The impact of tectonic activity in the development of Monterey Submarine Canyon.

1H

1 JBWlW

Hi

mHH

NAVAL POSTGRADUATE SCHOOL

Monterey, California

THESIS

THE

1 IMPACT OF TECTONIC ACTIVITY

IN

THE DEVELOPMENT OF MONTEREY
SUBMARINE CANYON

by

Robert Llcyd Allen, Jr.

March 19 82

Thesis

Ad\

risors : E. C. Haderlie

H. G. Greene

Approved for public release; distribution unlimited.

T203802

UNCLASSIFIED

SECURITY CLUflflCATlON OF THIS PAGE rWhmt Datm fawwg

REPORT DOCUMENTATION PAGE

REROR+ NUMlIM

2. GOVT ACCESSION NO

4 TITLE (•"<* Submit)

The Impact of Tectonic Activity in the
Development of Monterey Submarine Canyon

READ INSTRUCTIONS
BEFORE COMPLETING FORM

J. RECIRlEN T'S C AT AlOG NUMBE P

S TYPE OF REPOPT » PERlOO COVEREO

Master's Thesis;
March 19 8 2

7. AuTMOR.«>

Robert Lloyd Allen, Jr

• PERFORMING ORGANIZATION NAME ANO AOORESS

Naval Postgraduate School
Monterey, California 9 39 40

• PERFORMING ORG. REPORT NUMBER

». CONTRACT OR GRANT NLMBERf'j

10. PROGRAM ELEMENT PROJECT TASK
AREA * «ORK UNIT NUMBERS

II CONTROLLING OFFICE NAME ANO AOORESS

Naval Postgraduate School
Monterey, California 93940

12 REPORT OATE

March 1982

jj — MOM,TORlNG AGENCY NAME * AOORESSO/ dlllmnnt Ittm Ctmtrolltnt OHIca)

19. NUMBER OF PAGES

57

IS. SECURITY CLASS, lot fM« rfporl)

Unclassified

\Vm. DECLASSIFICATION/ OORNGRAOlNG
SCHEDULE

lV DISTRIBUTION STATEMENT (ol thl» Rmaott)

Approved for public release; distribution unlimited.

!7 DISTRIBUTION STATEMENT (ol Ihm mbmtrmcl mnffd In Block 30. II dllfrmnl *»•» *««M»rt;

IB. SuRRLEMENTARY NOTES

"». KEY WORDS CCriMur o« ••»•••• »ldm II n.e...«rr ■"* ««**»«<* *T Woe* numbmr)

Monterey Submarine Canyon
submarine canyon
tectonics

« ABSTRACT fCa«iil«u» an *•»•-•• Zmt II nmwmy *>* 1 0*f>i I tr »r ».oe* numft)

Evidence is presented that indicates that Monterey
Submarine Canyon was once the terminus ot a major land
drainage system. This PreTexisti ngdr ainage sys t^

in evidence today because it has Deen . al^ere^?YH,^5 on
along the San Andreas Fault. A numerical model based on
conservation of mass and plate tectonic reconstruction is
utilized to reconstruct the topography of the region as

DO 1473 EDITION OF I NOV »» IS OBSOLETE

S/N 1 102-0 14* MO 1

UNCLASSIFIED .

ic-jjiT" :--i4ai/iCAT!ON o- -his »-g« • •*•» ^-'- »"»•'•«-)

UNCLASSIFIED

f^cu'-T* :i a»»i»iC« "9n a« T»'* »*««'■»■■■■«»»

(20. ABSTRACT Continued)

appeared prior to onset of motion along the San Andreas Fault
Model results indicate that the Colorado River may have
drained into Monterey Bay during early Miocene time.

DD . ForrTJ„ 1473 2 ^CLASSIFIED

Approved for public release; distribution unlimited

The Impact of Tectonic Activity
in the Development of Monterey
Submarine Canyon

bv

Robert Lloyd Allen, Jr.
Lieutenant, United States Navy
. S., Florida State University, 1975

Submitted in partial fulfillment of the
requirements for the degree of

MASTER OF SCIENCE IN METEOROLOGY AND OCEANOGRAPHY

from the

NAVAL POSTGRADUATE SCHOOL
March, 19 8 2

ABSTRACT

Evidence is presented that indicates that Monterey Sub-
marine Canyon was once the terminus of a major land drainage
system. This pre-existing drainage system is not in evidence
today because it has been altered by displacement along the
San Andreas Fault. A numerical model based on conservation
of mass and plate tectonic reconstructions is utilized to
reconstruct the topography of the region as it appeared prior
to onset of motion along the San Andreas Fault. Model results
indicate that the Colorado River may have drained into
Monterey Bay during early Miocene time.

TABLE OF CONTENTS

I. INTRODUCTION

II. PROCEDURE 14

III. RESULTS 45

IV. CONCLUSIONS 51

LITERATURE CITED 52

LIST OF REFERENCES 54

INITIAL DISTRIBUTION LIST 55

ACKNOWLEDGMENTS

This study would not have been possible without the efforts
of my co-advisors; Dist. Prof. E. C. Haderlie of the Naval
Postgraduate School and Dr. H. G. Greene of the U. S. Geologi-
cal Survey.

Dr. Haderlie 's support and guidance were the lifeblood
of this thesis during the early going. His unparalleled
scientific curiosity and foresight literally made this study
possible.

Dr. Greene agreed to co-advise in spite of a heavy work
load with the U. S. Geological Survey. I was indeed fortun-
ate to have the foremost authority on the geology of Monterey
Bay as a co-advisor.

Two very capable members of the NPS Meteorology Department
provided valuable assistance. Prof. R. T. Williams was very
helpful with model design and trouble-shooting suggestions.
P. W. Phoebus, an outstanding programmer, provided much needed
technical assistance in programming.

Most of all, I would like to thank my wife, Teresa, who
shared in all the ups and downs from beginning to end, and
who is a constant source of inspiration to me.

I. INTRODUCTION

Monterey Submarine Canyon is the largest of the California
submarine canyons. Traced seaward from its head near Elkhorn
Slough in Monterey Bay, the canyon axis follows a meandering
path for approximately 100 km before emerging as a fan valley
at a depth of about 3 km (Figure 1) . From this point, the
fan valley can be traced for another 400 km across the Monterey

deep-sea fan. The volumes of the canyon and the fan have been

3 3

estimated to be 450 km and 30,000 km respectively (Menard,

1960). The walls of the canyon are approximately 1,500 m high

at one point, producing relief comparable to that of the Grand

Canyon of the Colorado River (Figure 2) .

Such is the magnitude of this feature that two of its
tributaries have been named. Carmel Canyon branches south
and heads very close to shore off Monastery Beach in Carmel
Bay. Soquel Canyon branches northward near the canyon head
and extends toward the town of Soquel, east of Santa Cruz.

The major canyon axis follows a fault contact near the
head and is flanked by Tertiary sediments on both sides. At
its outer limits; beyond about 20 km from its head at Elkhorn
Slough, there is no indication of faulting along the canyon
axis and the canyon course is purely erosional (Greene, 1977).
Soquel Canyon is cut entirely in poorly indurated seimentary
strata, while. Carmel Canyon is eroded in granodiorite on the
east and highly indurated sedimentary rocks on the west.

Figure 1, The Monterey and Carmel Submarine Canyons

off the central California Coast. (Diagram
by Tau Rho Alpha, USGS)

-360

-2772

Grand Canvon
of the Colorado

r2600

Figure 2. A comparison of the profiles of the Grand

Canyon of the Colorado River and the Monterey
Submarine Canyon, showing them to have similar
relief. Elevations relative to sea level are
given in feet. Vertical exaggeration is 5X.
(After F. P. Shepard, Submarine Geology, 3rd
Ed., Harper and Row, 19 7 3.)

Like many of the submarine canyons along the California
coast, Monterey Canyon does not lie seaward of a large land
drainage system. The Salinas River is the largest of
several small rivers which drain into Monterey Bay, all of
which appear diminutive in comparison with Monterey Canyon.
An explanation of this enigma was proposed by Martin and Emery
(196 7) when they suggested that Monterey Canyon had received
drainage from the Great Valley of California, through the San
Francisco Bay region during late Miocene, Pliocene and early
Pleistocene time. Although some questions were answered by
this hypothesis, others remain unanswered. Martin and Emery
noted that the amount of material in Monterey Fan could not
have resulted from the Great Valley connection which they
proposed. In addition, they noted the existence of buried
erosional features which led them to conclude that Monterey
Canyon is a re-excavation of a pre-existing submarine canyon.
As Martin and Emery noted, these buried erosional features,
Elkhorn Erosion Surface and Pajaro Gorge, pre-dated their
Great Valley Connection. The age and size of this pre-existing
canyon were established by Greene (19 77) using seismic profiling
techniques. Greene's profiles confirm the fact that this pre-
existing canyon existed prior to early Miocene time and is
still not entirely re-excavated in some areas (Figure 3) .
Greene's evidence indicates that the lower reaches of Monterey
Canyon have been displaced northward and are represented today
by Pioneer and Ascension Canyons. According to Greene's theory,

10

Figure 3. Basement contour map Monterey Bay Region,
California (from Greene, 1977)

11

displacements along the Palo Colorado-San Gregorio Fault and
the Ascension Fault over the past 20 million years may have
moved these canyons into their present positions.

Although it is presently one of the largest submarine
canyons in the world, there is evidence to indicate that
Monterey Canyon is an incomplete re-excavation of a larger
canyon. The mechanism involved in excavation of this earlier
canyon and creation of Monterey Fan is unknown.

One possible explanation is that Monterey Canyon was the
terminus of a large land drainage system which existed in
pre-early Miocene time. Large scale deformation of topography
since early Miocene has removed the canyon from its source
and produced changes in the drainage patterns of the area
(Clark and Rietman, 19 73; Greene, 19 77; Martin and Emery,
19 67; Starke and Howard, 19 68) .

The topographic changes which have occurred since early
Miocene along the west coast of North America have been exten-
sive. About 30 million years ago, during Oligocene time, the
East Pacific Rise came in contact with the North American
Plate. Relative motion between the Pacific and North Ameri-
can plates came to be expressed along right lateral strike-
slip faults on the continental margin. During early Miocene
time, the zone of strike-slip faulting between the Pacific
and North American Plates shifted inland to the San Andreas
Fault. Since its inception, approximately 300 km of right
slip has occurred along the San Andreas Fault (Crowell, 1962) .

12

Such large-scale motion would undoubtedly have had great im-
pact on any pre-existing drainage system. Reconstruction of
topography as it existed prior to the onset of motion on the
San Andreas Fault is difficult. Motion along the fault has
not been constant in either speed or azimuth over this inter-
val. In addition, compressional forces along the fault have
uplifted areas resulting in the creation of new topographic
features (Greene, 1977).

Due to the complexity of the problem, a numerical model
is utilized to reconstruct the topography of the area as it
appeared in early Miocene time. The model simply reverses
motion along the San Andreas Fault utilizing data from plate
tectonic reconstructions and imposing mass conservation. It
does not reverse the effects of erosion or deposition, motion
along other faults, or any other forces. However, since motion
along the San Andreas Fault has contributed greatly to the
alteration of topography since the early Miocene, results from
such a model may be expected to provide useful insights into
early Miocene topography.

13

II. PROCEDURE

The model was designed to simulate a reversal of the
motion which has occurred along the San Andreas Fault over
the past 21 million years. In simulating this reversal,
mass must be conserved. The conservation of mass states
that:

dm 3m ■* ± ± ■*■ n , , ,

^r; = ^-+v-7m + mV-v = 0/ (1)

where

m = mass,

t = time, and

v = velocity.

In other words, the total change in mass is equal to the local
time change plus mass flux divergence. Since the total change
is zero, mass is conserved and the local change must balance
transport:

|? = - v • 7m - mV • v. (2)

Since total mass equals mass density (p) times total volume
(V) , then:

^g±- = - v • 7(pV) - pVV • v (3)

14

If we assume that density is constant in space and time,
it can be eliminated:

£JL = _ v . VV - VV • v (4)

Finally, when dealing with a unit area, volume is ex-
pressed in height above/below sea level (h) (Equation (5)

3h ■*• -± ± ■*■

~ = - v • Vh - hV • v (5)

From Equation (5) , with an initial height field and a
velocity field, topographic changes in time may be predicted.

The height field is a 70 x 64 array of topographic and
bathymetric heights as illustrated in Figure 4 . The grid
interval is 10 minutes of longitude in the x direction and
10 minutes of latitude in the y direction (15.2 and 18.5 km,
respectively) . This interval in the x direction corresponds
to true grid spacing at 35 degrees north, and introduces a
departure from a spherical earth of approximately 7% at the
northern and southern extremes.

While the height field simply provides initialization for
the model, the velocity field defines the fault and drives
the model. As illustrated in the initial velocity field
(Figure 5) , the portion of the grid which lies to the east
of the San Andreas Fault is held fixed while that portion to
the west of the fault is moved southeastward. Along the fault

15

40*20 N

Fixed Boundary Conditions

125*0'W

4,080 Data Points
70 (x) x 64 (y)
Dx = 15.2 km
Dy = 18.5 KM

133'30'W

Permeable Boundary Conditions

29*50'N

Figure 4 . Grid features

16

Figure 5. Velocity field: 0-4.5 million years before
present, vectors indicate direction and
relative magnitude of velocity at each point.

17

w
w \
WW
w w^
w w\
w w\
\\\\\
w w\

W W\
W W\

w w\

\\\ w
w w\
u\\\
w W\
w \ w
w w\

W W\

w \ \ \

W \ W

w w\

,\\\\\
AWW
w w\
AWW
, w w\
AWW
A\ w\
aw w
AWW
AWW
, w w\
AWW
AWW
, \\ w\
,\\ \\\
AWW

. W \\\

. \\\\\
. \\ w\
.\\ \\\
www
www
www
.\\\\\
www
. w w\

. W W\

www
» w w\
. w w\

WWW
WWW

www

WWW

\ \ \ \ \

Veloci ty NFi eld

T = 4.5 - 10

W
\\\

\ W ^

ww

WW
WW
WW
w\ \,
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW

\w \

w\ \

WW

w\ \

WW
WW

WW
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW
WW

w\ \
WW
WW
WW
WW
WW
WW
WW
WW

sv
w
s \ \>\

W V
WW"

w w \
\ w w
w w\
www

WWW

www

www

\ w w N
w \ w y

WWW

www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www
www

WW

,v

AW

A \ W '

^\\ \ \ '
, \ \\\ \

. W \> W
A W 1 W
, w\ \W
. w w\w
aww

A W W\
. W WW

.www
,w\ w
.www

, W WW

, www
,\ w w

,W WW

.www

.www
.www
.www
.www
.www
.www
. w w

w^

WW* •

AWW '

www
w ww^

, W W
.WWW'

*w w w w

AWWW

A W W s
.W WWW

.WW WW \ ^

, W w CTV \ ^

.WW

AW W

A WW

A WW

.www

.WWWWWWW

.ww w£ ww\ w

AW WWW WW
W W\K W WW\

J w w\k w ww\

,\1 W\ W.\ ■ W >'■>

s.

WW. www www

S \ V.'aW \ '. '-. \ '. WW k. \ 5 \ '

7TTTTWTW

Figure 6.

Velocity field: 4.5-10 million years before
present, vectors indicate direction and
relative magnitude of velocity at each point,

18

Figure 7 .

Velocity field: 10-21 million years before
present, vectors indicate direction and
relative magnitude of velocity at each point.

19

itself, there is a gradation of the velocity field as depicted
in Figure 8. At the position of the fault, the magnitude of
the velocity field is reduced by one-half. At the next grid
point to the east, the velocity is one-quarter as large as
it is in the moving block. At the first grid point to the
west of the fault, velocity is three-quarters as large as
the velocity of the moving block. This configuration results
in a zone of velocity gradation across the fault and prevents
the numerical instabilities which may arise from modelling
the fault as a more severe velocity discontinuity. Previous
attempts without a gradation of velocity across the fault
resulted in unreasonable topography. The components of the
velocity field, speed and direction, will be discussed
separately.

Directions were derived from an algorithm which generates
smooth fields to match directions at three points where direc-
tions are known from plate tectonic reconstructions (Silver
et al . , unpub . data) . Directions of relative motion between
the North American and Pacific Plates relative to three points
on the North American Plate during three time intervals are
presented in Table I. Corresponding values from the model
algorithm are displayed in parentheses for comparison. Since
the model simulates a reversal of motion, all directions are
reduced by 180° to produce the velocity fields depicted in
Figures 5-7. These figures illustrate the velocity fields
used at different times in the model. The vectors to the left

20

KM W

15.2

KM W

Fault
Position

15.2

KM E

30.

KM

I 1 I 1 I

v 3/w 1/2V i/w 0

Figure 8. Velocity gradient along the fault

21

TABLE I
(From Blake et al. , 1978)

Azimuth of Average Movement Direction of Pacific
Plate Relative to Points on North American Plate

Values from model algorithms in parenthesis

Age (my) 36°N, 121. 5°W 33°N, 119°W 26°N, 112°W

0--4.5 321.2° (321.2°) 318.6° (318.5°) 311.7° (311.7°)

4.5--10 328.0° (328.0°) 325.7° (325.6°) 319.5° (319.5°)

10 — 21.2 339.0° (339.2°) 335.0° (334.9°) 323.9° (324.0°)

side of the figures represent the moving block. It can be
seen that there is a very slight change in the direction from
one end of the field to the other in all three figures as
would be expected from Table I. On the right side of each
figure is an area with no vectors. This is the stationary
portion of the grid. The shorter vectors at the intersection
of the stationary block and the moving block represents the
fault zone. As previously discussed, there is a gradient in
the magnitudes of the velocities across the fault. This is
, reflected in the comparatively shorter vectors in the fault
zone. The actual position of the San Andreas Fault is super-
imposed on these figures for comparison. It can be seen from
Figures 5-7 and from the values in Table I that the motion
changes with time to a more westerly direction becoming less
compressional and more nearly aligned with the fault axis.

Speeds were derived from a combination of sources. Plate
tectonic reconstruction (Atwater, 1973) produces an accelerating

22

velocity field which would have resulted in approximately
610 km of offset if all motion had been expressed as fault
displacement. How much of this displacement is actually
expressed in offsets along the San Andreas and other faults
is unclear. Evidence for a 260 km offset along the San Andreas
Fault (Crowell, 1962) establishes a conservative estimate
and is the reference displacement utilized in this model. Al-
though displacements from plate tectonic reconstruction do not
match displacements derived from geologic evidence, the accelera-
tion of motion between two plates, as derived from plate tec-
tonic reconstruction, is not disputed by geologic evidence
(Atwater, 19 73) . This acceleration of motion is incorporated
into the model by reducing velocities from plate tectonic
reconstruction such that the total resultant offset equals 260
km. This is accomplished by multiplying the velocities by
a scaling factor, s = 260 km/610 km = .426. Resultant scaled
velocities as well as original velocities derived from plate
tectonic reconstruction (Atwater, 1973) are listed in Table II.

TABLE II

Time Period

(Million years
before present)

21 — 10

10—4.5

4.5 —

Relative Motion

Pacific/N. Ameri-
can Plates

1 . 3 cm/yr

4 . 0 cm/yr

5 . 5 cm/yr

Relative Motion

San Andreas
Fault

0 . 6 cm/yr

1 . 7 cm/yr

2 . 3 cm/yr

23

The height and velocity fields are substituted into the
Continuity Equation (Equation (5)) using finite differencing
schemes. In discussing differencing schemes, the following
coordinate system and symbology will be used:

H(i,j,t)

reference point, height at a location on
a horizontal plane identified by coor-
dinates i (east) and j (north) at time t

u = velocity component in the i (east)
direction

v = velocity component in the j (north)
direction

At = interval of time (200,000 years in this
model)

Ax = interval of space on the i axis . For
example, the distance between H

and H , . , , . , »
(1+1,3 ft)

(i,j,t)

Ay = interval of space on the j axis. The

distance between H,. .. and H,. ,n .»

U,D,t) (i,j+l,t)

The primary centered differencing scheme used in this
model expresses Equation (5) in the following way:

H(i, j,t+l) - H(i, j ,t-l)

2At

•u(i, j,t) [H(i+l,j,t)-H(i-l,j,t) ]

2Ax

v(i,j,t) [H(i,j+l,t)-H(i,j-l,t) ]

2Ay

H(i,j,t) [u(i+l, j ,t)-u(i-l,j ,t) ]

2Ax

H(i,j,t) [v(i, j+l,t)-v(i,j-l,t) ]

2Ay

(6)

24

This scheme is centered in space and time. It can not be
used initially since it requires height fields at two differ-
ent times (t and t-1) in order to predict the height at t+1.
In addition, it can't be used on the grid boundaries since
it would require the input of values beyond the range of the
data field. However, it offers the advantage of centered
differencing and favorable numerical stability.

Forward differencing must be used to predict the height
fields on the first iteration for subsequent input into the
primary centered scheme. Using forward time and centered
space differencing,

H(i, j,t+l)-H(i,j,t;

At

u(i,j,t) [H(i+1, j,t)-H(i-l,j,t) ]

2Ax

v(i,j,t) [H(i,j + l,t)-H(i, j-l,t) ]

2Ay

H(i,j,t) [u(i+l, j,t)-u(i-l,j,t) ]
2Ax

H(i,j,t) [v(i, j+l,t)-v(i, j-l,t) 3
2Ay

(7)

As with all numerical methods, numerical stability is an
important consideration and limits the size of the time step
(At) to be utilized. The Courant-Friedrichs-Levy (CFL)
condition (Courant et_ al. , 1928) for computational stability
(Equation (8)) applies for this model.

V At
Ax

< 1

(8)

25

It controls the size of the time step (At) and grid
spacing (Ax, Ay) such that motion does not cover more than one
grid space between computations. With this model, At must be
less than or equal to 500,000 years. The time step used is
200,000 years.

Boundary conditions are illustrated in Figure 4. As pre-
viously discussed, centered space differencing can not be
used on the perimeters of the grid. Two different types of
boundary conditions are used in this model. Boundaries in the
direction of motion of the moving block (the eastern and southern
boundaries) must be permeable. For this reason, the Upstream
Differencing scheme (Haltiner and Williams , # 1980 , p. 130) is
used on these boundaries. This scheme produces a permeable
boundary where it intersects the moving block and establishes
a rigid boundary condition for the stationary block:

H(i, j,t+l)-H(i, j,t) u(i-l,j,t) [H(i, j , t) -H ( i-1 , j , t) ]

At Ax

H(i-l,j,t) [u(i, j,t)-u(i-l, j,t) ]

Ax

(8)

Fixed boundary conditions are imposed on the northern
and western boundaries. Maintaining the points on these
boundaries at their initial heights introduces errors where
these points lie on the moving portion of the grid. As
topography on these boundaries moves toward the interior
of the grid, a false field is created in their previous

26

positions. Resultant erroneous values are eliminated from
output by moving the northern and western boundaries inward
(for display only) such that the northwest corner of the grid
maintains its position relative to the moving block. This
is illustrated in Figure 9.

The model produces output at 3 million year intervals.
Output is displayed in a three dimensional form as well as a
contoured plan view at each interval (Figures 10-25) . The
three dimensional computer graphics simulate viewing the ter-
rain from a vantage point at high elevation over the Pacific
Ocean looking northeast. Submarine bathymetry is included and
all vertical heights are exaggerated by a factor of 15.

27

. R (tx)

The northern and western
boundaries move inward
such that the northwest
corner of the grid main-
tains its position rel-
ative to a point (r) on
the moving block.

Figure 9. Movement of boundaries for display

28

3AKERSFIELD
MONTEREY

Los Angeles

Figure 10. Topography 21 million years before present

29

Figure 11.

Twenty-one million years before present. On
all contour plots; contour interval = 500 m,
figures in hundreds of meters, bathymetry in
dashed lines, inferred drainage is heavy
dashed line, M, 3, and L represent Monterey,
Bakersfield and Los Angeles respectively

30

Bakersfield

.WTEREY

Los Angeles

Figure 12. Topography 18 million years before present

31

\ b\ \W\ I I II I I I I I I

i ' i \jyyi i i \ \ ,\i i ivm \a \ \ in

Mil jjjj I -f j I EJ I I > I 'I I \ I.1--I : I ! /IM j X.\ -'l-T'f M ^ i >K ! ■' . "■ J ': 'T n -!/'l l : ! i/fl 1 i7

fy 736'. 6A

Figure 13. Eighteen million years before present
contour interval = 500 m, figures in
hundreds of meters

32

Bakersfield Los Angeles

Ignterey

Figure 14. Topography 15 million years before present

33

Figure 15. Fifteen million years before present,
contour interval = 500 m, figures in
hundreds of meters

34

Bakersfield

Los Angeles

WEREY

igure 16. Topography 12 million years before present

Fig

35

_•

-•£

Figure 17. Twelve million years before present, contour
interval = 500 m, figures in hundreds of
meters

36

Bakersfield

Los Angeles

i,yl0NTEREY

iqure 18. Topography 9 million years before present

Figure

37

Figure 19. Nine million years before present, contour
interval = 500 m, figures in hundreds of
meters

38

Monterey

Bakersfield Los Angeles

Figure 20. Topography 6 million years before present

39

" -39.0} "- ;Y" \
' V-53.2/

1 i i ! i-V'i/i ';';i;! i 1-1 r^v-i-.--!-.':i ? i i i.i \^i?!-'<2v\-.\.\n^j ■ i i/i i

Figure 21. Six million years before present, contour
interval = 50 0 m, figures in hundreds
of meters

40

Bakersfield

Los Angeles

Figure 22. Topography 3 million years before present

41

-55.9..

I ' 1 l-l-M-J-'-; IMMt l-r-l Ml:" i-r->-!T I N i'l M > I I I 1 .r 1 M-1

Figure 23. Three million years before present, contour
interval = 500 m, figures in hundreds of
meters

42

Bakersfield
^lonterey i los angeles

Figure

24. Present day topography

43

Figure 25. Present day, contour interval = 500 m,
figures in hundreds of meters

44

III. RESULTS

In viewing the figures depicting model reconstructions
of paleotopography, the design of the model must be kept in
mind. Coarse resolution, as well as the simplifying assump-
tions of the model limit the scope of consideration to large
scale effects.

Figures 10-25 are model outputs generated at three
million year intervals. At each interval there is a three-
dimensional topographic display and a contour map, both
constructed from model results for that particular time.
In all three-dimensional plots, the coastline (based on
present sea level) is represented by a heavy solid line.
The points corresponding to the cities of Monterey, Bakers-
field, and Los Angeles have been annotated for reference.

All contour maps are oriented with north at the top.
Bathymetry appears as dashed contours while all contours >0
appear as solid lines. The San Andreas Fault is represented
as a heavy solid line. Inferred drainage patterns are
indicated by a heavy dashed line. The points corresponding
to the cities of Monterey, Bakersfield, and Los Angeles are
labelled M, B, and L respectively.

Although the model runs backward in time, this discus-
sion will start with model output at 21 million years before
present and proceed foward in time for simplicity. As

45

output for each time interval is discussed, reference will
be made to both figures (3-D and contour) representing
output for that interval .

As expected, topography at 21 million years before
present (Figures 10 and 11) differs greatly from present-
day topography. Monterey Bay lies far to the south-east
of its present position, approximately 100 km west of
Bakersfield. Bakersfield, and points to the east of the
San Andreas Fault, appear much as they are today. The Great
Valley of California extends northwest of Bakersfield and is
bounded on the east by the Sierra Nevada Mountains. The
Mojave Desert lies to the south of the Sierra Nevadas.
Along the fault itself, topography is depressed, particularly
in the area to the southwest of the Mojave Desert. Areas to
the west of the fault appear radically different than they
do today. All topographic features which correlate to today's
topography appear far to the southeast of their present posi-
tions. Although the general shape of the coastline and the
mountain ranges are recognizable, they appear different than
they do today. Monterey and San Francisco Bays are different
in shape and location but are easily recognizable. The Coast
Ranges to the north appear at lower elevations than they do
today but are not greatly different in the area to the south
of Monterey. The Transverse Ranges are somewhat lower and
they are located to the southeast of their present positions
as are the Peninsular Ranges. The position of the Peninsular

4 6

Ranges correlates geographically with the present-day
position of the Gulf of California.

Despite the fact that this reconstruction is the product
of a relatively simple geological model which does not take
into account the effects of erosion, deposition, or displace-
ments along other faults, the large scale features which
appear in these figures are supported by geologic evidence.
The Sierra Nevada Mountains (Curtis et al. , 1958) and the
Colorado Plateau (Eardley, 1962) are features which came
into existence long before Miocene time. Also, the Gulf of
California did not exist at this time (Larson et al . , 1968;
Larson, 1971; Van Andel and Shor, 1964). The depressed
areas along the fault southwest of the Mojave Desert corre-
late geographically with the Salinas, Caliente, San Joacquin,
Ridge, and Soledad basins. The geologic history of these
basins (Norris and Webb, 1976; Blake et al . , 1978) also
shows good chronological correlation with the model
reconstruction.

It is apparent from Figures 10 and 11 that drainage
patterns were much different in early Miocene time. Drainage
from the Colorado Plateau (Colorado River) could not flow
southward into the Gulf of California as it does today.
Rather this drainage flowed westward and entered the ocean
somewhere to the north of the Transverse Ranges. Exactly
where the terminus of this drainage system was located can

47

not be determined from model results alone. However, evidence
previously presented indicates that Monterey Bay was the
terminus of a major land drainage system at this time (Greene,
1977). The inferred drainage is illustrated in Figure 11.
How long this drainage pattern had been in existence prior
to early Miocene time is a question beyond the scope of this
study. However, insights into changes which have occurred
since early Miocene may be obtained by examining model output
at intervals over the last 21 million years.

As expected from the relatively low velocity of motion
along the fault from 21 million years before present to 10
million years before present (Table II), there is little
change in topography over this period (Figures 10-17) . It
appears that the drainage pattern previously established
would have been preserved over this interval. Although there
is evidence to indicate that Monterey Submarine Canyon was
filled and re-excavated during this time (Greene, 1977), this
could have been the result of sea level fluctuations and does
not necessarily imply large scale changes in land drainage
patterns .

From 10-4.5 million years before present, motion along
the fault increased in speed and became slightly less com-
pressional in azimuth (Tables I and II, Figure 6). Topography
at 9 million years before present (Figures 18 and 19) shows
that compression along the fault in the area southwest of the

48

Mojave Desert is closing the depressions in that area. At
the same time, the Peninsular Ranges have been moving north-
westward, leaving a depressed area in the southeastern corner
of the grid. At this point it is not possible to determine
drainage patterns, as illustrated in Figure 19. At 6 million
years before present (Figures 20 and 21) , it is clear that
compressional motion along the fault has uplifted the area
to the southwest of the Mojave Desert to such an extent that
this area no longer serves as a conduit for drainage. Simul-
taneously, the depressed area in the southeast corner has
expanded due to continued movement of the Peninsular Ranges
out of this area. It is not possible to determine that
drainage actually flowed southward at this point since
topography beyond the southeastern corner of the grid is not
presented. However, geologic evidence (Larson et al. , 1968;
Larson, 1971) indicates that the Gulf of California developed
at about this time. For this reason, it is assumed that
drainage from the Colorado Plateau flowed southward much as
it does today.

Velocity of relative motion is slightly higher over the
last 4.5 million years to the present (Table II) and there
is a slight change in the azimuth of direction (Table I and
Figure 5) . However, the trends concerning drainage continue
during this interval as depicted in Figures 22-25. North-
westward displacement of points to the west of the San

49

Andreas Fault, compression in the area of the Transverse
Ranges, and expansion of the Gulf of California continue to
the present and are continuing today.

50

IV. CONCLUSIONS

In arriving at conclusions based on the results of a
numerical model, care must be taken to consider the inherent
weaknesses of the model and to examine available evidence
from other sources for verification. In presenting model
results, only large scale features and general trends were
discussed. It is clear, from the description of the model,
that these are the limits of its credibility. However,
within these limits, model results correlate well with
available evidence and indicate that the Colorado River was
the erosional force involved in the excavation of Monterey
Canyon.

51

LITERATURE CITED

Atwater, T. and Molnar, P., 1973, "Relative Motion of the
Pacific and North American Plates Deduced from Sea-
Floor Spreading in the Atlantic, Indian, and South
Pacific Oceans," Proceedings of the Conference on
Tectonic Problems of the San Andreas Fault System,
Stanford University Publications, Geological Sciences,
Volume XIII.

Blake, M. C. Jr., Campbell, R. H. , Dibblee, T. W. Jr.,

Howell, D. G. , Nilsen, T. H. , Normark, W. R. , Vedder ,
J. C. , Silver, E. A., 1978, "Neogene Basin Formation in
Relation to Plate Tectonic Evolution of San Andreas
Fault System, California," The American Association of
Petroleum Geologists Bulletin, V. 62, No. 3, pp. 344-372,
March.

Clark, J. C. and Rietman, J. D., 1973, United States Depart-
ment of the Interior Geological Survey Prof. Paper 783,
Qligocene Stratigraphy, Tectonics, and Paleogeography
Southwest of the San Andreas Fault, Santa Cruz Mountains
and Gabilan Range, California Coast Ranges.

Courant, R. , K. 0. Friedrichs, and H. Lewy, 1928, "Uber die
partiellen dif f erenzengleichungen der mathematischen
physik," Math. Annalen, 100, 32-74.

Crowell, J. C, 1962, Displacement Along the San Andreas
Fault, California, The Geological Society of America.

Curtis, G. H. , Evernden, J. F., and Lipson, J., 1958, "Age
Determination of Some Granitic Rocks in California by
the Potassium-argon Method," Dept. Nat. Resources Div.
Mines Special Report. 54.

Eardley, A. J., 1962, Structural Geology of North America,
pp. 295-301, Harper and Row.

Greene, H. G. , 1977, United States Department of the Interior
Geological Survey Open-File Report 77-718, Geology of the
Monterey Bay Region.

Haltiner, G. J., and Williams, R. T. , 19 80, Numerical Predic-
tion and Dynamic Meteorology, pp. 130-132, John Wiley and
Sons, Inc.

52

Larson, R. L. , 1971, "Near Bottom Geologic Studies of the
East Pacific Rise Crest," Geol. Soc. Amer . Bull.,
V. 32, pp. 823-842.

Larson, R. L. , Menard, H. W. , and Smith, S. M. , 196 8,

"Gulf of California: A Result of Ocean Floor Spreading
and Transform Faulting," Science, V. 161, pp. 781-734.

Martin, B. D. and Emery, K. 0., 1967, "Geology of Monterey

Canyon, California," The American Association of Petroleum

Geologists Bulletin, V. 51, No. 11, pp. 2281-2304,
November.

Menard, H. W. , 1960, "Possible Pre-Pleistocene Deep-Sea Fans
off Central California," Geological Society of America
Bulletin, V. 71, pp. 1271-1278.

Norris, R. M. and Webb, R. W. , 1976, Geology of California,
pp. 123-134, John Wiley and Sons, Inc.

Silver, E. A., McCulloch, D. S., and Curray, J. R. , "Marine
Geology and Tectonic History of the Central California
Continental Margin." Unpublished.

Starke, G. W. and Howard, A. D., 1968, "Polygenetic Origin
of Monterey Submarine Canyon," Geological Society of
America Bulletin, V. 79, No. 7, pp. 813-826.

van Andel, Tj . H., and Shor, G. G. , eds . , 1964, Marine

Geology of the Gulf of California, Amer. Assoc. Petrol.
Geologists .

53

LIST OF REFERENCES

Bonnin, J., Francheteau, J., and Le Pichon, X., Plate

Tectonics , Elsevier Scientific Publishing Company, 1973.

California Division of Mines and Geology Special Report 118,
San Andreas Fault in Southern California, edited by
J. C. Crowell, 1975.

Dickinson, W. R. and Grantz, A., eds . , Proceedings of Con-
ference on Geologic Problems of San Andreas Fault System,
Stanford University, 1968.

Eardley, A. J. , Structural Geology of North America, Harper
and Row, 1962.

Kovach, R. L. and Nur, A., eds., Proceedings of Conference
on Tectonic Problems of San Andreas Fault System,
Stanford University, 1973.

Norris, R. M. and Webb, R. W. , Geology of California, John
Wiley and Sons, Inc., 1976.

Shepard, F. P., Submarine Topography off the California
Coast, Geological Society of America, 1941.

Shepard, F. P., Submarine Geology, Harper and Row, 1973.

Whitaker, J. H. McD., ed. , Submarine Canyons and Deep-Sea
Fans, Dowden, Hutchinson and Ross, Inc., 1976.

54

INITIAL DISTRIBUTION LIST

No. Copies

1. Defense Technical Information Center 2
Cameron Station

Alexandria, Virginia 22314

2. Library, Code 014 2 2
Naval Postgraduate School

Monterey, CA 9 3940

3. Chairman (Code 6 8 Mr) 1
Department of Oceanography

Naval Postgraduate School
Monterey, CA 9 3940

4. Chairman (Code 6 3 Rd) 1
Department of Meteorology

Naval Postgraduate School
Monterey, CA 939 40

5. Dist. Prof. E. C. Haderlie, Code 68 He 1
Department of Oceanography

Naval Postgraduate School
Monterey, CA 93 94 0

6. LT Robert L. Allen, Jr. 1
118 Moran Circle

Monterey, CA 9 3940

7. Director 1
Naval Oceanography Division

Naval Observatory

34th and Massachusetts Avenue NW

Washington, D. C. 20390

8. Commander 1
Naval Oceanography Command

NSTL Station

Bay St. Louis, MS 39522

9. Commanding Officer 1
Naval Oceanographic Office

NSTL Station

Bay St. Louis, MS 39522

55

10. Commanding Officer

Fleet Numerical Oceanography Center
Monterey, CA 9 394 0

11. Commanding Officer

Naval Ocean Research and Development

Activity
NSTL Station
Bay St. Louis, MS 39522

12. Commanding Officer

Naval Environmental Prediction

Research Facility
Monterey, CA 9 3940

13. Chairman, Oceanography Department
U. S. Naval Academy
Annapolis, MD 214 0 2

14. Chief of Naval Research
800 N. Quincy Street
Arlington, VA 22217

15. Office of Naval Research (Code 420)
Naval Ocean Research and

Development Activity
NSTL Station
Bay St. Louis, MS 39522

16. Scientific Liaison Office
Office of Naval Research

Scripps Institution of Oceanography
La Jolla, CA 92037

17. Library

Scripps Institution of Oceanography
La Jolla, CA 92037

18. Library

Department of Oceanography
University of Washington
Seattle, WA 98105

19 . Library
CICESE

P. 0. Box 4803

San Ysidro, CA 92073

20. Librarian

Hopkins Marine Station
Pacific Grove, CA 93950

56

21. Library

School of Oceanography
Oregon State University
Corvallis, OR 97331

22. Commander

Oceanographic Systems Pacific

Box 139 0

Pearl Harbor, HI 96860

23. Chief, Ocean Services Division
National Oceanic and Atmospheric

Administration
8060 Thirteenth Street
Silver Springs, MD 20910

24. Dr. H. G. Greene

U. S. Geological Survey

Branch of Pacific-Arctic Marine Geology

34 5 Middlefield Road, MS-99

Menlo Park, CA 94 0 25

25. Dr. F. P. Shepard

Scripps Institution of Oceanography
La Jolla, CA 92037

26. Dr. R. F. Dill

Scripps Institution of Oceanography
La Jolla, CA 92037

27. Prof. R. T. Williams, Code 6 3Wu
Meteorology Department

Naval Postgraduate School
Monterey, CA 9 3940

28. Mrs. Betty W. Allen
2453-D Amsterdam Circle
Marietta, GA 300 6 7

29. Capt. Alan Shaffer
Meteorology Department, Code 63
Naval Postgraduate School
Monterey, CA 9 394 0

30. Mr. J. R. MacFarlane
1819 Applewood Court
Orlando, FL 32808

31. Librarian

Moss Landing Marine Laboratory
Moss Landing, CA 95039

57

c.l

Thesis

A37955 Allen

_ i The impact of

tectonic activity in - in
the development of f
Monterey Submarine e
Canyon.

Thesis

A37955

Allen

c.l

The impact of

tectonic activity in

the development of

Monterey Submarine

Canyon.