Franceville basin

The Franceville Basin is a 1.6–2.1 billion year old sedimentary basin in Gabon. It contains unmetamorphosed sediments.^[1] It is notable for containing the Francevillian Biota, which are possibly the oldest multicellular life known. A natural fission reactor formed there about 1.8 - 2.1 billion years ago.^[2]

Map of Francevillian basin geology

For other uses, see Francevillian B Formation.

Geology

The Franceville Basin covers approximately 25,000 km² and is made up of unmetamorphosed sediment derived mainly from eroded Mesoarchaean tonalite–trondhjemite–granodiorites.^[3] It is over a kilometer thick, with various sources claiming 2.5-4 kilometers as the maximum depth.^[1] Around 1.8-2.1 billion years ago a natural fission reactor formed, nicknamed the "Oklo reactor". The resulting fission by-products were held in place by a clay layer.^[2]

See also

• Francevillian biota
• Francevillian B Formation

References

1. Bankole, Olabode M.; El Albani, Abderrazak; Meunier, Alain; Gauthier-Lafaye, François (October 2015). "Textural and paleo-fluid flow control on diagenesis in the Paleoproterozoic Franceville Basin, South Eastern, Gabon". Precambrian Research. 268: 115–134. doi:10.1016/j.precamres.2015.07.008.
2. Gauthier-Lafaye, F.; Holliger, P.; Blanc, P. -L. (1996-12-01). "Natural fission reactors in the Franceville basin, Gabon: A review of the conditions and results of a "critical event" in a geologic system". Geochimica et Cosmochimica Acta. 60 (23): 4831–4852. doi:10.1016/S0016-7037(96)00245-1. ISSN 0016-7037.
3. Bankole, Olabode M.; El Albani, Abderrazak; Munier, Alain; Poujol, Marc; Bekker, Andrey (15 September 2020). "Elemental geochemistry and Nd isotope constraints on the provenance of the basal siliciclastic succession of the middle Paleoproterozoic Francevillian Group, Gabon". Precambrian Research. 348: 105874. doi:10.1016/j.precamres.2020.105874. S2CID 224896274. Retrieved 13 November 2022.