Fibrous‐radiating carbonate spherulites spatially associated with poorly crystalline Mg‐Si substances have formed within conical microbialites in modern hypersaline lakes on Rottnest Island, Western Australia. Two spherulitic fabrics can be distinguished based on compositional and textural differences. The oldest (lowermost) fabric comprises variably intergrown aragonitic spherulites 100–500 μm wide, containing micritic nuclei with coccoid cell molds in various stages of cell division. Spherulite matrices contain aggregates of individual nanospheres 150–200 nm wide, composed of a poorly crystalline Mg‐Si phase, locally containing cell molds with similar dimensions to those within spherulite nuclei. The younger (upper) fabric comprises sub‐polyhedral networks of mineralized EPS composed of an Mg‐Si substance. The polyhedrons contain aragonite‐replaced coccoid cells, voids, and polyhedral spherulites 8–12 μm wide with a morphology determined by fossil EPS, interpreted to have been produced by coccoid cyanobacteria. These spherulites are composed of high‐Mg calcite, inferred to have formed in association with heterotrophic bacteria. Stable isotope data, textural relationships, and geochemical modeling are consistent with cyanobacterial oxygenic photosynthesis influencing the precipitation of Mg‐Si substances and aragonitic spherulites by locally increasing the pH. The morphology of the polyhedral spherulites suggests the former presence of EPS and that faceted spherulites with similar dimensions in the geological record may represent biosignatures. The Rottnest Island conical microbialites demonstrate an intimate association between microbial features and processes and spherulitic fabrics, potentially providing insights into texturally and compositionally similar features in the geological record.

中文翻译：

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来自现代高盐湖，罗特尼斯岛，西澳大利亚的球状微辉石。

在澳大利亚西部罗特尼斯岛的现代高盐湖中，锥形微微晶石中已形成了与结晶性较差的Mg-Si物质在空间上相关的辐射碳酸盐球状纤维。可以根据成分和质地差异来区分两种球形织物。最古老（最下部）的织物由100-500μm宽的杂化杂石质球晶组成，在各个细胞分裂阶段都含有带有球状模子的微晶核。球晶基体包含150-200 nm宽的单个纳米球的聚集体，由结晶度较差的Mg-Si相组成，局部包含与球晶核内尺寸相似的晶胞模。较年轻的（上层）织物包含由Mg-Si物质组成的矿化EPS的亚多面体网络。多面体包含置换了文石的球状细胞，空隙和8–12μm宽的多面体球晶，其形态由化石EPS确定，认为是由球状蓝藻产生的。这些球晶由高镁方解石组成，据推测是与异养细菌形成的。稳定的同位素数据，结构关系和地球化学模型与蓝细菌的氧光合作用一致，该光合作用通过局部提高pH值而影响Mg-Si物质和方沸石的沉淀。多面体球晶的形态表明EPS的存在，并且在地质记录中具有相似尺寸的刻面球晶可能代表生物特征。