Hickman-Lewis Keyron, Cuadros Javier, Yi Keewook, Hong Tae Eun, Byeon Mirang, Jang Jae Hyuck, Choi Min-Yeong, Seo YoonKyung, Najorka Jens, Montgomery Wren, Matlak Krzysztof, Wolanin Barbara, Smith Caroline L, Cavalazzi Barbara
School of Natural Sciences, Birkbeck, University of London, Malet Street, Bloomsbury, London, WC1E 7HX, UK.
Department of Earth Science and Engineering, Imperial College London, London, SW7 2BX, UK.
Nat Commun. 2025 Mar 19;16(1):2726. doi: 10.1038/s41467-025-57727-4.
Exceptional preservation of biogeochemical complexity in the Precambrian is largely limited to cherts, phosphates and shales; however, ancient fossils, including microbial mats and microbially induced sedimentary structures, also occur, more rarely, in poorly sorted, coarse-grained siliciclastics. The precise micromechanics by which exceptional retention of organic microbial traces occur within such rocks over billion-year geological timescales remain poorly understood. Herein, we explore the micro-nano-scale characteristics of microbial mats preserved in ~2.9 billion-year-old sandstones from the Mosquito Creek Formation (Pilbara, Australia) using a suite of advanced spatially correlated microscopy and geochemistry techniques. We demonstrate that sedimentary horizons rich in K-Al-phyllosilicates exhibit exceptional and unexpected preservation of biogeochemical complexity despite the age and metamorphic grade of the sequence. We propose that authigenic phyllosilicates intercalated with microbial kerogen at the nanoscale promote the preservation of nanoscopic domains of poorly ordered amorphous and turbostratic carbonaceous materials through pressure compensation associated with the kaolinite-illite transition during burial diagenesis and metamorphism, impeding the maturation of organic materials. Elucidating organic preservation in coarse-grained siliciclastics opens new avenues for biosignature searches both in ancient Earth sequences and on Mars, where similar phyllosilicate-bearing sandstones have been collected by the Mars 2020 Perseverance rover for near-future sample return.
前寒武纪生物地球化学复杂性的特殊保存主要局限于燧石、磷酸盐和页岩；然而，古老的化石，包括微生物席和微生物诱导的沉积构造，也更罕见地出现在分选差的粗粒硅质碎屑岩中。在数十亿年的地质时间尺度上，此类岩石中有机微生物痕迹得以特殊保存的精确微观机制仍知之甚少。在此，我们使用一系列先进的空间相关显微镜和地球化学技术，探索了保存在澳大利亚皮尔巴拉地区约29亿年前蚊子溪组砂岩中的微生物席的微纳米尺度特征。我们证明，尽管该层序的年代和变质程度不同，但富含钾铝层状硅酸盐的沉积层位展现出了特殊且意想不到的生物地球化学复杂性保存。我们提出，在纳米尺度上与微生物干酪根插层的自生层状硅酸盐，通过埋藏成岩作用和变质作用期间与高岭石 - 伊利石转变相关的压力补偿，促进了无序非晶质和准同相碳质材料纳米域的保存，从而阻碍了有机物质的成熟。阐明粗粒硅质碎屑岩中的有机保存，为在古代地球层序和火星上寻找生物特征开辟了新途径，火星2020毅力号探测器已采集了类似的含层状硅酸盐砂岩以供未来样本返回研究。
