Organic-walled microfossils from the late Mesoproterozoic to early Neoproterozoic lower Shaler Supergroup (Arctic Canada): Diversity and biostratigraphic significance

Loron, Corentin; Rainbird, R H; Turner, Elizabeth C.; Greenman, J. Wilder; Javaux, Emmanuelle

doi:10.1016/j.precamres.2018.12.024

Cited by 48 publications

(38 citation statements)

References 92 publications

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“…800 Ma peak in diversity is driven entirely by sampling. In fact, a spate of recent paleontological studies from rocks 1700–800 Ma suggest higher eukaryotic diversity during this earlier interval than previously known (Agić, Moczydłowska, & Yin, ; Baludikay, Storme, François, Baudet, & Javaux, ; Beghin et al, ; Loron, Rainbird, Turner, Greenman, & Javaux, ; Miao, Moczydłowska, Zhu, & Zhu, ). Recent discovery of complex eukaryotic fossils in previously unexplored 1,000 to 900 Ma rocks in Arctic Canada bolster the case that diversity trends can change with new work in Tonian successions (Loron, François, et al, ).…”

Section: Point–counterpoint Argumentsmentioning

confidence: 86%

On the co‐evolution of surface oxygen levels and animals

et al. 2020

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Few topics in geobiology have been as extensively debated as the role of Earth's oxygenation in controlling when and why animals emerged and diversified. All currently described animals require oxygen for at least a portion of their life cycle. Therefore, the transition to an oxygenated planet was a prerequisite for the emergence of animals. Yet, our understanding of Earth's oxygenation and the environmental requirements of animal habitability and ecological success is currently limited; estimates for the timing of the appearance of environments sufficiently oxygenated to support ecologically stable populations of animals span a wide range, from billions of years to only a few million years before animals appear in the fossil record. In this light, the extent to which oxygen played an important role in controlling when animals appeared remains a topic of debate. When animals originated and when they diversified are separate questions, meaning either one or both of these phenomena could have been decoupled from oxygenation. Here, we present views from across this interpretive spectrum—in a point–counterpoint format—regarding crucial aspects of the potential links between animals and surface oxygen levels. We highlight areas where the standard discourse on this topic requires a change of course and note that several traditional arguments in this “life versus environment” debate are poorly founded. We also identify a clear need for basic research across a range of fields to disentangle the relationships between oxygen availability and emergence and diversification of animal life.

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Section: Point–counterpoint Argumentsmentioning

confidence: 86%

On the co‐evolution of surface oxygen levels and animals

et al. 2020

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“…Microfossils interpreted as green algae may also provide an estimation of the minimum age for chloroplast acquisition. Their fossil record ranges from unambiguous 0.6 Ga prasinophytes based on wall ultrastructure [255], 0.8 Ga probable siphonocladalean chlorophytes and probable hydrodictyacean chlorophyte based on distinctive morphology and ecology [134], the latter also found in 1.1–0.9 Ga lower Shaler Group of arctic Canada [256], to 1.65 Ga acritarchs whose putative algal interpretation needs confirmation [257]. Using the new age of 1.047 Ga calibration for Bangiomorpha , Gibson et al.…”

Section: Molecular Datingmentioning

confidence: 99%

Cyanobacteria evolution: Insight from the fossil record

Demoulin

Lara

Cornet

et al. 2019

Free Radical Biology and Medicine

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153

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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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“…Macroscopic forms are too rare or simple to be of stratigraphic use, and while organic-walled microfossils are common in both finegrained siliciclastic sedimentary rocks or concretions, assemblages are typically dominated by simple, smooth-walled vesicles known as Leiosphaeridia, a biologically uninformative acritarch taxon. Nonetheless, with a growing number of taxonomic studies linked to new paleoenvironmental, chemostratigraphic and geochronologic constraints (e.g., Sergeev et al, 2012;Tang et al, , 2015Baludikay et al, 2016;Porter and Riedman 2016;Riedman and Porter, 2016;Beghin et al 2017a, b;Loron and Moczydłowska, 2017;Loron et al, 2019a;Cohen et al 2017a,b;Javaux and Knoll, 2017;Miao et al, 2019), a nascent Proterozoic biostratigraphic record is beginning to take shape.…”

Section: Nascent Potential Of Proterozoic Biostratigraphy and Chemostmentioning

confidence: 99%

Towards a new geological time scale: A template for improved rock-based subdivision of pre-Cryogenian time

Shields¹,

Strachan²,

Porter³

et al. 2022

Preprint

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Four first-order (Hadean, Archean, Proterozoic and Phanerozoic eon) and nine second-order (Paleoarchean, Mesoarchean, Neoarchean, Paleoproterozoic, Mesoproterozoic, Neoproterozoic, Paleozoic, Mesozoic and Cenozoic era) units continue to provide intuitive subdivision of geological time. Major transitions in Earth's tectonic, biological and environmental history occurred at approximately 2.5-2.3, 1.8-1.6, 1.0-0.8 and 0.7-0.5 Ga, and so future rock-based subdivision of pre-Cryogenian time, eventually by use of global stratotypes (GSSPs), will likely require only modest deviation from current chronometric boundaries (GSSAs) at 2.5, 1.6 and 1.0 Ga, respectively. Here we argue that removal of GSSAs could be expedited by establishing event-based concepts and provisional, approximate ages for eon-, era-and period-level subdivisions as soon as practicable, in line with ratification of an Ediacaran GSSP in 2004 and chronostratigraphic definition of the Cryogenian Period at c. 720 Ma in 2012. We also outline the geological basis behind current chronometric divisions, explore how they might differ in any future rock-based scheme, identify where major issues might arise during the transition, and outline where some immediate changes to the present scheme could be easily updated/formalised, as a framework for future GSSP development. In line with these aims, we note that the currently recommended four-fold Archean subdivision has not been formally ratified and agree with previous workers that it could be simplified to an informal threefold subdivision, pending more detailed analysis. Although the ages of period boundaries would inevitably change in a more closely rock-based or chronostratigraphic scheme, we support retention of all currently ratified period names. Existing period names, borrowed from the Greek, were chosen to delimit natural phenomena of global reach. Any new global nomenclature ought to follow this lead for consistency, and so we discourage the use of supercontinent names (e.g. Rodinian, Columbian) and regional phenomena, however exceptional. In this regard, we tentatively suggest that a new period (e.g. the 'Kratian'), could precede the Tonian as the first period of the Neoproterozoic Era and we concur with previous authors that the existing Siderian Period (named for banded iron formations) would fit better as a chronostratigraphically defined period of the terminal Archean. Indeed, all pre-Cryogenian subdivisions will need more conceptual grounding in any future chronostratigraphic scheme. We conclude that improved rock-based division of the Proterozoic Eon would likely comprise a threefold , period-level subdivision of the Paleoproterozoic Era (Oxygenian Rhyacian, Orosirian), a four-fold subdivision of the Mesoproterozoic Era (Statherian, Calymmian, Ectasian, Stenian) and potentially four-fold subdivision of the Neoproterozoic Era (pre-Tonian 'Kratian', Tonian, Cryogenian and Ediacaran). Future refinements towards an improved rockbased pre-Cryogenian geological time scale could be propoosed by new interna...

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Organic-walled microfossils from the late Mesoproterozoic to early Neoproterozoic lower Shaler Supergroup (Arctic Canada): Diversity and biostratigraphic significance

Cited by 48 publications

References 92 publications

On the co‐evolution of surface oxygen levels and animals

On the co‐evolution of surface oxygen levels and animals

Cyanobacteria evolution: Insight from the fossil record

Towards a new geological time scale: A template for improved rock-based subdivision of pre-Cryogenian time

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