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六盘山寺口子水库下白垩统六盘山群乃家河组中发育了核形石,通过对其外部核心及纹层特征,以及核形石地球化学组分的研究,认为研究区核形石主要产于水动力较强的动荡水环境中,对捕捉和粘附碳酸钙质点作用相当明显,藻类自身的钙化和原地微生物引发的沉淀作用也可能是核形石的成因。经分析得到核形石的Sr/Ba值为4.87,CaO的含量达到了48.18%,总体上,研究区核形石在盐度高、温度较高、气候炎热、蒸发量大的干旱环境条件下形成。这些环境与研究区在该时期受燕山运动的影响,地壳整体抬升,湖盆发生萎缩的构造背景是相符的。
According to the study of its external core and striated features and the geochemical composition of the nuclei, it is believed that the main types of nuclei in the study area are nuclei In turbulent water environment with strong hydrodynamic force, the effect of trapping and adhering calcium carbonate particles is quite obvious. The calcification of algae and the sedimentation caused by in-situ microorganisms may also be the cause of formation of nucleolite. The results showed that the Sr / Ba value of the nuclei was 4.87, and the content of CaO was 48.18%. In general, the nuclei in the study area were under the conditions of high salinity, high temperature, hot climate and large evaporation form. Affected by the Yanshan movement during this period, these environments and the study area are consistent with the uplifting of the crust and the tectonic setting of the basin atrophy.