 23, T. 30 S., R. 30 E., four wells drilled in a canyon 2 miles
south of Bena to depths ranging from 600 feet to 2,000 feet, prior to 1917.
54
BRECKENRIDGE MOUNTAIN QUADRANGLE
[Bull. 168
he- ^:^ .'■
Figure 32. Tungsten Chief mill.
Two of these were reported to have produced a small amount of heavy
oil along with water. In 1944, Gene Reid Company drilled No. "Tejon"
3 near one of these old producers to 2,700 feet and abandoned it without
obtaining production. Four shallow dry holes were drilled southwest of
these in sees. 22 and 27, T. 30 S., R 30 E., and abandoned. In 1945, Gene
Reid Company drilled its No. "Tejon" 4 in sec. 14, T. 30 S., R. 30 E., to
2,700 feet and abandoned it without showings. In 1929, a dry hole was
drilled at Bena by Elmer Oil Company to a reported depth of 5,057 feet.
All of the above wells were spudded in westward-dipping Bena gravel,
and the deeper ones probably bottomed in the Walker beds. Several, if
not all, of the wells encountered shallow marine sands and shales of prob-
able middle Miocene age at shallow depths.
It is hardly likely that any oil or gas in commercial quantities will ever
be produced from Breckenridge Mountain quadrangle as the Tertiary
formations are limited to lower Caliente Canyon, and all are exposed
without structural closure. Stratigraphic conditions are not favorable
as the formations are made up largely of coarse terrestrial gravels and
sands.
Tungsten
Mining activity within Breckenridge Mountain quadrangle is confined
almost entirely to the area of metaraorphic rocks north of Walker Basin
where small quantities of tungsten ore in the form of scheelite are mined.
The scheelite occurs in metamorphic zones in crystalline limestone in
contact with dikes of quartz diorite. These contact zones are made up
1953] REFERENCES CITED 55
largely of crystalline masses of red-brown garnet, and contain consider-
able admixtures of calcite, quartz, gray epidote, diopside, clinozoisite
and small quantities of scheelite. The ore is of low grade. The zones are
as much as 25 feet thick and are vertical, striking west of north.
A total of 15 workings has been developed and mining is done chiefly
along horizontal tunnels and inclines. All are in the prospect stage and
are idle at present. Most of these workings are on a group of claims owned
by the Tungsten Chief Mining Company. There is no mill at present.
REFERENCES CITED
Anderson, Alfred L. (1933) An occurrence of giant hornbleudite : Jour. Geology, vol.
41, pp. 89-98.
Anderson, F. M. (1905) A stratigraphic study in the Mount Diablo Range of Cali-
fornia : California Acad. Sci. Proc, 3rd Ser., vol. 2, pp. 187-188, 191.
Anderson, F. M. (1911) The Neocene deposits of Kern River, California and the
Temblor basin : California Acad. Sci. Proc, 4th Ser., vol. 3, pp. 95, 111.
Beach, J. H. (1948) Geology of the Edison oil field, Kern County, California, in Struc-
ture of tvpical American oil fields, a svmposium : Am. Assoc. Petroleum Geologists,
vol. Ill, pp. 58-87.
Buwalda, J. P. (1915) Structure of the southern Sierra Nevada, California: Geol.
Soc. America Bull., vol. 26, p. 403.
Buwalda, J. P. (1920) Fault system at the southern end of the Sierra Nevada, Cali-
fornia : Geol. Soc. America Bull., vol. 31, p. 127.
Buwalda, J. P. (1935) Tertiary tectonic activity in the Tehachapi region, California:
(abst) Geol. Soc. America Proc, 1934, p. 312.
Dibblee, T. W., Jr. (1952) Geology of the Saltdale quadrangle, California: California
Div. Mines Bull. 160.
Edwards, E. C. (1943) Edison oil field, in Geologic formations and economic develop-
ment of the oil and gas fields of California : California Div. Mines Bull. 118, pt. 3,
pp. 576-577.
Forbes, H. (1931 ) Geologic reports on dam sites in the San Joaquin River Basin, Cali-
fornia : Isabella, Borel and Bakersfield dam sites on the Kern River. The San
Joaquin River Basin, California : Dept. Pub. Works, Div. Water Res. Bull. no. 29,
appendix C, pp. 598-()06.
Fox, L. S. (1929) Structural features of the San Joaquin Valley, California: Am.
Assoc. Petroleum Geologists, Bull., vol. 13, No. 2, pp 103.
Godde, H. A. (1928) Miocene formations of the east side fields of Kern County, Cali-
fornia : California Div. Mines and Mining, Summary of operations, California oil
fields, vol. 14, no. 1, pp. 5-15.
Hake, B. F. (1928) Scarps of the southwestern Sierra Nevada, California: Geol. Soc.
America, Bull., vol. 39, pp. 1017-30.
Hoots, H. W. (1930) Geology and oil resources along the southern border of San
Joaquin Valley, California : U. S. Geol. Survey Bull. 812, pp. 243-332.
Johannsen, Albert (1937) A descriptive petrography of the igneous rocks, vol. 3, pp.
144-146, Univ. Chicago Press.
Lawson, A. C. (1904) Geomorphogeny of the upper Kern Basin, California: Univ.
California Dept. Geol. Sci., Bull., vol. 3, pp. 291-386.
Lawson, A. C. (1906) Geomorphic features of the middle Kern, California: Univ.
California, Dept. Geol. Sci., Bull., vol. 4, pp. 397-409.
Louderback, G. D. (1920) Report on geologic conditions in Hot Springs Valley in con-
nection with Isabella reser\oir site, in Water resources of Kern River and adjacent
streams and their utilization : California State Dept. Engineering Bull. no. 9,
pp. 134-137.
Locke, A., Billingsby, P., Mayo, E. B. (1940) Sierra Nevada tectonic pattern: Geol.
Soc. America Bull., vol. 51, pp. 513-540.
56 BRECKENRIDGE MOUNTAIN QUADRANGLE [Bull. 168
May, J. C, and Hewitt, R. L. (1948) The basement complex in well samples from the
Sacramento and San Joaquin Valleys, California : California Jour. Mines and Geol-
ogy, vol. 44, pp. 129-158.
Miller, W. J. (1931) Geologic sections across the southern Sierra Nevada of Cali-
fornia : Univ. California Geol. Sci., Bull., vol. 20, pp 331-360.
MHler, W. J., Webb, R. W. (1940) Descriptive geology of the Kernville quadrangle,
California : California Jour. Mines and Geology, vol. 36, pp. 343-378.
Rogers, R. G. (1943) Round Mountain oil field, California: in Geologic formations
and economic development of the oil and gas fields of California : California Di-v.
Mines Bull. 118, pt. 3, pp. 579-583.
Stevens, J. B. (1924) Comparative study of the San Joaquin Valley oil fields, Cali-
fornia : Am. Assoc. Petroleum Geologists, Bull., vol. 8, no. 1, p. 33.
Treasher, R. (1949) Geology of Isabella quadrangle, California: (abst.) Geol. Soc.
America, Cord. Sec, Proc, 1949.
Webb, R. W. (1936) Kern Canyon fault, southern Sierra Nevada : Jour. G«ology, vol.
44, pp. 631-638.
Wilhelm, V. H., Saunders, L. W. (1927) Report on Mt. Poso oil field : California Div.
Mines and Mining, Summary of operations, California oil fields, vol. 12, No. 7,
pp. 5-12, pis., map.
printed in California state printing office
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DIVISION OF MINES
OLAF P. JENKINS, CHIEF
STATE OF CALIFORNIA
DEPARTMENT OF NATURAL RESOURCES
BULLETIN 168^
PLATE 3^
N76^E.
EXPLANATION
Qq\ - Alluvium
Or - Terrace
Thr - Kern River growel
Tba - Bene grovel
Tfj - Freemen- Jewett shole
Tiv - llmon ondesile
Tbe - Beolville tonglomerole
Tw - Walker tormoMon
jqd - Biotite quartz diorite
jqdh - B'otile hornblende quortz i
jqn - Biotile hornblende quorl;
jgd - Gobbro dionle
Pd - Pompo schist
IPpg - Greenstone
IPk - Kernville schist
Is - Limestone
GEOLOGIC SECTIONS THROUGH BRECKENRIDGE MOUNTAIN QUADRANGLE, CALIFORNIA
By T W Dibblee Jr 1950
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STAMPED BELOW
AN INITIAL FINE OF 25 CENTS
WILL BE ASSESSED FOR FAILURE TO RETURN
THIS BOOK ON THE DATE DUE. THE PENALTY
WILL INCREASE TO SO CENTS ON THE FOURTH
DAY AND TO $1.00 ON THE SEVENTH DAY
OVERDUE.
AUGl2RQrD
^ 7 19I&
APR 5 19Tli
JAN 6 1988
JAN 1 4 ia
PHYS SCI LIBRARY
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Book Slip-15m-8,'52(A2573s4)458
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