Abstract Lower Cambrian carbonates of the Flinders Ranges, South Australia, feature a distinctive and laterally continuous hematitic horizon known as the Red Crust. Previously interpreted as a subaerial unconformity and major sequence boundary, we present conclusive paleontological and petrographic evidence that all occurrences of hematite are in the form of ferrimicrobialites constituting a component of the carbonate sediment. Newly described fossil assemblages including Gravestockia calcareous sponges, archaeocyaths and associated stereoplasm also indicate that deposition occurred in a shallow-water marine environment. The Red Crust is interpreted to reflect a widespread and dramatic shift to anoxic reducing conditions driven by ferruginous marine waters during the early Paleozoic, marking the oldest recognised Paleozoic oceanic anoxic event (OAE) of this type, coeval with the Cambrian explosion of life.

中文翻译：

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红壳：早期古生代海洋缺氧事件的证据

摘要 南澳大利亚弗林德斯山脉的下寒武统碳酸盐岩具有独特且横向连续的赤铁矿层，称为红地壳。以前被解释为地下不整合面和主要层序边界，我们提出了确凿的古生物学和岩相学证据，表明所有赤铁矿都以铁微生物岩的形式存在，构成了碳酸盐沉积物的一个组成部分。新描述的化石组合，包括 Gravestockia 钙质海绵、古细胞和相关的立体质体，也表明沉积发生在浅水海洋环境中。红地壳被解释为反映了在早古生代期间由含铁海水驱动的向缺氧还原条件的广泛而戏剧性的转变，