49 research outputs found
Multiperspective analysis of erosion tolerance
Erosion tolerance is the most multidisciplinary field of soil erosion research. Scientists have shown lack in ability to adequately analyze the huge list of variables that influence soil loss tolerance definitions. For these the perspectives of erosion made by farmers, environmentalists, society and politicians have to be considered simultaneously. Partial and biased definitions of erosion tolerance may explain not only the polemic nature of the currently suggested values but also, in part, the nonadoption of the desired levels of erosion control. To move towards a solution, considerable changes would have to occur on how this topic is investigated, especially among scientists, who would have to change methods and strategies and extend the perspective of research out of the boundaries of the physical processes and the frontiers of the academy. A more effective integration and communication with the society and farmers, to learn about their perspective of erosion and a multidisciplinary approach, integrating soil, social, economic and environmental sciences are essential for improved erosion tolerance definitions. In the opinion of the authors, soil erosion research is not moving in this direction and a better understanding of erosion tolerance is not to be expected in the near future
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Chronology and geochemistry of Taxinan basalts from the Tarim basin: evidence for Permian plume magmatism
A new K-Ar age of 289.6Ma has been obtained for Taxinan basalt in the southwest Tarim basin of the northwest China. This age is consistent with the Ar-Ar age of 290. 1Ma from the same sample. This dating confirms the formation age of the basalt is the Taxinan basaltic lavas are differentiated alkaline basalts, with ~45% and 4% MgO contents. The Taxinan basalts and Keping basalts in the inner Tarim basin have similar major element contents, rare earth element and trace elements spider patterns with enriched light rare earth elements, and elevated contents of other incompatible elements including the high field strength elements. However, the Taxinan basalts have higher and contents and total rare earth elements , and lower , and contents compared to the Keping basalts. Abundances of K, Rb, and Cs are variable and non-systematic, suggesting an important influence of alteration on the abundances of these elements. For more immobile elements, the Taxinan basalts have high Ti and low Zr/Nb ratios with high Nb contents , indicating derivation from enriched mantle sources. White there is not a pronounced Nb anomaly relative to La, the lavas have slightly low Nb/U and Ce/Pb suggesting either derivation from continental lithosphere or modest amounts of crustal contamination. The large volumes of eruptives combined with the enriched geochemical signature support the hypothesis that the Taxinan basalt was derived from plume volcanism, either from the plume itself or from melting of enriched lithospheric mantle that was heated and uplifted by ascending mantle plume. Based on the affinity between Taxinan and Keping basalts in time and composition, the areal distribution of the Permian basalts in Tarim basin can be extended to the southwest part from the Tazhong-Keping of the inner area of Tarim basin.Earth and Planetary Science