Showing 9 results for Micromorphology
M. H. Farpour, M. K. Eghbal, H. Khademi,
Volume 7, Issue 3 (10-2003)
Abstract
Gypsiferous Aridisols are of great importance and extent in arid and semi-arid environments. There is a close relationship between soil genesis and landscape positions. This study aimed to determine the genesis and classification of gypsiferous soils and to investigate the relationship between micro-and macro-morphology of gypsum crystals and geomorphic positions in Rafsanjan area. The study area is located in Nough, 30 km north of Rafsanjan with a mean annual precipitation of 60 mm. Seven representative pedons were selected on different geomorphic positions. Physico-chemical, micromorphological, XRD, and SEM observations were performed on soil samples. Rock pediment geomorphic surfaces, that are in fact peripheries of old closed water bodies in central Iran, are the source of gypsum in the area. Large gypsum pendants and microforms of lenticular, vermiform, platy, and interlocked gypsum plates are found in rock pediment. The amount of gypsum and the size of pendants decrease moving down the slope. Lenticular and interlocked gypsum plates are found in a transition of pediment and playa. Puffy ground is observed on the saline surface of playa. Lenticular and vermiform gypsum crystals increase down the slope, but alabastrine gypsum is the most dominant form of gypsum in the playa surface. Large amounts of soft gypsum nodules are found on the rock pediment surface (western slope). In addition, spindle form of gypsum and palycrete bundles are observed in this position. Wind action played a significant role in the genesis and development of soil in rock pediment. A close relationship was found between morphology of gypsum crystals and geomorphic positions.
S. Ayoubi, M. Karimian Eghbal, A. Jalalian,
Volume 10, Issue 1 (4-2006)
Abstract
Paleosols include soils formed under climatic condition different from the present. Although such soils are widespread in central Iran region, adequate investigations of them are yet to be carried out. Micromorphology is one of the most important tools in plaeoclimatological studies. This investigation was carried out to study microscopic features of two paleosols from Isfahan province to reconstruct the paleoclimatic condition during the Quaternary. The results of this study indicate that strong clay coatings are presented in Sepahanshahr paleosol, indicating moisture regime in the past. This paleosol is polygenetic due to calcite and gypsum accumulation during drier periods compared to clay illuviation condition. Micromorphological features in Segzi paleosol indicate that this area has experienced a swampy environment during the younger Dryas. The overall results from this study indicate that climatic oscillation evidences during Quaternary have been preserved in paleosols from Isfahan region.
Sh Ghergherechi, F Khormali, Sh Ayoubi,
Volume 14, Issue 51 (4-2010)
Abstract
Gypsum is the most common sulfate mineral in soils of arid and semi-arid regions. Two hundred million hectares of the earth’s surface and about 28 million hectares of Iranian arid soils are covered by gypsiferous soils. The studied soils consist of alluvial plane and eolian plains in northern Iran. Soils were classified as Haplocambids, Aquisalids and Endoaquepts. In this study, genesis, formation and development of gypsum in soils were investigated. Study area includes different geomorphic surfaces from the upper watershed to alluvial plains. Gypsum crystals without considering their size, shape, arrangement are determined as pedogenic. In the weakly-developed horizons, in aridic moisture regimes, formation of euhedral pedogenic gypsum crystals and incomplete infilling of voids was dominant. In the well-developed soils, in xeric moisture regime, gypsum crystals are oriented and the perpendicular in arrangement of crystals along pores is dominants. Gypsum crystals occur in different shapes such as lenticular, tabular, and rosette-like and fan arrangement. Origin of gypsum in weakly-developed soils was weathered gypsiferous marls in upper Atrak basin. The source of gypsum in the soils with shallow ground water is high content of sulfate dissolved in soil solutions. In horizons affected by fluctuation of ground water contaning sulphur, euhedral tabular shape is dominant. In well-developed soils, based on Snowball morphology, gypsum is classified as stage II nodule. Results showed that there is no relationship between formation of the snowball morphology, b-fabric and kind of diagnostic horizons (A, B and C).
S. Shamsi Mahmoodabadi, F. Khormali,
Volume 15, Issue 55 (4-2011)
Abstract
In order to study the effects of different land uses on soil development, a loess hillslope was selected in Agh-Su area, eastern Golestan Province. Six profiles in four land uses including pasture, Quercuse natural forest, Cupressus artificial forest and a cultivated land, were dug and studied. Samples from different horizons were collected for physico-chemical and microscopic analyses. Important physical and chemical attributes such as bulk density (Bd), mean weight diameter (MWD), Organic carbon (SOC), cation exchange capacity (CEC), soil calcium carbonate (CCE) and available P were compared in land uses. Organic matter, CEC and MWD were significantly lower in the cultivated land use. Organic matter content in the forest and pasture area was considerably higher than that of cultivated land use. Soil profile development studies revealed that forest soils were highly developed. Quercus natural forest soils were classified as Calcic Argixerolls. Unlike cultivated soils which showed the minimum development and were classified as Typic Calcixerepts, formation of argillic horizon with dominant speckled b-fabric in the natural forest indicated the high landscape stability. Crystallitic b-fabric of horizons showed the absence of enough leaching of carbonate and the subsequent migration of clay particles. Intense erosion of the surface horizons of cultivated land use resulted in the outcropping of the subsurface carbonate rich horizon preventing soil development. The soils of pasture and Cuprecuse soils had mollic epipedon and were classified as Typic Calcixerolls with moderate development. Micromorphological properties of soils can help consider changes in pedogenic processes occurring under different land covers.
M. Ajami, F. Khormali,
Volume 15, Issue 57 (10-2011)
Abstract
Biological soil covers such as lichens have critical roles in soil stability and prevention of erosion. In order to study the effect of lichen biological covers on aggregate stability and soil conservation, loess hills covered with lichen and uncovered ones were selected in Northern Golestan Province. Five samples were taken from the depth 0 to 5 cm of both two areas for physico-chemical analyses. The undisturbed soil samples were taken for micromorphological studies, too. Analyses of soils revealed that soil organic carbon content increased markedly, compared to uncovered soils. Mean weight diameter also increased about three folds in soils covered with lichen. Fungal hyphae and polysaccharides excretions bind soil particles together and increase size of aggregates. Micromorphological study of thin sections showed that uncovered soils had a weak and massive structure, but soils covered with lichen had a crumb granular and also well -separated angular block and higher proportion of voids. Due to the effect of lichen on upward movement of calcium carbonate, crystallitic b-fabric appeared in the surface layer of covered soils and speckled b-fabric underneath. Excremental pedofeatures are the most common pedofeatures in the covered soils.
S. Sanjari, M. H. Farpoor, I. Esfandiarpour Borujeni, M. K. Eghbal,
Volume 15, Issue 58 (3-2012)
Abstract
Paleosols provide invaluable data on paleoclimatic conditions of the area. These soils widely exist in central Iran. Micromorphology and clay mineralogy are among valuable techniques which are useful for interpretation and identification of these soils. The present research was performed to compare the micromorphology and clay mineralogy of paleosols and modern soils of Jiroft area. After field studies, 4 pedons (located on different geomorphic surfaces including stable mantled pediment, stable and unstable transitional surfaces of pediment and alluvial plain, and stable surface of alluvial plain) were sampled for physicochemical, micromorphological, and clay mineralogical analyses. Clay coatings in argillic horizons of paleosols were found during micromorphology observations. On the other hand, clay coatings in present soils were only found in natric horizons, which were attributed to high amounts of Na in these soils. Moreover, smectite, palygorskite, illite, chlorite, and kaolinite clay minerals were recognized in paleosols, but chlorite was not detected in modern soils. The presence of palygorskite in the soils under study was related to the stability of geomorphic surface. Results of the present research showed that a more humid climate was present at the time of paleosols formation.
M. Liaghat, F. Khormali, S. A. Movahedynaeini, E. Dordipour,
Volume 16, Issue 61 (10-2012)
Abstract
Studies on the soils of western Golestan province show that regardless of increased rain and presence of clay minerals with high cation exchange capacity, potassium extractable with ammonium acetate is low. In order to find the reason for this low amount of available K, clay minerals and micromorphology of the soil porosity were studied. Twenty disturbed and undisturbed samples from each horizon were taken for physicochemical properties, mineralogy and micromorphological studies. Four selected profiles included Gypsic Aquisalids, Typic Endoaquepts, Typic Calcixerolls and Typic Hapludalfs. The results showed that in addition to the clay content and type of clay minerals in soils that can affect soil available K (Kava.), it seems soil porosity can also affect Kava. mainly through their effects on extension of roots, water and nutrients transmission. Favorable content of clay and dominance of smectites in Mollisols and also higher porosity and dominance of channel porosities caused the presence of higher Kava, in these soils. presence of HIS. poor soil drainage, reduction of Fe3+ in smectite crystal lattice in Inceptisols, and also less amount of porosities caused the presence of higher potassium fixation and reduction of Kava. in these soils.
M. Ajami, F. Khormali,
Volume 16, Issue 61 (10-2012)
Abstract
In order to study land degradation from the soil genesis and micromorphological perspective, ten soil profiles were dug and described on five slope positions in both forest and deforested cultivated land. The soil samples were taken from all horizons for physico-chemical analysis and micromorphological studies. Forest soils had a well developed argillic and calcic horizons and also mollic epipedon. These soils were classified as Alfisols and Mollisols. Carbonate leaching into the depth of soil profile and translocation of clays to lower layers and formation of developed soils are by no means related closely with the dense forest cover and its subsequent landscape stability and favorable leaching conditions. Dominant soil orders in this area were Inceptisols and Mollisols. In cultivated landuse, no argillic horizon was observed except in toeslope position. Absence of argillic horizon or its elimination following deforestation is one of the most important and obvious pedogenetic evidences of land degradation after land use change. Outcropping of high carbonatic layers (calcic horizon), disappearance of mollic and formation of ochric epipedon, presence of redoximorphic features attributed to runoff in lowland, decrease of solum thickness, and change of soil color were the other pedogenic indicators for land degradation in the study area. Microscopic observations showed that granular and crumb microstructures with high porosity were converted to massive and compact ones with low porosity in the deforested area. Disappearance of clay coatings besides absence of excremental pedofeatures were the other important micromorphological evidences of erosion and land degradation.
P. Asadi Alasvand, A. Heidari,
Volume 19, Issue 74 (1-2016)
Abstract
Technosols are modified soils affected by human activities. This study investigated genesis, classification and physicochemical properties of four pedons of Technosols developed on refused oil refinery materials and compared them with two unpolluted pedons. Mineralogical studies showed smectite as a dominant clay mineral with other clay minerals. These clay minerals adsorb oil compounds in their interlayer spaces and reduce their mobility and decomposition. Different micromorphological features resulting from oil compounds in soils, including depletion zones, types of coatings (quasi and hypocoating) and features due to horizontal and vertical movement of oil compound in soil showed dynamics of oil compounds and their effects on soil forming process. The refused petroleum compounds decrease pH and increase organic carbon, amorphous form of Iron in soils. Taking into account the presence of high amounts of gypsum and carbonate in polluted soil, the studied soils were classified as Typic Calcigypsids in Soil Taxonomy but in WRB system, due to the presence of impermeable geomembrane within 100 cm of soil surface, they were classified as Linic Technosols, showing the more precision of WRB system in their classification.
