Sedimentary cherts, with well-preserved microfossils, are known from the Archean to the present, yet their origins remain poorly understood. Lake Magadi, Kenya, has been used as a modern analog system for understanding the origins of nonbiogenic chert. We present evidence for synsedimentary formation of Magadi cherts directly from siliceous gels. Petrographic thin-section analysis and field-emission scanning electron microscopy of cherts from cores drilled in Lake Magadi during the Hominin Sites and Paleolakes Drilling Project in 2014 led to the discovery of two-dimensional branching “labyrinth patterns” in chert, which are a type of fractal “squeeze” pattern formed at air-liquid interfaces. Labyrinth patterns preserved in chert from Lake Magadi cores indicate invasion of air along planes in dewatering gels. These patterns support the precipitation of silica gels in the saline-alkaline Lake Magadi system and syndepositional drying of gels in contact with air as part of chert formation. Recognizing cherts as syndepositional has been critical for our use of them for U-Th dating. Identification of labyrinth patterns in ancient cherts can provide a better understanding of paleoenvironmental and geochemical conditions in the past.

中文翻译：

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马加迪（肯尼亚）燧石中的迷宫图案：硅质凝胶早期形成的证据

沉积燧石具有保存完好的微化石，从太古代到现在都为人所知，但它们的起源仍然知之甚少。肯尼亚的马加迪湖已被用作了解非生物燧石起源的现代模拟系统。我们提供了直接从硅质凝胶中同沉积形成 Magadi 燧石的证据。2014 年 Hominin Sites and Paleolakes Drilling Project 期间在马加迪湖钻取的岩心燧石的岩相薄片分析和场发射扫描电子显微镜导致在燧石中发现二维分支“迷宫图案”，这是一种类型在气液界面形成的分形“挤压”图案。保存在马加迪湖岩心燧石中的迷宫图案表明空气在脱水凝胶中沿平面侵入。这些模式支持硅胶在盐碱湖 Magadi 系统中的沉淀，以及作为燧石形成一部分的与空气接触的凝胶的同沉积干燥。将燧石识别为同沉积物对于我们将它们用于 U-Th 定年至关重要。识别古代硅质岩中的迷宫图案可以更好地了解过去的古环境和地球化学条件。