Extensive microbial mats colonize sandy tidal flats that form along the coasts of today's Earth. The microbenthos (mainly cyanobacteria) respond to the prevailing physical sediment dynamics by biostabilization, baffling and trapping, as well as binding. This biotic-physical interaction gives rise to characteristic microbially induced sedimentary structures (MISS) that differ greatly from both purely physical structures and from stromatolites. Actualistic studies of the MISS on modern tidal flats have been shown to be the key for understanding equivalent fossil structures that occur in tidal and shelf sandstones of all Earth ages. However, until now the fossil record of Archean MISS has been poor, and relatively few specimens have been found. This paper describes a study location that displays a unique assemblage with a multitude of exceptionally preserved MISS in the 2.9-Ga-old Pongola Supergroup, South Africa. The 'Nhlazatse Section' includes structures such as 'erosional remnants and pockets', 'multidirected ripple marks', 'polygonal oscillation cracks', and 'gas domes'. Optical and geochemical analyses support the biogenicity of microscopic textures such as filamentous laminae or 'orientated grains'. Textures resembling filaments are lined by iron oxide and hydroxides, as well as clay minerals. They contain organic matter, whose isotope composition is consistent with carbon of biological origin. The ancient tidal flats of the Nhlazatse Section record four microbial mat facies that occur in modern tidal settings as well. We distinguish endobenthic and epibenthic microbial mats, including planar, tufted, and spongy subtypes. Each microbial mat facies is characterized by a distinct set of MISS, and relates to a typical tidal zone. The microbial mat structures are preserved in situ, and are consistent with similar features constructed today by benthic cyanobacteria. However, other mat-constructing microorganisms also could have formed the structures in the Archean tidal flats.

中文翻译：

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南非阿尔及利亚2.9 Ga Pongola超群硅质碎屑Nhlazatse节中的（氰基）细菌诱发的沉积结构的现实主义视角。

广泛的微生物席子定居在当今地球海岸形成的沙质潮滩上。微小底栖动物（主要是蓝细菌）通过生物稳定，挡板和捕集以及结合对主要的物理沉积物动力学作出反应。这种生物物理相互作用产生了特征性的微生物诱导沉积结构（MISS），该结构与纯物理结构和叠层石都大不相同。对现代潮汐平面进行的MISS的现实主义研究已被证明是理解所有地球年龄的潮汐和架子砂岩中存在的同等化石结构的关键。但是，直到现在，太古代MISS的化石记录仍然很差，并且发现的标本相对较少。本文介绍了一个研究地点，该研究地点在南非拥有2.9加仑历史的Pongola Supergroup中展示了一个独特的组合以及大量保存完好的MISS。“ Nazazatse部分”包括“易碎残留物和凹穴”，“多向波纹痕迹”，“多边形振荡裂纹”和“气穹顶”等结构。光学和地球化学分析支持微观纹理（如丝状薄片或“定向晶粒”）的生物起源。类似于长丝的纹理衬有氧化铁，氢氧化物以及粘土矿物。它们包含有机物，其同位素组成与生物来源的碳一致。Nhlazatse段的古代潮滩也记录了在现代潮汐环境中也出现的四个微生物垫相。我们区分了底栖和上底微生物垫，包括平面，簇状和海绵亚型。每个微生物垫相的特征在于一组独特的MISS，并且涉及典型的潮汐带。微生物垫结构被原位保存，并与当今底栖蓝细菌构建的相似特征相一致。然而，其他构造垫的微生物也可能在太古代的滩涂中形成了结构。