Pedogenic Gypsum of Southern New Mexico: Genesis, Morphology, and Stable Isotopic Signature

UNLV Retrospective Theses & Dissertations

1-1-2000

Pedogenic gypsum of southern New Mexico: Genesis, morphology, and stable isotopic signature

John Grant Van Hoesen University of Nevada, Las Vegas

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Repository Citation Van Hoesen, John Grant, "Pedogenic gypsum of southern New Mexico: Genesis, morphology, and stable isotopic signature" (2000). UNLV Retrospective Theses & Dissertations. 1186. http://dx.doi.org/10.25669/cudd-yb7b

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MORPHOLOGY, AND STABLE

ISOTOPIC SIGNATURE

John Van Hoesen

Bachelors of Science, Geology University of Albany 1998

A thesis submitted in partial fulfillment of the requirements for the

Master of Science Degree Department of Geoscience College of Sciences

Graduate College University of Nevada, Las Vegas August 2000

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Thesis Approval IJND/ The Graduate College University of Nevada, Las Vegas

July 21 _,20_QD_

The Thesis prepared by

John Van Hoesen

EntiUed

Pedogenic Gypsum in Southern New Mexico; Genesis. Morphology, and

Isptppic Signature.

is approved in partial fulfillment of the requirements for the degree of

Masters of Science ______

ExamrmtiOÊi Committee Chair

Dean o f the Graduate College

Examination Committee Member

2 Graduate College fa tu ity Représenta,

P R /1017-5.1/1-00 n

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT

Pedogenic Gypsum in southern New Mexico: Genesis, Morphology, and Stable Isotopic Signature

John Van Hoesen

Dr. Brenda J. Buck, Examining Committee Chair Assistant Professor of Geology University of Nevada, Las Vegas

Recent work in Canada and Iran (Dowuona et aL, 1992 and Khademi et al.,

1997a; 1997b) suggested a correlation exists between the and 8 D ratios of the

hydration water of pedogenic gypsum and the ô'*0/6D ratios of meteoric water.

However, a pedogenic origin for the sampled gypsum was not clearly supported and the

results &om this procedure were not compared to other paleoclimatic indicators.

Therefore, the goals of this study were, (1) evaluate the genesis and soil morphology of

pedogenic gypsum in arid to semi-arid regions and ( 2) determine the applicability of

pedogenic gypsum as a paleoclimatic indicator.

Six profiles containing soils of late Pleistocene through Holocene age in the

Tularosa and Jornada basins of Southern New Mexico were described and sampled for

isotopic analysis. Gypsum soil morphology was expanded to include a new “snowball”

morphology, as well as Stage I filaments and Stage II nodules, a classification scheme

formerly only applied to carbonate morphology. A pedogenic origin for gypsum crystals

111

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. found throughout the six profiles was determined using a scanning electron microscope.

These crystals do not exhibit any sign of re-precipitation, dissolution, or transport that

would suggest secondary crystallization and contamination fi*om yoimger meteoric water.

The hydration water of gypsum was extracted fi’om high-graded bulk sediment samples

containing gypsum and analyzed for and 6D iso topic values.

The 5*^0 and ÔD values collected fi’om the hydration water of gypsum were

substantially enriched in the heavier isotopes indicating extensive evaporation. There is

no trend between the isotopic signature of pedogenic gypsum and age, and there is no

trend with depth. No correlation exists between the isotopic signature of pedogenic

gypsum and the isotopic signature of pedogenic carbonate fixim this region. Results fiom

this study indicate that isotopic analysis o f pedogenic gypsum is not an applicable tool for

paleoclimatic reconstruction.

Authors Note: An HTML version of this manuscript, additional SEM and

fieldwork images not displayed in this manuscript, and relevant statistical data are

contained on the enclosed CD-ROM.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

ABSTRACT...... üi

LIST OF HGURES...... vii

ACKNOWLEDGEMENTS...... xi

CHAPTER 1 BACKGROUND...... 1 Purpose of Study ...... 1 Field Area Location...... 1 Geology and Geo morphology of the Tularosa and Jornada Basins ...... 3 Carbonate Horizon Morphology ...... 4 Gypsic Horizon Morphology ...... 7 Gypsum Soil Morphology ...... 9 Micromorphology of Gypsum ...... 10 Stable Isotopes Background ...... 13 Isotopic Fractionation ...... 13 Explanation of Delta Notation ( 6)...... 14 Oxygen and Hydrogen Isotopes Related to Paleoclimate ...... 15 Oxygen Isotopes from Pedogenic Carbonate ...... 20 Possible Sources of Error ...... 22 Oxygen Isotopes from Pedogenic Gypsum ...... 24 Possible Sources of Error ...... 26

CHAPTER 2 METHODOLOGY...... 27 Soil Profile Selection and Sampling ...... 27 Meteoric Water Sampling ...... 27 Texture Determination ...... 28 pH of Sampled Soil Profiles ...... 28 Scanning Electron Microscopy ...... 29 Hydration Water Extraction...... 29 Isotopic Analysis of Hydration Water of Gypsum...... 38 Radiocarbon Dating ...... 38

CHAPTER 3 SOIL PROFILE DESCRIPTIONS AND RESULTS...... 39 Jornada Basin ...... 41 Barbee Profile ...... 41 Dead Cow Grama Profile ...... 41 Big Apache Gap Profile ...... 47 Point of Rocks Profile ...... 52

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Tularosa Basin ...... 52 Death March Canyon Profile ...... 52 Three Rivers Profile...... 66

CHAPTER 4 PEDOGENIC CRYSTAL MORPHOLOGY RESULTS...... 75 Pedogenic Gypsum Macromorpho logy ...... 75 Snowball Morphology ...... 75 Stage I Gypsum ...... 83 Stage n Gypsum ...... 83 Stage n to Incipient Stage III Gypsum ...... 83 Pedogenic Gypsum Micromorphology ...... 86 Snowball Morphology ...... 86 Lenticular Crystals ...... 100 Tabular Pseudo-hexagonal Crystals ...... 100 Tabular Hexagonal Crystals ...... 105 Pseudo-hexagonal Lath Crystals ...... 105 Stage I Micromorphology ...... 105 Stage H Micromorphology...... 108 Pedogenic Carbonate Morphology ...... 108 Additonal SEM Images ...... 108

CHAPTER 5 GYPSUM HYDRATION WATER ISOTOPIC RESULTS...... 113 Introduction...... 113 Isotopic Composition of Gypsum Hydration Water ...... 114

CHAPTER 6 DISCUSSION...... 125 Soil Profile Relative Age Constraints ...... 125 Point of Rocks Profile ...... 125 Dead Cow Grama Profile ...... 126 Barbee Profile ...... 126 Big Apache Gap Profile ...... 127 Three Rivers Profile...... 128 Death March Canyon Profile ...... 129 Soil Profile Characteristics ...... 129 pH Analyses ...... 129 Vesicular Texture ...... 130 Low Clay Content ...... 132 Implications of Charcoal Horizons ...... 132 Evidence for Arididty ...... 133 Gypsum Morphology ...... 136 Snowball Morphology ...... 140 Stage n Gypsum ...... 140 Lenticular Crystals ...... 141 Tabular Crystals ...... 142 Lath Crystals...... 142 Isotopic Analysis of Hydration Water of Gypsum...... 142

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 7 CONCLUSIONS AND FUTURE RESEARCH ...... 147 Pedogenic Gypsum Crystal Morphology in the Tularosa and Jornada Basins ...... 147 Pedogenic Gypsum as a Paleoclimate Indicator ...... 147 Genesis of Pedogenic Calcium Carbonate...... 148

APPENDICES...... 150 Appendix 1. Soil Descriptions ...... 150 Appendix 2. pH and Statistical ...... 154 Appendix 3. Textural Analysis Data ...... 159 Appendix 4. Hydration Water of Gypsum Isotope Data...... 171

BIBLIOGRAPHY...... 173

VITA...... 180

CD-ROM Supplement ...... in pocket

V ll

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

Figure 1 Field area location map ...... 2 Figure 2 Geomorphology of southern New Mexico ...... 5 Figure 3 Latitude effect on 5'*0 and ÔD isotopic ratios ...... 16 Figure 4 Orographic effect on ô‘“0 and SD isotopk ratios ...... 17 Figure 5 Variations in S'*0 and SD isotopic ratios related to storm trajectories 18 Figure 6 Formation of pedogenic carbonate ...... 21 Figure 7 Formation of pedogenic gypsum ...... 25 Figure 8 Pictures of high graded bulk gypsum samples ...... 31 Figure 9 Diagram of gas extraction line ...... 32 Figure 10 Picture of manifold attached to gas extraction line ...... 33 Figure 11 Collection tube immersed in liquid nitrogen ...... 35 Figure 12 Tube cracker used to re-introduce the sample into the extraction line 36 Figure 13 U-shaped tube used to clean hydration water sanqile ...... 37 Figure 14 Picture of Barbee soil profile ...... 42 Figure 15 Summary of soil characteristics of the Barbee soil profile ...... 43 Figure 16 Soil texture diagram for the Barbee soil profile ...... 44 Figure 17 Picture of the Dead Cow Grama soil profile ...... 45 Figure 18 Summary of soil characteristics of the Dead Cow Grama soil profile ...... 46 Figure 19 Soil texture diagram for Dead Cow Grama soil profile ...... 48 Figure 20 Picture of the Big Apache Gap soil profile ...... 49 Figure 21 Summary of soil characteristics of the Big Apache Gap soil profile ...... 50 Figure 22 Soil texture diagram for the Big Apache Gap soil profile ...... 51 Figure 23 Picture of the Point of Rocks soil profile ...... 53 Figure 24 Summary of soil characteristics of the Point of Rocks soil profile ...... 54 Figure 25 Picture of large wedge shaped peds coated with gypsum ...... 55 Figure 26 Soil texture diagram for the Point of Rocks soil profile ...... 56 Figure 27 Picture of the Death March Canyon soil profile ...... 57 Figure 28 Summary of soil characteristics of the upper Death March soil profile ...... 58 Figure 29 Summary of soil characteristics of the lower Death March soil profile ...... 59 Figure 30 Soil texture diagram for the Death March Canyon soil profile ...... 61 Figure 31 Picture of the upper Three Rivers soil profile ...... 62 Figure 32 Picture of the lower Three Rivers soil profile ...... 63 Figure 33 Summary of soil characteristics of the upper Three Rivers soil profile ...... 64 Figure 34 Summary of soil characteristics of the lower Three Rivers soil profile ...... 65 Figure 35 Soil texture diagram for the Three Rivers soil profile ...... 67 Figure 36 pH dilutions in the Barbee soil profile ...... 68 Figure 37 pH dilutions in the Big Apache Gap soil profile ...... 69 Figure 38 pH dilutions in the Dead Cow Grama soil profile ...... 70

V I11

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 39 pH dilutions in the Death March Canyon soil profile ...... 71 Figure 40 pH dilutions in the Three Rivers soil profile ...... 72 Figure 41 pH dilutions in the Point of Rocks soil profile ...... 73 Figure 42 Similarity between the genesis o f pedogenic gypsum and carbonate ...... 76 Figure 43 Field picture of pedogenic gypsum snowball morphology ...... 77 Figure 44 Field picture of Stage I pedogenic gypsum ...... 78 Figure 45 Field picture of Stage II to incipient Stage III pedogenic gypsum ...... 79 Figure 46 Stereomicroscope image of fibrous pedogenic gypsum ...... 80 Figure 47 Stereomicroscope image of snowball morphology ...... 82 Figure 48 Stereomicroscope image of snowball morphology ...... 83 Figure 49 Stereomicroscope image of Stage 1 pedogenic gypsum ...... 84 Figure 50 Stereomicroscope image of Stage pedogenic gypsum...... 85 Figure 51 Exanqjle EDS images ...... 87 Figure 52 SEM images of the snowball morphology ...... 88 Figure 53 SEM images of the snowball morphology ...... 89 Figure 54 SEM images of the surface of the snowball morphology ...... 90 Figure 55 SEM images of the surface of the snowball morphology ...... 91 Figure 56 SEM images of organic material found within the soil profiles ...... 92 Figure 57 SEM images of organic material found within the soil profiles ...... 93 Figure 58 SEM images of organic material found within the soil profiles ...... 94 Figure 59 SEM images of organic material found within the soil profiles ...... 95 Figure 60 SEM images of the bacterium actinon^cetes ...... 96 Figure 61 SEM images of the bacterium actinonycetes ...... 97 Figure 62 SEM images of the bacterium actinon^cetes ...... 98 Figure 63 SEM images of the bacterium actinomycetes ...... 99 Figure 64 SEM images of lenticular pedogenic gypsum crystals ...... 101 Figure 65 SEM images of lenticular pedogenic gypsum crystals ...... 102 Figure 66 SEM images of lenticular pedogenic gypsum crystals ...... 103 Figure 67 SEM images of pseudo-hexagonal tabular pedogenic gypsum crystals 104 Figure 68 SEM images of tabular pedogenic gypsum crystals ...... 106 Figure 69 SEM images of lath shaped pedogenic gypsum crystals ...... 107 F igure 70 SEM images of pedogenic carbonate fimgal hyphae ...... 109 Figure 71 SEM images of pedogenic carbonate fungal hyphae ...... 110 Figure 72 SEM images of pedogenic carbonate needles ...... I l l Figure 73 SEM images of pedogenic carbonate filling root traces ...... 112 Figure 74 and SD plotted versus depth in the Barbee profile ...... 115 Figure 75 S'*0 and SD plotted versus depth in the Big Apache Gap profile ...... 116 Figure 76 S'*0 and SD plotted versus depth in the Dead Cow Grama profile ...... 117 Figure 77 S'*0 and SD plotted versus depth in the Death March Canyon profile 118 Figure 78 S‘*0 and SD plotted versus depth in the Point of Rocks profile ...... 119 Figure 79 S‘*0 and SD plotted versus depth in the Three Rivers profile...... 120 Figure 80 Isotopic plot of local meteoric water and hydration water values ...... 122 Figure 81 Comparison of hydration water of gypsum and water of crystallization.... 123 Figure 82 Isotopic values plotted versus relative age of soil horizon ...... 124 F igure 83 Picture of vesicular soil texture ...... 131 Figure 84 Picture of charcoal horizon in a clastic matrix ...... 134

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 85 ..... Picture o f large scale cut and fill feature in Death March Canyon ...... 135 Figure 86 Picture of large scale cut and fill feature in Death March Canyon ...... 137 Figure 87 Isotopic plots of precipitation illustrating evaporative enrichment ...... 145

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

I would like to recognize those organizations that provided financial support for

this project. My thanks to the UNLV Graduate Student Association and the UNLV

Department of Geoscience without support this project would not have been feasible. I

would like to thank Dr. Curtis Monger and Dr. Greg Mack fi’om New Mexico State

University who provided invaluable guidance during my fieldwork as well as throughout

the duration of the project, Sarah Lundberg spent many hours helping me on the SEM in

the Electron Microanalysis and Imaging Laboratory which was greatly ^preciated, and

Dr. Clay Crow was extremely patient with me as I ordered random and usually odd items

for this project. I would also like to thank John Kipp and Tim and Diane Lawton for

collecting rain samples for me in New Mexico. The hydration water of gypsum was

extracted at the University of Nevada, Reno under the guidance of Dr. Simon Poulson

and Dr. Greg Arehart Mk > were extremely generous with their time and lab space.

I would also like to thank the UNLV Department of Geoscience for providing

such an amazing work environment. Dr. Wanda Taylor and Dr. Peg Rees for always

having the right answers and Dr. Rod Metcalf for offering to save me from floundering!

Finally, I would like to thank Dr. Fred Bachhuber and Dr. Rik Omdorff for being so

helpful and supportive and for editing my thesis with such short notice. Enormous thanks

to my advisor Dr. Brenda Buck for giving me freedom with this project, for her support

and guidance, for pushing me every step of the way, for her enthusiasm, her good luck,

her sense of humor, and for always having to be different!

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 1

BACKGROUND

Purpose of Study

Recent work in Canada and Iran by (Dowuona et al., 1992; and Khademi et al.,

1997a; 1997b) suggested a correlation exists between the ô'*0 and 5D ratios of the

hydration water of pedogenic gypsum and the 5"0/5D ratios of meteoric water.

However, a pedogenic origin for the sampled gypsum was not clearly illustrated and the

results from this procedure were not conqiared to other well-established paleoclimatic

indicators.

The goals of this study were, (I) evaluate the genesis and soil morphology of

pedogenic gypsum in arid to semi-arid regions and ( 2) determine the applicability of

pedogenic gypsum as a paleoclimatic indicator. A better understanding of the overall

genesis of pedogenic gypsum was needed before an attempt could be made to interpret

the isotopic signature of pedogenic gypsum. Establishing pedogenic gypsum as a

potential paleoclimate proxy tool would be very useful in arid regions since very few

organic paleoclimatic indicators are preserved.

Field Area Location

The Jornada and Tularosa basins are located in southern New Mexico (figure 1)

and are separated by the San Andres and Organ Mountains. They are north trending

grabens formed during the Neogene, a result of extension caused by the inception of the 1

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7) ■DCD OQ. C 8 Q.

■D CD

C/) C/)

■D8 Location of Sampled

(O' Soil Profiles A Three Rivers San Andres * Big Apache Gap * Barbee o Dead Cow Grama 3"3. CD th and TULAROS * Death March ■DCD Consequence * Point of Rocks Q.O BASIN C a 3O Alamogordo ■o o

Q.CD JORNADA BASIN Dona Ana Mts m ■D CD (/) (/) New Mexico HUECO BASIN

300 Kilometers

Figure I : Field area location map in southwestern New Mexico produced from USGS digital elevation map. K» 3 Rio Grande rift (Blair et al., 1990, Se%er and Morgan, 1979). Approximate elevation

of the basins averages 1400 m. The basins are characterized by having an arid climate,

average daily temperatures are between 13° and 34°C, and average annual precipitation

of 24 cm. The source of winter precipitation is predominantly from the west originating

in the Pacific Ocean, although the majority falls during the summer monsoon season and

originates from the Gulf of Mexico (Blair et aL, 1990).

Quaternary landscape evolution of the Tularosa Basin of Southern New Mexico is

poorly understood. Access to Tularosa Basin is controlled by White Sands Military Base,

HoUoman Air Force Base, and White Sands National Monument. Limited access to the

basin may contribute to the lack of research in this region. However there has been

substantial research conducted on the surrounding basins, specifically the Hueco and

Jornada basins.

The arid climate of the region prevents the preservation of many organic

paleoclimate indicators at low elevations. Therefore, paleoclimate work in this region

has been restricted to studying the isotopic signature of pedogenic carbonate arid

morphology in eolian sediments o f lower elevations (basin floor) (Buck, 1996, Buck et al

1998, Buck and Monger, 1999), alluvial sediments along alluvial fans (Cole and Monger,

1994, Monger et aL, 1998) packrat middens in the high elevations along rocky cliffs (Van

Devander, 1990), and pluvial lake deposits (HaU, 1985).

Geology and Geo morphology of the Tularosa and Jornada Basins

The Tularosa Basin is bordered on the west by the San Andres and Organ

Mountains while the Sacramento and Jarillo Mountains border the eastern margin of the

basin. The San Andres Mountains are composed of Paleozoic sedimentary rocks.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4 primarily limestone and shale. In contrast, the Organ Mountains are composed of

Tertiary igneous rocks, the southern part of the Organ range is made up of rhyolite, Wide

the northern section is composed o f roonzonite (Gile et al., 1975). The Sacramento

Mountains are primarily conqx>sed o f Paleozoic limestone and shale but they do contain

a large igneous intrusion in the form of Sierra Blanca.

Research in the Jornada Basin has described carbonate morphology and the

alluvial soils related to five major valley border geomorphic surfaces (Gile et al., 1981):

the La Mesa (early-mid-Pleistocene), Jornada (late-mid- Pleistocene), Pichacho (late

Pleistocene), Leasburgh (latest Pleistocene), and the Fillmore (>2600-5000 years) (Gile et

al., 1981). The geomorphic surfaces described along the piedmont slope include the La

Mesa, Jornada I, Jornada II, Issacks’ Ranch, and Organ (figure 2) (Gile et aL, 1981).

These geomorphic surfoces formed through periods of erosion and sedimentation

during arid times, alternating with periods of landscape stability and soil formation

during wetter times. During arid periods the density of vegetation cover decreases and

the soil becomes unstable and is more susceptible to erosion and transport. During

moister periods the soil becomes more resistant to erosion as a result of surface stability

influenced by an increase in the density of vegetation cover. During these periods of

stability, illuviation of organic materiaL clay (if present), and soluble salts results in the

accumulation of these materials in the soil. Thus, the soils in this study are characterized

by accumulation of soluble salts such as gypsum, and calcium carbonate.

Carbonate Horizon Morphology

Pedogenic carbonate is common throughout the soils of the Tularosa, Jornada,

and Hueco Basins. Gile et al., (1966) described four distinct morphological stages for

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7) "DCD Q.O C Q.8

■D CD Stage II carbonate (/) morphogenetic

CD 8 3

Stage I carbonate CD morphogenetic -n 3-c sequence 3" CD ■oCD O CQ. a o 3 ■o o

co ■o CD

C/) Stage 111 and IV o' 3 carbonate morphogenetic sequence Figure 2: Schematic diagram of geomorphic surfaces previously described in the Jornada basin and their characteristic carbonate morphology (modified from Monger, 1995).

LA 6 pedogenic carbonate in the southwestern United States, while Bachman and Machette,

( 1977) added Stages V and VI to this classification system. These stages are directly

related to duration of sur&ce stability, therefore a relative geomorphic age has been

assigned to them. Horizons containing Stage I carbonate is thought to represent early to

middle Holocene age soil development. Stage II represents late Pleistocene, and Stage III

represents middle to late Pleistocene aged soil developmenL While Stage IV and greater

carbonate is thought to represent early to middle Pleistocene aged soil development.

Stage I is characterized by thin, discontinuous coatings on roots and pebbles in coarse

material, and filaments in fine material. Stage II contains continuous thin to thick

coatings on pebbles in coarse material and is characterized by spherical to semi-spherical

nodules in finer material. Stage III is indurated with carbonate, where all pore space is

completely or nearly completely filled with carbonate, which is also called a K horizon.

Stage IV is a result of the continued accumulation of carbonate producing a thin laminar

cap over the indurated Stage III horizon (Gile et aL, 1966; 1965). Stage V is

characterized by the presence of pisolites and vertical fractures while Stage VI contains

laminae, pisolites, and is brecciated (Bachman and Machette, 1977).

A variety of organic and inorganic foctors control carbonate precipitation and

development such as: ( 1) amount, seasonal distribution, and the concentration of Ca^^ in

rainfall, (2) amount of calcium carried and deposited by eolian processes, (3) in-situ

weathering of calcium silicate minerals, and (4) bacterial and fimgal activity which may

promote the production of pedogenic calcite, (5) influx of pCOi through atmospheric

diffusion, decomposition of organic materiaL and root respiration, and ( 6) supersaturation

of soil water caused by the removal o f water through évapotranspiration and evaporation

(Liu et aL, 1996 and Monger et al., 1991). The dominant foctor controlling the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 precipitation of pedogenic carbonate is the amount of calcium introduced into the soil

through atmospheric precipitation (Bachman and Machette, 1977 and Machette, 1985).

The dominance of atmospheric input of on carbonate accumulation is supported by:

(1) the presence of abundant calcic soils in non-calcareous parent material above present

and paleo-groundwater levels, ( 2) abundant local sources of calcic material in the form of

calcareous surficial deposits, lacustrine deposits, and calcic soils which provide a source

of carbonate which can be transported through eolian processes, (3) high concentrations

of calcium in dust throughout southern New Mexico, and (4) high concentrations o f Ca^^

in the rainfall of this region (Machette, 1985). Atmospheric input of Ca^^ is known to be

important in the formation o f pedogenic calcium carbonate and is likely to be an

important foctor in the formation of pedogenic gypsum, although this hypothesis was not

measured in this study.

Gypsic Horizon Morphology

Gypsic horizons are common throughout the world in arid and semi-arid

environments. These horizons are composed of pedogenic as well as detrital gypsum.

However, the formation of pedogenic gypsum is not thoroughly understood. The source

of the sulfate ion and amount of saturation with respect to gypsum defines the dominant

soil processes governing gypsum formatioiL Four potential origins for gypsum

accumulation in soils have been established: ( 1) in-situ weathering of existing parent

material, (2) oceanic source resulting in sulfate enriched precipitation, (3) eolian or

fluvial input o f gypsum or SO 4 sediment, and (4) in-situ oxidation o f sulfate minerals.

There may be other yet to be recognized origins for gypsum.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 8 Soils containing gypsic horizons can form in various parent materials such as

alluvium, eolian sediments, and weathered geologic formations (Taimeh, 1992). Carter

and Inskeep (1988) suggested pedogenic gypsum forms from original parent material

found within the sediments, such as gypsiforous shale and limestone, alluvium and eolian

sediments. They found pedogenic gypsum accumulation increased in soils with higher

contents of parent gypsum material (Carter and Inskeep, 1988). They suggested the

parent gypsum material in the alluvium was reprecipitated as pedogenic gypsum during

seasonal wetting and drying events (Carter and Inskeep, 1988).

Sulfate in the form of atmospheric precipitation may play an important role in

pedogenic gypsum formation. Water that ev^mrates off the ocean carries sulfate ions.

Therefore the pedogenic gypsum in some soils may have an oceanic source, with sulfate

ions being introduced to the soil in the form o f rainfall (Podwojewski and Arnold, 1994).

Another source of gypsiferous parent material is erosion of surficial gypsum deposits

(Taimeh, 1992). This can result in eolian or fluvial deposition of gypsic sediment on the

surrounding alluvium (Taimeh, 1992). Subsequent rainfall aids in the dissolution of the

detrital gypsum. Sub-surface evaporation may produce a solution supersaturated with

respect to gypsum and result in the precipitation of pedogenic gypsum (Taimeh, 1992).

Finally, gypsic horizons may form from the oxidation of pyrite (Mermut and

Arshad, 1987) or sulfide deposits having a volcanic origin (Podwojewski and Arnold,

1994, Toulkeridis, 1998). The combination o f sulfide oxidation, cation exchange

processes, and the hydrolysis of jarosite, may result in the formation of pedogenic

gypsum (Mermut and Arshad, 1987).

The source for the sulfate in this study is primarily from eolian and fluvial input

with minor input from in-situ weathering of parent material. The source for gypsum in

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 the Jornada basin is predominantly illuvial and fluvial additions of gypsiferous sediment

into the soils. In the Jornada Basin, the Yeso formation contains large-scale gypsum beds

and is well exposed in the Caballo Mountains that border the western edge of the Jornada

basin. Alluvial and eolian input provides a local source of sulfote for the soils located in

this region. Additional inputs of sulfate for this area most likely arise in the form of

atmospheric input from precipitation and eolian inputs from other geologic sources,

although these sources are likely very minor.

The greatest input in the Tularosa Basin is eolian sand from the White Sands

National Monument gypsiferous sand dunes. The large-scale Quaternary gypsum sand

dunes located in the Tularosa hasin provide a rich source of sulfote via eolian input.

White Sands National Monument is located in the southern portion of the basin and the

predominant wind direction in the area is southwest to northeast, providing a prominent

source for eolian input of weathered gypsiferous material throughout the basin.

Gypsum Soil Morphology

Pedogenic gypsum can be distinguished in the fleld from other soluble salts

through two simple tests. First is the lack of evffervescence when hydrochloric acid is

applied and the second involves placing a sample of the horizon in a test tube containing

water. If the water develops turbidity when BaCb (barium chloride) is added, then the

soluble salt can be identified as gypsum (Porta, 1998).

There are many important foctors controlling the soil morphology of gypsum

which include: (1) nucléation and growth rate as a function of soil temperature and

texture, (2) pH of the soil, (3) additional soluble ions, (4) organic matter, (5) the growth

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 medium for the crystals, and ( 6) stability o f the soil surface with respect to time (Magee,

1991).

Gypsum can occur as distinct gypsiferous horizons that can be classified based

upon percent gypsum (Stoops and Poch, 1998). Horizons containing less than 10% are

described as ecogypsic horizons, those containing 10-60% are gypsic horizons, those

containing 60-90% are hypergypsic horizons, and horizons containing greater than 90%

gypsum are hologypsic horizons (Stoops and Poch, 1998). Indurated horizons of gypsum

are termed gypcretes or petrogypsic horizons that are completely cemented with gypsum

(Florea and Hal-Joumaa, 1998). Gypsum can also occur as individual crystals commonly

displacing the soil matrix and exhibiting a vertical difluse texture (Carter and Inskeep,

1988).

Micromorphology of Gypsum

Determining a pedogenic origin for gypsum in soils may be accomplished by

studying the crystal morphology of gypsum and interpreting field relationships between

gypsic horizons. Previous work has described different morphologies for pedogenic and

diagenetic (non-pedogenic) gypsum (Carter and Inskeep, 1988) and for different episodes

o f soil development (Amit and Yaalon, 1996).

Pedogenic gypsum usually occurs as individual silt-and-sand sized euhedral to

subhedral crystals. The shape, size, and position of these crystals within the soil matrix

helps to differentiate whether they are pedogenic. Pedogenic gypsum crystals in soils of

southern Oklahoma were dominantly euhedral, spindle shaped, displaced the soil matrix,

and occurred in partially filled voids (Carter and Inskeep, 1988). Diagenetic gypsum

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11 (altered gypsum), on the other hand, was characterized by subhedral to anhedral crystals

which completely filled voids (Carter and Inskeep, 1988).

Gypsum in soils exhibits a variety of crystal forms that may represent different

environments of formatfon; lenticular disks, tabular pseudo-hexagonal, tabular

hexagonal, microcrystalline, prismatic, lath, and fibrous (Amit and Yaalon, 1996,

Jafarzadeh and Burnham, 1992). It has been suggested this diversity o f crystal

morphology is a result of changing microenvironmental conditions in soils over time

(Amit and Yaalon, 1996). Amit and Yaalon, (1996) have described the

micromorphology of different crystals (table 1) in gravelly soils found in Israel. These

crystal habits are controlled by a variety of localized conditions. Factors such as

alkalinity of the solution, pH, temperature, salinity, and abundance of organic material

affect the rate of crystal nucléation and therefore the ultimate crystal habit. Lenticular

crystals have been shown to form more readily in the presence of organic material and

other impurities such as sodium chloride (Cody, 1979). However it is not imperative for

organic material to be present since they have been described in soils with low organic

matter content (Jaforzadeh and Burnham, 1992). Tabular pseudo-hexagonal crystals are

associated with acid sulfate soils and are thought to precipitate from a rapidly

supersaturated solution followed by evaporation (Jaforzadeh and Burnham, 1992,

Tsarevsky et al., 1984). Prismatic crystals are commonly found precipitating in acidic

soils with a pH between 4 and 6, and have also been found at the base o f a fluctuating

water table (Jafarzadeh and Burnham, 1992, Pankova and Yamnova, 1987). Fibrous

gypsum has been explained as precipitating under strain but have also been attributed to

displacive crystallization (Jafarzadeh and Burnham, 1992). This suggests the growth of

gypsum may actually widen the crack in which it is forming.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12 Table 1. (from Amit and Yaalon, 1996).

Crystal Description Representative Environment Shape Alabastrine Microcrystalline, white in color, and Restricted to soils in which the upper horizon is Gypsum smooth like flour. Typically plugged restricting the depth of leaching. crystallizes by displacing host soil or Evaporation rates are typically higher. shattered fragments. Supersaturated saline solutions.

Lenticular Anhedral to subhedral in shape, Soils with high permeability as well as Gypsum poikilitic texture. Exhibits no increased NaCI content Typically formed particular preferred orientation in soil from impure saline solutions. Dry play matrix. sediments Prismatic Prians are euhedral, typically Rarely seen in arid regions, typical o f lacustrine Gypsum crystallize perpendicular to the plane environments. Thought to fixm imder acidic o f fracture, shattered fragments or conditions. gravel surface. Rarely seen in arid regions, suggested that Fibrous Crystallizes in the shape of needles or crystallization in a confined space enhances the Gypsum fibers. Typically radiate in all growth of these crystals. directions di^lacing the soil matrix or shattered fragments.

The broad distribution of crystal habits throughout a variety of soil types and soil

conditions suggests certain habits may form under certain conditions but are not limited

to this specific environment. It is likely that assigning each crystal habit to a specific soil

environment or texture is impossible, however understanding the varying factors

controlling their development, such as organic material, will aid in understanding their

genesis.

Stable Isotopes Background

A chemical element's atomic number is the number of positive charges (the

number of protons) in the nucleus o f each of its atoms. This number is the defining

characteristic of a given element, and remains the same for all atoms of that element.

However some atoms of an element can have a different atomic weight from others,

resulting in a different number of neutrons, producing an atom called an isotope.

Elements can exist in both stable and radioactive forms: those which are stable do not

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13 decay over time and retain a constant or “stable” isotopic signature while radiogenic

isotopes do decay over time producing daughter products and lose mass through gamma,

beta, or alpha decay or electron capture until they reach a stable electron state. Small

differences in the mass of stable isotopes are the reason they are useful for paleoclimate

studies. These differences in mass give rise to isotopic fractionation, which is the

fundamental atomic basis for stable isotopic paleoclimate studies.

Isotopic Fractionation

Isotopic fractionation is the fundamental process that results in the partitioning of

isotopes into distinct phases allowing us to correlate isotopic differences with climatic

change. Isotopic fractionation is a function of the atomic weight of each isotope. There

are three stable oxygen isotopes, **0, ‘^O, and ‘®0, where oxygen-18 is the heaviest and

oxygen-16 is the lightest. Isotopic analyses of oxygen typically represent the two end

members, since they have the strongest effect on the overall iso topic ratio. There are

many sources of isotopic fractionation in the oxygen isotope system. Evaporation results

in the preferential removal of lighter oxygen-16 isotopes leaving a more enriched solution

with respect to oxygen-18. Condensation and precipitation results in the preferential

removal of the heavier oxygen-18 isotopes leaving a more depleted atmospheric water

vapor with respect to oxygen-18. Rayleigh distillation processes are slowly occurring

and involve the immediate removal of the condensate from the vapor after formation,

leading to much higher fiactionation than normal (Dansgaard, 1964). Therefore, while

isotopic fractionation in oxygen is dependent upon atomic weight, temperature is an

extremely important contributing foctor to this process. The cooler the global climate the

more depleted atmospheric and meteoric water will become, leaving a precipitation

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14 record more enriched in '*0. Additional controls on the '*0/‘®0 ratio include melting of

polar ice caps during warmer periods. This melting of ice-caps, which store the lighter

isotope, results in an influx of the lighter isotope into the ocean, which is then

reflected in precipitation.

Hydrogen also has three stable isotopes 'H, ^H (deuterium), and ^H (tritium) that

react in a similar foshion as oxygen isotopes and reflect a similar isotopic trend when

they undergo the same type of isotopic fractionation as oxygen. The ‘H and ^H isotopes

are the two measured when obtaining a hydrogen isotope signature.

Explanation of Delta Notation (5)

Isotopic ratios are measures of the relative abundance o f isotopes, usually

arranged so the more abundant isotope appears in the denominator: i.e.- oxygen-18

isotopic ratio = '*0/'*0 = '*R. Where '*R is the ratio of heavy (or rare) isotope to the

light (abundant) stable isotope. Because of analytical limitations, the conventional

methodology is to compare the ratios of separate samples to a known value rather than to

directly measure the absolute isotopic abundance (Hayes, 1982). This method of

comparing the iso topic ratio of each sample to a pre-determined reference standard is a

differential comparison technique which allows for the measurement and comparison of

extremely small differences between isotopic ratios of differing samples (Hayes, 1982).

The notation used to express this relationship is the delta notation (5) first defined by

Urey, (1947).

0 "^XSTD= [ (^Rsample- '^RsTD)/^RsTD] X 10^

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15 5‘^XSTD is referred to as the delta measure in units of parts per mil (%o). Each isotope

system has a defined reference standard; measurements of oxygen isotopes in carbonates

are referenced to the Belemnhes of the Pee Dee Belemnhe formation (PDB), and

measurements of oxygen isotopes in water are referenced to Standard Mean Ocean Water

(SMOW).

Oxygen and Hydrogen Isotopes Related to Paleoclimate

Meteoric waters (lakes, streams, rivers, groundwater, etc) predominantly originate

from atmospheric precipitation. The origin of this precipitation is evaporation from the

ocean, most commonly near the equator. As discussed peviously, temperature defines

the ratio of the heavier isotope to the lighter isotope. Consequently, evaporation and

precipitation (thus ô " 0 and SO) varies with latitude (figure 3), altitude (figure 4), and

storm trajectories (figure 5) (Dansgaard, 1964, Gedzelman and Lawrence, 1990,

Amundson et al., 1996). Increasing latitude results in depletion o f the heavier isotope

which is removed from the condensate first and fells out in the form of precipitation

resulting in a vapor and therefore precipitation with a depleted S‘*0 ratio. An increase in

altitude produces the same depleted 5**0 ratio because as clouds rise and condensate

forms, the heavier isotope is the first to be removed from the system. Therefore higher

latitudes also have a more depleted S**0 ratio. The S'*0 ratio also varies with

precipitation source and is therefore directly related to storm trajectories and distance

from oceans. Storms originating in warmer waters will have an enriched ô‘*0 ratio while

those from cooler waters will have a more depleted 5**0 ratio. These variations

combined with global atmospheric circulation leads to a “pumping” effect of depleted

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16

ô‘*0 = 15 ÔD = 110

ô " 0 = -5 ÔD = 30 45

Figure 3; Illustration of latitude effect on ô'*0 and ôD isotopic ratios (modified from Dansgaard, 1964)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D Q.O C g Q.

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- 13% - 15% - 17 % V a p o r V a p o r V a p o r 3. 3" CD 111 II - 3% II 3 - 5% "O III Q.O | i Rainili R a in t ' C a III ,|iiiii, il • Mil,I 3O "O o III III Q.CD III g i s :

■D CD

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Figure 4; Orographic (altitude) and distance from ocean effect on the 6 "0 of precipitation (modified from Dansgaard, 1964). CD ■ D O Q. C 8 Q.

■D CD

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Figure 5 . Variations in average 5“0 in precipitation over North America, changing as a function of storm trajectories, latitude, elevation, and mean annual temperature (modified from Gedzelman and Lawrence, 1990). 00 19 water vapor from low to high latitudes which results in the global and local variation in

isotopic ratios (Dansgaard, 1964).

It has been shown that the isotopic variation in global precipitation defines the

Meteoric Water Line (MWL) (Craig, 1961). The MWL is defined as:

ÔpD = 8ôp'*0 + d

Where ÔpD is the ÔD o f precipitation, 0p**0 is the ô'*0 of precipitation, and d is the y-

intercept with a global average of 10 (Craig, 1961). The value d can be obtained by

rearranging the formula:

d = ôp D - 8 ôp"'0

Where d now represents the “deuterium excess factor” initially defined by Dansgaard,

(1964). This allows for a Local Meteoric Water Line (LWL) to be defined, which can be

compared to the global MWL. Variations from the MWL represent times of increased

evaporation or precipitation, isotopic ratios which fall below the MWL represent areas of

evaporation, while those values that plot above the MWL represent times of precipitation

(Craig, 1961). Isotopic fractionation is typically greater between hydrogen and

deuterium isotopes because the mass difference between the two isotopes is greater,

however they respond to temperature changes exactly like oxygen isotopes. The heavier

deuterium isotope behaves in a similar manner as oxygen-18 in response to latitude,

altitude, and storm trajectories and distance from oceans.

Therefore, wherever ancient water is preserved, and if these isotopic values can be

obtained and measured, the data can be used to infer the paleoclimate of a region. One

suitable method, which has been established as an applicable paleoclimate proxy, is the

analysis of ô'*0 of calcium carbonate. Meteoric water percolates into the subsurface and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20 combines with calcium and carbon dioxide ions to form calcium carbonate. Thus

analysis of the S'*0 ratio of the carbonate reflects the 0**0 of the prehistoric meteoric

water and can be used to infer paleoclimate (figure 6).

Oxygen Isotopes fi’om Pedogenic Carbonate

Past research has shown the merits of using carbon and oxygen isotopes of

pedogenic calcium carbonate to interpret paleoclimate, paleotemperature and/or storm

sources (Cerling 1984,1991, Amundson et al., 1989, 1996,1998, Quade et al., 1989, Cole

and Monger, 1994, Cole and Monger, 1994, Lhi et a t, 1996, Monger et aL, 1998, Buck

and Monger, 1999, Wang et al., 1994). Eolian and illuvial processes supply the

necessary Ca^^ ions which mix with CO2, derived from plant respiration, atmospheric

diffusion, or decomposition of organic material, and H2O in the form of precipitation to

form pedogenic CaCOj (figure 6).

By measuring the isotopic ratio of **0 to *^0 (0**0) in pedogenic carbonate it is

possible to infer the paleotemperature and/or storm sources of a region. The assumption

here is that the source for the oxygen in CaCOs is atmospheric precipitation which

percolates into the ground becoming soil water (Cerling, 1984). The mass of the oxygen

in CO2 is considered insignificant compared to that of soil water and since soil carbonate

accumulation rates are thought to be considerably lower than fluxes in biogenic CO2, the

0**0 of pedogenic carbonate is thought to represent the isotopic composition of soil

water.

It has been shown that the 6**0 value o f precipitation is a function o f temperature,

latitude, and altitude (Dansgaard, 1964). However, temperature is the dominant

controlling factor in the 6**0 of precipitation (Dansgaard, 1964). The 6**0 o f

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C 8 Q.

■D CD

C/) C/)

8 S^^O/SD of water in precipitation

CD O O 3. 3" CD ■DCD O Q. C a O 3 ■D H ,0 CO2 input from O Calcium input from precipitation plant respiration CD Q. \ Ca + CO2 + H2O ■D CD

C/) C/) C aC 03

Figure 6: Source of components involved in the formation of pedogenic calcium carbonate. Atmospheric water is the source for the soil water, thus isotopic analysis of this water reflects that of paleo-precipitation and can be used for paleclimate reconstuction. N> 22 precipitation undergoes isotopic fractionation as temperature decreases (condensation),

and enrichment as temperature increases (evaporation) (Epstein and Mayeda, 1964). This

is a result of Rayleigh distillation processes, which involves the preferential removal of

the lighter isotope during condensation (Dansgaard, 1964). Therefore, the 5**0 ratio of

pedogenic carbonate may reflect the paleotemperature o f precipitation or represent the

source of the precipitation which percolated into the soil (Cerling 1984,1991, Amundson

et al., 1989, 1996,1998, Quade et al., 1989, Cole and Monger, 1994, Monger and Cole,

1994, Liu et al., 1996, Monger et aL, 1998, Buck and Monger, 1999, Wang et aL, 1994).

Possible Sources of Error

Possible problems regarding the use of oxygen isotopes to infer paleotenqierature

are latitude effects (Dansgaard, 1964), altitude effects (Dansgaard, 1964), seasonallity of

precipitation associated with storm trajectories and source of precipitation (Amundson, et

aL, 1996, Lawrence et al., 1982), soil temperature where the carbonate precipitates, and

evaporation prior to carbonate precipitation (Cerling and Quade, 1993). Interpreting

paleoclimate from oxygen isotopes from low-latitude to mid-latitude areas is problematic

since these regions are characterized by convective rainfall during the summer (Lamb,

1977). This type of precipitation has a variety of heights and therefore temperatures, at

which condensation can occur (Lamb, 1977).

Isotopic enrichment of 6**0 and ÔD values results from higher temperatures of the

original precipitation and the water source for this precipitation (i.e. Gulf of Mexico

versus Pacific Ocean), season in which this precipitation originates (summer versus

winter) and increased surface and sub-surface evaporation (Cerling, 1984, Amundson

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23 et al., 1989). Other fectors that affect 6**0 and 6D values are depth o f wetting where

decreased depth of wetting may increase isotopic fractionation by retaining the water

higher in the profile thus increasing soil water evaporation. Depth of wetting is directly

controlled by soil texture, soil structure, surface cover, and clay content (Liu et al., 1996).

Sandy soils will result in deeper depth of wetting as compared with clay or clay loam

soils that will restrict percolation and cause increased evaporation. Strong well

developed soil structure, specifically prismatic, also inhibits water infiltration and likely

increases evaporation compared with weakly developed granular or unstratified soil in

which depth of wetting is markedly greater. Related to soil structure is the clay content

of soil. Higher concentrations of clay in soil will result in stronger soil structure that

promotes increased evaporation and fractionation. Surface crusts conqx)sed of soluble

salts (halite, gypsum, carbonate, etc) are commonly found in arid regions. These surfoce

crusts have a low permeability to water as conq)ared to sand dunes or unstratified soil and

again may contribute to increased evaporation (Gile 1966, Watson, 1988, Watson, 1985).

Once water has penetrated the crust however, surfoce crusts may decrease the evaporative

effect. Desert pavement found on the surfoce of many desert soils also results in

decreased evaporation. Increased plant cover results in less evaporation by providing a

stable soil surface that reduces runoff as well as reducing the amount of direct sunlight on

the soil surface. An increase in plant cover also results in an increase in transpiration,

however, the process of transpiration has been shown to have no effect on 6**0 and ÔD

values (Cerling, 1984).

Since the presence of gypsum results in decreased soil structure, decreased soil

cohesion, and restricted root growth it is likely these factors also contribute to enrichment

or depletion of 6**0 and 6D values in pedogenic gypsum (Poch et al., 1998). They need

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24 to be addressed when interpreting and applying these values to paleoclimate

reconstruction.

Oxygen Isotopes from Pedogenic Gypsum

Previous research suggested the 6**0 and 6D from the formation water of gypsum

might be useful in paleotemperature reconstruction (Halas and Krouse, 1982, Dowuona et

al., 1992, Khademi et aL, 1997a, 1997b, and Podwojewsld, and Arnold, 1994).

This method suggests the formation water of gypsum is in equilibrium with surrounding

soil moisture which is dependent on atmospheric precipitation in arid regions (Dowuona,

et al., 1992, Khademi et al., 1997b). The formation water of gypsum is thought to be in

equilibrium with meteoric water in arid soils because the source for this water is

atmospheric precipitation that infiltrates into the soil and combines with calcium and

sulfate ions to form gypsum (figure 7). Therefore, the source of hydration water in

gypsum is meteoric water, and since the fi^tionation foctor between the water of

crystallization and the soil water is known (Gonfiantini and Fontes, 1963) the 6**0/ ÔD

values obtained from the hydration water of gypsum have the potential to reflect the

6**0/6D signature o f past precipitation (Dowuona, et al., 1992, Khademi et al., 1997b).

The isotopic signature of the mother water is calculated using the following equation:

a = 6wc + 1000 6mw + 1000

where 6wc is the 6**0 and 6D isotopic composition of the water of crystallization of

gypsum and the 6mw is the 6**0 and 6D isotopic composition of the mother water, a is

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C 8 Q.

■D CD

C/) C/)

S*^0/ÔD of water in ■D8

(O' precipitation

3. 3" CD ■DCD O Q. C Oa 3 H ,0 ■D O

CD Q. \ Ca + SO4 + 2HnO ■D CD (/) / (/) C aS 04 ZHoO

Figure 7; Source of components involved in the formation of pedogenic gypsum. Atmospheric water is the source for the soil water, thus isotopic analysis of the hydration water of gypsum should reflect that of paleo-precipitation and could be used for paleoclimate reconstruction. N» V* 26 the fractionation factor and has been defined as 1.004 for **0 and 0.98 for 5D

(Gonfiantini and Fontes, 1963 and Pradhananga and Matsuo, 1985).

Possible Sources of Error

Problems that need to be addressed (other than those which also affect isotope

values of pedogenic carbonate) when using this procedure include re-equilibration of

gypsum with younger water during altemating wetting and drying cycles, surfoce and

sub-surface evaporation of soil water prior to crystallization of gypsum resulting in an

enrichment of 5**0 (Dansgaard, 1964), rehydration of anhydrite to gypsum, and

diagenetic versus pedogenic gypsum. However, it has been shown that the oxygen in the

sulfate (CaS04«2H20) ion of gypsum does not present a source of potential error at these

low temperature analyses (Dowuona et al., 1992).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 2

METHODOLOGY

Soil Profile Selection and Sampling

Six soil profiles exposed in dry arroyo cuts within the Jornada and Tularosa

basins were selected for analysis based upon the presence of buried soils containing

visible gypsum. Sanq>le location coordinates were collected using a Trumbell GPS

receiver, however a field base station was not available for correction of selective

availability.

Approximately 4-18 cm of soil was removed from the surface of the soil profiles,

exposing a fresh soil surfoce to prevent sanq)ling soil contaminated by modem surfoce

water. Each profile was then described using the methodology outlined in the Field Book

for Describing and Sampling Soils, Shoenberger et aL, (1998) and soil color was defined

using a Munsell Soil Color Chart. Unconsolidated soil and individual soil peds from

each described horizon were collected in large zip lock bags for analysis.

Meteoric Water Sampling

Surfoce waters were sampled by hand by dipping a plastic water vial into the Rio

Grande and Three Rivers creek. The vials were completely filled, labeled appropriately,

and stored in a cooler o f ice for transport back to the lab where they were stored in a

refrigerator for analysis. Precipitation was collected during the summer monsoon and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 28 winter using a self-built rain gauge. The rain gauge was constructed using a 1-quart

Rubbermaid thermos, a funnel, ping pong ball, and colander. The funnel was attached to

the thermos and duct-taped in place; the ping pong ball was placed in the funnel and the

colander was placed inside the funnel and again duct taped in place. Three such rain

gauges were constructed and placed in the Las Cruces area. During storm events the

funnel collected the water; the colander prevented clogging by airborne debris, and the

Ping-Pong ball reduced the effect of evaporation. These samples were immediately

collected and refrigerated to prevent fractionation.

Texture Determination

Particle size analysis was performed on each horizon in the six sampled soil

profiles using the hydrometer method described by Gee and Bauder, (1986).

Approximately 40-100 grams o f soil (depending on texture) from each horizon was

placed in a 450 ml glass beaker and labeled appropriately. Pretreatment involved adding

approximately 100 ml of distilled water and 10 ml of 1 M NaOAc (sodium acetate) to the

beaker to remove carbonates and soluble salts. Only those samples from horizons

containing visible organic matter were pretreated with 30 % H2O2 (hydrogen peroxide).

After removal of carbonates and soluble salts, 25 ml o f distilled water and 5 ml of H2O2

was added to the beaker containing the soil. The beaker was placed in a 1000-ml beaker

containing cold water to prevent excessive frothing. After the cessation of H2O2 frothing,

the beaker was placed on a hot plate and heated to 90° C to remove any excess peroxide

from the sample.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29 pH of Sampled Soil Profiles

The pH of each horizon was determined following the guidelines in the Soil

Survey Laboratory Methods Manual (1996).

Scanning Electron Microscopy

Samples were chosen for scanning electron microscopy (SEM) based upon the

visual presence of gypsum and location in the soil profile. Those horizons containing

gypsum visible with the naked eye were sampled first, and horizons surrounding them

were sampled second. The selected samples were stored in plastic screw top containers

and labeled appropriately.

Sample preparation of soil material for SEM and energy dispersive X-ray analysis

(EDS) analyses involved pre-heating the selected samples below 40°C (to prevent

dehydration of gypsum) for 48 hours to focilhate sample sputtering. Samples were then

sized appropriately to fit in the SEM, attached to a brass cylinder with carbon-coated

tape, and sputtered for 30 seconds with a gold/platinum coating using a Model 3 Pelco

Sputter Coater. SEM and EDS analyses were performed on a JEOL 5600 scanning

electron microscope and an Oxford ISIS energy dispersive x-ray system to determine if

the gypsum was pedogenic and characterize the gypsum micro morphology of these soils.

Hydration Water Extraction

Samples were chosen for water extraction and subsequent isotopic analysis based

upon SEM analysis indicating the presence of abundant unaltered pedogenic gypsum and

location in the soil profile. An attempt to sample a broad distribution of the profile was

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 30 made, sampling upper and lower horizons, those horizons separated by distinct abrupt

boundaries as well as those with distinct changes in gypsum morphology.

Previous workers picked individual gypsum crystals from the soil matrix and

analyzed them separately. However, the texture and size of the gypsum crystals

throughout the sampled soil profiles didn’t allow complete isolation of the gypsum from

the soil therefore high graded bulk samples (figure 8) were analyzed rather than pure

gypsum. The selected samples were stored and transported in plastic screw top

containers and labeled appropriately. The extraction process was conducted on a gas

extraction line (figure 9) in the stable isotope lab at the University of Nevada, Reno over

the course of 4 weeks and followed a modified methodology used by previous

researchers (Gonfiantini and Fontes, 1963, Dowuona et aL, 1992, and Khademi et al.,

1997a; 1997b).

Medium wall Pyrex tubing o f 1/4” and 3/8” was cut into 8-inch lengths and one

end of each length was sealed with an oxygen/natural gas torch. The 1/4” tubes were

used for water collection and the 3/8” tubes housed the soil sample during heating.

Each test tube was then attached to the extraction line manifold (figure 10) and outgassed

for approximately 2 minutes to remove any water produced during the sealing process.

Soil samples ranging in size from 5-7 grams were placed in 3/8” tubes followed

by a small piece of quartz wool to prevent contamination of the extraction line with soil

and attached to the extraction manifold. Previous workers used larger sample sizes,

however when this was attempted too much excess gas was produced and the hydration

water was trapped in the sample tube and extraction manifold. Thus, to prevent

fractionation, smaller samples were used which in turn produced less water. The 1/4”

tubes were also attached to the manifold and sealed halfway to facilitate the final sealing

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31

DM 320-341: High grmded soil sanq»lc.

A-.- « y.

' 4 r , - w

V - -

BP 18-62: High graded soil sample.

Figure 8: Example of high graded soil samples used for oxygen and hydrogen isotope analysis.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C 8 Q.

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Figure 9; Diagram showing location of extraction line elements. u> w 33

ë 0

a I S V

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34 of the tube. The sample tube was then placed inside a 2-mm diameter ceramic furnace

and degassed at 40"C (to prevent dehydration of gypsum) for approximately 0.5 to 1 hour

to remove any COj or water trapped in the soil. The samples were then step-heated in

100°C increments to 450"C and the 1/4” collection tube was immersed in a 350 ml Dewar

flask containing liquid nitrogen (figure 11) causing the water released fi-om the gypsum

to condense in the bottom of the collection tube. Tenq)erature was tightly controlled with

an Omega thermostat-thermocouple system connected directly to the ceramic furnaces.

After the samples were heated to 450"C, the collection tube was sealed ofif and allowed to

warm to room temperature. A single collection tube was then attached to the extraction

manifold and broken in a tube cracker (figure 12) re-introducing the water to the

extraction line. This tube cracker was used to re-introduce the water into the system to

prevent atmospheric contamination and reduce isotopic fiactionation. The water was

then collected in a u-sbaped tube immersed in a dry ice ethanol slush (figure 13). This

allowed contaminants with higher vapor pressures to be pumped away since a dry ice

ethanol slush maintains a temperature o f approximately —78"C compared to liquid

nitrogen which has maintains a temperature o f approximately —196°C. Once all

contaminants with a higher vapor pressure were pumped out of the system and all the

water condensed on the u-shaped tube, the dry ethanol slush was removed and the water

was allowed to warm to room temperature. A second collection tube connected to the

extraction manifold was then immersed in liquid nitrogen causing the water to once again

condense in the collection tube. The process was expedited with a hair dryer to ensure all

water vapor was liberated from the glass extraction line. Water vapor is highly cohesive

under pressure in a glass extraction line and this added heat source reduces the amount of

water vapor remaining in the system again preventing isotopic fractionation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35

Figure 11 : Close-up picture of collection tube immersed in liquid nitrogen.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 36

Figure 12: Close-up picture of tube cracker used to re-introduce the sample into the extraction line.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 37

" m m mm ■

KSr~*r»-' "''/•'

Figure 13: Close-up picture of u-shaped tube used during cleaning of the sample.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 38 The collection tubes were then labeled appropriately and wrapped in bubble wrap

to prevent cracking during transport to the Stable Isotope Laboratory at the University of

New Mexico, Albuquerque for isotopic analysis. Finally, the heated sample tubes were

sealed and labeled appropriately for SEM analysis to characterize the impact of heating.

The extraction process was slow and tedious, allowing for the analysis of only 2 samples

per eight-hour while sample cleaning in the dry ice ethanol slush was less time

consuming. Approximately 4-6 samples per hour were re-introduced into the extraction

line, cleaned, and labeled for analysis.

Isotopic Analysis of Hydration Water of Gypsum

The ô“ 0 and 5D isotopic analyses were conducted on 30 water sanq)les at the

University of New Mexico, Albuquerque in the Stable Isotope Laboratory, directed by

Zachary Sharpe, during the spring o f2000. Five samples were local surface and

precipitation water, and the remaining 25 samples were hydration water from pedogenic

gypsum. Four samples came from the Dead Cow Grama soil profile, seven from Three

Rivers, four from Death March Canyon, three from Point of Rocks, four from Big

Apache Gap, and two were from the Barbee profile. Four samples from the Barbee

profile were sent for isotopic analysis but two were broken en route.

Radiocarbon Dating

Bulk sediment was collected from those horizons containing charcoal in the Three

Rivers profile and high graded to concentrate the charcoal. The samples were then sent

to Beta Analytical for pretreatment, calibration, and radiocarbon dating. Due to the

extremely fine-grained nature and small quantity of the charcoal, AMS (accelerator mass

spectrometry) was utilized rather than the conventional beta-counting method.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 3

SOIL PROFILE DESCRIPTIONS AND RESULTS

The six soil profiles in this study were sampled in the Jornada and Tularosa basins

of southern New Mexico (figure 1). The Barbee, Dead Cow Grama, Point of Rocks, and

Big Apache Gap profiles were sampled in the Jomada basin, which is located on the

western side of the San Andres Mountains. The Three Rivers and Death March Canyon

profiles were sampled in the Tularosa basin, which is east of the San Andres Mountains

and west of the Sacramento Mountains. These basins reside in a semi-arid climate and

are characterized by an accumulation and illuviation of soluble salts such as calcium

carbonate and gypsum.

The four soil profiles sampled in the Jomada Basin receive illuvial, eolian, and

fluvial input of gypsiferous material with a minor contribution of gypsic material fi’om in

situ weathering of alluvial gypsiferous parent material in the Barbee and Big Apache Gap

profiles. The parent material for Barbee and Big Apache Gap profiles is primarily a

sandy alluvium derived from a sedimentary sequence containing a large local source of

gypsum, the Yeso formation. The Yeso formation is composed of four sedimentary

Paleozoic members, the Mcseta Blanca, red siltstone-dolomite, limestone, and sandstonc-

limestone (Mack and Suguio, 1991). The red siltstone-dolomite member contains

approximately 70% gypsum and is exposed throughout the linear extent of the Caballo

Mountains. Gypsum beds are exposed in the Caballo Mountains with a maximum

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 40 thickness of 90 m and occur as ahemating coarse and fine-grained gypsum containing

thin dark laminae (Mack and Suguio, 1991). The Yeso formation has a wide geographic

extent and is greater than 600 m thick in some areas. This provides another source of

eolian gypsum through surficial weathering o f e?qx>sed large-scale gypsum beds.

The parent material for Point o f Rocks and Dead Cow Grama soil profiles is

sandy alluvium primarily derived from igneous rocks in the Point of Rocks mountain

range, although minor input from surrounding sedimentary outcrops and local playas is

likely. The source of gypsum in the Three R ivas and Death March Canyon soil profiles

is eolian and alluvial sediment from surrounding Paleozoic sedimentary rocks and the

Quaternary gypsum dune fields located in White Sands National Monument. The parent

material for these two profiles is a mixture of igneous material from Sierra Blanca, a

-12,000 foot Tertiary igneous intrusion, and Paleozoic sedimentary units in the

Sacramento Mountains. Gypsum input is primarily from the White Sand dune fields,

which are located approximately 10-15 miles to the south of the san^led profiles. Eolian

processes deposit gypsiferous material on the surface of the soil and subsequent

illuviation of this material results in precipitation of gypsum crystals at depth. The

Sacramento Mountains to the west of this basin are composed of Mississippian and

Pennsylvanian limestones with interbedded shales, overlain by the Permian Abo

mudstones and Yeso limestones and gypsum, and capped by the San Andres Limestone.

(Bowsher, 1986). The Yeso formation is poorly exposed in the region surrounding the

sampled profiles, but may offer a minor sulfate contribution to the soil.

Appendix 1 summarize the master horizon, structure, color, boundary, and crystal

morphology of each horizon from all six profiles, appendix 2 summarizes the pH data

from each horizon, and appendix 3 contains the texture analysis data.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41 Jomada Basin

Barbee Profile

This profile was sampled in an exposed arroyo at the distal end of an alluvial fan

propagating from the Caballo Mountains (figure 14). This profile was sanq)led and

described to a depth o f240 cm based on texture, color, horizon boundaries, and soil

structure (figure 15). Surfoce lag consists of limestone and the dominant vegetation is

creosote bush and mesquite. Profuse root traces or vesicles, -1-3 mm in size, are present

throughout the entire section, but decrease in number at depth. These are very similar to

an Av horizon (vesicular), but their presence throughout the entire profile suggests they

may have formed by other means. Textural analyses indicate the profile is dominantly

sandy loam (figure 16).

The upper 120 cm o f the profile contains numerous Stage I gypsum filaments (—1-

5 mm long), snowballs (—1-3 mm in size), and fine (1 mm to 1 cm) roots coated with

gypsum. Between 120 and 213 cm gypsum gradually becomes more common and

massive. However, a thick Stage m calcic horizon is present below 213 cm which does

not contain gypsum.

Dead Cow Grama Profile

This profile was sampled in an exposed arroyo residing in a valley between the

Caballo Mountains the Point of Rocks (figure 17). This profile was sampled and

described to a depth o f255 cm based on texture, color, horizon boundaries, and soil

structure (figure 18). Surface lag consists of 1-5 cm rhyolitic pebbles and the dominant

vegetation is grass, creosote bush, and mesquite. This profile

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 42

-isaaaK

Figure 14: Vertical section of Barbee Profile showing sampled horizons.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 43 Depth Horizon (cm) Structure Color Texture Morphology 0-18 None 7.5YR 6/4 SUty Highly CaCO, 1 2 - light brown Loam

24— Abrupt and distinct boundary

3 6 - 18-62 Strong sub- 7.5 YR 5/3 Sandy Highly CaCOj angular blocky brown Loam Rare Stage 1 4 8 - gypsum and common snowballs 6 0 . Gradual boundary 7 2 - 62-120 Strong sub- 7.5YR 5/4 Sandy Highly CaCOj angular reddish Loam Prominent Stage 1 9 6 - a blocky brown gypsum filaments and common snowballs Abrupt boundary

120-160 Very strong 5YR 5/4 Sandy Highly CaCOj prismatic to Loam Promient Stage 1 angular blocky gypsum filaments and some Stage II nodules. Very Gradual boundary common snowballs 168- ;if] ZBtky 160-175 Very strong 5YR5/4 Sandy Highly CaCOj prismatic reddish brown Loam Stage I gypsum Gradual boundary filaments and snowballs B a s 175-213 Strong 5YR6/4 Sandy Highly CaCOj angular light reddish Loam Promient Stage I blocky brown gypsum filaments ------► Abrupt boundary and common snowballs 213-240 Massive 5YR8/3 Sandy Stage III gypsum incipient pink Loam Stage III gypsum

Figure 15: Barbee soil profile summarizing soil structure, color, texture, and crystal morphology.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44

40 %

100 100 90 80 70 60 50 40 30 20 10 0 Sand Separate, %

Figure 16: Textural diagram for Barbee Profile indicating it is predominantly sandly loam.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 45

Figure 17: Vertical section of Dead Cow Grama Profile showing sampled horizons.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46

Depth Horizon (cm) Structure Color Texture Morphology Strong platy 7.5YR6/4 Silty Highly CaCOj light brown Loam Abrupt and distinct boundary 2-12 Strong platy 7.5 YR 5/4 Silty Highly CaCO, brown Loam Stage I gypsum ► Clear boundary 12-50 Strong sub- 5Y R 5/4 Silty Highly CaCO, angular blocky reddish brown Loam Stage I gypsum ->■ Gradual boundary 50-90 Strong 5YR5/4 SUty Highly CaCO, n2BtkyK prismatic reddish Loam Stage I gypsum brown f ilaments and ------► Diffuse boundary some snowballs 90-108 Moderate sub- 7.55/4 Silty Same as above a 2Bky angular blocky brown Loam Clear boundary

108-158 Strong long 5YR6/4 Silt Stage I gypsum prismatic light reddish filaments brown

► Diffuse boundary

158-215 Weak sub- 7.5YR 6/4 Silt Highly CaCO, angular blocky light brown Stage I gypsum and stratified filaments and Stage n nodules

► Clear but not abrupt boundary

215-255 No structure 7.5YR7/4 Loamy Highly CaCO, fluvial sand pink Sand No visible gypsum

Figure 18: Dead Cow Grama soil profile summarizing soil structure, color, texture, and crystal morphology.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 47 contains abundant primarily vertical fine (1-3 mm) root traces or burrows. Textural

analyses indicate this profile is silty loam to silt (figure 19).

This profile contained abundant, visible snowballs displacing the soil matrix and

commonly filling root traces. There are common 1-5 mm long Stage I filaments and root

coatings of gypsum in the upper 100 cm, transitioning into weak 1-3 cm Stage H nodules

of gypsum near the bottom o f the profile. The lower section of the profile contains a

coarse pebble horizon beginning at 158 cm and below 215 cm is a 40-cm thick section of

well-sorted and rounded quartz and feldspar fluvial sand.

Big Apache Gap Profile

This profile was sampled in an exposed arroyo at the distal point of an alluvial fen

propagating off of the Caballo Moimtains (figure 20). This profile was described to a

depth o f305 cm. Samples were taken fi’om each horizon based on texture, color, horizon

boundaries, and soil structure (figure 21). Surface lag consists of conglomerate and

igneous pebbles and dominant vegetation includes grass, creosote bush, and sagebrush.

This profile contains the previously described 1 -3 mm fine vesicles, but they were not as

common here as they were in the Dead Cow Grama, Barbee Profile, and Point of Rocks

profiles. However, the abundance o f vesicles increases with increasing gypsum content.

Soil structure is almost entirely prismatic, with the exception of weak platy A horizon at

the surface, and the texture is most commonly sandy loam (figure 22). Stage I gypsum

and snowballs dominate the upper 230 cm of this profile with a weak Stage II gypsum

horizon between 230 and 260 cm. This incipient Stage II gypsum horizon is underlain by

coarse Quaternary age gravel containing 5-10 cm clasts coated with calcium carbonate,

and Cretaceous Mancos shale underlies this gravel.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48

100

90 20

60 50 t ,

60 -2- 40

£ja; lam. 70

m dW o lam

sa 100 0 100 90 80 70 60 50 40 30 20 10 0 Sand Separate, %

Figure 19: Textural diagram for Dead Cow Grama profile indicating it is predominantly silty loam.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 49

Figure 20: Vertical section of Big Apache Gap Profile showing sampled horizons.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 50

Depth Horizon (cm) Structure Color Texture Morphology 0-6 Weak Platy 7.5YR 6/4 Sandy Highly CaCO, light brown Loam I—^ Abrupt and distinct boundary

6-68 Strong sub- 7.5 YR 5/3 Loamy Highly CaCO, angular blocky brown Sand Stage I gypsum and common snowballs » Gradual boundary 68-94 Strong 7.5YR 5/4 Sandy Highly CaCO, Bky prismatic reddish Loam Prominent Stage I brown gypsum filaments ------► Abrupt boundary and snowballs 94-115 Strong 7.5YR6/4 Sandy prismatic brown Loam Same as above X % c ^Gradual boundary 2Btky E 115-130 Strong long 5YR 5/4 Sandy Same as above - 1 prismatic reddish brown Loam •------► Abrupt boundary 130-165 Strong long 7.5YR 5/4 Sandy Same as above prismatic brown Loam

Diffuse boundary = ;= G B g : 165-180 Strong 5YR6/4 Sandy prismatic It. reddish brown Loam Same as above 1 ► Abrupt boundary 180-230 Strong 7.5YR 5/3 Sandy Highly CaCO, prismatic brown Loam Prominent Stage I gypsum filaments and common snowballs -► Clear but not abrupt boundary Æ 230-260 Strong 5YR 5/4 Sandy Highly CaCO, prismatic reddish brown Loam Stage I gypsum filaments and —► Abrupt boundary incipient Stage II 260-305 Strong 7.5YR 5/4 Sandy Highly CaCO, Z=3< prismatic brown Loam Prominent Stage I to angular gypsum and some blocky snowballs IZJ'J/ . /

Figure 21 : Big Apache Gap soil profile summarizing soil structure, color, texture, and crystal morphology.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 51

y 60

100 0 100 90 80 70 60 50 40 30 20 10 0 Sand Separate, %

Figure 22: Textural diagram for Big Apache Gap profile indicating it is predominantly sandy loam.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 52 Point of Rocks Profile

This profile was sampled in a small exposed arroyo at the edge of a dry playa and

at the distal point of an alluvial fan near Point of Rocks (figure 23). This profile was

described to a depth o f 155 cm. Sanqxles were taken from each horizon based on texture,

color, horizon boundaries, and soil structure (figure 24). Sur&ce lag consists of rhyolitic

pebbles and dominant vegetation includes grass, creosote bush, and mesquite. The upper

100-cm contains 1-5 cm long Stage I gypsum filaments, 1-3 mm in size snowballs, and

gypsum coatings. The lower 50-cm of this profile also contains common large wedge

shaped soil peds coated with gypsum (figure 25).

The upper 22-50 cm of this profile contains 1 -5 cm long Stage I gypsum,

extremely weak Stage II nodules of gypsum were observed in the 50-105 cm range, and

the lower 105-155 cm of this profile contains Stage II and visible lozenge shaped 1-2 cm

long lenticular gypsum crystals. The soil color decreases from light brown in the upper

22 cm of the profile to brown between 22-50 cm then to reddish brown from 50-155 cm.

Texture analyses from this profile indicates the soil is predominantly silty loam (figure

26).

Tularosa Basin

Death March Canvon Profile

This profile was sampled in a large exposed arroyo within the distal end of an

alluvial fan propagating oflf tte western flank of Sierra Blanca (figure 27). This profile

was sampled and described to a depth o f640 cm. Sampling of each horizon was based

on texture, color, horizon boundaries, and soil structure (figures 28-29). This is an

extremely thick profile and contains 9 buried soils. Surface lag consists of igneous

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53

Figure 23: Vertical section of Point o f Rocks Profile showing sampled horizons.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 54

Depth Horizon (cm) Structure Color Texture Morphology Strong Platy 7.5YR 6/4 SUty Highly CaCOj light brown Loam Clear and distinct boundary 2-22 Weak granular 7.5 YR 6/3 Silty Highly CaCO] light brown Loam Rare Stage I ^ Diffuse boundary gypsum 22-50 Strong 7.5 YR 5/4 SUty Highly CaCO] prismatic brown Loam Rare Stage I gypsum filaments incipient Stage II Diffuse boundary nodules

50-105 Moderate 7.5YR 5/4 Silty Highly CaCO] sub-angular reddish Loam Prominent Stage I blocky brown gypsum filaments and Stage II nodules

► Clear boundary

105-155 Large 5.5YR4/4 Silty Highly CaCO] angular reddish Loam Prominent Stage I bloclqr brown gypsum filaments and wedge and Stage II shaped peds nodules

Figure 24: Point of Rocks soil profile summarizing soU structure, color, texture, and crystal morphology.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55

' i

S I

•8 •8 t 1 I VO

I £

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56

100

60 40 sai

am 70

80 20 iam 90 sai 100 0 100 90 80 70 60 50 40 30 20 10 0 Sand Separate, %

Figure 26: Textural digram for Point o f Rocks profile indicating it is predominantly silty loam.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57

I»

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58

Depth Horizon (cm) Structure Color Texture Morphology None 7.5 YR 6/4 Silty loam Highly CaCO, light brown No gypsum > Abrupt boundary 38-83 Well 5 Y R 6 /4 Silty loam Highly CaCO, stratified light reddish brown Rare snowballs

Abrupt boimdary 83-92 Strong 5 YR 5/4 Silty loam Highly CaCO, prismatic to brown Stage I gypsum sub-angular blocky and snowballs *■ Gradual boundary 92-170 Strong 5YR6/3 Silty loam Highly CaCO, 140- prismatic light reddish brown Stage I gypsum snowballs and incipient Stage H ► Diffuse boundary 170-245 Moderate 5 YR6/4 Silty loam Highly CaCO, sub-angular light reddish Strong Stage I blocky brown gypsum grading to Stage n. ► Clear boundary 245-260 Moderate 5 YR 6/4 Silty loam Highly CaCO, prismatic light reddish Rare snowballs brown ► Clear boundary 260-320 Moderate 5YR6/4 Silty loam Highly CaCO, prismatic light reddish Strong incipient Stage brown and snowballs Abrupt boundary 320-341 Strong 5 YR6/4 Silty loam Highly CaCO, prismatic light reddish No gypsum brown ► Clear boundary

341-405 Strong 5 YR 6/4 Silty loam Highly CaCO, sub-angular light reddish Stage I gypsum blocky brown 4 0 0 -

Figure 28: Upper section of Death March Canyon soil profile summarizing the soil structure, color, texture, and crystal morphology.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 59

Depth Horizon (cm) Structure Color Texture Morphology 405-415 Strong 2.5 YR 4/3 Silty loam Highly CaCO, prismatic reddish brown Possible Stage II Abrupt boundary gypsum 415-424 Weak 5YR6/4 Silty loam Highly CaCO, angular light reddish Stage n gypsum blocky brown Vl6Bkyr^ > Abrupt boundary 424-490 Strong 7.5 YR 6/6 Silty loam Highly CaCO, prismatic reddish yellow Strong Stage U gypsum -> Gradual boundary

490-560 Moderate 5 YR 6/6 Silty loam Highly CaCO, prismatic light reddish Strong Stage II brown gypsum

Clear boundary 560-600 Moderate 5 YR 7/4 Silty loam Highly CaCO, prismatic pink Strong Stage II gypsum and snowballs Clear boundary

600-640 Strong 5 YR5/4 Silty loam Highly CaCO, angular reddish Strong Stage II blocky brown to incipient Stage in gypsum Clear boundary and snowballs

Figure 29; Bottom section of Death March canyon soil profile summarizing soil structure, color, and crystal morphology.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 60 pebbles and limestone clasts and the most common vegetation includes grass, creosote

bush, and mesquite.

The upper 92-cm section of this profile contains very little gypsum in the form of

1-3 mm size snowballs. With depth, gypsum content increases, forming 1-3 cm Stage II

nodules between 415-490 cm and eventually forming an incipient Stage 111 petro-gypsic

horizon between 600-640 cm in the lower portion of the profile. Small 1-3 mm vesicles

were very common and pervasive throughout the profile. There were numerous horizons

in this profile containing large 0.5-1 cm re-crystallized gypsum crystals, clay skins,

slickensides and manganese oxide coatings on pebbles suggesting a playa environment.

Large scale cut and fill features were observed in the horizon to the leA of the san^led

surface which contained thick interbedded lenses of sand and gravel Textural analyses

indicate the soil falls in the range of silt to silty loam (figure 30).

Three Rivers Profile

This profile was sampled in an e?qx)sed arroyo within the distal portion o f an

alluvial fan propagating off the western flank of Sierra Blanca (figure 31-32). This profile

described to a depth o f528 cm Each horizon was sampled based on texture, color,

horizon boundaries, and soil structure (figures 33-34). Surface lag consists of igneous

pebbles and limestone clasts, and the most prolific vegetation is grass, creosote bush, and

mesquite.

Common 1-3 mm small vesicles are present throughout the profile and many fine

1-3 cm root traces were coated with gypsum. The upper 130 cm contains abundant 1-3

mm snowballs and 1-5 cm long Stage 1 gypsum filaments and 1-3 cm Stage n gypsum

nodules transitioning to a 30 cm thick incipient Stage 111 gypsum horizon. Abundant

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 61

30 » 70 40 % 60

100 0 100 90 80 70 60 50 40 30 20 10 0 Sand Separate, %

Figure 30; Textural diagram for Death March Canyon profile indicating it is predomoninantly silty loam.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 62

Figure 31 : Upper section of Three Rivers profile showing sampled horizons.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 63

Figure 32: Lower section of Three Rivers profile showing sampled horizons.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 64

Depth Horizon (cm) Structure Color Texture Morphology

0-20 None 10 YR6/4 Silty loam Highly CaCO, 15' pale brown Gypsic coatings \ ^ Gradual boundary 30. 20-63 Moderate 10 YR 5/3 Sandy loam Highly CaCO, 45" sub-angular brown Prominent Stagel blocky and gypsum and 60. platy snowballs ------► Abrupt and Wavy boundary 75- 63-125 Strong 7.5 YR 6/4 Sandy loam Highly CaCO, angular light brown Prominent Stagel 90-4 Bky blocky gypsum and snowballs 105 Abrupt boundary 125-159 Massive to 7.5 YR 5/3 Silty loam Incipient Stage QI strong angular brown gypsum % % r blocky #. Abrupt boundary % 159-179 None 7.5 YR 5/3 Silty loam Highly CaCO, brown Stage I gypsum ► Abrupt boundary 179-184 Strong angular 7.5 YR 6/4 Silty loam Highly CaCO, blocky light brown Stage 1 and Abrupt boundary incipient Stage n 184-208 Weak angular 7.5 YR 6/4 Silty loam gypsum blocky light brown Highly CaCO, m . Stage 1 gypsum 208-213 Strong angular 7.5 YR 6/4 Silty loam blocky light brown Highly CaCO, Abrupt boundary Stage I gypsum 240- 5C 213-229 None 7.5 YR 6/4 Silty loam Highly CaCO, 255' light brown Stage I gypsum Clear boundary and snowballs 270' 229-255 None 7.5 YR 6/4 Sand Highly CaCO, light brown Stage I gypsum 6C g 285. ------► Abrupt boundary 255-305 None 7.5 YR 6/4 Silty loam Highly CaCO, r‘7 T light brown Stage 1 gypsum 3 0 0 - > . 1.1 / /

Figure 33: Upper section of Three Rivers soil profile summarizing soil structure, color, texture, and crystal morphology.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 65

Depth Horizon (cm) Structure Color Texture Morphology r ^ . < * ^ V y . / w 305' ^ » /"%«'•s ^ \ ^ »V

310' *«f 4» %/ V"** » / # • , /% kf ~ — '•%J^ f%^\ \ /-% < ^ » S f % f S 305-373 None 7.5 YR 6/4 Silty loam Highly CaCO, . ^"/ & %/%* ^ ^ f %*" ^ k light brown Stage I gypsum r^ /- •» %^v ✓ V r r% % ^ ^ •W\/% ,*»•' f » %/%4^ \ ✓'^ %^ *f ,0 % • ^90% /-» ^ '• *kV *" s. r %

^ 0'% '.y \ /> <►♦%✓ w -► Abrupt boundary

X7Bticyr> 373-438 None 7.5 YR 6/4 Sandy loam Highly CaCO, light brown Stage I and snowballs. > 0- ^

< < x S -►Abrupt boundary

465" ~y y " V

48( 438-528 None 7.5 YR 6/4 Silt Highly CaCO, light brown No gypsum 495' -7 / 510" V ' 7 z___z_ 525- -' y -r-

Figure 34: Bottom section of Three Rivers soil profile summarizing soil structure, color, texture, and crystal morphology.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 66 Stage I and II gypsum is present below 130 cm, commonly associated with manganese

oxide coatings on 1-3 mm pebbles, rip-up clasts, and rare hard to distinguish mudcracks.

Two distinct laterally consistent charcoal horizons were also present and sampled. The

charcoal horizons are 0.5-2 cm thick and are approximately 100 cm apart in the horizon.

The bottom of the section contains coarse Quaternary age gravel inter bedded with coarse

sand. Textural analyses o f the horizons in this profile indicate the soil is dominantly silty

loam to sandy loam (figure 35).

Soil Profile pH Analyses

All six profiles displayed a similar trend in pH with increasing depth. The upper

A and C horizons of the profiles had a higher pH, pH generally decreased towards the

middle horizons which were usually B horizons, and increased in C horizons of the lower

section of each profile. pH of the 1:1 dilution, thought to most accurately represent the

soil pH, ranged from 7.3 - 9.8 in the sampled profiles. Those horizons containing little or

no gypsum, and which were composed of mostly fluvial unconsolidated sand, produced

the highest pH values in the profiles. All three dilutions produced similar trends in each

sampled profile (figures 36-41), although the pH increased with increasing dilution which

is an expected outcome of this methodology.

A non-linear simple regression function was perfiarmed using Sigma Plot 4.0 to

determine the correlation coefficient (R^) between the dilutions of each horizon to check

the precision of the data collection (appendix 2). Those coefficients closest to 1 indicate

the best correlation (table 2) and most suggested a reasonable amount of correlation

between the diluted samples although there was some discrepancy between some

dilutions.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 67

40 %

100 100 90 80 70 60 50 40 30 20 10 0 Sand Separate, %

Figure 35: Textural diagram for Three Rivers profile indicating it is predominantly silty loam to sandy loam.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 68

0-18 - .-O

18-62 -

62-120 -

120-160 - CL ------^2Btky------

160-175 - o ^ 2Btky

175-213 ------2Bky------

213-240 - 3K

8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 9.0 9.1 9.2 9.3 9.4 pH —• — 1:1 Dilution vs Depth o - 1:2 Dilution vs Depth —V— 1:5 Dilution vs Depth

Figure 36: Dilutions of Barbee Profile pH versus depth exhibiting a similar trend.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 69

..O

" C A2 68-94 - 115-94 - - ^ : : - ^ 2 A y S 'Hd 15-130 '------^ ------2Btky & 30-165 - 6 V 3Ay Q \ 165-180 - — ^ ------^ ------3Bky 180-230 - ...ô 4Ay 230-260 ------4Btky

260-305 - 5Aky

8.7 8.8 8.9 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 pH —• — 1:1 Dilution vs Depth O- 1:2 Dilution vs Depth —V— 1:5 Dilution vs Depth

Figure 37: Dilutions o f Big Apache Gap Profile pH versus depth showing a similar trend.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 70

12-50

H. 50-90 -

^ 90-108 -

108-158 -

158-215 -

215-255 -

8.5 8.6 8.7 8.8 8.9 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8

-#— 1:1 Dilution vs Depth o - 1:2 Dilution vs Depth -V — 1:5 Dilution vs Depth

Figure 38; Dilutions of Dead Cow Grama pH versus depth showing a similar trend.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 71

38-83 83-92 92-170 170-245 245-260 3 260-320 2By4 a 320-341 (g 341-405 405-415 415-424 424-490 490-560 560-600 600-640

-1 ------1------1------1------1------r .1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8. pH 1:1 Dilution vs Depth ■O' 1:2 Dilution vs Depth 1:5 Dilution vs Depth

Figure 39: Dilutions of Death March Canyon pH versus depth showing a similar trend.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 72

2-22 - .O A

22-50 - By

Q, 2 By50-105 - -e - - y l------2By50-105

3B ty105-155 - 3Bty105-155

8.3 8.4 8.5 8.6 8.7 8.8 8.9 9.0 9.1 9.2 9.3 pH -#— 1:1 Dilution vs Depth -o - 1:2 Dilution vs Depth -V— 1:5 Dilution vs Depth

Figure 40: Dilutions of Point of Rocks pH versus depth showing a similar trend.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73

0-20 - C 20-63 - Ay 63-125 - Bky 125-159 ^ Bkym ^ 159-179 - 2 C ______179-184 - 3 B tk y ------■S 184-208 - 4C1 Q 208-213 - 4C2 - V - 213-229 - 4C3 229-255 - 5C 255-373 - 6 C 1 ------373-438 - 6 C 2 ____ ^ 7Btky 438-528 - 8C “r 8.7 8.8 8.9 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 pH -#— 1:1 Dilution vs Depth -O 1:2 Dilution vs Depth -V — 1:5 Dilution vs Depth

Figure 41 : Dilutions of Three Rivers Profile pH versus depth showing similar trend.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 74 Table 2: Summary of correlation coefficients between pH trend lines.

R of dilution R" o f dilution R^ of dilution Soil Profile 1:1 versus 1:2 1:2 versus 1:5 1:1 versus 1:5 Barbee .64 .74 .22

Dead Cow Grama .69 .91 .88

Big Apache Gap .053 .25 .32

Point o f Rocks .95 .80 .80

fhree Rivers .49 .93 .57

Death March .71 .34 .27

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 4

PEDOGENIC CRYSTAL MORPHOLOGY RESULTS

Pedogenic Gypsum Macromorphology

Field observations in the Jornada and Tularosa basins indicate pedogenic gypsum

displays a similar soil morphology to calcium carbonate (figure 42). Pedogenic calcium

carbonate precipitates as Stage I filaments and coatings. Stage II nodules, and as an

indurated Stage HI horizon. However, gypsum exhibits a fourth soil morphology which

calcium carbonate does not display. Gypsum precipitates as small spherical "snowballs"

which displace the soil matrix in a similar fashion to Stage I filaments. Four distinct soil

morphologies for pedogenic gypsum were described: (1) snowballs [figure 43], (2) Stage

I filaments [figure 44], (3) Stage II nodules o f gypsum, and (4) Stage II to incipient Stage

III [figure 45].

Snowball Morphology

Snowballs of gypsum occurred as small 0.5-1 mm white powdery spheres that are

soft and easily powdered between two fingers. They are extremely common throughout

all soil profiles, and are found precipitating in a variety of soil textures. The occurrence

of this morphology decreases with depth, gradually transitioning into Stage 1 filaments

and Stage II nodules of gypsum. Under a stereomicroscope this morphology exhibits a

fibrous texture (figure 46) and occurs as thin coatings on pebbles and filling root traces

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 76

Calcium Carbonate Morphology Stage I filaments Stage H nodules Stage in massive and and coatings indurated.

lü T

* 1 s

''s''''

s " " / s S S - s

Jncreasing Age

Gypsum Morphology

Stage I Stage I Stage II nodules. Stage in massive filaments and “snowballs’’ and indurated. coatings Figure 42: Similarity in carbonate and gypsum macromorphology with increasing age. excluding the exception of the “snowball” morphology observed in Stage I gypsum.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 77

1 ■ÿ\ » . I

*§

Ië 4F:;. a Ca,' ## i

o «

. . m a 1 I 'WW W I

% 1 ## I m

'£I

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 78

Figure 44; Stage I filaments in prismatic structure observed in Big Apache Gap Profile.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 80

Field of view: 1 mm

BAG 180-230: Stage I fibrous gypsum coating inside of root trace.

Field of view: 2 mm

BP 160-175: Stage I filaments and fibrous gypsum coating interior of root traces.

Figure 46: Stage I gypsum occurs as filaments and as fibrous coatings in root traces and on sand grains.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81 (figure 47). The surfoce of the snowball is granular to sugary in appearance and shows

no preferential orientation (figure 48).

Stage I Gypsum

Stage I gypsum morphology is present as thin coatings on pebbles, root traces,

roots, and as small 1 - 3 mm fibrous filaments. The filaments are oriented vertically and

display a diffuse texture along grain boundaries and appear to be precÿitating along root

traces or burrows (figure 49).

Stage n Gypsum

Stage n gypsum is found as small randomly oriented 2 - 4 cm diffuse nodules.

Numerous buried soils displayed a vertical diffuse morphology indicating the gypsum is

pedogenic. This morphology was observed in Barbee, Dead Cow Grama, Big Apache

Gap, Point o f Rocks, and Death March profiles. It occurred with a sub-angular blocky

soil structure in Dead Cow Grama, Point of Rocks, and Three Rivers profiles. In the Big

Apache Gap, Death March, and Barbee profiles this morphology was predominantly

found occurring in soil with a prismatic structure.

Under a stereomicroscope. Stage II gypsum morphology appears powdery and

contains small sand grains incorporated into the matrix of the nodule (figure 50). Some

nodules exhibit a strong clastic texture associated with these sand grains while others

were less prominently clastic. The sand grains appear to be more concentrated along the

edges of the nodule decreasing in number towards the center. This clastic texture was

less evident as the nodules increased in size and abundance.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 82

Field of view: 2.5 nun

FOR 50-105: Snowball precipitating in well-rounded fluvial sand grains.

Field of view: 1.5 mm

DM 245-260: Snowball precipitating in well rounded sand grains.

Figure 47: Spherical to semi-spherical snowball morphology under a stereomicroscope showing granular, sugary texture. They are found in a variety of soil textures and displace the soil matrix.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 83

Field o f view: 2 mm

DCG 2-12: Snowball precipitating in silty loam soil horizon.

Field o f view: 2 mm

DM 170-245: Snowball precipitating in silty loam soil matrix.

Figure 48: Spherical to semi-spherical snowball morphology under a stereomicroscope showing granular, sugary texture. They are found in a variety of soil textures and displace the soil matrix.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 84

Field o f view; 2 mm»

BP 160-175: Stage I fibrous gypsum coating inside o f root trace.

DCG 50-90: Remnant Stage I filament filling root trace.

Figure 49: Stage I gypsum occurs as filaments and as fibrous coatings in root traces and on sand grains.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 85

Field of view; 1.5 mm

DM 424-490; Clastic Stage II gypsum nodule displacing the soil matix.

Field of view; 1 mm

DM 424-490: Close-up of clastix texture observed in Stage II nodules.

Figure 50: Example of Stage II gypsum nodules observed in the examined soil profiles. Exhibited a clastic texture composed of small sand grains.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86 Stage II to Incipient Stage DI Gypsum

In this study. Stage II to incipient Stage III morphology contained randomly

oriented 2-4 cm difhise nodules in a soil matrix slightly indurated with gypsum. This

morphology was only observed in Three Rivers and Death March profiles. The horizons

containing this morphology were approximately 30 - 60 cm thick and laterally consistent.

The color of the soil containing these horizons was pink in both profiles due to an

increase in soluble salts, predominantly gypsum.

Pedogenic Gypsum Micromorphology

Pedogenic gypsum in soil exhibits a variety o f crystal forms; including lenticular,

microcrystalline, tabular, lath, hexagonal, prismatic, and fibrous, which may represent

different environments of formation (Amit and Yaalon, 1996). It has been suggested this

diversity of crystal morphology is a result of changing microenvironment conditions in

soils over time (Amit and Yaalon, 1996). In this study gypsum was found precipitating

as lenticular, tabular, pseudo-hexagonal, hexagonal, lath, and lenticular crystals. Gypsum

crystals in these soils are dominantly euhedral to subhedral and exhibit a wide variety of

crystal habits. EDS analysis was used to detect the co-existence of abundant sulfur,

oxygen, and calcium (figure 51) to distinguish gypsum from other soil constituents.

Snowball Morphology

SEM analysis of the gypsum snowball morphology (figures 52 - 55)

indicate they are composed of numerous small euhedral gypsum crystals of differing

habits including tabular, pseudo-hexagonal, hexagonal, and lath, supported by an organic

matrix and a variety of bacteria (figures 56 - 59). This morphology contained abundant

amounts of the bacteria actinomycetes. The bacterium occurs as thin fibrous coatings on

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 87

POR 50-105

3R 179-184 Figure 51 : Example EDS images indicating the presence of calcium and sulphur.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 88

BP 18-1: Macro scale view of snowball morphology in Barbee Profile.

•N.,

3R 179-2: Close-up of snowbal” showing numerous smaller euhedral to subhedral gypsum crystals.

Figure 52: "Snowball" morphology SEM photos.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 89

5 0 -' 5 0 ^-1 K, r,-,

DCG 108-1: Macro scale view of snowball morphology in Dead Cow Grama soil profile.

BAG 230-6: Macro scale view of snowball morphology in Big Apache Gap soil profile.

Figure 53; Large scale snowball morphology SEM photos.

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POR 50-2: Surface of snowball morphology in Point of Rocks soil profile.

C uC ( ) ^

1-1 11

POR 50-3: Sub-hedral gypsum crystals on surface of snowball morphology in Point of Rocks soil profile.

Figure 54: Surface of "Snowball" morphology SEM photos.

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POR 50-4: Collection of sub-hedral gypsum crystals on surface of snowball morphology in Point of Rocks soil profile.

POR 50-5: Sub-hedral gypsum crystals and rhombohedral caclite crystals on surface of snowball morphology in Point of Rocks soil profile.

Figure 55: Surface of snowball morphology SEM photos.

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BP 18-14: Root hair coated with small euhedral gypsum crystals in the Barbee soil profile.

POR 50-1: Probable root tubule protruding from soil matrix in the Point of Rocks soil profile.

Figure 56: SEM photos of organic material associated with soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93

BAG 180-2: Close-up of unidentified organic material in root trace found in the Big Apache Gap soi profile.

BAG 180-3: Close-up of unidentified organic material within the root trace in the Big Apache Gap soil profile.

Figure 57: SEM photos of organic material associated with soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 94

BAG 180-4: Close-up of unidentified organic material within the root trace in the Big Apache Gap soil profile.

BAG 180-5: Close-up of unidentified organic material within the root trace in the Big Apache Gap soil profile.

Figure 58: SEM photos of organic material associated with soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 95

POR 22-4: Close-up of unidentified organic material in the Point of Rocks soil profile.

POR 22-5: Close-up of unidentified organic material in the Point of Rocks soil profile.

Figure 59: SEM photos of organic material associated with soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS

Page(s) missing in number only; text follows. Microfilmed as received.

This reproduction is the best copy available.

UMI

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. BP 18-9: Close-up of organic material on the surfae o f the "snowball* morphologyin Barbee soil profile thou^t to be associated with the bacteria actinomycetes.

j: • 0' 'J M . 2 k.' r,-. : -4 = FF

BP 18-10: Close-up of material thought to be related to actinomycetes on surface of snowball in Barbee soil profile.

Figure 61: SEM photos of organic material associated with soil profiles

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BP 18-11 ; Close-up of actinomycetes colony growing on the surface of a snowball in the Barbee soil profile.

BP 18-12: Close-up of actinomycetes colony growing on the surface of a snowball in the Barbee soil profile.

Figure 62: SEM photos of organic material associated with soil profiles.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 99

3R 229-3: Tabular gypsum crystal embedded in soil matrix coated with the bacteria actinomycetes in the Three Rivers Soil profile.

3R 229-4: Close-up of actinomycetes colony in the Three Rivers soil profile.

Figure 63: SEM photos of organic material associated with soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 100 the surface of gypsum crystals and as small donut shaped clusters of bacteria colonies

(figure 60 - 63). These donut sb^*ed features were also found as isolated individuals

throughout the soil matrix containing snowballs. The bacteria actinomycetes, which

occurred as fibrous filaments clinging to the surfoce of some gypsum crystals, were often

attached to the surrounding sand grains and other gypsum crystals. In addition, small

euhedral tabular and pseudo-hexagonal gypsum crystals were observed growing on the

tips of various root hairs (figure 56). Many of the crystal habits described in this study

were exclusively observed within the snowball morphology while others were found

precipitating within the soil matrix. Lenticular and tabular crystals were found within the

snowball morphology as well as in the soil matrix of the profiles, however pseudo-

hexagonal tabular and lath crystals were only found in the snowball matrix.

Lenticular crystals

This was the most common gypsum crystal habit found throughout the examined

soil horizons. They are lozenge, half moon shaped in cross-section (figures 64 - 66) and

resemble a convex lens. They are spar sized, (ranging fi’om 20 - 200 pm), disk shaped

crystals within the snowball morphology, with a strong development of the (111) crystal

face and sometimes (103) crystal fece (Jafarzadeh and Burnham, 1992). They also

precipitate as 0.5-1 mm sized individual crystals in the soil matrix not associated with the

snowball morphology. They commonly grew in a linear fashion, giving rise to the

appearance of Stage 1 gypsum filaments.

Tabular pseudo-hexagonal crystals

These crystals are microspar-sized, (ranging fi-om 4 - 8pm), six-sided crystals

where one edge of the hexagon is longer than the other edge (figure 67). They commonly

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. lot

3R 229-8: Lenticular discoid gypsum crystals di^lacmg soil matrix in Three Rivers soil profile

3R 229-7: Lenticular discoid gypsum crystal displacing soil matrix in Three Rivers soil profile.

Figure 64: Lenticular crystal morphology SEM photos.

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DCG 2-3: Lenticular discoid gypsum crystals filling root trace in Dead Cow Grama soil profile.

Z 0 \- U 1 M u. n

3R 229-2: Lenticular discoid gypsum crystal displacing soil matrix in Three Rivers soil profile.

Figure 65; Lenticular morphology SEM photos.

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BP 18-6; Lenticular discoid gypsum crystal embedded in snowball morphology and surrounded by euhedral crystals in the Barbee soil profile

BP 120-1 ; Collection of lenticular discoid gypsum crystal embedded in the soil matrix in Barbee soil profile.

Figure 66: Lenticular crystal morphology SEM photos.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104

j 2 Mm

BP 18-5: Euhedral pseudo-hexagonal tabular gypsum crystals found on snowball surface in the Barbee soil profile.

BP 18-3: Euhedral hexagonal tabular gypsum crystal found on snowball surface in the Barbee soil profile.

Figure 67: Tabular gypsum crystal morphology SEM photos.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105 occur in clusters of crystals rather than isolated crystals and were only foimd precipitating

in the snowball morphology. This crystal habit is found associated with small amounts

of clay skins, and the bacteria actinomycetes. This bacterium typically forms a thin

fibrous coating on surfoces of crystals.

Tabular hexagonal crystals

These crystals are microspar-sized, (ranging from 10 - 20 pm), hexagonal crystals

(figure 68) that are almost exclusively found in the snowball morphology with one

exception, the Barbee profile. This crystal habit occurs in the soil matrix of the Barbee

profile and is associated with well-developed disk-shaped lenticular crystals. However, it

also occurred in the snowball morphology.

Pseudo-hexagonal lath crystals

These crystals are found precipitating as micrite to microspar-sized, (ranging from

2 - 10pm), six-sided lath shaped crystals elongated to (101) and (111) where one axis of

the hexagon is longer than the other (figure 69). They were found associated with the

bacteria actinomycetes within the snowball morphology. This crystal habit only occurs

in the snowball morphology in the Barbee and Dead Cow Grama Profiles.

Stage 1 gypsum

Stage 1 gypsum occurs as powdery and finely crystalline gypsiun commonly

lining root traces. Lenticular crystals were commonly aligned in a linear fashion

precipitating within root traces giving rise to the appearance of Stage 1 filaments (figure

65).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 106

BP 120-2: Euhedral tabular gypsum crystal within the soil matrix in the Barbee soil profile.

3R 179-3: Euhedral tabular gypsum crystal on surface of snowball in Three Rivers soil profile.

Figure 68: Tabular crystal morphology SEM photos.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107

BP 18-4; Euhedral lath gypsum crystal found on snowball surface in the Barbee soil profile.

k - 1 1*1

BP 18-13: Euhedral psuedo-hexagonal gypsum lath crystal found on surface of snowball in Barbee soil profile.

Figure 69: Lath gypsum crystal morphology SEM photos.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 108 Stage II gypsum

This morphology contains small sand grains incorporated into the matrix of the

nodule. Some nodules exhibited a strong clastic texture associated with these sand grains

while others were less prominent. These sand grains appear to be more concentrated

along the edges of the nodule decreasing in number as you move towards the center of

the nodule. The nodules appear more indurated under a SEM than when observed under

the stereomicroscope.

Pedogenic Carbonate Morphology

Visible pedogenic carbonate is rare throughout the sampled profiles, but is present

in the Point of Rocks, Big Apache Gap, Barbee, and Death March Canyon profiles.

Pedogenic carbonate occurs as spar, microspar, and very rarely as micrite. Pedogenic

carbonate most commonly occurs as spar to micrite-sized fungal hyphae ranging in size

from 8-70 pm (figures 70 - 71). Carbonate also forms spar-sized fibrous needles that

coat the surface of root traces or burrows and sand grains (figure 72). A rare form of

pedogenic carbonate (in the soils of this study) occurs as spar-sized root trace fillings,

most Likely Stage 1 filaments in the 300 - 1000 pm size range (figure 73). The least

common form o f pedogenic carbonate occurs as micrite-sized rhombohedral crystals

ranging from 0.5 -1.5 pm (figure 55).

Additional SEM Images

Additional SEM and fieldwork images are contained on the CD-ROM located in

the back jacket of this thesis.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 109

POR 22-7: CaC03 fungal hyphae in Point of Rocks soil profile.

FOR 22-8: Close-up of internal structure o f CaCOa fungal hyphae in Point of Rocks soil profile. Figure 70: Calcium carbonate morphology in sampled soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 110

BAG 94-2: CaCOs fungal hyphae in Big Apache Gap soil profile.

BAG 180-8: CaCOs fungal hyphae in Big Apache Gap soil profile.

Figure 71 : Calcium carbonate morphology in sampled soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. i l l

DM 85-1 : Fibrous CaCOa needles surrounding root trace or burrow in Death March Canyon soil profile.

BAG 115-2; Fibrous CaCOa needles coating sand grain in Big Apache Gap soil profile.

Figure 72: Calcium carbonate morphology in sampled soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112

5tV',.*Vq m

'HSl^’SL

DM 170-1 : CaCOa filling root trace in Deatti March Canyon soil profile.

DM 85-3; CaCOa filling root trace in Death March Canyon soil profile.

Figure 73: Calcium carbonate morphology in sampled soil profiles .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTERS

GYPSUM HYDRATION WATER ISOTOPIC RESULTS

Introduction

The isotopic composition of the hydration water of gypsum has been suggested to

reflect the isotopic composition of past meteoric water and uhimately represent regional

paleoclimate (Khademi et aL, 1997a; 1997b and Dowuona et aL, 1992). This assumes the

hydration water undergoes little evaporation before precipitation of pedogenic gypsum.

The ô'^O and 5D fractfonation factors between the water of crystallization of gypsum and

the original mother water from which gypsum precipitated was found to be 1.004 for

a'^O and 0.98 for oD (Gonflantini and Fontes, 1963 and Pradhananga and Matsuo,

1985). However, substantial evaporation prior to crystallization would result in an

erroneous isotopic signature that cannot be corrected.

The predominant source of precipitation in the Tularosa and Jornada Basins is

from the Gulf of Mexico during the summer and the Pacific Ocean during the winter.

Water from both sources experiences substantial '*0 depletion; as the water from the

Pacific travels across numerous mountain ranges the heavier isotope preferentially falls

out in precipitation and the water originating in the Gulf of Mexico is substantially

warmer and experiences increased evaporation. However, water from the Pacific travels

a greater distance than water from the Gulf of Mexico and undergoes increased isotopic

113

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 114 fractionation and subsequent depletion. Therefore, water from the Pacific is more

depleted than water originating from the Gulf of Mexico.

Isotopic Composition of Gypsum Hydration Water

The S'*0 values of the local meteoric water range from -3.4 to -107oo and the 5D

values ranged from -12.9 to -63.8 °loo- The ô‘*0 values from the hydration water range

from -7.2 to 17.57ooand the8D values range from -24.9 to -917m,. The mean ô'*0 and

5D values were 10.90 and -48.447m,. The S‘*0 values from the mother water range from

-11.6 to 13.5 7m, and the ÔD values range from -5 to -72.457m,. The mean S‘*0 and SD

values of the mother water were 6.87 and —29.027m,. This data is summarized in table 3.

Table 3; Summary of isotopic data for pedogenic gypsum hydration water and its mother water. Source Mean Standard Deviation # of Samples Gypsum Hydration Water ÔD -48.44 16.64 24 5'*0 10.90 5.50 24 Gypsum Mother Water 5D -29.02 16.99 24 ô'*o 6.87 5.49 24

The ô'*0 and ÔD values of the hydration water of gypsum from each soil profile were plotted versus depth and produce a similar isotopic trend (figures 74 - 79). Correlation coefficients between these two trends were produced using a simple regression function in Sigma Plot 4.0 and the results are summarized in table 4. Table 4: Correlation coefficients between 6D and ô‘*0 isotopic values o f pedogenic

Soil Profile Correlation coefficients (r^* Barbee 1.0' Dead Cow Grama 0.63 Point o f Rocks 0.97 Big Apache Gap 0.95 Three Rivers 0.28 Death March Canyon 0.81 ♦This perfect correlation is the result of having only two data points.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115

18-62 - LH

160-175 - EH

-100 -95 -90 -85 -80 -75 -70 -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 8D

18-62 -

160-175 -

10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 5 '*0

Figure 74: Oxygen and hydrogen isotopes plotted versus depth in Barbee soil profile producing a similar trend.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. r = 0.95

68-94 - LH

115-130 - MH

a .

130-165 - EH

180-230 - LP

-100-95-90-85-80-75-70-65-60-55-50-45-40-35-30-25-20-15-10 -5 0 5 10 15 20 5D

68-94 - LH

115-130 - MH a .

130-165 - EH

180-230 - LP

-10 5 0 5 10 15 20 Ô ‘*o

Figure 75: Oxygen and hydrogen isotope values plotted versus depth in Big Apache Gap soil profile exhibiting a similar trend (r^ between two trends is shown on upper plot).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117

r = 0.63

2-12 - EH

12-50 - EH o.

50-90 - LP

108-158 - LP

-100 -95 -90 -85 -80 -75 -70 -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 ÔD

2-12 - EH

12-50 - EH

50-90 - LP

108-158 - LP

10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 6 '*0 Figure 76: Oxygen and hydrogen isotopes values plotted versus depth from Dead Cow Grama profile (r^ between two trends is shown in upper plot).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118

83-92 - LH

320-341 - LP? a.

341-405 -

405-415 - LP?

-100 -95 -90 -85 -80 -75 -70 -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 ÔD

83-92 - LH

320-341 - LP? cu

341-405 - LP?

405-415 - LP?

10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 8 '*0

Figure 77: Oxygen and hydrogen isotopes plotted versus depth from Death March Canyon (r^ between two trends is shown in upper plot).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 119 r = 0.97

22-50 - EH

50-105 - EH

105-155 - LP

-100 -90 -80 -70 -60-50 -40 -30 -20 5 D

22-50 - EH

50-105 - EH

105-155 - LP

-10 -5 0 510 15 20 Ô '*o Figure 78: Oxygen and hydrogen isotopes plotted versus depth in Point of Rocks soil profile producing a similar trend (r^ between two trends is shown in upper plot).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 120 r = 0.28

20-63 -

63-125 -

125-159 -

I 184-208 -

208-213 -

255-351 -

-100 -90 -80 -70-60 -50 -40 -30 -20 ÔD

20-63 -

63-125 -

125-159 - Q.

184-208 -

208-213 -

255-351 -

2 4 6 8 10 12 14 16 18 20-10 - 8 - 6 - 4 0 2 4 6 8 10 12 14 16 18 20-10 ô '*o Figure 79: Oxygen and hydrogen isotopes plotted versus depth in ThreeRivers soil profile producing a similar trend (r2 between two trends is shown in uppper plot).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 121 While the trends between ô'*0 and 5D of the hydration water of gypsum are

similar within the same profile, the ô'*0 and 8D trends between differing soil profiles are

highly variable. Both the mother water line and the hydration water line were plotted

using a best fit simple regression fiinction which produced a correlation equation ofôD =

2.44 ô’*0 - 46.1 for the mother water line and ÔD = 2.39 ô'*0 - 74.5 for the hydration

water line (figure 80). These slopes are consistent with previous research that found

slopes o f 2.5 to 4 characteristic o f arid regions (So for, 1978).

A local meteoric water line was plotted with the isotopic values of the surface

and precipitation waters using a best fit linear regression function producing a correlation

equation of ÔD = 7.22 5**0 — 8.13. The hydration water line and mother water line, as

well as the isotopic values fi’om the hydration water of gypsum, plot well below the local

and global meteoric water lines (figure 81).

The 5**0 and 5 D values were separated into three age categories: Late

Pleistocene, Early Holocene, and Middle to Late Holocene. When these values were

plotted by their corresponding age, they overlapped and showed no apparent trend or

distinct isotopic signature based on depth in the soil profile or with age (figure 82).

The only consistent trend in the data is that the hydration water of gypsum is always

enriched in heavier isotopes in relation to the mother water fi’om which the gypsum was

derived. This is an expected correlation that results fi'om isotopic fi-actionation during

evaporation.

The isotopic values of the hydration water of gypsum are summarized in appendix

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 122

-20 -

-40 - a to -60 -

5 ‘°0 Gypsum vs 8 D of -80 - gypsum hydration water 5 '*0 Gypsum vs 8 D of water o f crystallization -100 “I— -15 15 20

-20 -

-40 -

-60 -

-80 -

15 -10 -5 10 15 20

Dead Cow Grama a Barbee Profile = Point of Rocks O Meteoric Water Big Apache Gap ■ Three Rivers ■ Death March

Figure 80: Isotopic values o f local meteoric water plotted with isotopic values of the hydration water o f gypsum indicating abundant evaporation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 123

-70 - -80 - -90 - ■ Global Meteoric Water Line 5D: = 85 O - 10 00 - ■ Local Meteoric Water Line: 6D = 7.225 " o - 8.13 ■ Hydration Water Line: 6D = 2.395**0 - 74.5 Water of Ciystallization Line SD = 85 0-10

5**0

Figure 81; Comparison o f 5**0 and ôD values from hydration water of g>psuiTL water o f crystallization, local meteoric water, and global meteoric water illustrating abundant evaporation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 124

-20

-30 4

-40

-50

to -60 -I

-70

-80

-90 - Late to Middle Holocene SD versus 5 '*0 Early Holocene SD versus 6 '*0 Late Pleistocene SD versus Ô '*0 ■100 —I— -10 -5 0 10 15 20 Ô '*o

Figure 82: Oxygen and deuterium values plotted according to relative age constraints.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 6

DISCUSSION

Soil Profile Relative Age Constraints

Relative age constraints were interpreted using degree o f soil development,

gypsum and carbonate morphology, and clay content of the sampled soil profiles. As

weU as comparing soil development relative to soils fi'om the Jornada and Hueco basins

that are well described and dated.

Point o f Rocks

The upper 22 cm of this profile is interpreted as being Holocene in age since it

contains very little clay, a platy and granular soil structure, very weak Stage I gypsum

development, and still retained abundant roots. There is a diffuse boundary at 22 cm

between granular and prismatic soil structure suggesting stability rather than erosion.

The horizons between 22-105 cm are interpreted as being early Holocene in age because

of increased Stage I gypsum development, moderately developed sub-angular blocky soil

structure, and fewer roots. There is a clear boundary at 105 cm indicating a period of

erosion between the upper 105 cm of soil and the lower 50 cm and supporting the

interpretation that these are two separate buried soils. The bottom 50 cm of the profile

most likely represents a late Pleistocene-aged playa since it contains distinct Stage I

filaments and Stage II nodules of gypsum, some clay skins, and a large angular blocky

125

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 126 soil structure that is well developed. This horizon contains large (-1-2 m) wedge shaped

peds (figure 25), also supporting the hypothesis of an alternating wet and dry playa

environment for the lower 50 cm of this profile.

Dead Cow Grama

The upper 50 cm of this profile contains well developed soil structure, some clay

skins, and Stage I gypsum morphology suggesting this section of the profile is early

Holocene in age. There is a gradual boundary at 50 cm supporting the inference that the

upper 4 horizons are genetic and part of the same buried soil. From 50-158 cm the soil

exhibited a strong prismatic to sub-angular blocky structure, roots and root traces

decreased in occurrence, and contained strong Stage I gypsum development and is

interpreted to be late Pleistocene in age. There is a clear boundary at 158 cm, indicating

a period of erosion or hiatus in sedimentation, supporting the interpretation o f two buried

soils in this profile. The horizons below 158 cm contain coarse Rio Grande pebbles,

strong Stage I filaments and common Stage II nodules, which correlates to the Camp

Rice Formation previously described in the Jornada Basin and is therefore interpreted as

being Plio-Pliestocene in age (Nfeick et aL, 1993).

Barbee Profile

The upper 18-cm of this profile is composed of unstratified sand and is interpreted

as being historic blowsand suggesting an age of 100-150 years BP. There is a distinct

boundary at 18 cm, which is expected because of the young age of the overlying

sediment. The A and B horizons between 18 and 120 cm are interpreted as being early

Holocene in age. They contain a well-developed strong sub-angular blocky soil structure,

few clay skins, and Stage I gypsum filaments and coatings. There is an abrupt boundary

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 127 at 120 cm suggesting a period of erosion and instability separating the upper two A

horizons from the three B horizons between 120-175 cm These horizons, (from 120 to

175 cm), contain strong prismatic to sub-angular blocky soil structure, strong Stage I

gypsum morphology, few clay skins, and they are interpreted as being latest Pleistocene

in age. There is another abrupt boundary at 213 cm, again indicating a hiatus in

sedimentation and/or erosion coupled with instability. This also supports the

interpretation of three distinct buried soils within this profile. The lower section of this

profile below 213 cm is interpreted as middle to late Pleistocene in age because o f the

presence of strong sub-angular blocky to massive soil structure development, and the

presence of Stage II to incipient Stage HI gypsum development at the base of the profile.

However, gypsum may precipitate more quickly than carbonate since it is more soluble

and most likely transported per descensum at a faster rate into the subsoil. The abundant

source of gypsiferous material in this region may result in the formation of indurated

gypsic horizons at a faster rate than carbonate and thus prove to be less correlative than

thought. However, the factors governing the formation of pedogenic gypsum were not

measured in this study and may be related to the influx rate of CaS 04, therefore the

formation of gypsum could be faster or slower than carbonate.

Big Apache Gap

The upper 94 cm of this profile are interpreted as being late Holocene in age

based on the presence of abundant strong Stage I gypsum morphology and well

developed strong sub-angular blocky to prismatic soil structure. There is an abrupt

boundary at 94 cm separating the first buried soil from the second. The horizons between

94 - 130 cm may be middle Holocene in age since those horizons between 130 - 180 are

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 128 thought to be early Holocene in age. This is inferred from the presence of strong

prismatic soil structure, rare clay skins, and an increase in more prominent Stage I

gypsum filaments and snowballs. Thus, those horizons between 94 - 180 cm are bounded

by early and late Holocene age soils. They may represent late Holocene soil

development as well, but due to their stratigraphie position and the presence of an abrupt

boundary at 180 cm, it is likely they are middle Holocene in age. The horizons below

180 cm are likely latest Pleistocene to late Pleistocene in age because of strong well

developed prismatic to angular blocky soil structure development and the presence of

Stage I to incipient Stage II gypsum morphology.

Three Rivers

The upper section of this horizon from 0 - 359 cm, is Holocene in age based upon

the radiocarbon age o f6970 ± 40 years BP from the charcoal horizon that occurs at 359

cm. This section of the profile contains a horizon exhibiting incipient Stage II gypsiun

morphology. The presence of this morphology in a Holocene soil is inconsistent with the

interpretations throughout the other sampled profiles. The close proximity of this profile

to the gypsiferous sand dunes present in White Sands National Monument is interpreted

as the driving force behind this anomaly. This profile most likely receives a higher eolian

and consequently illuvial input of gypsum allowing Stage I and Stage II gypsum to

nucleate in a shorter period of time. This would explain the presence of Stage I and Stage

II gypsum morphology in Holocene aged soils, which are normally associated with early

Holocene to late Pleistocene geomorphic surfaces. The horizons below the charcoal

horizon are interpreted as being latest Pleistocene based on the stratigraphie position of

the charcoal horizon.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 129 Death March

The upper 83-cm of this profile contains unstratified sand, inferred as historic

blowsand, which has been dated at approximately 100-150 years BP in other

investigations but which were not dated in this study (Buck, 1996). Horizons between

83-260 cm are interpreted as being late Holocene to middle Holocene in age based on

moderate prismatic to sub-angular blocky soil structure development, rare clay skins, and

well-developed Stage I gypsum morphology. Those horizons found below 260 cm

contain abundant Stage I and St%e II gypsum morphology, common clay skins, and

strong soil structure development. However, there are no obvious soil characteristics in

these horizons that could be used to categorize them as middle or early Pleistocene in

age, so they are interpreted as late Pleistocene or older.

Soil Profile Characteristics

pH analvses

The trend in pH versus increasing depth displayed by all six soil profiles is

thought to reflect eluvial soil processes. Ail the surface horizons, predominantly A

horizons, had a higher pH, which is likely a result of eolian deposition of Ca^^ ions on the

surface which haven’t yet been flushed or eluviated out of the upper horizons. Those

horizons in the middle section, predominantly lower A and upper B horizons, most likely

represent regions which had experienced eluvial transport carrying the calcium carbonate

and sulfate into the lowermost horizons, which were dominantly B and C horizons, once

again resulting in an increase in soil pH. For example, the upper horizons of the Barbee

profile, which had the highest pH, are composed of a C horizon overlying two A

horizons. The pH gradually decreases with increasing depth through the A horizons to a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 130 depth of 120 cm. A dramatic increase in pH occurs below 120 cm because of the

presence of two B horizons where soluble salts are commonly deposited or precipitate.

The pH drops off again towards the lower section of the second B horizon, which is

likely related to the depth of illuviation. The pH once again increases towards the bottom

of the profile because of the presence of an indurated Stage IQ carbonate horizon. While

this exact scenario is not mirrored in all six profiles, the same processes are thought to be

controlling this fluctuation in pH with increasing depth. However, some abrupt changes

may be a result o f boundary changes between buried soils. This is thought to be the case

in the Three Rivers and Death March profiles

Vesicular texture

The presence of abundant 0.5-1 mm fine roots may be a possible mechanism for

the formation of the extremely common small 0.5-1 vertical root trace/vesicle features

described throughout all six soil profiles. Fine roots may displace the soil followed by

decomposition leaving root traces. SEM analysis showed the presence of small amounts

of organic material clinging to the walls of otherwise empty root traces, suggesting this

may be a plausible explanation (figure 83).

Although this texture resembles a vesicular A horizon (Av), it is unlikely these

features represent vesicular horizons. This texture is found throughout the examined soil

profiles and are not isolated to the upper A horizon. In contrast, Av horizons typically

form below a well developed desert pavement and their formation is favored at shallow

depths in the soil profile (McFaden et al., 1998). The texture described in this study was

not found below any significant desert pavement and development occurred at great

depths.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 131

Field of view: 2 mm

BP 115-130: Clastic soil texture containing abundant vesicles interpreted as root traces. Field of view: 2 mm

BP 260-305: Close-up of abundant root traces, some contain Stage 1 gypsum coatings. Figure 83: Example of vesicular soil texture which is so prevalent in the examined soil profiles. They are interpreted as fine root traces, rather than a true vesicular horizon since they arc so common and pervasive throughout the extent of the soil profiles.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 132 Low clay content

Texture analyses indicate extremely low clay content throughout the sampled

horizons. This is likely attributed to the parent material texture and composition

surroimding the sampled profiles. Those profiles sampled in the Jornada basin were

dominated by fluvial and eolian bqiut from weathered sandstone, gypsum beds, and

igneous rocks outcropping in the Caballo Mountains. The two profiles sampled in the

Tularosa basin were dominated by eolian input from gypsum dunes in White Sands

National Monument and illuvial input from weathered igneous material o f the

Sacramento Mountains. This lack of clay may also be attributed to eolian winnowing of

fine material from the region, in particular clay particles.

The abundance o f gypsum in these horizons may also be responsible for the lack

of clay at depth. Gypsum is significantly more soluble than carbonate and therefore is

more effective at causing clay particles to flocculate and prevent clay from being

illuviated into the profile (Reheis, 1987).

Some horizons did contain minor amounts o f clay, which were probably not taken

into account during the texture analysis procedure. This clay occurred as clay skins or

coatings on sand grains and most likely remained attached to the sand grains during the

procedure producing an underestimate of actual clay content for some profiles.

Implications of Charcoal Horizons

Previous studies have suggested a major climate shift towards increasing aridity

occurred in the southwestern United States between 7,000 and 9,000 years BP (Buck and

Monger, 1998, Buck and Monger, 1999, Buck, 1996, Monger et al., 1998). Stable C ‘^

isotopic analysis, pollen analysis, and soil characteristics support the idea of a more arid

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 133 climate during this time period. Within the Jornada and Tularosa basins this increase in

aridity is thought to result in decreased soil stability and increased sedimentation (Gile,

1966, Buck, 1996, Buck and Monger, 1999). Eolian sedimentation and soil development

on the high plains of Texas and New Mexico has also been linked with an increase in

aridity (Gustavson and Holliday, 1999). It has also been demonstrated that eolian activity

during periods of aridity results in increased sedimentatmn due to soil instability in the

Trucial States o f Great Britain (Stevens, 1969). Therefore it is inferred the charcoal

horizons described in the Three Rivers soil profile, dated at 6970 ± 40 BP, represent

large-scale forest fires associated with this increase in aridity during the Holocene. The

91 cm separating these two horizons may indicate two separate fires that washed off of

the adjacent Sacramento Mountains separated by a period of fluvial sedimentation or it

may represent the same forest fire separated by material washed onto the fon from a

lower elevation than the fire bum. These charcoal horizons are found in soils

predominantly composed of small, rounded sand grains, supporting the idea of fluvial

transport (figure 84). However, it is important to recognize this was not a moist time

period but a period marked by aridity that decreased soil stability facilitating fluvial

sedimentation.

Evidence For Aridity

The prominent cut and fill feature observed in Death March Canyon (figure 85)

may correlate to this period of aridity between 7,000 and 9,000 years BP. The horizons

above this feature are interpreted to be Holocene in age based on soil morphology and the

horizon it is dissecting is interpreted as being late Pleistocene in age also based on soil

morphology. This brackets the event between 5,000-10,000 years BP, which falls within

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NOTE TO USERS

Page(s) missing in number only; text follows. Microfilmed as received.

134

This reproduction is the best copy available.

UMI

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 135

Ia i •8 I tB 1 1 « 1 ! 00Cri

1 u.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 136 the range of this period of increased aridity. Long-term aridity may have decreased the

stability of the soil followed by a season of high rain or one single storm event. The

presence of this cut and fill feature is consistent with other regional evidence for aridity

and increased erosion and sedimentation between 7,000 - 9,000 years BP (Buck, 1996,

Buck and Monger, 1998, Buck et al., 1998, Monger et al., 1998, Buck and Monger,

1999.). Another cut and fill feature is not overlain by Holocene soils and may represent a

later erosional event (figure 86).

These features may also be indicative of periodic sedimentation and soil

formation during the late Pleistocene and Holocene (Gile and Hawley, 1966, Stevens,

1969, and Gustavson and Holliday, 1999). The soil within the channels is predominantly

coarse gravel and displays very little soil development compared with the surrounding

horizons. This suggests a period of stability allowing soil development, followed by

channel erosion. Another period of stability and the development of the Holocene soils

overlying the channel followed this erosion event. The erosional event may have resulted

in the removal of existing soil horizons creating the sharp contact at 320 cm, as well as

causing the entrenchment of the observed cut and fill channels.

Gypsum Morphology

Although most of the soils in southwest New Mexico contain pedogenic

carbonate and exhibit the associated carbonate stages used to establish relative age, the

soils sampled in this study were dominated by gypsum with a similar trend in

morphology with increasing age. As previously discussed, carbonate development is

primarily dependent upon an atmospheric source of Ca^^ (from rainfall). The Tularosa

and Jornada basins receive the necessary input of calcium from rainwater, eolian

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 137

4%-.. „ ' -

'X - * 0 ::

^ %( ■ T < * & * / 1 •> Gl J i t .%

Figure 86: Large scale cut and fill feature in Death March Canyon.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 138 deposition, in-situ weathering of carbonate parent materials and alluvium, and weathering

of calcium silicate parent materials. Therefore, carbonate is expected to be the dominant

morphology in these basins, yet the sampled profiles contain very little carbonate

compared to concentrations of gypsum. The kinetics involved in the sharing o f calcium

ions and the subsequent precipitation of gypsum versus carbonate are poorly understood

and it is unclear why gypsum dominates these soils when carbonate is expected to be the

most prominent morphology. Perhaps the abundant supply of gypsiferous material close

to the sampled profiles may result in a localized dominance of pedogenic gypsum

precipitation and development. The large influx of gypsiferous material may produce a

supersaturated solution with respect to sulfate, which results in the preferential

precipitation of gypsum over carbonate. The overabundance of sulfate ions overwhelms

the system and utilizes the Ca^^ ions preventing carbonate fi^om entering the soil solution

preventing the formation of pedogenic carbonate (Reheis, 1987, Florea and Al-Joumaa,

1998). Carbonate is not absent in these horizons and therefore must precipitate at times,

however the carbonate that is present is poorly developed and concentrated in the upper

horizons with a few exceptions. It has been suggested this lack of CaCO] in the deeper

horizons may be attributed to the presence of a supersaturated solution with respect to

gypsum, which decreases the solubility of CaCOj and ultimately decreases CaCOs

migration (Reheis, 1987, Florea and Al-Joumaa, 1998). This is a result of the common

ion effect in which the solubility of any salt in equilibrium with a saturated solution

decreases if there is an surplus of one if its ionic components present (Krauskopf, 1967

and Reheis, 1987). In the presence o f a supersaturated gypsum solution the solubility o f

gypsum is decreased by a factor of 64 (Reheis, 1987). This supersaturated solution of

gypsum may initially markedly reduce the solubility of carbonate preventing illuviation

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 139 of the carbonate into the lower horizons. This results in a decrease in the precipitation of

calcium carbonate. Therefore, as gypsum continues to accumulate in the soil, calcium

carbonate becomes less mobile and should be confined to the upper horizons.

In this study SEM analysis o f soil gypsum crystals indicate a pedogenic origin

with no evidence of recrystallization or evidence of detrital transport. They are euhedral

to sub-hedral indicating they grew in-situ and haven’t undergone transportation or

relocation. They are randomly oriented throughout the soil profile and displace the soil

matrix, again indicating a pedogenic origin. They do not exhibit any re-crystallization

“rings” associated with re-hydration of anhydrite or simple re-crystallization from

alternating wetting and drying events. There was no evidence of corrosion or jagged

edges at the crystal soil boundary that would suggest dissolution, and there were no signs

of solution pits on the surface of the crystal again attributed to dissolutfon (Jafarzadeh

and Burnham, 1992). This dissolution texture has been described as comb-shaped edge

forms by Tsarevskiy et aL, 1984. The most common gypsum neoformations result in

gypsum crystals occurring as sandy rosette aggregates, gypsic veins, and dominantly

exhibits an irregular prismatic habit (Tsarevskiy et aL, 1984, Stoops et aL, 1977).

Secondary prismatic gypsum crystals are commonly laminated and interbedded with mud

and sand, are fiuctured or corroded, and are relatively large (>1 mm) (Chen, 1997).

Prismatic gypsum crystals were not observed in any of the examined soil profiles and the

crystals which were observed were clean, euhedral to sub-hedraL and relatively small. It

has been suggested that small length/width ratios indicate rapid soil drying and thus rapid

precipitation of carbonate crystals that should be applicable to gypsum crystals

(Chadwick et aL, 1989). However there is not relationship between length to width ratios

throughout the soil

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 140 profiles. The gypsum crystals examined in this study were commonly equal in length and

width and those that did have a small length to width ratio were scattered throughout the

vertical section of the profiles. It is unlikely gypsum precipitates quickly since it is

forming from an evaporating supersaturated solution.

Snowball Morphology

This morphology was omnipresent throughout the examined soil profiles and was

found in varying soil textures. This suggests the precipitation of the snowball

morphology is not dependent upon specific eolian or eluvial processes or soil texture.

However, this morphology was almost always associated with some form of organic

material. The incorporation and abundance of organic matter associated with this

morphology suggests the formation of this specific morphology may rely on the presence

of organic material. This relationship is illustrated by the presence o f gypsum crystals

precipitating on the tips of root hairs (figure 56).Organic material may promote snowball

genesis, acting as a foundation for the gypsum crystals to precipitate on or by creating a

micro-reducing environment that is conducive to gypsum precipitation. The presence of

the bacteria actinomycetes may help support the framework of this morphology by

attaching itself to gypsum crystals and surrounding sand grains. This bacteria may also

be a source for biogenic sulfate, however this was not demonstrated in the study. The

combination of stable organic material and a bacterial framework may provide the

necessary structural support to promote the formation of the snowball morphology.

Stage II gypsum

The clastic texture observed in Stage II nodules is interpreted as a product of slow

gypsum nucléation. As the nodule begins to grow and displace the surroimding soil it

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 141 incorporates dislocated sand grains into the matrix along the edge of the crystal boundary.

The larger nodules examined in this study rarely displayed this clastic texture. This may

be caused by continued growth of the nodule from the inside out or through precipitation

of gypsum in surrounding voids that may eventually overprint the clastic nature of the

smaller more juvenile nodules.

Lenticular Crystal Morphology

Two major processes have been suggested for precipitation of this morphology,

( 1 ) the presence of ion impurities within the soil solution. Le - organic matter, sodhun

chloride, etc. or (2) crystallization in a soil where void space is not limiting crystal

growth (Edinger, 1973 and Eswaran and Gong, 1991). It has been shown that gypsum

crystals may become curved due to the presence of sodium chloride, (which isn’t the case

in this study area), and other inq>urities in the soil (Jaforzadeh and Bumham, 1992).

Lozenge shaped lenticular crystals commonly form under the influence of certain types of

organic material. This inhibits the normal rapid growth perpendicular to the (111) and

(103) crystal faces and promotes slow growth in the (110) and (010) directions by

decreasing nucléation density (Cody, 1979, Cody and Cody, 1988, and Jaiarzadeh and

Bumham, 1992). Therefore, it is interpreted that the high density of lenticular crystals in

the snowball morphology is a result of the high organic content associated with this

morphology.

Previous studies indicate the lenticular habit occurs in Holocene sediments in

three dominant depositional regimes: (1) marginal marine, (2) inland saline lakes and

along the margins and interior of playas, and (3) saline soil environments (Cody, 1979,

Bachhuber, 1992). However the crystals in this study were found in buried soils

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 142 embedded in the soil matrix with no evidence of transportation or secondary re

precipitation. They were common throughout the profiles, and were not isolated to

specific regions of the soil. They were most common in the upper A and B horizons of

the profiles, most likely related to the higher organic content. They were also present in

the lower portions of the profiles. The lack of evidence indicating re-precipitation and

transportation indicates these crystals are indeed pedogenic and grew in-situ in buried

soils rather than precipitating along the margins of saline lakes or wet playas. The high

salinity, highly alkalinity, and abundant organic matter of desert soils provide an

excellent environment for lenticular crystals to precipitate (Cody, 1979).

Tabular Crystal Morphology

It has been suggested that tabular crystals are the first to precipitate in arid soils

and commonly develop into lenticular crystals (Watson, 1985, 1988). Cody (1979) found

a similar relationship in which tabular crystals grown in the presence of organic matter

gradually grew larger and longer commonly developing curved crystal faces. In this

study tabular crystals are commonly found associated with both organic matter and

lenticular crystals, supporting this interpretation.

Lath Crystals

Lath-shaped crystals have also been interpreted as forming in shallow, sulfate-rich

surface waters along the margins of wet playas during desiccation (Bachhuber, 1992 and

Ogniben, 1955). However, the crystals in this study were found in buried soils, exhibited

no evidence of reprecipitation or transportation and were isolated to the snowball

morphology in the Barbee profile. This profile showed no evidence of containing buried

playa sediment, therefore it is highly unlikely they formed in a play a environment.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 143 Isotopic Analysis of Hydration Water of Gypsum

The hydration water of gypsum was collected from bulk sediment samples that

were preheated at <43 “C to remove any remaining soil moisture. This preheating and the

low clay content of the sediment minimize the risk of contamination from modem

meteoric water.

Isotopic analysis of the hydration water of gypsum produced values enriched in

the heavier '*0 and D isotopes. It is expected that the ô‘*0 and SD values should become

more enriched from the Late Pleistocene into the Holocene. Isotopic analysis of

pedogenic carbonate from southern New Mexico, specifically the Hueco basin, has

established a pattern of depletion in the Late Pleistocene with increased enrichment into

the Holocene (Buck, 1996 and Buck and Monger, 1999). However, the isotopic values

measured in the hydration water of pedogenic gypsum are highly enriched with respect to

the heavier isotopes. All of the 0**0 values plot above zero except one that is only

slightly negative. Both the mother water line and the hydration water line plot

significantly below the modem day meteoric water line and produce values greatly

enriched compared to values measured from pedogenic carbonate. This suggests high

evaporation rates prior to gypsum crystallization leading to an erroneous isotopic

signature.

The increased amount of evaporation may be attributed to localized

environmental factors such as: (1) Decreased vegetation cover during drier periods that

would increase the amoimt of direct simlight reaching the groimd surface. This in turn

would increase soil temperature producing a higher amount of evaporation. (2) The

presence of argillic horizons that would impede soil water percolation, and thus increases

evaporation. However this is an unlikely process since very little clay is seen in the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 144 examined soil profiles. While these environmental factors are likely important processes

controlling soil water evaporation, seasonallhy of atmospheric precipitation and

preferential pedogenic precipitation of gypsum during the warmest months most likely

results in the greatest amount of evaporation. Modem day precipitation in southwestem

New Mexico occurs in two seasons, the winter and monsoon seasons. Summer

precipitation usually falls during late August to October while the winter monsoon

precipitation usually occurs during the months of December through February. Summer

precipitation is more enriched in the heavier isotope, specifically during the months of

June and July, than winter precipitation and this relationship could be considered a

plausible explanation for the enriched values measured in the hydration water of gypsum

(figure 87). However, these modem day values are still relatively depleted with respect

to the isotopic signature of the hydration water and are an unlikely so wee for these

enriched values. The ô'*0 values from pedogenic carbonate indicate isotopic depletion

during the late Pleistocene gradually becoming more enriched moving across the

Holocene boundary (Buck and Monger, 1999). Since the isotopic signatwe of pedogenic

carbonate from the late Pleistocene crossing into the Holocene is depleted, the isotopic

signature of the hydration water of gypsum does not accurately represent the isotopic

signatwe of paleo-precipitation.

Pedogenic carbonate in New Mexico is thought to precipitate during the

months of March through May as a result of this winter precipitation (McFadden and

Tinsley, 1985). However, the enriched isotopic values garnered from the hydration water

of gypsum suggest gypsum precipitates later in the season, after imdergoing extensive

evaporation. Therefore, pedogenic gypsum likely precipitates from the same atmospheric

precipitation that arrives dwing the winter monsoon, but doesn’t actually precipitate until

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 145

Month vs 6 ‘*0 1976 Month vs 6 "O 1977 Month vs 5 '*0 1978 Roswell, NM

-10 -

-12 -

-14 Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Month

— Month vs 6 'S3 1976 E j- O - Month vs 5 "O 1977 E ! - V - Month vs5 '* 0 1978 E

Elk,NM

P -10 -

-14 - -16 -

-20 Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Month

Figure 87: Ô ’*0 values of local precipitation collected between 1976-1978 in southern New Mexico showing a distinct enrichment o f the heavier isotope during the summer months. This correlation is a result o f increased evporation and subseqent isotopic fractionation (from Hoy and Gross, 1982).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 146 the months of June through July when surface temperatures and thus soil temperature is

greatest. Mixing between winter precipitation and summer precipitation in the subsurface

is considered to be negligible since infiltration rates should be relatively constant.

The time lag between the actual introduction o f atmospheric water into the

subsurface of the soil and the precipitation of pedogenic gypsum would result in

increased evaporation and an associated enrichment in the 5**0 and SD values. The

extremely high S'*0 and SD values measured in the hydration water of gypsum are likely

a combination of both the localized environmental factors, and this inferred time lag

between rainfall and gypsum precipitation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER?

CONCLUSIONS AND FUTURE RESEARCH

Pedogenic Gypsum Crystal Morphology in the Tularosa and Jornada Basins

Pedogenic gypsum in the Tularosa and Jornada basins exhibits a wide variety of

macro-scale soil morphologies as well as micro-scale crystal habits. It precipitates as

Stage I coatings, filaments, and snowballs. Stage II nodules, and Stage II to incipient

Stage m slightly indurated nodules. Scanning electron microscope analyses indicate it

occurs as euhedral to sub-hedral spar to micrite sized crystals that displace the soil matrix

and show no indication of re-precipitation or transportation.

Such crystals have been described in previous research, however the Stage I

snowball morphology observed throughout the examined soil profiles in this study have

not been previously described. This morphology appears to be genetically linked to the

presence of organic material and other impurities in the soiL This suggests the snowball

morphology is fairly young smce organic material deconqmses over time, and is therefore

considered to be a feature of Stage I soil development.

Pedogenic Gypsum as a Paleoclimate Indicator

Contrary to previous research by Dowuona et al., (1992), Khademi et al., (1997a),

which state the 0**0 and ÔD isotopic values fi'om the hydration water o f pedogenic

gypsum were useful in paleoclimatic reconstruction, this study suggests isotopic analysis

of pedogenic gypsum is not an applicable paleoclimatic proxy. This study suggests that 147

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 148 pedogenic gypsum experiences a time lag between the input o f winter rainfall and the

subsequent precipitation of gypsum. Extensive evaporation of surface and soil water

induced by localized environmental factors and this time lag, introduces for too much

error into the S‘*0 and 5D signature to be useful paleoclimate proxies. Future

investigations may be able to quantify the amount of fractionation during this time lag,

however, this would need to be re-calculated if this method were to be employed in

regions with differing precipitation patterns and varying climatic and soil conditions.

Genesis of Pedogenic Calcium Carbonate

The 0**0 and 5D values from pedogenic carbonate have been established as

useful paleoclimate indicators. Pedogenic carbonate is thought to precipitate out of

solution earlier in the spring than gypsum, therefore it is inferred that carbonate formation

is not dependent upon evaporation of a supersaturated solution. Ev^wtranspiration is the

dominant mechanism in removing soil water from the system in regions that are well

vegetated. Thus, precipitation of pedogenic carbonate may coincide with increased

évapotranspiration and pC 02 content as plants increase productivity during the spring.

However, this relationship was not actually demonstrated in this study. This topic will

need further investigation to quantify the effect of pCOz soil content on pedogenic

carbonate precipitation.

Previous research has demonstrated that increased pCO? coupled with the

presence of soluble minerals or dissolved M g^ increases the ionic strength of the

solution and in turn increases the solubility of soil carbonate (Mcfadden and Tinsley,

1985). This suggests there is a limit or threshold of percent gypsum that defines an

increase in solubility versus a depression of solubility that is directly related to pCOz

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 149 values. The lack of pedogenic carbonate, however, in the soils of this study is attributed

to this presence of gypsum. Abundant gypsum may increase the salinity of the soil and

create an environment inhospitable to plant life. Without the necessary pCCb from

plants, gypsum will depress the solubility of carbonate because of the common ion effect.

This will prevent illuviation and subsequent precipitation o f carbonate at depth

(Krauskopf 1967).

Caution should be taken when sampling pedogenic carbonate in soils containing

significant amounts o f gypsum. The presence of gypsum without the presence of

increased levels of pCOz depresses carbonate solubility and that may delay the

precipitation of this mineral, increasing the likelihood of evaporation prior to carbonate

formation. The actual percentage of gypsum that would depress the solubility enough to

cause fractionation was not defined in this study and requires further investigation.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX I

Soil Descriptions

150

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D Q.O C g Q.

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C/) C/) Summary of soil descriptions for Dead Cow Grama and Point of Rocks Profiles

Soil Profile Horizon Texture Color Boundary Structure Gypsum Content Carbonate Content CD ■D8 DCG 0-2 A Silty loam 7.5 YR 6/4 Clear Strong platy None Highly effervescent DCG 2-12 Bky Silty loam 7.5 YR 5/4 Gradual Sub-angular blocky Strong Stage 1 Highly effervescent (O' DCG 12-50 Btky Silty loam 5 YR 5/4 Clear Strong prismatic Coatings and Stage 1 Highly effervescent DCG 50-90 2Btky Silty loam 5 YR 5/4 Diffuse Strong angular blocky Stage ! filaments Highly effervescent DCG 90-108 2Bky Silty loam 5 YR 6/4 Clear Moderate sub-angular blocky Stage 1 filaments Highly effervescent DCG 108-158 3Bky Silt 5 YR 6/4 Clear Moderate sub-angular blocky Coatings and Stage 1 Highly effervescent 3. DCG 158-215 4Bk Silt 7.5 YR 6/4 Clear Weak sub-angular blocky Stagel and II Highly efïervescent 3" Loamy sand 7.5 YR 7/4 None, fluvial sand None Highly effervescent CD DCG 215-255 4C

CD "O O CQ. POR 0-2 A N/A 7.5YR 6/4 Clear Strong platy None Highly effervescent Oa 3 POR 2-22 By Silty loam 7.5YR 6/4 Diffuse Very weak granular Faint Stage 1 coatings Highly effervescent "O Silty loam 7.5YR 5/4 Diffuse Strong prismatic Stage 1 and incipient 11 o POR 22-50 2By Highly effervescent POR 50-105 2By2 Silty loam 7.5YR 5/4 Clear Moderate sub-angular blocky Stage 1 and 11 Highly effervescent POR 105-155 3Bty Silty loam 5.5YR 4/4 Large angular blocky Stage 1 and crystals Highly effervescent Q.CD

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C/) C/) Summai7 of soil descriptions for Three Rivers and Big Apache Gap Profiles Sample Horizon Texture Color Boundary Structure Gypsum Content Carbonate Content 3R ■D8 0-20 C Silty loam 10 YR6/3 Gradual None, well stratified None Highly effervescent 20-63 Ay Sandy loam 10 YR 5/3 Abrupt Moderate sub-angular blocky Stage 1 and snowballs Highly effervescent (O' 63-125 Bky Sandy loam 7.5 YR 6/4 Abrupt Strong angular blocky Stage 1 and snowballs Highly effervescent 125-159 Bkym Silty loam 7.5 R 7/4 Abrupt Massive to angular blocky Incipient Stage 111 Highly effervescent 159-179 2C Silty loam 10 YR 7/4 Abrupt None, well stratified Rare Stage 1 Highly effervescent 179-184 3 Btky Silty loam 7.5 YR6/4 Abrupt Strong angular blocky Stage 1 and 11 Higlily effervescent 3. 184-208 4C1 Silty loam 7.5 YR 6/4 Abrupt Weak angular blocky Rare Stage 1 Highly effervescent 3" CD 208-213 4C2 Silty loam 7.5 YR 6/4 Abrupt Strong angular blocky Stage 1 Highly effervescent 213-229 4C3 Silty loam 7.5 YR6/4 Clear None, well stratified Stage I and snowballs Highly effervescent CD ■D Sand 7.5 YR6/4 Abrupt None, well stratified Stage I Highly effervescent O 229-255 5C Q. 255-373 6C1 Silty loam 7.5 YR 6/4 Abrupt None, well stratified Stage 1 Highly effervescent C Sandy loam 7.5 YR6/4 Abrupt None, well stratified Stage 1 Highly effervescent Oa 373-438 7 Btky 3 438-528 8C Silty loam 7.5 YR 6/4 Clear None, coarse gravels None Highly effervescent ■D O BAG CD 0-6 A Sandy loam 7.5 YR 6/3 Abrupt Weak platy None Highly effervescent Q. 6-68 A2 Loamy sand 7.5 YR 5/3 Gradual Stong sub-angular blocky Stage 1 and snowballs Highly effervescent 68-94 Bky Sandy loam 7.5 YR 5/4 Abrupt Strong prismatic Stage 1 and snowballs Higlily effervescent 94-115 2Ay Sandy loam 7.5 YR 5/3 Abrupt Strong prismatic Stage 1 and snowballs Highly effervescent ■D CD 115-130 2Btky Sandy loam 5 YR 5/4 Abrupt Strong prismatic Stage I and snowballs Highly effervescent 130-165 3Ay Sandy loam 7.5 YR 5/4 Diffuse Strong long prismatic Stage I and snowballs Highly effervescent (/) (/) 165-180 3Bky Sandy loam 5 YR 6/4 Abrupt Strong prismatic Stage I and snowballs Highly effervescent 180-230 4Ay Sandy loam 7.5 YR 5/3 Clear Strong prismatic Stage I and snowballs Highly effervescent 230-260 4Btky Sandy loam 7.5 YR 6/3 Clear Strong prismatic to blocky Stage 1, II, and snowballs Highly effervescent 260-305 5Aky Sandy loam 7.5 YR6/3 Clear Strong prismatic to blocky Stage 1,11, and snowballs Highly effervescent

Vl IV CD ■ D O Q. C 8 Q.

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C/) Summary of soil descriptions for Barbee Profile and Death March Canyon Profiles 3o" Soil Profile Horizon Texture Color Boundary Structure Gypsum Content Carbonate Content

8 C Silty loam 7.5 YR 6/4 Abrupt None None Highly elTervescent "O BP 0-18 BP 18-62 A Sandy loam 7.5 YR 5/3 Gradual Strong sub-angular blocky Common snowballs Highly elTervescent BP 62-120 By Sandy loam 7.5 YR 6/4 Abrupt Strong sub-angular blocky Stage I and snowballs Highly effervescent BP 120-160 2Btky Sandy loam 5 YR 5/4 Gradual Strong prismatic to blocky Stage 1,11 and snowballs Highly effervescent BP 160-175 2Btky2 Sandy loam 5 YR 5/4 Gradual Very strong prismatic Stage 1,11 and snowballs Highly effervescent BP 175-213 2Bky Sandy loam 7.5 YR 6/4 Abrupt Strong angular blocky Stage I and snowballs Highly effervescent None Highly effervescent 3. BP 213-240 3K Sandy loam 7.5 YR 6/4 Abrupt Massive/indurated 3" CD "OCD O cQ. aO 3 DM 0-38 C N/A 7.5 YR 6/4 Abrupt None, well stratified None Highly effervescent ■D O DM 38-83 C2 Silty loam 5 YR 6/4 Abrupt None, well stratified Rare snowballs Highly effervescent DM 83-92 Btky Silty loam 7.5 YR 5/4 Gradual Strong prismatic Stage I and snowballs Highly effervescent CD 5 YR6/3 Strong prismatic Stage 1,11, and Snowballs Highly effervescent Q. DM 92-170 2Byl Silty loam Diffuse DM 170-245 2By2 Silty loam 5 YR 6/4 Clear Moderate sub-angular blocky Stage 1 and II Highly effervescent DM 245-260 2By3 Silt 5 YR 6/4 Clear Moderate prismatic to blocky Rare snowballs Moderately effervescent DM 260-320 2By4 Silt 5 YR 6/4 Abrupt Moderate prismatic to blocky Incipient Stage 11 Highly effervescent ■D CD DM 320-341 3Btk Silty loam 5 YR 5/4 Clear Strong prismatic None Highly effervescent DM 341-405 3 Bky Silty loam 7.5 YR 7/2 Abrupt Strong sub-angular blocky Stage 1 Highly effervescent C/) DM 405-415 4 Btky Sandy loam 7.5 YR 4/3 Abrupt Strong prismatic Stage 11 Highly effervescent o' 3 DM 415-424 5Bky Silt 5 YR 6/4 Abrupt Weak angular blocky Stagel 1 Very weak DM 424-490 6Bky Silty loam 7.5 YR 6/6 Clear Strong prismatic Strong Stage II Highly effervescent DM 490-560 7Bky Silty loam 5 YR 6/4 Clear Moderately prismatic Strong Stage II Highly effervescent DM 560-600 8Bky Silty loam 7.5 YR 6/4 Clear Moderatley prismatic Strong Stage II Highly effervescent DM 600-640 9Bty Silty loam 7.5 YR6/4 Clear Strong angular blocky Stage 11 and snowballs Highly effervescent

L^>LA APPENDIX 2

pH Data

154

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. pH data for Three Rivers Soil Profile 155 Sample Dilutions D.I. Tap Averages 1:1 1:2 1:5 Water 1:1 1:2 1:5

Three Rivers 0-20 9.21 9.32 9.35 8.3 9.1 9.225 9.34 9.36 9.24 9.36 9.37 8.3 9.1 20-63 9.18 9.24 9.32 8.3 9.1 9.185 9.24 9.31 9.19 9.24 9.3 8.3 9.1 63-125 9.16 9.24 9.31 8.3 9.1 9.15 9.225 9.31 9.14 9.21 9.31 8.3 9.1 125-159 9.11 9.23 9.28 8.3 9.1 9.11 9.22 9.28 9.11 9.21 9.28 8.3 9.1 159-179 9.04 9.22 9.28 8.3 9.1 9.055 9.225 9.28 9.07 9.23 9.27 8.3 9.1 179-184 8.95 9.15 9.24 8.3 9.1 8.955 9.155 9.23 8.96 9.16 9.22 8.3 9.1 184-208 8.81 9.09 9.19 8.3 9.1 8.795 9.09 9.19 8.78 9.09 9.19 8.3 9.1 208-213 8.85 9.14 9.23 8.3 9.1 8.845 9.14 9.23 8.84 9.14 9.23 8.3 9.1 213-229 8.97 9.21 9.26 8.3 9.1 8.94 9.2 9.26 8.91 9.19 9.26 8.3 9.1 229-255 9.09 9.17 9.26 8.3 9.1 9.095 9.16 9.25 9.1 9.15 9.24 8.3 9.1 255-373 9.1 9.26 9.32 8.3 9.1 9.105 9.245 9.32 9.11 9.23 9.32 8.3 9.1 373-438 8.9 9.16 9.29 8.3 9.1 8.88 9.14 9.28 8.86 9.12 9.27 8.3 9.1 438-528 9.23 9.36 9.5 8.64 9.1 9.22 9.355 9.49 9.21 9.35 9.48 8.64 9.1

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. pH data for Point of Rocks and Dead Cow Grama Soil Profiles 156 Sample Dilutions D.I. Tap Averages 1:1 1:2 1:5 Water 1:1 1:2 1:5

Point of Rocks 0-2 N/A 2-22 8.65 9.16 9.38 8.3 9.1 8.625 9.005 9.195 8.6 8.85 9.01 8.3 9.1 22-50 8.47 8.85 9.1 8.3 9.1 8.465 8.705 9.055 8.46 8.56 9.01 8.3 9.1 50-105 8.45 8.62 9.01 8.3 9.1 8.47 8.595 8.995 8.49 8.57 8.98 8.3 9.1 105-155 8.46 8.58 8.84 8.3 9.1 8.425 8.575 8.835 8.39 8.57 8.83 8.3 9.1

Dead Cow Grama 0-2 9.07 9.12 9.39 8.3 9.2 9.06 9.14 9.55 9.05 9.16 9.71 8.3 9.2 2-12 8.91 9.01 9.35 8.3 9.2 8.9 9.02 9.405 8.89 9.03 9.46 8.3 9.2 12-50 8.71 8.96 9.34 8.3 9.2 8.735 8.955 9.37 8.76 8.95 9.4 8.3 9.2 50-90 8.59 8.76 9.14 8.3 9.2 8.58 8.785 9.16 8.57 8.81 9.18 8.3 9.2 90-108 8.58 8.9 9.17 8.3 9.2 8.57 8.92 9.205 8.56 8.94 9.24 8.3 9.2 108-158 8.6 8.93 9.19 8.3 9.2 8.6 8.915 9.205 8.6 8.9 9.22 8.3 9.2 158-215 8.95 9.5 9.68 8.3 9.2 8.97 9.5 9.69 8.99 9.5 9.7 8.3 9.2 215-255 9.11 9.63 9.78 8.3 9.2 9.105 9.645 9.77 9.1 9.66 9.76 8.3 9.2 1

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. pH data for Death March Canyon Soil Profile 157 Sample Dilutions D.I. Tap Averages 1:1 1:2 1:5 Water 1:1 1:2 1:5 Death March

0-38 N/A 38-83 7.82 8.13 8.54 8.4 9.4 7.775 8.135 8.64 7.73 8.14 8.73 8.4 9.4 83-92 7.62 7.81 8.43 8.4 9.4 7.63 7.775 8.43 7.64 7.74 8.42 8.4 9.4 92-170 7.54 7.83 8.32 8.4 9.4 7.535 7.825 8.41 7.53 7.82 8.5 8.4 9.4 170-245 7.41 7.82 8.54 8.4 9.4 7.405 7.815 8.58 7.4 7.81 8.61 8.4 9.4 245-260 7.31 7.8 8.52 8.4 9.4 7.32 7.7 8.58 7.33 7.6 8.63 8.4 9.4 260-320 7.23 7.73 8.63 8.4 9.4 7.285 7.785 8.64 7.34 7.84 8.64 8.4 9.4 320-341 7.62 7.82 8.63 8.4 9.4 7.615 7.665 8.64 7.61 7.51 8.64 8.4 9.4 341-405 7.54 7.91 8.42 8.4 9.4 7.585 7.805 8.52 7.63 7.7 8.62 8.4 9.4 405-415 7.72 7.84 8.41 8.4 9.4 7.715 7.785 8.48 7.71 7.73 8.54 8.4 9.4 415-424 7.51 7.91 8.43 8.4 9.4 7.47 7.915 8.48 7.43 7.92 8.52 8.4 9.4 424-490 7.32 7.71 8.43 8.4 9.4 7.33 7.725 8.48 7.34 7.74 8.53 8.4 9.4 490-560 7.33 7.7 8.44 8.4 9.4 7.335 7.715 8.45 7.34 7.73 8.46 8.4 9.4 560-600 8.11 8.14 8.5 8.4 9.4 8.105 8.17 8.58 8.1 8.2 8.65 8.4 9.4 600-640 8.23 8.31 8.81 8.4 9.4 8.225 8.31 8.83 8.22 8.31 8.84 8.4 9.4

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. pH data for Barbee and Big Apache Gap Soil Profiles 158 Sample Dilutions D.I. Tap Averages 1:1 1:2 1:5 Water 1:1 1:2 1:5 Barbee Profile 0-18 8.77 8.85 9.00 8.30 9.1 8.74 8.83 9.02 8.71 8.80 9.03 8.30 9.1 18-62 8.43 8.57 8.87 8.30 9.1 8.42 8.50 8.84 8.40 8.43 8.81 8.30 9.1 62-120 8.35 8.58 8.82 8.30 9.1 8.36 8.54 8.81 8.37 8.50 8.79 8.30 9.1 120-160 8.63 8.83 9.13 8.30 9.1 8.64 8.82 9.10 8.64 8.80 9.06 8.30 9.1 160-175 8.32 8.64 9.08 8.30 9.1 8.31 8.63 9.04 8.29 8.62 9.00 8.30 9.1 175-213 8.40 8.55 8.99 8.30 9.1 8.38 8.53 8.97 8.36 8.51 8.94 8.30 9.1 213-240 8.53 8.93 9.32 8.30 9.1 8.57 8.92 9.31 8.61 8.90 9.30 8.30 9.1 Big Apache Gap 0-6 9.11 9.29 9.41 8.30 9.1 9.09 9.30 9.43 9.06 9.31 9.45 8.30 9.1 6-68 8.81 9.10 9.22 8.30 9.1 8.79 9.11 9.25 8.77 9.11 9.27 8.30 9.1 68-94 8.76 9.16 9.31 8.30 9.1 8.77 9.17 9.31 8.78 9.18 9.31 8.30 9.1 94-115 8.79 9.28 9.37 8.30 9.1 8.82 9.55 9.38 8.84 9.81 9.39 8.30 9.1 115-130 8.76 9.24 9.38 8.30 9.1 8.78 9.25 9.38 8.80 9.26 9.37 8.30 9.1 130-165 8.79 9.26 9.40 8.30 9.1 8.83 9.25 9.42 8.86 9.24 9.43 8.30 9.1 165-180 8.90 9.30 9.45 8.30 9.1 8.92 9.31 9.47 8.94 9.32 9.48 8.30 9.1 180-230 8.89 9.31 9.50 8.30 9.1 8.92 9.32 9.49 8.94 9.33 9.47 8.30 9.1 230-260 8.80 9.14 9.41 8.30 9.1 8.83 9.14 9.40 8.85 9.14 9.39 8.30 9.1 260-305 8.86 9.11 9.32 8.30 9.1 8.87 9.12 9.33 8.88 9.12 9.34 8.30 9.1

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX 3

Textural Analysis Data

159

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. "OCD O Q. C S Q.

"O CD

C/Î C/) Texture Analysis Data for Barbee Profile Sample Wt(g) Blank HR R1 T1 HR 30s R T R1 T1 4R 1 min R T R1 Tl IR 30 mit R T Rl Tl g/l "C g/1 “C Ç/1 “c g/l “C g/1 "c g/l "C g/1 °C 8 BP 0-18 43.04 10 21 35 21 10 21 30 21 10 21 16 22 10 22 BP 18-62 50.04 10 19 48 19 10 19 44 19 10 19 22 19 10 19 BP 62-120 50.2 11 18 45 18 11 18 40 18 11 18 20 18 11 18 BP 120-160 50.03 10 22.5 40 22.5 10 22.5 36 22.5 10 22.5 18 23 10 23 CD BP 160-175 50.13 10 22.5 49 22.5 10 22.5 38 22.5 10 22.5 17 23 10 23 BP 175-213 50.03 10 22.5 45 22.5 10 22.5 42 22.5 10 22.5 20 23 10 23 3. 3" CD BP 213-240 50.89 10 23.0 39 23.0 10 23.0 35 23.0 10 23.0 20 23 10 23 ■oCD O Q. C a HR 1.5 hr R T R1 Tl HR 24 hr R T Rl Tl 3o "O Ç/I “C g/i “c g/i g/1 "C o BP 0-18 45.02 15 22 10 22 11 20 10 20 BP 18-62 50.04 20 20 10 20 12 22 10 22 CD Q. BP 62-120 50.2 18 19 11 19 13 20 11 20 BP 120-160 50.03 15 23 10 23 12 22.5 10 22.5 BP 160-175 50.13 15 23 10 23 12 22.5 10 22.5 ■D CD BP 175-213 50.03 17 23 10 23 12 22.5 10 22.5

C/) BP 213-240 50.89 16 23 10 23 13 23.0 10 23.0 C/)

Sand Silt Clay Sand Silt Clay (Ç) (g) (g) % % % BP 0-18 20.00 22.04 1 46.47 51.21 2.32 BP 18-62 34.00 14.04 2 67.95 28.06 4.00 BP 62-120 29.00 19.20 2 57.77 38.25 3.98 BP 120-160 26.00 22.03 2 51.97 44.03 4.00 161

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C 8 Q.

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C/) Texture Analysis Data for Big Apache Gap Profile 3o' O Sample Wt (g)^31ank HR Rl Tl HR 30s R T Rl Tl 4R 1 min R T Rl Tl 4R 30 mil R T Rl Tl g/1 °c g/1 “C g/1 “c g/1 “C g/1 "c g/1 "C g/1 “c ■D8 BAG 0-6 51.52 10 23 50 23 10 23 45 23 10 23 26 23 10 23 BAG 6-68 53.71 10 23 54 23 10 23 51 23 10 23 31 23 10 23 BAG 68-94 50.89 10 23 50 23 10 23 46 23 10 23 27 23 10 23 BAG 94-115 52.55 11 20 45 20 11 20 40 20 11 20 18 21 10 21 BAG 115-130 51.63 11 20 45 20 11 20 40 20 11 20 20 21 10 21 3. 3" BAG 130-165 51.08 11 20 50 20 11 20 44 20 11 20 22 21 10 21 CD BAG 165-180 52.64 10 21 50 21 10 21 44 21 10 21 20 22 10 22 ■DCD O BAG 180-230 51.28 10 21 45 21 10 21 41 21 10 21 20 22 10 22 Q. C BAG 230-260 50.71 10 22 48 22 10 22 43 22 10 22 21 22 10 22 Oa BAG 260-305 50.19 10 22 49 22 10 22 44 22 10 22 25 22 10 22 3 ■D O

CD HR 1.5 hr R T Rl Tl HR 24 hr R T Rl Tl Q. g/1 “C g/1 "C g/1 "C g/1 "C BAG 0-6 51.52 22 23 10 23 11 22 10 22 ■D 25 10 23 11 CD BAG 6-68 53.71 23 22 10 22 BAG 68-94 50.89 22 23 10 23 11 22 10 22 C/) C/) BAG 94-115 52.55 16 21 10 21 10 22 10 22 BAG 115-130 51.63 16 21 10 21 10 22 10 22 BAG 130-165 51.08 17 21 10 21 10 22 10 22 BAG 165-180 52.64 16 22 10 23 10 23 10 23 BAG 180-230 51.28 15 22 10 23 11 23 10 23 BAG 230-260 50.71 16 22 10 23 12 22 10 22 BAG 260-305 50.19 19 22 10 23 12 22 10 22 S 7 ] CD ■ D O Q. C 8 Q.

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C/) C/) Texture Analysis Data for Big Apache Gap Profile Sand Silt Clay Sand Silt Clay (g) (g) (g) %%% BAG 0-6 35 15,52 1 67.9 30.1 1.9 "O8 BAG 6-68 41 11.71 1 76.3 21.8 1.9 BAG 68-94 36 13.89 1 70.7 27.3 2.0 BAG 94-115 29 23.55 0 55.2 44.8 0.0 BAG 115-130 29 22.63 0 56.2 43.8 0.0 3 18.08 0 64.6 CD BAG 130-165 33 35.4 0.0 BAG 165-180 34 18.64 0 64.6 35.4 0.0 BAG 180-230 31 19.28 1 60.5 37.6 2.0 3. 3" BAG 230-260 33 15.71 2 65.1 31.0 3.9 CD BAG 260-305 34 14.19 2 67.7 28.3 4.0 "O O Q. C Oa 3 ■D O

CD Q.

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( fi (fi Texture Analysis Data for Dead Cow Grama Profile Wt Blank HR Rl Tl HR 30s R T Rl Tl HR 1 min R T Rl Tl HR 30 mill R T Rl Tl Sample (g) g/1 “c g/1 "c g/1 "c g/1 "c g/1 *'c g/1 “c g/1 "c DCG 0-2 40.04 11 18 31.0 18 11 18 27.0 18 11 18 16 18 11 18 ■O8 DCG 2-12 101.47 10 19 50.0 19 10 19 41.0 19 10 19 20 19 10 19 DCG 12-50 100.03 10 22 59.0 22 10 22 51.0 22 10 22 25 22 10 22 DCG 50-90 100.02 10 22 40.0 22 10 22 35.0 22 10 22 18 22 10 22 DCG 90-108 100.00 10 22 30.0 22 10 22 26.0 22 10 22 17 22 10 22 DCG 108-158 100.13 10 22 25.0 22 10 22 20.0 22 10 22 17 23 10 23 3. 3" DCG 158-215 40.00 10 22 17.0 22 10 22 15.0 22 10 22 13 23 10 23 CD DCG 215-255 40.00 10 22 40.0 22 10 22 37.0 22 10 22 24 23 10 23 TDCD O Q. C HR 1.5 hr R T Rl Tl HR 24 hr R T Rl Tl a "C °C °C "C 3O g/1 g/1 g/1 g/1 "O DCG 0-2 40.04 15.0 19 10 19 13.0 20 11 20 o DCG 2-12 101.47 17.0 20 10 20 11.0 22 10 22 CD Q. DCG 12-50 100.03 20.0 23 10 23 15.0 22 10 22 DCG 50-90 100.02 16.0 22 10 22 12.0 22 10 22 DCG 90-108 100.00 14.0 22 10 22 12.0 22 10 22 "O DCG 108-158 100.13 15.0 23 10 23 12.0 22 10 22 CD DCG 158-215 40.00 12.0 23 10 23 11.5 22 10 22 C/) C/) DCG 215-255 40.00 14.0 23 10 23 11.5 22 10 22 ^and Silt Clay Sand Silt Clay (Ç) (g) (§) % % % DCG 0-2 16.00 21.04 3.0 39.96 52.5 7.5 DCG 2-12 31.00 69.47 1.0 30.55 68.5 1 DCG 12-50 41.00 54.03 5.0 40.99 54.0 5 DCG 50-90 25.00 73.02 2.0 25.00 73.0 2 DCG 90-108 16.00 82.00 2.0 16.00 82.0 2 165

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C/) Texture Analysis Data for Three Rivers Profile o" 3 Sample 31ank HR Rl Tl HR 30s R T Tl HR 1 min R T Rl HR 30 mil T Tl O Wl(§) Rl Tl R Rl g/l “C g/l °C g/l “c g/l “C g/l °c g/l “C g/l “c 3R 0-20 44.27 10 21 35 21 10 21 30 21 10 21 15 21 10 21 8 ■D 3R 20-63 43.98 10 20 44 20 10 20 40 20 10 20 20 20 10 20 3R 63-125 44.31 10 20 40 20 10 20 35 20 10 20 29 20 10 20 3R 125-159 42.78 10 23 24 23 10 23 20 23 10 23 13 23 10 23 3R 159-179 45.06 10 24 20 24 10 24 18 24 10 24 14 24 10 24 3R 179-184 45 10 23 26 23 10 23 23 23 10 23 12 23 10 23 3. 3R 184-208 45.28 10 23 35 23 10 23 26 23 10 23 13 23 10 23 3" CD 3R 208-213 45.01 10 23 25 23 10 23 22 23 10 23 13 23 10 23 ■DCD 3R 213-229 45.68 10 23 29 23 10 23 25 23 10 23 14 23 10 23 O Q. C 3R 229-255 45.62 10 20 55 20 10 20 53 20 10 20 24 20 10 20 aO 3R 255-373 43.29 10 23 29 23 10 23 23 23 10 23 13 23 10 23 3 "D 3R 373-438 48.8 10 21 40 21 10 21 35 21 10 21 21 22 10 22 O 3R 438-528 64.56 10 23 13 24 10 24 13 24 10 24 11 24 10 24

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CD DM 560-600 51.45 10 22 31 22 10 22 24 22 10 22 15 23 10 22 Q. DM 600-640 51.51 10 23 34 22 10 23 30 22 10 21 19 23 10 21

HR 30 min R T Rl Tl HR 24 hr R T Rl Tl ■D CD g/1 "C g/1 "C g/1 “C g/1 “C (/) DM 0-38 DM 38-83 50.74 11 23 10 23 11 23 11 23 DM 83-92 51.2 15 23 10 23 11 23 11 23 DM 92-170 50.15 14 23 10 23 11 23 11 23 DM 170-245 50.3 12 23 10 23 11 23 11 23 DM 245-260 50.55 10 23 10 23 10 23 10 23 DM 260-320 50.15 10 23 10 23 10 23 10 23 DM 320-341 51.25 13 23 10 23 10 23 10 23 VO 7J CD ■ D O Q. C g Q.

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(/) (/) DM 341-405 50.47 13 23 10 23 10 23 10 23 DM 405-415 50.37 20 23 10 23 10 23 10 23 DM 415-424 50.35 11 23 10 23 10 23 10 23 DM 424-490 52.3 13 23 10 23 10 23 10 23 8 ■D DM 490-560 51.1 10 23 10 23 10 23 10 23 CQ' DM 560-600 51.45 13 23 10 23 10 23 10 23 DM 600-640 51.51 14 23 10 23 10 23 10 23 Texture Analysis Data for Death March Canyon Profile Sand Silt Clay Sand Silt Clay 3"3. (g) (Ç) (g) % % % CD DM 0-38 CD ■D DM 38-83 12.00 38.74 0 23.65 76.35 0.00 O CQ. DM 83-92 21.00 30.20 0 41.02 58.98 0.00 a DM 92-170 17.00 33.15 0 33.90 66.10 0.00 3O "O DM 170-245 14.00 36.30 0 27.83 72.17 0.00 o DM 245-260 5.00 45.55 0 9.89 90.11 0.00

CD DM 260-320 8.00 42.15 0 15.95 84.05 0.00 Q. DM 320-341 20.00 31.25 0 39.02 60.98 0.00 DM 341-405 10.00 40.47 0 19.81 80.19 0.00 ■D DM 405-415 28.00 22.37 0 55.59 44.41 0.00 CD DM 415-424 5.00 45.35 0 9.93 90.07 0.00 (/) (/) DM 424-490 15.00 37.30 0 28.68 71.32 0.00 DM 490-560 11.00 40.10 0 21.53 78.47 0.00 DM 560-600 14.00 37.45 0 27.21 72.79 0.00 DM 600-640 20.00 31.51 0 38.83 61.17 0.00

-o s i APPENDIX 4

Hydration Water of Gypsum Isotope Data

171

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Sample Ô2H 6180 5H of 6**0 of Mean ÔH Mean 60 Mean ÔH Mean 6 0 MW MW of MW of MW PPT 8-11-99 -43.4 -7 -48.44 10.90 -29.02 6.87 PPT 6-20-99 -12.9 -3.4 PPT 5-23-99 -22.5 -3.7 PPT 5-24-99 -33.5 -5.9 3RC 5-26-99 -63.8 -10 DCG 50-90 -52 15.6 -32.65 11.55 DCG 2-12 -60.9 8.1 -41.73 4.08 DCG 108-158 -54.3 13.8 -35.00 9.76 DCG 12-50 -26.8 17.5 -6.94 13.45 3 R 208-213 -65.1 12.9 -46.02 8.86 3R 184-208 -57.3 6.7 -38.06 2.69 3R 125-159 -72.4 1.2 -53.47 -2.79 3R 20-63 -61.6 8.2 -42.45 4.18 3R 63-125 -33.4 12.5 -13.67 8.47 3R 255-351 -59.1 13.6 -39.90 9.56 3R 184-208 -57.3 6.7 -38.06 2.69 DM#2 21-85 -53.7 6.4 -34.39 2.39 DM#2 85-95 -44.7 14.2 -25.20 10.16 DM#2 0-21 -37.7 15.7 -18.06 11.65 DM 83-92 -54 10.2 -34.69 6.18 POR 22-50 -24.9 16.7 -5.00 12.65 POR 50-105 -30 10.5 -10.20 6.47 POR 105-155 -91 -7.2 -72.45 -11.16 BAG 130-165 -37.2 12.7 -17.55 8.67 BAG 68-94 -26.5 13.9 -6.63 9.86 BAG 180-230 -57.3 9.5 -38.06 5.48 BAG 115-130 -32.4 12.4 -12.65 8.37 BP 18-62 -42 14.3 -22.45 10.26 BP 160-175 -31 15.5 -11.22 11.45 BP 175-213 jroken BP 213-240 jroken

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John Van Hoesen

Local Address: 1551 Lorilyn Ave Apt#l Las Vegas, NV 89119

Home Address: P.O. Box 26 East Beme, NY 12059

Degrees: Bachelor of Science, Geology, 1993 State University of New York, Albany

Masters of Science, Geoscience University of Nevada, Las Vegas

Special Honors and Awards: Geological Society of America Travel Grant, 2000- Cordilleran Section Meeting Bemada French Geoscience Scholarship, 1999 Geological Society of America Quaternary Geology and Geomorphology Division Howard Mackin Award- Honorable Mention- 1999 UNLV Graduate Research GREAT Assistanship-1999 UNLV Graduate Student Association Grant-Spring 1999 UNLV Graduate Student Association Travel Grant- Fall 1999

Publications: Van Hoesen, J.G., Omdorff, R.L., Saines, M., 2000, A Preliminary Assessment of an Ice Contact Deposit in the Spring Mountains, Nevada, Geological Society of America Abstracts with Programs, Cordilleran Section.

Van Hoesen, J.G., and Buck, B.J., 1999, Crystal Morphology of Pedogenic Gypsum from Buried Soils of Holocene to Late Pleistocene Age in Southwestern New Mexico, Geological Society of America Abstracts with Programs, v.31, no.l.

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Phillip, PJ., Wall, G.R., and Van Hoesen, J., 1999, Metalachlor and its Metabolites in Tile Drain and Stream Runoff in the Canajohairie Creek Watershed, Environmental Science and Technology, v.33, i..20, p.3531-3537.

Thesis Title: Pedogenic Gypsum in Southem New Mexico: Genesis, Morphology, and Stable Isotopic Signature.

Thesis Examining Committee: Chairperson, Dr. Brenda J. Buck., Ph D Committee Member, Dr. Frederick W. Bachhuber, Ph D Committee Member, Dr. Richard L. Omdorff, Ph D Graduate Faculty Representative, Dr. Penny S. Amy, Ph D

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.