In an effort to constrain the mechanism of dolomitization in Neogene dolomites in the Bahamas and improve understanding of the use of chemostratigraphic tracers in shallow‐water carbonate sediments the δ³⁴S, Δ₄₇, δ¹³C, δ¹⁸O, δ^44/40Ca and δ²⁶Mg values and Sr concentrations have been measured in dolomitized intervals from the Clino core, drilled on the margin of Great Bahama Bank and two other cores (Unda and San Salvador) in the Bahamas. The Unda and San Salvador cores have massively dolomitized intervals that have carbonate associated sulphate δ³⁴S values similar to those found in contemporaneous seawater and δ^44/40Ca, δ²⁶Mg values, Sr contents and Δ₄₇ temperatures (25 to 30°C) indicating relatively shallow dolomitization in a fluid‐buffered system. In contrast, dolomitized intervals in the Clino core have elevated values of carbonate associated sulphate δ³⁴S values indicating dolomitization in a more sediment‐buffered diagenetic system where bacterial sulphate reduction enriches the residual in ³⁴S, consistent with high sediment Sr concentrations and low δ^44/40Ca and high δ²⁶Mg values. Only dolomites associated with hardgrounds in the Clino core have carbonate associated δ³⁴S values similar to seawater, indicating continuous flushing of the upper layers of the sediment by seawater during sedimentary hiatuses. This interpretation is supported by changes to more positive δ^44/40Ca values at hardground surfaces. All dolomites, whether they formed in an open fluid‐buffered or closed sediment‐buffered diagenetic system have similar δ²⁶Mg values suggesting that the HMC transformed to dolomite. The clumped isotope derived temperatures in the dolomitized intervals in Clino yield temperatures that are higher than normal, possibly indicating a kinetic isotope effect on dolomite Δ₄₇ values associated with carbonate formation through bacterial sulphate reduction. The findings of this study highlight the utility of applying multiple geochemical proxies to disentangle the diagenetic history of shallow‐water carbonate sediments and caution against simple interpretations of stratigraphic variability in these geochemical proxies as indicating changes in the global geochemical cycling of these elements in seawater.

中文翻译：

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巴哈马碳酸盐岩白云石化的地球化学指纹：来自硫，钙，镁和团聚同位素的证据

在努力限制在巴哈马新近系白云岩白云石化的机制，提高在浅水碳酸盐沉积物使用化学地层示踪剂的理解δ ³⁴ S，Δ ₄₇，δ ¹³ C，δ ¹⁸ O，δ ^40分之44 Ca和δ ²⁶ Mg的值和Sr浓度已经从Clino芯白云石化的间隔，上钻大巴哈马银行和在巴哈马其他两个芯（温达和圣萨尔瓦多）的边缘进行了测量。在温达和圣萨尔瓦多芯，正大量白云石化具有碳酸相关硫酸盐δ间隔³⁴的价值观类似于在同期海水和δ发现^40分之44钙，δ^26个Mg的值，锶含量和Δ ₄₇的温度（25〜30℃），其指示在流体缓冲系统相对浅的白云石化。与此相反，在Clino芯白云石化的间隔具有升高碳酸盐相关联的硫酸盐的值δ ^34个，其中细菌硫酸盐还原丰富的残余指示在多个沉积缓冲成岩系统白云石化的价值观在³⁴ S，具有高沉淀物的Sr浓度和低δ一致^40分之44 Ca和高δ ²⁶ Mg的值。仅白云石与所述Clino芯hardgrounds已经碳酸盐δ关联相关联的³⁴S值与海水相似，表明在沉积裂隙期间，海水不断冲洗沉积物的上层。硬质表面上^{更正的δ44/40} Ca值得到了这种解释的支持。所有白云石，它们是否处于打开流体缓冲或闭合沉积物缓冲成岩系统形成具有相似的δ ²⁶ Mg的值表明该HMC转化为白云石。结块的同位素衍生温度在Clino屈服温度是高于正常的白云石化的间隔，可能表明对白云石Δ一个动力学同位素效应₄₇与细菌硫酸盐还原形成碳酸盐有关的数值。这项研究的结果突出了应用多种地球化学代理来阐明浅水碳酸盐沉积物的成岩史的实用性，并警告不要对这些地球化学代理中的地层变异性进行简单解释，因为这表明了这些元素在海水中的全球地球化学循环的变化。