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21.
陕西洛川黄土剖面中的黄土层及古土壤层中脂肪酸存在显著差异:黄土层中的正构脂肪酸以不对称的双峰分布,前峰高于后峰,C16:0为主峰;古土壤层中,脂肪酸以三组峰分布,C9,C16,C28近乎相等;古土壤层中的异构脂肪酸有iC17,iC19,反异构脂肪酸有aiC14,aiC15,aIC17,aiC20等,黄土层中几乎不见它们的,均含有C16;1,C18:1不饱和脂肪酸,其中C18;1含量高。L2,S2的 相似文献
22.
The occurrence of red desert soil profiles developed on Nubian Sandstone in the Libyan Sahara is discussed. From an examination of profile morphology in the field and the position of the soils at 970 m on an old land surface, it would be possible to regard them as desert paleosols formed under a previous humid climatic phase during the Quaternary. However, an investigation of the mineralogy of the soils and the underlying parent rocks strongly suggests that the properties of the soils are largely dependent on the parent material. Both have identical patterns of kaolinite content, haematite as the main ferric oxide, and similar proportions of quartz silt and coarse quartz sand. Therefore, the use of kaolinite and ferric oxides in interpreting past soil-forming climates in arid regions needs to be carried out with caution, for in the present case such an interpretation would be unreliable. 相似文献
23.
Based on field investigations, laboratory analyses and 14C dating, this paper discusses the laws of the formation and development of the paleosols in the northeast region of the Qinghai-Xizang
Plateau since Late Pleistocene. The authors reconstruct basic conditions of climate, vegetation, soil and natural zones during
the three periods in which the paleosols were formed, i.e. the last interglacial of the Late Pleistocene, warm stage of Late
Glacial and the Optimum of Holocene. Finally, this paper discusses the relationship between the paleosols and the uplift of
the Qinghai-Xizang Plateau. 相似文献
24.
Pedogenic needle-fiber calcite was studied regarding its morphology, texture and stable isotope composition from the paleosol of the Quaternary Várhegy travertine (Budapest, Hungary). The needle-fiber calcite is composed of 40–200 μm long monocrystals. Smooth rods as well as serrated-edged crystals with calcite overgrowths were identified by SEM. Needles have several textural varieties: randomly distributed crystals in vugs and pores with calcite hypocoatings, bundles of subparallel crystals forming coatings around grains and alveolar structure with bridging needles in vugs.The morphological study of needle-fiber calcite suggests that needles are calcified fungal sheaths and produced by fungal biomineralization, a common process in recent and fossil soils and calcretes. The stable isotope composition of needle-fiber calcite (average: δ18O=-7.1‰ and δ13C=-7.3‰ vs. V-PDB) indicates significant incorporation of organically derived CO2 and probably biological influence on needle genesis. Dissolved host rock travertine and/or atmospheric CO2 could also contribute some carbon to the acicular calcite. 相似文献