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中国沙漠 ›› 2023, Vol. 43 ›› Issue (3): 152-159.DOI: 10.7522/j.issn.1000-694X.2023.00003

• • 上一篇    

鄱阳湖沙山两处具有平行层理砂层的粒度分析及其对沉积环境的指示意义

李琦炜(), 龚志军(), 罗明, 彭花明, 王瀚, 王威   

  1. 东华理工大学 地球科学学院,江西 南昌 330013
  • 收稿日期:2022-10-08 修回日期:2023-02-11 出版日期:2023-05-20 发布日期:2023-05-31
  • 通讯作者: 龚志军
  • 作者简介:龚志军(E-mail: 13697082584@163.com
    李琦炜(1997—),男,山西太原人,硕士研究生,研究方向为第四纪地质学。E-mail: tynlqw@126.com
  • 基金资助:
    国家自然科学基金地区科学基金项目(42062013);地震灾害科学研究与科学普及项目(G20200002);江西省教育厅科学技术研究资助项目(GJJ160573);东华理工大学核资源与环境重点实验室开放基金项目(NRE1607)

Grain size analysis of two sand layers with parallel bedding in the sand hills around Poyang Lake and its implication for the sedimentary environment

Qiwei Li(), Zhijun Gong(), Ming Luo, Huaming Peng, Han Wang, Wei Wang   

  1. School of Earth Sciences,East China University of Technology,Nanchang 330013,China
  • Received:2022-10-08 Revised:2023-02-11 Online:2023-05-20 Published:2023-05-31
  • Contact: Zhijun Gong

摘要:

鄱阳湖是中国最大的淡水湖。目前,鄱阳湖周边分布着若干沙山,如湖口至彭泽一带沙山、吴城镇松门岛沙山等。此前研究多认为这些沙山为风力堆积的产物,特别是沙山的中上部。然而,我们通过野外调查发现,鄱阳湖周边沙山的中上部普遍保存有水成沉积构造的砂层/粉砂层,而且这些砂层/粉砂层的吴淞高程显著高于1949年以来鄱阳湖的最高水位(22.63 m,星子水文站)。本研究选取了鄱阳湖沙山两处代表性的具有平行层理的砂层为研究对象,并采集了两个样品开展粒度分析:一个样品(XZ-1)位于星子沙岭吴淞高程~36.5 m处,而另一个样品(HGDS-7)位于湖口县沙洲村沙山吴淞高程~40.3 m处。此次样品的粒度具有以下特征:(1)样品XZ-1分选性一般,而样品HGDS-7分选性差;(2)样品XZ-1粒度频率分布曲线有一个明显的主峰和一个不明显的次峰,而样品HGDS-7粒度频率分布曲线呈现明显的双峰型;(3)样品XZ-1和样品HGDS-7的概率累积曲线分别呈现六段式和八段式;(4)如采用萨胡判别公式进行计算,样品XZ-1与样品HGDS-7的Y值分别为3.71和8.89。以上粒度分析结果和沉积构造解译一致,即此次选取的两处具有平行层理的砂层均为水成沉积层。本研究表明虽然鄱阳湖周边沙山的中上部明显高于鄱阳湖自1949年以来的最高水位,但是这些沙山的中上部并不能全部解释为风成沉积物,至少有部分夹层是水成沉积过程的产物。未来需要在鄱阳湖不同沙山开展更多研究,以进一步论证这些沙山的成因,这一方面有利于了解鄱阳湖环境演变过程,另一方面为今后江西省鄱阳湖周边的供水安全、防洪安全和生态安全提供重要科学参考依据。

关键词: 鄱阳湖, 沙山, 平行层理, 粒度分析, 水成沉积物

Abstract:

Poyang Lake is the largest freshwater lake in China. At present, there are several sand hills around Poyang Lake, such as sand hills from Hukou county to Pengze county as well as Songmen Island in Wucheng Town. Previous studies suggest that these sand hills were formed by aeolian process, especially for the middle-top part of the sand hills. However, by field investigation, it was found that several sand/silt layers in the middle-top part of sand hills around Poyang Lake exhibit clear water-lain sedimentary structures. It is interesting that the elevation of these sand/silt layers was significantly higher than the highest water level of Poyang Lake since 1949. In this study, two representative sand layers with parallel bedding were targeted and two bulk samples were collected for particle size analysis. One sand sample (XZ-1) is collected from a sand layer with the parallel bedding within Shaling (sand hill) in Lushan city. Currently, the Wusong elevation of sand sample (XZ-1) is ~36.5 m. The other sand sample (HGDS-7) is collected from another sand layer with parallel bedding within a sand hill at Shazhou village in Hukou county. Currently, the Wusong elevation of sand sample (HGDS-7) is ~40.3 m. The results are as following: (1) Sand sample XZ-1 is moderately sorted, while sand sample HGDS-7 is poorly sorted. (2) The frequency curve of XZ-1 exhibits one main peak and a small peak, while that of HGDS-7 exhibits bimodal characteristics. (3) The log-probability accumulative curve of XZ-1 can be fitted by six distinctive populations, while the log-probability accumulative curve of HGDS-7 can be fitted by eight distinctive populations. (4) If the Sahu discriminant function is applied, Y value of XZ-1 is calculated at 3.71, while Y value of HGDS-7 is calculated at 8.89. The above particle size results are consistent with the interpretations by sedimentary structure, i.e. the targeted sand layers within the sand hills should be interpreted as water-lain sediments, rather than aeolian sediments, even though the targeted sand layers are much higher than the highest water level of Poyang Lake since 1949. In the future, more research should be carried out at different sand hills around Poyang Lake, to further understand the formation of the sand hills. It not only helps us better understand the evolution of Poyang Lake, but also be very useful for government policy on sustainable water supply, flood control and ecological safety on Poyang Lake.

Key words: Poyang Lake, sand hill, parallel bedding, grain-size analysis, water-lain sediments

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