Geology of the Ricardo Beds in the Western portion of Saltdale Quadrangle Kern County

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GEOLOGY OF THE RICARDO BEDS IN THE WESTERN PORTION OF SALTDALE QUADRANGLE KERN COUNTY, CALIFORNIA

A Thesis Presented to the Faculty of the Department of Geology The University of Southern California

In Partial Fulfillment of the Requirements for the Degree Master of Science in Geology

by Ralph M. Barnard June, 1950

UMI Number: EP58430

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T h is thesis, w ritten by

RALPH M. BARNARD under the guidance of h.'.Ls„ F a c u lty C o m m ittee, and app ro ved by a ll its members, has been presented to and accepted by the C o u n cil on G ra d u ate S tudy and Research in p a r t ia l f u l f i l l ­ ment of the requirements f o r the degree of

MASTER OP SCIENCE

D a te .....

F aculty Com m ittee

Chairman / c

’ '

/

* —■—

-^

Iff,

_

d

^

~

TABLE OP CONTENTS CHAPTER I.

II.

PAGE

INTRODUCTION .....................................

1

Location and accessibility of the area • • • •

1

General physiography . . . . . ...........

3

..

Climate and vegetation . . . • • • • • • • • •

ip

Previous work

• • • • • • . . • • • • • • • •

6

Scope of present investigation • • • • • • • .

8

Field work • • • • • • . • • • • • • • • • • •

8

STRATIGRAPHY AND PETROLOGY ......................

10

Basement rocks and younger acidic intrusives • • • • • • • • • • • • • • • • • Pre-Jurassic metamorphic rocks Upper Jurassic igneous rocks

10

• • • • • •

10

• • • • • • •

11

Miocene (?) acidic intrusive rocks

• • • •

12

Rosamond sediments • • • • • • • • • • • . • •

13

Relationships and lithology . . . . . . . .

13

Application of the term, Rosamond . . . . . sediments . • • • • • • • • • • • • • • •

l6

The Ricardo beds • • • • • • • • • • • • • • •

17

General .............

. . . . . . . . . . .

A comparison of three Ricardo sections

• •

17 18

Basal conglomerate andb r e c c i a ............

20

Andesite breccia

........

20

.....................

22

Basalt flows

• • • • • . • •

iii

CHAPTER

III.

PAGE Basalt sills and dikes ....................

26

T u f f s ...................................

26

Arkose, siltstone, and claystone

28

. . . . . .

Upper conglomerates......................

29

Cherts and limestones

32

....................

Black Mountain b a s a l t .......................

314-

Alluvium

35

...................................

STRUCTURE . .................................... Regional structure

..............

37 37

Detailed s t r u c t u r e .........

38

Nature of the Garlock fault in the mapped area

..........

Extent of tilting of the Ricardo

38 beds

Local faults affecting the Ricardo beds IV.

39

. •

39

CENOZOIC H I S T O R Y ..............................

Ip6

Pre-Ricardo e v e n t s ..........................

Ip6

Events of Ricardo t i m e ......................

Ip7

Post-Ricardo e v e n t s ................... V.

...

ECONOMIC ASPECTS

. . . I4.9

..............................

51

P u m i c i t e ...................................

$1

Placer g o l d .................................

52

APPENDIX........................................ BIBLIOGRAPHY

.......................................

56 6l

t

iv LIST OF FIGURES FIGURE 1. 2. 3.

PAGE

Badland topography formed by the erosion of Ricardo strata at the head of Iron Canyon • . • Angular unconformity between the Rosamond sediments and the basal Ricardo conglomerate

15

.........

21

Ip. Looking toward the base of the Ricardo section at Last Chance C a n y o n ..........................

25

5. 6. 7. 8.

Andesite breccia at Last Chance Canyon

.

5

Upper basalt flow capping 75 fset of arkose west of lower Red Rock Canyon ..........

25

View along the strike of the massive pink tuff on the west wall of Iron Canyon . . . . .

30

Alternating beds of red and light grey arkose at Red Rock C a n y o n ............

30

An unusually large calcareous arkose

concretion 9. 10. 11. 12. 13*

lip.

............

Outcrop surface of the conglomerate overlying the pink tuff, west of lower Red Rock Canyon

31 •

33

Repetition of the andesite breccia at the south end of the Last Uiiance Canyon f a u l t ..........

ip1

Repetition of basalt flov/s by the strike fault at f,Red Buttes” ..........................

Ip5

Distortion of the beds at the strike fault shown in Fig. 1 1 ..............................

Ip5

Cudahy Mine, at the pumicite horizon near the middle of the Ricardo sequence; Last Chance C a n y o n ........................................

5ip

Open cut in the pumicite horizon near the middle of the Ricardo sequence • • • • • • • •

55

V LIST OP PLATES PLATE I* II.

PAGE Index Map of Saltdale Quadrangle . . . . . . . . Comparison of Three Sections Through the Ricardo B e d s ..............

III.

2

19

Geologic M a p .............................. (j,a=peekefc) G?'$

CHAPTER I INTRODUCTION I.

LOCATION AND ACCESSIBILITY OF THE AREA

The Ricardo continental sediments and volcanics crop out in eastern Kern County, California, immediately to the east of the Sierra Nevada Range*

The most important exposure

occurs chiefly within the Saltdale Quadrangle, which is de­ fined by Latitudes 35°15*N. and 35°30fN., and Longitudes 117°[j.5 fW. and ll8°00fW*

Tilted Ricardo strata and the as­

sociated older rocks form the western part of the El Paso Mountains* The area described in this study extends from Red Rock Canyon, at the extreme western end of the El Paso Mountains, to the vicinity of Black Mountain, twrelve miles to the north­ east.

This elongated area is parallel to the general strike

of the Ricardo beds*

Plate I shows the exact position of the

area, which includes approximately sixty-five square miles* U.S. Highway 6 passes through Red Rock Canyon, making this portion of the area the most readily accessible.

North

of Red Rock Canyon, several secondary roads branch off from Highway 6 onto the north flank of the El Paso Mountains.

The

south flank of the mountains can be crossed by several secondary roads which branch off from the Randsburg Highway.

PLATE

INDEX

MAP

OF

SALTDALE

QUADRANGLE

X-,:,. :'-X X

.

■ ■'

I N Y8 K E RN

35° 3 0 ‘

Bl oc k Mt .

33 >

rz" o

R i car

i

y

. To Randsbur g

co

ICO lC ICO lO

o Saltdale

Koehn

; Dry Loke «

Qa n t i 4

AfOJAVE DESERT • 5 5 ° l $*

CASTLE

4 TO f

BUTTE

Mohove

113°00'

11 7 ° 4 5 ‘

Approx

AREA

MAPPED

S c a l e : M o . = 4 m lies

IS

SHOWN

IN

YELLOW

The most improved of these follows Last Chance Canyon, A branch of the Southern Pacific Railroad is parallel with the south flank of the SI Faso Mountains and a station is located at Cantil. II. GENERAL PHYSIOGRAPHY The physiographic and structural features of Saltdale Quadrangle are typical of the Basin and Range Province.

The

northeast-trending El Paso range is a tilted fault block; described by Baker^ as lying en echelon with the southern Sierra Nevada Range.

The Garlock fault scarp forms the

steep south flank of the El Paso Mountains, rises abruptly above

This scarp

a basin containing Koehn Dry Lake.

The

north flank of the El Paso Mountains has a relatively gentle slope, except at Black Mountain.

The piedmont alluvial

slope of the Sierra Nevada Range extends to the foot of the north flank of the El Paso Mountains in the area studied. Black Mountain, with

an elevation of 5*259 feet, is

the highest point in the El Paso Mountains and in Saltdale Quadrangle.

The lowest point in the quadrangle is at Koehn

C. L. Baker, "Physiography and Structure of the Western El Paso Range and the Southern Sierra Nevada", Univ. Calif• Pubs., Bull Dept. Geology, vol. 7* p. 119* 1912.

Dry Lake, which has an elevation of slightly less than 1,950 feet. Within the area studied, the El Paso Mountains are dissected by Red Rock Canyon, Iron Canyon^, and Last Chance Canyon.

Badland topography is present where the tributaries

to

these canyons have incised the Ricardo beds.

A portion

of

the Sierra Nevada piedmont alluvial slope isdrained by

the western and northern tributaries of Red Rock Canyon. III.

CLIMATE AND VEGETATION

The area is located at the northwest corner

of the

Mojave Desert proper, hense the climate and vegetation are those of extreme aridity.

Although the annual precipitation

is ordinarily less than five inches, cloudbursts have been known to destroy roads and buildings located in or close to the drainage courses of Red Rock Canyon.

The summers are

long and hot, with daytime temperatures of 100° to 112° F. being common from June through September.

The most ideal

daytime temperatures for field work occur from November to April.

Below freezing nighttime temperatures can be ex­

pected during the winter months, and light snow flurries

3 Not to be mistaken with another Iron Canyon lo­ cated approximately 12 miles to the east in the El Paso Mountains.

5

Figure 1 Badland topography formed by the erosion of Ricardo strata at the head of Iron Canyon.

occasionally occur in the El Paso Mountains during this season.

The strong winds typical of high desert regions are

frequent in the area, especially in the spring and fall. The scanty vegetation includes such types as the creosote bush, desert trumpet, and desert holly.

Small

groves of yucca trees (joshua) are present in many of the alluvial covered localities. IV. PREVIOUS WORK The majority of reports pertaining to this area have been concerned with the Ricardo fossil assemblage. logical investigation has been very incomplete.

Geo­

The strati-

graphic sequence has been described only in the immediate vicinity of Red Rock Canyon.

None of the reports includes

a geologic map of the area. The stratigraphic sequence at Red Rock Canyon was first described by G i l b e r t ^ in 1875. strata as the ’’Red Rock Canyon beds”.

He referred to the Fairbanks^- in an­

other early paper, briefly discussed the ’’Red Rock Canyon

G. K. Gilbert, ’’Report on the Geology of Portions of Nevada, Utah, California, and Arizona”, Geographical and Geological Explor, and Surveys West of the 100th Meridian, vol. 3, pp.“ 152-111.3 , 1875* H. W. Fairbanks, ’’Notes on the Geology of Eastern California”, American Geologist, vol. 17, pp. 07-69, 189^4--

7 beds" and the Black Mountain area to the northeast.

A

report by Baker^ contained a physiographic study of the western El Paso Mountains and a discussion of the Ricardo beds.

The Ricardo beds were referred to in this report as

the Upper Miocene Rosamond 11series11.

The name R i c a r d o ^ was

7 first applied to the beds at Red Rock Canyon by Merriam', following the discovery that the fossil fauna included o horses with Lower Pliocene characteristics. Hulin has noted the presence of a basal Ricardo conglomerate, and has stated that the Ricardo "series" can be found in widely scattered areas throughout the Searles Lake Quadrangle. A number of papers which deal with the Ricardo fossil assemblage are reviewed in the appendix of this report.

C. L. Baker, "Physiography and Structure of the Western El Paso Range and the Southern Sierra Nevada", Univ. Calif. Pubs., Bull. Dept. Geology, vol. 7> PP* 117-1^1-2 , 1912. L ° Ricardo is the name of a very small group of buildings in upper Red Rock Canyon, near some of the best fossil localities. ^ J. C. Merriam, "Tertiary Mammalian Faunas of the Mojave Desert", Univ. Calif. Pubs., Bull. Dept. Geology, vol. 11, pp. —I4J4.3"9 1919» ® C. D. Hulin, "Geologic Features of the Dry Placers of the Northern Mojave Desert", Calif. Jour. Mines Sc Geology, vol. 30, p. Il20, 193^-*

8 V.

SCOPE OF THE PRESENT INVESTIGATION

A detailed geologic map was made of the Ricardo sedi­ ments and volcanics that are exposed from Red Rock Canyon to the vicinity of Black Mountain,

From this map and the ad­

ditional field observations made during its preparation, written or graphic conclusions are presented regarding the following principal problems: (1) The nature and extent of important lithologic units and the amount of variation between the stratigraphic sequence at Red Rock Canyon and previously undescribed sequences to the northeast, (2) The vertical extent of what can be called the Ricardo beds, and the presence or absence of older Tertiary strata in the area. (3) The nature and extent of faulting within the Ricardo beds. (Ip) The history of the area from Miocene to Recent time • VI.

FIELD WORK

A total of approximately sixty days were spent in the field during the summer and fall of 19^4-9 *

mapping was

carried out with the aid of enlarged United States Army topo-

graphic sheets and a number of aerial photographs.

The

field work was supplemented with a small amount of labo­ ratory study. Dr. Thomas Clements has visited the area with the writer, and has offered a number of valuable suggestions. Mr. Wally Becktel of Red Rock Lodge supplied helpful infor­ mation pertaining to the local geography.

CHAPTER II STRATIGRAPHY AND PETROLOGY I.

BASEMENT ROCKS AND YOUNGER ACIDIC INTRUSIVES The metamorphic and igneous basement rocks that

underlie the Tertiary sediments of the area, are exposed along the high south flank of the El Paso Mountains* It was not the purpose of this investigation to enter into a de­ tailed study of these rocks, which present a sizable petrographic problem In themselves.

They are therefore shown,

along with the younger rocks that intrude them, as a single unit on the geologic map. Pre-Jurassic metamorphic rocks*

A large outcrop of

pebbly quartzite occurs northeast of lower Red Rock Canyon and southeast of Iron Canyon.

In this same area several

small remnants of schist were observed. Kulin^ has described a thick series of moderately metamorphosed sediments in the eastern El Paso Mountains. He believes these rocks to be of Paleozoic age and to probably represent several geologic Periods.

The pebbly

-*■ Carlton D. Hulin, "Geology and Ore Deposits of the Randsburg Quadrangle of California , Calif. State Mining Bu. Bull. 95, p p * 31-33, 1925*

11 quartzite near Red Rock and Iron canyons may also be of Paleozoic age, inasmuch as the rocks described by Hulin occur in a nearby area, and resemble the pebbly quartzite in their degree of metamorphism.

The small remnants of schist

in the area of this investigation may be either Paleozoic or pre-Cambrian in age. by Hulin

p

A large amount of schist, considered

to be of Archean age, is exposed in the Rand

Mountains of the adjacent Randsburg Quadrangle. Upper Jurassic igneous rocks.

The basement consists

of granitic rock in the Last Chance Canyon area.

Where

lower Lost Chance Canyon cuts through the south flank of the El Paso Mountains, much of the rock is similar megascopically to typical samples of the Atolia quartz monzonite, which were examined by the writer at a mine dump near Atolia in the Randsburg Quadrangle.

The Atolia quartz-

monzonite was described by Hulin^, as underlying the greater part of the Randsburg Quadrangle and intruding the Paleozoic sediments of the eastern El Paso Mountains. The coarser grained igneous rocks between Last Chance Canyon and Red Rock Canyon, range in composition from

2

C. Hulin, op. cit. pp. 21-31*

3 C. Hulin, op. cit. pp. 33-lp2.

12 granite to a rock identified by Baker^ as hornblende diorite. There can be little doubt that the batholithic rocks of the western El Paso Mountains belong to the same late Jurassic igneous invasion as do the rocks of the Sierra Nevada to the west and the Atolia quartz monzonite to the east. Miocene (?) acidic intrusive rocks.

West of lower

Red Rock Canyon, the Ricardo beds are unconformably under­ lain by a large body of rhyolite containing rounded phenocrysts of cniartz*

The main body lies on top of the basement

rocks but the rhyolite has the appearance of an intrusive rock rather than a surface flow.

The rhyolite may have been

intruded as a sill or laccolith into rocks that were removed by erosion in pre-Ricardo time.

Several smaller masses of

similar rock were observed underlying the Ricardo beds and associated with the basement rocks in Iron Canyon.

Acidic

dikes intrude both the metamorphic and igneous basement rocks between Red Rock and Last Chance canyons. In the adjacent Randsburg Quadrangle, Hulin^ has

C. L. Baker, "Physiography and Structure of the Western El Paso Range and the Southern Sierra Nevada", Univ. Calif. Pubs., Bull. Dept. Geology, vol. 7, pp. 121-122, 1912. ^ C. Hulin, op. cit., pp. ip8-52.

reported a group of rhyolite and latite pipes, dikes, and sills which are known to be intruded into the lower portion of the Upper Miocene Rosamond series of that area.

Detrital

fragments of the same intrusives are found higher in the Rosamond beds.

The rhyolite was not observed to intrude the

Rosamond sediments in the area of the present investigation. However, the Rosamond sediments of the area were extensively eroded in pre-Ricardo time.

Rhyolite bodies such as the one

on the west side of lower Red Rock Canyon, may have intruded Miocene sediments that were later removed by erosion.

If

such was the case, the intrusives are of the same age as those in the near-by Randsburg Quadrangle. II.

ROSAMOND SEDIMENTS

Relationships and lithology.

Pre-Ricardo arkosic

deposits, designated in this report as Rosamond sediments, unconformably overlie the basement rocks in the vicinity of Last Chance Canyon.

A distinct angular unconformity sepa­

rates these deposits from the overlying Ricardo beds.

The

Rosamond sediments occur in two areas which are separated from each other by a spur of granitic basement rock. The relationships between the Rosamond sediments and the Ricardo beds, are best observed at the smaller and southernmost

of the two separated areas.

Here the over-

lying Ricardo beds strike north 25° east and dip 15° to 20°

to the northwest, whereas the Rosamond strata strike ap­ proximately north 6o° east and dip I4.O0 to the northwest* The unconformable contact is visible at a number of locali­ ties, the clearest of which is shown in Figure 2.

The

maximum thickness of the Rosamond strata in this area, calculated on the basis of a I4-O0 dip, is in excess of 2$00 f eet. The larger and more northerly area in which Rosamond sediments are exposed is located between upper Last Chance Canyon and Black Mountain.

Here the beds continue to crop

out to the east of the area mapped, and extend into the large basin between Black Mountain and the main El Paso range*

The exact contact between the Rosamond and Ricardo

strata is rather obscure due to poor exposure in this area* However, the contact can be roughly traced by noting the occurrence of rounded boulders and cobbles which have been eroded from the basal Ricardo conglomerate*

Good exposures

of Rosamond strata occur on the east side of Bonanza Gulch, a tributary to upper Last Chance Canyon*

The Rosamond

sediments were examined only as far to the east as Bonanza Gulch.

The strike and dip of the beds near the mouth of

Bonanza Gulch are approximately the same as those previously noted for the southern Rosamond exposure. The Rosamond sediments that were mapped in this in­ vestigation consist chiefly of dark red and yellowish brown

15

Figure 2 Angular unconformity between the Rosamond sediments and the basal Ricardo conglomerate. The Rosamond here consists of alternating arkosic and shaly beds.

16 arkose.

No interbedded volcanic flows or tuffs are present.

Mica is abundant in much of the arkose of both areas.

In

the southern area, immediately below the contact with the basal Ricardo, beds of Rosamond arkose alternate with thin, micaceous, shaly beds, (See Figure 2.)*

In the same area,

some of the lower Rosamond arkose contains fragments of the underlying basement rock. Application of the term, Rosamond sediments.

The

name Rosamond "series” was first applied by Hershey^ to the continental sediments and volcanics exposed near the town of Rosamond, twelve miles south of Mohave.

These deposits,

along with the fossiliferous beds of the Barstow syncline in the central Mojave Desert, were later classified as Upper Miocene^.

The name Rosamond has since been widely applied to

lithologically similar Mojave Desert deposits which are generally thought to be Middle or Upper Miocene in age, but which have not been given local formation names.

The name

seems especially appropriate for the sediments being con­ sidered here, inasmuch as they are unc-onformably overlain by

° Oscar Hershey, "Some Tertiary Formations of Southern California", American Geologist, vol. 29, PP* 365-370, 1902. ' C. L. Baker, "Notes on the Later Cenozoic History of the Mojave Desert Region", Univ. Calif. Rubs., Bull., Dept. Geology, vol. 6, pp. 333-383, 191i*

17 the beds containing the Lower Pliocene Ricardo fauna, and are lithologically similar to some of the Rosamond sediments in other areas. do fossils were found in the Rosamond sediments in the area mapped. III. General.

THE RICARDO BEDS

The strata here included in the Lower Plio­

cene Ricardo beds consist of an estimated 3>700 to i(.,5>00 feet of continental sediments and volcanics.

The upper

limits of the Ricardo beds are rather poorly defined

be­

cause the upper strata are overlapped by Sierra Nevada al­ luvial slope deposits.

However, the thicknesses mentioned

above are considered as maximum. The Ricardo succession has been variously designated as the Ricardo formation, beds, or 11series".

Series (with

a capital S) is the rock equivalent of an entire geologic Epoch.

The designation Ricardo "series11 is therefore con­

sidered undesirable.

The designation Ricardo beds is used

in preference to Ricardo formation in this report

because

there are a number of distinct lithologic units present. The paleontology of the Ricardo beds is reviewed in the Appendix.

18 A comparison of three Ricardo sections*

Sections at

Red Rock Canyon, Iron Canyon, and Last Chance Canyon, are compared in Plate II, which follows this page.

The upper­

most basalt flow has been used as the datum horizon because it is present in all three sections and was apparently ex­ truded upon a fairly level surface*

WEST OF LOWER RED ROCK CANYON

HEAD OF IRON CANYON

a rk o s e , s ilts to n e , and claystone* occasionally tu ffa c e o u s ’

ark o s e , s ilts to n e , and claystane: occasionally tu ffa c e o u s .

2500’?

2 5 0 0 '?

a rk o s e , s ilts to n e , c la y s to n e , tu ff, c h e rt, and lim e s to n e .

2500' ?

b a s a lt f lo w 4 0

b a s a lt flow 25'+a rk o s e

LAST CHANCE CANYON

75'

ark o s e 1 0 0 '

b a s a lt fla w 2 5 ’

b a s a lt flo w 2 5 '

100'

b a s a lt flaw s 10'and 20', sep arate d by 1 5 'o f arkose, c h e rt,a n d I.s .

a rk a s e , w ith cob ble-bo ulder co n g lo m erate in low er p a r t

a r k o s e and minor amount of t u ff

600'

700'

basalt flow 2 0 ' arkose,chert,and I.s.

a rk o s e , c h e rt, and tu ff

p in k t u f f 100

800'

a lte rn a tin g beds o f re d a n d g ro y a rk o s e

p in k t u f f 1 0 0 '

red and g ray a rk o s e

4 0 0 '— b a s a l b re c c ia

co b b le conglomerate

500’ in tr u s iv e r h y o lite

5 0 0 '+ a n d e s ite b re c c ia 5 0 ' -

tuff 100'

a c id ic b a s a lt flow

b a s o l c o n g lo m e r a te

tuff 200' granodiorite

a n d e s ite b re c c ia 7 0 ' tu ff 2 0 0 ' b a s a l c o n g lo m e ra te 15'

Rosam ond a rk o s e

PLATE II COMPARISON

OF THREE S E C T IO N S 2 5 0 0 '+

THROUGH THE RICARDO BEDS D IS T A N C E

B E TW EE N O U T S ID E

5 ? M IL E S M E A S U R E D BA S A LT F L O W . CO LO RS S I M IL A R G EO LO G IC MAP. T H IC K N E S S E S

ARE

TO

C O LU M N S

IS A P P R O X IM A T E L Y

ALONG TH E S T R IK E

OF THE

UPPER g r a n o d io rite

THOSE

USED ON

A P P R O X IM A T E

A C C O M P A N Y IN G

20 Basal conglomerate and basal breccia.

The lowest

Ricardo bed, where the Ricardo lies unconformably upon the Rosamond sediments, is a conglomerate containing wellrounded boulders, cobbles, and pebbles.

This conglomerate

is also present at several locations between Iron and Last Chance canyons where the Ricardo lies directly upon the basement rocks.

However, there is a definite tendency for

the conglomerate to be absent or very thin where the Rosamond sediments are absent, as such localities were topo­ graphically high in early Ricardo time. The clasts are composed chiefly of quartzite, granite, and granodiorite.

Polished quartzite clasts of a

variety of colors are abundant.

The clasts are enclosed by

a poorly consolidated arkosic matrix. The lowest Ricardo bed west of lower Red Rock Canyon, is a breccia composed of fragments of the underlying in­ trusive rhyolite (quartz porphyry).

The breccia is only a

few feet thick and grades upward into typical Ricardo arkose. Andesite breccia.

A thick bed of dark red volcanic

breccia occurs between massive tuffs, near the base of the Ricardo section.

It is exposed from upper Iron Canyon to

the vicinity of Black Mountain.

The breccia is formed of a

jumble of unsorted, unoriented, fragments, ranging from less than an inch to over a foot in diameter,

The fragments are

21

Figure 3 Andesite breccia at Last Chance Canyon.

22

held together by small quantities of siliceous cement* Quartz crystals and incrusting layers of opal and chalcedony often fill or line fractures and other openings in the breccia.

Some of the fragments consist wholly of dark red,

purplish-red, brown, or dark brown rock, containing small phenocrysts of plagioclase in a fine grained groundmass. However, a large number of the fragments are composed of yet smaller fragments of the above described rock in a matrix of dense, pinkish-red, andesitic tuff. Several sample fragments, varying somewhat in color, were powdered and examined by the oil immersion method. Two samples contained andesine, but the plagioclase in a third sample was labradorite.

It is possible that with a

more thorough petrographic study, the material could be called an andesite-basalt breccia., The possibility of two generations of plagioclase of different composition was not investigated.

A large amount of secondary hematite is re­

sponsible for the red to brown color of the rock. Basalt flows.

A basaltic flow occurs approximately

200 feet above the andesite breccia in Last Chance Canyon and in the area to the north.

Erosion occurring in both

Ricardo and quaternary time have reduced the extent of this flow.

In Last Chance Canyon, a large portion of the flow

has been replaced down the dip by a thick conglomerate

which is also of Ricardo age*

The flow occurs in discon­

tinuous outcrops along the strike, due at least in part to Quaternary erosion.

The color of the rock ranges through

reddish-brown, dark brown, dark green, and grey. portion of the flow is very vesicular.

The upper

Small phenocrysts

of plagioclase are visible in a fine-grained groundmass. In Last Chance Canyon, near the southern end of the flow, the rock is megascopically similar to some of the fragments composing the underlying andesite breccia.

However, the

flow is more basic in appearance to the north.

A micro­

scopic examination of two samples from Last Chance Canyon showed the plagioclase to be labradorite.

The megascopic

appearance of some portions of the flow and the rather sodic labradorite in the samples examined,

suggest

that

the flow as a whole is only slightly more basic than the fragments composing the andesite breccia.

The southern end

of the flow has been tentatively designated as acidic ba­ salt in ilate II and Figure 5 , to differentiate it from the darker colored basalt flows occurring higher in the section. Two basalt flows extend from Red Rock Canyon to Last Chance Canyon, a distance of slightly less than seven miles, measured along the strike.

The flows are located strati-

graphically near the middle of the Ricardo sequence. flows vary from ten to fifty feet in thickness and are

The

separated from each other by approximately one hundred feet of arkose and associated sediments.

The stratigraphic po­

sition of the lower flow is occupied by arkose at two lo­ calities in Red Rock Canyon.

At both localities the basalt

is again present farther along the strike.

Evidently the

lower flow was cut by a stream system before the upper flow was extruded. A third basalt flow is present near the north end of o the locality designated as "Red Buttes", in the vicinity of Last Chance Canyon.

This flow is separated from the lower

of the two main flows by fewer than twenty feet of sediments (See Plate II).

The flow lies stratigraphically too close

to the main lower flow to be clearly diown on the geological map (Plate III). The tops of the flows are very vesicular and. contain amygdules of opal, chalcedony, and quartz.

Crude columnar

jointing was observed at several localities.

Fresh un­

weathered surfaces of the basalt are dark grey, dark green, or black.

Several samples from the flows in the Red Buttes

area, were examined by the oil immersion method. plagioclase in these samples was labradorite.

This name appears on the sheet, but may be in error. High formed by the andesite breccia on Canyon opposite to the designated

The

Olivine was

Saltdale topographic ridges of a red color are the side of Last Chance area.

Figure ip — Looking toward the base of the Kicardo section at Last Chance Canyon* 1-andesite breccia; 2-acidic basalt flow; 3-two basalt flows separated by less than 20 feet of sediments; Ip-upper basalt flow; 5>-upthrown repetition of upper basalt flow.

Figure 5 — Upper basalt flow capping 75 feet of arkose west of lower Red Rock Canyon* we***

present in the samples, but not in abundance. Basalt sills and dikes.

Two basaltic intrusives were

mapped in the Last Chance Canyon area.

Both intrusions oc­

cur partly in the form of a dike and partly in the form of a sill.

The larger of the two bodies intrudes the Rosamond

sediments and the basal Ricardo beds.

The main body of the

intrusion consists of basalt and diabase containing sodic labradorite as the feldspar.

Several small dikes extend

upward from the main body to the base of the andesite breccia.

Here the material from the dikes has spread out

into a vesicular and amygdaloidal mass that is highly sug­ gestive of a flow.

If this vesicular mass is actually a

flow rather than a sill, the basaltic intrusion occurred slightly prior to the deposition of the andesite breccia. The smaller intrusive body occurs immediately north of the ninety degree southward turn in the course of upper Last Chance Canyon.

This body is also intruded into the

beds below the andesite breccia.

However a narrow offshoot

dike was traced completely through the andesite breccia to the base of the overlying flow of basalt. Tuffs.

The lower half of the Ricardo beds includes

extensive deposits of light colored tuffs.

Less pure tuff­

aceous deposits grading from arkosic tuff to tuffaceous

27 arkose, are present In both the lower and the upper portions of the Ricardo beds. are also present.

Tuffaceous siltstones and claystones

In the Last Chance Canyon area and the

area to the north, the andesite breccia is both underlain and overlain by thick massive beds of pink, white, and cream colored tuffs composed of both lithic and vitric material of acidic to intermediate composition.

These tuffs include

scattered fragments of andesitic (?) rock of granule and pebble size.

The deposits can therefore be called lithic

tuff breccias, although the amount of fine light colored matrix is very great relative to the included dark colored fragments.

A similar massive tuff or tuff breccia is

present approximately 600 to 700 feet below the two basalt flows in Red Rock and Iron canyons.

This tuff is of a light

pink hue and extends along the strike for three and a half miles, with unusual uniformity of thickness and composition (Figure 6). Fine, light grey to white, vitric tuffs are present in Last Chance Canyon and adjacent areas to the north and south. planes.

These tuffs are well sorted and often show bedding The largest and most pure (vitric) deposits are

mined as commercial pumicite, and are further discussed in Chapter V.

28 Arkose, siltstone, and claystone.

A large amount of

the sediments in the Ricardo beds consists of coarse to fine arkose*

Both orthoclase and plagioc]ase are present in the

arkose in large quantities*

Angular to sub-angular granite

and granodiorite rock fragments are also present*

The

feldspar grains are usually fresh-appearing and angular. Grains of biotite are common, and also present a fresh ap­ pearance*

Much of the material was obviously derived from

the coarse grained acidic igneous rocks of a nearby area* However, a small to large admixture of tuff and volcanic rock fragments is usually present in the beds. Typically there is a wide range of grain size within the arkose.

Any one small sample will usually contain a

scattering of fragments of granule and pebble size, as well as interstitial silt and clay. in lenses. calities.

Coarser material also occurs

Cross-bedding was observed at a number of lo­ Unusually well bedded arkosic sediments were ob­

served near the middle of the Ricardo beds in the Last Chance Canyon area.

Such beds, however, are not extensive.

Most of the arkose is weakly consolidated.

Some of

the beds in the middle and upper portions of the Ricardo contain interstitial calcium carbonate.

Beds of arkose,

colored a bright red hue due to the presence of hematitic material, are present below the pink tuff in Red Rock

29 and Iron canyons (Figure J )• Calcareous arkose concretions in a matrix of noncalcareous arkose, were found at several horizons above the upper basalt flow in the vicinity of Red Rock Canyon*

The

concretions have no visible nuceli and differ from the en­ closing beds only in containing approximately twenty percent by weight of interstitial calcium carbonate*

Bedding planes

pass uninterrupted from the enclosing beds through the con­ cretions.

The concretion are therefore epigenetic in origin

and were probably formed by the precipitation of calcium carbonate from meteoric waters.

Centers of precipitation

may have developed around initial grains of calcium carbon­ ate in a manner similar to that described by Tarr^. Extensive deposits of poorly consolidated siltstone and claystone are associated with the arkose in the upper one-half of the Ricardo beds* absent in these deposits.

Shaly parting planes are

Sand-sized grains of feldspar

and quartz a^e disseminated through some of the beds of fine material.

Some of the siltstones and claystones are

tuffaceous* Upper conglomerates.

A thick poorly consolidated

conglomerate is present approximately 200 to 700 feet above

W. A. Tarr, "Concretions in the Champlain Formation of the Connecticut River Valley", Geol. Soc. America, vol. k.6 , pp. 1519-1552, 1935'.

Figure 6 — View along the strike of the massive pink tuff (T) on the west wall of Iron Canyon. The tuff is roughly 100 feet thick and is under lain by beds of arkose (A)*

T if’& A *" '

Figure 7 — Alternating beds of red and light grey arkose at Red Rock Canyon. A portion of the overlying massive pink tuff can be seen at the top.

Figure 8 An unusually large calcareous arkose concretion eroded from beds of noncalcareous arkose northeast of Ricardo. The bedding planes have been accentuated by weathering.

the andesite breccia in Last Chance Canyon*

The strati-

graphic position of a basaltic flow and some of the tuff underlying it is occupied down the dip by the lowest part of this conglomerate (See Section C-D, Plate III).

The

conglomerate consists chiefly of rounded to sub-rounded cobbles and pebbles of volcanic rocks in a matrix of sand, silt, and clay.

The most abundant clasts are grey and

purplish-red cobbles, probably of andesitic composition. Faint bedding planes are visible. A somewhat similar but less extensive zone of con­ glomerate crops out above the pink tuff west of lower Red Rock Canyon,

(Figure £).

Cobbles and boulders of both ex­

trusive and intrusive rocks are enclosed in a matrix of coarse brown arkose.

The conglomerate grades upward into

the arkose underlying the basalt flows. Cherts and limestones.

Thick beds of chert occur

both above and between the basalt flows near the middle of the Ricardo section in Last Chance Canyon.

Beds of chert

are also abundant in the middle and upper exposures of Ricardo strata between the northern termination of the ba­ salt flows and the northern end of the area.

The beds are

light grey to milky vhite in color and contain irregular masses of brown and grey, transparent to translucent, chal cedony.

The cherts have protected the less resistant

33

Figure 9 Outcrop surface of the conglomerate overlying the pink tuff west of lower Red Rock Canyon*

3k associated sediments from erosion, Causing the formation of high steep cliffs on the northwest side of Last Chance Canyon. Beds of light grey to chalky white, often vesicular rock are associated with the cherts in the Last Chance Canyon area.

These rocks contain an adequate percentage of

calcium carbonate to be called limestones.

Four samples

were treated with dilute hydrochloric acid and the values obtained ranged from 60% to 90% calcium carbonate by weight. The undissolved material consisted of silt and clay. IV. BLACK MOUNTAIN BASALT The lower Ricardo beds and underlying Rosamond sedi­ ments pass unconformably beneath a basalt flow at the north­ east end of the area mapped in this investigation.

Black

Mountain has been formed at least in part by the protective effect of this basalt, which has prevented the underlying Ricardo beds from being attacted by erosion. B a k e r^

observed that the Black Mountain basalt was

extruded upon an old erosion surface of beveled Ricardo strata.

In the vicinity of the Coso Range, thirty miles to

9

C. L. Baker, "Physiography and Structure of the Western El Paso Range and the Southern Sierra Nevada", Univ. Calif. Pubs., Bull. Dept. Geology, vol. 7* PP* 126-128, 1912.

35 the north, H o p p e r h a s

described thin flows of basalt which

also overlie an old erosion surface.

The same flows lie

without angular discordance upon the Goso formation, which contains fossil vertebrates believed to be of late Pliocene or more probably early Pleistocene age.

The old Ricardo

erosion surface is probably correlative with the old erosion surface in the Goso Mountains area.

It follows then, that

the most probable age of the Black Mountain basalt is early Pleistocene. The writer has mapped only the southwestern edge of the Black Mountain basalt, and no new information of im­ portance was obtained regarding this formation.

The basalt,

where mapped, is underlain by the thick massive tuff de­ posits of the lower Ricardo beds. V.

ALLUVIUM

The area contains Recent alluvium and old alluvial terrace deposits which are considered to be Pleistocene in age • The Sierra Nevada piedmont alluvial slope overlaps the eroded surface of the upper Ricardo beds (See Section -E-F, Plate III).

The Ricardo beds and the overlying Sierra

*1

Richard H. Hopper, "Geologic Section From the Sierra Nevada to Death Valley, California", Geol. Soc. Amer., Bull, vol. , pp. 393-^32, 19k7•

36 Nevada alluvium have been extensively dissected in the vicinity of Red Rock Canyon.

The alluvium has been left as

terrace deposits on the tops of cliffs and high ridges of Ricardo strata.

At many localities the old erosion surface

developed on the tilted Ricardo strata is clearly visible beneath the alluvium.

Baker11 has called the surface

beneath the alluvium, the “Ricardo erosion surface” and has correlated it with the erosion surface underlying the Black Mountain basalt and with old erosion surfaces found at the summit of the Sierra Nevada Range. Old alluvium has also been left as terrace deposits in the Iron Canyon and Last Chance Canyon areas.

In some

localities, eroded Ricardo strata are capped by a thin layer of partly consolidated gravel or conglomerate con­ sisting of fragments of local rocks. Recent dissection of the Sierra Nevada alluvial slope and some of the underlying Ricardo beds has resulted in the deposition of late alluvium in the Red Rock Canyon drainage system.

Recent erosion of the El Paso Mountains has caused

late alluvial deposits to be formed in all of the drainage systems in the area.

In some localities the Recent alluvial

deposits are themselves undergoing dissection.

11 C. Baker, op. cit., pp. 137-139.

CHAPTER III STRUCTURE I. REGIONAL STRUCTURE Typical basin and range structure is evident in Saltdale Quadrangle and the surrounding region.

The El Paso

range is a tilted fault block, uplifted along its south flank at the Garlock fault.

The relationship of the Garlock

fault to the major physiographic features of Saltdale Quadrangle is shown in Plate I, page 3*

Hulin-1- found evi­

dence of both vertical and horizontal movement of the Garlock fault in the adjacent Randsburg Quadrangle.

He sug­

gests that the fault may have been a line of weakness since the Jurassic igneous invasion, although he found much evi­ dence that the chief movements have occurred in the Qua­ ternary.

In the alluvium immediately south of the El Paso

scarp, Hulin further noted the occurrance of truncated spurs, furrow-like depressions, and other evidence which indicate some movement in Recent time. A large portion of the exposed Ricardo beds dip to the northwest, and are included in the tilted fault block

Carlton D. Hulin, "Geology and Ore Deposits of the Randsburg Quadrangle of California", Calif. State Mining Bu., Bull. p p * 62-6ip, 19 r £*

38 which has formed the El Paso Mountains*

The general strike

of the Ricardo beds is slightly north of the trend of the main El Paso range and the Garlock fault* II.

DETAILED STRUCTURE

Nature of the Garlock fault in the mapped area.

It

will be seen from Plate _I and Plate III that the Garlock fault crosses only the southernmost corner of the area mapped in the present study.

At this locality it consists

of at least two branches along which vertical displacements have occurred.

On the north side of the northern branch,

the basement rocks and the overlying Ricardo beds have been uplifted to form the extreme western end of the El Paso Mountains (See section E-F, Plate III).

A much smaller

amount of vertical displacement has occurred along the southern branch of the Garlock fault, where only the upper portion of the Ricardo beds has been brought to the surface. The northern branch of the fault was carefully ex­ amined in a gulley one half mile east of the mouth of Red Rock Canyon, where the basement rock on the upthrown side is in contact with upper Ricardo strata and alluvium on the downthrown side.

The fault plane is visible on the steep

sides of the gully as a zone of brecciation.

The vertical

attitude of this zone of brecciation clearly indicates that

39 the fault plane is vertical.

Immediately south of the fault

line at this same location, the alluvial slope is under­ going dissection,

suggesting Recent uplift along the fault.

Extent of tilting of the Ricardo beds.

Between Red

Rock Canyon and the vicinity of Black Mountain, the north­ west dip of the Ric-rdo beds ranges from more than 25° in some of the lower beds to less than 10° in the upper beds. Section E-F of H a t e

IIITbest illustrates how the effect of

uplift initiating at the Garlock fault is gradually lost in the upper Ricardo beds. Local faults affecting the Ricardo beds.

The lower

and middle portions of the Ricardo sequence have been dis­ placed along several large normal strike faults (See Sections A-B and C-D of Plate III).

Strike faults at Red Rock

Canyon are of minor importance, but in Last Chance Canyon and adjacent areas, displacements have had a large effect upon the local topography and the apparent thickness of the str atigraphic section.

The strike faults are usually termi­

nated at both ends through a gradual decrease in displace­ ment, but several were observed to be complemented at one end by a transverse or oblique fault. The largest normal strike fault in the area, desig­ nated here as the Last Chance Canyon fault, cuts a portion

of the andesite breccia in Last Chance Canyon, and can be traced northward to the vicinity of Black Mountain*

The

fault has a dip of approximately 30° east, at a locality just north of where the fault crosses the course of Last Chance Canyon.

The apparent maximum displacement of the

Last Chance Canyon fault is approximately 1300 feet.

For

over a mile this displacement causes a complete repetition of the andesite breccia, the overlying basalt flow, and a considerable thickness of sediments associated with these two extrusives.

On the ridge north of Last Chance Canyon,

the fault can be accurately traced along a narrow zone in which the strata have been reversed in dip.

hear the Holly

pumicite mine the andesite breccia on the downthrown side of the Last Chance Canyon fault is again repeated by a smaller strike fault. In the area between Last Chance Canyon and the head of Iron Canyon, a system of oblique and strike faults has caused the beds to the west and southwest to be upthrown relative to the beds to east and northeast.

A part of this

displacement occurs at the head of Iron Canyon, along a high angle strike fault which has caused a repetition of the andesite breccia and some of the arkose overlying it.

Above

the head of Iron Canyon, a large amount of vertical dis­ placement has taken place along an oblique fault, which at

— - - ^-i- *

■

a - . jaa a*—

-:-

- i f in n r

I

Figure 10 Repetition of the andesite breccia at the south end of the Last Chance Canyon fault. Upthrown portion occurs in the foreground.

one locality was observed to have a dip of approximately 30° to the northeast•

The fault has displaced pink and white

tuff members at least 650 feet vertically*

Ln echelon with

this oblique fault are a series of three miniature, step­ like, fault scarps in the lower outcrop of basalt at the southwest end of the area designated as Red Buttes

on the

map* Completing the over-all displacement of strata in the area between Iron Canyon and Last Chance Canyon, is a normal strike fault running the length of “Red Buttes'*. The maximum displacement of this fault occurs near the north end of “Red Buttes”, and has caused the complete repetition of three basalt flows-^*

These basalt flows are designated

here in the ascending order as flows 1, 2, and 3*

On the

downthrown side of the fault, the three basalt flows are well exposed, with flows 1 and 2 being separated from each other by less than twenty feet of sediments.

However, on

the upthrown side of the fault, flow 1 is at first not ap­ parent, and 2 and 3 appear to be thinner than do those on the downthrown side.

These apparent dissimilarities can be

explained by the poorer exposure of the upthrown outcrops,

See page 2k, footnote 8. ^ The lower two flows lie stratigraphically too close to each other to be shown separately on the geologic map (except at one small locality). The lowest flow is not visible in Figure 11 due to poor exposure.

U3 for a careful search revealed a small gully in which flow 1 is visible at the expected distance below flow 2.

A more

direct indication of strike faulting was found in a gully where the beds are greatly distorted next to the upthrown basalt,

(Figure 12). Several strike faults of minor displacement cut the

massive pink tuff in Red Rock and Iron canyons*

In the Last

Chance Canyon area, a number of minor displacements were ob­ served in the andesite breccia, the acidic basalt flow, and the tuffs associated with these extrusives. Some of the faults described may have originated sometime during the iliocene when the Ricardo beds were first tilted to the northwest.

However, a large amount of

displacement undoubtedly occurred during the Quaternary up­ lift of the El Paso Mountains, when the lower and middle portions of the Ricardo beds underwent further tilting. At Last Chance Canyon, the slope forming the eastern flank of "Red Buttes" is locally dissected along a strike fault of minor displacement.

The undissected surface of the

slope consists of debris from the overlying basalt flows. In view of the large amount of erosion which has taken place in the area during the late Quaternary, it seems unlikely that this nearly intact slope was formed before Recent time. Recent movement of the fault is suggested by the fact that

kb

the smooth profile of the slope is interrupted at the fault but is again present beyond the fault*

■rrn

Figure 11— Repetition of basalt flows by the strike fault at "Red Buttes”• View is toward the south*

; .fa;'

P

o

S

_ »

V,-

jVv y

’•

■"**.:

* 4» ■'■

j*

JW

*V

j,

«*V

a

h

*

■» -* K "

v

' £StaB£o ■* ? i-■,.v, •» ,&ahfrfr> . ^L-‘ •• -•

;X £?■£

T. >»

, * ”^,

•

■

*

•■ ■' ■

,. *•

"’ ?■*''vV *'V““

Nt, *■v " v «, - '- 3 •*t# "* ';, *W

" yi'

•< < '

Figure 12— Distortion of the beds at the strike fault shown in Fig* 11. ^Formally dipping beds are visible at right; upthrown basalt and dis­ torted beds at left. ^

: ■-y^^

-- -‘-ayyt

CHAPTER IV CENOZOIC HISTORY I.

PRE-RICARDO EVENTS

The Mojave Desert region is believed to have been subjected to more or less continuous erosion during the early Tertiary Period.

In the Upper and possibly Middle

Miocene, continental sediments, generally referred to as the Rosamond "series”, were widely deposited in this region. Hulin^ has stated that this deposition was caused by faulting and warping which destroyed the old well-developed drainage sustem and formed local basins.

In the Randsburg

Quadrangle this faulting and warping was accompanied by the intrusion of acidic dikes, sills, and pipes, and a short time later by the intrusion of basic dikes.

In other parts

of the Mojave Desert the intrusions reached the surface to form acidic and basic extrusives which are intercalated with the Rosamond sediments. In the area of the present investigation, those Rosamond sediments which still exist at present accumulated in two local basins.

Acidic intrusives similar to those of

the Randsburg Quadrangle entered the basement rocks.

These

G. Hulin, "Geology 6c Ore Deposits of the Randsburg Quadrangle, California11, Calif. State Min. Bu., Bull. 95 > p. 6 7 , 1925.

intrusions may have also invaded Rosamond sediments that were later removed by erosion (See pages 12 and 33)*

Later

in the Miocene the area was uplifted and the Rosamond sedi­ ments were tilted to the northwest.

The erosion that

followed removed any Rosamond sediments which may have ex­ isted in the topographically higher portions of the area, and beveled the sediments deposited in the two basins. II.

EVENTS OF RICARDO TIME

Although late Miocene erosion had beveled the Rosa­ mond sediments, several topographically high localities com­ posed of resistant igneous and metamorphic rocks were still present in the area at the beginning of Ricardo time.

The

river system that existed at this time began to deposit cobbles and boulders in the lower portion of the area.

The

composition and rounded condition of the cobbles and boulders indicate that they were carried in from an area of metamorphic and igneous rocks some distance away.

Hulin

p

has observed isolated patches of similar conglomerate widely scattered throughout the bearles Lake district, and suggests that the material was brought in from a region somewhere to the north •

p

C. Hulin, 11Geologic Features of the Dry Placers of the Northern Mojave Desert", Calif. Jour. Mines & Geology, vol. 30, pp. j4.2O-l4.2i, I93I4-.

An interval of explosive volcanism began shortly after the deposition of the river conglomerates, and much of the area was covered with thick deposits of ash*

A thick

bed of coarsely fragmented basic andesite was also deposited during this interval of explosive voleanism*

A basaltic

flow was quietly extruded in the area at still an early date in Ricardo time, but after a large amount of pyroclastic material had accumulated*

The flow and some of the under­

lying ash were later dissected by a river or river system. For some time the river or river system carried in and de­ posited cobbles and pebbles of volcanic material from an­ other area.

Extensive stream deposition of arkosic sedi­

ments also took place before the middle of Ricardo time, at least in the south/vest half of the area. Renewed volcanic activity occurred in the area near the middle of Ricardo time, with the quiet extrusion of basaltic flows.

Stream dissection as well as deposition oc­

curred in the Red Rock Canyon area during the interval be­ tween outpourings of basalt.

In the Last Chance Canyon area,

the well-bedded deposits of arkose, tuff, limestone, and chert, which are in part associated with the basalt flows, suggest the presence of a lake or very sluggish rivers In this part of the area in middle Ricardo time. During the later part of Ricardo time, large quantities

of arkosic material and finer sediments were brought into the area and deposited by streams.

A large anount of this

material was derived from a nearby area of granitic rocks; probably the ancestral Sierra Nevada Mountains to the west. The large quantities of immaturely weathered arkosic sediments occurring throughout the Ricardo sequence suggest that the Ricardo climate was rather arid.

However, studies

of both the Ricardo fauna-^ and floral indicate that a semiarid climate prevailed, in contrast to the extremely arid climate existing in the region at present. III.

10ST-RICARDO HISTORY

Uplift along the Garlock fault,

sometime during the

Pliocene, resulted in the formation of the ancestral El Paso Mountains and the tilting of the Ricardo beds to the north­ west.

The erosion that followed this uplift continued until

an old age erosion surface was developed.on the Ricardo strata.

The Black Mountain basalt was extruded upon this

old erosion surface, very late in the Pliocene or in the early Pleistocene.

Renewal of regiona.1 uplift occurred

3

J. C. Merriam, "Tertiary Mammalian P'aunas of the Mojave Desert", Univ. Calif. Pubs., Bull. Dept. Geology, vol. 11, p. 526, 1919. ^ I. E. Webber, "Woods from the Ricardo Pliocene of Last Chance Gulch, Calif.", Carnegie Inst. Wash., Pubs., no. 1l12, pp. 113-13k, 1933.

at this time or shortly thereafter*

Uplift along the C-arlock

fault during the Pleistocene resulted in the formation of the modern El Paso Mountains at approximately the same time the modern Sierra Nevada Range was rising to the west.

This

Pleistocene uplift of the El Paso Mountains was responsible for the additional tilting and much of the fault dis­ placement of the lower half of the Ricardo beds.

A large

portion of the upper Ricardo strata was not greatly affected by the Pleistocene uplift and was buried beneath the Sierra Nevada piedmont alluvial slope. The Sierra Nevada alluvial slope and the underlying Ricardo beds have been undergoing dissection in Recent time. The Ricardo beds in the El Paso Mountains have been affected by an even greater amount of Recent dissection.

Features

are present which suggest some uplift has occurred in the area during Recent time.

CHAPTER V ECONOMIC ASPECTS I.

PUMICITE

The pumicite of this area is a fine, well sorted, vitric, light grey to white, tuff.

It is rained for use in

the manufacture of scouring powders, tooth powders, insu­ lation, and a number of other products.

The pumicite is

called seisraotite^ by the Cudahy Packing Company. Commercial deposits of pumicite occur a short distance below the andesite breccia and at a horizon near the middle of the Ricardo beds. several other horizons.

Smaller deposits occur at

Some of the fine ash that formed

the pumicite may have been transported only by the wind and laid down upon dry land.

However the nature of the sedi­

ments associated with the upper deposits indicates deposition of the ash in lakes or quiet streams, after an initial transportation by the wind. The most extensively worked deposit of those oc­ curring below the andesite breccia is located north of Last Chance Canyon, and is designated on the accompanying

Spelled sesomotite on the topographic base sheet of the accompanying geologic map.

52 geologic map as the Holly Mine. Calsileo Corporation,

The deposit is owned by the

The material is processed into

different size grades at a mill located on the property. The high grade pumicite occurs in a bed approximately ten to twenty feet in thickness, and has been worked by open cuts along the strike. Below the andesite breccia in the area between Iron and Last Chance canyons, a pumicite bed has been developed by the Hancock Oil Company of California.

This deposit,

known as the Snow White llacer Claim, has been developed by open cuts and by tunneling a short distance into the bed. The pumicite horizon occurring near the middle of the Ricardo section in Last Chance Canyon has been extensively developed by the Cudahy Packing Company, manufacturers of Old Dutch Cleanser.

The deposit has been developed by

tunneling into the dip of the bed, which outcrops high on the west wall of Last Chance Canyon (Figure 13).

A small

open cut development has been attempted farther to the north along the strike of this same pumicite horizon (Figure lip). No commercial pumicite deposits were observed in the Red Rock Canyon area. II.

PLACER GOLD

Detridal gold has been concentrated in some of the

alluvial deposits of the drainage systems of Last Chance Canyon, Iron Canyon, and Red Rock Canyon.

Development of

the placers has been attempted intermittently for many years the greatest obstacle to the efficient recovery of the gold having been the scarcity of water.

At the time of this

writing, placer operations are being attempted at two locali­ ties, one in Iron Canyon and the other in Last Chance Canyon Hulin^ has previously noted that the gold has been concentrated from the basal Ricardo conglomerate, where it occurs in a highly disseminated condition.

Uplift and

consequent erosion of the basal Ricardo beds has caused the gold to be concentrated in both pre-Recent and Recent al­ luvial deposits.

2

C. D. Hulin, “Geologic Features of the Dry llacers of the Northern Mojave Desert”, Calif. Jour. Mines Geolo­ gy » vol. 30, pp. ]g2ip-lp25, I93I4-.

Figure 13 Cudahy Mine at the pumicite horizon near the middle of the Ricardo beds, Last Chance Canyon

V

Figure ll|_ Open cut in the pumicite horizon near the middle of the Ricardo beds*

APi-EFDIX

APPENDIX A REVIEW OF THE RICARDO FObSIL AbbEMBLAGE The best vertebrate fossil localities are located stratigraphicaily above the basalt flows in the Red Rock Canyon area.

Both plant and vertebrate remains have been

found near the middle of the Ricardo beds in Last Chance Canyon.

The lowest Ricardo beds occur in the Last Chance

Canyon section.

To the knowledge of the writer, no lossils

have been found in the lower 800 feet or so of this section. Field parties from the University of California, in 1911> 1913, and 191?, collected a large number of verte­ brate fossils from beds in the vicinity of Red Rock Canyon. The results of the research conducted upon these and other Mojave Desert vertebrate collections were presented in a series of papers by Merriam^.

The research revealed that

the fauna from Red Rock Canyon includes mammals with Lower Pliocene characteristics, whereas the fauna found near Barstow, in the central Mojave Desert, is distinctly Upper Miocene.

Consequently, Merriam adopted the name Ricardo

for the beds and fauna at Red Rock Canyon, to distinguish them from the Upper Miocene deposits of the Mojave Desert.

^ See Bibliography.

57 In regard to the possible correlation of the Ricardo fauna, Merriam^ noted its resemblance to the upper Snake Greek fauna of Nebraska and the Republican River fauna of Kansas. Since the appearance of Merriam's papers, a number of additions have been made to the Ricardo assemblage. reported the first avian fossil from the beds.

Miller^

Stock and

Furlong^* made several additions from mammalian remains col­ lected near the middle of the Ricardo sequence at Last Chance Canyon.

They suggest that the Ricardo assemblage may be

slightly later than the Republican River fauna, and slightly earlier than the Upper Snake Creek fauna.

The latest ad­

dition to the Ricardo fauna was reported by Green^ in I9I4-8 . Fossil plants, occurring near the middle of the Ricardo sequence at Last Chance Canyon, have been studied by Webber 8 Despite the faunal differences between the Ricardo

2

J. C. Merriam, "Tertiary Mammalian Faunas of the Mojave Desert” , Univ. Calif. Pubs., Bull. Dept. Geology, vol. 11, pp. Ij.37-ij.50, 1919. 3 L. H. Miller, "A Fossil Goose From the Ricardo Pliocene”, Condor, vol. 32, pp.208-209, 1930. ^ C. Stock and E. L. Furlong, "New Candid and Rhinocerotid Remains From the Ricardo Pliocene of the Mojave Desert California", Univ. Calif. Pubs., Bull. Dept. Geol. Sci., vol. 16, pp. I4.3-60, 19267 5 M. -• Green, A tt New Species of Dog From ^ theLower Pliocene of California", Ibid. , vol. 28, pp. 81-90, 199-8. ^ I. E. vl/ebber, "Woods From the Ricardo Pliocene of Last Chance Gulch, California", Carnegie Inst., Washington, Pub, I4-I2, pp. 113-13)p, 193k.

53 and the Barstow beds, Reed^ placed the Ricardo in the Upper Miocene.

In support of this view Reed, wrote:

. . . In the Mint Canyon area J. H. Maxson has collected from beds which lie below a marine zone considered by W. P. Woodring to be Upper Miocene (Ciebo) in age, a mam­ malian fauna containing horse teeth apparently belonging to Hi oparion mohavense, the commonest Ricardo species. In the same formation are other teeth referred to two of the Barstow Merychippus species. . . . It suggests that possibly the difference in time between the Barstow and the Ricardo is less than Merriam supposed. In addition . . . a tooth of Hipparion mohavense, the common Ricardo species, has recently been described by Chester Stock as coming from the Puente formation of the Los Angeles district. the exact stratigraphic po­ sition of the Puente bed that furnished this fossil is unfortunately not known, but the formation as a whole is commonly referred to the Upper Miocene. Keed further stated that even if the Ricardo fauna is cor­ relative with the European Pontian stage, European geologists are not agreed as to whether the Pontian is Upper Miocene or Lower Pliocene. Q Teilhard de Charden and Stirton

correlated the

Piicardo and several other California faunas with the Euro­ pean Pontian stage.

They state that there is no verte­

brate faunal break to separate the Miocene aid Pliocene in

7

R. D. Reed, Geology of California (Tulsa: American Associated Petrolium Geologists, 1933), pp. 221-223. ® P. Teilhard de Chardin and R. A. Stirton, nA Corre­ lation of some Miocene and Pliocene Mammalian Assemblages in Rorth America and Asia, With a Discussion of the Mio-Pliocene Boundary", Univ. Calif. Pubs., Bull., Dept. Geological Sci., vol. 23, pp. 277-290, 19357-

59 North America as in Eurasia,' but that the most satisfactory place for an arbitary line occurs with the first appearance of such genera as Hipparion and Pliohippus.

They have found

no certain evidence for the contemporaneous existance of Merychippus and well-defined species of Hipparion and Pliohippus. A review of the literature reveals that the marine and non-marine Mio-Pliocene boundaries are not perfectly correlative, but that the Ricardo fauna can be placed in the non-marine Lower Pliocene, as it stands today, A list of the known fauna and flora from the Ricardo beds follows.

The list has been compiled from the works cited. FAUNA

Reptilia Testudinate remains Ave s Branta howardae

Miller

Carnivora Canid, small near Canis? vafer Leidy Aelurodon? aphobus Merriam Aelurodon? possibly aphobus Merriam Aelurodon?, two spp. Aelurodon or Tephrocyon, two spp. Tomarctus robustus Green Hadrocyon mohavensis, Stock and Furlong Mustela? buwaldi Merriam Ischyrosmilus osborni Merriam Felid, large Felid, small not Ischyrosmilus

60 Lagomorpha Lepus? sp. Proboscidea 'Tetrabelodon? sp. Squidae Hipparion mohavens© Mepriam Hipparion mohavense callodonte Merriam Hipparion, two spp. Pliohippus tantalus Merriam Pliohippus fairbanksi Merriam Pliohippus sp., near P. mirabilis (Leidy) Oreodontidae Merycochoerus ? (Pronomotherium?). californicus Merriam Camelidae Procamelus, two spp. Pliauchenia sp. Alticamelus? sp. Bovidae Merycodus sp., near M. necatus (Leidy) Rhinocerotidae Aphelops sp. Peraceras? sp.

FLORA woody plants Pinus kelloggi Webber Gupressus sp. Palmoxylon mohavensis Webber Quercus ricardensis Webber Robinia alexanderi Webber undetermined dicotyledon fungi hyphae in wood of Pinus, Cupressus and Robinia hyphae and spores in bark fruiting bodies in palm root

BIBLIOGRAPHY

BIBLIOGRAPHY Baker, Charles Laurence, "Notes on the Later Cenozoic History of the Mojave Desert Region in Southeastern California", Univ. California Pubs., Bull. Dept. Geology, vol. 6, PP. 3 3 3 - 3 8 3 , 1911. ______ , "Physiography and Structure of the Western El Paso Range and the Southern Sierra Nevada", Univ. California Pubs., Bull. Dept. Geology, vol. 7, pp. 117-llp2. Fairbanks, Harold W., "Red Rock, Goler, and Summit Mining Districts", Calif. State Mining Bureau, 12th Ann. Report, pp. i4.56-l4.5 8 , 189I4I. , "Notes on the Geology of Eastern California", American Geologist, vol. 17, pp. 67-69, 1896. Gilbert, Grove Karl, "Report on the Geology of Portions of Nevada, Utah, California, and Arizona", Geographical and Geological Explorations and Surveys West of 100th Meridian, vol. 3, pp. 1I4.2-II4.3 , 1$75>. Green, Morton, "A New Species of Dog From the Lower Pliocene of California", Univ. California Pubs., Bull. Dept. Geol. Sciences, vol. 28, pp. 8l-90j I9I4-8T Hershey, Oscar, "Some Tertiary Formations of Southern Cali­ fornia", American Geologist, vol. 29, pp. 3l}-9“372, 1902. Hopper, Richard H., "Geologic Section From the Sierra Nevada to Death Valley, California", Geol. Soc. America, Bull. , vol. 58, pp. ipl5-i4-17, 19^-7. Hulin, Carlton D . , "Geology and Ore Deposits of the Randsburg Quadrangle of California", Calif. State Mining Bureau, Bull., bull. 95, 1925. ______ , "Geologic Features of the Dry Placers of the Northern Mojave Desert", Calif. Jour. Mines and Geology, vol. 30, pp. i 4. i 9 - l 4.2 2 , 193^ Merriam, John C., "New Protohippine Horses From Tertiary Beds on the Western Border of the Mojave Desert", Univ. California Pubs., Bull. Dept. Geology, vol. 7. PP. Ii35i+ip., 1913.

62 ______ , "New Horses Prom the Miocene and Pliocene of Cali­ fornia", Univ. California Pubs. , Bull. Dept. Geology, vol. 9, p F T T 9 - 5 « , 191^. , "Relationships of Pliocene Mammalian Faunas Prom the Pacific Coast and Great Basin Provinces of North America", Univ. California Pubs., Bull. Dept. Geology, vol. 10, pp. U-21— , 1917• ______ , "Tertiary Mammalian Faunas of the Mojave Desert", Univ. California Pubs., Bull. Dept. Geology, vol. 11, pp. ii.37-505, 1919. Miller, Loye H . , "A Fossil Goose From the Ricardo Pliocene", Condor, vol. 32, pp. 208-209* 1930. Reed, Ralph D . , Geology of California. Assoc. Petrolium Geologists, 1933.

Tulsa, Okla.. : Am.

Stock, Chester and E. L. Furlong, "New Canid and Rhinocerotid Remains From the Ricardo Pliocene of the Mojave Desert, California", Univ. California Pubs., Bull. Dept. Geol. Sci., vol. 16, pp. J4.3-60, 1926. Stock, Chester, "Can.id and Proboscidean Remains From the Ricardo Deposits, Mojave Desert", Carnegie Inst. 'Washington, Pub., no. 393, p p • 39-57, 1928. Tarr, W. A., "Concretions in the Champlain Formation of the Connecticut River Valley", Geol. Soc. America, Bull., vol. 56, pp. 1519-1552, 1 9 3 5 T “ Teilhard de Chardin, P. and R. A. Stirton, "A Correlation of Some Miocene and Pliocene Mammalian Assemblages in North America and Asia, With a Discussion of the Mio-Pliocene Boundary", Univ. California Pubs., Bull. Dept. Geol. Sci., vol. 23, pp. 277-290, 1934-. Tucker, W. B., R. J. Sampson and G. B. Oakeshott, "Mineral Re­ sources of Kern County", Calif. Jour. Mine- s and Geology, vol. 55, pp. 203 -297 , 1959. Webber, Irma E . , "Woods From the Ricardo Pliocene of Last Chance Gulch, California", Carnegie Inst. Washington, Pub., no. l±12, PP* 113-135* 1935*

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