Throughout most of the sedimentary record, the marine carbon cycle is interpreted as being in isotopic steady state. This is most commonly inferred via isotopic reconstructions, where two export fluxes (organic carbon and carbonate) are offset by a constant isotopic fractionation of ~25 (termed ). Sedimentary deposits immediately overlying the Marinoan snowball Earth diamictites, however, stray from this prediction. In stratigraphic sections from the Ol Formation (Mongolia) and Sheepbed Formation (Canada), we observe a temporary excursion where the organic matter has anomalously heavy C and is grossly decoupled from the carbonate C. This signal may reflect the unique biogeochemical conditions that persisted in the aftermath of snowball Earth. For example, physical oceanographic modeling suggests that a strong density gradient caused the ocean to remain stratified for about 50,000 years after termination of the Marinoan snowball event, during which time the surface ocean and continental weathering consumed the large atmospheric CO₂ reservoir. Further, we now better understand how C records of carbonate can be post‐depostionally altered and thus be misleading. In an attempt to explain the observed carbon isotope record, we developed a model that tracks the fluxes and isotopic values of carbon between the surface ocean, deep ocean, and atmosphere. By comparing the model output to the sedimentary data, stratification alone cannot generate the anomalous observed isotopic signal. Reproducing the heavy C in organic matter requires the progressively diminishing contribution of an additional anomalous source of organic matter. The exact source of this organic matter is unclear.

中文翻译：

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Marinoan雪球地球的后果是同位素异常的有机碳。

在大多数沉积记录中，海洋碳循环被解释为处于同位素稳态。这通常是通过同位素重建来推断的，其中两个出口通量（有机碳和碳酸盐）被〜25的恒定同位素分馏所抵消（称为）。然而，沉积物立即覆盖了马里诺斯雪球地球铁矾土，但偏离了这一预测。在来自Ol组（蒙古）和Sheedbed组（加拿大）的地层剖面中，我们观察到一个临时偏移，其中有机物具有异常重的C，并且与碳酸盐完全脱钩。C.该信号可能反映了雪球地球之后持续存在的独特生物地球化学条件。例如，物理海洋学建模表明，强烈的密度梯度导致海洋在Marinoan雪球事件终止后仍保持分层约50,000年，在此期间，表层海洋和大陆风化消耗了大量的大气CO ₂储层。此外，我们现在更好地了解碳酸盐的C记录可能会在后期发生变化，从而产生误导。为了解释观察到的碳同位素记录，我们开发了一个模型，该模型可以跟踪地表海洋，深海和大气之间的碳通量和同位素值。通过将模型输出与沉积数据进行比较，仅分层就不能产生异常的观测到的同位素信号。要在有机质中生产重碳，就需要逐渐减少其他有机质异常源的贡献。这种有机物的确切来源尚不清楚。