Assessing the applicability of isotopic analysis of pedogenic gypsum as a paleoclimate indicator, Southern New Mexico

doi:10.1016/j.jaridenv.2004.03.003

Journal of Arid Environments

Volume 60, Issue 1, January 2005, Pages 99-114

https://doi.org/10.1016/j.jaridenv.2004.03.003 Get rights and content

Abstract

A lack of well preserved paleoclimate indicators coupled with the abundance of gypsic soils in arid and semi-arid regions has stimulated research on using δ¹⁸O and δD isotopic analysis of the hydration water of gypsum to interpret paleoclimate. This study stresses the importance of establishing a pedogenic origin for gypsum crystals prior to isotopic analysis and evaluates the dominant processes controlling the formation of pedogenic gypsum. Isotopic analyses were conducted on the hydration water of pedogenic gypsum (23 samples) and local precipitation and river water (5 samples) in southern New Mexico. The isotopic signature of the hydration water indicates significant enrichment compared to local meteoric water. Evaporation is the driving mechanism by which gypsum accumulates in soils, and it is the dominant process controlling the isotopic fractionation of the hydration water of gypsum. Because the amount of isotopic fractionation during each episode of evaporation through time cannot be quantified, this technique is not suitable as a method to interpret paleoclimate.

Introduction

Gypsic soils are common throughout the world in arid and semi-arid environments (Nettleton et al., 1982; Nettleton, 1991). Gypsum can form in any type of soil parent material. The dominant soil processes governing gypsum formation are primarily the availability of sulfate ions and the lack of sufficient water to remove the soluble gypsum (Buck and Van Hoesen, 2002). Gypsum can accumulate in soils through four processes: (1) in situ weathering of existing parent material (Carter and Inskeep, 1988; Taimeh, 1992), (2) sulfate-enriched precipitation from an oceanic source (Podwojewski and Arnold, 1994), (3) eolian or fluvial input of gypsum or sulfate-rich sediment (Taimeh, 1992; Van Hoesen, 2000; Buck and Van Hoesen, 2002), and (4) in situ oxidation of sulfide minerals (Mermut and Arshad, 1987; Podwojewski and Arnold, 1994). The presence of gypsum in buried soils and/or paleosols may be used to qualitatively evaluate paleo-environmental conditions; however, recent research suggests isotopic analysis of gypsum may provide more quantitative paleoclimate data.

Previous workers suggested that the δ¹⁸O and δD isotopic signatures of the hydration water of gypsum can be used as a quantitative method to interpret paleoclimate (Sofer, 1978; Halas and Krouse, 1982; Dowuona et al., 1992; Khademi et al (1997a), Khademi et al (1997b); Podwojewski and Arnold, 1994). Organic matter and pollen are generally not well-preserved in arid environments. In cases where this is true, this method could be very important for determining paleoclimates. To test the utility of this method, we chose to investigate pedogenic gypsum in an area of southern New Mexico (Fig. 1) in which many previous paleoclimatic studies have been undertaken (e.g., Wells (1966), Wells (1985); Thompson et al., 1980; Gile et al., 1981; Van Devender, 1990; Hall, 1990; Monger et al., 1998; Buck and Monger, 1999). We examined the macro- and micromorphology of pedogenic gypsum and measured the δD and δO¹⁸ of the hydration water of gypsum from buried soils.

Section snippets

Geologic and geomorphic setting

The Jornada and Tularosa basins are located in southern New Mexico (Fig. 1). These basins are north trending grabens separated by the San Andres and Organ Mountains. The sampled areas are located in a region with an arid climate: average daily temperature varies between 13°C and 34°C and average mean annual precipitation is 24 cm.

Compared to the adjacent Jornada and Hueco basins, the Quaternary landscape evolution of the Tularosa Basin is poorly understood. Access to Tularosa Basin is controlled

Pedogenic gypsum in the Jornada and Tularosa basins

Gypsum is present in both surface and buried soils in the Jornada and Tularosa basins. The initial source for this gypsum is primarily the Permian Yeso Formation, which is exposed in both the Caballo and San Andres Mountains (Fig. 1; Mack and Suguio, 1991). Through time, erosion and dissolution of this gypsum has concentrated it into playas and other poorly drained areas in the form of crusts and large selenite crystals in both the Jornada and Tularosa basins. Eolian erosion of these crusts

Factors affecting oxygen and hydrogen isotopes in pedogenic gypsum

Reconstruction of paleoclimate from δ¹⁸O and δD ratios of the hydration water of gypsum (Halas and Krouse, 1982; Dowuona et al., 1992; Podwojewski and Arnold, 1994; Khademi et al (1997a), Khademi et al (1997b)) assumes that 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). Surface water infiltrates the soil and combines with calcium and sulfate ions to

Materials and methods

Six sections exposed in dry arroyos in the Jornada and Tularosa basins were selected based on the presence of modern and buried soils containing visible gypsum. Each site is located in areas with fresh exposures, and the surface was removed to prevent possible contamination by modern surface processes (e.g., case hardening, slope wash). Each profile was described using the methodology outlined by Schoeneberger et al. (1998). Particle size analysis was performed on each horizon using the

Results

SEM analyses of soil samples from the six measured sections found only pedogenic forms of gypsum. The gypsum occurs as euhedral to subhedral spar to micrite size, randomly oriented, lenticular, tabular, pseudo-hexagonal, hexagonal, lath, and lenticular crystals displacing the soil matrix (Van Hoesen, 2000; Buck and Van Hoesen, 2002). No re-crystallization “rings” associated with re-hydration of anhydrite or simple re-crystallization from alternating wetting and drying events were observed. No

Discussion

Field observations made during this study indicate a pedogenic origin for the gypsum in these buried soils (Buck and Van Hoesen, 2002). In addition, the SEM results indicate a pedogenic origin with no evidence of re-crystallization, dissolution, or detrital transport (Buck and Van Hoesen, 2002). Therefore, these gypsum crystals should contain hydration water derived from the meteoric water present at the time of their precipitation in the subsurface (B horizons) of these soils.

The genesis of

Conclusion

Stable isotopic analyses of the hydration water of pedogenic gypsum in this study indicated heavy enrichment in both δD and δO¹⁸, which supports gypsum's formation through evaporation in an arid environment (Sofer, 1978). No isotopic trends with age or depth were observed, however, large (24‰ in δO¹⁸ values; 66‰ in δD values in POR profile) variations were present within individual sections containing buried soils. The stable isotopic signature of the hydration water of pedogenic gypsum cannot

Acknowledgements

This project was supported by a UNLV Graduate Student Association Grant, a Bernada French Geoscience Scholarship, and a UNLV GREAT scholarship. We thank Greg Arehart and Simon Poulson at the University of Nevada, Reno stable isotope laboratory for their invaluable help, Greg Mack, Curtis Monger, and Tim and Dianna Lawton at New Mexico State University for their help in the field, and Marith Reheis, Robyn Howley, and Joy Drohan for reviewing an earlier version of the manuscript.

References (49)

B.J. Buck et al.
Stable isotopes and soil-geomorphology as indicators of Holocene climate change, northern Chihuahuan Desert
Journal of Arid Environments
(1999)
B.J. Buck et al.
Snowball morphology and SEM analysis of pedogenic gypsum, southern New Mexico
Journal of Arid Environments
(2002)
S. Halas et al.
Isotopic abundances of water of crystallization of gypsum from the Miocene evaporite formation, Carpathian Foredeep, Poland
Geochimica et Cosmochimica Acta
(1982)
H. Khademi et al.
Sulfur isotope geochemistry of gypsiferous aridisols from central Iran
Geoderma
(1997)
H. Khademi et al.
Isotopic composition of gypsum hydration water in selected landforms from central Iran
Chemical Geology
(1997)
B. Liu et al.
Stable carbon and oxygen isotopes of pedogenic carbonates, Ajo Mountains, southern Arizonaimplications for paleoenvironmental change
Palaeogeography, Palaeoclimatology, Palaeoecology
(1996)
H.C. Monger et al.
Stable carbon and isotopes in quaternary soil carbonates as indicators of ecogeomorphic changes in the northern Chihuahuan Desert, USA
Geoderma
(1998)
P. Podwojewski et al.
The origin of gypsum in Vertisols in New Caledonia determined by isotopic composition of sulfur
Geoderma
(1994)
Z. Sofer
Isotopic composition of hydration water in gypsum
Geochimica et Cosmochimica Acta
(1978)
R.S. Thompson et al.
Shasta ground sloth (Nothrotheriops shastense Hoffstetter) at Shelter Cave, New Mexicoenvironment, diet, and extinction
Quaternary Research
(1980)

A. Watson

Desert crusts as palaeoenvironmental indicatorsa micropetrographic study of crusts from Tunisia and the central Namib desert

Journal of Arid Environments

(1988)

C. Yapp

D/H variations of meteoric waters in Albuquerque, New Mexico

USA Journal of Hydrology

(1985)

R. Amit et al.

The micromorphology of gypsum and halite in Reg soilsthe Negev desert, Israel

Earth Surface Processes and Landforms

(1996)

R. Amundson et al.

Isotopic evidence for shifts in atmospheric circulation patterns during the late quaternary in mid-North America

Geology

(1996)

T.C. Blair et al.

Quaternary continental stratigraphy, landscape evolution, and application to archeologyJarilla piedmont and Tularosa Graben floor, white sands missile range, New Mexico

Geological Society of America Bulletin

(1990)

Buck, B.J., Kipp Jr., J.M., Monger, H.C., 1998. Eolian stratigraphy of intrabasinal fault depressions in the northern...

B.J. Buck et al.

Artifact distribution and its relationship to microtopographic geomorphic features in an eolian environment, Chihuahuan Desert

Geoarchaeology

(1999)

B.J. Buck et al.

Inverted clast stratigraphy in an eolian archaeological environment

Geoarchaeology

(2002)

B.J. Carter et al.

Accumulation of pedogenic gypsum in western Oklahoma soils

Soil Science Society of America Journal

(1988)

E.T. Cerling

The stable isotopic composition of modern soil carbonate and relationship to climate

Earth and Planetary Science Letters

(1984)

Cerling, T.E., Quade, J., 1993. Stable carbon and oxygen isotopes in soil carbonates. In: Swart, P.K., Lohmann, K.C.,...

H. Craig

Isotopic variations in meteoric waters

Science

(1961)

D. Cole et al.

Influence of atmospheric CO₂ on the decline of C4 plants during the last deglaciation

Nature

(1994)

W. Dansgaard

Stable isotopes in precipitation

Tellus

(1964)

Cited by (14)

Preservation and modification of the isotopic composition (18O/16O and 2H/1H) of structurally-bound hydration water of gypsum (CaSO<inf>4</inf>·2H<inf>2</inf>O) in aqueous solution
2022, Geochimica et Cosmochimica Acta
Citation Excerpt :
The stable isotope compositions of the elements contained in the mineral gypsum (CaSO4 2H2O) have been used to identify the sources of calcium-sulfate and the origin of the water from which the gypsum precipitated (Bath et al., 1987; Blättler and Higgins, 2014; Evans et al., 2015; Chen et al., 2016, among many others). The stable isotopes of the structurally-bound water (δ17O, δ18O and δD, or δ2H) – also called gypsum hydration water (GHW) – have been used to reconstruct the isotopic composition of paleo-lake waters (Hodell et al., 2012; Grauel et al., 2016; Li et al., 2017; Evans et al., 2018; Dixit et al., 2018; Gázquez et al., 2018) and to ascertain the formation mechanisms of marine gypsum deposits (Pierre and Fontes 1978, Evans et al., 2015), pedogenic gypsum in arid regions (Farpoor et al., 2004; Buck and Van Hoesen, 2005), gypsum speleothems in caves (Gázquez et al., 2013; 2017b; 2019; 2020) and hydrothermal gypsum (Bath et al., 1987; Chen et al., 2016; Gázquez et al., 2022). These studies rely on the assumption that water incorporated into the gypsum crystal lattice at the time of mineral precipitation has not been altered following formation and deposition.
Early investigations on stable isotopes (δ¹⁸O and δD) of structurally-bound gypsum (CaSO₄·2H₂O) hydration water (GHW) suggested that soon after gypsum precipitation, its primary isotopic composition could be altered via gypsum re-crystallization or by isotope exchange by diffusion of water into the intact crystals. If this occurs, the use of stable isotopes of GHW as a paleoclimate proxy is compromised. Here we investigated the long-term (up to 6 years) stability of GHW in contact with aqueous solution by conducting isotopic exchange experiments at different temperatures and using varying gypsum grain size. We placed gypsum with known hydration water isotopic composition in ¹⁸O/D-enriched and ¹⁸O/D-depleted aqueous solutions and monitored any change in the stable isotopes of GHW with time. At low temperature (25 °C) and when the solution is in chemical equilibrium with the mineral, GHW preserves its primary isotopic composition after 2 years. In contrast, when the gypsum-solution system is out of chemical equilibrium, the δ¹⁸O_GHW and δD_GHW values are altered, first via gypsum re-crystallization from the solution and later by isotope exchange via diffusion. Importantly, δ¹⁸O_GHW and δD_GHW stabilized after 2 years to values that represent only an 8 % change relative to the original GHW and remain constant during the subsequent 4 years. Our results suggest that at low temperature the effect of isotope exchange on GHW is limited. At higher temperature (65 °C), chemical equilibrium is not attained after 2 years for fine-grained synthetic gypsum (<250 μm) and its isotopic values continues to change. In contrast, the δ¹⁸O_GHW and δD_GHW in experiments using fine-grained natural gypsum at 45 °C stabilized after 1 year and values changed less than 3 % with respect to initial conditions. Experiments with coarser-grained natural gypsum (1–2 mm) at 45 °C did not show measurable isotopic changes of the GHW, indicating the lack of gypsum dissolution/re-crystallization or diffusion isotopic exchange. We conclude that microcrystalline gypsum crystals (<250 μm) are more readily affected by diagenesis resulting from changes in the gypsum saturation state of the solution, whereas larger gypsum crystals are more likely to preserve their original isotopic compositions. Our results indicate that under certain conditions, GHW can preserve the isotopic composition of its parent fluid and provide valuable information about paleoclimate and paleo-hydrologic conditions.
Hydrochemical characteristics and paleoclimate changes recorded from Sugan Lake on the northern boundary of Tibetan Plateau since mid-Holocene
2022, Catena
Citation Excerpt :
Gypsum precipitated in lakes under the conditions of high sulfate radical ion concentration and high evaporation. Therefore, the presence of significant amounts of gypsum in the lake sediments indicated a high rate of evaporation and a low lake-level closed-lake environment (Rhodes et al., 1996; Buck and Van Hoesen, 2002, 2005). Clay minerals have the potential to be used as paleoclimate tracers (Wang et al., 2013b; Zhou and Keeling, 2013; Coimbra, et al., 2021).
The Qaidam Basin, located in the northern Tibetan Plateau, is one of the three largest interior basins in China. It is surrounded by Kunlun, Altun and Qilian mountains with arid climate, sparsely vegetated landscape and a fragile ecological environment. Investigations on Holocene climate variations in this northern part of the Tibetan Plateau are essential for a better understanding of regional climate dynamics. A mid-Holocene sediment record from Sugan Lake in the Qaidam Basin was investigated using the grain size, mineral, total organic matter content (TOC), C:N ratio (C/N) and element analyses. A depth-age model since ∼ 7750 cal a BP had been made based on 8 AMS ¹⁴C data after taking out 2200 years carbon reservoir effect. SO₄^2--type water and sparse terrestrial vegetation with considerable evaporation caused by high temperature during the Holocene Megathermal Maximum were recorded from ca. 7750 to 5800 cal a BP. From 5800 cal a BP, hydrochemical characteristics shifted dramatically to the Cl-type, while aeolian activities intensified concurrently. A higher lake level with low evaporation/precipitation ratio as the result of cool and wet conditions were inferred between 5800 and 3580 cal a BP when the EASM weakened and westerly jet intensified. Colder and drier conditions were recorded probably due to the strengthening of the mid-latitude westerly circulation after 3580 cal a BP. However, the EASM probably prevailed shortly at 3580 ∼ 3000 cal a BP and 1800 ∼ 810 cal a BP, respectively. Cold/dry, cold/wet and cold/dry Little Ice Age fluctuation climate conditions and aeolian activities with risen lake level and diluted water were inferred from 580 to 280 cal a BP.
Isotopic composition of gypsum hydration water in deep Core SG-1, western Qaidam basin (NE Tibetan Plateau), implications for paleoclimatic evolution
2017, Global and Planetary Change
Citation Excerpt :
Khademi et al. (1997) and Farpoor et al. (2004) used the isotopic composition of gypsum hydration water to study the geomorphology in arid regions. Buck and Van Hoesen (2005) found no isotopic trends in pedogenic gypsum in relation to age and/or depth, and concluded that the isotopic composition of gypsum hydration water in sediments can be used as a paleoclimatic indicator. To determine the δ18O and δD of the water from which gypsum in sediment has precipitated, the hydration water is likely to have retained its original isotopic signal and not have undergone isotopic exchange after gypsum deposition (Sofer, 1978).
The oxygen and hydrogen isotopic compositions of gypsum hydration water can be useful for determining the isotopic composition of the original brine from which gypsum precipitated. However, relatively few long-term and continuous records of the stable isotope geochemistry of gypsum hydration water in arid regions have been reported. We measured the δ¹⁸O and δD of primary gypsum hydration water from a 938.5 m-long deep core (SG-1) in the western Qaidam Basin to study the mechanisms that contributed to gypsum formation and to reconstruct potential paleoclimatic change. The measured δ¹⁸O and δD ranged from − 4.21‰ to 8.69‰ and from − 72.77‰ to 49.73‰, respectively. The linear relationship between δ¹⁸O and δD indicates that meteoric water was the original source of the gypsum hydration water. The gradient of 5.39 for the δ¹⁸O and δD plots is lower than that of global meteoric water, suggesting that paleo-lakewater evaporated and became a CaSO₄-rich brine leading to gypsum deposition. The evaporation/precipitation (E/P) ratio played an important role in determining δ¹⁸O and δD. The oscillations noted in the δ¹⁸O and δD of the gypsum hydration water imply that: (a) there was a long-term and stepwise aridification after ~ 2.2 Ma in the western Qaidam Basin; and (b) there were three increasingly dry phases at 2.2–1.2 Ma, 1.2–0.6 Ma, and 0.6–0.1 Ma, with two cold and dry events at ~ 1 Ma and ~ 0.6 Ma. Global cooling, especially during the Mid Pleistocene Climate Transition event (MPT), may have been the primary cause of the aridification recorded in core SG-1 in the Asian inland.
Triple oxygen isotope systematics of structurally bonded water in gypsum
2017, Geochimica et Cosmochimica Acta
Citation Excerpt :
An evaporation line is defined by several samples and can in principle be back extrapolated to the MWL to determine pristine δ18Omw compositions. This is the foundation of several paleoclimate reconstruction studies (Matsubaya and Sakai, 1973; Sofer, 1978; Khademi et al., 1997; Buck and Van Hoesen, 2005; Hodell et al., 2012; Evans et al., 2015). Evaporation at low humidity generally results in a strong kinetic effect and thus shallow evaporation slopes (Craig, 1961; Dansgard, 1964).
The triple oxygen isotopic composition of gypsum mother water (gmw) is recorded in structurally bonded water in gypsum (gsbw). Respective fractionation factors have been determined experimentally for ¹⁸O/¹⁶O and ¹⁷O/¹⁶O. By taking previous experiments into account we suggest using ¹⁸α_gsbw-gmw = 1.0037; ¹⁷α_gsbw-gmw = 1.00195 and θ_gsbw-gmw = 0.5285 as fractionation factors in triple oxygen isotope space.
Recent gypsum was sampled from a series of 10 ponds located in the Salar de Llamara in the Atacama Desert, Chile. Total dissolved solids (TDS) in these ponds show a gradual increase from 23 g/l to 182 g/l that is accompanied by an increase in pond water ¹⁸O/¹⁶O. Gsbw falls on a parallel curve to the ambient water from the saline ponds. The offset is mainly due to the equilibrium fractionation between gsbw and gmw. However, gsbw represents a time integrated signal biased towards times of strong evaporation, hence the estimated gmw comprises elevated ¹⁸O/¹⁶O compositions when compared to pond water samples taken on site. Gypsum precipitation is associated with algae mats in the ponds with lower salinity. No evidence for respective vital effects on the triple oxygen isotopic composition of gypsum hydration water is observed, nor are such effects expected. In principle, the array of δ¹⁸O_gsbw vs. ¹⁷O_excess can be used to: (1) provide information on the degree of evaporation during gypsum formation; (2) estimate pristine meteoric water compositions; and (3) estimate local relative humidity which is the controlling parameter of the slope of the array for simple hydrological situations. In our case study, local mining activities may have decreased deep groundwater recharge, causing a recent change of the local hydrology.
Precise and accurate isotope fractionation factors (α17O, α18O and αD) for water and CaSO<inf>4</inf>·2H<inf>2</inf>O (gypsum)
2017, Geochimica et Cosmochimica Acta
Citation Excerpt :
Gyspum (CaSO4·2H2O) is a common hydrated mineral on Earth and has been recently found to be abundant on Mars (Showstack, 2011; Massé et al., 2012). The oxygen (16O, 17O, 18O) and hydrogen (1H, 2H) isotopes of gypsum hydration water (GHW) provide a rich source of information about the environmental conditions under which gypsum formed (Matsuyaba and Sakai, 1973; Sofer, 1978; Fontes et al., 1979; Halas and Krouse, 1982; Bath et al., 1987; Khademi et al., 1997; Kasprzyk and Jasinska, 1998; Farpoor et al., 2004; Buck and Van Hoesen, 2005; Hodell et al., 2012; Gázquez et al., 2013; Evans et al., 2015; Grauel et al., 2016; Chen et al., 2016, amongst others). Under certain conditions, the isotopic composition of GHW retains the value of the parent solution and is not altered by post-depositional processes.
Gypsum (CaSO₄·2H₂O) is a hydrated mineral containing crystallization water, also known as gypsum hydration water (GHW). We determined isotope fractionation factors (α¹⁷O, α¹⁸O and αD) between GHW and free water of the mother solution in the temperature range from 3 °C to 55 °C at different salinities and precipitation rates. The hydrogen isotope fractionation factor (αD_gypsum-water) increases by 0.0001 units per °C between 3 °C and 55 °C and salinities <150 g/L of NaCl. The αD_gypsum-water is 0.9812 ± 0.0007 at 20 °C, which is in good agreement with previous estimates of 0.981 ± 0.001 at the same temperature. The α¹⁸O_gypsum-water slightly decreases with temperature by 0.00001 per °C, which is not significant over much of the temperature range considered for paleoclimate applications. Between 3 °C and 55 °C, α¹⁸O_gypsum-water averages 1.0035 ± 0.0002. This value is more precise than that reported previously (e.g. 1.0041 ± 0.0004 at 25 °C) and lower than the commonly accepted value of 1.004. We found that NaCl concentrations below 150 g/L do not significantly affect α¹⁸O_gypsum-water, but αD_gypsum-water increases linearly with NaCl concentrations even at relatively low salinities, suggesting a salt correction is necessary for gypsum formed from brines. Unlike oxygen isotopes, the αD_gypsum-water is affected by kinetic effects that increase with gypsum precipitation rate. As expected, the relationship of the fractionation factors for ¹⁷O and ¹⁸O follows the theoretical mass-dependent fractionation on Earth (θ = 0.529 ± 0.001). We provide specific examples of the importance of using the revised fractionation factors when calculating the isotopic composition of the fluids.
Geochemistry of Evaporites and Evolution of Seawater
2014, Treatise on Geochemistry: Second Edition
The chemistry of modern and ancient evaporites, and their parent waters, is reflected in the mineralogy and facies distribution remaining in the geologic record. The evaporation of modern seawater and the order of precipitated salts, as well as the environment in which marine evaporites are deposited, together are the key for the understanding of the fossil record. The chemical evolution of the ocean has influenced the mineralogy of the K–Mg salts, and these changes are recorded in primary fluid inclusions remaining in unaltered halite. This chapter reviews these problematic sediments, describing in detail how the evaporite mineralogy and halite fluid inclusions have been used to estimate the chemical composition of ancient oceans. Here, we present and discuss the evaporite record in the Precambrian as well as the Phanerozoic and the general geologic significance of evaporites.

View all citing articles on Scopus

View full text

Assessing the applicability of isotopic analysis of pedogenic gypsum as a paleoclimate indicator, Southern New Mexico

Abstract

Introduction

Section snippets

Geologic and geomorphic setting

Pedogenic gypsum in the Jornada and Tularosa basins

Factors affecting oxygen and hydrogen isotopes in pedogenic gypsum

Materials and methods

Results

Discussion

Conclusion

Acknowledgements

Journal of Arid Environments

Journal of Arid Environments

Geochimica et Cosmochimica Acta

Geoderma

Chemical Geology

Palaeogeography, Palaeoclimatology, Palaeoecology

Geoderma

Geoderma

Geochimica et Cosmochimica Acta

Quaternary Research

Journal of Arid Environments

USA Journal of Hydrology

The micromorphology of gypsum and halite in Reg soilsthe Negev desert, Israel

Earth Surface Processes and Landforms

Isotopic evidence for shifts in atmospheric circulation patterns during the late quaternary in mid-North America

Geology

Quaternary continental stratigraphy, landscape evolution, and application to archeologyJarilla piedmont and Tularosa Graben floor, white sands missile range, New Mexico

Geological Society of America Bulletin

Artifact distribution and its relationship to microtopographic geomorphic features in an eolian environment, Chihuahuan Desert

Geoarchaeology

Inverted clast stratigraphy in an eolian archaeological environment

Geoarchaeology

Accumulation of pedogenic gypsum in western Oklahoma soils

Soil Science Society of America Journal

The stable isotopic composition of modern soil carbonate and relationship to climate

Earth and Planetary Science Letters

Isotopic variations in meteoric waters

Science

Influence of atmospheric CO2 on the decline of C4 plants during the last deglaciation

Nature

Stable isotopes in precipitation

Tellus

Influence of atmospheric CO₂ on the decline of C4 plants during the last deglaciation