The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity

作者：El Albani Abderrazak^*; Bengtson Stefan; Canfield Donald E; Riboulleau Armelle; Bard Claire Rollion; Macchiarelli Roberto; Pemba Lauriss Ngombi; Hammarlund Emma; Meunier Alain; Mouele Idalina Moubiya; Benzerara Karim; Bernard Sylvain; Boulvais Philippe; Chaussidon Marc; Cesari Christian; Fontaine Claude; Chi Fru Ernest; Garcia Ruiz Juan Manuel; Gauthier Lafaye Francois; Mazurier Arnaud; Pierson Wickmann Anne Catherine; Rouxel Olivier; Trentesaux Alain; Vecoli Marco

来源：PLos One, 2014, 9(6): e99438.

DOI：10.1371/journal.pone.0099438

The Paleoproterozoic Era witnessed crucial steps in the evolution of Earth%26apos;s surface environments following the first appreciable rise of free atmospheric oxygen concentrations similar to 2.3 to 2.1 Ga ago, and concomitant shallow ocean oxygenation. While most sedimentary successions deposited during this time interval have experienced thermal overprinting from burial diagenesis and metamorphism, the ca. 2.1 Ga black shales of the Francevillian B Formation (FB2) cropping out in southeastern Gabon have not. The Francevillian Formation contains centimeter-sized structures interpreted as organized and spatially discrete populations of colonial organisms living in an oxygenated marine ecosystem. Here, new material from the FB2 black shales is presented and analyzed to further explore its biogenicity and taphonomy. Our extended record comprises variably sized, shaped, and structured pyritized macrofossils of lobate, elongated, and rodshaped morphologies as well as abundant non-pyritized disk-shaped macrofossils and organic-walled acritarchs. Combined microtomography, geochemistry, and sedimentary analysis suggest a biota fossilized during early diagenesis. The emergence of this biota follows a rise in atmospheric oxygen, which is consistent with the idea that surface oxygenation allowed the evolution and ecological expansion of complex megascopic life.

• 出版日期2014-6-25