冀中坳陷HS1钻孔沉积物粒度及其沉积环境

    Grain-size variation and sedimentary environment of HS1 borehole sediments in Jizhong Depression

    • 摘要: 对冀中坳陷HS1钻孔沉积物进行粒度分析,综合岩性、年代、生物标志等,探讨了3.5 Ma BP以来以冀中坳陷为代表的华北平原坳陷区的岩相古地理演化过程。结果表明,在新构造运动长期震荡式下降和气候不断变化的条件下,经流水作用改造依次经历了河流相与不稳定浅湖洼地相交替(上新世晚期)、河流相(早更新世)、河流相-片流相-短时洪泛相(中更新世)、河流相和泛滥平原相交替(晚更新世)、泛滥平原相(全新世)5个沉积演化阶段,且沉积物所处环境的水动力条件不断减弱,细颗粒组分不断增加。沉积物粒度颗粒组分含量与碳、氧同位素和孢粉所记录的气候变化具有同趋性,在寒冷干旱气候条件下细颗粒组分含量增加,而在温暖湿润的气候条件下粗颗粒组分含量增加;介于二者之间的气候条件下,沉积物的粒径变化较平缓,粒径区间范围较宽。粒度曲线反映的沉积环境的旋回性变化与孢粉、碳、氧同位素记录所划分的气候冷暖演化阶段耦合性较好,也与华北地区其他钻孔同时期相关记录较一致,这对重建区域古地理环境具有重要意义。

       

      Abstract: The grain size analysis of HS1 borehole sediments in the Jizhong Depression was carried out, and the lithofacies paleogeographic evolution process in the depression area of North China Plain represented by Jizhong Depression since 3.5 Ma BP was discussed by integrating lithology, age and biomarkers.The results demonstrate that under the conditions the long-term turbulent decline of the neotectonic movement and continuous climate change, the river facies and unstable shallow lake depression facies alternate (Late Pliocene), river facies (Early Pleistocene), river facies, sheet flow facies and short-term flood facies (Middle Pleistocene), river facies and flood plain facies alternate (Late Pleistocene), flood plain facies (Holocene) five sedimentary evolution stages, and the hydrodynamic conditions of the sediment environment are weakening, and the fine particle components are increasing.The grain size fraction content of sediments was consistent with the climate change recorded by carbon-oxygen isotope and pollen.The acceptable grain fraction content increased under cold and dry climate conditions, while the coarse grain fraction content increased under warm and humid climate conditions.Under the climate conditions between them, the change of sediment particle size is relatively gentle, and the particle size range is vast.The cyclic variation of the sedimentary environment reflected by the grain size curve is well coupled with the cold and warm evolution stages of climate divided by pollen and carbon and oxygen isotope records.It is also consistent with the relevant documents of other boreholes in the same period in North China, which is of great significance to reconstruct the paleogeographic environment in the region.

       

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