Engineering characteristics and environmental impacts of the expansive Ankara Clay,and swelling maps for SW and central parts of the Ankara (Turkey) metropolitan area

Volume-changing clay soils constitute the most costly natural hazard to buildings on shallow foundations. With the existing expansive clays in Ankara, low-rise buildings at the southwest part of the city have shown damage resulting in considerable maintenance costs. This paper reports the findings of an experimental investigation emphasizing the swelling behavior of Ankara Clay and correlations between the swelling parameters and other soil properties, and present a synthesis of observed damage details. The poor performance of the affected light-weight structures is assessed in the light of environmental conditions. In addition, swelling maps for SW and central parts of the Ankara metropolitan area, based on measured and predicted swelling parameters, are constructed for the purposes of land-use planning and general assessment of environmental problems. The experimental results suggest that the clay has high-to-very high activity, depth of active zone generally ranges between 1–2 m, the use of remolded and desiccated specimens seems to be a better approach in swelling tests, and the empirical equations based on two or more index or physical properties are good predictors for the estimation of the swelling potential of the clay. High swelling pressures exerted by the soil, flat topography and poor drainage, climatic conditions and poor construction methods are the main reasons of the structural damage observed at the study site.     

钻孔岩心黏土混浊水电导率、黄铁矿、pH相关性分析及其在古沉积环境复原的应用:以渤海湾西岸平原DC01孔为例

为探讨复原海岸平原沉积环境和精确划分海陆相地层的有效方法,对渤海湾西岸海河以南平原深达30 m的DC01孔岩心以约20 cm间距取样,测试黏土混浊水电导率（EC）、黄铁矿质量分数（w（FeS₂））和pH值,并开展相关分析研究。结果显示,EC与w（FeS₂）正相关（相关系数r为0.47）,而EC与pH以及w（FeS₂）与pH均负相关（r分别为-0.43和-0.52）。根据EC值的大小将DC01孔自下至上分成5个带（Ⅰ—Ⅴ）,进一步分别对5个带的EC、w（FeS₂）及pH做相关分析,结果显示,Ⅱ带相关性最为突出：EC与w（FeS₂）的相关系数为0.83,极强正相关;EC与pH的相关系数为-0.77,强负相关;w（FeS₂）与pH的相关系数为-0.45,呈中等程度负相关。根据Ⅱ带的EC和w（FeS₂）极强正相关、且EC和w（FeS₂）均明显偏高以及多发育黑色泥炭和腐殖质黏土等特征,推断Ⅱ带为受海水影响的盐沼环境;结合AMS¹⁴C测年结果,推测8 260~7 470 cal.B.P.期间,海水曾经影响到DC01孔的位置。另外,Ⅳ带的EC值也偏高,但w（FeS₂）却较低,其EC与w（FeS₂）的相关系数为-0.03,不呈正相关关系,其原因是因为接近地表的上部沉积物因淋溶作用,在Ⅳ带形成淀积层导致EC异常偏高;最上层的Ⅴ带为淋溶层,这样就导致钻孔上部（深6.7 m以上）Ⅳ带和Ⅴ带EC与w（FeS₂）的相关性出现异常。因此在讨论沉积物上部沉积环境时,将EC与w（FeS₂）综合分析可以更精确地划分钻孔岩心的沉积环境。     

Evaluation and Prediction of the Swelling Characteristics of Nigerian Black Clays

The swelling characteristics of black clays from two major areas of occurrence in Borno State, Nigeria, were investigated in the laboratory. Clay samples derived from lagoonal clay deposits showed high swelling tendencies while those samples derived from Olivine basalts showed medium to high swelling tendencies. Although interparticle swelling was the dominant swelling mechanism, soil samples with higher clay contents exhibited higher swelling tendencies. The developed predictive models show that the free swell percentage as well as the swelling pressure can be predicted from measured values of electrical conductivity, specific gravity, clay content and plasticity index. On the other hand, swell percent can be predicted from measured values of electrical conductivity and specific gravity only.     

The structure and dynamics of 2-dimensional fluids in swelling clays

The interlayer pores of swelling 2:1 clays provide an ideal 2-dimensional environment in which to study confined fluids. In this paper we discuss our understanding of the structure and dynamics of interlayer fluid species in expanded clays, based primarily on the outcome of recent molecular modelling and neutron scattering studies. Counterion solvation is compared with that measured in bulk solutions, and at a local level the cation-oxygen coordination is found to be remarkably similar in these two environments. However, for the monovalent ions the contribution to the first coordination shell from the clay surfaces increases with counterion radius. This gives rise to inner-sphere (surface) complexes in the case of potassium and caesium. In this context, the location of the negative clay surface charge (i.e. arising from octahedral or tetrahedral substitution) is also found to be of major importance. Divalent cations, such as calcium, eagerly solvate to form outer-sphere complexes. These complexes are able to pin adjacent clay layers together, and thereby prevent colloidal swelling. Confined water molecules form hydrogen bonds to each other and to the clays' surfaces. In this way their local environment relaxes to close to the bulk water structure within two molecular layers of the clay surface. Finally, we discuss the way in which the simple organic molecules methane, methanol and ethylene glycol behave in the interlayer region of hydrated clays. Quasi-elastic neutron scattering of isotopically labelled interlayer CH₃OD and (CH₂OD)₂ in deuterated clay allows us to measure the diffusion of the CH₃- and CH₂-groups in both clay and liquid environments. We find that in both the one-layer methanol solvates and the two-layer glycol solvates the diffusion of the most mobile organic molecules is close to that in the bulk solution.     

The Influence of Placement Conditions on the Swelling of Variable Clays

The swelling of clay when it is subjected to moisture increase is a complicated process found to be influenced by several factors. The clay??s level of response is highly dependent on its mineralogical composition and structure. Practicing geotechnical engineers use the placement state and general index properties to forecast the swelling behavior of the soils. The purpose of this study was to investigate the influence of placement conditions on various clays and to demonstrate that the swelling of a particular clay type should not be predicted using information and trends obtained for other clays with different origins. Clay from Saudi Arabia was used to investigate the influence of initial moisture content and initial dry density on swelling. The prediction models created by other researchers were compared to the measured values in this study. The swelling behavior of both initially dry and wet prepared bentonite was examined, and the rate at which swelling developed in the bentonite clay was studied. The role of clay content in the volume change of sand?Cbentonite mixtures was also investigated. It was concluded that the prediction of clay-swelling parameters should not be based on the properties of other clays with different origins and mineralogical compositions. The trends published in the literature should be taken as a general guide only, and the influence of moisture content and dry density on swelling should be verified for individual sites. Because clay content significantly influences the overall volume change, it should be carefully assessed in each case.     

Environmental geological and geotechnical investigations related to the potential use of Ankara clay as a compacted landfill liner material, Turkey

Clay-bearing Upper Pliocene red clastics and Quaternary alluvial deposits occupy the Ankara basin. The clayey levels of the Upper Pliocene deposits, referred to as Ankara clay, is considered as a source for compacted clay liners due to their low coefficients of permeability and widespread distributions throughout Ankara. This study investigates the geological, geotechnical and mineralogical properties of the founding clayey soils at two sites of the Ankara region. The geotechnical index properties along with the hydraulic conductivities of the clayey soil samples collected from these sites were determined. A mathematical relation between the clay mineralogical content and hydraulic conductivity was established. The results of this investigation show that, from a geotechnical point of view, Ankara clay may be regarded as a highly suitable material for a compacted clay landfill liner given that its mineralogical compatibility with leachate is confirmed.     

Dynamic compaction properties of bentonite-based materials

Dynamic compaction tests of bentonite-based materials (BBMs) with 100, 70 and 50% bentonite contents have been performed using five powdery bentonites with different physicochemical properties to establish the simplified evaluation method for dynamic compaction properties of BBMs. For a given bentonite content and a total compaction energy condition, the maximum dry density, ρ_dmax, and the optimum water content, w_opt, which are well-known indexes of compaction properties, for BBMs were determined according to the type of bentonite used for BBMs. For evaluation of those values of BBMs derived in this study, the plastic limit of BBM, w_pbbm, was defined as the plastic limit that was measured using the sample pulverized to a maximum grain size of less than 425 μm in the case of BBM with sand having a maximum grain size of more than 425 μm and was measured using the powdery bentonite itself in the case of BBM without sand. This study proposed equations for evaluating ρ_dmax and w_opt of BBMs with more than 50% bentonite content under the total compaction energy conditions of 551–2755 kN-m/m³ using w_pbbm. Finally, we related the equations derived in this study to the equation for evaluating hydraulic properties of compacted BBMs proposed in previous work and proposed the preparation method of BBMs with more than 50% bentonite content for constructing BBM buffer by in-situ compaction method.     

吉林省东部石炭-二叠系伊利石的成因标志

吉林东部石炭-二叠系主要是一套泥质岩石, 其详细深入的矿物学工作尚不多见。利用JSM-6700F场发射电镜及INCA能谱仪,研究了伊利石的显微形貌和微区成分。采用D/max-2500 X-射线衍射仪,研究了伊利石的结晶度、多型和b₀值。结果表明:研究区伊利石结晶度变化于0.26~0.77,平均值为0.44;伊利石（白云母）多型有3种类型,分别为1M_d型、1M_d+2M₁混合型和2M₁型;伊利石（白云母）b₀值为8.996~9.045,平均值为9.007Å。石炭系伊利石结晶度变化于0.26~0.50,平均值为0.35,主要呈2M₁多型,b₀平均值为9.011Å,主要是低级近变质带的产物;二叠系伊利石结晶度变化于0.26~0.50,平均值为0.42,主要为1M_d+2M₁混合型多型,b₀平均值为9.004Å,主要为晚期成岩带的产物。     

The combined effect of clay and moisture content on the behavior of remolded unsaturated soils

The behavior of unsaturated clayey soil is highly influenced by the coupled interaction between water and clay content. Various aspects of the behavior of artificial clay–sand mixtures with variable water content were experimentally studied. Laboratory tests were utilized for the determination of consistency limits, the stress–strain relationship, strength parameters, hydraulic conductivity, and volume change characteristics for various combinations of water and clay content in soil mixtures.

Results presented for various clay–sand mixtures include: new normalized consistency limits; the combined effect of clay content and water content on the stress–strain relationship and on the strength parameters (c and φ); and the effect of clay content on hydraulic conductivity and swelling potential. The cohesion of clayey sand is found to increase with increasing water content to a certain limit, above which it decreases. The angle of internal friction for clayey sand is found generally to decrease with increasing water content. The degree of saturation is found to be better than the water content in explaining the strength behavior. The hydraulic conductivity sharply decreases with increasing clay content up to 40% beyond which the reduction becomes less significant. Simple empirical equations are proposed for predicting the swelling potential of clayey soils as a function of either the clay content or plasticity index.     

大兴安岭北段新林地区晚石炭世花岗岩的岩石成因及地质意义

大兴安岭北段新林地区晚古生代花岗岩主要出露在大乌苏和富西里附近,岩性主要为二长花岗岩,另有少量花岗闪长岩。对其中二长花岗岩样品进行LA-ICP-MS锆石U-Pb测年表明,大乌苏和富西里岩体侵位年龄分别为（303.7±2.2）和（300.5±0.5）Ma,均为晚石炭世岩浆活动的产物。花岗岩具有富硅（w（SiO₂）为66.77%~75.85%）、富碱（w（Na₂O+K₂O）为7.41%~8.69%）、高铝（w（Al₂O₃）为12.90%~16.22%）,低MgO、CaO、TiO₂的特点,属于钙碱性系列;铝饱和指数（A/CNK）为1.06~1.44,为过铝质岩石;镜下未见原生白云母、堇青石、石榴石等富铝矿物,不同于富铝的S型花岗岩;而w（P₂O₅）与w（SiO₂）负相关,呈I型花岗岩特征;富集LREE和Ba、Rb、K等大离子亲石元素,亏损Nb、Ta、Ti等高场强元素,与后造山I型花岗岩特征相似,应形成于拉张的构造环境。花岗岩的⁸⁷Sr/⁸⁶Sr为0.712 938、¹⁴³Nd/¹⁴⁴Nd为0.512 386,（⁸⁷Sr/⁸⁶Sr）_i值为0.704 4,ε_Nd（t）值为-1.09,T_DM2=1 172 Ma,源区物质主要为中-新元古代从亏损地幔增生的地壳物质。结合区域研究成果,大兴安岭新林地区晚石炭世岩浆侵位活动与额尔古纳-兴安地块和松嫩地块碰撞拼合后岩石圈伸展环境有关。     

Geotechnical evaluation of Turkish clay deposits: a case study in Northern Turkey

Clay deposits in Oltu-Narman basins (Erzurum, northern Turkey) have been studied to determine their engineering properties and to evaluate their uses for geotechnical applications. These deposits are concentrated in two different stratigraphic horizons namely the Late Oligocene and the Early Miocene sequences. Clay-rich fine-grained sedimentary units are deposited in shallow marine and lagoonar mixed environments. Their clay minerals originated by the alteration of Eocene calc-alkaline island-arc volcanics, preferably from pyroclastics (trachite and andesite flow), which form the basement for the Oltu depression. Smectite group clay minerals are found abundant in clay deposits. The experimental results show that the clay soils have high plasticity behaviors and low hydraulic conductivity properties. The optimum water content, the free swell, and the swelling pressure of clay samples decreased and the maximum dry unit weight of clay samples increased under high temperature. Consequently, it is concluded that the expanding of clay soils is an important soil problem that cannot be avoided in the significant parts of Oltu city and its villages. However, the soils of clay-rich layers in the outcrops-section of clay deposits can be successfully used to build compacted clay liners for landfill systems and to construct vertical and horizontal barriers for protection of ground water and for preventing soil pollution in geotechnical applications.     

内蒙古西乌旗迪彦庙蛇绿岩带内辉长岩地球化学及年代学

内蒙古西乌旗迪彦庙蛇绿岩位于二连浩特—贺根山蛇绿岩带与交其尔—锡林浩特蛇绿岩带一线之间,大地构造位于中亚造山带中段的锡林浩特晚古生代褶皱带。本文主要对其内的辉长岩进行了地球化学及年代学研究。研究结果表明：辉长岩w（SiO₂）为45.49%~50.48%,w（Al₂O₃）为13.31%~17.05%,w（K₂O）为0.01%~0.65%,w（Na₂O）为0.30%~4.15%,w（CaO）为8.00%~19.54%,w（MgO）为5.22%~10.92%,w（P₂O₅）为0.03%~0.23%,显示西乌旗迪彦庙蛇绿岩中的辉长岩属于高铝、低钾、低钠的拉斑系列;辉长岩的稀土元素总量低,重稀土元素比轻稀土元素富集,微量元素Nb、Zr、Hf、Ti相对亏损,K、Ta、Sr相对富集;La-ICP-MS锆石U-Pb测年获得辉长岩的年龄为（345.3±2.3）Ma,为早石炭世。综合分析,辉长岩可能为受到俯冲作用产生的流体交代而成,而并非结晶分异作用所致;迪彦庙蛇绿岩形成环境为弧前环境。     

Modification of physical, mechanical and hydraulic properties of bentonite by thermo-hydraulic gradients

The conditions of the bentonite in an engineered barrier for high-level radioactive waste disposal have been simulated in a series of tests. Cylindrical cells with an inner length of 60 cm and a diameter of 7 cm have been constructed. Inside the cells, six blocks of FEBEX bentonite have been piled-up, giving rise to a total length similar to the thickness of the clay barrier in a repository according to the Spanish concept. To obtain the blocks, the clay with its hygroscopic water content has been uniaxially compacted at a dry density of 1.65 g/cm³. The bottom surface of the material was heated at 100 °C and the top surface was injected with granitic water. The duration of the tests was 6, 12 and 24 months. The temperatures inside the clay and the water intake were measured during the tests and, at the end, the cells were dismounted and the dry density, water content and some hydro-mechanical properties of the clay (permeability, swelling pressure and swelling under load) were measured at different positions. The values obtained are compared to those of the untreated FEBEX bentonite. The injection of water provokes in the vicinity of the hydration surface an increase of the water content and a decrease of the dry density due to the swelling of the clay, while heating gives rise to an increase of the dry density and a reduction of the water content in the 18 cm closest to the heater, even after 2 years of thermo-hydraulic (TH) treatment. The swelling capacity and the hydraulic conductivity after TH treatment are mainly related to the dry density and water content attained during it. No major irreversible modifications of these properties with respect to those of the untreated clay have been detected.     

大兴安岭漠河前哨林场侵入岩年代学、岩石地球化学特征及其地质意义

前哨林场大地构造上位于大兴安岭北段额尔古纳地块北部的漠河前陆盆地边缘。本文研究了大兴安岭漠河前哨林场侵入岩的岩相学、年代学及岩石地球化学特征,探讨了研究区内侵入岩的形成时代、岩石成因及其构造环境。LA-ICP-MS锆石U-Pb定年结果表明,花岗岩形成于199.9~199.3 Ma、辉长岩形成于（201.8±2.6） Ma,即研究区内的花岗岩、辉长岩均形成于晚三叠世—早侏罗世。岩石地球化学研究表明：花岗岩的w（SiO₂）为63.22%~70.10%,w（Al₂O₃）为12.43%~14.36%,里特曼指数（σ）为0.74~1.65,属高钾钙碱性系列岩石,具有较低的Mg^#值（平均值为39.43）,w（TFeO）为2.80%~4.41%,w（CaO）为1.47%~3.38%,轻重稀土分馏明显,富集轻稀土,亏损重稀土,δEu为0.48~0.84,富集Rb、Ta、K、La、Nd、Zr、Ti等元素,相对亏损Th、U、Sr、P、Eu等元素;辉长岩的w（SiO₂）为51.42%~51.98%,w（Al₂O₃）为17.24%~17.73%,里特曼指数（σ）为3.00~3.53,属高钾钙碱性系列岩石,具有较高的Mg^#值（平均值为51.07）,w（TFeO）为9.06%~9.14%,w（CaO）为5.81%~6.69%,重稀土分馏不明显,δEu为0.86~0.98,富集Rb、Ta、Nb、Nd等元素,相对亏损Th、U、P、Eu等元素。上述岩石地球化学特征表明,花岗岩为辉长岩结晶分异的产物,原始岩浆起源于地幔,并受地壳物质的混染改造。研究区侵入岩形成于造山阶段挤压环境,是蒙古—鄂霍茨克洋俯冲碰撞的产物。     

Seismic and mechanical properties of Opalinus Clay: comparison between sandy and shaly facies from Mont Terri (Switzerland)

For the safe disposal of high-level radioactive waste, different host rocks are currently being considered. The favorable properties of clay are low permeability, some retention capacity concerning radionuclides, and the ability to self-seal cracks and fissures, e.g. by swelling or time-dependent compaction creep. In Switzerland, the Jurassic Opalinus Clay is envisaged as a potential host rock which—at Mont Terri—is subdivided into the sandy, shaly, and carbonate-rich facies, the latter being less abundant. For long-term safety assessments, the understanding of the relations of properties (e.g. mineralogical composition and microstructure) and performance (e.g. mechanical behavior) of clays and claystones is essential. In the case of the sandy Opalinus Clay, the mechanical strength increases with increasing carbonate content, because carbonates form the matrix. The mineralogical investigation of a set of sandy facies samples proved a significantly larger carbonate content (20–40 mass %) when compared to the shaly facies (10–20 mass %). The carbonates of the shaly Opalinus Clay, on the other hand, are mostly localized fossils aligned parallel to the bedding, acting as predetermined breaking points. Image analysis of SEM images of polished sections proved the determined microstructural differences. In addition, carbonate particles of the sandy facies are mostly isometric, whereas carbonate particles of the shaly facies cover a greater range of shapes. The mechanical tests were accompanied by investigations of the p- and s-wave velocities, which revealed that the anisotropy of the sandy facies is less pronounced than sedimentological analyses would suggest. The mechanical strength, which, for the first time, presents results of real triaxial tests of the sandy facies. The samples of the sandy facies exhibit a failure strength of σ _eff,B, approximately twice as high as was found for the shaly facies considering the deformation axis parallel to the bedding. Similar values were obtained when measuring perpendicularly to the bedding.     

Study on the swelling behaviour of blended clay–sand soils

Soils containing expansive clays undergo swelling that can be both detrimental and beneficial in various applications. In the Arabian Gulf coastal region, natural heterogeneous soils containing clay and sand (tills, shales, and clayey sands) support most of the civil infrastructure systems. Likewise, mixes of clay and sand are used for local earthwork construction such as roads and landfills. A clear understanding of the swelling behaviour of such soils is pivotal at the outset of all construction projects. The main objective of this paper was to understand the evolution of swelling with increasing clay content in local soils. A theoretical framework for clay–sand soils was developed using phase relationships. Laboratory investigations comprised of mineralogical composition and geotechnical index properties of the clay and sand and consistency limits, swelling potential, and morphology of clay–sand mixes. Results indicated that soil consistency of mixes of a local expansive clay and an engineered sand depends on the weighted average of the constituents. Mixes with 10% clay through 40% clay capture the transition from a sand-like behaviour to a clay-like behaviour. Influenced by the initial conditions and soil matrix, the swelling potential of the investigated mixes correlated well with soil plasticity (SP(%) = 0.16 (I _p)^1.188). The parameters sand void ratio and clay–water ratio were found to better explain the behaviour of blended clay–sand soils.     

改性膨胀土路堤填筑含水量优化试验研究

在控制含水量的前提下,对分别掺入不同量石灰、不同量水泥改性膨胀土试件进行强度和膨胀量试验,得到不同含 水量及不同石灰(水泥)掺量对改性膨胀土强度和膨胀性的影响,通过对实验所得数据的分析,找出含水量和掺石灰(水泥)剂 量的最佳融合点,并据此对膨胀土路堤填料的改性施工提出了一些有益的建议。     

Influence of Hematite Coating on the Activation of the Swelling Potential of Smectite-Bearing Rocks

The fraction of swelling-type clay minerals (smectites) is a first measure to estimate the swelling potential of natural rocks. This swelling potential is only activated if water can be incorporated in the sheet silicates. The samples studied in this work are volcanic rocks from the Southern Andes. According to the petrographic and mineralogical studies, the rocks are characterized as vulcanite with high content of smectite. Undisturbed samples showed minor swelling behaviour in conventional swelling tests, although X-ray diffraction and differential thermal analysis revealed swelling clay contents of more than 70 % in some samples. Powder swelling tests were performed on ground and recompacted rock samples. The results of these tests show a better agreement with those expected according to the mineralogical composition of the samples. The reason for the non-activation of the swelling potential in undisturbed samples was suspected to be the influence of the iron-oxide/hydroxide content, which was on average around 11 %. Scanning electron microscope images showed that the edge terminations of the clay particles are coated with hematite. The hydrophobic properties of hematite impede the access of water between the interlayers of the clay minerals and, in addition, hematite cementation prevents the expansion. In a further series of swelling tests water was replaced by a reducing solution (0.1 molar hydroxylammonium chloride) which removes the Fe-oxide coating. It can be shown that thus the swelling potential of the clay minerals in such undisturbed rocks can be activated.     

Mapping the Pliocene Clay Deposits Using Remote Sensing and its Impact on the Urbanization Developments in Egypt: Case Study,East Sohag Area

In the current study, Thematic Mapper image was compiled along with field and laboratory investigation results to map the Pliocene clay deposits. These deposits have high swelling potential; consequently they will have a negative impact on the urbanization expansion surrounding the flood plain zone (Low desert zone) in Egypt. Principle Component and Minimum Noise Fraction techniques with the help of supervised classification were successful in the mapping of these deposits. The interpretation shows that the Pliocene clay deposits occupy most of the wadis terraces and part of the wadis floors, and sometimes they covered by Quaternary deposits (1–5 m of sand and gravel). The physio-chemical characteristics of these deposits indicate that the Pliocene clay ranges from silty clay to clay with small amounts of sand. Laboratory analysis (Atterberg limits, saturation degree, and cation exchange capacity) indicate the swelling characteristics of the Pliocene clay. Different classification systems were applied and all reveal the expansive nature of this soil, which should be taken into account for future development in the area.     

Paleoenvironment of geomorphic surfaces of an alluvial fan in the eastern Isfahan,Iran, in the light of micromorphology and clay mineralogy

Alluvial fans are one of the most important landforms in geomorphological and paloenvironmental studies. The objective of this study was the application of clay mineral assemblages and micromorphological properties of the studied paleosols in the geomorphic surfaces of an alluvial fan in the eastern Isfahan as proxies for paleoenvironmental and paleoclimatic changes. Micromorphology, X-ray diffraction, and scanning electron microscopy approaches were used to study the representative pedons. The results indicated that the illuviation process in the calcareous soils of the arid regions of the eastern Isfahan was probably in response to Quaternary moist conditions. There was no significant difference between clay coating properties of the studied relict and buried paleosols. Clay mineralogical study suggested that kaolinite and illite were inherited from the parent materials, while smectite and palygorskite were formed in the soil environment. Paleoargillic horizon was characterized by smectite and calcic (especially the calcrete) horizons were dominated by palygorskite. Palygorskite was accumulated by both neoformation and illuviation processes. High clay content, high intensity of smectite peak, and activity of the illuviation process in paleoargillic horizon demonstrated the seasonality of climate (rainfall) even in the moist periods of Quaternary in Central Iran. Clay mineralogical assemblages suggested a trend of increasing environmental aridity in the study area. This study, therefore, highlighted the role of clay mineralogical investigations in arid lands’ geomorphological and paleoenvironmental researches.