钻孔岩心黏土混浊水电导率、黄铁矿、pH相关性分析及其在古沉积环境复原的应用:以渤海湾西岸平原DC01孔为例

为探讨复原海岸平原沉积环境和精确划分海陆相地层的有效方法，对渤海湾西岸海河以南平原深达30 m的DC01孔岩心以约20 cm间距取样，测试黏土混浊水电导率（EC）、黄铁矿质量分数（w（FeS₂））和pH值，并开展相关分析研究。结果显示，EC与w（FeS₂）正相关（相关系数r为0.47），而EC与pH以及w（FeS₂）与pH均负相关（r分别为-0.43和-0.52）。根据EC值的大小将DC01孔自下至上分成5个带（Ⅰ—Ⅴ），进一步分别对5个带的EC、w（FeS₂）及pH做相关分析，结果显示，Ⅱ带相关性最为突出：EC与w（FeS₂）的相关系数为0.83，极强正相关；EC与pH的相关系数为-0.77，强负相关；w（FeS₂）与pH的相关系数为-0.45，呈中等程度负相关。根据Ⅱ带的EC和w（FeS₂）极强正相关、且EC和w（FeS₂）均明显偏高以及多发育黑色泥炭和腐殖质黏土等特征，推断Ⅱ带为受海水影响的盐沼环境；结合AMS¹⁴C测年结果，推测8 260~7 470 cal.B.P.期间，海水曾经影响到DC01孔的位置。另外，Ⅳ带的EC值也偏高，但w（FeS₂）却较低，其EC与w（FeS₂）的相关系数为-0.03，不呈正相关关系，其原因是因为接近地表的上部沉积物因淋溶作用，在Ⅳ带形成淀积层导致EC异常偏高；最上层的Ⅴ带为淋溶层，这样就导致钻孔上部（深6.7 m以上）Ⅳ带和Ⅴ带EC与w（FeS₂）的相关性出现异常。因此在讨论沉积物上部沉积环境时，将EC与w（FeS₂）综合分析可以更精确地划分钻孔岩心的沉积环境。

Correlation Analysis of Conductivity (EC), w(FeS2), pH of Drilled Clay Water and Its Application in Paleo-Environment Restoration: A Case Study of DC01 Core on West Plain of Bohai Bay

In order to explore the effective method for the reconstruction of the ancient environment of coastal plains and accurately divide the marine and continental stratum, the core DC01(30 m depth) was taken from the south of the Haihe River in the west plain of the Bohai Bay,and sampled at intervals of 20 cm;The electric conductivity (EC), w(FeS₂) and pH were measured, and the correlations between EC and pH, w(FeS₂) and pH were analyzed. The results show that EC is positively correlated with w(FeS₂) (r=0.47), while EC is negatively correlated with pH, and so is w (FeS₂) (r=-0.43 and -0.52, respectively). According to the EC value, the core DC01 was divided into five bands from bottom to top, and the correlations between EC, w(FeS₂) and pH were further analyzed. The results show that the correlation of band Ⅱ is most obvious, and its EC is positively correlated with w(FeS₂) (r=0.83), but strongly negatively correlated with pH(r=-0.77), while w(FeS₂) is moderately negatively correlated with pH (r=-0.45). According to the strong positive correlation between EC and w(FeS₂), the high EC, w(FeS₂) and abundant black peat and humus clay, we can infer that the band Ⅱ was developed in a salt marsh environment close to the seawater. Combined with the AMS¹⁴C dating result, seawater once affected this position during the period of 8 260-7 470 cal. B. P. In band Ⅳ, the EC is high, but w(FeS₂) is very low, and the correlation between EC and w(FeS₂) is negative(r=-0.03), such a pattern was caused by the leaching effect of the upper surface sediments. The uppermost band Ⅴ(6.7 m on top) is a leaching layer, therefore its correlation between EC and w(FeS₂) is abnormal. Obviously, a comprehensive analysis of EC and w(FeS₂) can give a more reliable result for the discussion of the upper sedimentary environment of a drilling core.