The carbon isotopic (δ13C) composition of shallow-water carbonates often is interpreted to reflect the δ13C of the global ocean and is used as a proxy for changes in the global carbon cycle. However, local platform processes, in addition to meteoric and marine diagenesis, may decouple carbonate δ13C from that of the global ocean. We present new δ13C measurements of benthic foraminifera, solitary corals, calcifying green algae, ooids, coated grains, and lime mud from the modern Great Bahama Bank. We find that vital effects, cross-shelf seawater chemistry gradients, and meteoric diagenesis produce carbonate with δ13C variability rivaling that of the past two billion years of Earth history. Leveraging Walther's Law, we illustrate how these local δ13C signals can find their way into the stratigraphic record of bulk carbonate.

中文翻译：

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大巴哈马海岸碳酸盐岩δ13C的相控

浅水碳酸盐的碳同位素 (δ13C) 组成通常被解释为反映全球海洋的 δ13C，并被用作全球碳循环变化的代表。然而，除了大气和海洋成岩作用外，局部平台过程可能会使碳酸盐 δ13C 与全球海洋的碳酸盐岩脱钩。我们展示了来自现代大巴哈马银行的底栖有孔虫、孤珊瑚、钙化绿藻、鲕类、覆膜谷物和石灰泥的新 δ13C 测量值。我们发现重要的影响、跨大陆架海水化学梯度和大气成岩作用产生的碳酸盐具有与过去 20 亿年地球历史相媲美的 δ13C 变异性。利用瓦尔特定律，我们说明了这些局部 δ13C 信号如何进入大块碳酸盐的地层记录。