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我国黄土高原的黄土-古土壤序列是干旱-半干旱气候条件下的产物,富含碳酸盐物质.这些碳酸盐矿物一部分是由风力从源区带来的(原生碳酸盐),另一部分则是在风化成壤阶段形成的(次生碳酸盐).近年来利用黄土-古土壤中碳酸盐同位素组成追索我国黄土高原末次间冰期以来的古气候变迁,已经引起了一些研究者的注意.然而,由于已有的研究采用全岩样品,所得的分析结果可能包含了不同比例的原生碳酸盐的混合,使分析结果的解释复杂化.因此很需要对较纯的次生碳酸盐同位素组成作细致分析以求更加可信的数据.黄土高原中部的S_1古土壤是末次间冰期的产物.其中发育有清晰可辨的次生碳酸盐胶膜和菌丝体,是研究黄土高原中部末次间冰期古气候和古生态的极好样品.为此,我们选择洛川、西峰和段家坡3个采样点从中挑选出较纯的次生碳酸盐胶膜作对比研究.其目的是:(1)测定黄土剖面古土壤中纯次生碳酸盐的稳定同位素组成;(2)对土壤碳酸盐C,O同位素组成与古季风的关系作一初步探讨.
The Loess-Paleosol sequence in the Loess Plateau of China is a product of arid-semi-arid climatic conditions and is rich in carbonate minerals, some of which are derived from the source zone (primary carbonate) by wind and another (Secondary carbonate) formed in the weathered and pedigree stage.In recent years, the use of carbonate isotope composition in the loess-paleosol to track the paleoclimate changes since the last interglacial period of the Loess Plateau in China has led to some studies However, due to the use of whole-rock samples in previous studies, the analysis results obtained may contain different proportions of primary carbonate mixtures that complicate the interpretation of analytical results.Therefore, Carbonate isotope composition for detailed analysis in order to obtain more credible data.Central Loess Plateau S_1 ancient soil is the product of the last interglacials, which developed a clear and identifiable secondary carbonate film and mycelium, is To study the excellent samples of the paleoclimate and palaeoclimate of the last interglacial period in the central part of the Loess Plateau, we selected the relatively pure secondary carbonate films from three sampling points of Luochuan, Xifeng and Duanjiapo for comparative study .its It is: (1) determining a cross-sectional loess palaeosol secondary pure stable isotope carbonate composition; (2) soil carbonates C, O isotopic composition of a preliminary study for the relationship PALEOMONSOON.