Lindsay John F
Lunar and Planetary Institute, Houston, Texas, USA.
Astrobiology. 2008 Aug;8(4):823-39. doi: 10.1089/ast.2008.0230.
There is a growing body of evidence which suggests that the evolution of the planet drives the evolution of the biosphere. There have been 2 significant stages in Earth history when atmospheric oxygen levels rose rapidly, and both appear to be associated with supercontinent cycles. The earlier biospheric event, which extends across the Archean-Proterozoic boundary (ca. 3.0-2.2 Ga), has received little attention and is the focus of this study. Recent work on the Pilbara Craton of Western Australia has shown that concretion formed by microbial activity during the diagenesis of these sediments are absent from early Archean sediments but abundant in late Archean and early Paleoproterozoic successions of the Hamersley Basin, appearing abruptly in sedimentary rocks younger than 2.7 Ga. This study suggests that their internal architecture may have been defined by the diffusion of humic acids and the formation of polymer gels during diagenesis. The data imply that the biosphere expanded suddenly shortly after 3.0 Ga and may have begun to raise the oxygen levels of the oceanic water column earlier than thought-possibly as much as 300 my earlier.
越来越多的证据表明，地球的演化推动了生物圈的演化。地球历史上有两个重要阶段，大气中的氧气含量迅速上升，而且这两个阶段似乎都与超大陆旋回有关。早期的生物事件跨越太古代-元古代边界（约30亿-22亿年前），但很少受到关注，却是本研究的重点。最近对西澳大利亚皮尔巴拉克拉通的研究表明，在这些沉积物成岩过程中由微生物活动形成的结核在太古宙早期沉积物中并不存在，而在哈默斯利盆地的太古宙晚期和古元古代早期地层中却很丰富，在年龄小于27亿年的沉积岩中突然出现。这项研究表明，它们的内部结构可能是由腐殖酸的扩散和成岩过程中聚合物凝胶的形成所决定的。数据表明，生物圈在30亿年前后不久突然扩张，而且可能比之前认为的更早开始提高海洋水柱中的氧气含量——可能早多达3亿年。
