Nanoscale analysis of preservation of ca. 2.1 Ga old Francevillian microfossils, Gabon

Baghekema, Stellina Gwenaelle Lekele; Lepot, Kevin; Riboulleau, Armelle; Fadel, Alexandre; Trentesaux, Alain; Albani, Abderrazak El

doi:10.1016/j.precamres.2017.08.024

Cited by 23 publications

(21 citation statements)

References 89 publications

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“…Some Siphonophycus may present a sheath with a thickness of around 2 μm. Thick sheaths are generally common among cyanobacteria and not among other bacterial phyla [172]. They may thus be a criterion of a cyanobacterial affinity for those Siphonophycus specimens, in addition to alternating vertical and horizontal disposition in mats, which may indicate phototropism or chemotropism, a behavior not unique to cyanobacteria [41,134].…”

Section: The Fossil Recordmentioning

confidence: 99%

Cyanobacteria evolution: Insight from the fossil record

Demoulin

Lara

Cornet

et al. 2019

Free Radical Biology and Medicine

155

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Cyanobacteria played an important role in the evolution of Early Earth and the biosphere. They are responsible for the oxygenation of the atmosphere and oceans since the Great Oxidation Event around 2.4 Ga, debatably earlier. They are also major primary producers in past and present oceans, and the ancestors of the chloroplast. Nevertheless, the identification of cyanobacteria in the early fossil record remains ambiguous because the morphological criteria commonly used are not always reliable for microfossil interpretation. Recently, new biosignatures specific to cyanobacteria were proposed. Here, we review the classic and new cyanobacterial biosignatures. We also assess the reliability of the previously described cyanobacteria fossil record and the challenges of molecular approaches on modern cyanobacteria. Finally, we suggest possible new calibration points for molecular clocks, and strategies to improve our understanding of the timing and pattern of the evolution of cyanobacteria and oxygenic photosynthesis.

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Section: The Fossil Recordmentioning

confidence: 99%

Cyanobacteria evolution: Insight from the fossil record

Demoulin

Lara

Cornet

et al. 2019

Free Radical Biology and Medicine

155

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“…) and other ancient organic fossils (Lekele Baghekema et al . ; Wacey et al . ), and interpreted as a diagenetic feature.…”

Section: Discussionmentioning

confidence: 99%

On the structure and chemistry of fossils of the earliest woody plant

et al. 2019

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Palaeontology relies on the description of fossil morphologies to understand the evolutionary history of life on Earth. Yet much remains unknown about the impact of fossilization processes, even though these may introduce biases into palaeobiological interpretations. Here, we report the characterization of fossilized remains of the earliest known woody plant Armoricaphyton chateaupannense preserved either in 2D (as flat carbonaceous films) or in 3D (as organo‐mineral structures) in early Devonian shales (c. 407 Ma) of the Armorican Massif on the northern margin of Gondwana. To document the fine‐scale structure and the chemistry of the tracheids of this ancient plant, we used propagation phase contrast synchrotron radiation X‐ray microcomputed tomography (PPC‐SRμCT), transmission electron microscopy (TEM) and synchrotron‐based scanning transmission X‐ray microscopy (STXM) coupled with X‐ray absorption near edge structure (XANES) spectroscopy. PPC‐SRμCT enables digital visualization of cell walls in unprecedented detail for the specimens preserved in 3D revealing structures similar to those observed in extant lignified cells, thereby strongly suggesting that the earliest woody plant A. chateaupannense originally contained lignin compounds. STXM‐based XANES and TEM data show that, whatever the preservation modes (3D vs 2D), the remaining organic matter has a chemical composition rather typical of pyrobitumen compounds, raising the possibility of an original source other than lignin. The pyrobitumen compounds also contains automorphic Ti‐nanominerals interpreted as a diagenetic feature. Altogether, the present study illustrates that anatomical and chemical preservations may not always be correlated.

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“…A small number of studies have reported the presence of anatase with fossils (Foucher et al, 2012; Galvez et al, 2012; Lekele Baghekema et al, 2017; Noffke et al, 2008; Toporski et al, 2002). Noffke et al (2008) described the presence of a Ti oxide in the dark laminae of fossilised microbial mats, but no mention was made as to whether the grains were likely detrital or authigenic in origin.…”

Section: Discussionmentioning

confidence: 99%

“…Anatase has also been reported in association with macrofossils: with an Oligocene tadpole and coprolite (Toporski et al, 2002), and as nanocrystals associated with carbonaceous remains of Jurassic leaves (Johnston, Raine, & Watters, 1987). Precambrian examples include anatase grains associated with silicified organic‐walled microfossils (OWMs) of the Draken Formation (Foucher, Westall, & Knoll, 2012); the laminated cherts of the Gunflint Formation where anatase is present as detrital grains, not as an authigenic sedimentary phase (Papineau et al, 2017); diagenetic Ti‐rich nanocrystals, possibly anatase, associated with Francevillian Gunflint‐like microfossils (Lekele Baghekema et al, 2017); and in Archaean microbially influenced sedimentary structures from the Pongola Super Group (Bower, 2011; Noffke, Beukes, Bower, Hazen, & Swift, 2008). All these examples, however, report grains of anatase around the fossils, but do not describe authigenic anatase crystals within the fossils, which is the focus of this paper.…”

Section: Introductionmentioning

confidence: 99%

Authigenic anatase within 1 billion‐year‐old cells

et al. 2020

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The siliciclastic ~1 Ga‐old strata of the Torridon Group, Scotland, contain some of the most exquisitely preserved three‐dimensional organic‐walled microfossils (OWMs) of the Precambrian. A very diverse microfossil assemblage is hosted in a dominantly phosphatic and clay mineral matrix, within the Diabaig and the Cailleach Head (CH) Formations. In this study, we report on several microfossil taxa within the CH Formation (Leiosphaeridia minutissima, Leiosphaeridia crassa, Synsphaeridium spp. and Myxococcoides spp.) that include populations of cells containing an optically transparent and highly refringent mineral, here identified using electron microscopy as anatase (TiO2). Most anatase crystals occur entirely within individual cells, surrounded by unbroken carbonaceous walls. Rarely, an anatase crystal may protrude outside a cell, interpreted to correspond to zones where the cell wall had broken down prior to anatase precipitation. Where an anatase crystal entombs an organic intracellular inclusion (ICI), the ICI is large and well preserved. These combined observations indicate that the intracellular anatase is an authigenic sedimentary phase, making this the first report of in situ precipitated anatase intimately associated with microfossils. The ability of anatase to preserve relatively large volumes of intracellular and cell wall organic material in these cells suggests that the crystallisation of anatase entombed cellular contents particularly quickly, soon after the death of the cell. This is consistent with the strong affinity of Ti for organic material, the low solubility of TiO2, and reports of Ti occurring in living organisms. With the data currently available, we propose a mineralisation pathway for anatase involving Ti complexation with organic ligands within specific cells, leading to localised post‐mortem anatase nucleation inside these cells as the complexes broke down. Further overgrowth of the anatase crystals was likely fuelled by very early diagenetic mobilisation of Ti that had been bound to more labile organic material nearby in the sediments.

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Nanoscale analysis of preservation of ca. 2.1 Ga old Francevillian microfossils, Gabon

Cited by 23 publications

References 89 publications

Cyanobacteria evolution: Insight from the fossil record

Cyanobacteria evolution: Insight from the fossil record

On the structure and chemistry of fossils of the earliest woody plant

Authigenic anatase within 1 billion‐year‐old cells

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