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Karl Stahr - One of the best experts on this subject based on the ideXlab platform.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation. Materials and methods After studying an extensive number of road cuts in the field and mapping soil patterns in parts of the two basins by manual augering, ten pedons were selected for detailed description and sampling. Thin sections were analysed under a petrographic microscope, focusing on the micromorphology and optical properties of the cementing materials. Selected samples were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy to reconfirm the optical identification. The laboratory analyses included pH, carbonate contents, and X-ray diffraction analysis. Results and discussion The Duricrusts in the eastern Sado basin are indurated by silica. Combination of XRD and thin section analysis allowed to identify opal-CT as a major component, while opal-A is present to a lesser extent, and chalcedony is very rare. The cementing materials of the Duricrusts in the Oriola basin are palygorskite and calcite, which may occur alone or in combination within a soil profile. Conclusions The thick Duricrusts formed in the basins through precipitation of calcite, palygorskite and silica from lateral water flows, which ran from the Serra de Portel into the basins, during short moist seasons in a generally warm, semi-arid climate with strong evapotranspiration. Lithology of the upper catchment areas (element sources) and topography control the spatial distribution of the different Duricrusts. Their formation took place mainly during the Pliocene. Palygorskite transformation to smectite in the upper parts of the palycretes indicates that palygorskite is unstable in the present (more humid, typical Mediterranean) climate. This study demonstrates the potential role of lateral water and element transport in landscapes that need to be considered in pedological studies and concepts, and the use of mineral indicators of past climates such as palygorskite and the ageing stage of silica precipitations as tools for reconstructing environmental conditions and possible time of Duricrust formation.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation.
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Palygorskite-cemented crusts (palycretes) in Southern Portugal.
Soil Research, 2000Co-Authors: Karl Stahr, J. Trommler, K. H. Papenfuss, Mehdi Zarei, J Kuhn, Arieh SingerAbstract:In the Oriola depression of Southern Portugal near the town of Evora, field examinations revealed the presence of Tertiary sedimentary deposits that had the consistency of Duricrusts. These Duricrusts, occurring close to the land surface, were examined in the field as well as in the laboratory, with the objective of establishing their composition and formation. Micromorphological examinations showed that the Duricrusts were composed of clasts of fine sand to fine gravel sizes cemented together by a matrix dominated by either palygorskite or carbonate. The matrix : clasts ratio varied from about 1 : 3 when the cement was carbonate, to 3 : 1 or higher when the matrix was palygorskite. Occasionally the ratio in the latter was even higher. The clasts consisted of quartz, feldspar, and some Mg-rich metamorphic minerals. The palygorskite matrix fibres were arranged in mats within which they had parallel orientation. The mats or ‘domains’, which had a length of 15–25 sm and a width of about 40 sm, showed random orientation. In analogy to the term ‘calcrete’ the term ‘palycrete’ is used for the palygorskite Duricrusts. The palycrete, of an average thickness of 0.5 m, frequently rested directly on the Hercynian basement rocks, and was covered by a recent solum. In the B horizons of the solum, the palygorskite appeared to undergo recent weathering and transformation into smectite. The Duricrusts were proposed to have formed by authigenic calcite or palygorskite, which filled the interstices between clastic particles that had been deposited on Hercynian basement rocks following their peneplanation in the early Tertiary. The proposed environment of deposition and formation was that of an intermittent playa-lake in a semi-arid, seasonal climate, where strong evaporative processes had been active. Alteration and weathering of the mafic minerals contained in some of the clasts, in addition to interstitial solutions rich in Si and Mg, had created the chemical environment required for palygorskite neoformation. From the state of weathering–disintegration of the palygorskite in the soils formed on the palycrete, it is inferred that the environment for palygorskite neoformation had ceased to exist after palycrete formation.
Daniela Sauer - One of the best experts on this subject based on the ideXlab platform.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation. Materials and methods After studying an extensive number of road cuts in the field and mapping soil patterns in parts of the two basins by manual augering, ten pedons were selected for detailed description and sampling. Thin sections were analysed under a petrographic microscope, focusing on the micromorphology and optical properties of the cementing materials. Selected samples were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy to reconfirm the optical identification. The laboratory analyses included pH, carbonate contents, and X-ray diffraction analysis. Results and discussion The Duricrusts in the eastern Sado basin are indurated by silica. Combination of XRD and thin section analysis allowed to identify opal-CT as a major component, while opal-A is present to a lesser extent, and chalcedony is very rare. The cementing materials of the Duricrusts in the Oriola basin are palygorskite and calcite, which may occur alone or in combination within a soil profile. Conclusions The thick Duricrusts formed in the basins through precipitation of calcite, palygorskite and silica from lateral water flows, which ran from the Serra de Portel into the basins, during short moist seasons in a generally warm, semi-arid climate with strong evapotranspiration. Lithology of the upper catchment areas (element sources) and topography control the spatial distribution of the different Duricrusts. Their formation took place mainly during the Pliocene. Palygorskite transformation to smectite in the upper parts of the palycretes indicates that palygorskite is unstable in the present (more humid, typical Mediterranean) climate. This study demonstrates the potential role of lateral water and element transport in landscapes that need to be considered in pedological studies and concepts, and the use of mineral indicators of past climates such as palygorskite and the ageing stage of silica precipitations as tools for reconstructing environmental conditions and possible time of Duricrust formation.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation.
Mehdi Zarei - One of the best experts on this subject based on the ideXlab platform.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation. Materials and methods After studying an extensive number of road cuts in the field and mapping soil patterns in parts of the two basins by manual augering, ten pedons were selected for detailed description and sampling. Thin sections were analysed under a petrographic microscope, focusing on the micromorphology and optical properties of the cementing materials. Selected samples were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy to reconfirm the optical identification. The laboratory analyses included pH, carbonate contents, and X-ray diffraction analysis. Results and discussion The Duricrusts in the eastern Sado basin are indurated by silica. Combination of XRD and thin section analysis allowed to identify opal-CT as a major component, while opal-A is present to a lesser extent, and chalcedony is very rare. The cementing materials of the Duricrusts in the Oriola basin are palygorskite and calcite, which may occur alone or in combination within a soil profile. Conclusions The thick Duricrusts formed in the basins through precipitation of calcite, palygorskite and silica from lateral water flows, which ran from the Serra de Portel into the basins, during short moist seasons in a generally warm, semi-arid climate with strong evapotranspiration. Lithology of the upper catchment areas (element sources) and topography control the spatial distribution of the different Duricrusts. Their formation took place mainly during the Pliocene. Palygorskite transformation to smectite in the upper parts of the palycretes indicates that palygorskite is unstable in the present (more humid, typical Mediterranean) climate. This study demonstrates the potential role of lateral water and element transport in landscapes that need to be considered in pedological studies and concepts, and the use of mineral indicators of past climates such as palygorskite and the ageing stage of silica precipitations as tools for reconstructing environmental conditions and possible time of Duricrust formation.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation.
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Palygorskite-cemented crusts (palycretes) in Southern Portugal.
Soil Research, 2000Co-Authors: Karl Stahr, J. Trommler, K. H. Papenfuss, Mehdi Zarei, J Kuhn, Arieh SingerAbstract:In the Oriola depression of Southern Portugal near the town of Evora, field examinations revealed the presence of Tertiary sedimentary deposits that had the consistency of Duricrusts. These Duricrusts, occurring close to the land surface, were examined in the field as well as in the laboratory, with the objective of establishing their composition and formation. Micromorphological examinations showed that the Duricrusts were composed of clasts of fine sand to fine gravel sizes cemented together by a matrix dominated by either palygorskite or carbonate. The matrix : clasts ratio varied from about 1 : 3 when the cement was carbonate, to 3 : 1 or higher when the matrix was palygorskite. Occasionally the ratio in the latter was even higher. The clasts consisted of quartz, feldspar, and some Mg-rich metamorphic minerals. The palygorskite matrix fibres were arranged in mats within which they had parallel orientation. The mats or ‘domains’, which had a length of 15–25 sm and a width of about 40 sm, showed random orientation. In analogy to the term ‘calcrete’ the term ‘palycrete’ is used for the palygorskite Duricrusts. The palycrete, of an average thickness of 0.5 m, frequently rested directly on the Hercynian basement rocks, and was covered by a recent solum. In the B horizons of the solum, the palygorskite appeared to undergo recent weathering and transformation into smectite. The Duricrusts were proposed to have formed by authigenic calcite or palygorskite, which filled the interstices between clastic particles that had been deposited on Hercynian basement rocks following their peneplanation in the early Tertiary. The proposed environment of deposition and formation was that of an intermittent playa-lake in a semi-arid, seasonal climate, where strong evaporative processes had been active. Alteration and weathering of the mafic minerals contained in some of the clasts, in addition to interstitial solutions rich in Si and Mg, had created the chemical environment required for palygorskite neoformation. From the state of weathering–disintegration of the palygorskite in the soils formed on the palycrete, it is inferred that the environment for palygorskite neoformation had ceased to exist after palycrete formation.
Jürgen Kühn - One of the best experts on this subject based on the ideXlab platform.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation. Materials and methods After studying an extensive number of road cuts in the field and mapping soil patterns in parts of the two basins by manual augering, ten pedons were selected for detailed description and sampling. Thin sections were analysed under a petrographic microscope, focusing on the micromorphology and optical properties of the cementing materials. Selected samples were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy to reconfirm the optical identification. The laboratory analyses included pH, carbonate contents, and X-ray diffraction analysis. Results and discussion The Duricrusts in the eastern Sado basin are indurated by silica. Combination of XRD and thin section analysis allowed to identify opal-CT as a major component, while opal-A is present to a lesser extent, and chalcedony is very rare. The cementing materials of the Duricrusts in the Oriola basin are palygorskite and calcite, which may occur alone or in combination within a soil profile. Conclusions The thick Duricrusts formed in the basins through precipitation of calcite, palygorskite and silica from lateral water flows, which ran from the Serra de Portel into the basins, during short moist seasons in a generally warm, semi-arid climate with strong evapotranspiration. Lithology of the upper catchment areas (element sources) and topography control the spatial distribution of the different Duricrusts. Their formation took place mainly during the Pliocene. Palygorskite transformation to smectite in the upper parts of the palycretes indicates that palygorskite is unstable in the present (more humid, typical Mediterranean) climate. This study demonstrates the potential role of lateral water and element transport in landscapes that need to be considered in pedological studies and concepts, and the use of mineral indicators of past climates such as palygorskite and the ageing stage of silica precipitations as tools for reconstructing environmental conditions and possible time of Duricrust formation.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation.
Christine Stein - One of the best experts on this subject based on the ideXlab platform.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation. Materials and methods After studying an extensive number of road cuts in the field and mapping soil patterns in parts of the two basins by manual augering, ten pedons were selected for detailed description and sampling. Thin sections were analysed under a petrographic microscope, focusing on the micromorphology and optical properties of the cementing materials. Selected samples were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy to reconfirm the optical identification. The laboratory analyses included pH, carbonate contents, and X-ray diffraction analysis. Results and discussion The Duricrusts in the eastern Sado basin are indurated by silica. Combination of XRD and thin section analysis allowed to identify opal-CT as a major component, while opal-A is present to a lesser extent, and chalcedony is very rare. The cementing materials of the Duricrusts in the Oriola basin are palygorskite and calcite, which may occur alone or in combination within a soil profile. Conclusions The thick Duricrusts formed in the basins through precipitation of calcite, palygorskite and silica from lateral water flows, which ran from the Serra de Portel into the basins, during short moist seasons in a generally warm, semi-arid climate with strong evapotranspiration. Lithology of the upper catchment areas (element sources) and topography control the spatial distribution of the different Duricrusts. Their formation took place mainly during the Pliocene. Palygorskite transformation to smectite in the upper parts of the palycretes indicates that palygorskite is unstable in the present (more humid, typical Mediterranean) climate. This study demonstrates the potential role of lateral water and element transport in landscapes that need to be considered in pedological studies and concepts, and the use of mineral indicators of past climates such as palygorskite and the ageing stage of silica precipitations as tools for reconstructing environmental conditions and possible time of Duricrust formation.
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Duricrusts in soils of the Alentejo (southern Portugal)—types, distribution, genesis and time of their formation
Journal of Soils and Sediments, 2015Co-Authors: Daniela Sauer, Mehdi Zarei, Christine Stein, Stephan Glatzel, Jürgen Kühn, Karl StahrAbstract:Purpose This paper reports on extremely thick and massive Duricrusts in soils of two basins in the Alentejo (southern Portugal). Since different types of Duricrusts (calcretes, silcretes and palycretes) have been reported from other regions in the Mediterranean, the purpose of this study was to identify the cementing agents in the Duricrusts and to compare their composition in the two basins. Moreover, the study aimed at identifying the processes involved in Duricrust formation, and especially the role of topography and lateral water and element transport in the landscape, and drawing conclusions about environmental conditions and time of Duricrust formation.
