The Experts below are selected from a list of 609 Experts worldwide ranked by ideXlab platform
R W Payton - One of the best experts on this subject based on the ideXlab platform.
-
fragipan formation in argillic brown earths fragiudalfs of the milfield plain north east england ii post devensian developmental processes and the origin of fragipan consistence
European Journal of Soil Science, 1993Co-Authors: R W PaytonAbstract:SUMMARY Pedogenetic processes following a permafrost stage of development in four argillic brown earths with fragipans (Glossic and Ochreptic Fragiudalfs) are investigated by soil microscopy, including SEM observations of unimpregnated soil material, and by determination of clay mineralogy. Micromorphology of the apparently massive fragipan confirms both the presence of subhorizontal fissures infilled with illuvial deposits separating dense lenticular structures formed by ice-lens growth, and former vertical fissures formed by dessication on freezing with subsequent widening by ice-vein development. The firmness and brittle failure of the fragipans are attributed to a closely-packed, well-graded matrix of skeleton grains bonded by clay bridges consisting of non-swelling illite and chlorite and to weak interconnection of macrovoids. Weak cementation is rejected as an explanation of fragipan consistence. Sequential stages of particle translocation have been critical to fragipan formation. High bulk density is attributed not only to irregular compression and contraction of the soil matrix under permafrost conditions but also to the infilling of voids by illuvial silt and clay. The full development of the fragipans has depended on Flandrian clay migration which has contributed to clay-bridge formation, void infilling and localized seasonal impedance of drainage resulting in Eluviation of iron oxides, the development of grey polygonal patterning, and processes of degradation at the pan surface leading to glossic features.
-
fragipan formation in argillic brown earths fragiudalfs of the milfield plain north east england ii post devensian developmental processes and the origin of fragipan consistence
European Journal of Soil Science, 1993Co-Authors: R W PaytonAbstract:SUMMARY Pedogenetic processes following a permafrost stage of development in four argillic brown earths with fragipans (Glossic and Ochreptic Fragiudalfs) are investigated by soil microscopy, including SEM observations of unimpregnated soil material, and by determination of clay mineralogy. Micromorphology of the apparently massive fragipan confirms both the presence of subhorizontal fissures infilled with illuvial deposits separating dense lenticular structures formed by ice-lens growth, and former vertical fissures formed by dessication on freezing with subsequent widening by ice-vein development. The firmness and brittle failure of the fragipans are attributed to a closely-packed, well-graded matrix of skeleton grains bonded by clay bridges consisting of non-swelling illite and chlorite and to weak interconnection of macrovoids. Weak cementation is rejected as an explanation of fragipan consistence. Sequential stages of particle translocation have been critical to fragipan formation. High bulk density is attributed not only to irregular compression and contraction of the soil matrix under permafrost conditions but also to the infilling of voids by illuvial silt and clay. The full development of the fragipans has depended on Flandrian clay migration which has contributed to clay-bridge formation, void infilling and localized seasonal impedance of drainage resulting in Eluviation of iron oxides, the development of grey polygonal patterning, and processes of degradation at the pan surface leading to glossic features.
Fei Zhang - One of the best experts on this subject based on the ideXlab platform.
-
pedogenic processes in loess paleosol sediments clues from li isotopes of leachate in luochuan loess
Geochimica et Cosmochimica Acta, 2021Co-Authors: Fei Zhang, Zhangdong Jin, Jibao Dong, Chunyao Liu, Jun XiaoAbstract:Abstract Tracing pedogenic processes is fundamental for reconstructing climatic and environmental changes using loess deposits. Lithium isotopes can serve as a sensitive tracer to unravel these processes, owing to its active behaviors without effect by redox and biological reactions. This study investigated the Li contents and δ7Li values of leachate and residue ([Li]leachate, [Li]residue, δ7Lileachate and δ7Liresidue) of the upper 12.5 m Luochuan loess-paleosol sediment (since the last interglacial) on the Chinese Loess Plateau, in order to better understand pedogenic processes in loess. The [Li]leachate, varying from 0.39 to 1.97 μg/g, is mainly derived from the adsorption phase, with a significant variation in δ7Lileachate, from −6.55‰ to +12.88‰. Both [Li]leachate and δ7Lileachate variations reflect weathering and adsorption processes during different periods. The [Li]residue vary from 34.4 to 46.3 μg/g (averaging 38.4 μg/g) and their δ7Liresidue vary from −3.66‰ to +2.44‰ (averaging −0.22 ± 1.68‰), both in agreement with the upper continental crust values. At initial stage after loess deposited (stage I), high [Li]leachate but low δ7Lileachate are results of preferential adsorption of 6Li by clays and migration of 7Li with soil solution during weathering and Eluviation processes. When overlying loess was deposited and experienced pedogenesis as the stage I, 7Li migrated downward and was adsorbed by clays (stage II), resulting in high [Li]leachate and δ7Lileachate in underlying loess. When loess has superimposed pedogenic and adsorption processes as the stages I and II, loess became as paleosol with highest δ7Lileachate in underlying carbonate accumulation layer. A persistent increase in δ7Lileachate indicates dominant control of post-depositional adsorptions on Li fractionation along solution migrations during weathering and Eluviation of overlying deposits, and vice versa. These results highlight that variations in [Li]leachate and δ7Lileachate can be used to trace soil water migration processes and the magnitude of pedogenic processes in loess-paleosol sediment at different periods.
Zhangdong Jin - One of the best experts on this subject based on the ideXlab platform.
-
pedogenic processes in loess paleosol sediments clues from li isotopes of leachate in luochuan loess
Geochimica et Cosmochimica Acta, 2021Co-Authors: Fei Zhang, Zhangdong Jin, Jibao Dong, Chunyao Liu, Jun XiaoAbstract:Abstract Tracing pedogenic processes is fundamental for reconstructing climatic and environmental changes using loess deposits. Lithium isotopes can serve as a sensitive tracer to unravel these processes, owing to its active behaviors without effect by redox and biological reactions. This study investigated the Li contents and δ7Li values of leachate and residue ([Li]leachate, [Li]residue, δ7Lileachate and δ7Liresidue) of the upper 12.5 m Luochuan loess-paleosol sediment (since the last interglacial) on the Chinese Loess Plateau, in order to better understand pedogenic processes in loess. The [Li]leachate, varying from 0.39 to 1.97 μg/g, is mainly derived from the adsorption phase, with a significant variation in δ7Lileachate, from −6.55‰ to +12.88‰. Both [Li]leachate and δ7Lileachate variations reflect weathering and adsorption processes during different periods. The [Li]residue vary from 34.4 to 46.3 μg/g (averaging 38.4 μg/g) and their δ7Liresidue vary from −3.66‰ to +2.44‰ (averaging −0.22 ± 1.68‰), both in agreement with the upper continental crust values. At initial stage after loess deposited (stage I), high [Li]leachate but low δ7Lileachate are results of preferential adsorption of 6Li by clays and migration of 7Li with soil solution during weathering and Eluviation processes. When overlying loess was deposited and experienced pedogenesis as the stage I, 7Li migrated downward and was adsorbed by clays (stage II), resulting in high [Li]leachate and δ7Lileachate in underlying loess. When loess has superimposed pedogenic and adsorption processes as the stages I and II, loess became as paleosol with highest δ7Lileachate in underlying carbonate accumulation layer. A persistent increase in δ7Lileachate indicates dominant control of post-depositional adsorptions on Li fractionation along solution migrations during weathering and Eluviation of overlying deposits, and vice versa. These results highlight that variations in [Li]leachate and δ7Lileachate can be used to trace soil water migration processes and the magnitude of pedogenic processes in loess-paleosol sediment at different periods.
Jibao Dong - One of the best experts on this subject based on the ideXlab platform.
-
pedogenic processes in loess paleosol sediments clues from li isotopes of leachate in luochuan loess
Geochimica et Cosmochimica Acta, 2021Co-Authors: Fei Zhang, Zhangdong Jin, Jibao Dong, Chunyao Liu, Jun XiaoAbstract:Abstract Tracing pedogenic processes is fundamental for reconstructing climatic and environmental changes using loess deposits. Lithium isotopes can serve as a sensitive tracer to unravel these processes, owing to its active behaviors without effect by redox and biological reactions. This study investigated the Li contents and δ7Li values of leachate and residue ([Li]leachate, [Li]residue, δ7Lileachate and δ7Liresidue) of the upper 12.5 m Luochuan loess-paleosol sediment (since the last interglacial) on the Chinese Loess Plateau, in order to better understand pedogenic processes in loess. The [Li]leachate, varying from 0.39 to 1.97 μg/g, is mainly derived from the adsorption phase, with a significant variation in δ7Lileachate, from −6.55‰ to +12.88‰. Both [Li]leachate and δ7Lileachate variations reflect weathering and adsorption processes during different periods. The [Li]residue vary from 34.4 to 46.3 μg/g (averaging 38.4 μg/g) and their δ7Liresidue vary from −3.66‰ to +2.44‰ (averaging −0.22 ± 1.68‰), both in agreement with the upper continental crust values. At initial stage after loess deposited (stage I), high [Li]leachate but low δ7Lileachate are results of preferential adsorption of 6Li by clays and migration of 7Li with soil solution during weathering and Eluviation processes. When overlying loess was deposited and experienced pedogenesis as the stage I, 7Li migrated downward and was adsorbed by clays (stage II), resulting in high [Li]leachate and δ7Lileachate in underlying loess. When loess has superimposed pedogenic and adsorption processes as the stages I and II, loess became as paleosol with highest δ7Lileachate in underlying carbonate accumulation layer. A persistent increase in δ7Lileachate indicates dominant control of post-depositional adsorptions on Li fractionation along solution migrations during weathering and Eluviation of overlying deposits, and vice versa. These results highlight that variations in [Li]leachate and δ7Lileachate can be used to trace soil water migration processes and the magnitude of pedogenic processes in loess-paleosol sediment at different periods.
Jun Xiao - One of the best experts on this subject based on the ideXlab platform.
-
pedogenic processes in loess paleosol sediments clues from li isotopes of leachate in luochuan loess
Geochimica et Cosmochimica Acta, 2021Co-Authors: Fei Zhang, Zhangdong Jin, Jibao Dong, Chunyao Liu, Jun XiaoAbstract:Abstract Tracing pedogenic processes is fundamental for reconstructing climatic and environmental changes using loess deposits. Lithium isotopes can serve as a sensitive tracer to unravel these processes, owing to its active behaviors without effect by redox and biological reactions. This study investigated the Li contents and δ7Li values of leachate and residue ([Li]leachate, [Li]residue, δ7Lileachate and δ7Liresidue) of the upper 12.5 m Luochuan loess-paleosol sediment (since the last interglacial) on the Chinese Loess Plateau, in order to better understand pedogenic processes in loess. The [Li]leachate, varying from 0.39 to 1.97 μg/g, is mainly derived from the adsorption phase, with a significant variation in δ7Lileachate, from −6.55‰ to +12.88‰. Both [Li]leachate and δ7Lileachate variations reflect weathering and adsorption processes during different periods. The [Li]residue vary from 34.4 to 46.3 μg/g (averaging 38.4 μg/g) and their δ7Liresidue vary from −3.66‰ to +2.44‰ (averaging −0.22 ± 1.68‰), both in agreement with the upper continental crust values. At initial stage after loess deposited (stage I), high [Li]leachate but low δ7Lileachate are results of preferential adsorption of 6Li by clays and migration of 7Li with soil solution during weathering and Eluviation processes. When overlying loess was deposited and experienced pedogenesis as the stage I, 7Li migrated downward and was adsorbed by clays (stage II), resulting in high [Li]leachate and δ7Lileachate in underlying loess. When loess has superimposed pedogenic and adsorption processes as the stages I and II, loess became as paleosol with highest δ7Lileachate in underlying carbonate accumulation layer. A persistent increase in δ7Lileachate indicates dominant control of post-depositional adsorptions on Li fractionation along solution migrations during weathering and Eluviation of overlying deposits, and vice versa. These results highlight that variations in [Li]leachate and δ7Lileachate can be used to trace soil water migration processes and the magnitude of pedogenic processes in loess-paleosol sediment at different periods.