34 samples of loess-paleosol from the Luochuan and kifeng sections in the Loess Plateau, north-ern China were separated into sand, silt and clay fractions and analyzed for their mineral composi -tions. The results ind...34 samples of loess-paleosol from the Luochuan and kifeng sections in the Loess Plateau, north-ern China were separated into sand, silt and clay fractions and analyzed for their mineral composi -tions. The results indicate that there is almost no difference between loess and paleosol in mineralcomposition. Major mineral species are quartz, mica, feIdspar and chlorite, accounhng for about88-92% of the total, other minerals are kandite, smectite, vermiculite and a few heavy minerals. Thecalcite, magnetite and hematite were not taken into consideration because of their removal in the pro-cess of sample preparation. The main difference with respect to the mineral composition of samplescollected from different sections and different stratigraphic leveIs lies in the amount and grain sise ofminerals hosted. Comparisons between the Luochuan section and the kifeng section, between paleosoland loess and between the upper part and the lower part of some paleosol layers show that the for-mers contain less feldspar but more mica and vermiculite and are finer in grain sise, indicahng theco-occurrence of both biochemical weathering process responsible for mineral change and physicalweathering process leading to grain-stie change during the soiI-forming processes. This result favourssuch an explanation of the soi1-forming mechanism that loess deposition and paleosol developmentoccurred synchronously, though the rate of soil formation was greater than that of loess deposition,thus leading to soil development.展开更多
文摘34 samples of loess-paleosol from the Luochuan and kifeng sections in the Loess Plateau, north-ern China were separated into sand, silt and clay fractions and analyzed for their mineral composi -tions. The results indicate that there is almost no difference between loess and paleosol in mineralcomposition. Major mineral species are quartz, mica, feIdspar and chlorite, accounhng for about88-92% of the total, other minerals are kandite, smectite, vermiculite and a few heavy minerals. Thecalcite, magnetite and hematite were not taken into consideration because of their removal in the pro-cess of sample preparation. The main difference with respect to the mineral composition of samplescollected from different sections and different stratigraphic leveIs lies in the amount and grain sise ofminerals hosted. Comparisons between the Luochuan section and the kifeng section, between paleosoland loess and between the upper part and the lower part of some paleosol layers show that the for-mers contain less feldspar but more mica and vermiculite and are finer in grain sise, indicahng theco-occurrence of both biochemical weathering process responsible for mineral change and physicalweathering process leading to grain-stie change during the soiI-forming processes. This result favourssuch an explanation of the soi1-forming mechanism that loess deposition and paleosol developmentoccurred synchronously, though the rate of soil formation was greater than that of loess deposition,thus leading to soil development.
