Reid R P, Visscher P T, Decho A W, Stolz J F, Bebout B M, Dupraz C, Macintyre I G, Paerl H W, Pinckney J L, Prufert-Bebout L, Steppe T F, DesMarais D J
MGG-RSMAS, University of Miami, Florida 33149, USA.
Nature. 2000 Aug 31;406(6799):989-92. doi: 10.1038/35023158.
For three billion years, before the Cambrian diversification of life, laminated carbonate build-ups called stromatolites were widespread in shallow marine seas. These ancient structures are generally thought to be microbial in origin and potentially preserve evidence of the Earth's earliest biosphere. Despite their evolutionary significance, little is known about stromatolite formation, especially the relative roles of microbial and environmental factors in stromatolite accretion. Here we show that growth of modern marine stromatolites represents a dynamic balance between sedimentation and intermittent lithification of cyanobacterial mats. Periods of rapid sediment accretion, during which stromatolite surfaces are dominated by pioneer communities of gliding filamentous cyanobacteria, alternate with hiatal intervals. These discontinuities in sedimentation are characterized by development of surface films of exopolymer and subsequent heterotrophic bacterial decomposition, forming thin crusts of microcrystalline carbonate. During prolonged hiatal periods, climax communities develop, which include endolithic coccoid cyanobacteria. These coccoids modify the sediment, forming thicker lithified laminae. Preservation of lithified layers at depth creates millimetre-scale lamination. This simple model of modern marine stromatolite growth may be applicable to ancient stromatolites.
在寒武纪生命大爆发之前的三十亿年里，被称为叠层石的层状碳酸盐堆积物在浅海海域广泛分布。这些古老的结构通常被认为起源于微生物，并且可能保存着地球最早生物圈的证据。尽管它们具有进化意义，但人们对叠层石的形成知之甚少，尤其是微生物和环境因素在叠层石堆积过程中的相对作用。在这里，我们表明现代海洋叠层石的生长代表了沉积物堆积与蓝细菌席的间歇性石化之间的动态平衡。快速沉积物堆积时期，叠层石表面由滑行丝状蓝细菌的先锋群落主导，与间断间隔交替出现。这些沉积间断的特征是胞外聚合物表面膜的形成以及随后异养细菌的分解，形成微晶碳酸盐薄壳。在长时间的间断期，会形成包括内生球状蓝细菌的顶极群落。这些球状蓝细菌会改变沉积物，形成更厚的石化层。深层石化层的保存形成了毫米级的层理。这个现代海洋叠层石生长的简单模型可能适用于古代叠层石。
