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PEDOGENESIS AND GEOMORPHOLOGY OF HANAUPAH CANYON
ALLUVIAL FAN, DEATH VALLEY, CALIFORNIA
by
STEVEN ANDREW STADELMAN, B.S., B.A.
A THESIS
IN
GEOSCIENCE
Submitted to the Graduate Faculty of Texas Tech University in
Partial Fulfillment of the Requirements for
the Degree of
MASTER OF SCIENCE
Approved
Accepted
August, 1989
ACKNOWLEDGEMENTS
I would like to thank Ron Dorn for his professional
guidance as well as his unending encouragement and enthusiasm
throughout the course of my thesis. I would like to thank
B.L. Allen for his help and guidance and for my training in
soils. I would like to thank my other committee members, Jim
Barrick and Necip Guven, for their reviews of my thesis.
There are several other persons who have assisted me in my
work, including: Charlie Aulbach, Daryl Brownlow, Mike
Cross, Nanci Griffith, Mike Gower, Dave Jordan, Charlie
Landis, Jeff Lee, Lan Mai, Thuy Mai, Marina Oliver, Nick
Olsen, Nelson Rolong,J Edwin Seithelko, Siva Sivalingham, Bill
Slopey, and Bill Staines. I also extend my deepest gratitude
to my family, Toni Wiswell, and Mrs. Siva Chambers for their
support.
ii
..
TABLE OF CONTENTS
ACKNOWLEDGEMENTS I I
• • • • • • • • • • • • • • • • • • • . . • • • • . • • • • • • • • • ~ 1.
LIST OF
LIST OF
CHAPTER
I
TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1v
FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
I. INTRODUCTION AND PREVIOUS WORK ······••4••·· 1
II. SOIL DEVELOPMENT INDICES .................. 15
III. CLAY MINERALOGY ........................... 59
IV. MICROMORPHOLOGY ........................... 80
V. CONCLUSIONS ............................... 99
BIBLIOGRAPHY ...................................... 105
APPENDIX A: FIELD DESCRIPTIONS .................... 110
APPENDIX B: CHEMICAL PROPERTIES ................... 116
APPENDIX C: SALT TRANSECTS ........................ 121
iii
"L!ST-uF TABLES
1. Pedons and associated surface ages as determined by dating of desert varnish ........ 14
2. Maximum soil properties used for quantification ................................ 17
3. Sample calculations for Q3a-lower, profile 1 . .................................... 20
4. Pedon classification .......................... 23
5. Maxima observed during field description . .................................. 2 5
6. Linear regression statistical data for soil thicknesses, profile property indices, and profile indices .................. 26
7. Relative percentages of clay minerals ......... 62
8. Relative clay mineral content in pedogenic CaC03 rinds from XRD analyses of bulk samples ............................... 7 0
9. Micromorphological properties ................. 81
10. Field descriptions ........................... 111
11. Chemical properties .......................... 117
12. Salt transects ............................... 122
iv
LIST OF FIGURES
1. Location of Death Valley ........................ 4
2. East-west cross-section of Death Valley ......... 5
3. Location of Hanaupah Canyon Fan ................. 7
4. Generalized map of geomorphic units with soil pit locations ......................... 9
5. Flow chart of the soil development indices of Harden .............................. 16
6. Plots of unweighted profile property indices versus soil age ........................ 28
7. Plots of soil thicknesses versus soil age ...... 30
8. Plots of weighted profile property indices versus log soil age using total solum thicknesses .............................. 32
9. Plots of weighted profile property indices versus log soil age using upper horizon thicknesses ............................ 34
10. Plots of horizon indices versus depth .......... 38
11. Plots of weighted profile indices versus log soil age ............................ 41
12. Plot of differences in calcium carbonate equivalence values versus log soil age ......... 44
13. Diffraction patterns for pedon 1, unit Q3b2 ...................................... 61
14. Diffraction patterns for pedon 3, unit Q3a-lower ................................. 64
15. Diffraction patterns for pedon 2, unit Q3a-upper ................................. 66
16. Diffraction patterns for pedon 1, unit Q2b-lower ................................. 67
17. Diffraction patterns for pedon 1, unit Q2a .................................... · .. 69
v
·18. Photomicro~raph of-the Btky horizon of pedon 1 on the Q3a-lower unit showing the skel-vosepic fabric ............................ 84
19. Photomicrograph of the Btky horizon of pedon 1 on the Q3a-lower unit showing clay accumulation within voids of a rind of calcium carbonate .............................. 8 6
20. Photomicrograph of the Av horizon of pedon 1 on the Q3a-upper unit showing the vo-insepic fabric .............................. 88
21. Photomicrograph of the Av horizon of pedon 1 on the Q2b-lower unit showing a rosette of cloudy calcite crystals ............. 90
22. Photomicrograph of the Av horizon of pedon 1 on the Q2b-lower unit showing cloudy calcite crystals at void edges and microspar partially filling voids .............. 91
23. Photomicrograph of the Av horizon of pedon 1 of the Q3a-upper unit showing palygorskite (?) within a polycrystalline quartz lithorelict ............................. 94
vi
Introduction
CHAPTER I
INTRODUCTION AND PREVIOUS WORK
Soil development is the result of the interaction of
several soil forming factors, primarily parent material,
time, relief, organisms (flora and fauna) and climate
(Jenny, 1941). The effect of a particular factor on soil
formation can be determined by keeping all other soil
forming conditions constant. A chronosequence is a group of
soils with all factors constant except the age of the soil
(time) . Rarely are these conditions met for soils older
than a few thousand years due to paleoclimatic fluctuations
and corresponding changes in associated flora. The lack of
data on these two soil forming factors (climate and
vegetation) for most chronosequences results in the
approximation of the effects of age on soil development.
Analysis of soil properties in a chronosequence using
development indices has been the focus of considerable
research in recent years (Bilzi and Ciolkosz, 1977; Harden,
1982; Harden and Taylor, 1983). Soil properties are
compared to parent material properties and quantified based
on changes from the parent material. Quantified properties
can be arranged into several different indices. The most
comprehensive indices are those of Harden (1982) in which
development of individual properties, horizons, and profiles
can be evaluated separately.
Soil age is critical to the use of a development index.
There are several dating methods currently used on soils.
The most common method is the dating of organic radiocarbon
(Matthews, 1985), typically from organic-rich A horizons.
Soils in relatively dry regions, however, do not often
contain sufficient organic matter for radiocarbon dating.
Other sources of radiocarbon have been used, in particular
1
inorganic carbon in calcium carbonate (CaC03), which is a
common product of pedogenesis in soils of arid and semiarid
regions. Dates from pedogenic carbonate have not proven
reliable due to unpredictable effects of dissolution and
reprecipitation (Magaritz, et al., 1981; Chen and Polach,
198 6) .
Dating of pedogenic carbonate using radioactive decay
of the entrapped 234u to 230Th has also been done in arid
and semiarid soils (Ku, et al., 1979). Recent studies
(Sowers, et al., 1988; Amundson, et al., 1989) indicate that
pedogenic carbonate does not provide a closed system for
radioactive decay of 234u. Dates obtained are not
consistent with other data and can result in age reversals.
Another dating technique uses the chemistry of rock
varnish. Rock varnish is typically a dark brown coating
found on stable geomorphic surfaces in arid and semiarid
regions. Recent work (Dorn and Oberlander, 1982) indicates
that the origin of desert varnish is in part organically
controlled. The entrapment of organic matter in varnish has
been used to radiocarbon date land surfaces in arid and
semiarid regions (Dorn, et al., 1987). Chemical analyses of
desert varnish yield decreasing ratios of (Ca + K)/Ti as age
increases due to greater leaching of the Ca + K. Varnish
cation ratios are calibrated to dates from associated
radiocarbon for younger surfaces and other techniques (for
example, K-Ar) for older surfaces. Analysis of varnish for
cation ratios can then be used to date the surface. This
technique is referred to as cation-ratio (CR) dating (Dorn,
1983) .
Several alluvial fan surfaces in the Death Valley,
California, area have been dated using accelerator mass
spectroscopy (AMS) of radiocarbon and CR dating of desert
varnish (Dorn, 1988) . In addition to considerable age data,
stable isotope (Dorn, et al., 1987) and Mn/Fe analyses
(Dorn, 1988) on varnish components provide paleoclimatic
2
data over the past 800,000+ years. The combination of age
control and paleoclimatic data for a series of
geomorphically related soils presents an excellent
opportunity to study changes in soil development over time.
The research presented herein consists of a
chronosequence of soils developed on Hanaupah Canyon Fan
evaluated on the basis of field descriptions and laboratory
data. Soil development is evaluated and interpreted in
terms of the soil development indices of Harden (1982).
The primary objective of this phase of the work was to
evaluate soil development in comparison to the geomorphic
and paleoclimatic model of Dorn (1988) using field
descriptions, chemical properties, clay mineralogy, and thin
section descriptions. The secondary objective was to
evaluate the feasibility of the soil development indices of
Harden (1982) in a hyperarid region.
Description of the Study Area
Death Valley is one of several north-south trending
structural basins in the southwestern part of the Basin and
Range Province, southeastern California (Figure 1) . It is
also located at the south end of a series of these
structural basins with internal drainage, an area referred
to as the Great Basin (Hunt, 1975; Fiero, 1986). Formation
of the basin is the result of block faulting, with tilting
of the basin to the east (Hooke, 1972) .
Death Valley is the most dramatic of these valleys with
maximum relief from basin to mountaintop (Figure 2) of more
than 3400 meters (m) . Elevations range from -86 m at
Badwater Basin in the center part of the valley, to 3368 m
at Telescope Peak in the Panamint Range, approximately 15
kilometers (km) to the west. The basin, as it appears
today, is the result of tectonic activity over the past 4-5
million years, a relatively young area geologically (Hunt,
1975). On the east side, the Amargosa Range, including the
3
Fig. 1.
Relation of Death Valley to the aouthem Great Basin, northern Mojave Desert, and Sierra Nevada
0 10 JO 40 iO Mll.lS
NEVADA
• ...... -..-
Location of Death Valley (Hunt and Mabey, 1966).
4
We
st
Pe
ne
min
r
Va
lley
DE
AT
H
VA
LL
EY
Pan
amin
t R
ange
, pi
ne w
oods
fo
ulle
d on
wes
t /
ond
tille
d ea
st
/ (a
rid
tim
ber/
me
/ _...
shru
blan
d
#
E 11
st
Bloc
A M
ount
otn)
, foull~d
Of'
•tst
Ofld
frlt
c1d
110 S
t
Fig
. 2
. E
ast
-west
cro
ss-s
ecti
on
of
Dea
th V
all
ey
(H
unt,
1
97
5)
.
t.n
Black Mountains to the south and the Grapevine and Funeral
Mountains further north, rises over 2000 m above the valley
floor along a precipitous fault scarp. The mountains on the
west side consist of the Panamint Range, which rises over
3300 m above the valley floor to Telescope Peak along a much
longer fault scarp.
Alluvial-fan development in Death Valley reflects the
basin asymetry (Hooke, 1972). On the east side, fans are
relatively small and conical shaped with hanging channels
due to faulting. Toes of the fans are buried by salt pan
sediments due to tilting of the basin and drainage
eastwards. On the west side, fans are much longer (8-13
km), cover larger areas (25-40 km2), drain larger areas (50-
65 km2), and coalesce to form an alluvial apron that extends
for several km along the base of the Panamint Range (Hunt
and Mabey, 1966).
Hanaupah Canyon Fan, one of the largest alluvial fans
on the west side of southern Death Valley, is nearly due
west of Badwater Basin (Figure 3) . It drains approximately
67 km2 of the Panamint Range including Telescope Peak. The
fan itself covers nearly 31 km2 and extends approximately 10
km from head to toe with over 600 m elevation difference.
The surface morphology is characteristic of most fans on the
west side, consisting of extensive areas of desert pavement
and channels, both active and abandoned. The current
channel (Holocene) is entrenched over 60 m at the fan apex
where its width exceeds 300 m. Less than 5 km downfan the
channel is only a few meters deep and the width expands to
several thousand meters.
Geomorphic units of Hanaupah Canyon Fan have been the
focus of several surface morphological studies over the last
two decades and have resulted in development of a relative
chronology for fan units (Denny, 1965; Hunt and Mabey, 1966;
Hooke, 1972; Hunt, 1975). Recent studies have included
chemical analyses of rock varnish and have provided an
6
Fig. 3. Location of Hanaupah Canyon Fan (Hunt and Mabey, 1966).
7
absolute chronology using radiocarbon and cation-ratio
dating (Dorn, 1983, 1988). Unit designations used herein
follow those based on fan morphology and chemical analyses
of rock varnish as presented by Dorn (1988).
The fan units are divided into three major groups, Q1,
Q2, and Q3 (Figure 4). Each of these is divided into
subunits "a" and "b" based on rock varnish analyses, with
those designated as "a" being older than "b" subunits. Most
of the Q3b (Holocene) deposits are located at the eastern
(downfan) part of the fan. These deposits include the
relatively narrow, deeply incised east-west main channel
that is located from apex to midfan. They have
characteristic bar and channel topography and have been
separated into three distinct subgroups based on amount of
varnish formation and morphology. Unit Q3a is located
completely on the north side of the main Holocene channel
and extends almost 10 km from fan ape~ to toe. It consists
mainly of large flat areas of heavily varnished desert
pavement with a few deeply incised abandoned channels and
numerous shallow internal drainages. Ages range from
approximately 14,000 yr BP at the toe above a fault, to
approximately 32,000 yr BP midfan, to over 50,000 yr BP at
the apex.
Units Q1 and Q2 are located mostly south of the main
Holocene channel and are similarly divided into a and b
units. Q2b is located primarily near the lower part of the
fan and is buried by Q3b gravels at the lower end, whereas
Q2a is located further upfan. Both units, although narrower
than Q3a, are characterized by broad, heavily varnished
desert pavements. They are highly dissected by deeply
incised drainages, many of which are abandoned. Cation
ratio ages on rock varnish range from 105,000 to 130,000 yr
BP for Q2b and 140,000 to 170,000 yr BP for Q2a.
Unit Q1 is located near the fan apex on the south side
of the current channel and consists of a highly dissected,
8
Q3b
Weat Side Road
Q3a-upper
Q2a
• 1
• Q 3a-mlddle
2
Q 3 a-lower
1
• 2 • 3 • ..
0
NORTH
1 2
kUometera
Fig. 4. Generalized map of geomorphic units with soil pit locations (after Dorn, 1988).
9
deeply incised geomorphic surface. Interfluves are rounded
and have fragments of an eroded petrocalcic horizon
10
(calcrete) common on the surface (This calcrete was observed
to be more than 3 m thick in outcrop) . Patches of rock
varnish have formed on boulders perched on top of interfluve
crests and yield cation-ratio dates as old as 800,000 yr BP,
representing a minimum date for the unit.
The geology of the Panamint Range drained by Hanaupah
Canyon consists of Precambrian and early Paleozoic
sedimentary and metasedimentary deposits. The lithology is
predominantly quartzite and argillite, although there is
granitic material exposed in the Telescope Peak area. The
fan deposits consist of gravelly to bouldery sands, loamy
sands, and learns (Appendix A) . Boulders can be several tens
of meters in diameter and found from apex to toe (Hunt and
Mabey, 1966). The lithology of the deposits of Hanaupah
Canyon Fan is typically 60% quartzite, 20% granitics, 10%
carbonates, and 10% argillites (Hunt and Mabey, 1966).
Percentages of the deposits exposed on surfaces of the
different fan units indicate compositions of approximately
20-30% igneous, 70-80% metamorphics, and only traces of
sedimentary rock types (Goodwin, 1988) .
The current climate of Death Valley is one of extreme
aridity, with average precipitation of less than 5 em per
year, most of which occurs as rain during winter months.
Average summer temperatures are commonly the highest in
North America and often exceed 49 C. The extreme aridity is
reflected in the scant vegetation. In the basin, vegetation
clusters around the bases of alluvial fans where shallow
groundwater and springs provide relatively fresh water. On
alluvial fans such as Hanaupah Canyon Fan, vegetation is
sparse; it is concentrated in channels and is indicative of
high aridity, consisting mostly of scrub creosotebush
(Lorrea sp.), Eripggnum sp., and other xerophytes.
Interfluves, where broad areas of desert pavement have
formed, are nearly devoid of vegetation.
Analyses of drill cores from the basin, packrat
middens, and rock varnish indicate that the current
hyperarid climate started at the end of the Pleistocene
about 13,000 to 10,000 yr BP (Hooke, 1972; Wells and
Woodcock, 1985; Dorn, 1988). Archeological and geomorphic
relationships indicate that the extensive salt pan in the
central basin is late Holocene in age (Hunt and Mabey, 1966;
Hunt, 1975) .
Late Pleistocene packrat (Neotoma) middens indicate
that the full glacial climate in Death Valley was
considerably less arid than today (Wells and Woodcock,
11
1985) . Vegetation consisted of chaparral, yucca, and
Joshua trees at 425 m elevation. Juniper woodland, today
located above 1950 m in the Panamint Range, was at 1130 to
1280 m on footslopes, where creosotebush is found today.
Transition of the full glacial climate to the extant
vegetation characteristic of hot deserts began approximately
13,000 years yr BP and lasted until 10,000 yr BP.
Cores from the basin indicate the presence of two lakes
in the last approximate 50,000 years (Hooke, 1972).
Evidence of fresh water sediments was observed and
correlated to the late Pleistocene and interpreted as
evidence for a perennial lake that formed sometime prior to
26,000 yr BP and ended about 10,000 yr BP. Radiocarbon
dating (AMS) of rock varnish from shorelines of this lake
indicates that the high stand occurred approximately 13,000
years ago, after which it declined and disappeared by 10,000
yr BP (Dorn, 1988) . The present day saltpan is the result
of dessication of a mid-Holocene lake approximately 2000 yr
BP as indicated by archeological materials in overlying
aeolian deposits (Hunt and Mabey, 1966).
Chemical and microstratigraphic analyses of rock
varnish from alluvial fans in Death Valley, including stable
carbon isotopes and Mn/Fe ratios, provide paleoclimatic data
that extend back into the middle and early Pleistocene
(Dorn, 1988) . Analyses include stable carbon isotope and
Mn/Fe ratios. Together, these data indicate there have been
cycles of arid and semiarid periods during fan deposition.
These cycles are used to classify fan units by representing
deposition during semiarid periods with subscript "a'' and
periods of arid deposition with "b."
Soils on Hanaupah Canyon Fan
Eighteen soils were described from five geomorphic
units (Figure 4), including Qla, Q2a, Q2b, Q3a (upper,
middle, and lower) and Q3b. Two to three pedons were
described for all but the Q2a unit (1 pedon) and Q3b2 (6
pedons) . Pits were located on stable interfluves of desert
pavement or where recent channels cut through interfluves.
In the latter setting, profiles were excavated back from the
channel edge approximately 1-2 m to minimize possible edge
effects from channel banks. All soils were well drained
with slopes ranging from 7-11%. Descriptions were made to
the C horizon in most cases, using the absence of pedogenic
CaC03 accumulation as an indicator of the B/C boundary.
Gravel content in all pedons exceeded 35% by volume and was
estimated to range from 45 to 65%.
12
Horizon designations follow that of Soil Taxonomy (Soil
Survey Staff, 1975) with the following exceptions. All
surface horizons are vesicular and are designated as Av
horizons. In most of the younger soils, the horizon
immediately below the Av horizon contains rinds and pendants
of calcium carbonate on clasts, warranting a "k" subscript.
These horizons, however, have colors identical to those of
overlying Av horizons but are redder than underlying Bk
horizons. To indicate the development of color as well as
carbonate accumulation, these are designated as Bwk
horizons. Age estimates based on AMS radiocarbon and CR
dating are presented in Table 1.
13
Table 1. Pedons and associated surface ages as determined by dating of rock varnish (Dorn, 1988)
Pedon aqe
Qla Q2a-1 Q2bl-1 Q2bl-2 Q3au-1 Q3au-2 Q3au-3 Q3am-1 Q3am-2 Q3am-3 Q3al-1 Q3al-2 Q3al-3 Q3b2-1 Q3b2-2 Q3b2-3 Q3b2-5 Q3b2-6
(thousands of years)
>800 145 + 18 120 + 13 120 ± 13
50 + 4 50 + 4 50 ± 4 32 + 3.3 32 ± 3.3 32 + 3.3 15.4 + 1.5 15.4 ± 1.5 15.4 + 1.5
4. 4 + 1.1 4 . 4 + 1. 1 4.4 + 1.1 4 . 4 + 1. 1 4.4 + 1.1
14
CHAPTER II
SOIL DEVELOPMENT INDICES
Methods
Soil Development Indices
Many soil properties follow systematic changes with time
(Birkeland, 1984). Examples include increasing grade of
structure, increasing clay content and expression of clay
accumulation, shifts in texture to finer classes, and change
of colors to redder hues and brighter chromas. The
systematic nature of these changes has been the focus of
considerable recent work, resulting in the establishment of
soil development indices based on field and laboratory data
(Bilzi and Ciolkosz, 1977; Meixner and Singer, 1981; Harden,
1982; Harden and Taylor, 1983). Early indices allowed
comparison of relative horizon development by observing
changes in soil properties across soil boundaries (Bilzi and
Ciolkosz, 1977) . The most comprehensive indices, however,
are those developed by Harden (1982) in which soil properties
are quantified based on changes relative to parent material
properties. Normalization of soil properties allows
comparison of development of individual properties, horizons,
and profiles with time.
The method of quantifying soil properties is presented
in Figure 5. Critical to the use of soil development indices
is characterization of the parent material. Properties of
parent material for Hanaupah Canyon Fan were described from C
horizons and are presented in Table 2. Properties used for
quantification include: 1) texture, here replaced with
particle size distribution determined in the laboratory; 2)
dry consistence; 3) structure; 4) development of clay films;
5) stage of carbonate formation; 6) rubification (increasing
hue and chroma); 7) color paling (decreasing hue and chroma);
and 8) color lightening (increasing value) . Morphology of
15
Pro
file
p
rop
ert
y In
dex
14
1
Wei
ghle
d p
rofil
e
pro
pe
rty
Inde
x 14
1
No
rma
lize
q
ua
ntif
ied
p
rop
ert
lea
(d
ivid
e b
y m
axim
um
quan
tifie
d p
rop
ert
y)
Sum
no
rmal
ized
pro
pert
lea
lor
each
hor
izon
Div
ide
by
num
ber
of
qu
an
lllie
d p
rope
rtle
a •
horiz
on I
ndex
Pro
file
inde
x S
um
horiz
on
pro
du
tll
thro
ugh
prof
ile J
~
J I
Div
ide
aum
by
depl
h of
ao
ll de
acrip
lion
I ~
We
igh
led
pr
ofile
in
dex
Fig
. 5
. F
low
ch
art
o
f th
e so
il
dev
elo
pm
en
t in
dic
es
of
Hard
en
(1
98
2).
~
~
1.
2.
3.
4 .
5.
6.
7.
8.
Tab
le
2.
Max
imum
so
il p
rop
ert
ies
use
d
for
qu
an
tifi
cati
on
so
il
pro
perty
Str
uctu
re
Dry
co
nsi
sten
ce
Cla
y
film
s
Part
icle
siz
e
dis
trib
uti
on
Ru
bif
icati
on
Pali
ng
Lig
hte
nin
g
Car
bo
nat
e st
ag
e
pa
ren
t
ma
teria
l
sin
gle
gra
in
loo
se
no
ne
loam
y sa
nd
to
sil
t lo
am
2.5Y
4
/4
2.5Y
4
/4
2.5Y
4
/4
no
ne
no
rm
ali
za
tio
n
ma
xim
a
mo
der
ate
sub
an
gu
lar/
pla
ty
very
hard
few
th
in d
isco
nti
nu
ou
s
sil
t lo
am
lOY
R
4/6
2.5
Y
5/2
2.5
Y
5/4
stag
e
IV
~
..,J
secondary carbonate accumulation has been used by McFadden,
et al. (1986) in the framework of the indices of Harden
18
(1982) . In this study, the stage of calcium carbonate
accumulation (Gile, et al., 1966) was used. Two properties
from previous indices are not used here. Melanization, which
quantifies darkening of upper horizons due to the
accumulation of organic matter as is manifested in decreasing
color values, was not observed for soils from Hanaupah Canyon
Fan, likely due to the paucity of vegetation. The other
property is the change in pH, of which both lowering (Harden,
1982) and increasing (Reheis, 1987) have been used. Changes
in pH were not quantified due to considerable variability
within and between profiles.
Once parent material properties were established, soil
development was quantified as defined by earlier indices
(Harden, 1982). Ten points were assigned to each horizon for
each systematic shift in a property from that of the parent
material. Each property was then normalized using a maximum
value, either the maximum recorded from profile descriptions
or an established maximum. Quantification maxima are
presented in Table 2.
Normalization yielded values between 0 and 1 for each
property for each horizon. Five indices were calculated.
Multiplying normalized values by horizon thickness and
summing through the profile yielded the profile property
index. Division by the total solum thickness yielded the
weighted profile property index. These two indices, when
plotted versus soil age, allowed comparison of individual
property formation through time.
Horizon and profile indices were calculated in a
slightly different manner. The normalized properties for
each horizon were summed and divided by the number of
properties used, which produced the horizon index. Plotting
this index versus horizon depth allowed comparison of horizon
development within and among profiles. Multiplying the
horizon index by corresponding horizon thickness and summing
through the profile produced the profile index, which
provided a comprehensive way of comparing total soil
development. Division by total solum thickness yielded the
weighted profile index. Weighted indices allowed comparison
of soil development separately from trends in depth of soil
formation. Sample calculations of these indices are
presented (Table 3) for pedon one from unit Q3a-lower.
Chemical Analyses
Calcium carbonate eguiyalence CCCEl . Calcium carbonate
equivalence was determined on the < 2mm fraction for
horizons of most pedons except indurated horizons. Values
were determined according to the neutralization procedure
outlined in the USDA Handbook No. 60 (U. S. Salinity
Laboratory Staff, 1954).
Electrical conductivity CECl . Electrical conductivity
19
was determined for most pedons on < 2mm fractions according
to the procedure outlined in the USDA Handbook No. 60 (U. S.
Salinity Laboratory Staff, 1954) using a Beckman RD-26 Solu
Bridge. Additional determinations were made on upper
horizons from transects across well developed desert
pavements on stable interfluves.
Soil reaction CpHl . Values for pH were determined for
most pedons on < 2mm fractions using an Orion Research Model
601A digital ionalyzer for pastes prepared according to the
USDA Handbook No. 60 (U. S. Salinity Laboratory Staff, 1954).
Results
Soil Classification
Soils described on Hanaupah Canyon Fan (U. S. Soil
Survey Staff, 1975) are represented by four great groups of
soils: Paleorthids, Calciorthids, Camborthids, and
Torriorthents (Table 4). In the order given, these groups
represented decreasing age of pedons. For soils with zones
Tab
le
3.
Sam
ple
calc
ula
tio
ns fo
r Q
3a-l
ow
er,
p
rofi
le
1.
ho
rizo
n
Av
Btk
z
Bk
-B
k-
up
per
low
er
thic
kn
ess
(em
) 5
19
2
6.5
9
0.5
Qu
an
tifi
ed
pro
pert
ies
1.
dry
co
ns.
2
0
15
0
0 2
. str
uctu
re
20
2
0
0 0
3.
cla
y fi
lms
0 0
0 0
4.
tex
ture
2
0
0 1
0
0 5
. ru
bif
icati
on
1
0
10
0
0 6
. li
gh
ten
ing
0
0 0
0 7
. p
ali
ng
1
0
0 0
0 8
. carb
on
ate
0
20
2
0
20
No
rmali
zed
p
rop
ert
ies
1.
dry
co
ns.
0
.5
0.3
75
0
0 2
. str
uctu
re
0.6
67
0
.66
7
0 0
3.
cla
y fi
lms
0 0
0 0
4.
tex
ture
0
.66
7
0 0
.33
3
0.3
33
5
. ru
bif
icati
on
0
.33
3
0.3
33
0
0 6
. li
gh
ten
ing
0
0 0
0 7
. p
ali
ng
0
.5
0 0
0 8
. carb
on
ate
0
0.5
0
.5
0.5
c
---- 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
N
0
Tab
le
3.
(Co
nt'
d)
Un
weig
hta
d
pro
fil
e
pro
pert
y
ind
ex
=
n
orm
ali
zed
pro
pert
ies
mu
ltip
lied
b
y
ho
rizo
n t
hic
kn
ess
=
Weig
hte
d
pro
file
p
rop
ert
y
ind
ex
=
u
nw
eig
hte
d d
ivid
ed
by
to
tal
solu
m t
hic
kn
ess
=
9.6
25
1
6
0 8 2
.5 0
42
.29
5
68
0.3
86
0
.66
7 0
0.3
33
0
.01
77
0 0
.3
0.4
82
N ~
Tab
le
3.
(Co
nt 'd
)
ho
rizo
n
Av
Sum
o
f n
orm
ali
zed
p
rop
ert
ies
=
2 .1
67
Sum
d
ivid
ed
b
y
the
nu
mb
er o
f p
rop
ert
ies
=
Ho
riz
on
in
dex
-
0.3
1
Sum
o
f n
orm
ali
zed
p
rop
ert
ies m
ult
ipli
ed
b
y h
ori
zo
n
thic
kn
ess=
1
.54
8
Btk
z
Bk
-B
k-
up
per
low
er
1.8
75
0
.83
3
0.8
33
0.2
68
0
.11
9
0.1
19
5.0
89
3
.15
4
10
.77
Sum
=
u
nw
eig
hte
d
pro
file
in
dex
=
2
0.5
60
1
Weig
hte
d
pro
file
in
dex
=
2
0.5
60
1/p
rofi
le th
ick
ness
-
c 0 0 0
0.1
45
8
N
N
23 Table 4. Pedon classification.
Pedon Classification
1 . 01 * 2 . 01 * 3. 01 * 4 . Q2a Typic Paleorthid 5. Q2bl-1 Typic Paleorthid 6. Q2bl-2 Typic Paleorthid 7 . Q3au-1 Typic Calciorthid 8. Q3au-2 Typic Calciorthid 9. Q3au-3 Typic Calciorthid 10. Q3am-1 Typic Calciorthid 11. Q3am-2 Typic Calciorthid 12. Q3am-3 Typic Calciorthid 13. Q3al-1 Typic Calciorthid 14. Q3al-2 Typic Calciorthid 15. Q3al-3 Typic Calciorthid 16. Q3b2-1 Typic Torriorthent 17. Q3b2-2 Typic Torriorthent 18. Q3b2-3 Typic Torriorthent 19. Q3b2-4 Typic Camborthid 20. Q3b2-5 Typic Camborthid 21. Q3b2-6 Typic Camborthid
* Exhumed petrocalcic horizons
24
of pedogenic clay accumulation, none met the requirements for
an argillic horizon. Calcium carbonate was the dominant soil
property that governed classification except for the Q3b2
pedons (Holocene) .
Profile Property Indices
Eight soil properties were used for quantification of
soil development on Hanaupah Canyon Fan. The maxima from
field descriptions for each are given in Table 5. These
maxima correspond to those used for normalization (Table 2),
with two exceptions. The maximum stage of CaC03 accumulation
described was stage III; however, soil development on the
oldest unit (Q1a) was represented by an exhumed petrocalcic
horizon. It seems likely that the upper part of the
petrocalcic horizon was laminar (stage IV) and subsequently
was eroded upon exhumation. Thus, stage IV was used for
normalization. The maximum development of structure
described was a combination of weak subangular blocky and
weak platy. Moderate subangular blocky structure was used
for normalization.
Unweighted and weighted profile property indices were
calculated for each property and plotted versus soil age
using semi-log and log-log models (Y or log Y - a+b log X;
where Y is soil property and X is soil age) . All properties
showed the best correlation with soil age when weighted
values were plotted versus log soil age (Table 6) . With the
exception of particle size distribution and rubification, all
were significant at the 0.01 level. Weighted profile indices
were calculated for (1) all seven properties and (2) the best
four properties. Both showed the best correlation with log
soil age and were significant at the 0.01 level. Total
solum, upper, and lower horizon thicknesses were also plotted
versus soil age, except for the lower horizon thickness,
which was plotted versus linear soil age. Linear regressions
for total solum and lower horizon thicknesses showed the best
1 .
2 .
3.
4 .
5.
6.
7 .
8.
Table 5. Maxima observed during field description.
soil
property
Structure
Dry consistence
Clay films
Particle . s~ze
distribution
Rubification
Paling
Lightening
Carbonate stage
field description
maxima
weak subangular/platy
very hard
few thin discontinuous
silt loam
10 YR 4/6
2.5Y 5/2
2.5Y 5/4
stage III
25
Tab
le
6.
Lin
ear
reg
ressio
n sta
tisti
cal
data
fo
r so
il th
ick
nesses,
pro
file
p
rop
ert
y in
dic
es,
an
d p
rofi
le
ind
ices.
Th
ick
ness
es
vers
us
To
tal
solu
m
Up
per
h
ori
zo
ns
Lo
wer
h
ori
zo
ns
Th
ick
ness
es
vers
us
To
tal
solu
m
Up
per
h
ori
zo
ns
Lo
wer
h
ori
zo
ns
y =
li
near
so
il
ag
a
1.3
4x
+1
10
.2
0.0
69
x+
12
.6
1.3
8x
+8
3.8
log
so
il
ag
e
13
6.6
x-2
6.0
1
1.9
x-0
.20
5
11
7.7
x-1
9.1
r
0.9
35
0
.25
2
0.9
68
0.9
39
0
.54
5
0.9
25
Weig
hte
d
pro
file
p
rop
ert
y
ind
ices
vers
us
thic
kn
esses
Dry
co
nsis
ten
ce
0.0
14
x+
0.0
47
0
.20
9
Str
uctu
re
0.0
09
5x
+0
.05
8
0.0
91
R
ub
ific
ati
on
0
.00
86
x+
0.0
24
0
.16
7
Cla
y
film
0
.04
4x
-0.0
27
0
.52
P
art
icle
siz
e
dis
trib
uti
on
0
.00
29
x+
0.0
9
0.0
11
C
arb
on
ate
sta
ge
0.2
2x
+0
.15
8
0.9
42
L
igh
ten
ing
0
.71
6x
-0.6
34
0
.82
2
Weig
hte
d
pro
file
p
rop
ert
y
ind
ices
vers
us
thic
kn
esses
Dry
co
nsis
ten
ce
0.3
1x
+0
.07
6
0.7
15
S
tru
ctu
re
0.1
1x
+0
.48
0
.79
9
Ru
bif
icati
on
0
.11
x+
0.2
2
0.5
17
C
lay
fi
lms
0.5
1x
-0.3
7
0.6
94
Weig
hte
d
pro
file
in
dic
es
vers
us
log
so
il
All
7
pro
pert
ies
0.1
5x
-0.0
46
0
.79
B
est
4
pro
pert
ies
0.2
6x
-0.1
1
0.9
25
log
so
il
log
so
il
age
r2
0.8
75
0
.06
4
0.9
37
0.8
82
0
. 2
97
0
.85
6
ag
e
0.0
44
usi
ng
0.0
08
27
0
.02
8
0.2
7
0.0
00
12
0
.88
8
0.6
76
. ag
e
US
1ng
0.5
11
0
.63
8
0.2
67
0
.48
1
0.6
23
0
.85
5
p
0.0
00
1
0.3
13
0
.00
01
0.0
00
1
0.0
19
4
0.0
00
1
tota
l so
lum
0.4
73
2
0.7
57
1
0.5
68
1
0.0
56
7
0.9
7
0.0
00
1
0.0
00
3
up
per
ho
rizo
n
0.0
04
1
0.0
00
6
0.0
58
6
0.0
05
9
0.0
00
8
0.0
00
1
N "'
correlation with log and linear soil age, respectively, and
were statistically significant at the 0.01 level. Upper
horizon thickness showed no correlation with soil age.
27
Unweighted plots of profile property indices versus soil
age are presented in Figure 6. At this point, no
interpretations of soil development were made because trends
in soil thickness may have masked or distorted trends in
individual property development. One property, paling, was
not used in subsequent indices. As originally defined
(Harden and Taylor, 1983), paling was used to quantify
systematic increases in soil hue and/or chroma due to CaC03
accumulation in soils of semi-arid and arid regions. For all
but one soil on Hanaupah Canyon Fan, paling occurred in upper
horizons, typically in a vesicular A horizon, and not in Bk
horizons. Since the values calculated did not represent the
pedogenic processes originally associated with color paling,
it was not used in further calculations. Still, it provided
insight into processes affecting pedogenesis, which will be
discussed later.
Dividing property indices by total soil thickness can be
used to remove the influence of trends in soil thickness from
the indices, so that it reflects only development of
individual properties (Harden, 1982; Busacca, 1987). Before
property indices were weighted in this manner, it was
necessary to look at trends in soil thickness to be sure that
weighting was in fact removing their effects from indices
calculations. Total, "upper," and "lower" horizon
thicknesses were plotted versus soil age (Figure 7) . Lower
horizons were defined as those dominated by accumulation of
calcium carbonate whereas upper horizons were those
represented by more pronounced development of the other
properties. In most pedons, Btk or Bwk horizons were
included in upper horizons. When thusly defined, upper and
lower horizons could be easily distinguished in the field on
the basis of color, consistence, structure, and clay films
Fig. 6. Plots of unweighted profile property indices versus soil age (in thousands of years) : a. structure, b. rubification, c. clay films, d. dry consistence.
35 a. 28 30 •
25
20 • 11 • • •
• • • 10 • • 2
5
0 0 20 40 u 10 100 120 uo tiO
15
• b . 10 • 11 •
• 10 •
• • • I • • 5 • 0
0 20 40 10 10 100 120 140 110
25
c. 20 • • • 15
• • 2 tO
5 • 0 ·-3-2
0 20 40 10 10 tOO 120 140 tiO
25 d. •
20
u • • I • •
10 I • • •
5
0 0 20 •o 60 10 100 120 140 160
Fig. 6. (Continued) e. particle size distribution, f. stage of carbonate formation, g. color lightening, and h. color paling.
tOO
10
10
70
10
10
40
30
20
tO
0 0
300
210
zoo
110
•
I • • • • • 20
I
•
• • •
•
• I 40 10 10 tOO
• • •
tZO 140
e.
uo
f 0
• • z
0~--~~---.----~----~----~--~-----.----~ 0 tOO 200 300 400 500 100 700 100
300 g . • 210 • • zoo
110 • tOO
10
0 ·-3-3 0 zo 40 10 10 tOO uo t40 uo
uo h . • 140
uo
tOO
10
10
40
10
I • • I e 0 • I • • • 0 20 40 10 10 tOO uo uo uo
29
Fig. 7 .
a. r • 1.Uia • 111.U1, R·•1111ue1M: .171
10
0~--~----~--~----~--~----~--~--~ 0 20 40 10 to 100 120 140 110
b. ' ....... 11.1, ·~· ....
I
I . •
" I • • • II 40 •• 10 100 120 140 110
c. ' • , •• ,. • 71.1, ........... .117
10
I
0+---~----~----~--~----~--~----,---~ 0 10 40 10 10 100 120 140 110
Plots of soil thicknesses (in thousands of years): b. upper horizons, and c.
versus soil age a. total solum, lower horizons.
30
31
(where present) . The boundary between upper and lower
horizons was distinct in all profiles and easily determined.
Total solum thickness changed linearly with soil age over the
past 145,000 years as did lower horizon thickness. Upper
horizon thickness, however, behaved very differently.
Correlations of upper soil thickness with age were low for
linear, semi-log, and log-log plots (Table 6).
Whereas total and lower soil thicknesses increased
steadily with increasing age, upper soil thickness was very
low in the Q3b2 (Holocene) profiles. They reached a maximum
in the Q3a-lower (Late Pleistocene) profiles, decreased
considerably to Q3a-middle profiles, and then decreased
slowly over the next 100,000 years.
Upper horizon profile property indices. Comparison of
soil thickness age trends with similar trends for unweighted
profile property indices indicated that structure,
rubification, clay films, and dry consistence strongly
reflected upper soil thickness. Weighting of these soil
properties using total thickness had variable effectiveness
for removing thickness trends (Figure 8) . For these
properties, dividing by total thickness yielded age trends
with maxima in late Pleistocene profiles that decreased with
increasing age. This distribution was not consistent with
the field data from which they were calculated. Field data
indicated that structure and rubification had maximum
development (weak subangular blocky and 10YR hues,
respectively) in Late Pleistocene and Holocene profiles,
respectively, and remained relatively constant with
increasing age. Clay film development reached a maximum in
soils on Q3a-middle units (32,000 yr BP) then remained
constant (few thin discontinuous films) in older profiles.
Dry consistence changed to slightly harder consistencies as
age increased.
Using total thickness for indices calculation of these
four properties (structure, rubification, clay film
Fig. 8. Plots of weighted profile property indices versus log soil age (in thousands of years) using total solum thicknesses: a. structure, b. rubification, c. clay films, d. dry consistence, e. particle size distribution, f. color lightening, and g. stage of carbonate formation.
32
' . ··-.a. . -._... .. ., .... a. ' . ......... . ..... .._.. ·- b. .I
.I
••• ... . II
.I ... ... ... . . ... ••• ... • • • .. ••• I 1.1 I • .. 1.1 •• I
c . d. .. - ................. , ...................... .....
... ... • . .. .... • • .I 1.1 1.1 I • .I ..• I II •
e. f. ' ............... .._ ........ .. '. ··- ................ ·-. . .. . a
• ..• •.I
• .. ••• I ••• • .I 1.1 I I
r • .ua • .tM. ........_.. .... g.
. I
·~ .... ----.... --~----~--~----------~ • .I I I II I
33
development, and dry consistence) did not yield trends
consistent with field descriptions. For all profiles
described, changes in these properties from the parent
material occurred only in upper horizons, typically vesicular
A and Bwk (younger soils) or A and Btk (older soils)
horizons. Lower (Bk) horizons, which made up the bulk of the
total soil thickness, were not developed in respect to these
properties. Due to the much greater thickness of the lower
versus upper horizons, weighting of property indices using
total thickness did not accurately represent development of
these properties in upper horizons. This warranted
modification of the index to reflect true trends in
development of upper horizon properties. One of the more
useful aspects of Harden's indices (1982) is that they can be
modified.
Indices for upper horizon properties were weighted
again, this time using upper horizon thickness and plotted
against log age (Figure 9) . The results were in agreement
with the field data from which they were calculated.
Structure had the lowest values (very weak subangular blocky)
in the Q3b2 (mid-Holocene) profiles, reached maximum values
(weak subangular blocky) by about 32,000 yr BP on the Q3a-
middle surface, and did not change in older soils.
Rubification trends were similar, except that the
maximum (10 YR) was present in the youngest profiles (mid
Holocene) and did not change until approximately 145,000 yr
BP.
Clay accumulation did not change appreciably using upper
horizon instead of total solum thickness. Maxima were still
present in the Q3a-middle pedons and decreased steadily in
older profiles. Field observations indicated that expression
of clay film development should not have decreased once
maximum development occurred. The decrease seen was an
artifact of the calculations. Clay accumulation occurred in
Btk horizons and not in A horizons. Since all older profiles
34 a. b.
r • .117a • .471, ll-e4t-..l: .IJI ' ........ 111, .... ~-·--; .117
.I .I
.I .I
.7 .7
•• .I .I .I .4 • . 3 .3 .2 .2 .I
.I
0 0 .I 2.1
0 0 .I I.S 2 2.1 1.1 2
c. d.
' • ..... 0 ~74, ·~= ....
..
. 2
0
0~----~----~----~----~----------~ 0 .I 1.1 2 2.1 ·.2~-...c;..:---------------0 .I 1.5
Fig. 9.
2 2.1
Plots of weighted profile property indices versus log soil age (in thousands of years) using upper horizon thicknesses: a. structure, b. rubification, c. clay films, and d. dry consistence.
35
showed the same development, quantification resulted in
normalized values of 1 for all Btk horizons. Normalized
values were multiplied by the associated horizon thickness,
then weighted by dividing by upper horizon thickness (which
includes the thickness of the A horizon). Thus, clay film
development indices calculated in this way reflected changes
in the ratio of the thicknesses of the Av and Btk horizons.
Correlation of dry consistence with soil age improved
considerably using upper horizon thickness for indices
calculations, although it is still poor (Table 6) . Values
reached a maximum by approximately 120,000 yr BP then
decreased in the next older pedon (about 145,000 yr BP).
Lower horizon properties. The three remaining
properties, particle size distribution, lightening, and stage
of carbonate formation, had different age trends. Since
these properties reflected changes that occurred throughout
the profile, they were weighted using total solum thickness
(Figure 8).
Particle size distribution reflects general fining
(accumulation of clay and silt fractions) of soils with age
due to breakdown of minerals by pedogenic processes and
accumulation of clay (Harden, 1982) . In the development
indices, field texture has typically been combined with moist
consistence and referred to as total texture. Moist
consistence was used to accomodate wide ranges in clay
content of textural classes. For this study, field texture
was replaced with particle-size distribution determined in
the laboratory. Moist consistence was not described;
however, soils described on Hanaupah Canyon Fan had a narrow
range of clay. In general, the silt and clay content
increased in upper horizons, as reflected by shifts from
loamy sand or sandy loam in lower to silt loam in upper
horizons.
Changes in particle size distribution had no correlation
(Table 6) with soil age. For profiles of similar age, some
36
had high index values due to more silt and clay in upper
horizons, whereas others had values of zero. The difference
was due to the extreme variability of parent materials, some
of which contained as much as, or more silt than, the
overlying solum. This variability reflects the nature of the
depositional environment of Hanaupah Canyon Fan, where the
tremendous elevation difference from source area to fan over
a relatively short distance resulted in deposition by debris
flows as well as water (Hooke, 1972) . Particle size
distributions of C horizons ranged from loamy sand through
silt loam. Vesicular A horizons typically had the highest
silt content in the profile and were usually silt loams.
Thus, profiles with loamy sand or sandy loam parent materials
had the highest indices, whereas profiles with loam or silt
loam parent materials had low or zero values. The latter was
typical for soils in the study area.
Lightening of color is another property, similar to
paling, that has been used to quantify changes in soil color
due to accumulation of calcium carbonate in arid and semiarid
regions (Harden and Taylor, 1983). Points were assigned for
increases in color value compared to that of the C horizon.
In this study, C horizons had two colors (moist), 2.5Y 4/4
and 2.5Y 5/4. Distribution of these colors was age related.
Profiles younger than 50,000 yr BP had 2.5Y 4/4 colors for C
horizons as well as for Bk horizons. Soils 50,000 yr BP and
older had 2.5Y 5/4 colors for C and Bk horizons. Parent
material color of the younger pedons (2.5Y 4/4) was used for
quantification in all profiles. Plots of weighted lightening
versus log soil age are presented in Figure 8. Soils younger
than 50,000 yr BP had zero values, whereas older soils had
higher values due to changes in color value from 4 to 5.
The stage of carbonate formation (Gile et al., 1966) was
used here to quantify recognizable changes in pedogenic
carbonate accumulation. Although located predominantly in
lower horizons, some upper horizons (usually Bwk or Btk) also
exhibited carbonate accumulation and were included in
calculations. Points were assigned for the stage described
in each horizon, resulting in some profiles where upper
horizons (Btk, Bwk) had a lower stage of carbonate formation
than lower indurated horizons (Bkm). The oldest unit, Q1a,
was represented by stage III indurated pedogenic calcrete
with an erosional upper surface; however, a laminar horizon
may have been present prior to erosion. Stage IV was
therefore used for quantification. Thus, thicknesses of
indurated carbonate for Q1a were considered minima, as were
subsequent weighted values for stage of carbonate formation.
Weighted stage of carbonate formation versus log soil
age is presented in Figure 8. Of the seven field properties
quantified, stage of carbonate formation showed the best
correlation with soil age (Table 6) .
Horizon Indices
Summing of normalized values for each property for each
horizon, when divided by the number of properties (seven),
yielded the horizon index (Harden, 1982) . Development of
soil properties within profiles over time was charted by
plotting values versus horizon depth for soils of similar
37
age. The youngest pedons, approximately 4,400 years old, had
maximum horizon indices of approximately 0.2-0.3 in thin (1-2
em) vesicular A horizons due to rubification and slight
development of dry consistence and structure (Figure 10 a) .
Indices decreased to < 0.1 in B horizons, reflecting calcium
carbonate accumulation. Values decreased to zero in C
horizons.
On the next oldest unit, Q3a-lower (approximately 15,400
yr BP) there was the same general trend of maxima in A
horizons decreasing to zero in C horizons (Figure 10 b) .
Values in upper horizons were higher (0.25-0.3) due to harder
dry consistencies and increasing structure grade, and
extended to depths of approximately 20-40 em. Lower (B)
Fig.
.. .. ,. ..... •••••• .. a.
71 .. ..
I
10
•• •• .. ... ... , ... Ill
••• ... ... ... c.
10.
•
••• • ••
1.1 •••
1.1
I.J
••• •••
....... . ,..... .. ,....I
1.& •••
..,..... . ...... ....... ,
.. ... ::; ... ...
Ill ... e.
• ••
• ••
Plots of horizon b. Q3a-lower, c. e. Q2b-lower and
II .. 10
:::; .. ... , .. ••• Ill
b .
• .. • • .. ... II ... , ...
Ill
• •• .. . ... d.
.. ..... ..
.,_ ... . .. ,_ -·
1.1 1.1 .. ,
• 1.1 ••• .. ,
••• •••
..,_, .. .. _ . •..- J
••• • ••
..,_ .
.,_ . .. ,....,
indices versus Q3a-middle,
depth: d.
d Q3a-upper, Q2a.
•••
• ••
u3b2, and
38
39
horizons also had slightly higher values (approximately 0.1)
due to an increase in carbonate formation from stage I to II.
Two of the three profiles from Q3a-middle (approximately
32,000 yr BP) had maxima in Bwk and Btk horizons (Figure 10
c). Maxima increased to approximately 0.35-0.55, the highest
value corresponding to clay film development in pedon 3.
Values were slightly higher (0.3-0.35) in A horizons due to
slight increases in dry consistence, whereas Bk horizon
indices remained the same (0.1) since stage of carbonate
formation was unchanged. The depth of upper horizon
development, where maxima occurred, was less than 20 em.
All three profiles from Q3a-upper (approximately 50,000
yr BP) exhibited similar distribution of horizon indices
(Figure 10 d) . Values for A horizons remained relatively
unchanged from those in the Q3a-middle pedons, as did Btk
horizons, where profile maxima occurred (0.5-0.55). The Bk
horizon indices were slightly higher (0.25-0.3) than in
previously discussed pedons due to lightening of color to
2.5Y 5/4. Minimum values were reached inC horizons, but did
not reach zero (0.2) due also to similar changes in color
lightening. Upper horizon thicknesses remained less than 20
em.
Soils formed on Q2b-lower (approximately 120,000 yr BP)
and Q2a (approximately 145,000 yr BP) had slightly higher
maxima in Btk horizons, due to harder dry consistencies
(Figure 10 e) . Indices for A horizons similarly had slightly
higher values for the same reason. In contrast to the
younger soils, indices did not decrease steadily with depth
from maxima in upper horizons. Low values were recorded in
upper Bk horizons (stage II) located immediately above the
indurated (stage III) horizon. The upper Bk horizons
included detached fragments of the indurated horizons in the
lower parts. Low values in C horizons, which are still
slightly above zero, reflected color lightening.
40
Horizon indices reflected trends seen in property
indices described earlier, in which upper horizon properties
reached maxima relatively quickly (between approximately
15,400 to 50,000 yr BP) then decreased slowly in older soils.
Lower horizon values increased slowly from minima in Holocene
soils to maxima approximately 145,000 yr BP (Q2a).
Profile Indices
Multiplication of horizon indices by corresponding
horizon thicknesses, when summed through the profile, results
in a single number representing soil formation, referred to
as the profile index (Harden, 1982) . Unweighted and weighted
(using total solum thickness) profile indices can be plotted
versus soil age to yield insight into changes in total
development over time. In previous works (Harden, 1982;
Harden and Taylor, 1983; Busacca, 1987), the profile index
was calculated twice, once using all properties described and
again using the four properties that have the best
correlation between profile property index and soil age. In
some cases there was better correlation using the four best
properties than using all properties (Harden and Taylor,
1983; Harden, 1982). Busacca (1987) found little difference
between using all properties and the best four.
For Hanaupah Canyon Fan, weighted profile indices were
similarly calculated twice. The four best properties
included dry consistence, stage of carbonate formation,
lightening, and structure (Table 6). The correlation was
slightly better for weighted profile indices calculated using
the four best properties than all seven properties (Figure
11) .
Using the four best properties was more representative
of total soil formation in that upper (dry consistence and
structure) and lower horizon (lightening and stage of
carbonate formation) properties were equally represented.
When all properties were used, upper horizon properties
a.
b.
Fig. 11.
,. 140
120
100
8
60
40
20
0 0 .5
100
&0
80
70
60
50
40
30
20
10
0 0 .5
J • 74.071• • 55.118, R-aquared: .157
I
1.5 2 log &Oil age
J • 42.211• • 21.042, R-aquered: .153
• • 1.5
log IOilage 2
2.5 3
2.5 3
Plots of weighted profile indices versus log soil age (in thousands of years): a. all 7 properties and b. the best 4 properties.
41
outnumbered lower horizon properties, weighting the index
slightly to upper horizon development.
Calcium Carbonate Equivalence (CCE)
42
CCE values were determined for four pedons on the
youngest surface (Q3b2). Pedons 2, 3 and 4 were located
below a late Pleistocene fault scarp and had inherited some
soil properties from sediments produced by erosion of the
Q3a-lower surface located on the upthrown side, including
stage of carbonate formation. Peden 1 was used to represent
the Q3b2 unit since it was located away from the fault scarp.
Values for CCE were relatively constant with slight increases
from a minimum in the C horizon to a maximum in the A horizon
(Appendix B) .
Q3a-lower pedons had different CCE trends. Maxima were
slightly higher and occurred in C horizons. Minima were
lower and occurred in Bk horizons. Intermediate values
occurred in A horizons whereas rinds from Bk horizons had
much higher values .
Pedons from Q3a-middle reflected the same general trends
as seen in Q3a-lower soils. Minima occurred in Bk horizons
whereas maxima occurred in Av and C horizons.
Distribution of maxima and minima for Q3a-upper soils
was different from younger soils. Minima occurred in Btk
horizons and maxima in Bk horizons, except for pedon 2 where
the maxima was in the A horizon. Values in C horizons were
relatively high as were those in A horizons.
Pedons from Q2a and Q2b-lower reflected the continuation
of trends seen in Q3a-upper soils. Maxima were considerably
higher and occurred in Bk horizons. Minima occurred in A
horizons and Btk horizons continued to have relatively low
values although slightly higher than in Q3a-upper soils.
The presence of fine (<2mm) carbonate in C horizons made
quantification according to the soil development format of
Harden (1982) difficult. During field descriptions, it was
43
noted that there was a very distinct boundary between Btk (or
Bwk) horizons and the uppermost Bk horizon in all but the
Holocene profiles. This boundary was easily determined by
dry consistence, color, structure, and clay accumulation
(where developed) . Differences in CCE values across this
boundary were calculated for each pedon by subtracting Btk
(or Bwk) values from the subjacent Bk horizon values. These
were plotted against log soil age and are presented in Figure
12. Values generally were correlated to soil age (Table 6).
For soils about 32,000 years BP and younger, values were very
low and, with one exception, negative. This indicates that
there were greater amounts of <2mm carbonate in Btk(Bwk)
horizons than subjacent Bk horizons. Values increased
significantly in Q3a-upper pedons where they were positive.
The value for pedon Q2bl-1 was also positive but less so than
in Q3a-upper soils. Pedon Q2a had the highest value of all
soils due to considerable increases in the Bk horizons.
Electrical Conductivity (EC)
Pedons from Hanaupah Canyon Fan had relatively high
soluble salt content as indicated by high electrical
conductivity (EC) values (Appendix B) . The location of many
of the pits at channel cuts may indicate that high salt
content was due to concentration at channel edges by lateral
movement of subsurface moisture. Transects were made on
three of the geomorphic surfaces (Q3a-lower, Q3a-upper, and
Q2a) to determine the effects of channel proximity on soluble
salt content. Each transect began at the channel edge and
was run for approximately 50-60 m sampling the vesicular A
horizon every 10 m. Determinations of soluble salt content
for transects indicated that high EC values were not clearly
related to channel proximity. As a result, EC data
determined from pedons were considered representative of
soils on associated geomorphic surfaces.
12
10 • 8
6 • • • 4
2 • 0 • • •
-2 t 10 • 100 1000
• -4 • -6
Fig. 12. Plot of differences in calcium carbonate equivalence (CCE) values versus log soil age
(in thousands of years) .
44
45
Electrical conductivity values ranged from 0.5 to 298
mmhos/cm. Holocene pedons had the lowest values (0.5-7
mmhos/cm) with maxima in C horizons. The next highest values
occurred in A horizons (0.9-1.6 mmhos/cm). Minima occurred
in Bw horizons. Minima and maxima for the remaining pedons
did not follow any definite patterns. In all older pedons,
except Q3a-upper pedon 1, minima were in C horizons. Av
horizons had a wide range of values (1-144 mmhos/cm) as did
Btk horizons (0.9-298 mmhos/cm) and Bwk horizons (53.4-270
mmhos/cm). Bk horizons had values ranging from 0.8-144
mmhos/cm.
Soil Reaction (pH)
The relatively high soluble salt content made evaluation
and interpretation of pH data in the framework of soil
development indices difficult. Values of pH ranged from 6.9
to 8.6 (Appendix B). As with EC values, there were very few
trends between pH data and either depth or age. The C
horizon values in general tended to be somewhat higher and
Btk horizon values slightly lower. Extremely high EC values
generally corresponded to relatively low pH values (for
example, pedon Q3am-2).
Lowering (Harden, 1982) and increasing (Reheis, 1987) of
pH values with increasing soil age have been used in soil
development indices from xeric and aridic regions,
respectively. Critical to the use of pH was characterization
of the lowest soil horizon described. The high variability
of pH in upper horizons and the unpredictable nature of the
occurrence of high soluble salt concentrations, and their
apparent suppressive effect on pH, made evaluation of changes
with soil age impractical. Preliminary plots of pH values
and soil age indicated that pH could not be used as a
development indices parameter.
[) . . 1SCUSS10D
Soil Development Indices
U~~er horizon ~ro~erties. Changes in property indices
for structure, rubification, clay film development, and dry
consistence, as soil age increased, indicate that they were
closely related to the geomorphic development of associated
fan surfaces. Except for rubification, these properties
reached maxima on surfaces with well developed desert
pavements, typically before 50,000 yr BP. Rubification
developed in the Holocene remained constant until
approximately 145,000 yr BP where very slight increases
occurred. In general, 10YR hues first appeared by about
4,400 yr BP and did not change. Maximum structure was
developed by 15,400 yr BP and clay films by 32,000 yr BP.
Once maxima were reached, soil properties did not develop
further in older soils. Although dry consistence was the
only property to show systematic changes over longer periods
of time (approximately 120,000 years), correlation was poor.
The restriction of development of these four properties
46
(structure, rubification, clay film development, and dry
consistence) to upper horizons strongly suggests different
processes were present than in lower horizons. The
restriction of changes in rubification to A horizons in
Holocene soils, and the observation that the color was the
same for most older upper horizons (over the past
approximately 145,000 years), indicate an aeolian component,
most likely derived from deflation of the associated playa.
Although no data were available from the Death Valley playa,
colors reported for playa sediments in the Panamint Valley,
the next basin west, had the same color (10YR 4/4) as upper
horizons of soils in the current study area (Peterson, 1980).
The presence of highly vesicular fabrics in A horizons
and a less vesicular arrangement in subjacent Btk or Bwk
horizons are indicative of multiple wetting episodes in upper
horizons (McFadden, et al., 1987). Exposure of silty upper
47
horizons to more cycles than lower horizons explains the
better-development of structure, clay films, and dry
consistence. The presence of vesicular horizons under
revarnished patches formed on the exhumed petrocalcic horizon
of 01 indicates that such processes may have been active
during the past approximately 800,000 years.
The thickness of upper horizons (defined earlier as
those horizons where structure, rubification, clay films, and
dry consistence have developed) is related to geomorphic
development. Minima (1-2 em) occurred in Holocene pedons
(about 4,400 yr BP) whereas maxima (up to 40 em) were in the
next oldest fan unit sampled (approximately 15,400 yr BP),
the late Pleistocene Q3a-lower surface which corresponded to
the youngest desert pavement. Thickness decreased
considerably (< 20 em) to the next oldest surface, Q3a-middle
(32,000 yr BP) and continued to decrease over the next
approximately 100,000 years.
Decreases in thickness after maxima were reached at
approximately 15,400 yr BP corresponded to increased
incision, dissection, and erosion of desert pavements as age
increased. Such decreases are interpreted as thinning due to
increased erosion in response to uplift. Eventually there
was complete removal of upper horizons and exhumation of a
petrocalcic horizon sometime between about 145,000 and
800,000 yr BP.
Lower horizon properties. Development of lower soil
horizons was characterized by properties associated with
accumulation of calcium carbonate (CaCOJ) . These properties
included thickness of the zone of accumulation, lightening of
color, stage of calcic horizon formation, and distribution of
fine (< 2mm) CaC03 as reflected in CaC03 equivalence (CCE) .
The thickness of the zone of carbonate accumulation
increased as soil age increased. The greatest single
increase occurred from Holocene to late Pleistocene (Q3a
lower) surfaces. Such increases indicate that there was
continued movement of CaC03 into the Bk horizons over at
least the past 800,000 years (early to middle Pleistocene)
48
Non-zero index values for color lightening first
appeared in Q3a-upper (50,000 yr BP) pedons in Bk and C
horizons. As originally defined, lightening was used for
quantification of color changes due to accumulation of
pedogenic CaC03 (Harden and Taylor, 1983) . In C horizons of
the Q3a-upper and older pedons, lightening may indicate
changes in parent material colors, or accumulation of fine
CaC03 as soils thickened downward. No lightening occurred in
Q3a-middle or Q3a-lower horizons, which were part of the same
fan unit as Q3a-upper, indicating that the colors observed in
Q3a-upper were probably not due to parent material
differences. This suggests that the lightening of color in C
horizons in the Q3a-upper pedon was probably due to
accumulation of CaC03. All older profiles had a similar
lightening of color in Bk and C horizons. The C horizons
colors may have resulted in part from incipient accumulation
of fine (< 2mm) pedogenic CaCOJ.
Carbonate accumulation in Holocene profiles consisted of
thin discontinuous stage I coatings on clasts. Stage II
CaC03 accumulation was developed by approximately 15,000 yr
BP on Q3a-lower, expressed by thicker (2-5 em) continuous
rinds on clast bottoms. Older profiles on the Q3a unit
(32,000 and 50,000 yr BP) had the same stage of formation and
similar distribution of CaC03 on clasts. Pedons for the
lower Q2 unit (approximately 120,000 yr BP) exhibited
indurated stage III CaC03 accumulation. Upper parts of the
indurated zone were characterized by an eroded rubbly
appearance, and the overlying Btk and Bk horizons were thin
(<20 em) with loose eroded rinds. Bk horizons overlying the
petrocalcic horizon were also characterized by loose rinds.
The presence of minor amounts of detrital CaC03 in the
parent material (Hunt and Mabey, 1966) and a considerable
aeolian component of the upper horizons, as indicated by
49
upper horizon properties and particle size distribution,
suggest that pedogenic carbonate accumulation was largely due
to an aeolian source. Accumulation of carbonate-rich aeolian
material and translocation into lower horizons is indicated.
Dissolution of CaC03 rinds in upper Bk horizons of older
soils also contributed to accumulation in lower horizons as
the soil thickened downward. Dissolution of rinds became
more important in soils beginning approximately 50,000 yr BP
as increased erosion of the soil resulted in decreased
preservation of aeolian CaCOJ. Development of petrocalcic
horizons in older soils, while erosion removed upper horizons
and associated surface aeolian accumulations, indicates that
dissolution of rinds became increasingly important as a
source of CaC03 for lower Bk formation.
Horizon Indices
Horizon indices, when viewed chronologically, indicate
reworking of upper horizons in older soils. Although upper
horizon thickness decreased, pedogenic redistribution of soil
material continued as indicated by vesicular fabric in all
upper horizons, where present.
Maxima in horizon indices shifted from A to Btk horizons
between 32,000 and 50,000 yr BP, but always remained in upper
horizons and indicate more pronounced soil development, most
likely in response to more wetting episodes. Values
increased very little beyond 50,000 yr BP due only to slight
changes in dry consistence. Index values reached a maximum
at the greatest depth in soils at 50,000 yr BP because of the
appearance of clay films in all profiles. Maximum index
values occurred higher in the profile as upper horizon
thickness decreased on older surfaces in response to
increased erosion.
Lower horizon indices were considerably lower and
reached maxima much more slowly than upper horizons. Indices
reached a maximum by approximately 120,000 yr BP due to
increases in color lightening and changes from stage II to
stage III of carbonate formation. Color lightening was
responsible for non-zero values for C horizons beginning
approximately 50,000 yr BP, and is interpreted as an
indication of incipient pedogenic CaC03 formation as Bk
horizons thickened downward.
Profile Indices
50
When indices of all properties are combined into one
index (profile index), it puts a number on a soil profile to
represent its total development. The use of that number, in
terms of evaluating soil formation, is limited. However, one
of the reasons for using the profile index is for preliminary
association of total soil development with geomorphic
development. A profile index allows the assignment of
relative ages and permits correlation of surfaces where no
age control is available (Harden, 1982) .
Profile indices from soils on Hanaupah Fan were viewed
in this manner. For the purpose of correlation, the best
four properties were used; however, the plot of indices
versus log of soil age created considerable errors in age
estimation (Table 6) . A slight change in the profile index
yielded a considerable change in age. Of all properties used
for index calculations, the stage of carbonate formation
correlated the best with soil age, but age changes were also
exaggerated with small changes in the property index. Soils
with similar stage of formation, e.g., stage II, occurred
over a long span of time (approximately 15,000 to as much as
120,000 yr BP).
The field measurement with the best correlation to soil
age for soils described in this study was the thickness of
the zone of CaC03 accumulation. This parameter was not used
by Harden (1982). The best correlation was obtained when it
was plotted versus linear soil age, so that slight changes in
thickness did not affect such profound changes in age.
51
Similarly, total soil thickness (to the bottom of the zone of
carbonate accumulation) was also a good estimate of soil age.
Calcium Carbonate Equivalence (CCE) and Electrical Conductivity (EC)
In Holocene soils (Q3b2) CCE values for < 2mm fraction
increased systematically from C to A horizons and probably
represent detritus in alluvial parent materials, although
slightly higher values in the A horizons may have resulted
from additions of aeolian material. Values from the Q3a
lower and -middle pedons suggest that carbonate accumulated
in the surface horizon (presumably as aeolian material) and
precipated as rinds on clasts in Bk horizons, effectively
removing it from the <2mm fraction. This trend changed for
soils about~ 50,000 yr BP. Values in these soils suggest
that there was degradation and removal of pedogenic carbonate
from Av, Btk, and upper Bk horizons into lower Bk horizons in
response to increased uplift and dissection of fan surfaces.
Minima in A horizons may also have resulted from removal by
surface erosion.
Values from the Q2b-lower and Q2a profiles showed
similar trends to those for the Q3a-upper pedons. Values
indicate removal of CaC03 from upper horizons and
accumulation in upper Bk horizons.
The distribution of CCE minima in Bk horizons and maxima
in surface horizons for profiles younger than approximately
50,000 yr BP may also be explained by capillary movement.
Surface drainage of soils on younger surfaces was inherently
slower than on older surfaces due to a less developed
drainage system. After wetting, soil moisture moved upward
from the soil to the surface. Movement from Btk or Bwk
horizons dissolved carbonate and concentrated it in surface
horizons as the moisture evaporated. The identification of
authigenic carbonate crystals in the soil matrix of upper
horizons supports such an interpretation. These will be
discussed in detail later (CHAPTER IV) .
52
Soluble salt content (EC) was typically very high for
pedons from Hanaupah Canyon Fan. Studies on the effects of
aeolian salt accumulation in soils in the Mojave Desert
(McFadden, et al., 1986; Peterson, 1980) reported high
soluble sodium salt contents for soils in the region.
Argillic and natric horizon development in the Panamint
valley were attributed to translocation of aeolian clay in Av
horizons (Peterson, 1980). Salts were concentrated in the Av
horizons due to capillary movement of water as the soils
dried. Leaching of the salts during storms resulted in lower
concentrations and subsequent clay dispersion and
translocation. Natric horizons developed in alluvial
sediments in less than 10,000 years and probably in the last
approximately 3,500 years in the Panamint Valley. McFadden,
et al. (1986) presented an aeolian interpretation for the
origin of relatively high soluble salt and calcium carbonate
accumulations in soils from the Cima volcanic field during
the Holocene. McFadden, et al. (1987) extrapolated this data
to alluvial fans in the Mojave Desert. Silty vesicular A
horizons and upper B horizons on fans were interpreted as
recording increased aeolian activity during the late
Pleistocene and the Holocene.
The distribution of EC values and thicknesses of upper
horizons directly affected by aeolian additions for soils on
Hanaupah Canyon Fan are viewed here in terms of the model of
McFadden, et al. (1987). The relatively high EC values and
their erratic distribution in relation to geomorphic position
(Appendix C) support the interpretation that salt
accumulation was recent (Holocene) . Longer periods of salt
accumulation would probably show better correlation to
geomorphic position than observed, such as proximity to
channels and the associated playa.
Low EC values on Holocene soils were somewhat
surprising. Peterson (1980) reported high salt content on
soils younger than approximately 3,500 yr BP from alluvial
53
deposits in the Panamint Valley. Holocene soils described
from Hanaupah Canyon Fan in this study were dated
approximately 4,400 yr BP (Dorn, 1988). The low soluble salt
content is best explained by surface morphology and
geomorphic position. Holocene soils retained original bar
and channel morphology and were topographically the lowest
alluvial units in the study area. As a result, they were the
recipient of runoff from older, higher units with desert
pavements. The bar and channel surface morphology resulted
in very little runoff and deeper leaching of soluble salts in
aeolian dust trapped in the rough surface. Values of EC and
in the Holocene pedon were therefore relatively low.
The interpretation of A and upper B horizons as records
of late Pleistocene and Holocene aeolian activity (McFadden,
et al., 1987) does not agree with other chemical data in this
study. Several lines of evidence indicate that most Holocene
aeolian deposition was not preserved on fan units with desert
pavements, in particular older units where drainages were
better developed.
First, CCE values on <2mm carbonate from A horizons
systematically increased until a maximum was reached by
approximately 50,000 yr BP; they then decreased considerably
on older soils. This corresponded to changes in soil
properties and geomorphic evolution of fan units.
Preservation of Holocene, CaC03-rich, aeolian material in
surface horizons of older soils should have had higher fine
(<2mm) CaC03 content that was comparable to younger soils.
Instead, values were lower and indicate removal from surface
horizons. Soils younger than approximately 50,000 yr BP
reflected better preservation of Holocene carbonate
accumulation in surface horizons, although it may have been
due to other factors not related to aeolian activity as
discussed below. The Q3b2 pedon had slightly higher CCE
values in upper horizons that probably recorded Holocene
aeolian deposition.
Second, capillary movement was apparently partially
responsible for concentration of carbonates in surface
horizons in soils where a pavement was present. This
probably involved removal of older pedogenic carbonate from
Bk horizons, in which case upper horizon accumulations did
not necessarily reflect Holocene aeolian deposition.
54
Last, low soluble salt content in upper horizons of the
Q3b2 profile (approximately 4,400 yr BP) did not reflect
preservation of Holocene aeolian salts. Instead, it was most
likely the result of deeper leaching due to geomorphic
position in which soluble salts were moved through the
profile.
Soil Development and Geomorphic Evolution of Fan Units
Soil development was closely related to the formation of
desert pavements. Recently abandoned, active channels
provided effective traps for aeolian materials and continued
to serve as effective dust traps after abandonment until a
desert pavement formed (Jessup, 1960; Mabbutt, 1977;
McFadden, et al., 1987). At the same time, recently
abandoned channels were topographically lower than adjacent
older, higher surfaces with desert pavements. This position
formed a 'basin' for runoff from older surfaces, where runoff
was greater due to the presence of a desert pavement. The
relatively high amounts of dust and water concentrated on
these recently abandoned deposits allowed for relatively
rapid initial soil formation. Eventually, a smooth desert
pavement formed from the bar and channel deposit as uplift
continued. As the pavement formed, the deposits become much
less effective dust traps and runoff increased. The combined
effect of pavement formation and uplift was a considerable
increase in erosion of the pavement, as reflected by
development of a network of shallow internal drainages by
approximately 15,400 yr BP. Soil development also reflected
these changes, as the thickness of upper horizons affected by
aeolian additions peaked on the youngest pavement (about
15,400 yr BP) and decreased with increasing age.
After pavement formation, wetting episodes reworked
upper horizons, resulting in increased development of clay
films, structure, and dry consistence. In general, maximum
development of upper horizon properties occurred by
approximately 50,000 yr BP. Dry consistence was the
exception, although it changed very slowly. Soluble
materials, such as CaC03, were moved deeper into lower
55
horizons, although capillary movement may have returned some
to the surface. Erosion and dissolution of upper horizons of
pedogenic carbonate accumulation were evident by
approximately 50,000 yr BP as reflected by loosening of rinds
and changes in distribution patterns of fine (<2mm) carbonate
) (CCE) . Dissolved carbonate was moved further downward into
the soil and accumulated in the lower Bk and, apparently, C
horizons, eventually cementing the Bk into a Bkm
(petrocalcic) horizon by approximately 120,000 yr BP. Former
C horizons became Bk horizons as the zone of carbonate
accumulation moved downward. This change was also evidenced
by the continual increase in thickness of the carbonate-rich
zone with increasing soil age. While the zone of carbonate
accumulation was thickening downward, the upper parts were
eroded until eventually petrocalcic horizons were exposed and
became incorporated into desert pavements. This type
pavement first occurred at the gulley edges of unit Q2b-lower
(120,000 yr BP). Eventually, overlying horizons were removed
and the petrocalcic horizon was exposed and eroded, e.g., on
the oldest fan unit, Q1a.
Paleoclimatic Data
Trends in soil development on Hanaupah Canyon Fan were
mostly in response to changes in age and topography as
discussed earlier. The effects of paleoclimatic changes also
56
have to be considered. There is considerable independant
paleoclimatic data from Death Valley: desert varnish analyses
(Dorn, et al., 1987; Dorn, 1988); Neotoma plant macrofossil
assemblages (Wells and Woodcock, 1985); and drill cores from
the basin (Hooke, 1972) . Only studies of varnish chemistry
allow for interpretation of environmental change during the
length of fan deposition represented by preserved fan units
(approximately 800,000 years). Dorn, et al. (1987) and Dorn
(1988) analyzed the chemistry of desert varnish from several
alluvial fans in Death Valley proper, including Hanaupah
Canyon Fan. Analyses included stable 13c isotopes on organic
matter and Mn/Fe ratios, from basal layers of the varnish.
More humid conditions were represented by more negative (-22)
13c values and higher Mn/Fe ratios while more arid conditions
were represented by less negative (-15) 13c values and lower
Mn/Fe ratios. Signals representative of humid conditions
were found in basal layers for units Q1a, Q2a and Q3a while
signals indicating arid conditions were obtained from basal
layers of Q1b, Q2b and Q3b. Q1a-b, Q2a-b and Q3a-b represent
three cycles of alluvial fan deposition that began with humid
conditions related to previous stands of extinct Lake Manly
for Q2 and Q3 cycles (Hooke, 1972) . Each cycle ended with an
arid phase. Data from Neotoma middens and core data agreed
with varnish chemical data on the timing of the end of Q3a
deposition and the beginning of Q3b deposition approximately
12,000 to 10,000 yr BP.
Soil development based on interpretation of field data
from Hanaupah Canyon Fan did not reflect the cyclicity seen
in desert varnish, lake level, and paleovegetation records.
The differences between Holocene (4,400 yr BP) and late
Pleistocene (15,400 yr BP) soils can be explained by changes
in surface morphology and topographic position without
invoking severe climatic changes. The two pedogenic
processes dominating soil development were (1) incorporation
of aeolian materials into upper horizons and (2) accumulation
57
of calcium carbonate in lower horizons. Amounts of aeolian
dust added to the fan surface are sensitive to climatic
change. There is evidence for water in the playa basin (Lake
Manly) during periods Q2a and Q3a. At such times, less dust
would be produced. More arid periods correspond with
dessication of Lake Manly and greater areal extent of the
playa, resulting in greater deflation of playa sediments.
The addition of aeolian materials to the surfaces of soils on
Hanaupah Fan was indicated by silty textures and colors of A
horizons. Uplift of the older fan units and the subsequent
gulley development resulted in erosion of upper soil
horizons, although A horizons below desert pavements were
maintained until complete removal of upper horizons between
approximately 145,000 and 800,000 yr BP. Chemical analyses
of upper soil horizons exhibited no good systematic changes
with age. As a result there was no clear evidence of effects
of paleoclimatic change preserved in upper horizons.
Lower horizons were characterized by the accumulation of
calcium carbonate provided primarily by aeolian materials at
the soil surface in younger soils. In older soils,
additional carbonate was provided by dissolution of older
pedogenic CaC03 and subsequent translocation downward. The
morphology and thickness of carbonate accumulation
systematically changed with increasing age. Deposition of
CaC03 in lower horizons of all soils studied suggest that
they may have been more sensitive to climatic changes than
upper horizons which began as zones of deposition in younger
soils then became zones of removal in older soils. Plots of
thickness and stage of carbonate formation versus age did not
yield any conclusive evidence of climatic change. Although
greater amounts of precipitation during more humid (semiarid)
periods probably resulted in deeper leaching of carbonates,
evidence of such periods was not apparent since the depth of
soil formation in the study area increased with age over the
past approximately 800,000 years. The thickness of the zone
of carbonate accumulation, similarly, did not reflect
paleoclimatic changes.
58
Methods
CHAPTER III
CLAY MINERALOGY
Five pedons were analyzed for clay minerals by X-ray
diffraction (XRD) . Samples were air-dried, passed through a
2-mrn seive and the <2mm fraction used for subsequent
analyses. Indurated horizons were not analyzed by XRD.
Carbonates were removed from approximately 20-30 grams of
sample using 10% acetic acid. After destruction of CaC03,
organic matter was removed with successive treatments of
approximately 13%, 20% and 27.5% hydrogen peroxide.
Carbonate- and organic-free samples were suspended in
deionized water and decanted until gypsum and more soluble
salts were removed, as indicated by dispersion. Once samples
started dispersing, approximately 5 milliliters (ml) of
Calgon solution was added. Samples were stirred and allowed
to settle. Clays were siphoned at the appropriate times
determined by Stokes Law.
Two samples of clay from each horizon were prepared for
XRD analyses. In the first, clay suspensions were saturated
three times with approximately 5 ml of 0.3N calcium chloride
(CaC12). ca2+-saturated samples were then washed with a 1%
glycerol solution to remove excess ca2+ and expand
interlayers of smectites. The clay suspensions were then
placed on aluminum slides, allowed to dry at room
temperature, then further dried in an oven at 60 C to remove
excess glycerol.
A second set of samples were saturated three times using
a 0.3N solution of potassium chloride (KCl) then washed with
deionized water. Clay suspensions were placed on aluminum
slides and dried at room temperature. Samples saturated with
K+ were analyzed three times; at room temperature, after
heating to 250 C, and after heating to 550 C.
59
X-ray analyses were performed using a Phillips-Norelco
diffractometer operated at· 40 kV and 20 rnA. Ni-filtered Cu
K-alpha radiation was used at a scanning speed of 2 degrees
per minute from 2 to 30 degrees 20. X-ray analysis of the
aluminum slide over this range indicated aluminum peaks at
approximately 6 and 4A. Upon heating the slides to 550 c, the 4A peak commonly showed a considerable increase in
intensity.
Preliminary analyses were also run for bulk powder
samples of pedogenic CaC03 rinds in Bk horizons for six
pedons. Samples were scanned from 2 to 20 degrees 20.
Results
Q3b2 Pedon 1 (4,400 yr BP)
The clay assemblage in this pedon showed very little
change with depth (Figure 13) . Relative abundance of clays
are presented in Table 7 and follow the sequence: mica >
chlorite > smectite > kaolinite > talc. Peaks for all clays
were relatively sharp and distinct. Peaks for the aluminum
slide occurred at approximately 4 and 6A.
60
Smectite was indicated by the 18A line (001) reflection
in ca2+-glycerol samples. Chlorite was identified by 14.0-
14.2 (001), 7.0-7.1 (002), 4.75 (003) and 3.53 A (004)
reflections. The persistence of the 001 reflection through
the heating of potassium-saturated samples to 550 degrees C
confirmed the 14 A reflection as that of chlorite. Intensity
of the 001 reflection increased considerably with heating
while higher order reflections showed decreases. Similar
changes in intensity have been identified for chlorites in
soils (Barnhisel, 1977) .
In all horizons, mica was the dominant clay indicated by
10, 5 and 3.3A reflections, representing 002, 004 and 006
reflections, respectively. Talc was present in minor amounts
as indicated by the 9.33A line (001). The 001 reflection for
kaolinite (7.1-7.15A) occurred very close to the 002
A(Av)
~l
- ...... .
\ BC
•• t ••. -
Bw
\)\_J::J.v-~~J
' I II. I I •, I t• I r I • I
• ·CAl· •
' .. . '. . .. . , . ..... -
I I 6 I I
' I I .I
Fig. 13. Diffraction patterns for pedon 1, unit Q3b2.
61
62 Table 7. Relative percentages of clay minerals.•
Horizon sm+ Chl p Mica K Talc s
Q3b2 pedon 1 (4,400 yr BP) Av xxxx XXX xxxx XX X Bw XX XXX xxxx X X BC XXX XXX xxxx X c XXX XXX xxxx X X
Q3a-lower pedon 3 (15,400 yr BP) Av X XX X xxxx X X Bky X X XX xxxxx X Bkl XX XXX XXX xxxx X X Bk2 XX XXX xxxx XXX X X c XX XXX xxxx X X
Q3a-upper pedon 2 (50,000 yr BP) Avz X X X XXX XX X Btkz XX XXX XX XXX X X Bku XX XXX XXX XXX X X
Bkl XX XXX XXX XXX XX XX c XX XXX xxxx X
Q2b-lower pedon 1 (120,000 yr BP) Av XXX X X xxxx X X Btk XX X XX xxxx XX X Bk1 X XXX xxxx XXX X X Bkm++ Bk2 xxxx XXX XX X X XX XX
c XX XXX xxxx X X
Q2a pedon 1 (145,000 yr BP) Av XXX X X XXX X X AB XX XX XX xxxx X X Bty X XX X xxxx X X
Bky1 XX XXX xxxx XXX XX XX
Bky2 X XX X xxxx X X?
*Relative quantities: XXXXX = > 50%, XXXX = 35-50%, XXX = 20-35%, XX = 10-20%, X = < 10%
+sm= Smectite, Chl= Chlorite, P= Palygorskite, K= Kaolinite, S= Sepiolite
++Horizon not analyzed for clay mineralogy.
63
reflection for chlorite. Minor amounts of kaolinite were
confirmed by the presence of the 002 reflection at 3.55-
3.58A, which formed a small shoulder to the left of the 3.53A
(004) chlorite peak, and the dissappearance of the 7.1 and
3.55-3.58A reflections upon heating to 550 C. Very little
quartz was present in the clay fraction as indicated by the
small peak at 4.3A (100). Relative proportions of clays from
this pedon showed very little change with depth.
Q3a-lower Pedon 3 (15,400 yr BP)
Clay mineral assemblages in this profile followed the
sequence: mica > chlorite >palygorskite > smectite > talc
for the A and Bky horizons (Figure 14). Minor amounts of
kaolinite were present in the A horizon but were absent in
the Bky horizon. Small amounts of palygorskite occurred as
indicated by the 10.6A (110) reflection located to the left
of the lOA mica peak. Other palygorskite reflections were
not distinct. Very little smectite was present as indicated
by the lack of a distinct 18A peak in the ca2+-glycerol
sample. Minor amounts of chlorite were present as seen by
reflections at 14.1A (001). Minor amounts of talc and
kaolinite were also present.
The Bk horizon had a different clay mineralogy. Mica
and palygorskite were present in approximately equal amounts
and comprised most of the clay. Palygorskite was identified
by the 10.6 (001), 6.4 (200), 5.4 (130), 4.5 (040) and 3.2A
(004) reflections. Of these, the 10.6A reflection was the
strongest, most distinct peak, with the remainder appearing
as relatively small broad peaks. Moderate amounts of
chlorite, comparable to the Holocene pedon, were present.
The C horizon clay mineral assemblage was similar to
that of the Q3b2 profile (Holecene) and consisted
predominantly of mica with moderate amounts of chlorite and
minor amounts of smectite, talc, and kaolinite. Palygorskite
was absent from the C horizon.
............
Bkl
"' ••••••••••••••••••••••••••••••• . . ... . .
A(Av)
• •• . . ... . . ••• • •••••
•••• •••• ••••
.. ......... .
• • ••• ••• • ••••• . ..... .
Bky 64
1.1 •.• ... . ..... . ...... .
c
I I ll.a te I 11.1 1.1 1.1 • • • ••• . ......
Fig. 14. Diffraction patterns for pedon 3, unit Q3a-lower.
Q3a-upper Pedon 2 (50,000 yr BP)
Clay mineral distribution in the upper horizons was
similar to that in the upper horizons of the Q3a-lower pedon
(Figure 15) . The dominant clay was mica with minor amounts
of palygorskite (10.6 A). Smectite, chlorite, talc, and
kaolinite were also present in minor amounts.
65
The Bk horizon was split into upper and lower units and
both were characterized by increasing amounts of all other
clay minerals relative to mica. Palygorskite increased
considerably and was the most abundant clay followed by mica
> chlorite with minor amounts of smectite, talc and
kaolinite. The C horizon was predominantly mica with
moderate amounts of chlorite and minor smectite and talc.
Neither kaolinite nor palygorskite occurred in the C horizon.
Q2b-lower Peden 1 (120,000 yr BP)
Mica was the major clay mineral in the upper horizons
with minor amounts of palygorskite, chlorite and talc (Figure
16) . Smectite and kaolinite were slightly higher in upper
horizons (A and Btk) than in the previously discussed pedons.
Smectite peaks were broader than in the lower horizons.
The Bkl horizon exhibited significant increases in
palygorskite while smectite decreased markedly relative to
overlying horizons. Chlorite increased slightly in
comparison to that in the Holocene profile. The Bk2 horizon
was located below the Bkm and was characterized by a
considerable increase in smectite and a decrease in
palygorskite. Sepiolite was probably present in moderate
amounts as indicated by the 12.2A (110) reflection. Chlorite
and talc increased slightly in the Bk2 horizon. Clay
mineralogy of the C horizon was similar to that in younger
pedons and was dominated by mica with moderate amounts of
chlorite and minor smectite, talc, and kaolinite.
Az (Avz) Btkz
·-···
1 I .... .... .... '·' ... ... . ..... ••·• ••·• ••· • ••·• r.' •·• 4.1 1.1 I I
Bk(upper)
I .... .... .... .... '·' ... . . .... . . ... . .....
........
Bk(lower)
I ................ '·' ... . . .... . . I
••• • ••••
• ...... 0
tl.e It I ll.e
66
c
I I
' . . . t I I 4 I I ........ Fig. 15. Diffraction patterns for pedon 2, unit Q3a-upper.
Bkl
\
Fig. 16.
A(Av)
o I
•••• ••• • •• . .. ........
I I .... .... .... ... . .. ........
ll.e •• I 11.1
••• • •••••
67
I I. I I e • e 1.1 I I . ...... .
c
II I t• I te.e I I I I e I I I I I . .......
Diffraction patterns for pedon 1, unit Q2b-lower.
68
Q2a Peden 1 (145,000 yr BP)
Upper horizons (Av, AB, and Bty) had a clay mineralogy
(Figure 17) similar to that in the Q2b-lower pedon. The Av
and AB horizons were predominantly mica with moderate amounts
of smectite. Lesser amounts of chlorite and palygorskite
were present with minor amounts of kaolinite and talc. The
Bty contained mostly mica with minor amounts of chlorite and
kaolinite.
The two lower horizons (Bkyl and Bky2) had different
clay mineral assemblages. Palygorskite and mica were the
major minerals in the Bkyl and there was a considerable
increase in palygorskite relative to overlying horizons.
There were also slight increases in smectite, chlorite, and
talc. Minor amounts of sepiolite (?) and kaolinite were
present. The Bky2 horizon had considerably less palygorskite
and was characterized by high mica content with moderate
amounts of chlorite and palygorskite, lesser amounts of
smectite and minor amounts of talc and kaolinite.
Pedogenic Carbonate Rinds
Preliminary analyses of bulk samples of CaC03 rinds on
undersides of clasts were analyzed from six pedons ranging in
age from approximately 15,400 to 145,000 yr BP (Table 8).
Mica was the major clay mineral in all samples and was
characterized by a sharp, distinct peak at approximately lOA.
Chlorite was also present in all pedons, although in minor
amounts and was recognized by peaks at approximately 14 and
7A. Palygorskite was identified in minor amounts in pedon
one of unit Q3a-lower and pedon 3 of the Q3a-middle.
Moderate amounts were present in pedon 2 of unit Q3a-lower.
Minor amounts of palygorskite may have been present in pedon
1 of unit Q3a-upper and pedon 1 of unit Q2b-lower. No
palygorskite was indentified from the Bkyl horizon of the Q2a
pedon.
I .. . .. . .. . ' .
Bty
•• ....... Fig. 17.
•.• I I I I
A(Av)
c •••• ,
.....
... ... ... . .. .......
Bkyl
'' U.l U I 11.1 tl.l 1.1 1.1 1.1 . ......
AB
I f .I I e e e 1.1 I I
. ......
Bky2
• I I I I I 11.1 lt.l II I f I •• . .. . .. .. .
Diffraction patterns for pedon 1, unit Q2a.
69
. . . .. '
Table 8. Relative clay mineral content in pedogenic CaC03 rinds from XRD analyses of bulk samples.*
70
horizon mica chlorite palygorskite
Q2a (145,000 yr BP) Bky1 XXX X -----
Q2b-lower (120,000 yr BP) pedon 1, Bkl XXX X X (?)
Q3a-upper (50,000 yr BP) pedon 1, Bku XXX X X (?)
Q3a-middle (32,000 yr BP) pedon 3, Bk1 XXX X X
Q3a-lower (15,400 yr BP) pedon 2, Bk1 XXX X XX
Q3a-lower (15,400 yr BP) pedon 1, Bku XXX X X
*xxx- major, XX= moderate, X= I
m~nor
71 D . . lSCUSSlOn
Clay mineral assemblages for most horizons consisted of
detrital smectite, chlorite, mica, talc, and kaolinite.
Authigenic clay minerals included smectite, palygorskite, and
possibly sepiolite in one horizon. The discussion of clay
mineral assemblages here will focus on authigenic (pedogenic) minerals.
Q3b2
The Holocene pedon assemblage (Q3b2) showed relatively
little change throughout the profile. This distribution
indicates that the assemblage was inherited (detrital) from
the alluvial parent material and was relatively unaffected by
pedogenesis. The C horizons of all older pedons had similar
suites and relative abundance of clay minerals. Thus, the
clay mineral assemblage of C horizons was used to approximate
that of the parent material in evaluation of assemblages in
older pedons.
Q3a-lower
The next oldest pedon (about 15,400 yr BP) was located
on the late Pleistocene Q3a-lower surface. The clay
mineralogy of the C horizon was similar to that of the
Holocene pedon. The presence of palygorskite in all but the
C horizon indicates that it was authigenic and not inherited
from the parent material.
Although there was evidence of suppression of pH by high
soluble salt content in some horizons (Appendix A), upper
horizons generally had lower pH values (7.6-8.0) than lower
horizons (8.0-8.4). The increase in soil pH with depth
corresponded to increases in palygorskite content, indicating
that soil conditions in lower horizons were more favorable
for preservation and possibly formation of palygorskite
(Jones and Galan, 1988) .
72
Thus, the presence of minor amounts of palygorskite in
upper horizons was suggestive of an aeolian source. Aeolian
palygorskite has been recognized from arid regions based on
SEM analyses (Coude-Gaussen, 1987) and interpreted as such in
arid soils (Shadfan and Mashhady, 1985; Lee, et al., 1983;
Aba-Husayn and Sayegh, 1977; Elprince, et al., 1979).
Three different explanations may be offered for the
lower amounts of smectite in upper horizons. First, smectite
may have suffered alteration to palygorskite (Jones and
Galan, 1988). It may also reflect a relative increase in
smectite content in the lower horizons. The amounts of
smectite in lower horizons did not show an increase from that
in the Holocene pedon, indicating that there was probably no
synthesis of smectite in lower horizons. Alternatively,
smectite in upper horizons may not have been present in
amounts comparable to the Holocene pedon due to dilution by
aeolian influxes of smectite-poor material. This
interpretation is supported by similar relative decreases in
more stable, detrital minerals such as chlorite and talc in
upper horizons. Consistent amounts of mica throughout the
profile suggest that it may have been a major clay component
of aeolian accumulations.
The significant increase of palygorskite content to
moderate amounts in the Bk1 horizon may have been a result of
translocation of aeolian palygorskite from upper horizons,
neoformation, translocation from eroded carbonate rinds in
upper horizons, or a combination of formational modes.
Q3a-upper
The clay mineral assemblage of the Q3a-upper pedon
(approximately 50,000 yr BP) was similar to that of the Q3a
lower. Minor amounts of palygorskite were present in upper
horizons even though pH was only slightly alkaline (7.2-7.4).
High palygorskite content in Bk horizons was probably due to
translocation of aeolian material, removal from associated
carbonate rinds, and possibly neoformation.
73
Smectite in Q3a-upper Av and Btk horizons was
interpreted as authigenic. Previous researchers (Bigham, et
al., 1980; Lee, et al., 1983) indicated that palygorskite may
alter to smectite as its stability decreases. Alteration of
aeolian palygorskite to smectite is suggested in upper
horizons by increases in smectite while detrital clay
contents decrease.
Q2b-lower
Smectite and mica in upper horizons and palygorskite in
lower horizons dominated the clay mineralogy in this pedon.
Smectite content increased similar to that in upper horizons
of the Q3a-upper pedon, and is also interpreted as
authigenic. The absence of palygorskite and the presence of
moderate amounts of smectite in upper horizons support the
interpretation that it was an alteration product of
palygorskite. It also suggests that there has been little or
no replenishment of aeolian palgorskite in upper horizons.
The Bk1 horizon had very high palygorskite content
representing accumulation by processes indicated in the Q3a
upper pedon. Preservation and possibly neoformation of
palygorskite was partially due to slightly higher pH values
(8.2) than in the overlying horizons (7.9).
The Bk2 underlied the petrocalcic horizon and contained
minor amounts of palygorskite, significantly more smectite,
and moderate amounts of sepiolite. The occurrence of
sepiolite suggests that conditions for hermite formation
changed relative to overlying horizons, possibly in response
to formation of the petrocalcic horizon.
Q2a
The clay mineral assemblage in the Q2a pedon
(approximately 145,000 yr BP) was generally similar to that
of the Q2b-lower pedon. The absence of palygorskite and the
presence of moderate amounts of smectite in upper horizons
are interpreted similarly as representing alteration of
relict palygorskite accumulations to smectite.
The Bky1 horizon was comparable to the Bk1 of the Q2b
lower pedon in that palygorskite content was highest in the
Bk horizon immediately below the Btk horizon. Accumulation
in the Bky1 horizon is also interpreted as a result of
translocation of palygorskite from overlying horizons,
followed by accumulation of gypsum. Neoformation of
palygorskite is also possible.
Rinds
74
Analyses of bulk samples of pedogenic CaC03 rinds in the
uppermost Bk horizons suggest that there was removal of
palygorskite as soil age increases. The younger samples
(approximately 15,400 to 32,000 yr BP) had minor to moderate
amounts, while older samples (50,000 to 145,000 yr BP) had
little or no palygorskite. Loosening of rinds in uppermost
Bk horizons generally paralleled the absence of palygorskite
in rinds. On samples approximately 50,000 yr BP and older,
rinds were typically very loose, detached from clasts, and
showed indications of considerable dissolution in upper Bk
horizons. The maximum palygorskite content in each pedon
occurred in the uppermost Bk horizon, suggesting that there
is removal of palygorskite from rinds.
Authigenic Clays
Palygorskite and sepiolite. The palygorskite content
was relatively high in pedons approximately 15,400 yr BP and
older with maximum content in the uppermost Bk horizons. The
highest content was in the Bk1 horizon of the Q2b-lower pedon
where it was approximately 75% (Table 7) . Conditions in the
Bk horizons were favorable for palygorskite preservation as
75
indicated by more alkaline pH values and less intense erosion
than in the upper horizons.
Minor amounts of palygorskite were present in upper
horizons from pedons approximately 15,400 to 50,000 yr BP in
age. In older soils, it was either absent or present in very
minor amounts. Upper soil horizons of all pedons older than
4,400 yr BP had slightly alkaline pH values and other soil
conditions unfavorable for preservation of palygorskite.
Thus,the presence of palygorskite in upper horizons would
suggest either a detrital origin (parent material) or an
external source (aeolian) . The absence of palygorksite in C
horizons of every pedon analyzed does not support an argument
for a detrital source. The presence of minor amounts in
upper horizons of units Q3a-upper and Q3a-lower strongly
indicates an aeolian origin for palygorskite, most likely
derived from deflation from the associated playa and other
basins in the region.
Sepiolite was found in the Bk2 horizon of the Q2b-lower
pedon, located immediately below an indurated petrocalcic
horizon (Bkm) . The absence of sepiolite in the subjacent C
horizon suggests that its presence in the Bk2 horizon was
probably authigenic, as does its absence above the
petrocalcic horizon. The location of sepiolite in the Bk2
horizon suggests that formation of the overlying Bkm horizon
may be related to its occurrence. The location of the Bk2
several meters above and the presence of the water table
several meters below the channel floor (Hunt, et al., 1966)
argues against the possibility of sepiolite formation by
groundwater movement (Singer, 1984). Bachman and Machette
(1977) found that sepiolite typically occurred in late-stage
calcretes from New Mexico and rarely was found in soils
younger than approximately 100,000 yr BP. Additionally they
found that sepiolite occurred where palygorskite was dominant
and smectite was relatively depleted. The relatively high
smectite content in the Bk2 horizon, however, is not
consistent with their observations.
Neoformation of hormites. Formation of sepiolite has
76
been reported from the Tecopa Basin approximately 32 km east
of Death Valley (Starkey and Blackmon, 1979) and the next
basin to the east, the Amargosa basin (Papke, 1972).
Pleistocene volcanic ash and tuff deposits in the basins were
considered as sources of the soluble silica and magnesia
necessary for sepiolite formation. The proximity of these
basins to the study area suggests that similar volcanics were
deposited in the Death Valley playa with subsequent formation
of hormites. Hormites in soils in the study area may be a
result of formation in the basin, transportation from the
basins to the soils by aeolian processes, and subsequent
alteration.
Pedogenic neoformation of hormites also required sources
of soluble silica, magnesia and, for palygorskite, alumina.
Dissolution of aeolian palygorskite and possibly other clays
from upper horizons and precipitation in lower horizons,
where conditions are favorable for formation and
preservation, is one possible mechanism of authigenic
formation from soil solutions.
There is another mechanism that may be responsible for
the needed soluble silica, alumina, and magnesia in the
soils. High soluble salt contents in all but the Holocene
pedon are indicated by EC values, common efflorescences of
salts on pavement surfaces, and the increasingly fractured
nature of clasts, both in older pavements and older soil
profiles, were observed in the field. Increased clast
fracturing with age has been noted by Yaalon (1970).
Considerable work in recent years has been done on
simulation of daily wetting and drying cycles with saline
solutions (typically sodium sulfate) and their effects on
certain lithologies, most commonly quartz (Goudie, et al.,
1979; Smith, et al., 1987; Magee, et al., 1988). These
77
simulations were done to explain the occurrence of silt-sized
quartz and the effects of salt weathering in desert regions.
Although most workers were concerned with generation of silt
sized quartz from sand particles, it was reported that there
was formation of clay-sized quartz particles as well (Pye and
Sperling, 1983) . It has also been reported that feldspar and
mica were much more susceptible than quartz to salt
weathering and that regolith containing quartz and feldspar
underwent considerably more weathering than quartz dune sand
(Pye and Sperling, 1983) .
The presence of high salt concentrations, and the
tendency of the upper horizons to experience more wetting
episodes, suggest that silica and alumina may be generated in
upper soils horizons from the feldspar- and quartz-rich
parent materials. Salt weathering may also be a factor in
the initial breakdown of rinds in older soils allowing for
partial dissolution and removal of palygorskite from rinds.
Halitim, et al. (1983) reported evidence of dissolution of
aeolian quartz particles caused by salts in Algeria. They
concluded that quartz dissolution by salts was a source of
silica for palygorskite neoformation. Additional SEM
analyses of quartz and feldspar particles would be required
to substantiate the effects of salts on primary mineral
weathering, thereby serving as a silica source for
palygorksite formation in the soils studied. However, salt
dissolution presents another possible means of generating the
components necessary for hermite formation and suggests that
there are multiple factors affecting hermite formation.
Smectite. Smectite distribution in the Holocene profile
(4,400 yr BP) was relatively unchanged throughout, suggesting
that it is detrital. As soil age increased, smectite
distribution changed. In the Q3a-lower pedon (15,400 yr BP),
smectite decreased to minor amounts in upper horizons and
remains relatively unchanged in lower horizons. In the Q3a
upper pedon (50,000 yr BP), smectite in upper horizons
78
increased slightly and is interpreted as being of authigenic
origin. Previous researchers (Bigham, et al., 1980; Lee, et
al., 1983) indicated that palygorskite can alter to smectite.
The distribution of authigenic smectite in upper horizons
suggests that alteration occurred between approximately
15,400 and 50,000 yr BP. Smectite in upper horizons of the
Q2bl-1 and Q2a pedons is also interpreted as being of
authigenic origin, reflecting complete alteration of
palygorskite. The original aeolian palygorksite may have
been deposited prior to 50,000 yr BP.
The amount of smectite in the Bk2 horizon of pedon Q2bl-
1 was relatively high and contradictory to observations of
sepiolite occurrence (Bachman and Machette, 1977) . The
presence of considerable amounts of smectite, very little
palygorskite, and moderate amounts of sepiolite is difficult
to explain. Smectite was probably not detrital since there
was considerably less in the underlying C horizon. Smectite
in the Bk2 horizon may have been relict and indicative of
prevailing soil conditions prior to formation of the
petrocalcic horizon.
Paleoclimatic and Geomorphic Interpretations
Palygorskite and sepiolite in soils are indicative of
arid and semiarid climatic conditions (Callen, 1984). Their
distribution in soils on Hanaupah Canyon Fan appears to be in
agreement with arid-semiarid cycles defined by stable isotope
and microchemical analyses of rock varnish from associated
desert pavements (Dorn, et al., 1987; Dorn, 1988), paleolake,
and paleovegetation records in Death Valley (Hooke, 1972;
Wells and Woodcock, 1985).
The presence of minor amounts of palygorskite in upper
horizons of the Q3a-lower (approximately 15,400 yr BP) is
problematical since its age corresponds with the end of the
last pluvial approximately 10,000 yr BP (Dorn, 1988; Wells
and Woodcock, 1985). The late Pleistocene high stand of Lake
79
Manly was approximately 15 m and deflation of playa sediments
at a minimum. This suggests that aeolian accumulation of
palygorskite in this pedon occurred during the arid phase
(Q3b) following dessication of Lake Manly approximately
10,000 yr BP.
The absence of palygorskite in the Holocene pedon did
not agree with this scenario. The location of Holocene
pedons in topographically low areas on Hanaupah Canyon Fan
and the presence of a bouldery bar and channel surface
suggests that there was concentration of runoff from older,
higher desert pavements, less runoff on the unit itself, and
deeper leaching of soluble materials as a result. Under such
conditions, palygorskite was unstable and any aeolian
accumulations would probably not have been preserved.
The presence of authigenic smectite in upper horizons of
pedons 50,000 yr BP and older was perhaps due to alteration
of aeolian palygorskite. The original palygorskite may have
been Holocene-age and the subsequent alteration due to
conditions less favorable for preservation on the more
dissected, more deeply incised, older fan units.
Alternatively, smectite may represent alteration of older,
Pleistocene-age aeolian palygorskite. The presence of Lake
Manly from prior to 26,000 to approximately 10,000 yr BP
(Hooke, 1972; Wells and Woodcock, 1985; Dorn, 1988) suggest
that there was little deflation of aeolian material at the
time, and probably no hermite formation. Thus, palygorskite
and authigenic smectite in upper horizons of pedons about
50,000 yr BP may represent an older accumulation of aeolian
material. Similar palygorksite and smectite contents in
upper horizons of the Q2b-lower and Q2a pedons may also
represent alteration of older aeolian accumulations.
Methods
CHAPTER IV
MICROMORPHOLOGY
Oriented soil samples for thin section analyses were
collected from six pedons, impregnated with epoxy resin,
mounted on glass slides, and cut parallel to the soil
surface. Thin sections were ground to a uniform thickness of
30 urn and studied in polarized and plane light using a
polarizing microscope at magnifications ranging from 2X to
400X. Descriptions were made according to the terminology of
Brewer (1964). The majority of the samples were taken from
upper horizons since natural aggregates were present. Lower
(Bk) horizons were not well represented due to their loose,
unaggregated nature. In general, the Bk horizons of the
older pedons (>50,000 yr BP) exhibited better aggregation and
were sampled.
Results
Micromorphological properties are presented in Table 9.
Unless noted otherwise, descriptions are for thin sections
cut parallel to the soil surface.
Q3b2, Pedon 1 (4,400 yr BP)
AY. The uncommon argillans were associated with void
surfaces and had rather diffuse boundaries. One narrow band
consisted of a concentration of clay, forming a vo-insepic
fabric of moderately oriented, thicker, discontinuous
argillans. Channel argillans were common in this band and
connected voids (chambers) . A very prominent feature of this
horizon was the high density of very angular, silt-sized
quartz and feldspar lithorelicts. No pedogenic carbonate was
recognized.
80
Tab
le
9.
Mic
rom
orp
ho
log
ical
pro
pert
ies.
ho
rizo
n
dep
th
(em
)
Q3
b2
, p
ed
on
1
Av
0-2
Q3
a-l
ow
er,
p
ed
on
3
Av
(h)
0-9
A
v (v
) 0
-9
Btk
y
9-4
5
Q3
a-m
idd
le,
ped
on
3
Avz
0
-4
Bw
kz
4-1
8
Q3
a-u
pp
er,
p
ed
on
1
Av
0-6
B
tk
6-1
9
Bk1
1
9-4
6
Bk2
4
6-1
65
Q2
b-l
ow
er,
p
ed
on
1
Av
0-5
Btk
5
-17
fab
ric
in-v
osep
ic
vo
-in
sep
ic
sk
el-
vo
-in
sep
ic,
cry
sti
c
sk
el-
vo
sep
ic
sk
el-
in-v
osep
ic,
cry
sti
c
sk
el-
vo
-in
sep
ic
in-v
osep
ic
sk
el-
vo
-in
sep
ic
cry
sti
c
cry
sti
c
cry
sti
c,
in-v
osep
ic
vo
-sk
el-
insep
ic
rela
ted
d
istr
ibu
tio
n
patt
ern
en
au
lic,
ch
i to
nic
en
au
lic
en
au
lic,
po
rph
yri
c
en
au
lic
en
au
lic,
po
rph
yri
c
en
au
lic
en
au
lic
en
au
lic
po
rph
yri
c
po
rph
yri
c
po
rph
yri
c
en
au
lic
arg
illa
ns
ori
en
tati
on
th
ick
ness
wea
k,
co
nti
nu
ou
s th
in
mo
dera
te,
co
nti
nu
ou
s th
ick
m
od
era
te
thin
co
nti
nu
ou
s to
d
isco
nti
nu
ou
s
mo
dera
te,
co
nti
nu
ou
s th
ick
mo
dera
te,
dis
co
nti
nu
ou
s
thin
mo
dera
te,
frag
men
ted
, v
ari
ab
le
dis
co
nti
nu
ou
s
wea
k,
co
nti
nu
ou
s th
in
mo
dera
te,
co
nti
nu
ou
s th
ick
--
----
----
----
--
mo
dera
te,
thin
d
isco
nti
nu
ou
s,
frag
men
ted
m
od
era
te,
co
nti
nu
ou
s v
ari
ab
le
00
.....
..
Tab
le
9 (c
oo
t' d
) .
ho
rizo
n
dep
th
(em
)
Q2
a,
ped
on
1
Av
0-2
AB
2-7
Bty
7
-18
Bky
2 5
2-6
8+
fab
ric
vo
-in
sep
ic,
cry
sti
c
vo
-in
sep
ic,
cry
sti
c
vo
-in
sep
ic,
cry
sti
c
cry
sti
c
rela
ted
d
istr
ibu
tio
n
patt
ern
en
au
lic,
po
rph
yri
c
en
au
lic,
po
rph
yri
c
en
au
lic,
po
rph
yri
c
po
rph
yri
c
ar~illans
ori
en
tati
on
th
ick
ness
wea
k to
m
od
era
te,
thin
· d
isco
nti
nu
ou
s
frag
men
ted
w
eak
to
m
od
era
te,
vari
ab
le
dis
co
nti
nu
ou
s,
frag
men
ted
m
od
era
te,
vari
ab
le
dis
co
nti
nu
ou
s,
----
----
(X)
tv
83 Q3a-lower Peden 2 (15,400 yr BP)
The upper two horizons (Av and Bky) were sampled from
this pedon. Two thin sections were prepared from the Av
horizon; the first was oriented paralled to the soil surface
and the second oriented vertically. The Bky was also
oriented parallel to the surface.
Ay (horizontal) . Argillans were associated with void
surfaces as continuous, smooth coatings. Boundaries with the
s-matrix ranged from diffuse to relatively sharp. Argillan
remnants occurred in the s-matrix in minor amounts and
typically had redder colors (ferriargillans) .
Ay (yertical) . Distinct accumulations of CaC03 were
present, forming a porphyric, crystic fabric. An isolated
pedogenic carbonate rind occurred in the middle of the thin
section. Below it (down) argillans occurred as relatively
thick, red, curved fragments with rather sharp boundaries and
a chaotic arrangement. Voids were also better developed.
Above (up), void argillans were thin, light brown, and formed
continuous coatings with rather diffuse boundaries. The
lower part of the thin section had argillan development
similar to the Btky horizon while the upper part was similar
to the horizontally oriented Av thin section. The rind in
the middle of the slide was located near the boundary between
the Av and Btky horizons.
Pedogenic CaC03 occurred primarily as coatings (calcans)
on clasts, and occasionally with CaC03 in fractures. There
were good examples of displacement of fragments as indicated
by optically continuous particles separated by carbonate.
Minor amounts of cigar-shaped, cloudy, euhedral crystals of
calcite occurred in the s-matrix. In places, these crystals
were present at void edges and appeared to displace and
possibly engulf void argillans.
Btky. Grain argillans were generally ubiquitous, light
red (ferriargillans) to light brown in plane light, with
rather sharp boundaries (Figure 18) . Several thick clay
Fig. 18. Photomicrograph of the Btky horizon of pedon 1 on the Q3a-lower unit showing the skel-vosepic fabric (24X) .
84
85 bridges between particles were observed. Void argillans were
common and had similar characteristics. Channel argillans
were common, partially to completely filling fractures. A
thick CaC03 rind on one of the larger clasts was partially
dissolved and filled by moderately oriented clay in
dissolution channels and voids (Figure 19).
Pedogenic carbonate occurred primarily as micritic rinds
on larger particles. Replacement of quartz particles by
CaC03 was common as indicated by varying degrees of embayment
at particle edges.
Q3a-middle Pedon 3 (32,000 yr BP)
~. Argillans were dominantly associated with voids,
with very few skeletans. Void argillans were mostly light
brown to red (ferriargillans) in plane light, with rather
sharp boundaries.
Calcium carbonate occurred as micrite, clear microspar,
and cigar-shaped, cloudy, euhedral crystals. The cloudy
calcite was dominant, restricted to the s-matrix, and did not
occur in voids. It commonly dominated the matrix, resulting
in a porphyric, crystic fabric. It was present at void
edges, commonly adjacent to void argillans. In places, it
appeared to be displacing and possibly replacing the
argillans. Micrite and clear microspar, to varying degrees,
partially filled voids, where euhedral crystals in the matrix
formed the void wall. Micrite was present on the outer part
of the void and clear spar towards the center. Displacement
and embayment of quartz and feldspar lithorelicts by
carbonate were common.
Bwkz. Void argillans were relatively common with rather
sharp boundaries, and typically brownish red (ferriargillan)
in color. Grain argillans were relatively rare. Thin and
moderately thick void argillans were present in approximately
equal amounts. The overall appearance of argillans was
fragmented, commonly with abrupt edges.
Fig. 19. Photomicrograph of the Btky horizon of pedon 1 on the Q3a-lower unit showing clay accumulation within voids of a rind of calcium carbonate (SOX) .
86
87
Calcium carbonate occurred as micrite, clear microspar,
cigar-shaped, cloudy, euhedral crystals, and cloudy columnar
spar. Micrite and clear microspar were restricted to
pedogenic rinds on clasts. The cigar shaped crystals were
common and restricted to the matrix, but were less abundant
than in the overlying Avz horizon. They rarely extended into
voids and commonly formed part of the void wall, next to
argillans. In places, they appeared to be displacing and
possibly engulfing argillans. Columnar, cloudy spar was
restricted to edges of clasts, where it formed calcans with
crystal boundaries oriented perpendicular to clast surfaces.
Columnar spar and euhedral crystals were approximately the
same size. Embayment of quartz and feldspar by CaC03 was
common.
Q3a-upper Pedon 1 (50,000 yr BP)
~- Void argillans were dominantly thin with diffuse
boundaries (Figure 20) . A few compound argillan-calcans were
observed on skeletal quartz particles, with argillans forming
the outermost coat. ELk. Argillans were common on skeletal grains with less
common void and channel argillans. Argillans were typically
red (ferriargillans) and thick, with rather sharp boundaries.
Compound argillan-calcans were common and similar to those
observed in the Av horizon.
Calcium carbonate occurred as micrite, clear microspar,
and cloudy, cigar-shaped eudedral crystals. Micrite
typically occurred as rinds on clasts and as ring-like
concentrations in the matrix. Clear microspar partially
filled voids in the matrix. The cloudy euhedral crystals
occurred infrequently in parts of the matrix. Replacement
and displacement of quartz and feldspar by calcite were
common. Bkl and Bk2. No argillans were observed. Carbonate
distribution in both horizons was similar and characterized
Fig. 20. Photomicrograph of the Av horizon o pedon 1 on the Q3a-upper unit showing the in-vosepic fabric (24X) .
88
89 by micrite and clear microspar. In the Bk1 horizon, the
matrix was composed primarily of microspar (approximately 50-
75%). In the Bk2 horizon microspar comprised considerably
more of the matrix (75-90%) . Micrite occurred as pedogenic
rinds on larger clasts and as roughly circular concentrations
in the matrix. Clear microspar was the major component of
the matrix and was observed in fractures in lithorelicts,
where it appeared to be displacing fragments into the soil
matrix. Pedogenic microquartz was present in the Bk2 horizon
as a compound calcan-silan on a clast, with the silan forming
the inner rind. In places, parts of the silan appeared as
isolated areas within the calcan.
Q2b-lower Peden 1 (120,000 yr BP)
~. The matrix consisted primarily of cloudy, cigar
shaped calcite, resulting in a crystic fabric. A few
rosettes of these crystals were observed (Figure 21) . Void
argillans were rare, with diffuse boundaries, and
discontinuous due to apparent dissruption by the cloudy,
euhedral calcite. Fragmented void arigillans were surrounded
by the calcite at void edges and appeared to be engulfed and
displaced.
Calcite also occurred as micrite, clear microspar, and
cloudy, columnar spar (Figure 22). Micrite commonly occurred
as calcans on clasts, while microspar typically occurred in
voids developed in the micritic calcans. The cloudy,
euhedral calcite was restricted to the soil matrix and rarely
extended into voids. Cloudy, columnar spar occurred as
calcans around clasts with crystal boundaries oriented
perpendicular to the clast surface.
~. Both void and skeletal grain argillans, ranging
from thin to thick, were continuous with diffuse boundaries.
A few clay bridges were observed between grains. Carbonate
was present as micritic rinds with clear microspar commonly
occurring in voids within the rinds.
Fig. 21. Photomicrograph of the Av horizon of pedon 1 on the Q2b-lower unit showing a rosette of cloudy calcite crystals ( 4 OX) •
90
Fig. 22. Photomicrograph of the Av horizon of pedon 1 on the Q2b-lower unit showing cloudy calcite crystals at void edges and microspar partially filling voids ( 2 4 X) •
91
92 Q2a Pedon 1 (145,000 yr BP)
~- Void argillans ranged from thin to thick and had
diffuse boundaries. Blocky fragments of moderately oriented
argillans were observed in the matrix. Void argillans were
commonly discontinuous due to the presence of cloudy euhedral
calcite in the matrix at the void edges. Parts of the matrix
were dominated by cloudy calcite crystals and formed a
porphyric, crystic fabric.
Calcium carbonate occurred as micrite, clear microspar,
and cloudy euhedral crystals. Micrite and clear microspar
were associated with pedogenic calcans (rinds) . Cloudy
euhedral crystals were restricted to the soil matrix and
occurred as individual crystals and rosettes. Clear
microspar was common in voids where cloudy calcite formed
void edges.
Aa. Voids and areas of cloudy calite in the matrix were
less common than in the Av horizon. Argillan development was
similar to that in the Av horizon.
Calcite occurred as micritic rinds on clasts, clear
microspar growing in voids in the rinds, and cloudy crystals
in the s-matrix. Micrite and clear spar also occurred in the
matrix, the latter in voids. Cloudy crystals were present as
discrete clusters in the matrix, forming a porphyric, crystic
fabric. ~- Argillans had diffuse to moderately diffuse
boundaries, and were commonly red (ferriargillans) . Some
argillans were observed bridging grains. A few void
ferriargillans were present and appeared fragmented, with
abrupt, sharp edges. Channel ferriargillans were common.
Carbonate rinds were rare and very porous. Cloudy
euhedral calcite was infrequent and restricted to the matrix,
forming a porphyric, crystic fabric. Replacement of quartz
particles by carbonate was common. Bky2. Micritic calcite occurred as rinds on clasts and
small circular concentrations in the matrix. Clear microspar
formed the majority of the matrix and was a minor component
of rinds. Replacement of quartz by calcite was common.
Unidentified Authigenic Mineral
93
In each horizon studied in thin section, there were
observed acicular crystals that commonly occurred as fibrous
clumps and masses. These occurred predominantly in
association with polycrystalline lithorelicts, located at
crystal boundaries (Figure 23) . This mineral was very rarely
associated with monocrystalline lithorelicts.
It was present in very minor amounts in the Q3b2 Av
horizon, increasing to minor amounts in horizons of the Q3a
lower and -middle pedons. In the Q3a-upper pedon, amounts
increased from minor in upper horizons (Av and Btk) to
moderate in the Bkl horizon. The Bk2 had minor amounts. The
increase in the Bkl reflected the presence of the mineral in
the soil matrix in addition to its occurrence at
polycrystalline grain boundaries. Very minor amounts were
observed in the Av horizons of the Q2b-lower and Q2a pedons.
Subjacent horizons had minor amounts.
The second order birefringence colors observed for this
mineral fall within the range for calcite and palygorskite.
Preliminary staining with alizarin red and tests with
hydrochloric acid were negative for calcite. The
distribution of this mineral in the horizons of which thin
sections were made seemed to parallel the palygorskite
distribution observed in XRD of clay and silt (preliminary)
fractions, especially in the Q3a-upper pedon. Identification
as palygorskite is tentative until additional microchemical
tests are made.
Discussion
Clay Orientation and Accumulation
Clay orientation was observed in every pedon to varying
degrees. Argillans in the Av horizon of the Q3b2 (Holocene)
Fig. 23. Photomicrograph of the Av horizon of pedon 1 on the Q3a-upper unit showing palygorskite (?) within a polycrystalline quartz lithorelict (80X) .
94
were typically associated with smooth-walled voids, or vesicles. The f t' f orma 10n o vesicles is probably the result
of heating and expansion of air trapped in the soil after
summer rainfall (Evanari, et al., 1974). Vesicles are
usually restricted to horizons with silty textural classes.
The occurrence of argillans at the walls of vesicles is
probably the result of the pressure exerted by the entrapped
air, and not of clay illuviation. Vesicle argillans were
common in surface (Av) horizons of all pedons analyzed and
less common in the subjacent horizon. Orientation was
observed to be better in older pedons. The presence of
vesicle argillans in all pedons and better orientation in
older pedons suggests that the processes forming them have
been active for at least the past approximately 145,000 yr
BP.
95
Clay orientation was better developed in most pedons
older than the Q3b2 (4,400 yr BP). The greatest abundance of
argillans was seen in the Q3a-lower pedon (15,400 yr BP).
The ubiquitous nature of argillans in the Btky horizon of the
Q3a-lower pedon, and their presence in fractures and voids of
pedogenic CaC03, are indicative of clay accumulation
(illuviation) .
Argillans in the Q3a-middle (32,000 yr BP) and older
pedons showed evidence of degradation in varying degrees.
Argillans in the older pedons (Q2a and Q2b-lower) generally
were more fragmented and discontinuous, indicating greater
degradation. To a large extent, destruction of argillans,
especially void argillans, was due to the growth of the
cloudy, cigar-shaped, euhedral calcite in the soil matrix,
commonly displacing and engulfing argillans. The degraded
appearance of argillans and the abundance of the calcite in
the s-matrix suggests that destruction of argillans was
present by at least 32,000 yr BP and probably continued until
upper horizons were removed between approximately 145,000 and
800,000 yr BP.
Calcium Carbonate
Pedogenic CaC03 was not observed in the Q3b2 pedon,
probably due to the young age of the deposits (4,400 yr BP).
In pedons approximately 15,400 yr BP and older, CaC03 was
96
observed in all horizons in several forms. Carbonate was
observed in the s-matrix and as rinds (cutans) on clasts. In
general, most micrite and clear microspar formed rinds on
clasts and were rare in the matrix in upper horizons. Where
sampled, microspar in Bk horizons of pedons approximately
50,000 yr BP and older formed the soil matrix. The presence
of micritic rinds in Av horizons were interpreted as
pedorelicts, probably representing degradation of underlying
horizons.
Detrital quartz and feldspar particles in all pedons,
including the Holocene, were observed to have undergone
varying degrees of displacement, dissolution, and replacement
by carbonate, most commonly by microspar. Carbonate commonly
occurred in fractures at the edges of lithorelics. Growth of
carbonate in these fractures resulted in displacement of
lithorelict fragments into the s-matrix.
Cloudy, cigar-shaped, and columnar calcite was observed
in pedons > 15,400 yr BP and were restricted to upper
horizons, especially Av horizons. Cigar-shaped crystals in
these analyses were similar to the "acutely terminated
calcite crystals" described by Hunt, et al., (1966) from the
silty sands in the carbonate zone of the Death Valley playa
deposits. They attributed the occurrence of the calcite and
overlying zones of more soluble salts to capillary rise of
groundwater. The restriction of cloudy crystals in soils to
upper horizons, suggests that their occurrence is due to
similar processes. Saturation of soils in Death Valley under
current conditions is infrequent, and subsequent evaporation
is very high and probably results in capillary movement of
water to the soil surface. Common efflorescences of soluble
97
salts at the soil surface were also observed during this
study and were attributed to capillary movement and surface
evaporation of soil solutions. The occurrence of soluble
salts at the soil surface and calcite crystals in the surface
horizon (Av) mimics the zonation within the playa deposits.
The restriction of the cloudy calcite crystals to the
soil matrix is not clearly understood. With a few rare
exceptions, the crystals did not extend into pre-existing
voids. The presence of discontinuous clay cutans next to,
and in places within or surrounded by, the crystals at void
edges suggests that argillans were incorporated and displaced
as the crystals grew. The argillans may have coated the
calcite crystals at void surfaces and, thus, inhibited growth
into voids. In the Bwkz horizon of the Q3a-middle unit, the
presence of micrite and microspar within voids surrounded by
the cloudy calcite indicates precipitation of carbonate from
younger soil solutions. The presence of significant amounts
of the cloudy calcite in the older Av horizons (120,000 and
145,000 yr BP) suggests that capillary movement may have been
active over considerable periods of time. Alternatively, it
may be related to the presence of a less permeable
petrocalcic horizon and slower drainage in older pedons.
Under these conditions, there may be more capillary movement
of water and more concentration of carbonate in surface
horizons. Thus, the cloudy calcite may be of similar age to
that seen in younger pedons. The relationship between
formation of this type of calcite and soil age is not
resolved.
Cloudy, columnar sparry calcite was also observed in
upper horizons as rinds (calcans) on lithorelicts. These
were similarly interpreted as the result of precipitation
from capillary soil solutions due to evaporation at the soil
surface. Precipitation on clast surfaces probably restricted
crystal growth resulting in columnar morphology observed.
98
Paleoclimatic Interpretations
The transition from semi-arid to arid conditions at the
end of the Pleistocene approximately 10,000 yr BP is well
documented in the Death Valley area (Wells and Woodcock,
1985; Dorn, 1988). The Q3a-lower pedon (approximately 15,400
yr BP) contained considerable amounts of illuvial clay in the
Bky horizon with no signs of argillan degradation and
probably represents illuviation under more humid, semi-arid
conditions at the end of the Pleistocene. Climatic
interpretations of the relationship between argillans and
calcans in pedons older than about 15,400 yr BP are tenuous
at best due to the effects of the growth of calcite crystals
in the soil matrix. Timing of this growth is crucial to
unraveling any climatic signals preserved in upper soil
horizons and requires analyses, in particular stable
isotopes, beyond the scope of this study.
Soil Development Indices
CHAPTER V
CONCLUSIONS
Soil development on Hanaupah Canyon Fan in Death Valley,
California, has been evaluated using soil development indices.
Individual property development indicated that significant
amounts of aeolian material had been added to the soil
surface. Aeolian dust strongly influenced soil development,
especially in young soils where bouldery and cobbly surfaces
acted as efficient dust traps. The formation of desert
pavements and subsequent gulley development resulted in less
dust accumulation due to increased erosion. Destruction of
pavement by the expanding gulley network has been accompanied
by a decrease in upper horizon thickness as the rate of
aeolian accumulation lagged behind the effects of erosion.
Eventually, the overlying soil was completely removed and the
underlying petrocalcic horizon gradually exposed between
approximately 120,000 and 800,000 yr BP.
The development of dry consistence, structure, and clay
films was restricted to upper horizons, defined as those
horizons reflecting addition of aeolian materials as
indicated by better development of these three properties.
Rubification was also restricted to upper horizons, but
showed no systematic development from youngest (4,400 yr BP)
to oldest (145,000 yr BP) profiles. Surface horizons were
vesicular silt loams, but changes in particle size
distribution as a function of depth were not systematic
largely due to the highly variable nature of the alluvial
deposits in which the soils formed. As a result, changes in
texture did not show a systematic relationship with soil age.
Lower horizons were best characterized by properties
associated with the accumulation of calcium carbonate.
Properties used in earlier indices (Harden and Taylor, 1983)
99
100
included color lightening and color paling. Use of these
properties on Hanaupah Canyon Fan was severely limited by the
light, pale colors of the alluvial deposits. Paling did not
occur in Bk horizons. Lightening did not occur until about
50,000 yr BP where Bk and C horizons had slightly higher
values than parent materials in younger soils. Geomorphic
relations suggest that this color change is not due to
differences in parent materials. It is interpreted here as
representing incipient accumulation of CaC03. Stage of
carbonate formation as defined by Gile, et al. (1966) was
added into the index to better characterize lower horizon
development and showed the best correlation with soil age of
all properties quantified.
Development of upper horizon properties indicated that
the effect of aeolian additions decreased with age as erosion
increased. The thickness of upper horizons reached a maximum
(approximately 40 em) on the youngest surface with a desert
pavement (about 15,000 yr BP), decreased to less than 20 em
by about 32,000 yr BP then decreased more slowly over the
next 100,000 years. Eventually, erosion removed upper
horizons completely and exposed an underlying petrocalcic
horizon sometime prior to about 800,000 yr BP. Maximum
development of structure was reached by about 15,400 yr BP,
whereas clay film development was first seen in pedons that
were on surfaces dated at approximately 32,000 yr BP. This
represents visible accumulation of clay and ,therefore, a
maximum age for the onset of clay translocation. Dry
consistence was the only upper soil property to change
systematically for more than about 50,000 years. Dry
consistence reached a maximum at 120,000 yr BP then decreased
in the next older soil (about 145,000 yr BP). Changes in dry
consistence, however, were very slow and did not correlate
well with soil age.
Development of lower horizon properties indicated
redistribution of CaC03 from upper to lower horizons. Maxima
101
were reached more slowly than in upper horizons. Maximum
lightening of color occurred by about 50,000 yr BP whereas
stage III CaC03 accumulation developed between approximately
50,000 and 120,000 yr BP. Stage IV, if present, may have
developed and subsequently eroded between about 145,000 and
800,000 yr BP. Upper Bk horizons, characterized by loose
rinds, overlie rubbly eroded petrocalcic horizons in older
soils. The overall thickness of pedogenic carbonate
accumulation increased, indicating movement of carbonate to
greater depths. The sources of carbonate included aeolian
sediments and dissolution of rinds in upper horizons of older
pedons. It may also be due, in part, to dissolution of
detritus in the parent material.
Calcium carbonate equivalence (CCE) values on the < 2mm
fraction indicated that additions of aeolian carbonate
reached a maximum by about 50,000 yr BP but decreased
considerably in older soils due to increased erosion of upper
horizons. The distribution seen may also have been due to
capillary concentration of carbonate in upper horizons.
Values in older soils indicated that there was translocation
of CaC03 from upper to lower horizons in response to
increased erosion.
Soluble salt content (EC) was relatively high on soils
with associated desert pavements, but did not change
systematically with increasing age. Holocene soils had
relatively low values that were best explained by topographic
position and surface morphology. Reaction values (pH)
indicated that they were suppressed by high salt content in
some horizons. Values of pH for C horizons primarily
reflected the presence of relatively high amounts of CaC03
and were non-systematic with increasing age. As a result, pH
could not be used in indices calculations.
Horizon indices reflected maximum horizon development in
upper soil zones. Maxima moved into Btk horizons by
approximately 15,400 yr BP but were never deeper than about
102
20 em and moved toward the surface in all older pedons.
Lower horizons had low indices representing only carbonate
accumulation. The lowest index in each profile occurred in
the C horizon. In profiles older than about 50,000 yr BP, C
horizons had values slightly higher than zero due to
lightening of color.
Profile indices were calculated using (1) all seven
properties described and (2) the four properties that had the
best correlation with soil age (dry consistence, structure,
lightening, and stage of carbonate formation). The index
utilizing the best four properties had a better correlation
with soil age. Use of the profile index for correlation of
geomorphic surfaces was not practical. Of all properties and
measurements, total solum and lower horizon thicknesses
provided the most reliable means of correlation of geomorphic
surfaces on Hanaupah Canyon Fan.
In the chronosequence studied, field properties and lab
analyses indicated that time, surface morphology, and
topographic position of soils most strongly influenced soil
development. Effects of paleoclimatic change were not
evident from the properties described. Incorporation of
aeolian materials and probable capillary movement were the
dominant processes affecting upper horizon development.
These were important in younger soils, but became less
important in older soils as increased dissection and erosion
removed upper horizons. No indications of past climatic
changes in upper horizon development could be detected in the
present study. Lower horizons were dominated by accumulation
of CaC03 throughout soil development on Hanaupah Canyon Fan.
No soil properties described exhibited indications of
paleoclimatic conditions, although accumulation of calcium
carbonate may have preserved stable isotope values reflecting
such changes.
103
Clay Mineralogy
Holocene soils and C horizons of all pedons were
characterized by detrital assemblages of predominantly mica
with moderate amounts of chlorite, smectite, and minor
amounts of talc. In soils on surfaces approximately 15,400
yr BP and older, palygorskite was present in all but the C
horizon and its first occurrence in time corresponded to the
youngest desert pavement. The highest amounts of
palygorskite were located in the uppermost Bk horizon of each
pedon. The presence of minor amounts of palygorksite in
upper horizons, where soil conditions were not conducive for
formation and preservation of palygorskite, were suggestive
of an aeolian source. Palygorskite probably formed in the
associated playa and other basins in the region and was
subsequently transported by wind to fan surfaces. By
approximately 50,000 yr BP, authigenic smectite appeared in
upper horizons and may represent alteration of palygorskite.
Probable sources of palygorskite include alteration and
translocation of aeolian material from upper to lower
horizons, removal of palygorskite from eroded pedogenic rinds
in less alkaline upper horizons, and neoformation.
Neoformation was indicated by sepiolite in one pedon and
palygorskite in carbonate rinds from younger soils.
Neoformation of hormites required sources of soluble
magnesium, silica and, for palygorskite, alumina.
Dissolution of aeolian palygorskite and other clay minerals
was one possible source. The presence of very high soluble
salt content in all but the Holocene pedon suggested that
salt weathering of detrital and possibly aeolian materials
generated the necessary constituents.
The distribution of palygorskite in upper horizons of
pedons younger than approximately 50,000 yr BP perhaps
represents Holocene-age aeolian deposition on fan units.
Older pedons did not preserve Holocene-age palygorkite
accumulation due to the presence of better developed drainage
104
systems. Alteration of palygorskite to smectite was
suggested by assemblages in upper horizons of pedons > 50,000
yr BP. This may represent palygorskite accumulations older
than the Holocene or the preservational effects of the better
drainages developed on older units.
Thin Section Analyses
Influxes of aeolian materials were indicated by the
angular, silt-sized, predominantly quartz particles. The
generation of similar material by displacive growth of
calcite in lithorelicts fractures was commonly observed.
Void argillans were present in all pedons and indicated
orientation of clay due to pressure exerted by gas trapped in
vesicles in upper horizons. Orientation generally became
better as soil age increased, suggesting that they have
formed over at least the past approximately 145,000 years.
Degradation of argillans also increased with age, primarily
as the result of the growth of cloudy, cigar-shaped, euhedral
calcite crystals in the soil matrix. These crystals probably
formed as a result of capillary rise of soil water into upper
horizons, followed by subsequent evaporation and
precipitation. Although the density of crystals generally
increased with soil age, it was not possible to determine if
they formed at approximately the same time or over longer
periods.
Palygorskite was tentatively identified in varying
amounts from all horizons, most commonly at crystal
boundaries of quartz-rich, polycrystalline lithorelics. Its
occurrence may yield insight into the paleoclimatic history
the area once additional analyses are conducted.
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109
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APPENDIX A
FIELD DESCRIPTIONS
110
Tab
le
10
. F
ield
descri
pti
on
s
ho
riz
on
Ped
on
Q
2a
Av
AB
B
ty
Bky
1 B
ky2
Bkr
n
dep
th
(em
)
0-2
2
-7
7-1
8
18
-52
5
2-6
8+
6
8-2
83
Ped
on
Q
2b
l-1
A
v 0
-5
Btk
5
-17
B
k1
17
-39
B
krn
39
-24
0
Bk2
2
40
-25
3
c 25
3+
Ped
on
Q
2b
l-2
A
v 0
-5
Btk
5
-17
B
k 1
7-2
5
Bkr
n1
25
-55
B
krn2
5
5-2
69
c
26
9-5
00
+
Mu
nse
ll
tex
ture
co
lor
(mo
ist)
10Y
R
4/3
--
-10
YR
4
/4
---
10Y
R
4/6
--
-2
.5Y
5
/4
---
" --
-"
---
10Y
R
4/4
--
-10
YR
4
/3
---
2.5
Y
4/4
--
-"
---
" --
-"
---
10Y
R
4/4
--
-"
---
" --
-2.
SY
5
/4
---
" --
-"
---
str
uctu
re
wk
pty
w
k p
ty/s
bk
sg
sg
sg
rn
wk
pty
/sb
k
wk
sbk
sg
rn sg
sg
wk
pty
/sb
k
wk
sbk
sg
rn rn sg
dry
co
nsis
t
en
ce
vh
/h
h h s s h sh
1 1 1 vh
h
/vh
1 1
cla
y
film
s
ftd
ftd
ftd
.......
.......
.......
Ped
en
Q3
au-1
A
v 0
-6
10Y
R
4/4
--
-B
tk
6-1
9
" --
-B
ku
19
-46
2
.5Y
5
/2
---
Bk1
4
6-1
65
"
---
c 1
65
+
2.5
Y
5/4
--
-
Ped
en
Q3
au-2
A
v 0
-3
10Y
R
4/3
--
-B
tkz
3-2
0
10Y
R
4/4
--
-B
ku
20
-48
2
.5Y
5
/4
---
Bk1
4
8-1
66
"
---
c 16
6+
" --
-
Ped
en
Q3
au-3
A
v 0
-4
lOY
R
4/3
--
-B
tkz
4-2
2
10Y
R
4/4
--
-B
ku
22
-49
2
.5Y
5
/4
---
Bk1
4
9-1
74
"
---
c 17
4+
" --
-
Ped
en
Q3a
m-1
A
v 0
-1
10Y
R
4/3
--
-B
wk
1-1
5
" --
-B
k1
15
-47
2
.5Y
4
/4
---
Bk2
4
7-1
87
"
---
c 18
7+
" --
-
wk
pty
/sb
k
wk
sbk
sg
sg
sg
wk
sbk
w
k sb
k
sg
sg
sg
wk
sbk
w
k sb
k
sg
sg
sg
wk
sbk
w
k sb
k
sg
sg
sg
sh
sh s 1 1 h
sh
/s
s/1
1 1 h sh
s/
1 1 l h
sh
l l l
ftd
ftd
ftd
~
~
N
Ped
en
Q
3arn
-2
Av
0-3
10
YR
4
/2
---
wk
sbk
h
Btk
3
-22
10
YR
4
/4
---
wk
sbk
h
ftd
B
ku
22
-40
2
.5Y
4
/4
---
sg
1 B
k1
40
-17
0
" --
-sg
1
c 1
70
+
" --
-sg
1
Ped
en
Q3a
rn-3
A
v 0
-4
10Y
R
4/3
--
-w
k p
ty/s
bk
B
wkz
4
-18
10
YR
4
/4
---
wk
sbk
B
ku
18
-38
2
.5Y
4
/4
---
sg
Bk1
3
8-5
8+
"
---
sg
Ped
en
Q
3a1
-1
Av
0-5
10
YR
4
/3
---
wk
sbk
sh
B
tkz
5-2
4
10Y
R
4/4
--
-w
k sb
k
sh
/s
Bku
2
4-5
0.5
2
.5Y
4
/4
---
sg
1 B
k1
50
.5-1
41
"
---
sg
1 c
14
1+
"
---
sg
1
Ped
en
Q3
a1-2
A
v 0
-5
10Y
R
4/2
--
-w
k sb
k
h/s
h
Bw
k 5
-30
10
YR
4
/4
---
wk
sbk
sh
B
ky
30
-70
2
.5Y
4
/4
---
sg
1 B
k 7
0-1
28
"
---
sg
1 c
12
8+
"
---
sg
1
Ped
en
Q3
al-
3
Av
0-9
lO
YR
4
/3
---
wk
pty
/sb
k
h/s
h
Bky
9
-45
lO
YR
4
/4
---
wk
sbk
s/1
B
kl
45
-72
2
.5Y
4
/4
---
sg
1 B
k2
72
-15
4
" --
-sg
1
---
......
c 1
54
+
" --
-sg
1
......
---
w
Ped
on
Q
3b
2-1
A
v 0
-2
10Y
R
4/4
--
-vw
k sb
k
sh
Bw
2
-30
2
.5Y
4
/4
---
sg
s B
C
30
-74
"
---
sg
1 c
74
+
" --
-sg
1
Ped
on
Q
3b
2-2
A
v 0
-2
10Y
R
4/3
--
-w
k sb
k
s B
wk
1-u
2
-10
"
---
sg
1 B
wk
1-l
1
0-2
9
I --
-sg
1
Bw
k2
29
-45
"
---
sg
1 B
wk3
4
5-6
0+
"
---
sg
1
Ped
on
Q
3b
2-3
A
v 0
-1
10Y
R
4/3
--
-vw
k sb
k
vs
Bw
k1
-u
1-2
0
" --
-sg
1
Bw
k1
-l
20
-40
"
---
sg
1 B
wk2
4
0-6
0+
"
---
sg
1
Ped
on
Q
3b
2-4
A
v 0
-1
10Y
R
4/3
--
-vw
k sb
k
vs
Bw
k1
-u
1-2
5
" --
-sg
1
Bw
k1
-1
25
-46
"
---
sg
1 B
wk2
4
6-6
9+
II
--
-sg
1
Ped
on
Q
3b
2-5
A
v 0
-1
lOY
R
4/4
S
L
v w
k sb
k
s B
w
1-9
2
.5Y
4
/4
LS
sg
1 B
k 9
-48
"
LS
sg
1 B
C
48
-69
"
SL
sg
1
c 6
9-1
80
+
" L
sg
1
I-'
I-'
.b
Ped
on
Q
3b
2-6
A
v 0
-1
10Y
R
4/4
B
w
1-1
7
2.5
Y
4/4
B
k1
17
-54
II
Bk2
5
4-8
2
II
c 8
2-1
50
+
"
1 =
lo
ose
vs
= v
ery
so
ft
s =
so
ft
sh =
sli
gh
tly
h
ard
h
= h
ard
v
h =
very
h
ard
SL
v w
k sb
k
LS
sg
LS
sg
LS
sg
L
sg
vwk
= v
ery
w
eak
w
= w
eak
sb
k =
su
ban
gu
lar
blo
ck
y
pty
=
pla
ty
sg =
sin
gle
g
rain
'
m =
mass
1v
e
s 1 1 1 1
f =
few
t
= t
hin
d
= d
is-
co
nti
nu
ou
s
t--'
t-
-'
Ul
APPENDIX B
CHEMICAL PROPERTIES
116
Tab
le
11
. C
hem
ical
pro
pert
ies
ho
rizo
n
dep
th
CCE
pH
solu
ble
P
art
icle
S
ize D
istr
ibu
tio
n
tex
tura
l (e
m)
(%)
salt
s
% s
an
d
% c
lay
%
sil
t cla
ss
Ped
on
Q
2a
Av
0-2
9
.4
7.9
4
7.5
4
7.0
5
11
.92
4
1.0
3
SiL
A
B
2-7
1
2.3
4
8.2
3
.6
44
.11
1
6.2
3
39
.66
S
iL
Bty
7
-18
11
8
.1
6.7
6
1.0
7
7.
91
31
.02
SL
B
ky1
18
-52
2
1.2
9
8.1
5
6.5
5
9.2
5
2.3
7
38
.38
SL
B
ky2
52
-68
+
20
.4
8 3
9.6
4
7.4
2
7.8
3
44
.75
S
iL
Bkm
6
8-2
83
Ped
on
Q
2b
l-1
A
v 0
-5
7.1
3
7.9
5
5.5
4
2.2
8
14
.63
4
3.0
9
SiL
B
tk
5-1
7
8.7
1
7.9
26
6
8.3
2
6.8
7
24
.81
SL
B
k1
17
-39
1
1.0
3
8.2
5
9.6
6
6.3
9
2.4
3
31
.18
SL
B
km
39
-24
0
Bk2
2
40
-25
3
19
.29
8
.3
113
59
.98
7
.65
3
2.3
7
L
c 2
53
-50
0+
1
3.0
2
8.4
1
1.3
6
1.2
4
5. 6
4 3
3.1
2
SL
Ped
on
Q
2b
l-2
A
v 0
-5
· Btk
5
-17
B
k 1
7-2
5
Bkm
l"
25
-55
B
km2
55
-26
9
c 2
69
-50
0+
?ed
on
Q
3au
-1
Av
0-6
9
.95
8
.2
1 7
2.2
1
7.5
1
20
.28
SL
B
tk
6-1
9
5.9
7
8.1
0
.91
6
3.1
5
8.3
7
28
.48
SL
B
ku
19
-46
1
2.3
9
---
0.8
3
50
.44
7
.34
4
2.2
2
L
.Bkl
4
6-1
65
1
3.5
5
7.9
3
.1
67
.86
4
.42
2
7.7
2
SL
c 16
5+
---
---
---
50
.03
7
.72
4
2.2
5
L
,......
......
.....J
Ped
on
Q
3au
-2
Av
0-3
1
6.0
1
7.5
14
4 B
tkz
3-2
0
5.5
7
7.8
4
.4
Bku
2
0-4
8
11
.47
7
.7
36
Bk
l 4
8-1
66
1
2.5
1
7.6
9
.75
c
166+
1
1.5
2
Ped
on
Q
3au
-3
Av
0-4
1
3.7
4
7.1
1
09
.8
Btk
z 4
-22
8
.95
7
.2
16
5.8
B
ku
22
-49
1
4.3
7
.5
90
Bk
l 4
9-1
74
1
5.9
5
7.5
9
0.9
c
174+
1
1.4
3
8.5
4
.7
Ped
on
Q
3am
-1
Av
0-1
1
3.9
6
7.5
98
B
wk
1-1
5
6.7
7
7.1
27
0 B
k1
15
-47
7
.42
7
.7
10
8.8
B
k2
47
-18
7
10
.87
8
.5
78
C1
187+
1
1.1
5
8.5
2
4.3
Ped
on
Q
3am
-2
Av
0-3
5
.71
8
.1
24
.5
Btk
z 3
-22
8
.17
6
.9
29
7.5
B
ku
22
-40
3
.82
7
.5
16
2.5
B
kl
40
-17
0
5.3
7
7.6
12
6 C2
17
0+
12
.02
8
.5
8
Ped
on
Q
3am
-3
Av
0-4
9
.77
8
.1
23
.4
Bw
kz
4-1
8
---
---
---
Bku
1
8-3
8
Bk
l 3
8-5
8+
8
.02
7
.8
96
.2
34
.2
20
.45
4
9.2
5
15
.25
5
3.8
2
9.3
2
57
.54
4
.78
77
2
.21
41
.09
1
6.5
7
49
.12
4
.84
6
0.5
2
5.4
4
58
.37
7
.55
4
9. 7
2 4
.66
42
.55
1
4.4
6
57
.09
1
0.2
8
65
.01
1
.89
5
8.5
5
8.5
7
33
12
.55
4
3.6
8
8.5
7
58
.16
2
.82
5
8.5
6
5.9
5
61
. 97
6
.03
37
.22
1
2.5
6
47
.89
1
3.2
5
64
.83
5
. 43
45
.35
3
5.5
3
6.8
6
37
.68
2
0.7
9
42
.34
4
6.0
4
34
.04
3
4.0
8
45
.62
42
.99
3
2.6
3
33
.1
32
.88
54
.45
5
2.2
5
39
.02
3
5.4
9
32
50
.22
3
8.8
6
29
.74
SiL
S
iL
L
SL
LS
SiL
S
iL
SL L
SiL
SiL
L
SL L
SiL
S
iL
SL
SL
SL
SiL
S
iL
SL
.....
.....
CD
Ped
on
Q3
al-1
A
v 0
-5
9.2
3
8 20
Bw
k 5
-24
4
.87
7
.6
53
.4
Bku
2
4-5
0.5
3
. 62
8
65
Bkl
5
0.5
-14
1
3.2
9
8.2
70
c
141+
1
3. 9
4 8
.4
5
Ped
on
Q3
al-2
A
v 0
-5
9.8
8
38
Bwk
5-3
0
7.0
9
8.3
1
13
.8
Bky
3
0-7
0
4.5
2
8.6
13
0 B
k 7
0-1
28
7
.15
8
.4
80
.6
c 12
8+
8.4
8
.3
36
Ped
on
Q
3al-
3
Av
0-9
6
.53
8
.2
18
.9
Bky
9
-45
4
.59
8
.1
13
.5
Bk1
4
5-7
2
4.4
5
8 2
1.5
B
k2
72
-15
4
8.4
8
16
.1
c 15
4+
12
.7
2.0
7
Ped
on
Q3
b2
-1
Av
0-2
9
.78
7
.9
0.
92
Bw
-2
-30
9
.72
8
.5
0.4
9
BC
30
-74
9
.47
8
.5
0.8
1
c 74
+
9.0
9
8.1
3
.5
Ped
on
Q3
b2
-2
Av
0-2
8
.6
7.9
1
.6
Bw
k1-u
2
-10
1
0.1
9
8.4
0
.61
B
wk1
-l
10
-29
8
.29
8
.4
0.6
9
Bw
k2
29
-45
8
.53
8
.4
1.
9 B
wk3
4
5-6
0+
8
8.4
6
.5
48
.76
1
3.2
9
65
.45
8
.59
58
8
.64
5
2.2
9
7.1
4
54
.85
4
.91
45
.34
1
3.6
6
45
.2
13
.15
5
1.6
8
7.6
2
70
.94
1
.12
5
0.8
7
9.5
4
54
.53
1
0.8
3
52
.5
12
.07
5
8.2
5
11
.11
5
4.5
9
7.4
7
68
.46
7
.54
77
.93
5
. 45
78
.85
2
.57
7
6.9
7
4.4
8
84
.99
1
.59
68
.6
4.7
9
83
.1
2.5
6
" "
77
.9
2.6
3
88
.1
2.7
1
37
.95
2
5.9
6
33
.36
4
0.5
7
40
.24
41
41
.65
4
0.7
2
7.
94
39
.59
34
.64
3
5.4
3
30
.64
3
7.9
4
24
16
.6
18
.5
18
.5
13
.4
26
.71
1
4.3
4 "
19
.47
9.
19
SiL
SL
L
L
SL
SiL
S
iL
L
SL L
L
L
L L
SL
LS
SL
LS
SL
LS "
LS
LS
........
........
1..0
Ped
en
Q3
b2
-3
Av
0-1
7
.49
8
Bw
k1
-u
1-2
0
8.8
6
8.6
B
wk
1-1
2
0-4
0
7.9
7
8.6
B
wk2
4
0-6
0+
8
.38
8
.5
Ped
en
Q3
b2
-4
Av
0-1
7
.42
7
.8
Bw
k1
-u
1-2
5
8.5
9
8.6
B
wk
1-1
2
5-4
6
9.4
3
8.4
B
wk2
4
6-6
9+
9
.17
8
.2
Ped
en
Q3
b2
-5
Av
0-1
Bw
1
-9
Bk
9-4
8
BC
48
-69
c
69
-18
0+
Ped
en
Q3
b2
-6
Av
0-1
Bw
1
-17
B
k1
17
-54
B
k2
-5
4-8
2
c 8
2-1
50
+
1.1
6
8.3
4
.83
0
.5
88
2.8
0
.6
II
II
1 9
2.1
2
.77
1.2
68
4
.79
0
.5
85
.1
1.7
8
0.9
3
II
II
1.
7 8
2.1
1
.81
26
.87
9
.2
II
5.1
3
27
.21
1
3.1
2
II
15
.49
SL
LS II
s
SL
L
S II
LS
~
N
0
APPENDIX C
SALT TRANSECTS
121
122
Table 12. Salt transects
distance Electrical geomorphic (meters) Conductivity location
(nunhos I em) Q2a 10 1 pavement 30 41 pavement 40 1 pavement so 2 pavement 60 39 pavement
Q3a-upper 0 1 shallow gulley 10 91 pavement 20 39 pavement 30 1 pavement
40 1 pavement so 4 pavement
60 2 pavement
Q3a-lower 0 19 channel edge
10 104 pavement
20 201 pavement
30 91 pavement
40 149 pavement
50 113 shallow gulley
