Casts and molds of soft-bodied organisms in Ediacaran sandstones (“Ediacara-style” fossilization) have played an important role in reconstruction of the emergence and radiation of early complex macroscopic life. However, the preservational processes responsible for the Ediacara fossil record are still vigorously debated. Whereas classic studies proposed fossilization via rapid sulfide mineralization of carcass and matground surfaces, a more recent view posits silica as the key mineral involved in their preservation. We performed experiments in which a variety of soft-bodied organisms were exposed to silica-rich solutions at concentrations considered characteristic of Ediacaran seawater (2 mM). Our results document continuous precipitation of amorphous silica onto the surfaces of these organic tissues under constant and normal marine pH values (7.8). Mineral formation was accompanied by a progressive decrease in the dissolved silica (DSi) concentration of the experimental solution to levels well below amorphous silica saturation. Additionally, we find that the magnitude of silica precipitation is correlated to each organism’s functional-group chemistry, as measured by potentiometric acid-base titrations. We suggest that a wide range of soft-bodied organisms were prone to silicification in Ediacaran marine environments characterized by anactualistically high DSi concentrations. This provides further support for the model that the extraordinary moldic preservation of the Ediacara Biota was promoted by early silica cementation and that this mode of preservation can offer an accurate glimpse into the composition of those early animal ecosystems.

中文翻译：

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实验证据支持埃迪卡拉生物群的早期二氧化硅胶结

Ediacaran砂岩中的软生物的铸模（“ Ediacara型”化石）在重建早期复杂的宏观生命的出现和辐射中起了重要作用。但是，有关埃迪卡拉藻化石记录的保存过程仍在激烈辩论。尽管经典的研究提出通过via体和地表表面的快速硫化物矿化来进行化石，但最近的观点认为二氧化硅是参与其保存的关键矿物。我们进行了一些实验，在这些实验中，各种软体动物都以被认为具有Ediacaran海水（2 mM）特征的浓度暴露于富含二氧化硅的溶液中。我们的研究结果表明，在恒定和正常的海洋pH值下，无定形二氧化硅连续沉淀在这些有机组织的表面上（7。8）。矿物的形成伴随着实验溶液中溶解二氧化硅（DSi）浓度的逐渐降低至远低于无定形二氧化硅饱和度的水平。此外，我们发现，通过电位酸碱滴定法测量，二氧化硅沉淀的程度与每个生物的官能团化学性质相关。我们建议，以特征性的高DSi浓度为特征的Ediacaran海洋环境中，各种各样的软生物很容易硅化。这为早期的硅酸盐胶结促进了埃迪卡拉生物群的非常规霉菌保存提供了进一步的支持，并且这种保存方式可以准确地了解那些早期动物生态系统的组成。矿物的形成伴随着实验溶液中溶解二氧化硅（DSi）浓度的逐渐降低至远低于无定形二氧化硅饱和度的水平。此外，我们发现，通过电位酸碱滴定法测量，二氧化硅沉淀的程度与每个生物的官能团化学性质相关。我们建议，以特征性的高DSi浓度为特征的Ediacaran海洋环境中，各种各样的软生物很容易硅化。这为早期的硅酸盐胶结促进了埃迪卡拉生物群的非常规霉菌保存提供了进一步的支持，并且这种保存方式可以准确地了解那些早期动物生态系统的组成。矿物的形成伴随着实验溶液中溶解二氧化硅（DSi）浓度的逐渐降低至远低于无定形二氧化硅饱和度的水平。此外，我们发现，通过电位酸碱滴定法测量，二氧化硅沉淀的程度与每个生物的官能团化学性质相关。我们建议，以特征性的高DSi浓度为特征的Ediacaran海洋环境中，各种各样的软生物很容易硅化。这为早期的硅酸盐胶结促进了埃迪卡拉生物群的非常规霉菌保存提供了进一步的支持，并且这种保存方式可以准确地了解那些早期动物生态系统的组成。