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Sedimentology of the northern half of the Laguna Salada, Baja California

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Sedimentology of the northern half of the Laguna Salada, Baja California

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Content SEDIMENTOLOGY OP THE NORTHERN HALF
I *
OP THE LAGUNA SALADA, BAJA CALIFORNIA
by-
C h a r le s M. C u r t is
1 1 1
A T h e s is P r e s e n te d to th e
FACULTY OP THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In P a r t i a l F u l f i l l m e n t o f th e
R eq u irem en ts f o r th e Degree
MASTER OF SCIENCE
(G eology)
A ugu st, 1966
UMI Number: EP58549
All rights reserved
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UMI EP58549
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UNIVERSITY O F SO U T H E R N CALIFO R NIA
TH E GRADUATE SC H O O L
UNIVERSITY PARK
LOS A N G ELE S, C A LIF O R N IA 9 0 0 0 7
This thesis, written by
CHAR:LES.M..CIJRTIS................................
under the direction of h..X3..Thesis Committee,
and approved by all its members, has been pre
sented to and accepted by the Dean of The
Graduate School, in partial fulfillment of the
requirements for the degree of
M a ste r o f S c ie n c e (Geology)
Dean
................................
HESIS COMMITTEE
CONTENTS
PAGE
ABSTRACT . . . . ............................................................................. 1
INTRODUCTION ....................................................................................... 2
P urpose .............................................................. • • • • • 2
L o c a tio n and a c c e s s i b i l i t y • • • . ..................... 2
P r e v io u s i n v e s t i g a t i o n .................................................... 5
C lim ate ....................................................................................... 5
C o l l e c t i o n o f sam ples .................................................... 9
Methods o f a n a l y s i s ......................................................... 12
A c k n o w l e d g m e n t s ............................................. • • • • 15
PHYSIOGRAPHIC AND GEOLOGIC SETTING ............................... 16
G e n era l p h y sio g ra p h y . . . . . ............................... 16
R e g io n a l geology .............................................................. 17
G e n e r a l ............................................. 17
R e g io n a l s t r u c t u r e ......................................................... 19
L i t h o l o g y ............................................................................. 19
SEDIMENTOLOGY.................................................................................. 26
T e x t u r e ....................................................................................... 26
G e n e r a l .................................................................................. 26
Sedim ent ty p e • • • • 29
C o lo r ........................................................................ 48
Mean d i a m e t e r ................................................................... 53
S ta n d a rd d e v i a t i o n • ............................................... 60
Skewness • ........................................................................ 74
i i i
PAGE
K u r t o s i s .................................................................................. 97
C hem ical d a t a ........................................................................ 118
C arb o n ate c o n te n t ......................................................... 118
Carbon c o n te n t ................................................................... 119
C oarse f r a c t i o n a n a l y s i s ............................................... 124-
G en era l .................................................................................. 124
L ig h t m i n e r a l s ................................................................... 125
Heavy m i n e r a l s .................................................................. 131
Clay m i n e r a l o g y ................................................................... 134
G e n e r a l .................................................................................. 134
R e s u l t s .................................................................................. 134
D i s c u s s i o n ............................................................................. 135
MI CEO FAUNA............................................................................................. 138
SUMMARY AND CONCLUSIONS .................................................... 147
REFERENCES............................................................................................. 151
APPENDICES............................................................................................. 155
A ppendix I .................................................................................. 156
Appendix I I ............................................. 166
ILLUSTRATIONS
FIGURE PAGE
1 , L o c a tio n and to p o g r a p h ic c o n to u r map 3
2 a , b , c . I s o p l e t h d iag ra m s o f mean a n n u a l
te m p e r a t u r e , r a i n f a l l , and
r u n o f f ................................................................... 7
3 . Sample l o c a t i o n s and i d e n t i f i c a t i o n • 10
4. F a u l t map o f th e I m p e r i a l and
C o a c h e lla V a lle y s .......................................... 20
5. S t r a t i g r a p h i c r e l a t i o n s h i p s f o r
I m p e r i a l V a lle y ............................................... 23
6 a . T e x t u r a l c o m p o s itio n d iag ra m s f o r
s e d im e n ts from Laguna S a la d a . . . 30
6b. T e x t u r a l c o m p o s itio n diagram f o r
se d im e n ts o f th e A - l a y e r ..................... 32
6 c. T e x t u r a l c o m p o s itio n d iag ram f o r
se d im e n ts o f t h e C - l a y e r ..................... 34
6d. T e x t u r a l c o m p o s itio n d iagram f o r
s e d im e n ts o f th e E - l a y e r ..................... 36
7 a . R e l a t i o n s h i p o f sed im en t ty p e f o r
t h e A ^ - l a y e r .................................................... 39
7b. R e l a t i o n s h i p o f se d im e n t ty p e f o r
th e A2- l a y e r .................................................... 41
7 c . R e l a t i o n s h i p o f se d im e n t ty p e f o r
th e C - l a y e r ......................................................... 44
V
.GE
46
49
51
54
56
58
61
63
65
68
70
R e l a t i o n s h i p o f se d im e n t ty p e f o r
t h e E - l a y e r ...............................................
C o n to u rs o f L ayer lfAff sand
p e rc e n ta g e s ...............................................
C o nto urs o f L ay e r ,fA1 1 s i l t
p e r c e n ta g e s ...............................................
C on tou rs o f th e mean d ia m e te r s f o r
L ay er "A” ....................................................
C on tou rs o f th e mean d ia m e te rs f o r
L ay er 1 1 CM ....................................................
C o n to u rs o f th e mean d ia m e te r s f o r
L ayer ,fEH ....................................................
S ta n d a rd d e v i a t i o n c o n to u r s f o r
L ay e r "A*1 ....................................................
S ta n d a rd d e v i a t i o n c o n to u r s f o r
L ay er M Cn ....................................................
S ta n d a rd d e v i a t i o n c o n to u r s f o r
L ay e r "E” ....................................................
G r a p h ic a l method o f s o r t i n g v a lu e s
f o r L ay er ”A, f ..........................................
G r a p h ic a l method o f s o r t i n g v a lu e s
f o r L a y e r ftCM .........................................
G r a p h ic a l method o f s o r t i n g v a lu e s
f o r L ay er 1 1 0 M .........................................
v i
.GE
75
77
79
84
86
88
91
93
95
98
C ontour p l o t o f slcewness v a lu e s
f o r l a y e r ttAw ..........................................
C ontour p l o t o f skew ness v a lu e s
f o r L ay e r "Ct f .........................................
C o ntou r p l o t o f skew ness v a lu e s
f o r L ay e r f,E " ..........................................
H isto g ra m s o f th e c la y e y s i l t
s e d im e n ts in L a y e r "A1 * • • • .
H isto g ra m s o f th e c la y e y s i l t
se d im e n ts in L ay e r f,Cf1 . . . .
H isto g ra m s o f th e c la y e y s i l t
se d im e n ts in L ay e r f,EM . . . .
Skewness v e r s u s s ta n d a r d d e v i a t i o n
f o r L ay e r U AU ..........................................
Skewness v e r s u s s ta n d a r d d e v i a t i o n
f o r L ay er 1 1 CH .........................................
Skewness v e r s u s s ta n d a r d d e v i a t i o n
f o r L a y e r H E, f ..........................
Skewness v e r s u s mean d ia m e te r f o r
L ay er ,fAl f ....................................................
Skewness v e r s u s mean d ia m e te r f o r
L ay er tfCf f ....................................................
Skewness v e r s u s mean d ia m e te r f o r
L ay e r "E*1 ...............................................
FIGURE
!
17 a.
!
17b.
i
|
i 17 c.
i
i 1 8 a.
18b.
18 c.
t 1 9 a , b , c
i
!
I 20.
j 2 1.
2 2 .
j 23.
24a.
24b.
24c •
Skewness v e r s u s k u r t o s i s f o r
L ay er “A” .........................................................
Skewness v e r s u s k u r t o s i s f o r
L ay e r M CM .........................................................
Skewness v e r s u s k u r t o s i s f o r
L ay e r M E" .........................................................
K u r t o s i s c o n to u rs f o r L ay e r "A*1 . .
K u r t o s i s c o n to u r s f o r L ay e r "C" . •
K u r t o s i s c o n to u r s f o r L ay e r H Eff . .
P e r c e n ta g e s o f c a lc iu m c a r b o n a t e ,
o r g a n ic c a rb o n , and t o t a l carbo n
Mean d ia m e te r v e r s u s c a lc iu m
c a r b o n a te .........................................................
Q u a r t z / f e l d s p a r r a t i o s ..........................
P l a g i o c l a s e / o r t h o c l a s e r a t i o s • . .
Heavy m in e r a l w e ig h t p e r c e n t s * .
Humber o f f o r a m i n i f e r a p e r
5 gm
sam ple f o r L ay e r w A,f
Humber o f f o r a m i n i f e r a p e r
5
gm
sam ple f o r L ay e r ,,C,f
Humber o f f o r a m i n i f e r a p e r
5
gm
sam ple f o r L ay e r ,,E,f • i
PAGE I
t
i
]
105
107 |
109
112
114 '
116
120 ;
I
122
127
129
132
140
142
i
144 '
TABLES
TABLE
I.
II.
P e r c e n ta g e o f n e g a t i v e and p o s i t i v e
skew ness v a lu e s f o r c la y e y s i l t s and
s a n d - s i l t - c l a y s . . . . . . . . . .
Average q u a r t z and f e l d s p a r p e rc e n ta g e
v a lu e s f o r th e m a r g in a l and c e n t e r
t r a v e r s e s . . . . . . ...............................
PAGE
82
126
ABSTRACT
i
! The Laguna S a la d a o c c u p ie s a s t r u c t u r a l tr o u g h
betw een th e S i e r r a J u a r e z and th e S i e r r a de l o s Cucapas
'M ountains in B a ja C a l i f o r n i a , R e ce n t g r a v i t y d a ta su g
g e s t t h a t t h e b a s in c o n ta in s a p p ro x im a te ly 1 9 ,0 0 0 f e e t
o f se d im e n t w hich i s n e a r l y e q u a l to th e t h i c k n e s s e s
g iv e n f o r th e C o lo rad o D e lta and I m p e r i a l V a lle y a r e a s .
I f t h e p o s t u l a t i o n s a r e c o r r e c t , th e n th e Laguna S a la d a
o c c u p ie s a b a s in whose s e d im e n ta ry h i s t o r y p a r a l l e l s
t h a t o f t h e I m p e r i a l V a lle y . P e r i o d i c in u n d a t i o n s by
:the m arine w a t e r s o f th e G u lf o f C a l i f o r n i a a re p a r t o f
jth at h i s t o r y . The d e l t a o f th e C olorado R iv e r now form s
a b a r r i e r to t h e m arin e w a te r s o f th e G u lf and on ly o c -
i
I
'c a s io n a l f l o o d i n g s from th e C olorado R iv e r a r e r e p o r t e d .
The Laguna S a la d a , how ever, w i t h i t s c lo s e p r o x im ity to
I
^the G u lf and s u b s t a n t i a l l y lo w e r d i v i d e , c o n tin u e s to
r e c e i v e i n t e r m i t t e n t s u p p l i e s o f m arin e a s w e ll as f r e s h
w a t e r s .
S edim ents from th e Laguna S a la d a , :* in term s o f
se d im e n t t y p e , mean s i z e , s o r t i n g , sk ew ness, and c o l o r ,
c a n n o t be d i f f e r e n t i a t e d from th e p la y a se d im e n ts d e s
c r i b e d in th e l i t e r a t u r e . C o n d itio n s n o t n o rm a lly p r e
s e n t in p la y a s a r e i n d i c a t e d by th e c o n s i s t e n t v a r i a t i o n s
w ith d e p th w ith th e above p a ra m e te rs a s w e ll as th e
a b u n d an t m arin e f a u n a .
INTRODUCTION
P urpo se
Laguna S a la d a was chosen as a t h e s i s a r e a in o r d e r
to e x te n d th e knowledge and a v a i l a b l e d a t a f o r th e
C olorado D e lta se d im e n t and r e l a t e d f e a t u r e s * An o p p o r
t u n i t y was p ro v id e d to s tu d y a c lo s e d b a s in in an a r i d
r e g io n in w hich m arin e se d im e n ts a r e d e p o s i te d a l t e r n a t e l y
w ith t e r r e s t r i a l s e d im e n ts . T his may prove u s e f u l in th e
i n t e r p r e t a t i o n o f s i m i l a r e n v iro n m e n ts in th e g e o lo g ic
r e c o r d .
L o c a tio n and A c c e s s i b i l i t y
Laguna S a la d a i s l o c a t e d in th e n o r th w e s te r n
p o r t i o n o f B a ja C a l i f o r n i a betw een 3B° 21* and 32° 00*
N o rth l a t i t u d e and 115° 32* and 115° 46* West l o n g i t u d e .
Bounded on th e w e st by th e S i e r r a J u a r e z M ountains and on
th e e a s t by th e Cucapa M o u n ta in s, th e Laguna S a la d a
o c c u p ie s a n o r t h w e s t - t r e n d i n g e lo n g a te tr o u g h a p p r o x i
m a te ly 60 m ile s lo n g w ith a maximum w id th betw een 15 and
20 m i l e s . Mexican F e d e r a l Highways 2 and 5 e x te n d w e st
and s o u th from M e x ic a li and p ro v id e r e l a t i v e l y e asy a c c e s s
to th e la g o o n a l p l a i n ( F i g . 1 ) .
2
F ig u re 1 . L o c a tio n map show ing th e Laguna
S a la d a b a s i n and th e a c c e s s Mexican
F e d e r a l Highways 2 and 5 from
M e x ic a li*
115 30 115 45
UNITED*™1 "
M EXICO
12 30’ —
\
32 15
LOCATION MAP
OF THE
LAGUNA SALADA, BAJA CALIFORNIA
C O N T O U R S (M E T E R S)
S C A L E
M IL E S
5
j P re v io u s I n v e s t i g a t i o n
|
| There h a s been l i t t l e s i g n i f i c a n t work a c c o m p lish e d
I in th e Laguna S a la d a a r e a . The e a r l i e s t r e p o r t s o f
| a c t i v i t y a r e r e l a t e d by McDougal (190?) who in c l u d e s
! many i n t e r e s t i n g a c c o u n ts c o n c e rn in g t r a v e l l e r s and
i
j sm u g g lers who had o c c a s io n to c r o s s th e a r e a d u r in g th e
! d ry p e r i o d s . A lso c i t e d by McDougal a r e r e p o r t s o f e x -
i
! t e n s i v e f i l l i n g s o f th e b a s i n in 1884, 1893, and 1907.
In 1913 two Mexican g e o l o g i s t s , Y. S. B o n i l l a s and P.
U rb in a , gave a c o n c is e g e o g r a p h i c a l d e s c r i p t i o n o f th e
j Laguna S a la d a . The p h y sio g ra p h y was p r e s e n t e d a g a in by
I B e a l (1 9 4 8 ). A d e s c r i p t i o n o f th e s u r f a c e s o f p la y a s
! w hich i n c lu d e d some d a t a on Laguna S a la d a was p r e s e n t e d
I in th e d i s s e r t a t i o n o f S to n e (1 9 5 6 ). One o f th e most
i
| r e c e n t a r t i c l e s to a p p e a r in th e l i t e r a t u r e i s a d i s c u s -
i s io n o f th e g e o p h y s ic a l a s p e c t s by B i e h l e r , Kovach, and
A lle n (1 9 6 5 ).
i
C lim ate
T em p erature and r a i n f a l l d a t a f o r t h e stu d y a r e a
i
1 were o b ta in e d from U n ite d S t a t e s G e o lo g ic a l Survey P r o
f e s s i o n a l P a p e r 486-B by H ely and Peck (1964) w hich
! c o v e rs th e lo w e r p o r t i o n s o f t h e C olorado R iv e r and th e
, S a lto n S ea. Laguna S a la d a l i e s o u t s i d e th e d ra in a g e b a s i n
j
' d i s c u s s e d in th e r e p o r t b u t t h e c o n to u r s in some c a s e s
6
! c r o s s i n t o th e s tu d y a r e a and a llo w t h e a u t h o r to
f o r m u la te c o n c lu s io n s a s to t h e mean a n n u a l te m p e r a t u r e ,
j r a i n f a l l , and r u n o f f .
|
^ Prom th e d a ta p r e s e n t e d in P i g s . 2a, b, and c ,
Laguna S a la d a conform s to th e Bwh c l a s s i f i c a t i o n o f
Koppen (H a u rw itz and A u s ti n , 1944) w hich i s a t r o p i c a l
i
t , .
j and s u b - t r o p i c a l d e s e r t (w) w ith a mean a n n u a l te m p e r a tu re
j g r e a t e r th a n 6 4 .4 ° P (h) and where e v a p o r a t i o n e x ceed s
| p r e c i p i t a t i o n (B ). The mean a n n u a l te m p e r a tu r e i s w e ll
| d e f in e d in th e s tu d y a r e a by t h e 72° P c o n to u r and i s su b -
• s t a n t i a l l y o v e r th e 6 4 .4 ° P f i g u r e n e c e s s a r y f o r th e M h ,f
j
i p o r t i o n o f th e c l a s s i f i c a t i o n ( P ig . 2 a ) . S p e c i f i c d a ta
|
| on th e maximum and minimum t e m p e r a t u r e s i s n o t a v a i l a b l e
j f o r th e Laguna S a la d a a r e a , how ever, the te m p e r a t u r e s
»
| r e c o r d e d in Yuma, A riz o n a and I n d i o , C a l i f o r n i a , do n o t
i
: a p p e a r to be s i g n i f i c a n t l y d i f f e r e n t th a n th e te m p e ra
t u r e s e n c o u n te re d by th e a u th o r d u r in g th e sam ple c o l -
i
i
; l e c t i o n s . B oth r e c o r d i n g s t a t i o n s r e v e a l a lm o st i d e n t i -
. c a l d a i l y , m o n th ly , and a n n u a l te m p e r a tu r e r a n g e s o v e r a
: 29 y e a r p e r i o d e x te n d in g from 1931 to I9 6 0 (H ely and Peck,
1 9 6 4 ). The maximum t e m p e r a t u r e s , r e c o r d e d d u r in g th e
j
'm o n th s o f J u ly and A u g u st, a r e w e l l above 120° P a t b o th
, s t a t i o n s . In c o n t r a s t , th e minimum te m p e r a t u r e s d u r in g
th e same p e r io d a r e betw een 50° P and 60° P. The m onthly
, a v e ra g e s f o r th e s e two ,,h o t ,, m onths exceed 90° P w ith
a v e ra g e d a i l y te m p e r a tu r e r a n g e s from 78° P to 110° P.
F ig u r e s 2a, b , c . I s o p l e t h d iag ram s o f (a )
mean a n n u a l te m p e r a t u r e ,
(b) r a i n f a l l , and (c) r u n
o f f •
CONTOUR DIAGRAMS
OF
MEAN ANNUAL
TEMPERATURE (a)
(°F )
RAIN FALL (b)
(INCHES)
RUNOFF (c)
(INCHES)
116
116 115 30’
MEXICALLI
115 30 116
MODIFIED
AFTER
HELY AND PECK (1964)
115 30’
0.02
\ \
LAGUNA SALADA
LAGUNA SALADA
c
9
Ja n u a ry i s th e c o l d e s t month w ith a r e c o r d e d minimum o f
12° P a t I n d io and 19° P a t Yuma. The a v e ra g e m onthly
te m p e r a tu r e f o r J a n u a ry i s 55° P w ith d a i l y ra n g e s from
38° P to 70° P.
P r e c i s e f i g u r e s f o r th e mean a n n u a l r a i n f a l l a re
more d i f f i c u l t to i n t e r p r e t i n P ig . 2b a s a v a r i e t y o f
c o n to u r s a p p ro a c h th e a r e a . The c o n to u r s , how ever, a re
c o n ta in e d w i t h i n a t h r e e - t o t e n - i n c h r a i n f a l l ra n g e w hich
a d e q u a te ly c l a s s i f i e s th e a r e a a s a d e s e r t (w )." R u n o ff
c o n to u r s ( P ig . 2c) i n d i c a t e t h a t l e s s th a n 0 .5 in c h e s
w i l l d r a i n i n t o th e Laguna S a la d a b a s i n .
C o l l e c t i o n o f Sam ples
W ith th e use o f a B runton com pass, o d o m eter, l i n e
o f s i g h t b e a r i n g s , and an a r b i t r a r y g r i d sy s te m , t h e
sam ples were o b ta in e d in th e m anner shown in P i g . 3 . A
sa m p lin g l i n e was e s t a b l i s h e d e v e ry 3 m il e s and a lo n g
each l i n e th e sam ples w ere c o l l e c t e d 2 m il e s a p a r t u n t i l
th e edge o f t h e l a g o o n a l p l a i n was r e a c h e d . The l a c k o f
an a p p r o p r i a t e b a se map made i t n e c e s s a r y to c r o s s -
r e f e r e n c e e a c h sam ple s t a t i o n by l o c a t i n g th e l i n e - o f -
s i g h t b e a r i n g on s e l e c t e d p eak s in b o th th e S i e r r a J u a r e z
and Cucapa M o u n ta in s. Seven com p lete t r a v e r s e s and one
p o i n t on l i n e e i g h t w ere a c c o m p lish e d by t h i s m ethod.
Each sam ple s t a t i o n was c o re d to a d e p th o f 5 f e e t
u s i n g a 7 f o o t Iwan a u g e r . The sam ples w ere s p l i t e v ery
F ig u re 3. Diagram i l l u s t r a t i n g th e sam ple
l o c a t i o n s and number sy ste m .
11
2L2
2L1 •
3L2
2R1 3L1
2R2
3R1
3R2*
4L2
4L1
5L2
5L1
4R2
4R3
6L2
5R1
6L1 5R2
5R3
7L2 5R4
6R1
7L1
6R2
6R3
7R1
7R2
7R3
SAMPLE LOCATIONS
LAGUNA SALADA
12
f o o t and th e n p u t i n t o s e p a r a t e h a l f - p i n t i c e cream co n
t a i n e r s . In i n s t a n c e s where a n o t i c e a b l e change o c c u r r e d
w i t h i n th e o n e - f o o t i n t e r v a l s , an a p p r o p r i a t e s p l i t was
made and p la c e d i n t o a s e p a r a t e c o n t a i n e r .
At th e o u t s e t o f t h i s p r o j e c t t h e main o b j e c t i v e
was to sam ple th e e n t i r e l a g o o n a l p l a i n , how ever, th e
d i f f i c u l t i e s o f t r a v e l , tim e , and a c c e s s i b i l i t y r e s u l t e d
i n th e d e c i s i o n to c o v e r th e n o r t h e r n h a l f o n ly .
Methods o f A n a ly s is
S ta n d a r d s e d i m e n t o l o g i c a l p r o c e d u r e s w ere u sed in
th e d e t e r m i n a t i o n o f t h e t e x t u r e o f th e s e d im e n ts .
P i p e t t e a n a l y s e s o f th e l e s s th a n 0 .0 6 2 mm s i z e m a t e r i a l ,
a s p r e s e n t e d in Krumbein and P e t t i j o h n (1 9 3 8 ), and th e u se ;
o f th e 3 - i n c h d ia m e te r T y le r s c r e e n s f o r t h e sand s i z e
m a t e r i a l s p ro v id e d th e b u lk o f th e d a t a . D uring th e
a n a l y s e s th e a u t h o r so u g h t to sav e tim e by a p p ly in g a
p i p e t t e te c h n iq u e w hich had prov en u s e f u l w ith o c e a n ic
s e d im e n ts (K. S. R o d o lfo , D epartm en t o f G eology, U .S .C .,
p e r s o n a l c o m m u n ic a tio n ). The t e c h n i q u e , w hich used o n ly
a 500 ml s u s p e n s io n , a llo w e d th e a n a l y s e s to be co m pleted
w i t h i n a 18 h o u r p e r i o d and w i t h a t i m e - s a v i n g o f 6 h o u rs
p e r a n a l y s i s . F l o c c u l a t i o n o c c u r r e d d u r in g a l l o f th e
a t t e m p t s a t p r e p a r i n g th e sa m p le s . The prob lem , a t f i r s t ,
a p p e a re d to c e n t e r aro u n d th e w a sh in g o f th e h ig h s a l t
c o n te n t from th e s e d im e n ts ; t h e r e f o r e , th e number o f w ash
13
i n g s was i n c r e a s e d th r o u g h th e u se o f a c e n t r i f u g e . I t
became a p p a r e n t t h a t a n o t h e r f a c t o r was a t f a u l t when th e
sam p les w ere p r e p a r e d a s u s u a l e x c e p t t h a t th e d i s p e r s i n g
a g e n t had been i n t e n t i o n a l l y o m it t e d . In a p p ly in g th e
new te c h n iq u e th e d i s p e r s i n g a g e n t was changed from th e
more commonly u sed c a lg o n to m a r a s p e r s e . The r e s u l t on
t h e sa m p le s, p r e p a r e d w i t h o u t a d i s p e r s i n g a g e n t , was
c o m p le te ly p o s i t i v e , t h a t i s , no f l o c c u l a t i o n . Sub
s e q u e n t a d d i t i o n o f th e m a ra s p e rs e a g a in cau se d f l o c c u l a
t i o n and proved t h a t th e d i s p e r s i n g a g e n t was o p e r a t i n g in
r e v e r s e . Due to th e f a c t t h a t th e Laguna S a la d a s e d i
m ents c o n ta in an u n u s u a l ly h i g h c o n c e n t r a t i o n o f s u l f a t e
s a l t s , th e a u th o r assum es t h a t th e s u l f a t e s w ere th e
c au se o f th e d i f f i c u l t i e s .
The c a r b o n a t e , o r g a n ic c a rb o n , and t o t a l carbon
a n a l y s e s were a l l d e te rm in e d th ro u g h th e u se o f th e Leco
Carbon A n a ly z e r ( A lla n Hancock S t a f f , 1 9 5 3 ). R e p r e s e n t a
t i v e sam ples were ta k e n from th e f,AH and M EH l a y e r s o f
l i n e f o u r . D u p l i c a t e , and in some c a s e s t r i p l i c a t e ,
a n a l y s e s were p erfo rm ed on a l l sam ples to p ro v id e con
f i r m a t i o n o f th e r e s u l t s .
A H o re lc o x - r a y d i f f r a c t o m e t e r w ith c o p p e r tu b e
r a d i a t i o n was used to d e te rm in e th e c la y m in e ra lo g y . The
t e c h n iq u e s a p p l i e d t o th e sam p les were o b t a i n e d from
B r i n d le y (1 9 6 1 ).
I t was n e c e s s a r y to o b t a i n th o r o u g h ly washed
i 14
i
| sam ples by c e n t r i f u g a t i o n and d e c a n t a t i o n b e c a u se o f th e
h ig h s a l t c o n te n t p r e s e n t i n th e s a m p le s . A s u s p e n s io n
was th e n p r e p a re d by v ig o r o u s s h a k in g and th e n a llo w e d to
! s e t t l e f o r 10 h o u r s . The l e s s th a n 2 m icro n s i z e
i
j f r a c t i o n was a p p l i e d to a g l a s s s l i d e f o r x - r a y a n a l y s i s
l
j and exposed to a s e r i e s o f f o u r p r o c e s s e s w hich th e
! a u t h o r presum ed w ere a d e q u a te to d i f f e r e n t i a t e betw een th e
o o o o
j 7A, 10A, 14a , and 17A p e ak s c o n s id e r e d in t h i s s t u d y .
| The p r o c e s s e s p ro v id e d d i f f r a c t o g r a m s from sam ples w hich
i
| w ere (1) u n t r e a t e d , (2) exposed to an e th e le y n e g l y c o l
b a t h f o r one h o u r a t 60° C, (3) h e a te d to 250° C f o r 12
h o u r s , and (4) h e a t e d t o 550° 0 f o r 1 h o u r .
S t a i n i n g t e c h n i q u e s w ere employed to d i f f e r e n t i a t e
i o r t h o c l a s e and p l a g i o c l a s e f e l d s p a r s . Sodium c o b a l t i n i -
t r i t e was u se d to s t a i n th e o r t h o c l a s e f e l d s p a r s y e llo w
and p o ta s s iu m r h o d i z o n a t e to s t a i n th e p l a g i o c l a s e f e l d -
| s p a r s r e d ( B a ile y and S te v e n s , I 9 6 0 ) . The te c h n iq u e was
!
j u s e f u l ; n e v e r t h e l e s s , t h e a u t h o r found t h a t th e l e n g t h o f
i
■ tim e t h a t th e p o ta s s iu m r h o d i z o n a te rem ain ed on th e s l i d e
. was c r i t i c a l . I f l e f t on f o r too lo n g a p e r i o d , th e
! o r t h o c l a s e was r e s t a i n e d to a r e d d i s h o ran g e w hich was
i
1 d i f f i c u l t to d i s t i n g u i s h from th e p l a g i o c l a s e s t a i n and
i f th e p o ta s s iu m a c i d was removed to o e a r l y , s t a i n i n g o f
| t h e p l a g i o c l a s e was i n c o m p le te . Ten se co n d s was c o n s i d e r
ed an a d e q u a te l e n g t h o f tim e f o r th e sa m p le s.
S e p a r a t i o n o f th e l i g h t and heavy m in e r a l s was
15
p e rfo rm ed by u t i l i z i n g th e s t a n d a r d t e c h n iq u e s in Krum-
b e in and P e t t i j o h n (1938) and A lla n Hancock S t a f f (1 9 5 8 ).
Acknowledgments
The w r i t e r w is h e s to acknow ledge th e h e l p o f D rs.
P. S. G o r s l i n e , R. H. M erriam , and J . W. R e i t h f o r t h e i r
a s s i s t a n c e and a d v ic e in th e l a b o r a t o r y and f i e l d work
a s w e l l a s f o r t h e i r h e l p in p r e p a r i n g t h i s m a n u s c r i p t.
A p p r e c i a t i o n i s due a l s o to D r. 0 . L. Bandy f o r th e
i d e n t i f i c a t i o n o f th e f o r a m i n i f e r a . S p e c i a l th a n k s and
c o n s i d e r a t i o n a r e g iv e n to W. M. C h i ld e r s o f E l C e n tro ,
C a l i f o r n i a f o r h i s t im e ly h e lp and k in d n e s s a t a tim e
when t h e c o n tin u a n c e o f th e sa m p lin g program was j e o p a r d i z
e d . The w r i t e r i s a l s o in d e b te d to h i s b r o t h e r - i n - l a w ,
Samuel D. O r i z a , f o r th e e x c e l l e n t d r a f t i n g o f th e
f i g u r e s i n t h i s r e p o r t .
PHYSIOGRAPHIC AND GEOLOGIC SETTING ;
G e n e ra l P h y s io g ra p h y I
i
The C o lo rad o D e s e r t, one o f th e e i g h t n a t u r a l ;
i
p r o v in c e s in s o u th e r n C a l i f o r n i a ( J a h n s , 1954)> i s a low
la n d bounded on th e w e st by th e P e n i n s u l a r Range p r o v i n c e ,
t h e T r a n s v e r s e Ranges to th e n o r t h , and th e s o u t h e a s t !
c o r n e r o f th e t r i a n g u l a r Mojave D e s e r t p r o v in c e on th e !
e a s t •
!
E l e v a t i o n s v a ry c o n s i d e r a b l y w i t h i n th e b oun d in g
f
p r o v i n c e s . The h i g h e s t and s t e e p e s t m o u n ta in s a r e in th e ;
T r a n s v e r s e Ranges and th e n o r t h e r n p o r t i o n s o f th e P e n in - i
r
s u l a r Ranges w here e l e v a t i o n s exceed 1 0 ,0 0 0 f e e t ; f o r ;
exam p le, San G orgonio M ountain (1 1 ,5 0 2 f e e t ) and San ;
J a c i n t o Peak (1 0 ,8 3 1 f e e t ) . N e ar th e i n t e r n a t i o n a l b o r d e r
e l e v a t i o n s r a r e l y exceed 6000 f e e t . The e a s t e r n b o r d e r
c o n t a i n s num erous s m a l l e r r a n g e s w hich i n c l u d e e l e v a t i o n s
above 8000 f e e t in th e n o r t h e a s t and a p p ro x im a te ly 3000
f e e t n e a r th e b o r d e r . W ith in th e S i e r r a de l o s C ucapas,
th e i s o l a t e d ra n g e w hich c o n s t i t u t e s th e e a s t e r n b o und ary
f o r th e Laguna S a la d a , e l e v a t i o n s r i s e to 3500 f e e t
( B e a l, 1 9 4 8 ).
W ith in th e s t r u c t u r a l e lo n g a te d e p r e s s i o n o f th e
I m p e r i a l and C o a c h e lla V a lle y s l i e s a b e l o w - s e a - l e v e l
b e l t 85 m il e s lo n g and up to 30 m il e s w id e . The S a lto n
16
17
Sea o c c u p ie s a 2 0 -m ile lo n g tr o u g h w i t h i n th e d e e p e s t
p o r t i o n s o f t h e d e p r e s s i o n and h a s a r e c o r d e d d e p th o f
278 f e e t below s e a l e v e l (H ely and P eck , 1 9 6 4 ). S e p a r a t
i n g th e S a l to n Sea tr o u g h from t h e G u lf o f C a l i f o r n i a i s
th e 1 0 0 -m ile wide d e l t a o f th e C olorad o R iv e r w hich i s
o n ly 35 f e e t above s e a l e v e l a t i t s lo w e s t p o i n t . R e c e n t
l y , a few c e n t u r i e s a g o , th e f r e s h w a t e r s o f a n c i e n t Lake
C a h u l l l a f i l l e d th e S a lto n t r o u g h to d e p th s 40 t o 50 f e e t
above s e a l e v e l . T h is s u g g e s ts t h a t th e d e l t a d i v id e was
e ro d e d by th e o v e rf lo w from t h i s la k e (L o n g w ell, 1 9 5 4 ),
o r p o s s i b l y lo w e re d t e c t o n i c a l l y .
The Laguna S a la d a d e p r e s s io n a l s o r e c e i v e s e x t e n
s i v e a c c u m u la tio n s o f f r e s h w a t e r d u r in g th e f lo o d
s e a s o n s . One f i l l i n g o f th e d e p r e s s io n from t h e Rio H ardy,
a t r i b u t a r y o f t h e C o lo rad o R i v e r , was w i t n e s s e d by
McDougal (1 9 0 7 ). Prom a v a i l a b l e d a t a , th e lo w e s t p o r t i o n
! o f th e b a s i n i s 20 f e e t below s e a l e v e l . The d i v i d e ,
h ow ever, i s l e s s th a n 20 f e e t above s e a l e v e l and a c c o u n ts
f o r th e r e l a t i v e e a s e w ith w hich t h e t i d e and f l o o d w a te r s
r e a c h th e d e p r e s s i o n .
R e g io n a l Geology
G e n e ra l
The C olorad o D e l ta r e g i o n , i n c l u d i n g th e I m p e r i a l
and C o a c h e lla V a l l e y s , o c c u p ie s a s t r u c t u r a l t r o u g h e x -
18
! t e n d i n g a p p r o x im a te ly 180 m il e s beyond th e p r e s e n t h ead o f
th e G u lf o f C a l i f o r n i a * The P e n i n s u l a r R ange, composed o f
C re ta c e o u s b a t h o l i t h i c ro c k s o f g a b b r o ic to g r a n i t i c
■ i
I c o m p o s itio n w i t h a s s o c i a t e d m e ta m o rp h ic s , form s a w e s te r n
i
I bou ndary to th e s t r u c t u r a l t r o u g h w h ile more d i v e r s e p r e -
C enozoic m e ta m o rp h ic s, g r a n i t i c s , and s u b o r d i n a t e
T e r t i a r y v o l c a n i c s co m p rise th e e a s t e r n b o u n d a ry .
S e d im e n ta tio n d u r in g th e C en o zo ic r e s u l t e d in an
a c c u m u la tio n o f c o a r s e and f i n e - g r a i n e d m a t e r i a l s e x c e e d -
i
in g 2 0 ,0 0 0 f e e t in th e d e e p e s t p o r t i o n s o f th e tr o u g h
( B i e h l e r , K ovach, and A l l e n , 1 9 6 4 ), The c o a rs e and f i n e
|s e d i m e n t s a r e tim e e q u i v a l e n t d e p o s i t s r e s u l t i n g from th e
i
! i n t e r f i n g e r i n g o f f a n g l o m e r a te s , c o n g lo m e r a te s , b r e c c i a s ,
i
jand a r k o s i c s a n d s to n e s d e r iv e d from t h e s u rr o u n d in g
|m o u n ta in o u s m asses w i t h c l a y s , s i l t s , and f i n e sand
|im p o r te d p r i m a r i l y by t h e C o lo rad o R iv e r (M erriam and
i
jBandy, 1 9 6 5 ).
I
| The Laguna S a la d a t r o u g h , s e p a r a t e d from th e d e l t a
!by th e i s o l a t e d p r e - T e r t i a r y c r y s t a l l i n e mass o f th e
i
S i e r r a de l o s C ucapas, h a s u n d erg o n e a s i m i l a r s e d i
m e n ta ry h i s t o r y . The g r a v i t y s t u d i e s o f B i e h l e r , Kovach,
and A lle n (1964) i n d i c a t e t h a t th e b a s in o f t h e Laguna
S a la d a may c o n ta in a s much a s 1 9 ,0 0 0 f e e t o f se d im e n t
w hich a lm o s t e q u a ls th e t h i c k n e s s e s p o s t u l a t e d f o r th e
C olorado D e l ta tr o u g h and i n f e r s t h a t th e C enozoic h i s t o r y
i
o f th e two tr o u g h s sh o u ld e x h i b i t e s s e n t i a l l y p a r a l l e l
19
s e c t i o n s . T h is would in c l u d e a M iocene i n u n d a t i o n o f th e
Laguna S a la d a w h ic h , a c c o r d i n g to th e p a le o g e o g r a p h ic maps
o f Durham and A l l i s o n ( i 9 6 0 ) , d id n o t o c c u r u n t i l t h e
P l i o c e n e .
R e g io n a l S t r u c t u r e
R e g io n a l s t r u c t u r e o f t h e se d im e n t f i l l e d t r o u g h s ,
s o u th o f th e T r a n s v e r s e R anges and n o r t h o f th e G u lf o f
C a l i f o r n i a , i s c o n t r o l l e d by th e San A ndreas sy ste m o f
f a u l t s . The p r i n c i p a l n o r th w e s t t r e n d i n g f a u l t s in th e
a r e a , p r e s e n t e d in P i g . 4 , have been docum ented as e x
h i b i t i n g a p red o m in a n t r i g h t l a t e r a l s t r i k e - s l i p d i s p l a c e
ment ( B i e h l e r , Kovach, and A l l e n , 1 9 6 4 ). R e cen t g r a v i t y
d a t a s u p p o r t th e c o n c lu s io n t h a t th e Laguna S a la d a f a u l t ,
w h ich bounds th e w e s te r n m arg in o f th e S i e r r a de l o s
C ucap as, i s a c o n t i n u a t i o n o f t h e E l s i n o r e f a u l t .
L lt h o l o g y
S e d im e n ta tio n i n t o th e main t r o u g h began d u r in g
t h e e a r l y p o r t i o n s o f th e C eno zo ic E ra (Durham and A l l i
so n , I 9 6 0 ) . E x te n s iv e d e p o s i t i o n , how ever, d id n o t b e g in
u n t i l th e M iocene p e r i o d when th e S p l i t M ountain Forma
t i o n , a c o a r s e b a s a l c o n g lo m e r a te , was d e p o s i te d u n c o n -
fo rm ab ly upon o l d e r c r y s t a l l i n e r o c k s (D ib b le e , 1 9 5 4 ).
The f o r m a tio n e x h i b i t s t h i c k n e s s e s w hich v a r y from 0 to a
maximum o f 2700 f e e t a t i t s ty p e l o c a l i t y . C onform ably
F ig u r e 4 F a u l t map o f th e I m p e r i a l and
C o a c h e lla T a l le y s and t h e i r r e l a t i o n
s h i p s to Laguna S a l a d a .
21
SAN GORGON 10 MTN.
11,502’
116 30' 116 115 30' 115
H34,
PINTO BASIN
SAN JACINTO PEAK
10,831 *
PALM
SPRINGS
•33 30’
33 30'— |
TRUCKHAVEN
NILAND
WARN El?
SPRINGS
GLAM IS BRAWLEY
a
33—
CALEXICO
-«5cs-'
MEXICALLI
YUMA
k - 3 2 30’ 32 30’-
SAN LUIS
FAULT MAP OF THE SALTON TROUGH
EL MAYOR
MILES
KILOMETERS
PRE-TERTIARY CRYSTALLINE ROCK
MODIFIED AFTER
BIEHLER, KOVACH, AND ALLEN (1964)
GULF
OF
CALIFORNIA
116 115 30’
22
o v e r l y i n g th e S p l i t M ountain F o rm a tio n i s a s e r i e s o f
a n d e s i t e l a v a s , b r e c c i a s , and t u f f s from 9 to 700 f e e t
t h i c k t h a t make up th e A lv e rso n A n d e s ite ( F i g , 5 ) . The
I m p e r i a l F o rm a tio n (W oodring, 1931) i s c o n c o rd a n t w i t h th e
a n d e s i t e and c o n s i s t s o f l i g h t g ra y c l a y s t o n e s , a r k o s i c
s a n d s t o n e s , and c a l c a r e o u s o y s t e r r e e f s a t t a i n i n g t h i c k
n e s s e s from 0 to 3800 f e e t (D ib b le e , 1 9 5 4 )• A L a te
M iocene age i s i n d i c a t e d f o r some p o r t i o n s o f th e I m p e r i a l
F o rm a tio n by t h e p r e s e n c e o f a d i v e r s i f i e d m arin e f a u n a .
The s e c t i o n c o n ti n u e s as th e I m p e r i a l F o rm atio n
g r a d e s upward i n t o t h e Palm S p r in g F o rm a tio n and c o n s i s t s
o f f i n e s a n d , s i l t , c l a y , and o c c a s i o n a l t u f f s . A P l e i s
to c e n e age h a s been s u g g e s te d due t o th e c h a r a c t e r o f th e
a b u n d a n t v e r t e b r a t e f o s s i l s found th r o u g h o u t th e form a
t i o n (D r. Theodore Downs, Los A n g eles County Museum,
p e r s o n a l c o m m u n ic a tio n ).
The c o a r s e m a r g in a l f a c i e s o f th e I m p e r i a l and Palm
S p r in g F o r m a tio n s , t h e Canebrake C o n g lo m e ra te , a t t a i n s a
maximum t h i c k n e s s o f 9000 f e e t and r e p r e s e n t s th e m ost
e x t e n s i v e c o a r s e d e p o s i t in th e r e g i o n . G r a n i t i c and m e ta -
m orphic d e b r i s a re th e m ost im p o r t a n t c o n s t i t u e n t s in th e
c o n g lo m e r a te .
A l a c u s t r i n e s e c t i o n , composed o f l i g h t g ray c l a y
s t o n e s i n te r b e d d e d w i t h f i n e - g r a i n e d s a n d s t o n e s , o v e r l i e s
th e Palm S p r in g F o rm atio n and C anebrake C onglom erate and
was named by T a r b e t and Holman (1944) a s t h e B o rreg o
F ig u re 5* S t r a t i g r a p h i c r e l a t i o n s h i p s f o r th e
I m p e r i a l V a lle y r e g i o n w hich r e v e a l
th e r e l a t i o n s h i p betw een th e c o a r s e
m a r g in a l f a c i e s and t h e i r f i n e
g r a i n e d e q u i v a l e n t s .
GENERALIZED STRATIGRAPHIC RELATIONSHIPS
FOR
THE IMPERIAL VALLEY REGION
MODIFIED AFTER
(MERRIAM AND BANDY, 1965)
SYSTEM COMPOSITE SECTION
SERIES
ALLUVIUM
BRAWLEY
FORMATION
OCOTILLO
CGL.
u u
BORREGO
Q C
LU
FORMATION
L JU
PALM SPRING
o*
Q .
O f
LU
FORMATION
z
o
LU
IMPERIAL LU
Z
LU O'
CD
LU
Z FORMATION
CL
ALVERSON ANDESITE
Q C
LU
LU
SPLIT MOUNTAIN
z
LU
U -
FORMATION
LU
ANZA FORMATION
25
F o rm a tio n . The f o r m a tio n h a s a maximum t h i c k n e s s o f 6000
i
f e e t a t i t s ty p e l o c a l i t y . O v e r ly in g th e l a k e beds o f
i
I th e B o rreg o F o rm a tio n a r e th e O c o t i l l o C o nglom erate and
i t s a s s o c i a t e d l a c u s t r i n e f a c i e s , th e B raw ley F o rm atio n
w hich c o n t a i n s a p p r o x im a te ly 2000 f e e t o f l i g h t g ra y
)
c l a y s t o n e s and b u f f s a n d s to n e i n t e r b e d s .
R e c e n t d e l t a s e d im e n ts a r e p re d o m in a n tly f i n e sa n d s
! and s i l t s w i t h an i n c r e a s i n g c la y c o n t e n t a s one a p p ro a c h e s
| th e G u lf o f C a l i f o r n i a .
| SEDIMENTOLOGY
i T e x tu re
G e n e ra l
The c o l l e c t e d sam p les were i d e n t i f i e d a c c o r d i n g to
the g r i d sy stem i l l u s t r a t e d in P i g . 3 . A num ber d e s i g n a
t i o n t o i d e n t i f y th e sam ple l i n e w i t h a l e t t e r "L1 * ( l e f t )
and “R" ( r i g h t ) to l o c a t e th e p o s i t i o n o f th e sam ple
r e l a t i v e t o th e c e n t e r t r a v e r s e p ro v id e d th e a u t h o r w i t h
i
a c o n v e n ie n t r e f e r e n c e to th e sam ple l o c a t i o n s . Each
j
1 - f o o t i n t e r v a l was I d e n t i f i e d w i t h a l e t t e r b e g in n in g
w i t h “A1 1 f o r th e 0 to 1 f o o t l e v e l and e n d in g w ith "E1 1
Ifor th e 4 to 5 f o o t l e v e l . I f th e sam ple was s p l i t w i t h
in th e 1 - f o o t i n t e r v a l s , th e n t h e a p p r o p r i a t e i n t e r v a l ,
i
in i n c h e s , was added to th e sam ple num ber, f o r exam p le,
th e s u r f a c e sam ple 5L2A was d iv id e d i n t o two s e p a r a t e
s a m p le s, one c o n t a i n i n g th e f i r s t 5 in c h e s o f th e 1 - f o o t
i
i n t e r v a l and th e o t h e r th e r e m a in in g 7 i n c h e s ; t h e r e f o r e ,
th e sam ple i d e n t i f i c a t i o n s would be 5D2A05 and 5D2A512.
The b u lk o f th e sam p les e x h i b i t e d a c o l o r ran g e
I
c o n fin e d to l i g h t s h a d e s o f brown w i t h th e e x c e p tio n o f a
i
l i g h t g re e n p a tc h a lo n g th e e a s t e r n m a rg in . S a l t c o n t e n t ,
in g e n e r a l , i s h i g h w i t h g re e n c la y s r e q u i r i n g th e g r e a t e r
num ber o f w a sh in g s to remove th e s a l t s .
S ed im en t d a ta p r e s e n t e d i n term s o f w e ig h t
26
p e r c e n t a g e s , mean d i a m e t e r , s t a n d a r d d e v i a t i o n , skew n ess,
and k u r t o s i s w are o b t a i n e d by program m ing t h e “method o f
i
! moments1 1 f o r th e A utom ath 1800 computer* The m ethod i s
1
b a se d upon a c o m p u ta tio n a l a p p ro a c h i n w hich th e t o t a l
l sam ple a f f e c t s t h e f i n a l r e s u l t s a s opposed to th e more
1
commonly u se d g r a p h i c a l m ethods w hich u t i l i z e s p e c i f i c
1
j p o r t i o n s o f th e d i s t r i b u t i o n c u rv e , t h e r e b y n e g l e c t i n g
j l a r g e seg m en ts o f th e t o t a l sample*
t
I
I C a l c u l a t i o n s o f th e moments b e g in by d e te r m in in g
j th e p h i a r i t h m e t i c mean, w hich in r e a l i t y i s th e c e n t e r
j o f g r a v i t y o f th e fre q u e n c y d i s t r i b u t i o n curve* The
; c e n t e r o f g r a v i t y o f any sy stem can be c a l c u l a t e d by
■
summing th e p r o d u c t s o f th e w e ig h ts o f a body o r cu rv e a t
I some p a r t i c u l a r d i s t a n c e from a p o i n t o f o r i g i n and th e n
i
d i v i d i n g by th e t o t a l w e ig h t o f th e o b j e c t o r c u rv e . In
t h e c a se o f th e fre q u e n c y c u rv e t h i s i s a c c o m p lish e d by
j m u l t i p l y i n g th e i n d i v i d u a l w e ig h t p e r c e n t a g e s o f e a c h
i
: s i z e c l a s s by th e m i d - p o i n t s o f t h e i r r e s p e c t i v e p h i c l a s s
1
| i n t e r v a l s and d i v i d i n g th e sums o f t h e s e p r o d u c ts by th e
i
. t o t a l w e ig h t p e r c e n t a g e .
j A f t e r c a l c u l a t i n g th e c e n t e r o f g r a v i t y o r p h i
a r i t h m e t i c mean o f th e fr e q u e n c y d i s t r i b u t i o n c u rv e , th e
1 n e x t p r o c e s s i s to d e te rm in e t h e moment o f i n e r t i a ( I )
a b o u t t h e a x i s o r c e n t e r o f g r a v i t y o f th e sy ste m .
Moments o f i n e r t i a a r e o b t a i n e d by m u l t i p l y i n g e ac h mass
1
(w e ig h t p e r c e n t a g e ) by th e s q u a re o f i t s d i s t a n c e from
28
t h e a x i s , t h a t i s , th e s q u a re o f t h e d e v i a t i o n o f th e p h i
(0) m id - p o i n t from th e p h i a r i t h m e t i c mean ( c e n t e r o f
g r a v i t y ) .
In o r d e r t o d e te rm in e t h e s o r t i n g o r t h e s t a n d a r d
d e v i a t i o n o f t h e f r e q u e n c y d i s t r i b u t i o n c u rv e , i t i s
n e c e s s a r y to f i n d th e r a d i a l d i s t a n c e from th e p h i a r i t h
m e tic mean ( c e n t e r o f g r a v i t y ) a t w hich th e mass o f th e
c u rv e c o u ld be c o n c e n t r a t e d w i t h o u t a l t e r i n g th e moment
o f i n e r t i a o f th e body a b o u t t h a t a x i s . T h is d i s t a n c e i s
r e f e r r e d to a s th e r a d i u s o f g y r a t i o n . The moment o f
i n e r t i a o f t h i s new p o i n t i n v o lv e s th e t o t a l mass (M) and
2
a d i s t a n c e (K) and e q u a l s M K , By d e f i n i t i o n th e moment
o f i n e r t i a h a s n o t been changed and t h e r e f o r e e q u a ls th e
a c t u a l moment o f i n e r t i a ( I ) . E q u a tin g th e two f u n c t i o n s
g y r a t i o n o r t h e s t a n d a r d d e v i a t i o n o f th e f re q u e n c y d i s
t r i b u t i o n c u rv e .
I t i s p o s s i b l e to r e l a t e th e above e q u a tio n to th e
more commonly u sed s t a n d a r d d e v i a t i o n e q u a t io n (P o lk ,
1964) by s u b s t i t u t i n g th e a p p r o p r i a t e sy m b o ls.
r e s u l t s in th e e q u a t io n w hich i s th e r a d i u s o f
K = r a d i u s o f g y r a t i o n = = s t a n d a r d d e v i a t i o n
W = w e ig h t p e r c e n t a g e s = M = mass
0 = p h i
K0 = p h i (0) a r i t h m e t i c mean
D = p h i (0) m id - p o in t
29
I = 2 w (M 0 - D)^ = moment o f i n e r t i a
‘t h e r e f o r e K = \ / £ = R , = / 2 W (M(2f-D)2
V M u 0 v J--------------------- 1 -----
llw
The r e m a in in g two moments, skew ness and k u r t o s i s ,
a r e c a l c u l a t e d by c o n t i n u i n g t h e p r o c e s s e s d e v e lo p e d h e re
to p r o g r e s s i v e l y h i g h e r po w ers. T here a r e no p h y s i c a l
a n a lo g u e s f o r skew ness and k u r t o s i s and i t i s d i f f i c u l t to
te x p r e s s them in sim p le term s (Krumbein and P e t t i j o h n , 1938)*
\
| S ed im ent Type
i
W ith th e u se o f a t r i a n g u l a r d iag ram p ro p o se d by
-Shepard (1 9 5 4 ), t h e s e d im e n t t y p e s w i t h i n l a y e r s UAU,
”C", and 1 1 E" w ere d e te r m in e d . The d iagram was ch o sen b e
c a u se o f i t s w ide a c c e p ta n c e i n th e l i t e r a t u r e and i t s
u s e f u l n e s s in th e a r e a s t u d i e d ( P i g . 6 a , b , c , d ) .
The b u lk o f th e 58 s u r f a c e sam ples a r e c o n ta in e d
w i t h i n t h r e e t e x t u r a l g r o u p s , s i l t y c l a y , c la y e y s i l t ,
and s a n d - s i l t - c l a y ( P i g . 6 b ) . Only f o u r sam ple l o c a t i o n s
a r e r e p r e s e n t e d in th e seven e x c e p ti o n s due t o th e f a c t
t h a t t h r e e o f them w ere s p l i t w i t h i n th e 1 - f o o t i n t e r v a l .
Two o f th e f o u r sa m p le s (5R4A and 7L2A), w hich would
t e c h n i c a l l y be c l a s s i f i e d a s sandy c l a y s , a r e n o t s i g n i
f i c a n t l y d i f f e r e n t from th e s a n d - s i l t - c l a y sa m p le s . The
two s a n d s , 5L2A and 6L2A, a r e d i f f e r e n t and p e rh a p s owe
t h e i r o r i g i n t o two l a r g e a l l u v i a l f a n s a d j a c e n t to t h e s e
s t a t i o n s . C o n s id e r a b le d i f f i c u l t y was e x p e r ie n c e d d u r i n g
F ig u re 6 a . T e x t u r a l c o m p o s itio n d iag ra m s used
to i d e n t i f y se d im e n ts from Laguna
S a l a d a .
31
TEXTURAL C O M P O S I T I O N D IA G R A M
MODIFIED FROM SHEPARD (1954)
BASED ON
SAND (2-0.62 mm),
SILT (0.62-0.004 mm),
CLAY (0.004 m m )
CLAY
CLAY
SILTY SANDY
CLAY CLAY
SAND-
CLAYEY CLAYEY SILT-
SILT SAND CLAY
SANDY SILTY
SILT SAND
SILT SAND
F ig u r e 6b T e x t u r a l c o m p o s itio n d iag ra m f o r
s e d im e n ts o f th e A - l a y e r .
33
CLAY
A - LAYER
F ig u re 6 c , T e x t u r a l c o m p o s itio n diag ram f o r
s e d im e n ts o f th e C - l a y e r .
35
CLAY
C - LAYER
F ig u r e 6d T e x t u r a l c o m p o s itio n d iag ra m f o r
s e d im e n ts o f th e E - la y e r *
37
CLAY
E - LAYER
I t h e c o l l e c t i o n o f 5L2 due t o t h e w et c o n d i t i o n s s u r r o u n d -
i
in g th e a r e a .
i
A se d im e n t map was p r e p a r e d t o i l l u s t r a t e th e d i s -
i
; t r i b u t i o n o f t h e se d im e n t t y p e s a c r o s s t h e s u r f a c e o f t h e
i
! la g o o n ( F i g . 7a). The s i l t y c l a y s form a l a r g e c o n tin u o u s
; a r e a bounded by c o a r s e r m a t e r i a l s c l o s e r to t h e m a rg in s
i
S o f t h e b a s i n . The c o a r s e r m a t e r i a l s , s a n d - s i l t - c l a y and
i
; s a n d , o c c u r p r e d o m in a n tly a lo n g th e e a s t e r n m arg in w h e re -
| a s t h e w e s te r n m arg in i s c h a r a c t e r i z e d by c la y e y s i l t s .
i
T h is g e n e r a l p a t t e r n o f sa n d s on th e e a s t e r n s i d e and
s i l t s on th e w e s te r n s i d e i s c l e a r l y i l l u s t r a t e d i n F i g s .
i
: 8 and 9 w hich a r e c o n to u r maps o f sand and s i l t p e r c e n t -
I a g e s f o r th e s u r f a c e l a y e r M AH •
| The i n c r e a s e i n th e p e r c e n ta g e o f sand a t 5R4 a p -
I p e a r s t o be an e x c e p t i o n . An e x a m in a tio n o f th e c o n to u r s
i
i
; in F i g . 1, n e v e r t h e l e s s , d i s c l o s e s t h a t th e sam ple
i
j o c c u p ie s a p o s i t i o n below th e c l o s e s t and s t e e p e s t p o r t i o n
i
j o f t h e S i e r r a J u a r e z f r o n t . To th e n o r t h and s o u th o f
!
i 5R4 an i n c r e a s e in th e s i l t p e r c e n t a g e s o c c u r s w hich can
i
1 be a t t r i b u t e d t o t h e p r e s e n c e o f san d d u n e s. The dune
m a t e r i a l s a r e p resu m ab ly d e r iv e d from t h e s u r r o u n d in g
b a s i n f l a t .
S in c e many o f th e s u r f a c e sam p les w ere s p l i t w i t h
i n th e 1 - f o o t i n t e r v a l s , a s e d im e n t map i s p r e s e n t e d
i w hich i n d i c a t e s th e chan g es j u s t below th e s u r f a c e ( F i g .
t
7b). In e v e ry c ase t h e change was from a c o a r s e r t o a
F ig u r e 7 a . R e l a t i o n s h i p o f s e d im e n t ty p e
w i t h i n th e b o u n d a r i e s o f th e
sa m p lin g a r e a f o r th e A ^ - l a y e r .
SAND (S)
40
SAND-SILT-CLAY (SMC)
CLAYEY SILT (CM)
SILTY CLAY (MC)
SEOmEHT TYPE
A1 - LAYER
F ig u r e 7 b . R e l a t i o n s h i p o f s e d im e n t ty p e
w i t h i n th e b o u n d a r ie s o f th e
sa m p lin g a r e a f o r t h e A2 - l a y e r .
42
SAND (S)
SAND-SILT-CLAY (SMC)
CLAYEY SILT (CM)
MC
:SMC:
SILTY CLAY (MC)
:SMC:
:SMC:
MC
SMC
SEDIMENT TYPE
LAYER
! f i n e r m a t e r i a l w i t h a r e s u l t a n t i n c r e a s e in t h e s i l t y
c la y and c la y e y s i l t a r e a s . L a y e rs ffClf and f,Ef 1 ( F i g s .
i
7 c , d ) , c o n t i n u i n g t h e d e c r e a s i n g sand c o n te n t t r e n d , have
j l e d th e a u t h o r to t h e c o n c lu s io n t h a t t h e sand p r o d u c ts
*
1
a r e t h e r e s u l t o f r e l a t i v e l y r e c e n t a c t i v i t y . D rainage
from th e m a r g in a l a r e a s p r o v id e s t h e h u lk o f t h e s a n d -
s i z e m a t e r i a l s ; t h e r e f o r e , a p r o b a b le r e a s o n f o r th e
I im p e tu s f o r an i n c r e a s e i n d r a i n a g e c o n c e iv a b ly r e s u l t e d
from movements a lo n g th e b o r d e r i n g f a u l t z o n e s . S u p p o r t
in g t h i s c o n c lu s io n a r e th e r e p o r t s o f e a r th q u a k e sh o ck s
o f m a g n itu d e s g r e a t e r th a n 6 .0 in h i s t o r i c tim e s a lo n g
b o th m a rg in s ( B i e h l e r , K ovach, and A l l e n , 1964) and th e
i
j t r a c e a b l e s c a r p o f t h e Laguna S a la d a f a u l t on t h e e a s t e r n
| m arg in ( F i g . 4 ) . The s c a r p i s c l o s e l y a s s o c i a t e d w i t h
| sam ple l o c a t i o n s 5L2A and 6L2A w hich c o n t a i n th e a b u n d an t
sand p e r c e n t a g e s .
i
| Com paring th e ch an ges i n s e d im e n t ty p e w i t h d e p th
J
; r e v e a l s t h a t th e sand on th e e a s t and c la y e y s i l t s on th e
| w e st a r e r e l a t i v e l y s t a b l e a r e a s b etw een s h i f t i n g se d im e n t
p a t t e r n s a c r o s s th e b a s i n s u r f a c e . The c o r r e l a t i o n in
l a y e r M A,f betw een t h e main t o p o g r a p h i c d e p r e s s i o n and th e
i
! to n g u e - s h a p e d s a n d - s i l t - c l a y a r e a in t h e n o r t h e a s t c o r n e r
! p r o v id e s a p o s s i b l e c lu e t o some o f th e ch an g e s in s e d i
m ent t y p e . When f l o o d w a t e r s r e a c h th e s o u t h e r n e x tr e m i t y
| o f th e Cucapas (E l Mayor) th e y a re d i r e c t e d n o rth w a rd
th r o u g h a sy ste m o f c h a n n e ls 12 to 15 f e e t deep ( F i g . 1)
F ig u r e 7 c , R e l a t i o n s h i p o f s e d im e n t ty p e
w i t h i n th e b o u n d a r i e s o f th e
sa m p lin g a r e a f o r th e C - l a y e r .
SEDIMENT TYPE
C - LAYER
8667
99999
F ig u re 7d. R e l a t i o n s h i p o f s e d im e n t ty p e
w i t h i n th e b o u n d a rie s o f th e
s a m p lin g a r e a f o r th e E - l a y e r .
N ote th e d e c r e a s e in t h e c o a r s e r
s e d im e n ts .
SAND-SILT-CLAY (SMC)
MC
SILTY CLAY (MC)
CLAYEY SILT (CM)
'CM
.CM,
MC
.CM
MC
SEDIMENT TYPE
E - LAYER
; 48 ,
i
and t h u s would e v e n t u a l l y r e a c h t h e d e p r e s s e d a r e a in th e
I
! n o r t h e a s t c o r n e r . Assuming t h a t th e sand m a t e r i a l s a r e i
i
d e r i v e d from th e m a r g in a l a r e a s and d i s t r i b u t e d a c r o s s
th e s u r f a c e o f t h e b a s i n by wind a c t i o n , th e n t h e m ost ■
p e r s i s t e n t w et a r e a s sh o u ld p ro v id e a p o t e n t i a l t r a p to
I p r e v e n t th e rem o v al o f m a t e r i a l s . The o t h e r ch an g es w i t h .
i
| d e p th in v o lv e th e g r a d u a l d is a p p e a r a n c e o f th e sand p r o - :
i
; d u c ts so t h a t o n ly two m a jo r se d im e n t t y p e s , c la y e y s i l t s >
land s i l t y c l a y s , rem a in ( P i g s . 6b, c ) .
i
C o lo r j
G reen and brown a r e th e two b a s i c c o l o r t y p e s f o r j
t h e s e d im e n ts in t h e L aguna S a la d a b a s i n . The g re e n c l a y s
l
; a r e a lo n g th e e a s t e r n m arg in and o c c u r in e v e ry sam ple |
j w i t h an W L" d e s i g n a t i o n . Sample l i n e s 6 and 7 have g re e n \
j c l a y s in sam p les 6A, 7A, and 7R1A08 a s w e l l . The g re e n
! c o l o r e x te n d s from 6 to 36 i n c h e s below t h e s u r f a c e and in
i
j e v e ry c a s e g ra d e s i n t o t h e brown c la y v a r i e t i e s . A cco rd -
( in g to S to n e (1 9 5 6 ), g re e n c la y s a r e n o t common and were
e n c o u n te r e d o n ly w i t h i n th e s u b s u r f a c e se d im e n t o f m o is t
■ p l a y a s . The g re e n c o l o r , t h e r e f o r e , t r a n s g r e s s e s se d im e n t
type* p la y a t y p e , and c la y m in e r a lo g y . A s s o c i a t i o n o f th e
c o l o r s w i t h th e d e p r e s s i o n s a lo n g th e e a s t e r n m arg in and
: th e f a c t t h a t th e y r e q u i r e d a g r e a t e r num ber o f w a sh in g s
to remove t h e i r s a l t c o n te n t h a s l e d t h e a u t h o r to con
c lu d e t h a t th e p o n d in g o f f l o o d and t i d e w a t e r s w i t h th e
F ig u re 8 . C o n to u r d iag ra m o f th e sand p e r c e n t
a g e s i l l u s t r a t i n g th e p redo m inance
o f t h e h ig h v a lu e s a lo n g t h e e a s t e r n
m a rg in .
50
SAND WEIGHT PERCENT
A - LAYER
CONTOUR INT. 10%
F ig u re 9 C o n to u r d iag ram o f th e s i l t p e r c e n t
a g e s show ing t h a t t h e h i g h v a lu e s
o c c u r n e a r t h e w e s te r n m a rg in .
Co
o
to
'O
SILT WEIGHT PERCENT
A - LAYER
CONTOUR INT 5%
s u b s e q u e n t e v a p o r a t i o n and c o n c e n t r a t i o n s o f th e s a l t s
from th e t r a p p e d w a t e r s h a s p ro d u ce d th e c o l o r d i f
f e r e n c e s .
O th e r e v id e n c e s u p p o r t s th e c o n c e p t o f a s h i f t in
e m p h asis from a p o s s i b l e s a l i n e l a c u s t r i n e o r m arin e
e n v iro n m e n t to t h e s u b a e r i a l c o n d i t i o n s o f th e p r e s e n t .
T h is i s c o n s i s t e n t w ith t h e g r a d u a l a p p e a ra n c e o f th e
g re e n c la y v a r i e t i e s a s one f o llo w s t h e c o l o r change from
l a y e r "E" to l a y e r "A1 1 w i t h i n th e a p p r o p r i a t e c o r e s .
Mean D ia m e te r
C o n to u rs o f th e d i s t r i b u t i o n o f mean d i a m e t e r s f o r
th e r e s p e c t i v e l a y e r s ^A*’, ,fC,f, and ,fEf < a r e shown in
F i g s . 1 0 a , b , c . The c o n to u r i n t e r v a l i s i n p h i ( 0 ) u n i t s
t h e r e f o r e , t h e s m a l l e r th e p h i u n i t t h e c o a r s e r th e
m a t e r i a l . I t h a s a l r e a d y been shown t h a t th e m a rg in s c o n
t a i n t h e c o a r s e r m a t e r i a l s , t h e r e f o r e , i t i s no s u r p r i s e
t h a t th e c o n to u r s o f mean d i a m e t e r s r e f l e c t t h e same con
d i t i o n . An i n t e r e s t i n g p o i n t i s th e ra n g e o f mean
d i a m e t e r s . The s u r f a c e l a y e r h a s a ra n g e o f 3 0 t o 9 0
w hich d e c r e a s e s to 5 0 to 9 0 in t h e 2 - t o - 3 - f o o t d e p th
i n t e r v a l and 6 0 t o 9 0 in t h e 4 - t o - 5 - f o o t d e p th i n t e r v a l .
S in c e th e s u r f a c e s p r e a d i s u n d o u b te d ly i n f l u e n c e d by th e
a l l u v i a l a r e a s , one can assume a d e c r e a s i n g i n f l u e n c e o f
t h e s e a r e a s w ith d e p th . The o v e r a l l u n i f o r m i t y o f th e
c o n to u r s in th e M Elf l a y e r ( F i g . 10c) s u p p o r t s t h e c o n c e p t
F ig u r e 1 0 a . C o n to u rs o f th e mean d i a m e t e r s f o r
l a y e r 1 1 AM •
55
MEAN DIAMETER
CONTOURS
A-LAYER
CONTOUR INT. 1 PHI (0)
F ig u r e 10b, C o n to u rs o f th e mean d i a m e t e r s
f o r l a y e r 1 1 C” ,
MEAN DIAMETER
CONTOURS
C - LAYER
CONTOUR INT. 1 PHI (0)
F ig u r e 1 0 c . C o n to u rs o f t h e mean d i a m e t e r s
f o r l a y e r H EH. The ra n g e o f mean
d i a m e t e r s h a s become i n c r e a s i n g l y
s m a l l e r w i t h d e p th r e s u l t i n g in a
sm ooth s u r f a c e f o r l a y e r " E " .
59
MEAN DIAMETER
CONTOURS
E - LAYER
CONTOUR INT. 1 PHI (0)
60
i i
| o f a l e s s d i f f e r e n t i a t e d s e d im e n ta r y e n v iro n m e n t w hich may
i
be th e r e s u l t o f an e x t e n s i v e m a rin e f l o o d i n g o f t h e j
b a s i n . !
i
i S ta n d a r d D e v i a t io n j
i
i
] S ta n d a r d d e v i a t i o n o r s o r t i n g m ea su re s th e a v e ra g e
i j
! s p r e a d o f t h e f r e q u e n c y d i s t r i b u t i o n c u rv e and i s e x -
| i
p r e s s e d in te rm s o f p h i (0) v a l u e s . I t i s r e p r e s e n t e d in
I
i
t h e c o n to u r d ia g ra m s P i g s . 1 1 a , b, c . J u s t a s th e s e d i - '
! !
ment ty p e i s f i n e r - g r a i n e d and l e s s d i f f e r e n t i a t e d w ith
d e p th , th e s o r t i n g v a l u e s r e f l e c t b e t t e r s o r t i n g and more [
I
i u n i f o r m i t y w ith d e p th . Though th e s p r e a d o f s o r t i n g j
! . I
j v a lu e s f o r l a y e r s "A", "C11, and "E" rem a in e s s e n t i a l l y !
| c o n s t a n t , i . e . , 1 .9 0 t o 3 .9 0 9 1 .6 0 t o 3 .9 0 9 and 1 . 7 0 \
j to 3 .7 0 9 r e s p e c t i v e l y , th e a v e r a g e v a l u e s , 3 . 0 0, 2 . 4 0 ;
t
! and 2 .3 0 r e f l e c t th e g r a d u a l d is a p p e a r a n c e o f t h e s a n d -
s i l t - c l a y s e d i m e n ts . In th e u p p e r o r "A" l a y e r 50 p e r
! c e n t o f t h e sam p les a r e s a n d - s i l t - c l a y and a c c o u n t f o r 87
( p e r c e n t o f th e s o r t i n g v a lu e s above 3 .0 0, In th e ,fCM
and f,E1 " 'l a y e r s t h e s a n d - s i l t - c l a y s e d im e n ts a c c o u n t f o r
! 100 p e r c e n t o f th e s o r t i n g v a l u e s above 3 . 0 0 b u t o n ly ,
j
! r e p r e s e n t 16 p e r c e n t and 8 p e r c e n t o f th e t o t a l num ber o f
: s a m p le s , r e s p e c t i v e l y .
i The i n c r e a s e in r e l a t i v e l y b e t t e r s o r t i n g c h a r a c t e r
i s t i c s a lo n g th e w e s te r n m arg in c o n s t i t u t e s th e m ost
n o t i c e a b l e change in th e s o r t i n g v a l u e s w i t h d e p th . B oth
F ig u r e 11a* S ta n d a r d d e v i a t i o n c o n to u r s f o r
l a y e r f,Af<.
62
3.4
o
< A >
2.8
O O j
STANDARD DEVIATION
CONTOURS
A - LAYER
CONTOUR INT. 0.2
F ig u r e 1 1 b . S ta n d a r d d e v i a t i o n c o n to u r s f o r
l a y e r "O11.
64
o
2.4
ro
ro
o o
2.6,
STANDARD DEVIATION
CONTOURS
C-LAYER
CONTOUR IN T. 0.2
F ig u r e 11c* S ta n d a r d d e v i a t i o n c o n to u r s f o r
l a y e r . N ote th e r e l a t i v e l y
b e t t e r and more u n ifo rm s o r t i n g .
C J «N
3.0'
2.2'
STANDARD DEVIATION
CONTOURS
E - LAYER
CONTOUR IN T. 0.2
67
th e w e s te rn and c e n t r a l p o r t i o n s o f th e b a s i n in l a y e r s
M 0 H and d e m o n s tr a te b e t t e r s o r t i n g a s w e l l as a
re m a rk a b ly u n ifo rm s o r t i n g s u r f a c e ♦ The w e s t e r n d r a i n
a g e , t h e r e f o r e , in c o n t r a s t t o t h a t from t h e e a s t , a p
p e a r s to have l i t t l e a f f e c t on th e m a r g in a l sa m p le s in
th e d e e p e r l a y e r s .
A g r a p h i c a l method w hich i l l u s t r a t e s t h e d i s t r i b u
t i o n o f s o r t i n g v a lu e s w i t h i n e a c h s i z e g ra d e i s employed
in P i g s . 1 2 a, b , c ( G o r s l i n e , 1 9 5 4 )• The h e i g h t o f th e
a r e a i n d i c a t e s th e number o f sa m p le s w i t h i n th e s o r t i n g
v a lu e s shown. An i n t e r e s t i n g f e a t u r e o f t h i s p r e s e n t a
t i o n i s t h a t i t i l l u s t r a t e s w hat s i z e r a n g e s c o n t a i n th e
h i g h and low s o r t i n g v a l u e s . By a l i n e c o n n e c tin g th e
h i g h e s t v a l u e s w i t h i n e a c h s i z e r a n g e , a p o r t i o n o f a
s i n u s o i d a l t r e n d i s d e f i n e d w h ic h , a c c o r d i n g to P o lk
(1 9 6 4 ) , i s due to t h e :
r e l a t i v e s c a r c i t y in n a t u r e o f g r a n u l e - c o a r s e sand
(0 t o -2 0 ) p a r t i c l e s , and f i n e s i l t (6 to 8 0 )
g r a i n s , s e d im e n ts w i t h mean s i z e s i n t h e s e ra n g e s
m ust be a m ix tu r e o f e i t h e r (1) sand and p e b b l e s , o r
(2) sand o r c o a r s e s i l t w i t h c l a y , h e n ce w i l l be
more p o o r l y s o r t e d th a n th e pure end members (p u re
g r a v e l , s a n d , o r c l a y ) .
The p o o r e s t s o r t i n g v a lu e o r p o i n t o f i n f l e c t i o n
on th e s i n u s o i d a l t r e n d i n P i g s . 1 2 a, b , c i n d i c a t e s th e
s i z e ra n g e in w hich th e p o o r e s t s o r t i n g v a l u e s o c c u r .
P o lk s t a t e d t h a t th e p o o r e s t v a l u e s a r e found in s e d im e n ts
w i t h a mean s i z e o f 6 0 to 8 0 . The p o o r e s t s o r t i n g
v a l u e s , h o w ev er, a r e w i t h i n th e 4 0 to 6 0 ra n g e in l a y e r
F ig u r e 1 2 a . G r a p h ic a l method d e p i c t i n g th e
d i s t r i b u t i o n o f s o r t i n g v a l u e s
w i t h i n eac h s i z e g ra d e f o r la y e
1 1 A ". The p o o r e s t v a l u e s a r e
p r e s e n t in th e 4 0 t o 6 0 ra n g e
GO
LU
O
Z
<
O '
O '
LU
h
LU
<
O
z
<
LU
0.125 - 0.062 m MM
(3 - 40)
0.062 - 0.031 MM.
(4 - 50)
0.031 - 0.016 MM.
(5-60)
0.016 -0.008 MM.
(6 - 70)
0.008 - 0.004 MM.
(7 - 80)
0.004 - 0.002 MM.
(8 - 90)
0.002 - 0.001 MM.
(9 - 100)
STANDARD DEVIATION (SORTING) A-LAYER
Z
o
o
~ n
< />
>
m
< S )
0\
\o
4.0 3.0 2.0
F ig u r e 12b* G r a p h ic a l m ethod d e p i c t i n g th e
d i s t r i b u t i o n o f s o r t i n g v a lu e s
w i t h i n e a c h s i z e g ra d e f o r
l a y e r P o o r e s t s o r t i n g
v a l u e s a r e p r e s e n t in t h e 5 0
t o 6 0 r a n g e .
MEANi DIAMETER RANGES
c q
> I
Z __
O o
> 3
7 0
o
o
m
<
K > I
K >
I
00
I
'£
0
1
O
o
K J
■ N l
I
00
(SI
00
t
O s
I
■Nj
O s
I
00
o n
It
&
0 0
— >
I
I
O s
K >
o
0 0
_ t n
< * > I
I o
O s
K >
I
I
J I L
- * K> OO — NO OO
i I I
NO OO
1 . 1 I
N J OO
J I L
— K > 00
J__I
— ■ N J 0 0
saidw vs j o on
T L
F ig u r e 12c* G r a p h ic a l method d e p i c t i n g th e
d i s t r i b u t i o n o f s o r t i n g v a l u e s
w i t h i n e a c h s i z e g ra d e f o r l a y e r
• P o o r s o r t i n g v a lu e s a r e
p r e s e n t in th e 6 $ t o 8 0
r a n g e .
MEAN DIAMETER RANGES
:
o
o
to
s 0
Q — •
o
8
o
8
00 1
^ 00
■ o ,
' p
1
1 o
x O O
© ©
'w ' to
© S
3 O
2:
■
1
Ox
I
0
©
O x
1
©
© S
• — ' o
00
J I L
— ■ K > 00
K J
c n
O x
to
c n co
c n
© O x
to
CO
to C O
sandwvs do on
74
"A" , th e 5 0 t o 6 0 r a n g e in l a y e r 1,C1,9 and o n ly in l a y e r
1 1 E” do th e v a l u e s conform to th e 6 0 to 8 0 r a n g e . The
b u lk o f th e s o r t i n g v a lu e s o v e r 3 . 0 , n e v e r t h e l e s s , do f a l l
w i t h i n th e 6 0 to 8 0 ra n g e in a l l t h r e e l a y e r s .
Skewness
Skewness m e a su re s th e d e g re e o f asym m etry o f a
d i s t r i b u t i o n c u r v e . P r o v i d i n g t h a t th e b u l k o f th e c u rv e
l i e s w i t h i n th e c o a r s e f r a c t i o n , th e n t h e i n t r o d u c t i o n o f
an e x c e s s amount o f f i n e m a t e r i a l s r e s u l t s in a p o s i t i v e
s ig n f o r th e skew ness v a l u e . N e g a tiv e v a l u e s o c c u r when
a p r e d o m in a n tly f i n e - g r a i n e d s e d im e n t i s c o n ta m in a te d
w ith c o a r s e r m a t e r i a l s . Z ero v a l u e s , on th e o t h e r h a n d ,
can o c c u r e i t h e r w i t h a t r u e n o rm al d i s t r i b u t i o n p ro d u ced
by a s i n g l e o p e r a t i n g a g e n t o r by th e i n t r o d u c t i o n o f a
b a l a n c i n g c o n t r i b u t i o n o f b o th c o a rs e and f i n e m a t e r i a l s
from two s e p a r a t e s o u r c e s . C o n to u r p l o t s o f t h e skew ness
v a l u e s f o r l a y e r s "A ", "C", and "E" a r e p r e s e n t e d in P i g s .
13 a, b, c . The i s o p l e t h v a lu e e q u a ls t h e skew ness v a lu e
m u l t i p l i e d by 100.
The c o n to u r d ia g ra m s r e v e a l two c h a r a c t e r i s t i c s to
be c o n s i d e r e d : (1) d is a p p e a r a n c e o f th e h i g h n e g a t iv e
skew ness v a lu e s w i t h d e p th and (2 ) th e d e c l i n e o f n e g a t i v e
v a l u e s w i t h d e p th . An e x p l a n a t i o n o f th e two s i t u a t i o n s
c e n t e r s a ro u n d th e d e c r e a s e in c o a r s e m a t e r i a l s . The
i n t r o d u c t i o n o r c o n c e n t r a t i o n o f s a n d - s i z e d m a t e r i a l s on a
F ig u r e 1 3 a . C o n to u r p l o t o f sk ew n ess v a lu e s
f o r l a y e r UAU.
76
SKEWNESS CONTOURS
A - LAYER
CONTOUR INT. 25
ISOPLETHS (SK) (100)
F ig u r e 13 b. C o n to u r p l o t o f skew ness v a lu e s
f o r l a y e r M CH*
M
cn
o
'A
C M
SKEWNESS CONTOURS
C - LAYER
CONTOUR INT. 25
ISOPLETHS (SK) (100)
F ig u r e 1 3 c . C o n to u r p l o t o f skew ness v a lu e s
f o r l a y e r H E,f.
80
O t •
< o
CM
SKEWNESS CONTOURS
E - LAYER
CONTOUR INT. 25
ISOPLETHS (SK) (100)
! 81
p re d o m in a n tly f i n e - g r a i n e d s u r f a c e r e s u l t s in ex trem e
■ n e g a t i v e skew ness v a l u e s . C o n tin u e d c o n c e n t r a t i o n o f th e
| c o a r s e m a t e r i a l s e v e n t u a l l y c a u s e s a s h i f t t o th e p o s i t i v e
| s i d e when t h e c o a r s e m a t e r i a l becomes d o m in a n t. T h is c o n -
t
: c e p t i s i l l u s t r a t e d c l e a r l y in F i g . 13a i n w hich th e
; la g o o n f l a t and th e m a r g in a l a r e a s a r e s e p a r a t e d by a
J c o n tin u o u s z e ro i s o p l e t h . N e g a tiv e v a l u e s w i t h i n th e
| b o u n d a r ie s o f th e z e ro i s o p l e t h and p o s i t i v e v a l u e s a lo n g
i
I th e m a r g i n a l a r e a s a r e c o n s i s t e n t w ith th e p r e s e n t a t i o n
l
I a b o v e . W ith d e p th , ho w ev er, t h e d e c r e a s i n g p e r c e n t a g e o f
i
! s a n d - s i z e d m a t e r i a l s r e s u l t s in l e s s e x tre m e n e g a t i v e
t
v a l u e s ; t h e r e f o r e , l e s s d i f f e r e n t i a t e d skew ness
b o u n d a r i e s .
The d e c l i n e o f th e n e g a t i v e v a l u e s w i t h d e p th i s
I
: e x p la in e d by n o t i n g t h e c o r r e l a t i o n betw een th e i n c r e a s e
! in a r e a s o f p o s i t i v e skew ness w i t h t h e i n c r e a s e in a r e a s
i
j o f c la y e y s i l t . Com paring th e l a y e r f*E,f s e d im e n t
| d iag ra m ( F i g . 7 c) w i t h th e c o r r e s p o n d i n g skew ness c o n to u r s
, in F i g . 13c i l l u s t r a t e s th e c l o s e a s s o c i a t i o n betw een th e
c la y e y s i l t p a tc h and th e a r e a o f p o s i t i v e skew ness v a lu e s
n e a r th e e a s t e r n m a r g in . S h i f t s betw een p o s i t i v e and
f
; n e g a t i v e sk ew ness v a l u e s o c c u r o n ly w i t h i n th e c la y e y s i l t s
and s a n d - s i l t - c l a y g ro u p s ; t h e r e f o r e , T ab le I was p r e
p a re d t o i n d i c a t e t h e v a r i a b i l i t y o f th e chan g es w ith
, d e p th . D e s p ite t h e r e d u c t i o n in th e num ber o f s a n d - s i l t -
!
c l a y sam p les from l a y e r s U AU t o f,Eff th e r e l a t i v e p e r c e n t -
TABLE I
CLAYEY SILTS
4
L ay e r M A,! L ay e r "C" L ay e r "E"
Number o f Sam ples
(9) (13) (14)
P e r c e n ta g e o f (+)
Skewness V a lu e s 33% (+) 54^ (+) 86% (+)
P e r c e n ta g e o f ( - )
Skewness V alu es 67% ( - )
SAND-SILT
46% ( - )
CLAT
14% ( - )
Number o f Sam ples (24)
(13)
(6)
P e r c e n ta g e o f (+)
Skewness V a lu e s 33% (+) 31% (+) 33% (+)
P e r c e n ta g e o f ( - )
Skewness V alues 67% ( - )
69% ( - ) 67% ( - )
83
a g e s o f th e p o s i t i v e and n e g a t i v e skew ness v a l u e s rem a in
e s s e n t i a l l y u n c h an g e d . Such c o n s i s t e n c y i s p re su m a b ly due
t o c o i n c i d e n c e . A more i n t e r e s t i n g c h a n g e , n e v e r t h e l e s s ,
i s r e v e a l e d i n th e c la y e y s i l t s . R e v e r s a l o f th e p r e
d o m in a n tly n e g a t i v e c h a r a c t e r o f th e skew ness v a l u e s in
th e s u r f a c e sam p les to a s l i g h t p red om inance o f th e
p o s i t i v e v a l u e s in l a y e r wC,f and e v e n t u a l l y to a co m p lete
dom inance o f t h e p o s i t i v e v a l u e s in l a y e r can b e s t be
e x p la in e d by co m paring th e h i s t o g r a m s o f th e c la y e y s i l t
sam p les f o r l a y e r s f,A,f, 1 1 Cf*, and ,fE,f ( P i g s . 1 4 a , b , c ) .
The h i s t o g r a m s w ere grou ped a c c o r d i n g to t h e i r c h a r a c t e r
i s t i c m odal c l a s s a s w e l l a s t h e s ig n o f t h e i r skew ness
v a l u e . B a s i c a l l y t h r e e g ro u p s were r e c o g n iz e d in l a y e r
"A ". The f i r s t g ro u p c o n t a i n s th e sa m p le s w i t h n e g a t i v e
skew ness v a l u e s and t h e l a r g e s t w e ig h t p e r c e n t a g e o f
p a r t i c l e s in th e c la y f r a c t i o n w h ile t h e seco n d g ro u p ,
a l s o n e g a t i v e , c o n t a i n s t h e h i g h e s t w e ig h t p e r c e n t a g e o f
p a r t i c l e s i n th e s i l t f r a c t i o n . Group t h r e e i s c o m p rise d
o f t h e p o s i t i v e v a lu e s a m p le s . The a b se n c e o f t h e second
g ro u p in l a y e r nS u i s c o n s i d e r e d th e k ey t o th e d e c l i n e
o f th e n e g a t i v e v a l u e s w i t h d e p th . F o r ex am p le, i f th e
c o a r s e f r a c t i o n were removed from th e group (2 ) h i s t o g r a m s
i n l a y e r s f,A,f and !,Cn , t h e i r c h a r a c t e r i s t i c p a t t e r n s would
be i d e n t i c a l to th o s e in g rou p (3)» t h e r e f o r e , a change
o f s i g n o c c u r s . Group ( l ) h i s t o g r a m s , e x c e p t f o r 6R3A612
and 4L1A712 would re s e m b le t h e group ( l ) h i s t o g r a m s in
F ig u r e 14a* H is to g ra m s o f t h e c la y e y s i l t
s e d im e n ts in l a y e r 1 1 A . The
h i s t o g r a m s a r e group ed a c c o r d i n g
t o t h e i r c h a r a c t e r i s t i c m odal
c l a s s a s w e l l a s t h e s ig n o f
t h e i r skew ness v a l u e .
HISTOGRAMS
CLAYEY SILTS
LAYER A (SKEWNESS)
GROUP 2
GROUP 1
4R3A912 (-25) 7R3A (-53)
GROUP 3
6R2A812 (-75)
6R3A612 (-55) 2R2A (57)
1A612 (35)
4L1A712 (-15)
-SAND--------- — SILT----- -C L A Y -
1 i__L __L ., , .1... 1 -L _ 1 1
25
3A (11) 6R3A06 (4)
00
V J 1
F ig u r e 1 4 b . H is to g ra m s o f t h e c la y e y s i l t
s e d im e n ts i n l a y e r nCn .
HISTOGRAMS
CLAYEY SILTS
LAYER “ C" (SKEWNESS)
GROUP 1
3L1C (-60)
25
7R2C06 (-40) 6R3C (-8)
25
GROUP 2
2L2C (-30) 3C (-26)
SAND- SILT H C LA Y -
I 1 L . I., i
87
5L1C (-22)
GROUP 3
ZiLi
7R1C (81) 2R2C (80) 6C (24)
3R1C (69) 6L2C(24) 4R1C(14)
25
i j
4L1C (3)
F ig u re 1 4 c . H is to g ra m s o f t h e c la y e y s i l t
s e d im e n ts in l a y e r "E™ •
HISTO GRAMS
CLAYEY SILTS
LAYER "E ” (SKEWNESS)
GROUP 1
4R3E (-20) 6R2E (-5)
GROUP 2
5L2E (118) 5L1E (109)
25
3R1E (70)
-SAND-
J .1 L -L
SILT h C L A Y -
I 1-1 L 1,1
B9
4E612 (47)
7R1E (24) 4L1E (28) 6L2E (10)
90
l a y e r ffE" and no change o f s i g n would o c c u r . The two
e x c e p t i o n s a r e n o te d b e c a u se o f t h e low p e r c e n t a g e o f
p a r t i c l e s i n th e c l a y f r a c t i o n . I t would a p p e a r , from an
e x a m in a tio n o f a l l th e sa m p le s a n a l y z e d , t h a t a p e r c e n t -
i
I
j age o f p a r t i c l e s o f a t l e a s t 31 p e r c e n t in th e c la y
! f r a c t i o n i s n e e d e d t o i n s u r e a n e g a t i v e skew ness v a l u e .
; The p o i n t , t h e n , i s t h a t w i t h o u t t h e c o a r s e f r a c t i o n 67
: p e r c e n t o f t h e e x i s t i n g n e g a t i v e v a l u e s would now be
i
| p o s i t i v e and o n ly two g ro u p s would re m a in . S in c e t h i s
i
c o n d i t i o n i s a l r e a d y p r e s e n t i n l a y e r ffEff, t h e a u t h o r
c o n c lu d e s t h a t t h e r i s e i n t h e p o s i t i v e skew ness v a lu e s
I and th e d e c l i n e o f t h e n e g a t i v e v a l u e s i s due t o th e
, d im in is h e d sand s u p p ly t o t h e lag o o n in p a s t t i m e .
A p l o t o f skew ness v e r s u s s o r t i n g a p p e a r e d , a t
i
j f i r s t , to have no s i g n i f i c a n t r e l a t i o n s h i p . By s c a l i n g
i o f f th e maxima and m inim a o f e a c h s e d im e n t t y p e , h ow ever,
J a g r o u p in g was r e v e a l e d w hich had l i t t l e o r no o v e r l a p .
■ i
j Where o v e r l a p p i n g o f th e b o x es d i d o c c u r t h e r e was
, v i r t u a l l y no o v e r l a p o f t h e p o i n t s th e m s e lv e s ( P i g s . 15 a,
i
1 b , c ) . The p r e s e n t a t i o n i s u s e f u l in t h a t c o m p a riso n s o f
, t h e a r e a l ch an g e s i n t h e se d im e n t g ro u p s can r e a d i l y be
1
m ade. F o r ex am p le, t h e p r e v i o u s comments t h a t s o r t i n g
becomes i n c r e a s i n g l y b e t t e r w i t h d e p th i s e a s i l y r e c o g -
! n i z e d by n o t i n g t h e s h i f t i n g o f t h e maxima and minima
' d e f i n i n g t h e s e d im e n t t y p e s a lo n g th e v e r t i c a l a x i s .
A n o th e r f a c t o r n o t r e a d i l y a p p a r e n t in o t h e r p r e s e n t a t i o n s
F ig u r e 1 5 a . P l o t o f skew ness v e r s u s s t a n d a r d
d e v i a t i o n f o r l a y e r ,#Aff * S c a l i n g
o f f t h e r e s p e c t i v e s e d im e n t ty p e s
r e v e a l s a d e f i n i t i v e g ro u p in g f o r
e a c h . D e s p ite th e o v e r l a p p i n g o f
th e b o u n d a r i e s t h e r e i s v i r t u a l l y
no o v e r l a p o f t h e p o i n t s .
STANDARD DEVIATION (SORTING)
N > C J
SILTY CLAY
m
m
m
m
ro
K C A
r IS
> %
< z
m m
za w *
7 0 m
V O
ro
F ig u r e 1 5b. P l o t o f skew ness v e r s u s s t a n d a r d
d e v i a t i o n f o r l a y e r “ C*1 •
STANDARD DEVIATION (SORTING)
N )
™ r
□
SILTY CLAY
0 £
r
< z
m I"
3 a
^ < /»
CO
T
c /»
c /»
oO
« />
C O
□
K )
V O
-fs -
F ig u r e 1 5 c . P l o t o f skew ness v e r s u s s t a n d a r d
d e v i a t i o n f o r l a y e r "E11.
STANDARD DEVIATION (SORTING)
ro C O
_ c /»
m *
p " r n
< %
m ni
3 0 ^
^ < />
SILTY CLAY
< /»
■ r
H »
< />
>
Z
»9
< /»
o
r
>
-<
ro
V O
O N
97
i s t h a t t h e s i l t y c l a y s , as a g ro u p , a r e b e t t e r s o r t e d in
l a y e r "C,f• The a u t h o r d i d n o t p u rsu e an e x p l a n a t i o n o f
t h i s phenomenon b u t i t s r e c o g n i t i o n i s o f s u f f i c i e n t v a lu e
t o j u s t i f y th e d i a g r a m 1s u s a g e . A lso s t a t e d e a r l i e r was
th e s h i f t i n th e skew ness v a l u e s o f t h e c la y e y s i l t group
from a p re d o m in a n tly n e g a t i v e to a p re d o m in a n tly p o s i t i v e
c h a r a c t e r . I f t h e s e p a r a t i o n o f s e d im e n t t y p e s o c c u r s
c o n s i s t e n t l y w i t h i n t h e two p a r a m e t e r s , th e n t h e d ia g ra m s
may p ro v e u s e f u l i n i d e n t i f y i n g s i m i l a r e n v iro n m e n ts and
p o s s i b l y in d i f f e r e n t i a t i n g betw een them .
P l o t s o f sk ew ness v e r s u s mean d i a m e t e r f o r th e
t h r e e sam ple l a y e r s 1 1 Au , flCfl, and ,fEfl r e v e a l e s s e n t i a l l y
s t r a i g h t - l i n e r e l a t i o n s h i p s ( P i g s . 1 6 a , b , c ) . D e v ia tio n s
from t h i s r e l a t i o n s h i p a r e due t o t h e c o a r s e r s e d i m e n ts .
L a y e rs “A” and U CU e x h i b i t t h e m ost a p p a r e n t d e v i a t i o n s
a s two s e p a r a t e t r e n d s a r e r e c o g n i z e d . In l a y e r **CH t h e
lo w e r t r e n d c o n t a i n s a l l th e s a n d - s i l t - c l a y s w h e rea s in
l a y e r "A" th e s e p a r a t i o n o c c u r s w i t h i n th e sand and s a n d -
s i l t - c l a y s a m p le s . The s e p a r a t i o n s p ro b a b ly r e f l e c t th e
s c a t t e r p r e s e n t i n t h e t e x t u r a l p a r a m e t e r s .
K u r t o s i s
K u r t o s i s i s th e r a t i o betw een t h e s o r t i n g o f th e
t a i l s and th e s o r t i n g o f th e c e n t r a l p o r t i o n o f t h e c u r v e .
When th e c e n t r a l p o r t i o n s a r e e x c e s s i v e l y p e a k e d , th e
c u rv e i s s a i d t o be l e p t o k u r t i c w h ile b e t t e r s o r t i n g in
F ig u r e 1 6 a . Skewness p l o t t e d a g a i n s t mean
d i a m e t e r f o r l a y e r “A". E s s e n
t i a l l y s t r a i g h t l i n e r e l a t i o n s h i p s
o c c u r f o r th e t h r e e l a y e r s .
SKEWNESS
99
MEAN DIAMETER (PHI-UNITS)
A-LAYER
F ig u r e l 6 b # A p l o t o f skew ness v e r s u s mean
d i a m e t e r f o r l a y e r
101
«/>
\ Si
1 1 1
z
ui
oo
• •
MEAN DIAMETER (PHI-UNITS)
C-LAYER
F ig u r e 16c* A p l o t o f sk ew ness v e r s u s mean
d i a m e t e r f o r l a y e r “E11.
103
to
to
UJ
z
UJ
to
MEAN DIAMETER (PHI-UNITS)
E-LAYER
104
! t h e t a i l s p ro d u c e s a f l a t - p e a k e d o r p l a t y k u r t i c c u rv e .
!
Normal d i s t r i b u t i o n s a r e r e f e r r e d t o a s m e s o k u r tic
i
i c u r v e s . In g e n e r a l , t h e n , th e p o s i t i v e k u r t o s i s v a lu e s
| r e p r e s e n t l e p t o k u r t i c c u rv e s and n e g a t i v e v a l u e s r e p r e s e n t
i
i th e p l a t y k u r t i c c u r v e s . L e p t o k u r t i c c u rv e s a r e p o s s i b l e
i
| in b o th f i n e and c o a r s e g r a i n m a t e r i a l s .
j Inasm uch a s skew ness r e f l e c t s t h e r e l a t i v e b a la n c e
; o f th e t a i l s and k u r t o s i s r e f l e c t s t h e i r r e l a t i v e
I
1 abundance ( L u s t i g , 1 9 6 5 ), a p l o t o f t h e two p a r a m e te r s was
, p r e p a r e d t o i l l u s t r a t e w hat g r a p h i c a l r e l a t i o n s h i p s e x i s t
| ( P i g s . 1 7 a , b , c ) . The r e s u l t was th e f a m i l i a r s i n u s o i d a l
i
: t r e n d w hich r e f l e c t s t h e f a c t t h a t a s skew ness v a r i e s
j
j from n e g a t i v e t o p o s i t i v e v a l u e s th e k u r t o s i s v a r i e s from
i
i p o s i t i v e to n e g a t i v e t o p o s i t i v e . S in c e th e r e l a t i o n s h i p
betw een skew ness and mean d i a m e t e r i s l i n e a r , a lm o s t
i d e n t i c a l p l o t s t o P i g s . 1 7 a , b , c a r e o b t a i n e d when th e
j k u r t o s i s v e r s u s mean d i a m e t e r r e l a t i o n s h i p i s i n v e s t i g a t e d .
| L e p t o k u r t i c c u rv e s a r e s u b o r d i n a n t in num ber t o th e p l a t y
k u r t i c c u rv e s i n e a c h sam ple l a y e r , an e x p e c te d f a c t in a
mixed e n v iro n m e n t; an d , e x c e p t f o r l a y e r ,lE,f, th e y a r e
i more common i n t h e f i n e m a t e r i a l s . The d is a p p e a r a n c e o f
th e l e p t o k u r t i c c o n d i t i o n in th e f i n e m a t e r i a l s w i t h d e p th
i s a t t r i b u t e d t o t h e g e n e r a l l a c k o f m a t e r i a l s in th e
| 6 .5 0 and 9 .5 0 s i z e r a n g e ; t h e r e f o r e , t h e h i g h p e r c e n t a g e
. o f c o a r s e s i l t s and c o l l o i d a l f r a c t i o n s r e s u l t s in th e
c h a r a c t e r i s t i c b im o d a l s i z e d i s t r i b u t i o n c u rv e s ( P i g s .
F ig u r e 1 7 a . A p l o t o f t h e two p a r a m e t e r s ,
skew ness and k u r t o s i s , i s made
f o r l a y e r M AM. Sam ples w i t h
l e p t o k u r t i c c u rv e s a r e more
common in th e s u r f a c e l a y e r s .
KURTOSIS
N >
ro
• •
90T
F ig u re 17b. A p l o t o f skew ness v e r s u s k u r t o s i s
f o r l a y e r ,fCH •
• •
• •
— f •<
2 0 -1
SKEWNESS
C-LAYER
F ig u r e 1 7 c . A p l o t o f skew ness v e r s u s k u r t o s i s
f o r l a y e r "E ".
«/>
o
I-
SKEWNESS
E - LAYER
I l l
1 4 a , b , c ) . L e p t o k u r t i c c u rv e s in th e c o a r s e m a t e r i a l s
a r e due p r i m a r i l y t o t h r e e sam ple l o c a t i o n s , 5L2, 6L2A,
and 3C. Sample 5L2 i s l e p t o k u r t i c t h r o u g h o u t t h e l e n g t h
o f th e c o r e .
The k u r t o s i s v a lu e o f th e ap ex i n eac h l a y e r n e v e r
e x c e e d s - 1 .6 0 w h ich s u g g e s t s , a t l e a s t f o r t h i s e n v i r o n
m en t, a v a l i d l i m i t f o r t h e d e g re e o f p l a t y k u r t o s i s .
C o n to u r maps w ere p r e p a r e d to i l l u s t r a t e th e p o s i
t i o n s o f th e k u r t o s i s v a l u e s on th e la g o o n s u r f a c e ( F i g s .
! 1 8 a , b , c ) . The i s o p l e t h v a lu e e q u a l s th e k u r t o s i s v a lu e
m u l t i p l i e d by 100.
S im ple k u r t o s i s a s w e l l as skew ness c a l c u l a t i o n s
; c e a s e t o have m eaning f o r th e s t r o n g l y b im o d a l s e d im e n ts ,
' n e v e r t h e l e s s , k u r t o s i s i s a s e n s i t i v e i n d i c a t o r o f th e b i -
\ 9
i
t
| m odal and u n im o d a l d i s t r i b u t i o n s and i s u s e f u l in a mixed
i
e n v iro n m e n t f o r i n d i c a t i n g p o s s i b l e s o u rc e d i r e c t i o n s a s
w e l l a s th e i n c r e a s i n g o r d e c r e a s i n g i n f l u e n c e o f t h e s e
s o u r c e s . The c o n t o u r d iag ra m f o r l a y e r 1 1 AM ( F i g . 18a)
r e v e a l s o n ly t h r e e l e p t o k u r t i c o r u n im o d a l t r e n d s . As
e x p e c te d , th e a l l u v i a l s o u r c e s a lo n g th e e a s t e r n m arg in
| a r e th e o n ly l a r g e c o n t r i b u t o r s o f c o a r s e m a t e r i a l s and
!
t h u s c a u se t h e c o a r s e l e p t o k u r t i c an om aly. The two
i r e m a in in g t r e n d s , l e p t o k u r t i c ( f i n e ) , a p p e a r t o o r i g i n a t e
i
I from a s o u t h e r l y s o u rc e b u t f u r t h e r s a m p lin g would be
i
j n e c e s s a r y to c o n firm them . The t r e n d a lo n g t h e w e s te r n
i
edge i s l i k e l y i n f l u e n c e d by t h e dune m a t e r i a l s in t h a t
F ig u r e 1 8 a . K u r t o s i s c o n to u r s f o r l a y e r f‘An .
A d e c r e a s e in th e p o s i t i v e
( l e p t o k u r t i c ) v a l u e s o c c u r s w i t h
d e p th .
113
U l
o
o
o
o.
Ift
KURTOSIS CONTOURS
A - LAYER
CONTOUR INT. 50
ISOPLETHS (K) (100)
F ig u r e 18b. K u r t o s i s c o n to u r s f o r l a y e r
115
-YOO’
• O s * - .
o
«v
o
KURTOSIS CONTOURS
C - LAYER
CONTOUR INT. 50
ISOPLETHS (K) (100)
F ig u r e 1 8 c . K u r t o s i s c o n to u r s f o r l a y e r
117
cn
O
O
Cn
Ln
Cn
KURTOSIS CONTOURS
E - LAYER
CONTOUR INT. 50
ISOPLETHS (K) (100)
118
a r e a and t h e r e f o r e n o t d i r e c t l y a s s o c i a t e d w i t h a s o u rc e
d i r e c t i o n . On t h e o t h e r h a n d , i f t h e t r e n d in th e s o u t h
e a s t r e p r e s e n t s a t r u e s o u r c e , th e n i t c o u ld have
o r i g i n a t e d i n t h e d r a i n a g e sy ste m a lo n g t h e s o u t h e a s t
m a rg in o r t h e d i s t r i b u t i o n c h a n n e ls from t h e s o u t h . The
f i n e - g r a i n e d c h a r a c t e r o f th e se d im e n t l e a d s th e w r i t e r
to c o n c lu d e t h a t t h e d i s t r i b u t i o n c h a n n e ls p r o v id e t h e
m ost l i k e l y s o u r c e d i r e c t i o n . The c o n tin u a n c e o f th e
two dom inant l e p t o k u r t i c t r e n d s in l a y e r f,Cf1 s t r e n g t h e n s
t h e i r p o s i t i o n a s s o u r c e d i r e c t i o n s . I n t e r e s t i n g l y
enough, th e changes w i t h d e p th s u g g e s t t h a t t h e e a s t e r n
t r e n d h a s a d e c r e a s i n g i n f l u e n c e and t h e s o u t h e r n t r e n d
an i n c r e a s i n g i n f l u e n c e on th e b a s i n s e d i m e n ts .
E x ce p t f o r th e s m a ll l e p t o k u r t i c s o u rc e a t sam ple
l o c a t i o n :5Ij2E, l a y e r "E" ( F i g . 18c) e x h i b i t s a re m a rk a b ly
u n ifo rm p l a t y k u r t i c s u r f a c e w hich c o n t r a s t s w i t h th e
e a s i l y d i f f e r e n t i a t e d i s o p l e t h s u r f a c e s i n l a y e r "A" and
"C ". In f a c t , t h e l a c k o f th e l e p t o k u r t i c c o n to u r s in
l a y e r HEn s u p p o r t s th e c o n c e p t o f th e p r e s e n c e a t t h a t
tim e o f a body o f w a te r o v e r th e la g o o n s u r f a c e , a t l e a s t
to t h e l e v e l o f th e sam ple l o c a t i o n s .
C hem ical D ata
C a rb o n a te C o n te n t
S i g n i f i c a n t changes i n th e c a r b o n a te c o n t e n t w ere
found o n ly i n t h e v e r t i c a l d i r e c t i o n s , t h a t i s , a g e n e r a l
119
i n c r e a s e in t h e c a r b o n a t e c o n t e n t w i t h d e p th ( F i g . 1 9 a ) .
Sample 4L2E r e v e r s e d t h i s t r e n d by d e c r e a s i n g to 3 .6
p e r c e n t from a p r e v i o u s h ig h a t th e s u r f a c e o f 1 0 .3 p e r
c e n t . The f o r a m i n i f e r a c o n c e n t r a t i o n s a p p e a r to have
l i t t l e e f f e c t on t h e p e r c e n t a g e o f c a lc iu m c a r b o n a te
p r e s e n t b u t when mean d i a m e t e r i s p l o t t e d a g a i n s t c a lc iu m
c a r b o n a t e , a b r o a d l y c o n s i s t e n t r e l a t i o n s h i p i s r e c o g n iz e d
w hich shows t h a t t h e h i g h e r p e r c e n t a g e s a r e p r e s e n t in th e
f i n e r m a t e r i a l s ( F i g . 2 0 ) . A p o s s i b l e e x p l a n a t i o n can th e n
be o f f e r e d f o r th e d i s c r e p a n c y a t 4L2E s i n c e i t i s th e
o n ly sam ple w hich becom es c o a r s e r w i t h d e p th , h ow ev er,
t h e c o a r s e sam p les a t th e s u r f a c e a l l have p e r c e n t a g e s
h i g h e r th a n 4L2E.
Oarbon C o n te n t
V a lu e s f o r th e o r g a n i c carb o n p e r c e n t a g e s ra n g e d
from t r a c e s t o 0 .8 0 p e r c e n t . The two e x tre m e s a r e
fo u n d o n ly in sa m p le s 4L1A712 and 4L2A812 ( F i g . 1 9 b ) .
N e g l e c t i n g t h e s e e x tre m e v a l u e s , t h e o r g a n i c c arbon
p e r c e n t a g e s , th o u g h low , a r e q u i t e u n ifo r m . The low v a lu e s
can be a t t r i b u t e d to t h e i n t e r m i t t e n t f l o o d i n g and d r y in g
o f th e la g o o n s u r f a c e w hich e x p o se s t h e o r g a n i c c a rb o n to
t h e a tm o sp h e re and s u b s e q u e n t o x i d a t i o n , p ro b a b ly b i o
c h e m ic a l.
T o t a l carb o n p e r c e n t a g e s a r e p r e s e n t e d i n F i g . 19c
a n d , e x c e p t f o r 4L2E, d e m o n s tr a te an i n c r e a s e w i t h d e p th .
F ig u r e s 1 9 a , b, c . P e r c e n t a g e s o f c a lc iu m
c a r b o n a t e , o r g a n i c c a rb o n ,
and t o t a l c a rb o n i l l u s t r a t e
th e r e l a t i v e u n i f o r m i t y o f
t h e v a r i a t i o n s w i t h t h e e x
c e p t i o n o f sam p les 4L1 and
4L2.
4R1
4L3 4L1 4L2
CALCIUM
CARBONATE
ORGANIC
CARBON
LO
TOTAL
CARBON
F ig u r e 2 0 . Mean d i a m e t e r v e r s u s c a lc iu m
c a r b o n a t e , a b r o a d l y c o n s i s t e n t
r e l a t i o n s h i p in w hich th e h i g h e r
p e r c e n t a g e s p r e s e n t in th e f i n e r
m a t e r i a l s i s r e v e a l e d .
123
x
D .
t c
UJ
h
UJ
z
<
UJ
3 S
CaC03 (PERCENTAGE) A
E'* LAYERS OF SAMPLES 4L2, 4, AND 4R3
0
i2;4
Sample 4L2 o c c u p ie s an anom alous p o s i t i o n w i t h i n p r a c t i c a l
l y e v e ry p a r a m e t e r . At th e s u r f a c e i t r e p r e s e n t s one o f
th e f i n e r - g r a i n e d s e d i m e n ts , y e t i t i s l o c a t e d in and
hounded by t h e c o a r s e s t s e d im e n ts i n th e b a s i n . The
o t h e r s e d im e n ts become f i n e r w i t h d e p th , w h e rea s 4L2E
r e p r e s e n t s one o f t h e c o a r s e s t sa m p le s w i t h i n th e 4 t o 5
f o o t d e p th l e v e l . The e x p l a n a t i o n f o r th e anom alous
c a r b o n a t e , o r g a n i c c a r b o n , and t o t a l c a rb o n p e r c e n t a g e s i s
a p t to be th e one n eed ed t o e x p l a i n th e anom alous t e x t u r a l
c h a n g e s . One p o s s i b l e i n t e r p r e t a t i o n i s th e c lo s e
p r o x im ity o f sam ple 4L2 to th e a l l u v i a l f a n . I t i s co n
c e i v a b l e t h a t t h e a l l u v i a l m a t e r i a l s w ere d e p o s i t e d a s f a r
a s t h e sam ple l o c a t i o n a t 4L2 d u r i n g th e a c c u m u la tio n o f
th e s e d im e n ts o f l a y e r "E1 *. S u b s e q u e n t d i r e c t i o n a l
c h an g e s in th e d r a in a g e o f f th e a l l u v i a l a r e a may have
r e s u l t e d i n th e s u r f a c e t e x t u r a l changes n o te d in sam ple
4L2 a s w e l l a s a f f e c t i n g th e v a r i a t i o n s w i t h i n t h e c arb o n
and c a r b o n a te c o n t e n t s .
O oarse F r a c t i o n A n a ly s is
G e n e ra l
The sand f r a c t i o n s o f th e s u r f a c e sam p les a lo n g
th e m a rg in s and th e c e n t e r t r a v e r s e w ere exam ined f o r
t h e i r g r o s s m i n e r a l o g i c c o n t e n t t o d e te rm in e p r o b a b le
s o u r c e s and d i f f e r e n c e s .
L i g h t M in e r a ls
I
i
Q u a rtz c o n t e n t s v a ry from 33 to 58 p e r c e n t and 1
i
i have an a v e ra g e v a lu e o f 46 p e r c e n t , P l a g i o c l a s e c o n - i
: I
i t e n t s v a ry from 29 to 58 p e r c e n t and a v e ra g e 40 p e r c e n t ,
! w h ile an a v e ra g e o f 14 p e r c e n t f o r th e p o t a s h f e l d s p a r s
< o c c u r s w i t h i n a ra n g e o f 6 t o 22 p e r c e n t . The v a l u e s
I
: above compare f a v o r a b l y w i t h P e n i n s u l a r Range s e d im e n ts
!
in sam p les 16 and 17 d i s c u s s e d by M erriam and Bandy ( 1 9 6 5 ).'
Changes in th e q u a r t z , o r t h o c l a s e , and p l a g i o c l a s e
1 p e r c e n t a g e s a c r o s s t h e Laguna S a la d a a r e shown in T ab le ■
I I I w hich l i s t s t h e a v e r a g e p e r c e n ta g e v a lu e s f o r th e e a s t , |
| w e s t , and c e n t e r t r a v e r s e s . Pew d i f f e r e n c e s e x i s t b u t ^
; t h e r e i s an i n d i c a t i o n t h a t th e g r a n i t i c s o u r c e s o f th e
i
j S i e r r a de l o s Cucapas a r e s l i g h t l y more a c i d i c th a n th o s e ,
from th e S i e r r a J u a r e z . Q u a r t z / f e l d s p a r r a t i o s ( P i g . 21) I
| r e v e a l t h a t d i f f e r e n c e s a r e a l s o p r e s e n t i n t h e n o r t h and
1 s o u t h d i r e c t i o n s . The h i g h e s t q u a r t z p e r c e n t a g e s , o u t
l i n e d by th e 0 .9 and 1 .2 c o n t o u r s , o c c u r in o n ly two
l o c a l i t i e s ; th e n o r t h e r n end ( l i n e s 1, 2, and 3) and th e
! e a s t e r n h a l f o f l i n e 5* Dominance o f th e h i g h p l a g i o c l a s e 1
1
p e r c e n t a g e s (4 9 -5 7 p e r c e n t ) i s c l e a r l y shown in P i g . 22
( p l a g i o c l a s e / o r t h o c l a s e r a t i o s ) by th e 4 .0 and 6 . 0 co n -
; t o u r s . A reas o f h ig h o r t h o c l a s e (1 5 -2 0 p e r c e n t ) a r e
! i n d i c a t e d by th e 2 .0 c o n to u r l i n e s . The p re d o m in a n tly
a n g u l a r t o s u b a n g u l a r and o c c a s i o n a l su b ro u n d e d a p p e a ra n c e
TABLE I I
126
AVERAGE QUARTZ ARB FELDSPAR PERCENTAGE VALUES
FOR THE MARGINAL AND CENTER TRAVERSES
W est C e n te r E a s t
(R) (L)
_________________________ P e r Cent_________P e r Cent_________P e r Cent
Q u a rtz 44 46 47
O r t h o c l a s e 11 15 15
P l a g i o c l a s e 45 39 38
F ig u re 2 1 . Q u a r t z / f e l d s p a r r a t i o s . The
h i g h e s t q u a r t z p e r c e n t a g e s a r e
o u t l i n e d by t h e 0 .9 and 1 .2
c o n t o u r s •
128
QUARTZ-FELDSPAR
RATIOS
LAYER A,
F ig u r e 22. P l a g i o c l a s e / o r t h o c l a s e r a t i o s .
Dominant p l a g i o c l a s e p e r c e n t a g e s
a r e shown by th e 4 .0 and 6 .0 con
t o u r s . A re as w ith h i g h o r t h o c l a s e
a r e i n d i c a t e d by th e 2 .0 c o n t o u r s .
130
PLAGIOCLASE-ORTHOCLASE
RATIOS
LAYER A ,
131
i
o f th e g r a i n s in a l l th e sa m p le s, in a d d i t i o n to th e
abundance and f r e s h u n w e a th e re d a p p e a ra n c e o f th e f e l d
s p a r s , s t r o n g l y s u g g e s t s t h a t th e g r a n i t i c m asses to th e
e a s t and w e st o f t h e b a s i n a r e th e m a jo r c o n t r i b u t o r s o f
t h e c o a r s e m a t e r i a l s .
Heavy M in e r a ls
! B i o t i t e , h o r n b le n d e , and a u g i t e c o n s t i t u t e th e
m a jo r com ponents o f th e heavy m in e r a l p r o d u c t s . M inor
c o n s t i t u e n t s i n c l u d e d a p a t i t e , s p h e n e , z i r c o n , m a g n e tic s ,
and o p a q u e s. A n h y d rite was p r e s e n t in c o n s i d e r a b l e
q u a n t i t i e s i n a few sa m p le s.
The c o l o r o f th e b i o t i t e v a r i e d from l i g h t brown
,and g re e n to d a r k brow n. In g e n e r a l t h e e a s t e r n m arg in
jsp ecim en s e x h i b i t a d a r k e r a p p e a ra n c e due to th e p r e
dom inance o f t h e d a rk brown b i o t i t e i n c o n t r a s t to th e
w e s te r n sam p les w hich c o n t a i n th e l i g h t e r c o l o r s .
S am ples 11 and 51 a lo n g th e c e n t e r t r a v e r s e c o n ta in e d
r e l a t i v e l y few b i o t i t e s and t h u s d i f f e r from th e dom inant
p e r c e n t a g e s in th e m a r g in a l sa m p le s .
The h eav y m i n e r a l s i d e n t i f i e d i n a l l th e sam ples
a r e c o n s i s t e n t w ith th e i d e a o f g r a n i t i c s o u r c e s .
Heavy m i n e r a l p e r c e n t a g e s w ere c o n to u r e d in F ig .
23 and i l l u s t r a t e t h a t th e a b u n d a n t p e r c e n t a g e s a re
l o c a t e d c l o s e to th e s o u r c e s , t h a t i s , th e m a r g in a l a r e a s .
F ig u r e 23. Heavy m in e r a l w e ig h t p e r c e n t s a r e
c o n to u r e d . N ote t h a t t h e h i g h e s t
p e r c e n t a g e s o c c u r n e a r th e m a r g i n a l
( s o u r c e ) a r e a s .
133
'0 -6.
HEAVY MINERAL
WEIGHT PERCENT
LAYER A,
C lay M in e ra lo g y
134
G e n e ra l
Three c o re s a lo n g l i n e 4, 4R3, 4 , and 4L2, w ere
ch o sen t o d e m o n s tra te th e d i f f e r e n c e i n c la y m in e r a lo g y
b o th l a t e r a l l y and v e r t i c a l l y a c r o s s th e Laguna S a la d a
b a s i n • In o r d e r t o d i f f e r e n t i a t e betw een t h e c la y
m i n e r a l s a c r o s s t h e la g o o n b a s i n , i t was b e l i e v e d s u f
f i c i e n t to choose a sam ple from e a c h o f t h e m a r g i n a l a r e a s
a s w e l l a s a sam ple from th e c e n t e r t r a v e r s e .
R e s u l t s
U n t r e a t e d Sample A n a l y s i s : K a o l i n i t e and i l l i t e a r e i n d i -
o o
c a t e d i n a l l th e sam p les by r e f l e c t i o n s in th e 7A and 10A
o
r e g i o n s o f th e d i f f r a c t o g r a m s w h ile in th e a r e a above 10A
t h e v e ry b ro ad and d i f f u s e p e ak s s u g g e s t a s u b s t a n t i a l
p e r c e n t a g e o f m ixed l a y e r c l a y s . In g e n e r a l , h o w ever, th e
d i f f r a c t o g r a m s o f t h e sa m p le s on th e e a s t shown maxima
o o
n e a r 14A and th e w e s te r n sam p les n e a r 12A.
o o
E th y le n e G ly c o l T r e a t m e n t ; The 7A and 10A r e g i o n s a r e u n -
0 0 o
a f f e c t e d w h ile th e 14A and 12A a r e a s have s h i f t e d t o 17A.
H eated to 250° C f o r 12 H o u r s : A l l t r a c e s o f t h e p e ak s in
o
th e 17A r e g i o n have been e l i m i n a t e d w i t h a r e s u l t a n t i n -
O o
c r e a s e in t h e 10A p eak ; a s m a ll r e f l e c t i o n in th e 14a a r e a
o
was o b s e rv e d in a few s a m p le s . The 7A l i n e was u n a f f e c t e d .
135
H eated t o 550° C f o r 1 H o u r; W ith t h e e x c e p ti o n o f sam ple
o
4L2E, th e 7 A l i n e h a s d is a p p e a r e d c o m p le te ly . An i n c r e a s e
o c c u r r e d in th e number o f sam ples w i t h s m a ll p e a k s n e a r
o
14a •
D is c u s s io n
The d i f f r a c t o g r a m t r a c e s in n e a r l y a l l t h e u n
t r e a t e d sam ples e x h i b i t e d b ro a d and o c c a s i o n a l l y p l a t e a u -
o
l i k e p e ak s w i t h i n t h e 10A a r e a . T h is s u g g e s t s a v a r i e t y
o f m i x e d - l a y e r s t r u c t u r e s . A l l t h e g l y c o l a t e d sam ples
o
d e m o n s tr a te d a s h i f t t o th e 17A ra n g e w h ich i n d i c a t e s
t h a t th e m o n t m o r i l l o n i t e c la y s a r e p re d o m in a n t. C h l o r i t e s
and v e r m i c u l i t e s , in g e n e r a l , w i l l n o t ex p an d . However,
c e r t a i n s w e l l i n g c h l o r i e s and low c h a rg e d v e r m i c u l i t e s
a r e e x c e p ti o n s w hich r e q u i r e th e a p p l i c a t i o n o f more
d e f i n i t i v e t e c h n i q u e s to d i f f e r e n t i a t e them from th e
m o n t m o r i l l o n i t e s . Many o f th e sa m p le s e x h i b i t e d r e f l e c -
o
t i o n s in th e 14A a r e a a f t e r h e a t t r e a t m e n t t o 550° C w hich
may i n d i c a t e th e p r e s e n c e o f s w e l l i n g c h l o r i t e s b u t u n
l e s s a c o n s t a n t h u m id ity d e v i c a i s u se d to p r e v e n t th e
r e h y d r a t i o n o f th e m o n t m o r i l l o n i t e s , i t i s n o t p o s s i b l e
t o d i f f e r e n t i a t e betw een them . A c o n s t a n t h u m id ity d e
v i c e was n o t a v a i l a b l e , so t h i s p ro c e d u re c o u ld n o t be
u s e d . Even th o u g h d e f i n i t i v e t e s t s w ere n o t p e rfo rm e d ,
s w e l l i n g c h l o r i t e s a r e e x tr e m e ly r a r e and i t i s assumed
t h a t th e y a r e n o t p r e s e n t . On th e o t h e r h a n d , d e t e c t i o n
13 6
o f th e low c h a rg e d v e r m i c u l i t e s r e q u i r e s p r e t r e a t m e n t w i t h
t O
1 Mg w hich p r e v e n t s t h e i r e x p a n s io n i n t o t h e 17A r e g i o n
when g l y c e r o l * i s added (W a lk er, 1 9 5 8 ). Assuming t h a t
i
i
: n o rm a l c h l o r i t e s and v e r m i c u l i t e s a r e a b s e n t , r e f l e c t i o n s
! O
- in th e 14A r e g i o n would i n d i c a t e t h e p re s e n c e o f th e low
I c h a rg e d v e r m i c u l i t e s . I t i s b e l i e v e d t h a t th e d i f f e r e n c e
betw een th e m o n t m o r i l l o n i t e s and th e v e r m i c u l i t e s i s , a t
b e s t , an a r b i t r a r y one and may r e p r e s e n t a d i f f e r e n c e in
| l a y e r c h a rg e o n ly (W a lk er, 1 9 6 1 ).
i
j I f m o n t m o r i l l o n i t e s a r e th e p re d o m in a n t c la y
j m i n e r a l s in th e Laguna S a l a d a , i t i s th e n p o s s i b l e t o d i f -
| f e r e n t i a t e betw een th e e a s t e r n and w e s te r n m a r g in s . De-
I
! s p i t e th e f a c t t h a t th e d i f f r a c t i o n peaks a r e b r o a d , th e y
t o o
| g e n e r a l l y peak in th e 1 4 . 5A and 1 5 . 5A r e g i o n s f o r th e
o o
| e a s t e r n sa m p le s and betw een 12A and 13A f o r th e w e s te r n
s a m p le s . A d i f f e r e n c e o f c a t i o n in th e m o n t m o r i l l o n i t e
j s t r u c t u r e may be a l l t h a t i s i n d i c a t e d s i n c e McAtee (1956)
; r e p o r t e d t h a t W a -m o n tm o rillo n ite s c o n ta in o n ly one l a y e r
o
; o f w a t e r r e s u l t i n g i n a (001) s p a c in g o f 1 2 . 4A w h ile
C a - m o n t m o r i l l o n it e s c o n ta in a d o u b le l a y e r t h a t p ro d u c e s
o
; a (001) s p a c i n g o f 1 5 . 4A. MacEwan (1961) a l s o s t a t e d
! t h a t :
C a - m o n t m o r i l l o n it e s te n d t o be more h i g h l y
h y d r a te d th a n N a - m o n t m o r il l o n it e s a t a l l p r e s s u r e s .
A lth o u g h c l i m a t e , w e a t h e r i n g , and ro c k ty p e have been
i
! shown to c au se d i f f e r e n c e s in c la y m in e r a lo g y , th e f i r s t
j two f a c t o r s have u n d o u b te d ly p la y e d a s m a ll r o l e in such
I
j a n a rro w and c o n fin e d d r a in a g e a r e a a s t h e Laguna S a l a d a .
! I t i s more d i f f i c u l t to e l i m i n a t e th e p o s s i b i l i t i e s o f
i
f
' r o c k ty p e d i f f e r e n c e s due to th e f a c t t h a t r e l a t i v e l y
i
l i t t l e m apping h a s been a c c o m p lish e d i n t h e S i e r r a de l o s
I
! O ucapas. P r e l i m i n a r y e x a m in a tio n s by g r a d u a t e s t u d e n t s
a t San Diego S t a t e C o lle g e , and th e m i n e r a l o g l e s tu d y o f
th e sa n d s from th e e a s t e r n and w e s te r n m a r g in s , s u g g e s t
t h a t t h e r e a r e few d i f f e r e n c e s betw een th e P e n i n s u l a r
; Eange and th e C u c ap a s. The a u t h o r c o n c lu d e s t h a t t o p o -
j g r a p h i c v a r i a t i o n s b etw een th e e a s t e r n and w e s te r n la g u n a
i
m a rg in s c o n t r i b u t e to t h i s d i f f e r e n c e in c la y m in e r a lo g y .
A t o p o g r a p h ic d e p r e s s i o n o c c u p ie s th e e a s t e r n s i d e o f th e
; b a s i n so t h a t i n tim e s o f f lo o d t h e w a t e r s c o l l e c t in th e
! e
j d e p r e s s io n and rem ain u n t i l e v a p o r a t i o n i s c o m p le te . In
1 a d d i t i o n , s p r i n g s a lo n g th e Laguna S a la d a f a u l t a s w e ll
! a s a h i g h w a te r t a b l e p ro v id e a d d i t i o n a l w a t e r s w hich keep
i t in an a lm o s t c o n s t a n t ”w e tM c o n d i t i o n .
MICROFAUUA
j The m arin e b i o c l a s t s o f th e Laguna S a la d a s e d im e n ts
, i
i c o n s i s t o f t e s t s o f g a s t r o p o d s , o s t r a c o d e s , d ia to m s , and
j !
| f o r a m i n i f e r a . O s tr a c o d e s and g a s t r o p o d s c o n s t i t u t e an ■
| a lm o s t u n i v e r s a l component in th e c o l l e c t e d sa m p le s , I
I i
| w h e re a s th e d ia to m s a r e a b u n d a n tly p r e s e n t in o n ly a few j
! s a m p le s , n o t a b l y 7E» fh e f o r a m i n i f e r a l p o p u l a t i o n , j
i
p ic k e d and m ounted by th e a u t h o r , was i d e n t i f i e d by D r.
■ 0 . L. Bandy o f th e D epartm ent o f G eology, U n i v e r s i t y o f
| S o u th e rn C a l i f o r n i a . S e p a r a t i o n o f th e f o r a m i n i f e r a l
p o p u l a t i o n s o f S o u th e rn C a l i f o r n i a and th e G u lf o f C a l i - ;
|
f o r a i a i n t o d e p o s i t i o n a l p a r a l i c e n v iro n m e n ts by Bandy 1
i
i
j (1963) p r o v i d e s th e b a s i s f o r th e d i s c u s s i o n o f th e
■ s p e c i e s p r e s e n t in th e Laguna S a l a d a . Only one o f th e !
1 |
te n g e n e ra l i s t e d i n t h e la g o o n a l b i o f a c i e s , ammonia
: b e c c a r i i t e p i d a . o c c u r s in t h e s tu d y a r e a . The s p e c i e s
j
r e p r e s e n t s th e b u lk o f t h e f o r a m i n i f e r a l p o p u l a t i o n .
M i l l i o l i d s r e p r e s e n t i n g th e b e a c h b i o f a c i e s , B u l i m i n e l l a
e l e g a n t i s s i m a and H anzaw aia n i t i d u l a . form th e u p p e r s u b -
i l i t t o r a l ( i n n e r s h e l f ) b i o f a c i e s , and B u lim in a m a r g i n a t a
1
j d e n u d a ta ( ? ) and E lp h id iu m s p p . t h e c o s m o p o lita n b i o f a c i e s ,
; a l l i n d i c a t e th e d i v e r s i t y o f th e f a u n a . The d i v e r s i t y
c o u p le d w i t h th e p r e s e n c e o f p l a n k t o n i c f o r a m i n i f e r a
< ( g l o b i g e r i n i d s ) and p te r o p o d s s u b s t a n t i a t e th e c o n c e p t o f
1
a p e r i o d i c c o n n e c tio n w i t h th e G u lf o f C a l i f o r n i a .
139
B ecause o t h e r e v id e n c e h a s s u p p o r te d th e p r e s e n c e
; o f a body o f w a t e r when th e s e d im e n t i n l a y e r ,fE ft was
! d e p o s i t e d , a f o r a m i n i f e r a l c o u n t p e r 5-gm sam ple o f th e
| s u r f a c e l a y e r f,AH and th e b otto m l a y e r f,EH was made. The
j r e s u l t s c o n to u re d in P i g s . 24 a, b , c i l l u s t r a t e t h r e e
I
! s i g n i f i c a n t d i f f e r e n c e s betw een th e two l a y e r s :
1 . A s h i f t in th e a r e a s o f l a r g e c o n c e n t r a t i o n o f
f o r a m i n i f e r a to w a rd th e s o u th e r n end o f th e
b a s i n .
2. A s i g n i f i c a n t l y h i g h e r num ber o f f o r a m i n i f e r a
! in t h e a r e a s o f c o n c e n t r a t i o n in l a y e r " E " .
3 . A l a r g e r num ber o f sam ples in l a y e r **A ,f w i t h
no f o r a m i n i f e r a p r e s e n t .
i
! E x a m in a tio n o f l a y e r s A - ^ and A2 in P i g s . 2 4a, b
| i l l u s t r a t e s th e c o r r e l a t i o n betw een th e a r e a s o f h ig h
i
| f o r a m i n i f e r a c o n c e n t r a t i o n s and th e t o p o g r a p h i c d e p r e s s io n
! a lo n g th e e a s t e r n m a r g in . In c o n t r a s t th e f o r a m i n i f e r a
c o n c e n t r a t i o n s in l a y e r nE,f a r e f a r t h e r s o u t h . The a p -
i
; p a r e n t s h i f t may i n d i c a t e a change in th e to p o g r a p h i c
c o n t o u r s , b u t i t i s more l i k e l y an i n d i c a t i o n o f th e d i f -
I f i c u l t y in d e te r m i n i n g a “t r u e " s u r f a c e o f a c c u m u la tio n .
i
A s tu d y o f th e i n t e r v e n i n g l a y e r s f,BH, f,0 ,f, and (,DH would
be n e c e s s a r y t o d e te r m in e th e c o n s i s t e n c y o f t h e f o r a -
| m i n i f e r a c o n c e n t r a t i o n s a s w e l l a s t o h e lp in th e d e t e r -
I
m in a tio n o f th e s u r f a c e o f a c c u m u la tio n .
The p r e s e n c e o f f o r a m i n i f e r a i n h i g h e r num bers an d,
F ig u r e 2 4 a . C o n to u rs o f th e num ber o f f o r a
m i n i f e r a p e r 5 g® sam ple f o r
l a y e r “A".
141
i n '
NO. OF FORAMS PER 5 GM. SAMPLE
A, - LAYER
CONTOUR INT
F ig u r e 24b, C o n to u rs o f t h e number o f f o r a -
m i n i f e r a p e r 5 gm sam ple f o r
l a y e r " C " •
143
60'
NO. OF FORAMS PER 5 GM. SAMPLE
A0 - LAYER
CONTOUR INT
F ig u r e 24 c, C o n to u rs o f th e number o f f o r a -
m i n i f e r a p e r 5 gm sam ple f o r
l a y e r HE ". The a r e a o f h i g h f o r a -
m i n i f e r a c o n c e n t r a t i o n h a s s h i f t e d
to th e s o u t h . N ote a l s o th e i n
c r e a s e in th e num ber o f sam p les
c o n t a i n i n g f o r a m i n i f e r a .
145
too
«n
< N
50
NO. OF FORAMS PER 5 GM. SAMPLE
E - LAYER
CONTOUR INT 2N
i 146
w i t h few e x c e p t i o n s , in a l l th e sam ple l o c a t i o n s in th e
; “E1 * l a y e r s u p p o r t s th e c o n c l u s i o n t h a t a more e x t e n s i v e
!
| f l o o d i n g o f th e Laguna S a la d a o c c u r r e d d u r in g th e
i
| d e p o s i t i o n o f th e bo tto m sam ple l a y e r .
i
I
SUMMARY AND CONCLUSIONS
The Laguna S a la d a , in a c c o rd a n c e w i t h th e c l a s s i f i
c a t i o n p r e s e n t e d by S to n e (1956) i s a compound p l a y a . The
s o f t spongy s u r f a c e s t y p i c a l o f m o is t p l a y a s , how ever,
were c o n s i d e r a b l y more a b u n d a n t. Only o c c a s i o n a l l y was
th e sm ooth, h a r d , mud c ra c k e d a r e a s a s s o c i a t e d w ith
t y p i c a l d ry p l a y a s e n c o u n te r e d . A summary o f th e
i
I c h a r a c t e r i s t i c s o f th e s tu d y a r e a a r e l i s t e d a n d , where
|
a p p l i c a b l e , a co m pariso n w ith th e c h a r a c t e r i s t i c s o f th e
t y p i c a l p la y a s d e s c r i b e d by S to ne w i l l be made.
1. S edim ent t y p e s a r e p re d o m in a n tly f i n e - g r a i n e d .
S i l t y c la y s a re p red o m in a n t a t a l l d e p th l e v e l s w ith th e
im p o rta n c e o f c la y e y s i l t s i n c r e a s i n g and s a n d - s i l t - c l a y s
d e c r e a s i n g w i t h d e p th . The s e d im e n t t y p e s o f 40 d i f f e r e n t
p l a y a s , p r e s e n t e d i n a t r i a n g u l a r d iag ra m by S to n e , i l
l u s t r a t e s th e same c h a r a c t e r i s t i c s where 44 o f th e 70
sam p les a r e s i l t y c l a y s , 16 c la y e y s i l t s , and 6 s a n d - s i l t -
c l a y s .
2. The a v e r a g e g r a i n s i z e in t h e Laguna S a la d a
becomes f i n e r w i t h d e p th . A mean d i a m e te r o f 6 .8 0
( 9 .8 m ic ro n s) f o r l a y e r H Afl, 7 . 4 0 ( 6 .2 m ic ro n s ) f o r l a y e r
f,Cn , and 7 .7 0 ( 5 .0 m ic ro n s ) f o r l a y e r ,fE,f d e m o n s tr a te s
th e d e c r e a s i n g i n f l u e n c e o f th e san d s i z e d m a t e r i a l s .
D i r e c t c o m p a riso n s w ith th e a v e ra g e g r a i n s i z e o f 4
m ic ro n s p r e s e n t e d by S to n e c a n n o t be made due to th e d i f -
148
f e r e n c e s in t h e m ethods o f c a l c u l a t i o n . The 4 m ic ro n s i s
g iv e n in te rm s o f m edian d ia m e te r w h ich i n a p re d o m in a n tly
f i n e - g r a i n e d s e d im e n t i s l e s s th a n th e mean d i a m e te r f o r
th e same f r e q u e n c y c u rv e (F rie d m a n , 1 9 6 1 ).
3 . Poor s o r t i n g i s c h a r a c t e r i s t i c o f a l l th e
sam ples c o l l e c t e d in th e Laguna S a la d a a n d , a c c o r d i n g to
S to n e , c h a r a c t e r i s t i c o f a l l p l a y a s . S o r t i n g , how ever, i s
r e l a t i v e l y b e t t e r w ith d e p th . A verage v a lu e s f o r l a y e r
“A ", " 0 " , and ffEff a r e 3 .0 0 , 2 .4 0, and 2 .3 0 , r e s p e c t i v e
ly*
4. A d e c l i n e o f th e p o s i t i v e and h i g h l y n e g a t i v e
skew ness v a l u e s o c c u rs w i t h d e p th due to th e g r a d u a l
d i s a p p e a r a n c e o f th e c o a r s e m a t e r i a l s . S i l t y c l a y s ,
t h e r e f o r e ^ m o s t p la y a s e d im e n ts , a r e alw ays c h a r a c t e r i z e d
by n e g a t i v e skew ness v a l u e s . C layey s i l t s and s a n d - s i l t -
c l a y s e x h i b i t b o th n e g a t i v e and p o s i t i v e v a l u e s . The
m a j o r i t y o f t h e c la y e y s i l t s a r e n e g a t i v e and th e m a j o r i t y
o f th e s a n d - s i l t - c l a y s a r e p o s i t i v e . S in c e t h e s a n d - s i l t -
c la y s a r e t h e l e a s t common o f th e two se d im e n t t y p e s , one
can e x p e c t th e o v e r a l l m a j o r i t y o f th e p l a y a s e d im e n ts to
have n e g a t i v e skew ness v a l u e s .
5. The f r e q u e n c y d i s t r i b u t i o n c u r v e s a r e
c h a r a c t e r i s t i c a l l y b im o d a l ( p l a t y k u r t i c ) in t h e p la y a
s e d im e n ts . Unim odal ( l e p t o k u r t i c ) c u rv e s a r e uncommon
b u t when p r e s e n t th e y may i n d i c a t e p o s s i b l e s o u rc e
d i r e c t i o n s .
6. Calcium c a r b o n a te p e r c e n t a g e s ra n g e d from 3 .6
to 1 3 .7 p e r c e n t w hich c o r r e l a t e s w ith th e 3 to 15 p e r
c e n t v a l u e s f o r th e m o is t p l a y a s sam pled by S to n e ,
[ 7 , V a lu es f o r th e o r g a n i c c arbo n c o n te n t ra n g e d
|fro m t r a c e s to 0 ,8 0 p e r c e n t and a v e ra g e d 0 .1 4 p e r c e n t .
jThe p e r c e n t a g e s c i t e d by S to n e were 0 .0 8 to 1 .5 p e r c e n t
.1
|w i t h an a v e ra g e o f 0 .3 p e r c e n t .
j 8 . Q u a rtz and f e l d s p a r s a r e th e dom inant l i g h t
I
|m i n e r a l s in th e c o a r s e f r a c t i o n s . The f e l d s p a r s , p l a g i o -
!
j c l a s e and o r t h o c l a s e a r e r e l a t i v e l y f r e s h and a b u n d an t
a n d , a lo n g w i t h th e dom inant h e a v i e r m i n e r a l s b i o t i t e ,
jh o r n b le n d e , and a u g i t e , c o n firm t h a t th e g r a n i t i c m asses
|t o th e w e s t and e a s t o f th e b a s i n , S i e r r a J u a r e z and
j
S i e r r a de l o s C u cap as, r e s p e c t i v e l y , s u p p l i e d th e b u lk o f
!th e c o a r s e m a t e r i a l s .
i
i 9 . K a o l i n i t e s , i l l i t e s , and m ixed l a y e r c l a y s w ith
ia p r e d o m in a n tly m o n t m o r i l l o n i t e s t r u c t u r e c o n s t i t u t e th e
m a j o r i t y o f th e c la y m i n e r a l s .
. 10. The f a u n a l p o p u l a t i o n c o n s i s t s o f g a s t r o p o d s ,
o s t r a c o d e s , d ia to m s , and b e n th o n ic and p l a n k t o n i c f o r a -
m i n i f e r a . O s tra c o d e s and g a s tr o p o d s a r e common to a l l
'sa m p le s w h ile th e f o r a m i n i f e r a s and d ia to m s a r e l o c a l l y
a b u n d a n t. In th e 40 p l a y a s s t u d i e d by S to n e , o n ly 7 con
t a i n e d i n v e r t e b r a t e f o s s i l s . G a s tr o p o d s , p e le c y p o d s , and
o s t r a c o d e s were c i t e d b u t o n ly th e p e le c y p o d s w ere co n
s i d e r e d common. The a b u n d an t f a u n a l p o p u l a t i o n i n c l u d i n g
I 150
t h e p l a n k t o n i c s a t t e s t to th e d i f f e r e n c e s betw een th e
: p a r t i a l l y m arin e Laguna S a la d a and t h e ‘‘n o r m a l” p l a y a
1
; s e d i m e n t s .
!
1
| The summary c o n firm s t h a t , in te rm s o f se d im e n t
|t y p e , a v e ra g e s i z e , s o r t i n g , and skew ness t h e Laguna
1
|S a l a d a s e d im e n ts a r e d i f f i c u l t to d i s t i n g u i s h from th e
j t y p i c a l p la y a s e d im e n ts d e s c r i b e d by S to n e . V e r t i c a l
i v a r i a t i o n s w i t h i n th e p a r a m e t e r s , a v e ra g e s i z e , s o r t i n g ,
|s k e w n e s s , and c a lc iu m c a r b o n a te c o n t e n t , a c c o r d i n g to
i S to n e , showed no d e f i n i t e t r e n d s . In th e Laguna S a la d a ,
:h ow ever, r e l a t i v e l y c o n s i s t e n t v a r i a t i o n s w ith d e p th do
i
! o c c u r w i t h i n th o s e p a r a m e t e r s . The c o n d i t i o n w hich caused
th e d i f f e r e n c e s in v e r t i c a l v a r i a t i o n s , c o l o r , and f a u n a l
p o p u l a t i o n betw een th e Laguna S a la d a and th e t y p i c a l
| p l a y a s a re p ro b a b ly due t o p e r i o d i c a l t e r n a t e in u n d a
t i o n s o f m arin e and f r e s h w a t e r s a lo n g w i t h an i n c r e a s e in
; th e r a t e o f t e c t o n i c a c t i v i t y a lo n g th e m a r g in s , e s p e c i a l -
1
j l y th e e a s t e r n m a rg in .
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h i s t o r y o f B a ja C a l i f o r n i a and i t s m arin e f a u n a s :
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P o s t e r , M. D ., 1951* Magnesium and c a t i o n exchange in
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1 and r i v e r sand from t h e i r t e x t u r a l c h a r a c t e r i s t i c s :
| J o u r . S e d . P e t r o l o g y , v . 31, pp. 514— 529.
G o r s l i n e , D. S . , 1954-. S e d im e n ta tio n in S e b a s t i a n V is -
I c a in o Bay and v i c i n i t y , B a ja C a l i f o r n i a , M exico:
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| f o r a i a , u n p u b l. M a s te r* s t h e s i s , 96 p p .
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and w a t e r l o s s i n t h e lo w e r C olorad o R i v e r - S a l t o n Sea
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B l6 .
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1 J a h n s , R. H ., 1954. I n v e s t i g a t i o n s and p ro b lem s o f
i s o u th e r n C a l i f o r n i a g e o lo g y : C a l i f . D e p t. N a t. R e s . ,
D iv. M ines B u l l . 170, p t . 1 , ch. 1, pp. 5 -2 9 .
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s e d im e n ta r y p e t r o g r a p h y : A p p l e to n - C e n tu r y - C r o f t s ,
I n c . , New Y ork, 549 pp.
i
L o n g w ell, C. R . , 1954. H i s t o r y o f th e lo w e r C olo rado
R iv e r and th e I m p e r i a l d e p r e s s i o n : C a l i f . D e p t. N a t.
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L u s t i g , L. K . , 1965* C l a s t i c s e d i m e n ta t io n in Deep
1 S p r in g s V a l l e y , C a l i f o r n i a : U. S. G e o l. S urvey P r o f .
1 P a p e r 3 5 2 -F , pp. 1 3 1 -1 9 2 .
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D e lta : Amer. G eo g rap h . S oc. B u l l . , v . 39» pp. 70 5 -
729.
i
MacEwan, M. C . , 1961. M o n tm o r illo n ite m i n e r a l s : The
x - r a y i d e n t i f i c a t i o n and c r y s t a l s t r u c t u r e s o f c la y
m in e r a l s (Brown, G ., e d . ) : M i n e r a l o g i c a l S o c i e t y ,
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i n t e r s t r a t i f i c a t i o n i n m o n t m o r i l l o n i t e : Am.
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1 5 4
M erriam , R. and Bandy, 0 . L . , 1965* S o u rce o f Upper
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Sed. P e t r o l o g y , v . 35$ p p. 9 1 1 -9 1 6 .
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158.
S to n e , R. 0 * , 1956. A g e o lo g ic i n v e s t i g a t i o n o f p la y a
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1
1_____ , 1961. V e r m i c u li t e m i n e r a l s : The x - r a y i d e n t i -
| f i c a t i o n and c r y s t a l s t r u c t u r e s o f c la y m i n e r a l s
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1
W oodring, W. P . , 1931. D i s t r i b u t i o n and age o f th e
! T e r t i a r y d e p o s i t s o f t h e C olo rad o D e s e r t: C a rn e g ie
I n s t . W ash., P u b l. 148, pp. 1 -2 5 .
APPENDICES
APPENDIX I
SEDIMENTARY CHARACTERISTICS
OP LAYERS “A1 1 , “ C", AND M EM
L a y e r "A1 1 ( 0 to 1 1 )
Sample
No.
Sa S i
........% ......
Cl
%
Md
(0)
So Sk Ku
1A06
4 5 .7 3 2 9 .9 6 2 4 .3 1 4 .8 6
3 .5 9 .1 5
- 1 .0 6
1A612
1 6 .7 9 65 .4 7
1 7 .7 4 5 .6 4
2 .3 7 .35
.0 4
2A 1 1 .7 6 41 .1 3 4 7 .1 1 7 .3 1
3 .0 0 - .7 0 - .26
2R1A 7 .7 3 3 6 .9 9
55 .2 8 8 .0 3 2 .5 7 - .89 .09
2R2A 4 .3 8
7 3 .0 3 2 1 .5 9
6 .2 2 2 .3 2
.57 - .22
2L1A 1 9 .9 2 2 2 .0 0 5 7 .0 8 7 .6 0
3 .1 9 - .87
- .60
2L2A 5 0 .7 6 2 7 .6 0 2 1 .6 4 5 .0 4
3 .0 5 .63 - .9 6
3A 1 6 .9 8 5 3 .6 2 2 9 .4 0 6 .2 0 2 .8 2 .11 - .82
3R1A 1 .4 3 3 9 .9 0 5 7 .6 7 8 .4 7 2 .0 3 - .6 8 - .1 0
3R2A 1 4 .8 6 2 3 .2 4 6 1 .9 0 8 .0 1 2 .9 2 - 1 . 0 2
- .23
3L1A06
2 5 .3 7 3 2 .9 9
4 1 .6 4
6 .7 5
3 .0 8 - .2 2
- 1 .3 3
3L1A612 3 0 .3 0
3 0 .7 3 3 8 .9 7 6 .5 1 3 .2 3 - .07 - 1 .4 7
3L2A07
4 0 .4 6 3 4 .5 8 2 4 .9 6 5 .5 4
2 .9 9 .39
- 1 .0 1
3L2A712 8 .0 7 4 9 .9 7
4 1 .9 6
7 .2 7 2 .5 9
- .21 - .9 0
4A04 2 2 .9 8 3 2 .6 8 4 4 .3 4 6 .8 8 3 .3 6
- .5 5 - .93
4A412 7 .7 4
2 9 .3 5 6 2 .9 1
8 .3 4 2 .6 8 - 1 .6 0
2 .3 7
4R1A06
1 7 .0 3
3 2 .3 0
5 0 .6 7 7 .3 6 3 .2 2 - .7 4 - .68
4R1A612
5 .2 7 3 6 .6 3 5 8 .1 1 8 .2 4 2 .4 3 - 1 .0 3 .71
4R2A 9 .3 0 3 4 .2 4 5 6 .4 6
8 .0 3 2 .7 3
- 1 .2 0
.87
4R3A09 2 7 .8 4 4 8 .9 4 2 3 .2 2 5 .4 8 3 .1 6
- .07 - .7 4
SEDIMENTARY CHARACTERISTICS
OP LAYERS "A", f,CH, AND flEff (C o n tin u e d )
L a y e r 1 1 A” ( 0 t o l f )
Sample
Ho.
Sa
. . . . % .....
S I
%
Cl
%
Md
(0)
So Sk Ku
4R3A912 1 1 .5 8 5 8 .3 8 3 0 .0 4 6 .5 3 2 .8 1
- .2 5 - .25
4L1A07
2 5 .6 0 3 5 .3 6 3 9 .0 4
6 .5 7 3 .0 7 - .0 9 - 1 . 3 4
4L1A712 1 7 .1 0 4 6 .8 5 3 6 .0 5 6 .5 7 3 .0 3 - .1 5
1
H
•
O
O
4L2A08 2 .0 0 2 2 .6 0 7 5 .4 0 9 .0 2 1 .8 8
- 1 .4 9
2 .1 2
4L2A812 8 .0 6 2 2 .1 1
6 9 .8 3
O
V O
•
00
2 .4 2 - 1 . 2 4 .52
4L3A 5 4 .3 0 2 2 .9 6 2 2 .9 4 4 .2 8 3 .8 0
.2 5
1
H
•
O
H
5A04 2 6 .8 6 3 4 .1 6 3 8 .9 8 6 .5 3
3 .3 8 - .2 8 - 1 . 2 4
5A412
8 .6 3
3 6 .7 2
5 4 .6 5 7 .9 5 2 .6 5 - .91 .11
4R1A 1 2 .7 0
2 6 .5 5 6 0 .7 5
8 .0 6 2 .9 6 - 1 . 2 4 .56
5E2A04 3 0 .5 4
3 4 .7 3 3 4 .7 3 6 .1 5 3 .2 9 - .1 0
- 1 .2 5
5R2A412 2 0 .1 6 4 5 .4 2 3 4 .4 2
6 .5 1
3 .2 0
O
•
1
- .6 0
5E3A 1 1 .4 3 3 5 .1 7
5 3 .4 0 7 .7 1
2 .9 4 - 1 .1 1 .62
5E4A06 53.63 1 8 .8 7
2 7 .5 0 4 .5 2
3 .9 1 .2 7 - 1 .4 7
5E4A612
4 6 .9 3
1 9 .0 1 3 4 .0 6
5 .3 3 3 .8 5 .09
- 1 .6 0
5L1A06 8 .9 6 3 1 .9 6 5 9 .0 8
8 .0 5
2 .6 4
- .89
1
•
H
V O
5L1A612 1 8 .8 6
3 6 .2 7 4 4 .8 7
7 .1 4 3 .0 2 - .42
H
O V
•
1
5L2A05
8 6 .6 4 7 .3 0 6 .0 6 3 .4 3 1 .9 8 2 .1 8 5 .5 2
5L2A512 7 5 .6 6
1 8 .4 3 5 .9 1 3 .7 3
1 .8 1 1 .7 8 4 .2 7
6A
8 .5 9
3 7 .2 8
5 4 .1 3 7 .9 1 2 .6 3 - .7 6 - .33
6R1A08 3 .8 1 3 9 .2 1 5 9 .9 8 8 .3 6
2 .3 7
- 1 .2 6
1 .7 7
159
SEDIMENTARY CHARACTERISTICS
OP LAYERS "A” , w CM f AND "E" (C o n tin u e d )
L a y e r "A” (0 to 1 ! )
Sample
Ho.
Sa
%
S I
. %......
Cl
.%
Md
(0 )
So Sk Ku
6R1A812
1 .0 9 3 4 .5 9
6 4 .3 2
8 .7 5
1 .9 4 - 1 . 1 4 1 .9 6
6R2A08 2 4 .2 1
3 8 .1 9 3 7 .6 0 6 .5 8 3 .2 4
- .31 - .9 8
6R2A812 8 .6 2
4 8 .0 3 4 3 .3 5 7 .4 2 2 .7 6 - .75 .3 5
6R3A06 8 .3 2 6 0 .4 5
3 1 .2 3 6 .8 0 2 .5 2 .0 4 - .7 0
6R3A612 8 .8 6 5 4 .9 8 3 6 .1 6
6 .9 9
2 .8 4
- .5 5 .09
6I1A010 2 0 .9 0
2 4 .3 9 5 4 .7 1 7 .4 6 3 .2 6 - .70 - .9 1
6L1A1012
3 1 .9 1
2 6 .4 2
4 1 .6 7
6 .7 0
3 .5 1
- .4 1 - 1 .0 8
6L2A09 7 7 .1 2 1 3 .9 2 8 .9 6
2 .9 9
2 .9 8
.91 .83
6L2A912 7 3 .9 2 1 4 .0 4 1 2 .0 4 3 .3 0 3 .1 8 .98 .43
7A
2 3 .5 3 2 7 .5 5
4 8 .9 2 7 .2 1
3 .1 5 - .5 4 - 1 .0 4
7E1A08 3 2 .8 5 3 0 .5 3
3 6 .6 2 6 .3 6 3 .2 1 .0 2 - 1 .4 2
7R1A812 24 .8 8
2 8 .3 9 4 6 .7 3 6 .9 2
3 .3 3
- .3 6
1
|_ _ J
•
ro
0
7R2A 2 2 .3 1
3 4 .6 1 4 3 .0 8
6 .9 5
3 .0 8 - .2 6 - 1 .3 2
7R3A 1 1 .0 4 5 7 .9 0 3 1 .0 6
6 .7 5
2 .8 0
- .53
.28
711A 8 .2 0 2 6 .1 0 6 5 .7 0 8 .4 4 2 .4 7 - 1 .4 2
1 .5 7
7L2A 5 3 .6 9 1 6 .8 5
2 9 .4 6
5 .3 5
3 .4 0 .4 4 - 1 .3 4
8A 1 5 .2 9 3 5 .6 5 4 8 .0 6 7 .3 4
2 .8 9 - .33
- 1 . 2 4
160
SEDIMENTARY CHARACTERISTICS
OP LAYERS "A", "C", AND "E" (C o n tin u e d )
L a y e r "C" ( 2 to 3 ' )
Sample
No.
Sa
%
S i Cl
...._ %
Md
(0)
So Sk Ku
1C 2 .4 1 4 0 .3 0 5 7 .3 0 8 .2 9 2 .2 2 - .47 - 1 .1 9
20 0 .0 8 3 8 .9 0 6 1 .0 2 8 .4 7
2 .1 6 -
.59 - 1 .0 7
2R1C 0 .4 5 2 8 .4 4 7 1 .1 1 8 .9 6 1 .8 2 - .92 - .2 6
2R2C 1 .1 6 7 1 .9 8 •2 6 .8 6 6 .7 0
2 .1 7 .80 - .8 6
2L1C06 4 3 .8 4
1 7 .7 1 3 8 .4 5 5 .7 4
3 .8 5
.06
- 1 .5 9
2L1C612
3 4 .5 9 1 8 .7 9
4 6 .6 1
6 .5 1
3 .7 4 - .28 - 1 .4 7
2L2C 1 6 .7 3 6 3 .7 8 1 9 .4 7 5 .1 6 3 .2 8 - .30 .03
30 4 .0 2 6 1 .3 4 3 4 .6 4
6 .7 7
2 .7 4 - .2 6 .03
3R1C 1 .8 1
7 0 .3 5
2 7 .8 4 6 .8 1 2 .1 4
.69 - .91
3R2C 1 .3 7 2 2 .8 7
7 5 .7 6 9 .0 6 1 .8 2 -1 .2 1 .6 6
3L1C 4 .2 2
4 9 .3 3
4 6 .4 5 7 .6 1
2 .6 5
- .6 0 - .02
3L2C 0 .4 2
4 6 .9 3 5 2 .6 5
8 .1 0
2 .1 9
- .2 1 - 1 .4 7
4C 0 .0 2 4 0 .6 4 5 9 .3 4
8 .4 7 1 .9 7
- .3 4
- 1 .3 9
4R1C 0 .0 8 5 2 .8 0 4 7 .1 2 7 .5 6 2 .2 3
.1 4 - 1 .5 6
4R2C 0 .0 9 3 9 .1 2
6 0 .7 9
8 .5 2 2 .0 5 - .52 - 1 .1 1
4R3C 0 .4 1 5 9 .2 5 4 0 .3 4 7 .5 4 2 .1 9
.2 6 - 1 .4 7
4L1C 3 .8 8
5 1 .7 7 4 4 .3 5 7 .4 7 2 .4 7 .03 - 1 .5 7
4L2C04
3 2 .9 3 2 8 .8 9
4 4 .1 8 6 .5 4 3 .5 9
- .2 0 - 1 .4 8
4L2C412
3 2 .5 3 2 3 .5 4 4 3 .9 4 6 .5 2 3 .5 7
-
.1 5 - 1 .4 9
5C05 1 .1 1 3 1 .0 1 6 7 .8 8 8 .8 4 1 .8 8
—
.8 6 - .3 2
161
SEDIMENTARY CHARACTERISTICS
O R LAYERS "A", "C", A M D "E" (C o n tin u e d )
L a y e r "C" ( 2 t o 3 ' )
Sample
No.
Sa
........... % .
S i
%
Cl
%
Md
(0)
So Sk Ku
5C512 0 .5 6 3 8 .3 0 6 1 .1 4 8 .5 2 2 .0 2 -
.55 -1 .0 3
5R1C 0 .1 6 48. 58 5 1 .2 8
7 .9 9
2 .2 2 - .18 - 1 .4 9
5R2C
1 .0 7 3 1 .7 5
6 7 .1 8 8 .8 0 1 .9 2 - .8 6 - .32
5R3C 2 .4 2 3 2 .4 0 6 5 .1 8 8 .7 2 1 .9 4 - .8 0 - .37
5R4C 0 .6 9 4 0 .3 6
5 8 .9 5 8 .4 3 2 .0 4 - .4 4 - 1 .1 8
5L1C
3 .9 5
6 6 .3 6 29 .6 9 6 .6 3 2 .6 3
- .22 .42
5L2C 5 9 .7 2 3 1 .6 9 8 .5 9 4 .0 6 2 .1 9 1
.5 5 2 .4 5
6C 4 .6 2 7 6 .1 1 1 9 .2 7 5 .7 9
2 .5 0 .2 4 1 .0 1
6R1C 0 .6 8
2 5 .0 7 7 4 .2 5 9 .1 7 1 .6 3
-
.99
.1 4
6R2C 0 .5 0 4 6 .0 9 53 .4 1 8 .2 4 2 .1 2 -
.2 7
- 1 .3 9
6R3C 0 .1 4
5 0 .7 1 4 9 .1 5 7 .9 9
2 .1 4 - .08
-1 .5 3
6L1C 0 .4 9 4 3 .3 4
5 6 .1 7 8 .4 0 2 .0 7
- .3 4
- 1 .3 7
6L2C 0 .7 3 5 9 .8 5
3 9 .4 1 7 .4 8 2 .2 4 .2 4
- 1 .4 9
7C04
2 3 .9 7 2 2 .3 8
5 3 .6 5
7 .3 4
3 .2 9
- .4 4 - 1 .4 0
7049 6 9 .4 8 1 3 .2 2 1 7 .3 0
3 .7 5
3 .3 4 1
.03 - .18
70912 3 1 .3 2 2 1 .4 5
47 .2 3 6 .6 3 3 .6 9
-
.31
- 1 .4 2
7R1C 2 .4 2 7 3 .6 2 23 .9 6
6 .69
2 .0 8 .8 1 - .62
7R2C06
2 3 .9 1
3 2 .1 4
4 3 .9 5
6 .8 2
3 .3 9
- .4 0 - 1 .1 2
7R2C612 2 1 .6 4
4 7 .8 9 3 0 .4 7 6 .0 3 3 .4 2 - .3 4 - .67
7R3C 0 .1 6 3 9 .4 7 6 0 .3 7
8 .6 1 1 .9 0
-
.4 4 - 1 .2 1
16a
SEDIMENTARY CHARACTERISTICS
OP LAYERS "A", "C", AND "E" (C o n tin u e d )
L a y e r "C" ( 2 t o 3 1)
Sample
N o*
Sa
............% _
S i
_ %
Cl
%
Md
W
So Sk Ku
7L1C07 2 .9 0 2 2 .1 2 7 4 .9 8 9 .0 1
2 .0 5
- 1 .8 0
3 .9 5
7L1079 1 0 .9 9 2 7 .9 1
6 1 .1 0
8 .1 7 2 .7 8 - 1 .0 8 .
ro
0
7L1C912 2 6 .2 0
2 4 .2 9 4 9 .5 1
7 .0 1 3 .4 1
- .39
- 1 .3 8
7L2C
3 8 .8 3
2 9 .7 4 3 1 .4 3 5 .9 0 3 .1 8 .32 - 1 .3 6
8C 5 .9 0 4 3 .6 0 5 0 .5 0 7 .8 2
2 .5 1 - .37 - 1 .1 6
I
I
163
SEDIMENTARY CHARACTERISTICS
OE LAYERS 1 1 A” , "CM , AND ,fEH (C o n tin u e d )
L a y e r 1 1 E" ( 4 to 5 1 )
Sample
No.
Sa
%
S I
%
Cl
i
Md
(eS)
So Sk Ku
1
IE 2 .7 2 3 0 .2 6 6 7 .0 2
8 .3 9
2 .2 1 - .78 - .53
2E
0 .0 3
3 4 .5 2 6 5 .4 5 8 .5 0 1 .9 9 - .63 - .87
2R1E 0 .1 1 2 7 .1 2
7 2 .7 7
8 .9 4 1 .8 2
- .91 - .32
2R2E 0 .4 4
6 7 .7 7 3 1 .7 9 6 .9 2 2 .2 1
.59
- 1 .2 1
2L1E
2 3 .3 5 2 1 .6 5
5 5 .0 0
7 .1 3
3 .7 2 - .8 0 - .69
2L2E 0 .2 8 3 0 .0 7 6 9 .6 7 8 .8 9 1 .9 1
- .96 - .28
3E 4 .2 6 7 8 .8 3 1 6 .9 1 5 .7 7
2 .0 0 1 .3 4 .47
3R1E 0 .2 4 6 8 .7 6 3 1 .0 0 6 .7 2 2 .2 4 .70 - 1 .0 8
3R2E09
0 .1 4
4 5 .4 5
5 4 .4 1
8 .2 3 2 .1 5
- .30
- 1 .3 9
3R2E912 0 .2 5 3 2 .4 3 6 7 .3 2 9 .0 7
1 .8 7
- 1 .1 2 - .12
3L1E 0 .8 9 4 0 .5 2
58 .5 9
8 .3 4 2 .1 4 - .49
- 1 .1 5
3L2E
0 .7 9 4 3 .2 3
5 5 .9 8 8 .4 1 2 .0 8 - .48 - .72
4E06 0 .1 3 6 0 .1 6 3 9 .7 1 7 .5 2 2 .1 0 .34 - 1 . 5 0
4E612 0 .2 0 6 2 .7 6 3 7 .0 4 7 .3 2 2 .0 8 .47 - 1 .3 3
4R1E 0 .1 5
3 7 .6 6
6 2 .1 9 8 .5 8 2 .0 1
- .55
- 1 .0 1
4R2E 0 .3 0 4 6 .2 4 5 3 .4 6 8 .1 6 2 .2 0 - .20
- 1 .5 9
4R3E 0 .7 2
5 4 .3 9 4 4 .8 9 7 .7 0 2 .4 1 - .20
- .79
4L1E 3 .0 6
6 6 .2 5 3 0 .6 9
6 .6 2 2 .4 1 .28 - .4 4
4L2E
2 3 .8 7
2 6 .0 1 5 0 .1 2 7 .2 2 3 .2 7 - .33
- 1 .4 6
5E
0 .3 7 6 1 .1 7 3 8 .4 6
7 .2 7 2 .2 5 .32 - 1 .4 6
164
I
| SEDIMENTARY CHARACTERISTICS
J
I
OP LAYERS "A", " C " , AND "E" (C o n tin u e d )
I
| L a y e r "E" ( 4 to 6 ' )
Sample
No.
Sa
%
S i
t
Cl
. .
Md
(0)
So Sk Ku
5R1B 0 .5 1
4 0 .4 2
5 9 .0 7 8 ,3 7
2 .2 0 — .47 - 1 .2 7
5R2E 0 .2 5 2 1 .9 2 7 7 .8 5 9 .1 3 1 .6 5 - 1 .0 2 .03
5R3E05
0 .2 8 3 9 .9 6 5 9 .7 6 8 .4 8 1 .9 8 - .4 0 - 1 .4 1
5R3E512 0 .4 5 4 9 .0 3 5 0 .5 2 7 .9 4 2 .2 0 - .1 6 - 1 .4 8
5R4E 3 .2 5 2 7 .1 8 6 9 .5 7
8 .3 4 2 .0 0 - .65 - .53
5L1E 1 .7 4 7 4 .5 0 2 3 .7 6 6 .1 2 2 .1 6 1 .0 9 - .36
5L2E 3 2 .4 9 5 6 .5 3
1 0 .9 8 5 .0 7 2 .1 9 1 .1 8 1 .3 0
6E
2 .5 5 5 9 .1 7
3 8 .2 8 6.9 8
2 .5 5 .33
- 1 .6 0
6R1B 0 .2 6 4 5 .3 0 5 4 .4 4 8 .2 0 2 .2 0 - .33 - 1 .4 2
6R2E 0 .2 4 5 2 .8 6 4 6 .9 0 7 .8 4 2 .2 4
- .05 - 1 .5 6
6R3E 0 .1 2 4 4 .6 8 5 5 .2 0 8 .3 3 1 .9 9 - .21 -1 .4 9
6L1E 0 .1 6 3 4 .5 3 6 5 .3 2 8 .7 7 1 .8 3
- .68 - .8 0
6L2E 1 .4 0
5 5 .4 5 4 3 .1 5 7 .4 9
2 .3 4 .1 0
- 1 .5 4
7E 2 6 .9 0 1 7 .7 0 5 5 .4 0
7 .3 5 3 .3 7
- .48 - 1 .3 4
7R1E 0 .2 5 5 9 .9 9
3 9 .7 6
7 .5 1 2 .1 5
.2 4
-1 .4 3
7R2E 1 .3 7
7 8 .0 8
2 0 .5 5 6 .2 5
1 .9 6 .98
- .37
7R3E
0 .1 5 4 2 .3 3 5 7 .5 2 8 .3 3
2 .0 6 - .38 - 1 .3 0
7L1E04 9 .9 6 2 5 .4 4 6 4 .6 0 8 .1 9
2 .6 1
- .9 1 - .3 6
7L1E46 2 4 .7 0 2 9 .6 0 4 5 .7 0 6 .8 9
3 .2 4
- .33
- 1 .2 4
165
SEDIMENTASY CHARACTERISTICS
OR LAYERS "A", "C", AND "E" (C o n tin u e d )
L a y e r "E" ( 4 to 5 ' )
Sample Sa S i Cl Md So Sk Ku
No. % i ......
. i...... (0) ...
7L1E612 4 .3 2
2 9 .5 7
6 6 .1 1 8 .4 8 2 .3 6
in
00
•
I
L A
•
1
7L2E
2 2 .5 5 5 1 .1 1
2 6 .3 4 6 .0 6
2 .6 3 .51
- .9 6
8B 7 .9 6 2 6 .5 7
6 5 .4 7 8 .5 0 2 .4 3 - 1 .0 8
.17
APPENDIX I I
PERCENTAGE OE QUARTZ, FELDSPARS, HEAVY MINERALS
ORGANIC CARBON, AND CALCIUM CARBONATE
Sample
Ho.
Q tz .
%
G ra in s
O r th .
%
G r a in s
P la g .
%
G ra in s
Hvy.
Min. %
W eight
CaCO^
%
Org.
O arb.
%
1A 5 8 .1
1 5 .5 2 0 .5
3 .0 - *
2A 5 7 .3
1 8 .6 2 4 .2
5 .5
- -
2L2A 5 2 .2 1 4 .2 3 3 .6
4 .5
- -
3A 3 2 .6
9 .9 5 7 .5
3 .0 - -
3R2A 5 4 .1 7 . 0
3 8 .9 7 .1
- -
3L2A07 5 4 .9
1 3 .0
3 5 .5
3 .8 - -
4A04 4 4 .4 6 .1
4 9 .5
2 .8 6 .7
0 .2 0
4A412 - - - -
8 .7 0 .1 9
4E06 - - - - 1 2 .6
0 .2 3
4E612 - - - -
1 2 .9
0 .2 1
4R1A06 - - - - 8 .3
0 .3 2
4R1A612 - - - - 1 0 .4 0 .2 6
4R1E
\
-
-
-
- 1 1 .6 0 .1 4
4R2A - - -
7 .5
0 .1 0
4R2E - - - - 1 1 .4 0 .0 6
4R5A09
4 3 .2
6 .7
5 0 .1 8 . 4 8 .0
0 .1 9
4R3A912 -
-
- - 1 0 .8 0 .2 3
4R3E -
- - - 1 3 .6 0 .2 1
4L1A07
- -
- - 7 .2
0 .2 7
4L1A712 - - - - 1 0 .2 0 .0 0
4L1E 1 0 .0 0 .2 4
168
PERCENTAGE OP QUARTZ, FELDSPARS, HEAVY MINERALS,
ORGANIC CARBON, AND CALCIUM CARBONATE (C o n tin u e d )
Sample
No.
Q tz .
%
G r a in s
O r th .
%
G rain s
P l a g .
%
G r a in s
Hvy.
Min. %
W eight
CaCO^
% 3
O rg.
Carb •
. % ...
4L2A08
-
-
- - 8 .6 0 .1 2
4L2A812 - -
-
-
1 0 .3
0 .8 0
4L2E - - - - 3 .6 0 .1 2
4L3A
4 1 .9
1 9 .4
3 8 .7 1 8 .9 5 .3
0 .3 6
5A04 5 4 .4
1 3 .9
3 1 .8
2 .5
- -
5R4A06 3 8 .0 1 3 .0 4 9 .0 6 .2
-
-
512AO5 5 7 .9 7 .7 3 4 .5 5 .3 - -
6A 3 8 .3
2 1 .4 4 0 .4 3 . 2 - -
6R3A06 4 2 .6 1 2 .2 4 5 .2 4 .1 - -
6L2A09 3 7 .7 2 1 .5
4 0 .8 7 .6 - -
7A 4 0 .1 1 8 .2
4 1 .7
2 .1 - -
7R2A 4 2 .4 1 5 .2 4 2 .4 3 .2 - -
7L2A 3 8 .9
1 4 .6
4 6 .5
8 .2
— -

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Asset Metadata

Creator Curtis, Charles M (author)

Core Title Sedimentology of the northern half of the Laguna Salada, Baja California

Degree Master of Science

Degree Program Geology

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest,Sedimentary Geology

Language English

Contributor Digitized by ProQuest (provenance)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c30-110596

Unique identifier UC11225634

Identifier usctheses-c30-110596 (legacy record id)

Legacy Identifier EP58549.pdf

Dmrecord 110596

Document Type Thesis

Rights Curtis, Charles M.

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA