渤海湾西岸几种地球化学的环境指标

摘要

为了探讨渤海湾西岸全新世地层的古环境,本文进行了多种地球化学环境指标的分析,在此,将指示不同环境的指标进行了分项(或归类)如:古气候、氧化-还原、海-陆相环境指标等；并将其分别进行R型聚类分析和散点分析(获得了元素指标的相关系数及聚散特征).具体分析结果为:①古气候指标:如图2所示,古温度值与Rb/Sr比值呈正相关关系,相关系数为+0.927,而CaCO3含量与古温度值、Rb/Sr比值二项指标则呈较大的负相关关系,相关系数为-0.721,表明CaCO3较高含量的寒冷期时而古温度值的负值也往往随之变大.②氧化-还原指标:如图4,显示出了Fe2+/Fe3+比值与Corg/P2O5比值有较大的聚敛性.③海-陆相指标:如图5所示,Sr/Ba比值与B/Ga比值呈正相关关系,相关系数为+0.946,而Ca/(Ca+Fe)比值与Sr/Ba比值、B/Ga比值二项指标也显示出了较大的正相关性,相关系数为+0.894;而B的古盐度SP值和Rb/K比值此二项指标与Sr/Ba比值、B/Ga比值、Ca/(Ca+Fe)比值等这三项指标呈负相关关系,相关系数分别为-0.792及-0.632.④通过最优分割分析(按照本文中一定的“方法原则”)以及统计分析,划分出了:第Ⅰ-第V气候冷段、第Ⅰ-第V还原带、及其海平面升降波动曲线:第Ⅰ-第Ⅶ段),如图3显示出大致的规律为:气候冷期时往往处于还原环境,与此同时,海平面则呈波动下降趋势.%Several geochemical indexes were exaimized to find out the paleoenviroment evolution of the Holocene stratotype section on the west coast of Bohai Sea. These indexes, which are subgrouped to refer to various enviorments, such as paleoenviorment change, oxidation-reduction setting, and transformation environment of marine and terrestrial fades, were analyzed to obtain correlation coefficient and figure features using R-type convergent analysis, cluster analysis, and scatter plot The analytical results are: ① Paleoclimate index (Fig. 2) showing that paleotemperature values are in positive proportion to Rb/Sr ratios, with a correlation coefficient of + 0. 927, while CaCQ) contents are in distinct negative proportion to both paleotemperature values and Rb/Sr ratios, with a correlation coefficient of -0. 721, which indicates that paleotemperature negatively increased as content of CaCOs became high during chilly period. ② The oxidation-reduction indexes (Fig. 4) showing that Fe2+/Fe3+ ratios and Corg/P2O5 ratios have great convergent. ③ The indexes of transformation environment of marine and terrestrial facies (Fig. 5) showing that Sr/Ba ratios are in positive proportion to B/Ga ratio, with a correlation coefficient of +0. 946. While ratios of Sr/Ba and B/Ga are in positive proportion to Ca/(Ca+Fe) ratios, with a coefficient of +0. 894. Meanwhile, paleosalinity Sp and Rb/K ratios are in negative proportion to ratios of Sr/Ba, B/Ga, and Ca/(Ca+Fe), with correlation coefficients of -0. 729 and -0. 632. ④ Using optimal segmentation method and statistic analysis, this study classify three stages; cold climate stages from I to V, oxidation-reduction zoneS from Ⅰ to Ⅵ, and fluctuating graph of sea level ( from Ⅰ to Ⅶ), as shown in Fig. 3, which illustrates a reduction enviorment during cold enviorment, accompanied by sea level decreasing fluctuantly.