Fossil plants in sub-basaltic andfluvial silcretes differ in their geological setting, silica source, taphonomy, preservation and the plants and communities represented: these factors collectively indicate distinct silicification pathways. This review shows that the floras in sub-basaltic silcretes are mostly autochthonous, being derived from the local vegetation, whereas the floras in inland fluvial silcretes are transported andallochthonous. The floras in both are three-dimensionally preserved. The plantsin sub-basaltic silcretes areusually permineralised, preserving internal anatomy and cellular morphology, whereas the plants in inland fluvial silcretes occur as moulds/impressions that may preserve epidermal andsurface features. Both types of silcrete floras offer insights into past environments and ecological drivers. Terrestrial (ground-dwelling) ferns are frequently preservedin situin sub-basaltic silcretes whilst in the inland fluvial silcretes they are represented only by pinnule fragments or abscised pinnules. The extraordinary anatomical preservation of soft tissues in sub-basaltic silcretes, e.g., exocarps of fruits, bark on wood, actively growing vegetative shoots (fern croziers) and root nodules, is evidence of rapid burial by volcanogenic sediments and subsequent silicification by silica-richgroundwaters. The source of silica was hydrothermal fluids released at the time of eruption and/or the weathering of overlying volcanics, and the acidic (humic) conditions resulting from buried plant material provided ideal geochemical conditions for silica precipitation and plantpermineralisation. The sub-basaltic silcrete floras formed contemporaneously with Eocene–Miocene volcanism in eastern Australia, whereas the formation of inland pedogenic and fluvial silcretes was probably initiated during the Paleocene–Eocene Thermal Maximum (PETM). The fine surface preservation of plants in inland fluvial silcrete floras indicates rapid burial but no organic material is preserved, probably because oxidising groundwaters stripped out the organics before silicification occurred. The comparatively less silica-rich groundwaters associated withfluvial silcretes and the sandy substrates would have further contributed to the loss of plant material.

中文翻译：

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因火而生，因水而生——回顾古环境条件、植物区系组合和保存模式，作为澳大利亚硅质混凝土植物区系独特硅化途径的证据


次玄武质和河流硅质岩中的化石植物在地质环境、硅源、埋藏学、保存以及所代表的植物和群落方面有所不同：这些因素共同表明了不同的硅化途径。本综述表明，次玄武质硅质结界中的植物群大多是本地植物群，源自当地植被，而内陆河流相硅质结界中的植物群是迁移的和外来的。两者的植物群均以三维方式保存。玄武质硅质结界中的植物通常是全矿化的，保留内部解剖结构和细胞形态，而内陆河流硅质结界中的植物以模具/压痕形式出现，可以保留表皮和表面特征。两种类型的硅质混凝土植物群都提供了对过去环境和生态驱动因素的见解。陆生蕨类植物经常保存在原位玄武岩硅质结界中，而在内陆河流的硅质结界中，它们仅以小羽片碎片或脱落的小羽片为代表。玄武岩下的硅质结节中的软组织（例如水果的外果皮、木材上的树皮、活跃生长的营养芽（蕨类植物）和根瘤）在解剖学上保存得非常完好，这是火山沉积物快速埋藏以及随后富含二氧化硅的地下水硅化的证据。二氧化硅的来源是火山喷发和/或上覆火山风化时释放的热液，埋藏植物材料产生的酸性（腐殖质）条件为二氧化硅沉淀和植物矿化提供了理想的地球化学条件。 次玄武岩硅质交结物群是与澳大利亚东部的始新世-中新世火山活动同时形成的，而内陆成土和河流硅质交结物的形成可能是在古新世-始新世最热期（PETM）期间开始的。内陆河流硅质混凝土植物群中植物的良好表面保存表明快速埋藏，但没有保存有机物质，可能是因为氧化地下水在硅化发生之前剥离了有机物。与河流硅质凝结物和沙质基质相关的富含二氧化硅的地下水相对较少，会进一步导致植物材料的损失。