Geochemical Processes Leading to Variation of Soil Development on Calcareous Toposequence in Semiarid Fields

This study was carried out in soils formed in different physiographic units (summit(PI), shoulder(PII), backslope(PIII), footslope(PIV)) on the limestone parent material under the same climatic conditions.The study was assessed clay mineralogy, weathering indices, mass loss/gain states, and physicochemical properties of different profiles with limestone parent material. It is concluded that smectite clay mineral is dominant in the footslope unit (PIV), with differences in clay mineralogies due to physiographic change. The highest aggregate stability (63.74%) was determined in the in situ physiographic summit unit. The soil's field capacity and wilting point contents showed statistically significant changes with the increase in smectite minerals and clay in the PIV profile on the footslope unit (p <0.01). A positive (0.506; p <0.05) correlation was found between the variability in physiographic units (from Summit to footslope) and the available water content (AWC). Bulk density and porosity characteristics varied depending on the particle size distribution and the type of land use. The soils formed in shoulder and backslope units, which are in the Entisol soil class, are classified as "not decomposed" according to the Chemical Alteration Index (CIA), Chemical Weathering Index (CIW), and Plagioclase Alteration Index (PIA) values. In the Inceptisol and Vertisol ordo, it was determined that the basic cations were leached in the PI and PIV profiles in the summit and footslope units, and the separation was more advanced. The highest losses from the soil were obtained from the backslope, while the gains were obtained from the footslope physiographic unit. As a result of this study, it has been revealed that soil formation in the summit and bottom lands (footslope) is more effective than other physiographic units, and physicochemical properties are affected by these processes.


INTRODUCTION
In general, soil is the name given to the earth's crust due to geochemical events and biological activities during the physical and chemical decomposition of organic and inorganic materials. Additionally, soil forms an integral part of the terrestrial ecosystem and ecosystem services. Its non-static, dynamic nature and unique balance between the system's physical, chemical, and biological components.
For the first time, Dokuchaev and later Hilgard revealed that different soils were formed under other environmental conditions, particularly with different climate and vegetation effects from a particular parent material (Dengiz and Senol, 2018). Joffe (1949) distinguished two types of soil formation factors, active and passive. He stated that passive soil formation factors only symbolize the substances that serve as the source of the mass and the conditions that affect the mass; these are the parent material, topography, and the passing process. He stated that active soil formation factors are the essential materials for soil formation and the means that provide energy affecting the mass and that organisms, climate, and partially the hydrosphere symbolize the soil formation factors in this class. Soil forming were explained by Simonsen (1959) as accumulation events in the soil (organic matter accumulation, new sedimentation), the transformation of soil parent materials, displacements in soil, events that prevent horizonization (clay leaching), and losses from the soil (leaching, erosion, etc.). In addition, White (2013) and Tuncay et al. (2019) stated that topographic factors mainly affect soil formation by altering the amount of water entering the soil profile, soil temperature, and erosion-transport and accumulation on the surface.
When parent material decomposes under the influence of environmental factors, the components present in their structure are released. According to the ecological conditions, it is known that many soil properties such as color, structure, permeability, plant nutrients vary according to these substances released as a result of decomposition (Mandel and Bettis, 2001;Schaetzl and Anderson, 2005;Dengiz et al. 2013). For instance, impermeable soil can be formed on the clayey-calcareous parent material, while dark-colored soils rich in plant nutrients occur on the basalt parent material (Young, 2012). Again, according to Pal et al. (2014), while Alfisol, Inseptisol, Entisol, and Mollisol soils are formed in granite-gneiss, calcic-gneiss parent materials in hot, semi-arid ecosystems, on the other hand, they stated that Mollisol and Alfisol soils formed on the parent materials such as limestone, micaceous sandstone in hot, humid ecosystems with 3000 mm rainfall. Dengiz and Baskan (2010), Saricaoglu et al. (2020) declared that topography is an essential factor in explaining the different character of soils and their formation, as well as the primary material, particularly in the local or small area. In this context, the researchers stated that the topographical elements, especially the slope, slope length, and slope direction parameters, cause microclimate, vegetation, and soil differences. Furthermore, they stated that soil erosion in the local area causes soil formation processes and differentiation by affecting the difference in speed and size depending on the degree of slope.
Mineral weathering, an essential part of the pediatric assessment, plays a vital role by transforming bedrock into decomposed parent material and soil that provides nutrients to ecosystems. In this case, during decomposition, the released elements are leached or accumulated according to ambient conditions due to various pedogenic processes (Lybrand and Rasmussen 2018;Tuncay et al. 2020). Among these processes, functions such as dissolution of primary minerals, formation of secondary minerals, redox reactions, transport of some materials, and ion exchange can occur. Especially the dominant secondary minerals of soils are clay minerals formed due to chemical changes of primary minerals. The amount and type of clay in the soil affect many of the soil's physical and chemical properties. In a study investigating the underlying soil formation stages in a glacial ecosystem (Mavris et al., 2010), it was determined that the coarse material decreased with physical decomposition, and the decomposition caused acidification by increasing the clay fraction. Clay minerals with a 2: 1 layered lattice structure, such as Montmorillonite, are characterized by a large specific surface area and high load, which increases water retention and cation exchange capacity (Fissore et al., 2016).
Moreover, the effects of Smectite clay mineral on the micro-aggregate formation (Fernández-Ugalde et al., 2012) and studies have shown that the type of clay minerals is essential in the stability of soils (Morgan, 2005). Again, Aboudi Mana et al. (2017) determined the permeability due to the pore structure of soils dominated by argillaceous minerals at low levels. Yilmaz et al. (2014), while large-scale aggregation occurs in kaolinitic soils, montmorillonite soils' stability was low. By Moghimi et al. (2012), the adequate properties for water-resistant aggregates were determined as organic carbon, kaolinite clay mineral, and Ca 2+ . Jones (1983) stated that in soils with a high swelling shrinkage rate depending on the clay type, root penetration resistance due to bulk density is low; Narloch et al. (2020) stated that while compressibility decreases in soils dominated by montmorillonite clay, it increases in soils dominated by kaolinite clay. For many years, it has been known that the changes of soils in the period for soil formation vary considerably depending on environmental characteristics. These changes involve mineral fragmentation, biological weathering, interactions, geochemical changes of elements and cycles in the soil plant-water system. Individual decomposition rates of soils vary due to changes in soil properties and differences in environmental conditions. Accordingly, soils are a complex system formed due to different combinations of factors that make soil. Today, there are two distinct approaches in characterizing soils and rocks in chemical weathering.
The first is the fluid aqueous environment's geochemical properties (Aiuppa et al., 2000;Phillips and Rojataczer, 2001). The second approach is the weathering indices applied to determine the weathered profile's geochemical and mineralogical properties and study soils' weathering processes by digitizing (Chesworth et al., 1981;White, 1983;Nesbitt and Wilson, 1992). There are some losses, gains, and transformations during the pedogenic processes in soil formation. Mass change indices such as chemical alteration index (CIA), plagioclase alteration index (PIA) base/sesquioxide index (R 2 O 3 ), in which the phenomena occurring within the specified processes are quantified, leaching, the state of chemical components or clay minerals reveal the decomposition of soils and their behavior during the process. (Egli et al., 2001(Egli et al., , 2003Gunal et al., 2011). Partition indices are traditionally calculated using different formulas using the molecular ratios of the significant element oxides. The stoichiometric change of important element oxides during decomposition occurs in index values. Each oxide's molecular ratio can be easily calculated using the weight percentage of their oxides in question. Chemical weathering indices, sometimes termed alteration indices, are often used to characterize dissociative profiles. Tuncay et al. (2020) stated that the topography changes under the same climate significantly affect the soil's physical and chemical properties, and the CIA and CIW also revealed this change. Ozaytekin and Dedeoglu (2021) reported that the weathering index values were distributed following the geological age in their study on the soils' weathering rates and mass balance formed on the Hasandag volcanic material.
This study aimed to examine the pedogenetic changes of Entisol, Inceptisol, and Vertisol soils with different development levels on the same land cover and the same parent material (limestone-marl) semi-arid ecological conditions, considering the weathering indexes, geochemical-chemical events, and mineralogical data.

Field description of the study area
The study area covers an area that includes the Sandikli district and its immediate surroundings, located within the provincial borders of Afyon ( When the study area's long years of climate data are examined, the average temperature is 10.8 o C, the annual precipitation is 362.40 mm, and the annual evaporation is 663.08 mm. The continental climate is dominant, with cold winters and hot and dry summers. According to Soil Survey Staff (2014), soil temperature and humidity regimes are examined when the soil temperature regime is Mesic, and the moisture regime is Xeric. Additionally, according to the Newhall model, Dry Xeric was determined as a subgroup of soil moisture regime (Newhall and Berdanier, 1994;Van Wambeke, 2000).

Soil and rock sampling
Within the study's scope, soil and rock sampling were carried out in four different soil profiles formed on the limestone base material representing different topographic positions in the section located in the northeast-southwest area. Soil profiles are located on the summit (PI), shoulder (PII), backslope (PIII), and footslope (PIV) physiographic units, respectively

Geo-chemical and mass balance analysis
The soil made air dry was passed through a 2 mm sieve to determine some physicochemical soil properties. The sand, silt, and clay contents (%) were determined by the Bouyoucos hydrometer method (Bouyoucos, 1951), soil color in dry and moist condition using Munsel color scale according to Soil survey staff (1993). Electrical conductivity (EC) and soil reaction (pH) were measured in a 1: 1 soil-water suspension (Soil Survey Staff, 2014). Additionally, CaCO 3 content of soils, exchangeable cations with ammonium acetate (Mg ++ , Ca ++ , Na + ve K + ), organic matter content (Soil Survey Staff, 2014), moisture constants (Klute 1986), and wet aggregate stability (Kemper ve Rosenau, 1986) were determined.
Cation exchange capacity (CEC) values were found by saturating soils with Na-acetate, then extracting with ammonium acetate and reading the extracted sodium in atomic absorption spectrophotometer (Richards, 1954;Anonymous, 1973). The wet sieving method (with a single sieve diameter) recommended by Kemper and Rosenau (1986)   The formula in question is for the entire profile If M jflux is negative, it indicates loss from the system; if it is positive, it indicates participation in the system. If the beginning of soil formation is known, the annual decomposition rate is resolved by dividing the value found by the previous year.

Primer and seconder mineralogical and thin section analysis
The proportional distribution and degrees of the abundance of primary minerals in ground samples were determined by an X-ray diffractometer (2θ=2-70 o ) (Jackson, 1963). To determine the clay mineral type, leaching, decantation, lime removal, centrifugation, and sedimentation processes. The resulting clay fractions were separately saturated with 1N MgCl, and KCl leached and plated. In obtaining XRD peaks, the air dry and potassium 550 o C, in part saturated with potassium, air dry in the parts saturated with magnesium, and magnesium was made after 16 hours in ethylene glycol steam in the desiccator at 60 o C. Clay peak graphs were obtained in the XRD device (2θ=2-15 o range) (Whittig and Allardice 1986).
The textures of minerals and rocks with thin sections were determined by photographing them under the microscope (Murphy et al., 1977).

Statistical analysis
Significance levels of changes in soil properties were determined by applying the TUKEY's multiple comparison test. Evaluations were made using the ANOVA menu in Minitab 17v. Package program.

Some physicochemical and morphological characteristics of soils
Morphological descriptions of the horizon belonging to the soil profiles included in the study are given in Table 1, and their images are shown in Figure 3. The PI profile formed on the physiographic summit unit was classified as Typic Haplustept. The PI profile has A-Bw-C defining horizons. it has been ranked as Typic Haplxerept in the Inceptisol ordinance since it shows an advanced soil formation than Entisols and it has diagnostic horizon (cambic) depending on the structural development. The PII soil profile was classified in the Lithic Xereorthent subgroup and was determined by the Entisol ordo since it does not contain a subdiagnosis horizon. As the physiographic unit, the profile grouped as Shoulder has an A/C horizon sequence. Backslope is classified in the Entisol order in the PIII profile located on the physiographic unit. These soils located on sloping lands are shallow soils that do not have enough pedogenetic processes due to exposure to erosion, especially since enough vegetation does not cover them. They are classified in the Lithic Xereorthent sub ordinance. Its profile coded as PIV is located on the footslope physiographic unit and classified as Typic Haplustert. These soils are deep and heavy textured soils with high clay content and have Ap/Ad2/Bss/C horizon sequences.
Profile horizons, designated PI, have a clay loam and clay texture, with a moderate, medium granular structure, plastic when moist and slightly hard when dry. Soils covered with pasture cover, formed on limestone parent material. The PII profile horizons' bodies are clayey loam on the surface, silty clay, and silty clay loam to the deep; the surface is covered with pasture vegetation, the primary material is limestone. PIII profile also has a texture of clay loam and granular structure development in the surface horizon and the darker color on the surface; the color gets lighter as the profile approaches towards the parent material, depending on the lime increase. The color in the profile surface horizon, symbolized by PIV, is 5 YR4/2 in dry conditions and 5 YR3/2 in humid conditions. This situation continues homogeneously within the profile. Although clay loam is in the texture surface horizons, it turns into a clay structure due to the clay ratio increasing towards the depths. Soils with granular structure in A horizons, semi-angular block structures have occurred in deeper areas.
Primarily, there are widespread and small slickenside formations in 49-78 cm depth, which is one of the critical indicators of vertisol soils. Its main material is limestone and colluvial deposit.
In local areas with high topographic differences and similar main material-bedrock and similar land cover-use at short distances, the landform and different topographic positions significantly impact the soils' formation and development processes. Even if the climatic conditions are the same in a region, it has been stated by the researchers that a significant change in the topography may cause the formation of different soils. In this context, Sağlam and Dengiz (2015) found that the soil formed in the bottom land position and the fine materials brought by the waters from the sloping lands are deep, rich in clay, and have low permeability. The contribution of different main materials' physical, chemical, and mineralogical properties causes local soil formation differences. Therefore, although the region's topographical conditions and geological diversity have the same climate, diverse soils have been formed under different drainage conditions. In the study conducted by Dengiz and Baskan (2010) to determine the relationship between soil profile development and land formdifferent topographic position, it was determined that topographic positions in the formation of soils affect the morphological, physical, and chemical properties of soils. Thus, it is thought that the slope degree is one of the essential factors affecting the soil formation process in the soil profiles on the slope lands. Again, Sommer et al. (2008) reported that depending on the geomorphological situation and spatially changing soil erosion, some parts of the land will erode faster than others. Therefore, soil development will be different.
Some physicochemical properties of the soils belonging to the study area are given in Table 2. The soil profiles' pH level is a slightly alkaline reaction, and the salinity problem has not been determined. The change in EC content was primarily defined in the PIV profile, the footslope physiographic unit. At the pH level, the difference was determined in PII and PIII profiles, which have the narrowest shoulder and backslope physiographic units. Lime content in the horizons varied significantly, and the highest value was determined in the PIII profile on the backslope. In contrast, the lower lime content was determined in the PI and PIV profiles with higher soil formation. The reason for low levels of CaCO 3 in these soils is that lime is transported from the profile by leaching.
On the other hand, the narrow range of PII and PIII soil properties' variation and the high levels of lime content have emerged due to insufficient water penetration from the physiographic unit into the profile. Tuğyan and Sungur (2020)  the dissolution of carbonates, while K (0.05-1.08 cmokg -1 ) and Na (0.02-0.24 cmokg -1 ) ions were detected at low levels.

Mineralogy of rock and clay
The representative rock-thin section microscope image of the soils formed on the limestone parent material is shown in PI and PIII profile rocks are sharply fractured, dark gray, calcite veined limestone with intense fractures and cracks (Figure 4). The rock, which has a micritic texture, consists of very thin intraclass and scarce fossils. The rock has melting cavities with many broken fissures, and these are filled with spar calcites. Calcites are medium to small sizes and crystallized interlocked with each other. Pyrite minerals are also found in the rock as opaque.
The X-ray diffractometers taken in the soil body to determine the mineralogical properties of the PI and PII numbered profiles opened in the study area are given in Figure 5.
Smectite, muscovite, and quartz minerals were determined from the primary minerals in the body of the soil profile numbered PI (Table 3) Primary minerals in the body of the soil profile numbered PII were identified as smectite, muscovite, quartz, cristobalite, and calcite ( is thought that the profile with a high slope, whose intensity has decreased with the mineral depth seen, may have come with superficial transport. The X-ray diffractometers taken in the soil body to determine the mineralogical properties of the PIII and PIV numbered profiles opened in the study area are given in Figure 6. PIII soil profile is formed on limestone parent material with Ap-AC-Cr horizon sequence. Among the primary minerals, muscovite, smectite, sanidine, quartz, and calcite were found in the soil body. The Cr horizon did not include muscovite, smectite, sanidine, and quartz minerals (Table 3). As the soil profile formed on the limestone main material in the colluvial deposit position reached the Cr horizon, the parent material's activity increased. Secondary peaks of muscovite, sanidine and quartz minerals were not observed. The intensity of the calcite peaks increased in parallel with the limestone, increasing the material efficiency. Calcite, quartz, muscovite, sanidine, and smectite were determined in order of density (Table 3).
The PIV soil profile has formed on the limestone-colluvial deposit parent material in the Ap-Ad2-Bss-C horizon sequence. Smectite, muscovite, microcline, orthoclase and quartz were found in the soil body. Furthermore, the secondary peaks of microcline, orthoclase, and muscovite minerals were determined only in the Ap horizon, while the muscovite mineral peaks were determined in the Ap and Ad2 horizon. In order of density, quartz, microcline, orthoclase, muscovite, smectite were determined. The abundance of microcline and orthoclase minerals decreased with depth, and muscovite became the second mineral during abundance (Table 3). The profile with colluvial character and stony terrain is very high from the host rocks (Beckmann and Thisse. 1987).
The clay fraction X-ray diffractometers are given in Figure 7 (Table 4). An increase in the peak intensity of the crystallized chlorite and smectite minerals with depth was detected.  (Table   4). The reduction in peak intensity is associated with the increase for sand (46.27%) and the texture of the sandy loam.  (Table 4). A decrease in the illite peak intensity was observed in the Ad2 horizon, but there was no change in the order.
When the distribution of clay minerals in the profiles was examined, the smectite mineral determined at the PI, PII, and PIII profiles at a deficient and medium level was determined as more very abundant in the PIV profile. All profiles contain illite and kaolinite minerals. The PIV profile did not determine the chlorite mineral in low and medium levels in PI, PII, and PIII profiles. The high amount of swelling clay, having cracks extending deep from the surface in dry seasons and causing sliding surfaces to be seen in the profile from place to place, increases the transport with the slope.

Weathering indices and mass balance of soils
The values of the weathering indices of the profile horizons belonging to the study area are given in There are significant variations in the indices of dissociation resulting from the physiographic difference. It was determined that soil formation processes were more effective in PIV profile with in situ summit and footslope slope. Thus, the weathering indices were higher than the others. According to the CIA classification values stated by Nesbitt and Young (1982), the soil profiles PII and PIII were determined as "undissociated"(≤50), and the soil profiles PI and PIV numbered as slightly decomposed (60-80%). The CIA value can reach 100% in soil, and sedimentary material where leaaching and decomposition are intense and kaolinite and gibbsite clay minerals are present (Ozaytekin et al., 2012). In shale rocks, it varies between 70-75% (Tuncay et al., 2019). It is evident that in PII and PIII profiles, there are differences in water penetration into the soil and washing depending on the physiographic unit. The classification belonging to the CIA is valid within the CIW. Harnois (1988) proposed the CIW classification in a modified approach by removing K 2 O from the CIA. Al is immobile compared to Ca and Na elements, and increases in the decomposition degree with high mobility of Na and Ca increase CIW. Soil profiles PII and PIII are "undissociated" (50) and and Ti). The base /R 2 O 3 ratio, which generally gives results between 1-10, is below 1, which indicates the mobility of basic cations in the profile. Therefore, it is seen that basic cations are leached out, and decomposition occurs in PI and PIV profiles. Bases/R 2 O 3 ratio decreases as the weathering increases in soils (Mourier, 2008).
The mass balance model is used to quantify the amount resulting from loss/gain and transformations for any element during the soil formation period (Brimhall and Dietrich, 1987). The horizon's bulk density and chemical contents and the parent material or bedrock must be known to reveal the mass balance model (Brimhall et al.,1991). The mass balance equation has been developed to reveal open system losses/gains concerning the decomposition of soils and the parent material based on these features. Brimhall and Dietrich (1987), Brimhall et al. (1991), and Chadwick et al. (1990) tried to reveal the volumetric and mass changes of soils during their formation.
Stationary elements such as Ti or Zr are used to produce such loss/gain values. Ti element was used in the study (Brimhall and Dietrich, 1987;Harden, 1988, Chadwick et al., 1990Brimhall et al, 1991). Langley-Turnbaugh and Bockheim (1998); successfully applied it on rocks rich in silicates. Egli and Fitze (2000) have revised the method. There are also sedimentary rocks in the study area. It was also applied to the soils formed on this main material to test the method's success. If M jflux is negative, it indicates loss from the system; if it is positive, it indicates participation in the system.
About 70-80% of quartz, plagioclase and K-feldspar minerals dominate the earth's crust (Nesbitt and Markovics, 1997). The movement and loss of alkali and alkaline earth elements are good indicators of the disintegration-decomposition state (Nesbitt et al., 1980). Alkali and alkaline earth elements (Na, K, Ca, and Mg) move away in arid-semi-arid climatic conditions.
The mass balance indexes and changes in loss gains of the study area's soil profiles are given in Table 6.
The mass function gave negative results for all cations (except PIV) except for the PI profile, K and PII profile Na. The greatest loss was determined as Ca (-583.74 g cm -2 ) in the PIII profile at the back slope. Mass transport values give negative results in profiles with pedological development. The profile in the foot slope position, on the other hand, showed positive results in terms of cations due to its accumulation position. Although silicon gains movement in tropical climates, it is open to transportation, especially in sloping lands. While negative mass transport results were obtained in PII and PIII numbered profiles in A-AC horizon sequence (weak profile development), PI and PIV numbered physiographic units were gained in summit and footslope units, respectively. Since the PI profile is limestone with silicon interlayer, it gives high SiO 2 values, which increased the summit physiographic unit's gain. Aluminum is enriched in advanced soil formation processes (Hill et al., 2000;Kurtz et al., 2000). Al, a mobile element, gave negative results in calculations. Soil formation processes are expected to give negative results in profiles in the initial stage (Gardner 1980;Gardner 1992;Jin et al. 2010;Taboada et al. 2006). Although limestone is the main material, the studied profiles, due to the superficial transport, from the parent materials of the surrounding magmatic origin and especially the biotite mineral origin, gave net negative results except for the PIII profile. While the PIV profile showed negative results for Al and Fe in Ap and Ad horizons, it gave a positive anomaly value due to the accumulation of clay and sesquioxide in the Bss horizon, albeit a little (Oh and Richter, 2005).

Relationships between the physical and mineralogical characteristics of soils
Some of the physical properties of the profiles are specified in Table 7. The aggregate stability in profiles varied between 51.74-63.74%, and the change between horizons was not statistically significant (P <0.01).
As determined at the lowest level in PII profile was determined at high levels in soils, showing the backslope physiographic unit (PIII) with high lime content. In summit physiography, it is thought that the reason for these values is that there is not much erosion and transport in situ and the clay content, which is effective in aggregation, is high. In aggregates in the soil, clay minerals, organic origin colloidal substances, iron, aluminum, manganese oxides, and calcium carbonate are among the influential parameters. (Branick and Lal, 2005). Lime and gypsum added to the soil provide more stable aggregates (Chan and Heenan, 1999).
While the change between FC (19.32-48.50%) and WP (11.02-35.40%) values in profile horizons is statistically significant, this change in AWC (8.30-13.90%) was determined to be insignificant. Field capacity and wilting point are determined at the lowest PII. These horizons have low clay content, and clay minerals are generally minerals with low swelling shrinkage potential. Due to these features, water retention is determined to be low.
Smectite is a clay type with a 2: 1 lattice structure, swelling shrinkage, and high water retention (Laird, 2016). Field capacity and wilting point were determined in the highest foot slope physiographic unit. In this profile, the clay amount is high, and the abundance level of smectite minerals is high. Available water content was determined in the highest backslope physiographic unit. The low density of the smectite clay mineral in the PIII profile is thought to cause the water content held at the wilting point to be lower, depending on the amount of clay. The available water content increases when water's retention energy decreases with decreased wilting point values. Although field capacity varies significantly depending on texture, organic matter, and structure (Karahan et al., 2014), the variety and amount of clay minerals effectively change the wilting point. (Lal and Shukla, 2004). Again, the high lime content in the PIII profile and the porosity above the average caused the field capacity to be determined at high levels after PIV.
The bulk density values of the profiles (1.37-1.53 g cm -3 ) varied insignificantly, and the porosity (34.91-48.67%) varied at a statistically significant level. PIII and PIV profiles' Ap horizon is the release horizon and has a lower bulk density and higher porosity than other horizons. With the processing, the bulk density decreases as the aeration pores increase on the soil surface and the penetration resistance decreases (Kuhwald et al., 2020). At the depths of the subsoil, the bulk density increase over time and the porosity decreases. The presence of an Ad horizon in the PIV profile indicates a horizon with a root boundary, and an increase in bulk density values has been observed in this horizon. In general, increases in bulk density were determined with the increase for clay.
The relationships showing the correlations of soil physical properties with clay mineral density and physiographic unit are shown in Table 8.
The physiographic unit (from the summit to footslope) and smectite showed a positive As a result of this study, the differences in the clay minerals of the soils formed on the limestone main material under the same climatic conditions and the variations in the soil formation processes according to physiographic units were revealed. It has been determined that soil formation processes occur faster in the in situ summits and footslope physiographic unit. Statistically significant variations in physical properties were found within the soil profile due to weathering. It has been revealed that due to the accumulation of smectite clay minerals in the soil formed on the bottom lands, the water retention properties of the soils are high, and the segregation is more advanced than the other units.