Clay Mineralogical Composition Research Articles

Non-exchangeable potassium release and its removal in foot-hill soils of North-west Himalayas

Abstract In the present investigation, soils representing ten locations and three agro-climatic zones of foot-hills of north-west Himalayas were studied to assess Non-exchangeable Potassium (NEK) reserves, its release and influence of K-fixing capacity and clay minerals on NEK release. Maximum release of non-exchangeable K was obtained in temperate zone soils (295 mg kg− 1) followed by intermediate zone (227 mg kg− 1) and sub-tropical zone soils (106 mg kg− 1), having relative soil quality index (RSQI) values of 85, 80 and 65, respectively. The quantitative analysis of clay minerals, through XRD technique, revealed that the temperate soils have more illite (averaging 62%) which holds well as a reason for high NEK reserves of 1556 mg kg− 1 in these soils in comparison to intermediate (having illite averaging 53%) and sub-tropical (having illite averaging to 49%) soils having NEK amounting to 1022 and 918 mg kg− 1, respectively. In order to study the NEK removal from the soils under investigation, maize was grown as a test crop and potassium was applied through four treatments having four levels of K (0, 15, 30 and 60 mg kg− 1) applied as KCl. The crop demonstrated significant response in terms of dry matter yield up to 30 mg kg− 1 in sub-tropical and intermediate soils while no such response was obtained in temperate soils. The percent NEK removed by maize crop from NEK reserves was 14, 25 and 20% in sub-tropical, intermediate and temperate soils, respectively. The information about NEK release, its removal as well as its relationship with K fixing capacity, clay minerals and RSQI can be used for understanding the K buffering potential of soils especially under adverse soil and climatic conditions that prevail in southwest India. Besides, the regression equations developed can be used for predicting NEK release on the basis of K fixing capacity and clay mineralogical composition.

The effect of irrigation on the content and mineralogical composition of clays in chernozems of Rostov oblast (Bagaevsko-Sadkovskaya Irrigation System)

The content and mineralogical composition of clays in the irrigated and nonirrigated pre-Caucasian chernozems in Rostov oblast were studied by X-ray diffraction analysis. Irrigation caused an increase in the content of this fraction in plow layers. The main changes in the mineralogical composition comprised a decrease in the quantity of illites and increase in labile minerals.

Clay Mineralogical Composition of Representative Paddy Soils in Southern Part of Northeastern Japan

Clay Mineralogical Composition of Representative Paddy Soils in Southern Part of Northeastern Japan

Ceramic behaviour of five Chilean clays which can be used in the manufacture of ceramic tile bodies

This study is focussed on the behaviour of ceramic clays from Chile which has an important local ceramic industry. Five deposits of clays with industrial application have been studied. The clays come from San Vicente de Tagua-Tagua (SVTT), Litueche (L), Las Compañías – Río Elqui (LC), La Herradura – Coquimbo (LH) and Monte Patria – Coquimbo (MP). The chemical and mineralogical compositions of clays were determined by X-ray fluorescence (XRD) and X-ray diffraction (XRD), respectively. Also, the plasticity index (PI) was measured for each sample. The chemical and mineralogical compositions of samples differ considerably. Test samples have been prepared by pressing and firing in the range of 800–1150 °C. Linear contraction (LC), water absorption capacity (WAC) and thermodilatometric analysis (TDA) were done in order to characterize clays after firing. A considerable decrease in the WAC coinciding with the beginning of vitrification, is observed between 1050 and 1100 °C. At 1150 °C the porosity of the tile bodies decreases significantly and the tile bodies became earthenware. All studied clays seem to be easily adaptable to a correct dry pressing ceramic process. In particular, illite–kaolinite-rich samples show the best behaviour. Samples SVTT are suitable for the production of fast firing vitreous pieces. L samples present the highest refractory behaviour.

Soil Development and Fertility Characteristics of Inland Valleys in the Rain Forest Zone of Nigeria: Mineralogical Composition and Particle-Size Distribution

The particle-size distribution and mineralogical composition of the clay (< 2 μm) and fine-sand (0.25–0.10 mm) fractions in soils of two inland valleys in Abakaliki and Bende, Southeast Nigeria, were investigated to provide basic information on soil-forming processes and agricultural potentials. These soils were silty or clayey, deriving from Cretaceous or Tertiary shale materials. The particle-size distribution and its computation on a clay-free basis revealed relatively remarkable lithologic breaks in a couple of pedons. The effect of lithologic discontinuities on soil mineralogical composition was not, however, conspicuous. Petrographic investigation revealed that quartz predominantly comprised the fine-sand fraction in the soils at both study sites. Nevertheless, the clay mineralogical composition of the soils was a mixture of kaolinite, irregularly interstratified smectite-illite intergrades (S/I), hydroxyl-Al interlayered 2:1 type clays (HICs), vermiculite, smectite, halloysite and illite along with fine-sized quartz in Abakaliki. The soils of Bende predominantly contained smectite, which was partially interlayered with hydroxyl-Al and kaolinite. It is suggested that seasonal floodwater has slowed the disintegration of weatherable clay minerals inherited from the shale, while quartz originating from the sandstone is predominant in the fine-sand fraction. Additionally, a possible soil-forming process observed at the both study sites was ferrolysis, which was indicated by a clear decreasing pattern of HICs downward in the soil profiles. The entry of S/I and vertical distribution patterns for a couple of clay minerals in the pedon suggested that the soils in Abakaliki have developed under the significant influence of aeolian dust delivered by the Harmattan. The findings might describe a site-specific deposition pattern of Harmattan dusts as well as hydromorphic soil-forming processes in the wetlands of the inland valleys.

Kaolin in the net-like horizon of laterite in Hubei, south China

AbstractThe clay mineralogy and chemical composition of the white veins, red matrix and both Fe- and Mn-bearing nodules occurring in a laterite profile in Hubei, south China were investigated using X-ray diffraction, scanning electron microscopy equipped with an energy-dispersive spectrometer, and high-resolution transmission electron microscopy. The results show that the mineral components of the red matrix are mainly quartz, kaolinite, halloysite, goethite and minor illite, whereas the white net-like veins contain mostly quartz, kaolinite, halloysite, and illite. In the net-like horizon, the chemical index of alteration (CIA, the ratio of Al2O3/(Al2O3+CaO+K2O+Na2O)) and the TiO2/Al2O3ratio are 89.8% and 0.021 for the white vein and 90.7% and 0.025 for the red matrix, respectively. Both white-vein and red-matrix components have similar TiO2/Al2O3ratios, and are similar to the ratio 0.027 of the unaltered bedrock. The similarity in TiO2/Al2O3values indicates that all three portions of the laterite soil share the same origin. Also, although the white-vein and red-matrix components differ in Fe2O3abundance, the similar CIA values do imply similar degrees of alteration. The Fe-bearing and Mn-bearing nodules were produced by the local accumulation of Fe2O3and MnO, respectively. Halloysite in the weathering profile occurs in two different morphologies, tubular and platy crystals. Tubular halloysite occurs both in the red matrix and the Fe-bearing nodule whereas platy halloysite occurs only in the white vein and Mn-bearing nodule assemblages. Crystallization of small tubular halloysite from Si and Al concretions in the red matrix is observed, indicating that the morphology of these crystals in the weathering environment is mainly controlled by Fe3+cations, whereas platy halloysite may be derived from the hydration of kaolinite.

Stress History Effects on Consolidation and Permeability Behavior of Fine-Grained Soils

Abstract Practical situations wherein the soil is subjected to static stress reversals are many, and in this context, understanding the engineering behavior of soil in the field subjected to such static stress reversals gains importance. The present paper deals with the study of the effect of static cyclic loading on compressibility and permeability behavior of fine-grained soils of different clay mineralogical composition, both in the undisturbed and remolded states. The static stress reversals enable the soils to reach a “near equilibrium state” in terms of volume change, whether the soil is initially in the undisturbed state or in the remolded state. The stress history of a soil has been shown to have definite influence on the coefficient of consolidation and permeability of fine-grained soils. Soil clay mineralogy has been observed to control the nature of variation of the behavior of soils subjected to static stress reversals.

Variáveis de acidez em função da mineralogia da fração argila do solo

A acidez do solo e variáveis associadas são muito importantes nos manejos dos solos, especialmente nas regiões tropicais e subtropicais. Com o objetivo de estudar algumas variáveis da acidez do solo e verificar a influência da mineralogia da fração argila sobre a relação entre pH em CaCl2 e grau de saturação por bases (V), amostraram-se os horizontes B e C de diferentes classes de solo no Estado do Paraná: Latossolo Bruno ácrico húmico (LBw-1), Latossolo Bruno distrófico húmico (LBw-2), Latossolo Vermelho distroférrico húmico (LVdf), Cambissolo Háplico alumínico típico (CXa) e Cambissolo Húmico distroférrico típico (CHd). A fração argila foi estudada por difratometria de raios X, análise termodiferencial, análise termogravimétrica e análises químicas. As amostras de solo foram incubadas por 60 dias, após terem recebido doses crescentes de óxido de cálcio, para atingir valores preestabelecidos do grau de saturação por bases (natural, 25, 45, 60, 70, 125 e 150 %). Em seguida, determinaram-se os teores de cátions trocáveis e os valores de pH em H2O e solução de CaCl2 1 mol L-1. Os solos apresentaram o seguinte comportamento quanto à mineralogia da fração argila: mais esmectítico/vermiculítico - CXa; mais oxídico, principalmente óxidos de Fe - LVdf e óxidos de Al - LBw1; mais caulinítico, com menores teores de óxidos de Fe e Al - CHd e LBw2. Essa diversidade mineralógica foi determinante na relação pH em CaCl2 e grau de saturação por bases (V) dos solos. As curvas que mostraram essa relação foram não lineares, o que significa poder tamponante diferenciado ao longo da faixa de pH em CaCl2 estudada; formato convexo dos solos mais oxídicos e côncavo dos solos cauliníticos e com argila 2:1. O formato convexo das curvas foi conseqüência da formação de cargas negativas e dissociação de H+ preferencialmente a valores elevados de pH em CaCl2 (acima de 5), devido à menor acidez (PCZ mais alto) dos radicais Fe-OH e Al-OH. O formato côncavo foi atribuído a cargas permanentes e a maior dissociação de H+ a valores menores de pH em CaCl2 (abaixo de pH 5), uma vez que o radical Si-OH é considerado um ácido forte (PCZ baixo). Para um mesmo pH em CaCl2 verificou-se a seguinte seqüência nos valores de V em função da mineralogia da fração argila: solos com predomínio de óxidos de Fe e Al &lt; solos com predomínio de caulinita &lt; solos cauliníticos com minerais 2:1.

Clay Mineralogical Composition of Tea Garden Soils in Shandong Province, China

For assistance of the appropriate plant-nutrient management practice to keep the sustainable tea pro- duction in Shandong Province, particle-size and clay mineral analyses were carried out to the surface layer of soils collected in tea gardens of Laoshan region of Qingdao City and Dahainanchun region of Jimo City, Shandong Province, People's Republic of China. Variation of the particle-size distribution with sites was small in each region. The clay content ranged from 17.6 to 22.7% for soils from Laoshan region and from 16.1 to 18.6% for soils from Dahainanchun region, and the texture was clay loam for the former and sandy clay loam for the latter. All the soils showed the similar X-ray diffraction patterns of the clay fraction, and vermiculite, mica, ser- pentine and quartz were identified in common. Among them, vermiculite was predominant followed by mica and serpentine. Similarity in the clay mineralogical composition, along with the regional similarity in the particle-size distribution, suggests origination of soils from eolian dust in an extensive area and is easy for the comprehensive performance of the plant-nutrient management practice to soils in the tea garden in

Mineralogical implications for the Late Pleistocene glaciation in Amery Oasis, East Antarctica, from a lake sediment core

AbstractThe clay mineralogical composition of a 552 cm long sediment core from Lake Terrasovoje in Amery Oasis, East Antarctica, was analysed and compared with that in surface sediments from other locations in the vicinity. The lower part of the sediment core is formed by sub- and proglacial sediments with a dominance of smectite and illite, and lower amounts of kaolinite and chlorite. The upper part of the core is deposited after 12 500 cal yr bp and mainly composed of illite and kaolinite, with low amounts of smectite and chlorite, such as found in samples from rock outcrops and covering sediments throughout Amery Oasis. The clay composition in the lower section of core Lz1005 suggest that the basin of Lake Terrasovoje was filled by a 150–200 m thickened Nemesis Glacier prior to 12 500 cal yr bp rather than by local ice caps.

Clay Mineralogical Composition of Representative Paddy Soils in Northern Part of Northeastern Japan

Clay Mineralogical Composition of Representative Paddy Soils in Northern Part of Northeastern Japan

EFFECTS OF SECONDARY SOIL FORMING PROCESSES AFTER DEPOSITTION ON THE CLAY MINERALOGICAL COMPOSITION OF SALINE SOILS AND ACID SULFATE SOILS IN VIETNAM

The clay mineralogical composition was examined for 4 profiles of each of saline soils and acid sulfate soils collected from some important river systems of Vietnam. Predominant clay minerals of saline and acid sulfate soils were found to be mica and kaolinite, accompanied with mica/vermiculite/smectite∼mica/smectite mixed-layer mineral, vermiculite, chlorite and smectite. The clay mineralogical composition of these soils was compared with that of alluvial soils from the corresponding river systems/agro-ecological regions in order to clarify the effects of the secondary soil forming processes of salinization and acidification (as a result of pyrite oxidization) on the clay mineralogical composition of the soils. It was hardly observed the mineralogical differences based on the distribution pattern of major clay minerals in the clay fraction. Then, examination of correlation between mineral contents was taken for the selected pairs of clay minerals, and the clay mineralogical alteration was somewhat indicated. In saline soils, it was the transformation of mica into expansible 2:1 layer silicate minerals. In alkaline saline soils, the transformation of mica into vermiculite occurred principally due to presence of a large amount of Ca and Mg salts in soil. In case of acid sulfate soils, the transformation into kaolinite (1:1 layer mineral) was suggested. However, such clay mineral transformations have occurred limitedly in soils. This is probably due to prevention of the development of salinization and oxidation by the secondary soil forming processes under paddy-rice cultivation and mangrove forestation. Based on these results, it could be asserted that saline soils and acid sulfate soils, in general, still kept the essence of the original alluvial soils.

Clay-mineral record in Lake Baikal sediments: The Holocene and Late Glacial transition

We analyse the clay-mineralogical composition of two 1-m long cores from elevated plateaus in the southern and northern basins of Lake Baikal. Our aim is to test the limits of classically used clay proxies for climate reconstructions. Mineralogical signature is determined by X-ray diffraction on oriented aggregates from Holocene and Late Glacial sediments. Mineralogical results are presented on a palaeomagnetic-derived time scale. Sampling at a centimeter resolution allows for a sub-millenial order reconstruction. The evolution of clay-derived climate proxies (smectite/illite peak intensity ratio, S/I) is compared between the two locations, with respect to other climate reconstructions for the Lake Baikal area and Siberia. During the Late Glacial punctual increases of S/I are related to changes of particle source rather than any climate change. At both sites the most intense chemical weathering conditions occured during the Subboreal, lagging the Eurasian middle Atlantic climate optimum. S/I follows a gradual but irregular increase through the Holocene, probably related to slow warming favourable to the development of the Siberian soils. The different sensitivity to hydrolysing conditions in northern and southern sites can be explained by a combination of local lithological and topographical parameters.

Paleoweathering conditions of Upper Carboniferous siliciclastic rocks of SW Hungary

The clay mineralogical and chemical compositions of Upper Carboniferous siliciclastic rocks from the western flank of the Villány Mountains (Téseny Sandstone Formation) have been investigated to determine paleoweathering conditions, as well as to appraise the influence of the post-depositional processes upon source rock signature. The clay-mineral assemblage of the samples consists predominantly of illite±muscovite, suggesting a potassium metasomatism in the Téseny clastics. Therefore the use of the Chemical Index of Alteration (CIA), which provides a consistent quantitative framework for examining weathering, leads to erroneous conclusions without correction for K-metasomatism. When considered in Al2O3-CaO* + Na2O-K2O (A-CN-K) compositional space, orthogneiss and igneous rock clasts selected from the Téseny conglomerate reflect two different weathering trends; one (including orthogneiss, quartz diorite, and andesite samples) shows an ideal trend observed for granodioritic rocks, and the other (including aplite, rhyodacite, and rhyolite samples) follows a trend from a slightly more K-feldspar-rich fresh rock composition than that of average granite. Intermediate to intense chemical weathering of the source areas is indicated by premetasomatized CIA values of 77–84 for the samples from borehole Siklósbodony-1, suggesting that these rocks have gained about 6–7% K2O (in A-CN-K space) during metasomatism.

CLAY MINERALOGY OF ALLUVIAL SOILS AND GREY DEGRADED SOILS DERIVED FROM THE SAME RIVER SEDIMENT IN THE RED RIVER DELTA, NORTHERN VIETNAM

Five samples of alluvial soils and 3 samples of grey degraded soils, both derived from the sediments of the Thaibinh River system in the Red River Delta, northern Vietnam, were subjected to clay mineralogical analysis in addition to measurement of pH, organic matter content and particle-size distribution. The pH was comparable between the two soil types. In contrast, the organic matter and clay contents were remarkably lower for grey degraded soils than for alluvial soils. Predominant clay minerals in both soil types were mica and kaolinite; the mica content was higher for alluvial soils while the kaolinite content was higher for grey degraded soils. Chlorite-vermiculite intergrade was detected only in grey degraded soils, whereas vermiculite was present in alluvial soils instead. Absence of goethite in grey degraded soils might be a cause of their grey color. A sign of degradation on the amount (clay content) and type (clay mineralogical composition) of clay minerals was indicated in grey degraded soils in the Red River Delta, leading to decrease in the organic matter content and then to decline in the soil fertility.

Field Experiment on Long-Term Application of Chemical Fertilizers and Farmyard Manure in Floodplain Soil of Bangladesh

Field experiment on long-term application of chemical fertilizers and farmyard manure is ongoing in a floodplain soil of Bangladesh since 1978. The treatments are application of N, NP, NK, NPK, NS, NZn, NSZn, NPKSZn, and N+FYM (cowdung as farmyard manure), along with control (no addition), and have been executed in every cropping. Forty-five times of paddy-rice cropping was done before soil sampling in July 2002. Among chemical properties of soil, the organic matter and total N concentrations, clay mineralogical composition, and the heavy metal concentration were assessed. The organic matter and total N concentrations of surface soil were increased from those in the initial state, although this was ascribed to continuous cropping of paddy-rice rather than the direct effect of chemical fertilizers and farmyard manure. Clay mineralogical change, such as fixation of K in the vermiculite interlayer to be transformed into clay mica, was not detected. Accumulation of heavy metals in soil was not noticed.

Spatial trends in the geochemical composition of sediments in the Panuco River discharge area, Gulf of Mexico.

Major and trace elements, organic matter, carbonates, loss of ignition, grain size, gravel, sand, silt, clay, and qualitative mineralogical composition were determined on surficial marine sediments sampled during the stormy (February), dry (May), and rainy (September) seasons in the coastal area adjacent to Panuco River discharges into the Gulf of Mexico. The sediments supplied by the river move in a north-east direction, and are deposited in the north-east extreme of the studied area. Terrigenous sediments show a strong association of Al2O3 with Fe2O3, Na2O, K2O, P2O5, Rb, Cu, Zn, organic matter, clay, and grain size (Mz). Mineralogical analysis shows that they are formed by quartz, kaolinite, montmorillonite, illite-montmorillonite and biotite. The highest metal concentration of Cu (25 mg/kg), Zn (155 mg/kg), Pb (50 mg/kg) and organic matter (1.26%) was observed in the sampling points located very close to the river mouth. A statistical analysis was done with the information contained in the variables. Five significant factors explain 77% of the total variance: factor 1 is due to sediments from a terrigenous source, factor 2 corresponds to sediments from a biogenous source, factor 3 is associated to sediments with heavy minerals, factor 4 is due to Co concentration, and factor 5 is due to Ni concentration. The sediments supplied from the river had a short-term local impact on the sediment distribution, as observed by the carbonate and heavy mineral concentration of the sediments.

Clay mineralogical composition of alluvial soils from different river systems/agro-ecological regions in vietnam in reference to origin, regional distribution and soil quality

Sixteen profiles of alluvial soils of Vietnam were collected throughout the country and subjected to clay mineral analysis. Alluvial soils from different river systems/agro-ecological regions had different clay mineralogical compositions due to differences in sediment sources. Mica and kaolinite were found to be predominant clay minerals in alluvial soils. Other major minerals detected were vermiculite, smectite, chlorite, and the mica/vermiculite/smectite∼mica/smectite mixed-layer mineral, depending on the river systems. The clay mineralogical composition was remarkably similar within soil units belonging to the same river system and in a profile. However, the clay mineralogical composition greatly varied with river systems; therefore, the regional variation existed and was mainly controlled by the mineralogical features of the sediment sources. Mica was found to be altered to mixed-layer minerals in some soils under specific conditions. The soil quality was assessed from the viewpoint of inherent potentiality based on the type and amount of clay minerals as plant-nutrient sources. Alluvial soils distributed in the Red River and Mekong River systems were evaluated to be in the high level of inherent potentiality. Those from the Trakhuc River and Ba River systems were classified to have low inherent potentiality, while those from the remaining ones were to be at an intermediate level.

Clay Mineralogy and Chemical Composition of Bentonites from the Gourougou Volcanic Massif (Northeast Morocco)

AbstractThe Gourougou volcanic massif (northeastern Morocco) is actively prospected for bentonite deposits. Five bentonites originating from different environments were selected for the present study: hydrothermal alteration of obsidian perlite glass inside the volcanoes themselves (Providencia and Tribia deposits); alteration of pyroclastic flows in a marine shallow water to lagoonal lacustrine environment (Ibourhardayn deposit); ash falls in marine or lacustrine systems (Moulay Rachid and Melg el Ouidan (formerly Camp Berteau) deposits). All of these bentonites were probably formed from volcanic glass originating from a rhyolitic magma at different stages of differentiation as shown by slight variations of REE and incompatible element abundances. The crystal-chemical characteristics of the smectite vary according to alteration conditions: beidellite predominates in hydrothermal systems, whereas montmorillonite predominates in lagoonal and lacustrine environments, and mixed-layer beidellite-montmorillonite in the sea-water-altered pyroclastic flows. All these dioctahedral smectites exhibit a heterogeneous distribution of charge as shown by the presence of partially expandable (1 EG) or non- expandable (0 EG) layers in the K-saturation state. The proportion of the collapsed or partially expandable layers is not related to the average layer charge or to the cation exchange capacity. This militates for an overall heterogeneous charge distribution. Compared to other natural or experimental alteration systems of similar rhyolitic glass, the formation of beidellite or montmorillonite appears to be controlled by the amounts of Mg in the system.

Mineralogical and geochemical evolution of a basalt-hosted fossil soil (Late Triassic, Ischigualasto Formation, northwest Argentina): Potential for paleoenvironmental reconstruction

Reconstruction of paleoclimatic conditions in the Ischigualasto basin, northwestern Argentina, has been constrained by fi eld studies coupled with mineralogic, whole-rock, and fi ne-fraction chemical and stable isotope analysis of a Triassic (Carnian) basalt-hosted fossil soil. Field evidence, such as wedgeshaped aggregate structure and slickensides, indicate this was likely a paleo-Vertisol. Whole-rock analysis defi nes down-profi le trends in clay mineralogy and chemical composition that are consistent with modern soils developed upon basalt parent material. X-ray diffraction analysis indicates that the basaltic parent material is dominated by plagioclase with trace amounts of weathered 2:1 phyllosilicate. Overlying weathered horizons show a progressive loss of plagioclase and an increase in phyllosilicates with minor amounts of kandite clays and detrital quartz. X-ray diffraction analysis of the <2 µm fraction shows that the weathered layers are dominated by dioctahedral smectite (montmorillonite) with a minor fraction of kaolinite in the upper layers of the profi le. There is a progressive loss of basic cations in conjunction with an increase in concentration, on a wt% basis, of conservative elements from the basalt upward through the weathering profi le. The combined data indicate that this soil likely formed on a stable landscape in a cool and humid climate. In addition, the presence of quartz in the paleosol profi le suggests an eolian contribution of sediment during pedogenesis. Despite these apparent morphologic and bulk chemical trends indicative of a pedogenic origin, none of the authigenic minerals formed in isotopic equilibrium. However, based on measured oxygen and hydrogen isotope compositions, these minerals apparently formed from meteoric waters with a narrow range of δ 18 O and δD compositions at different temperatures. If this is correct, then amygdaloidal calcites formed at ~60‐100 °C, followed by precipitation of montmorillonites at 49‐57 °C during late-stage hydrothermal alteration. Finally, goethite formed at low temperatures of 6 ± 3 °C in a pedogenic environment. This complex history of hydrothermal alteration and pedogenic overprinting brings to light the need for cautious interpretation of bulk chemical trends in paleosols as a means for paleoclimate reconstruction. Comparison of the calculated Triassic oxygen isotopic compositions of meteoric water and soil temperature with modern environments suggests that this soil formed in a seasonal, humid, and cool climate.