Two forms of carbon‐rich microfossils were discovered in the breccias of the Onaping Formation, Sudbury impact structure. The first form is represented by single particles scattered in the matrix of the breccias and included in the vesicles in altered glass. These particles are leaf‐shaped, stem‐shaped, tubular, and spherical objects ranging from 5–10 μm to 200–300 µm in size. It is suggested that algal flora inhabiting the ocean basin before the Sudbury impact was the source of plant material in the Onaping Formation. The second form of carbon‐rich microparticles in the Onaping Formation is represented by plant detritus in carbon‐bearing fragments of mudstones included in the breccia matrix. The microparticles in the mudstones are mainly ribbon‐like shreds from 3–5 µm to 200–300 µm long, while rare particles have more complex shapes. The matrix of the mudstones is a fine‐grained clay‐like substance with a network of micron‐wide open‐joint fissures. Contents of carbon in the mudstone matrix are 12–15 wt%. Muddy bottom sediments of the pre‐impact sea are supposed as a source of mudstone fragments in the breccias. Fragments of mudstones and carbon‐rich microparticles are an important source of organic carbon in the breccias of the Onaping Formation. Discovery of microfossils in the breccias of the Onaping Formation suggests the presence of a previously unknown complex algal flora that inhabited the pre‐impact sea before the impact event 1.85 billion years ago at the very end of the Paleoproterozoic.

中文翻译：

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加拿大萨德伯里撞击构造的元古代火山口充填角砾中保存的富碳微化石

在Onaping组的角砾岩中，Sudbury冲击结构发现了两种形式的富碳微化石。第一种形式由散布在角砾岩基质中的单个颗粒表示，并包含在蚀变玻璃中的囊泡中。这些颗粒是叶状，茎状，管状和球形物体，尺寸从5–10μm到200–300 µm。有人认为，在萨德伯里撞击之前居住在海盆中的藻类植物是奥那平组中植物材料的来源。Onaping组中第二种形式的富碳微粒以角砾岩基质中含泥碳的碎屑中的植物碎屑为代表。泥岩中的微粒主要是长3–5 µm至200–300 µm的带状碎片，而稀有粒子的形状更复杂。泥岩基质是一种细颗粒的粘土状物质，具有微米级的开缝裂隙网络。泥岩基质中的碳含量为12-15 wt％。撞击前海底泥泞的沉积物被认为是角砾岩中泥岩碎片的来源。泥石碎片和富碳微粒是奥那平组角砾岩中有机碳的重要来源。在Onaping组的角砾岩中发现了微化石，这表明存在着一个以前未知的复杂藻类植物，它在18.5亿年前的古元古代末期的撞击事件之前就居住在撞击前的海中。撞击前海底泥泞的沉积物被认为是角砾岩中泥岩碎片的来源。泥石碎片和富碳微粒是奥那平组角砾岩中有机碳的重要来源。在Onaping组的角砾岩中发现了微化石，这表明存在着一个以前未知的复杂藻类植物，它在18.5亿年前的古元古代末期的撞击事件之前就居住在撞击前的海中。撞击前海底泥泞的沉积物被认为是角砾岩中泥岩碎片的来源。泥石碎片和富碳微粒是奥那平组角砾岩中有机碳的重要来源。在Onaping组的角砾岩中发现了微化石，这表明存在着一个以前未知的复杂藻类植物，它在18.5亿年前的古元古代末期的撞击事件之前就居住在撞击前的海中。