E. Soleimani Sardoo; M.H. Farpoor
Abstract
Introduction: Several archaeologists believe that there is a relationship between cultural residuals, human beings, and soil. Soil related factors such as age index, climate change, and paleoclimate are important in archaeology. Soils could be accounted as records of invaluable information. Appropriate ...
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Introduction: Several archaeologists believe that there is a relationship between cultural residuals, human beings, and soil. Soil related factors such as age index, climate change, and paleoclimate are important in archaeology. Soils could be accounted as records of invaluable information. Appropriate compiling of these data cause better understanding of soil and landscape genesis, and human activities in the past. There are two distinguished archeological sites of Daqyanous (Islamic Era) and Konarsandal (before Islamic Era) in Jiroft area. Besides, Konarsandal site is surrounded by old and new Halilrood channels. Since no data about the comparison of soil evolution in the mentioned archeological sites were available, the present research was conducted to compare soil evolution of archaeological sites using soil classification, clay mineralogy, and micromorphology in Jiroft area.
Materials and Methods: soil samples were collected from three different archaeological sites including new channel of Halilrood (pedon 1), old channel of Halilrood (pedon 2) and, Daqyanous (pedon 3). The samples were air-dried and sieved (2 mm). Routine soil physical and chemical analyses including pH, EC, soil textural class, soluble sodium, calcium, and magnesium, and gypsum and calcite contents were performed. The studied pedons were classified using Soil Taxonomy system according to morphology, laboratorial results, and field observations. The clay minerals were determined by X-ray diffraction (XRD) method after carbonates, organic matter, and Fe were removed using Jakson (1965) and Kittrik and Hope (1963) procedures. Ten undisturbed samples were selected for micromorphology studies and thin section preparation.
Results and Discussion: Pedon 1 is affected by Halilrood River sediments, that is why an old soil together with a young soil was formed. Salinity and SAR in the old soil were higher than the upper young soil. A textural discontinuity was found between the old and the young soils. Natric, calcic, and gypsic horizons were found in pedon 1 and caused a Typic Natrargid to be formed in new Halilrood channel. Natric horizon due to high Na cation was formed in pedons 1 and 2. On the other hand, salic, natric, and cambic horizons formed a Typic Haplosalid in pedon 2 (old Halilrood channel). High salinity and SAR in the upper layers caused salic and natric horizons to be formed. Pedon 3 with argillic horizon is an old polygenetic soil. Available humidity in the past caused removal of carbonates from upper layers that followed by clay illuviation and argillic horizon formation. Salinity and SAR in this soil were low and a heavy texture was found in pedon 3. Since pedon 3 showed cambic, argillic, and calcic horizons, it was classified as Arenic Haplargids. Calcium carbonate, gypsum, Fe oxides, and clay coatings were among dominant micromorphological features observed in the studied pedons. Konarsandal archeological site is located in the lowlands of Jiroft plain downward Rabor and Baft elevations. Lenticular gypsum crystals could be attributed to the solution of upward Neogene formations and groundwater close to the surface which evaporates due to capillary. Powdery calcite, Fe-oxides, and clay coating and infilling of gypsum in pore spaces of pedon 1 were observed by micromorphological investigations. Diffused clay coating around pore spaces is explainable by high sodium content and Natric horizon formation. Lenticular, interlocked plates, and infillings of gypsum were observed in pedon 1. However, gypsum with irregular shapes and low content was investigated in pedon 2. This is due to location of this pedon in Halilrood old channel. That is why pedon 2 affected by Halilrood during long periods of time is unstable and shows less evolution compared to pedon 1. Irregular and lenticular forms of gypsum show weak soil development due to low rainfall, high evaporation, and excess salt. High NaCl is reported as a requirement for lenticular gypsum formation. This form of gypsum is supported by high salinity in pedons 1 and 2. High Na and natric horizon formation in pedons 1 and 2 caused dispersion of clay and ceased formation of clay films around pore spaces. Gypsum was not found in pedon 3 during filed and laboratory studies. Besides, gypsum was not observed by micromorphological observations. Clay and calcite coatings and calcite infillings were among the micromorphological features observed in pedon 3. Calcite coating on clay coating in this pedon could be attributed to the climate with more available humidity in the past followed by an arid climate. Carophyte algae fossil was only observed in pedon 3. Kaolinite, illite, chlorite, smectite, and palygorskite clay minerals were determined by X-ray diffraction. Palygorskite is highly related to the parent material and climate. Pedogenic palygorskite formation from transformation of 2:1 clay minerals and/or neoformation is reported by several studies.
Due to the impact of paleoclimate with more available humidity, palygorskite was not found in Daqyanous archeological site. It seems that higher humidity in the past did not allow palygorskite formation or transformed it into smectite. Chlorite and illite are originated from parent material. Evidences of pedogenic mica minerals in arid and semi-arid environments were also found which is due to K fixation among smectite layers. Smectite with pedogenic origin is also reported by Sanjari et al. (29) in the study area. Chlorite, illite, and kaolinite clay minerals seem to be originated from parent material in the present study.
Conclusion: Laboratories analyses and micromorphology observations clearly showed weak development in Konarsandal pedons compared to high evolution of soils in Daqyanous archaeological site. The same results were also found for unstable surfaces of pedons 1 and 2 compared to stable surface of pedon 3. The stable surface provided the accumulation of clay and calcite coatings around the cavities and the formation of argillic and calcic horizons indicating high soil development. Results of the study showed polygenetic formation in soils. Soils in old Halilrood channel show high salinity and Na adsorption ratio compared to other two pedons under study.
A. Bayat; M. H. Farpoor; A. Jafari
Abstract
Introduction: Soil genesis and development in arid and semi-arid areas are strongly affected by geological formations and geomorphic surfaces. Various morphological, physical, and geochemical soil properties at different geomorphic positions are usually attributed to different soil forming factors including ...
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Introduction: Soil genesis and development in arid and semi-arid areas are strongly affected by geological formations and geomorphic surfaces. Various morphological, physical, and geochemical soil properties at different geomorphic positions are usually attributed to different soil forming factors including parent material and climate. Due to variations in climate, geological formations (Quaternary, Neogene and Cretaceous) and geomorphology, the aim of the present research was the study of genesis, development, clay mineralogy, and micromorphology of soils affected by climate, geology and geomorphology in Bardsir area, Kerman Province.
Materials and Methods: The study area, 25000 ha, starts from Bardsir and extends to Khanesorkh elevations close to Sirjan city. The climate of the area is warm and semi-arid with mean annual temperature and precipitation of 14.9 °C and 199 mm, respectively. Soil moisture and temperature regimes of the area are aridic and mesic due to 1:2500000 map, provided by Soil and Water Research Institute. Moving to west and southwest, soil moisture regime of the area changes to xeric with increasing elevation. Using topography and geology maps (1:100000) together with Google Earth images, geomorphic surfaces and geologic formations of the area were investigated. Mantled pediment (pedons 1, 3, 7, and 8), rock pediment (pedon 2), semi-stable alluvial plain (pedon 6), unstable alluvial plain (pedon 5), piedmont plain (pedons 9 and 11), intermediate surface of alluvial plain and pediment (pedon 4), and old river terrace (pedon 10) are among geomorphic surfaces investigated in the area. Mantled pediment is composed of young Quaternary sediments and Cretaceous marls. Rock pediments are mainly formed by Cretaceous marls. Quaternary formations are dominant in alluvial plains. Alluvial terraces and intermediate surface of alluvial plain and pediment are dominated by Neogene conglomerates. Siltstone, sandstone, and Neogene marls together with Neogene conglomerates are among dominant geological formations of piedmont plain. Eleven pedons affected by young Quaternary sediments, Neogene and Cretaceous marls in aridic, aridic border to xeric, and xeric moisture regimes on above-mentioned geomorphic surfaces were described and sampled using Natural Resources Conservation Service (2012) guideline. Physicochemical properties, clay mineralogy, and micromorphology of soil samples investigated and soils were classified by Soil Taxonomy (2014) and WRB (2015) systems.
Results and Discussion: Calcic, gypsic, argillic, and cambic diagnostic horizons investigated after field and laboratory studies. Typic Calcigypsids, Lithic Torriorthents, Typic Haplogypsids, Typic Haplocalcids, Typic Torrifluvents, Sodic Haplocambids, Typic Calciargids, and Xeric Haplocalcids subgroups were found using Soil Taxonomy (2014) system. Gypsisols, Calcisols, Luvisols, Cambisols, and Regosols reference soil groups identified by WRB (2015) classification system. Developed Alfisols, formed on piedmont plain geomorphic surface in xeric moisture regime. On the other hand, Entisols formed on rock pediments with aridic moisture regime. Soils in aridic moisture regimes were little developed with gypsic horizon, and where calcic horizon was formed, it was near the surface. Moving to the west with increasing humidity, gypsum was leached from the pedon and clay illuviation caused argillic horizon to be formed. Formation of Btk horizon in pedon 9 was attributed to a more paleoclimate. The maximum gypsum content of 44.7 % (gypsiferous soils) was found in soils affected by Quaternary formations and Cretaceous marls, but the maximum calcium carbonate (44 %, calcareous soils) was investigated in soils formed on Neogene conglomerate formations. Moreover, the maximum sodium adsorption ratio (SAR) content (29.2 (mmol(±) L-1)0.5) was determined for soils on unstable surface of alluvial plain. Smectite, vermiculite, illite, kaolinite, and chlorite clay minerals were investigated and smectite to illite ratio increased moving from aridic to xeric moisture regimes that prove the pedogenic source of smectite from weathering of illite. Coating and infilling of calcium carbonate, lenticular and interlocked plates and infillings of gypsum, and clay coatings were observed during micromorphological investigations. Micromorphological observations also showed that gypsum crystals decreased and calcite crystals and thickness of clay coatings increased from aridic to xeric moisture regimes. The minimum amount of gypsum crystals was found in Neogene formations. The results also showed that gypsum pedofeatures are dominant in Cretaceous formations, but calcium carbonate pedofeatures are the main features of Neogene formations. Due to presence of animal voids (channel, regular and star-shaped vughs, chamber, and vesicles), spongy microstructure was formed in agricultural lands.
Conclusion: Results of the research showed the important role of parent material, climate, and geomorphic surface on genesis and development of soils in Bardsir area.
Mohammad Akbar Bahoorzahi; Mohammad Hady Farpoor; Azam Jafari
Abstract
Introduction: The optimum and sustainable use of soil is only possible with correct and complete understanding of its properties. The objectives of the present research were to study 1) genesis and development of soils related to different geomorphic surfaces in Kouh Birk Area (Mehrestan City), 2) Soil ...
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Introduction: The optimum and sustainable use of soil is only possible with correct and complete understanding of its properties. The objectives of the present research were to study 1) genesis and development of soils related to different geomorphic surfaces in Kouh Birk Area (Mehrestan City), 2) Soil classification according to Soil Taxonomy (2014) and WRB (2014) systems, and 3) physicochemical properties, clay mineralogy and micromorphology of soils.
Materials and Methods: Mean annual rainfall and soil temperature in the selected location are 153.46 mm and 19.6 oC, respectively. From geological point of view, the studied area is a part of west and south west zones and Flysch zone of east Iran. Soil temperature and moisture regimes of this part are thermic and aridic, respectively. Eight representative pedons on different surfaces including rock pediment, mantled pediment, Alluvial fan and Upper terraces were selected, sampled, and described. Routine physicochemical analyses, clay mineralogy, and micromorphological observations performed on soil samples. Soil reaction, texture, electrical conductivity, calcium carbonate, and gypsum were identified. Four samples including Bt horizon of pedon 1, Bk1 horizon of pedon 4, By2 horizon of pedon 5 and Bk1 horizon of pedon 7 were selected for clay mineralogy investigations. Four slides including Mg saturated, Mg saturated treated with ethylene glycol, K saturated, and K saturated heated up to 550 oC were analyzed. A Brucker X-Ray diffractometer at 40 kV and 30 mA was used for XRD analyses. Undisturbed soil samples from Bt horizon of pedon 1, Bk2 horizon of pedon 2, Btn horizon of pedon 3, By2 horizon of pedon 5, Bk1 horizon of pedon 7, and By1 horizon of pedon 8 were selected for micromorphological observations. A vestapol resin with stearic acid and cobalt as hardener was used for soil impregnation. Bk-Pol petrographic microscope was used for micromorphology investigations.
Results and Discussion: Due to the presence of argillic and petrocalcic horizons in rock pediment, soils of this surface were more developed compared to other landforms. High amount of CaCO3 (39.5%) was observed in pedon 4 on rock pediment geomorphic surface which is attributed to calcareous parent material. The presence of argillic horizon in this geomorphic position is due to the more available water of the past climate. The maximum salinity was observed in the mantled pediments. Calcic over gypsic horizons formed in pedon 7 on alluvial fan surface due to higher solubility of gypsum than calcium carbonate. Kaolinite, illite, chlorite, and palygorskite clay minerals were found in pedons 1 and 4 on rock pediment. Palygorskite in this position seems to be pedogenic, but kaolinite, illite, and chlorite are inherited from parent material. Mantled pediment and alluvial fan showed smectite, kaolinite, illite, chlorite, and palygorskite clay minerals. Pedogenic smectite in this position is probably formed from weathering of illite and chlorite. On the other hand, palygorskite stability decreased in mantled pediment surface. This is the reason why smectite was the dominant clay mineral in this landform. Clay and calcite coatings were investigated in Bt horizon of pedon 1 (rock pediment). Coatings and infillings of calcite in Bk2 horizon of the same geomorphic position caused a calcic crystallitic b fabric. A diffused clay coating due to the presence of Na in Btn horizon of pedon 3 in rock pediment was observed. Micromorphological observations of By2 horizon in pedon 5 (mantled pediment) showed gypsum interlocked plates and gypsum infillings. Interlocked plates formed due to re-solubility of gypsum crystals. Micro spars and infillings of calcite are among dominant pedofeatures found in Bk1 horizon of pedon 7 (alluvial fan geomorphic surface). A calcic crystallitic b fabric and Primary calcite mineral were also observed in this pedon. Release of Ca from calcareous parent material caused Ca+2 to SO4-2 ratio to be increased which could be a probable source of gypsum formation. Results of the study showed that more and less developed soils formed on rock pediment and upper terrace geomorphic surfaces, respectively. Illuviation of clay, gypsum, and CaCO3 together with formation of cambic, calcic, petrocalcic, gypsic, argillic, and natric horizons were among the dominant pedogenic processes in studied soils. Paleosols containing Bt horizons were only observed on rock pediment geomorphic surface. Kaolinite, illite, chlorite, and palygorskite clay minerals were observed in almost all surfaces. Smectite was not discovered in rock pediment, but was only investigated in mantled pediment and alluvial fan which could be attributed to higher available moisture of formation time in these surfaces. Secondary calcite and gypsum caused stability of pedogenic palygorskite in soils under study. Micromorphological observations proved the presence of clay and calcite coatings, calcite and gypsum infillings, and gypsum interlocked plates. Gypsum pedofeatures were not observed in rock pediment, but clay and calcite pedofeatures were only found. On the other hand, clay and calcite pedofeatures were not observed in upper terraces and gypsum pedofeatures were the only features determinded in this position.
Conclusion Results of the present research showed that difference in soil characteristics is highly affected by geomorphology.
