Manuscrit Accepté / Accepted Manuscript Arumberiamorph
Manuscrit accepté / Accepted manuscript
Arumberiamorph structure in modern microbial mats: implications for Ediacaran palaeobiology
A.V. KOLESNIKOV, T. DANELIAN, M. GOMMEAUX, A.V. MASLOV and D.V. GRAZHDANKIN
Reçu le /Received date: 25/06/16 Accepté le /Accepted date: 17/01/2017
Prière de citer l’article de la façon suivante / Please cite this article as:
KOLESNIKOV A.V., DANELIAN T., GOMMEAUX M., MASLOV A.V. and GRAZHDANKIN D.V. (2017). – Arumberiamorph structure in modern microbial mats: implications for Ediacaran palaeobiology. – Bulletin de la Société géologique de France, 188, n° thématique (sous presse).
Arumberiamorph structure in modern microbial mats: implications for Ediacaran palaeobiology
Présence de structure arumbériamorphe dans des tapis microbiens modernes: implications pour la paléobiologie à l’Édiacarien
A. V. Kolesnikov,1, 2 T. Danelian,2 M. Gommeaux,3 A. V. Maslov4 and D. V. Grazhdankin1, 5
1Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch Russian Academy of Sciences, prospekt Akademika Koptyuga 3, Novosibirsk 630090, Russia, [email protected]
2Université de Lille 1 – Sciences et Technologies, CNRS, UMR 8198 Evo-Eco-Paleo, F 59655 Villeneuve d’Ascq, France, [email protected]
3Groupe d’Étude sur les Géomatériaux et les Environnements naturels Anthropiques et Archéologiques EA
3795 (GEGENAA) – Université de Reims Champagne-Ardenne, 2 esplanade Roland Garros, F 51100 Reims,
France, [email protected]
4Zavaritsky Institute of Geology and Geochemistry of Ural Branch Russian Academy of Sciences, ulitsa
Vonsovskogo 15, Yekaterinburg 620016, Russia, [email protected]
5Novosibirsk State University, ulitsa Pirogova 2, Novosibirsk 630090, Russia, [email protected]
Keywords. – Microbial mats, microbiallyBSGF induced sedimentary structures, Guérande salinas, Ediacaran, Arumberia
Mots-clés. – Tapis microbien, structures sédimentaires microbiennes, salines de Guérande, Édiacarien,
Arumberia
Abstract. – In the course of studying modern halotolerant microbial mats in salterns near the village of
Kervalet, western France, we observed fanning-out and curved series of macroscopic ridges on the surface of a newly formed biofilm. The structure resembles the late Ediacaran fossil Arumberia which is globally distributed in Australia, Avalonia, Baltica, Siberia and India, always confined to intertidal and delta-plain settings subject to periodic desiccation or fluctuating salinity. Although the origin of the structure observed in modern microbial mats remains enigmatic, wrinkled and rugose variants of microbial biofilms in general exhibit increased levels of resistance to several environmental stresses. By analogy, the fossil Arumberia
1 ACCEPTED MANUSCRIPT could be interpreted as a microbial mat morphotype (the “Arumberia” morph) developed in response to environmental perturbations in terminal Ediacaran shallow marine basins. If environmental conditions are likely to be responsible for the formation of Arumberia, it is not that a specific biological community has survived since the Ediacaran – it is that the biological response of microbial communities that manifested itself quite commonly in certain terminal Ediacaran and early Cambrian environments can still be found
(seemingly in much more restricted settings) today.
Résumé. – Dans le cadre d'une étude des tapis microbiens halotolérants actuels, dans des salines situées près du village de Kervalet (France), nous avons observé des ensembles de rides curvilignes disposées en
éventail, à la surface d'un tapis microbien nouvellement formé. La structure actuelle observée rappelle
Arumberia, fossile de l'Édiacarien supérieur, qui a une très large distribution (Australie, Avalonia, Baltica,
Sibérie et Inde), présent uniquement dans des contextes intertidaux ou de plaines deltaïques, sujets à une dessication périodique et à une salinité variable. Même si l'origine de la structure observée dans les tapis microbiens actuels demeure inconnue, les tapis montrant une structure froncée ou rugueuse sont généralement dotés d'une résistance supérieure à différents stress environnementaux. Par analogie, le fossile
Arumberia pourrait être interprété comme un morphotype (dit “arumbériamorphe”) de tapis microbien développé en réponse à des perturbations de l'environnement de l'Édiacarien terminal, dans des bassins marins peu profonds. Si le facteur causant la formation d’Arumberia est vraisemblablement les conditions environnementales, on ne peut pas conclureBSGF qu’une communauté biologique particulière ait survécu depuis l’Édiacarien – mais plutôt que certaines communautés microbiennes répondent de la même façon aujourd’hui qu’à l’Édiacarien ou au début du Cambrien mais que ceci se manifeste dans des contextes bien plus restreints.
INTRODUCTION
Few Ediacaran fossils pose more problems in terms of pattern recognition and fabricational constraints than does Arumberia. The iconic Arumberia represents series of subparallel, curved or fanning- out ridges preserved on upper bedding plane surfaces of sandstone beds. Although originally interpreted as cup-shaped epibenthic organisms [Glaessner and Walter, 1975], an alternative view would be that these structures are either microbially mediated or even inorganic [Brasier, 1979; Jenkins, 1981; Jenkins et al.
1981; McIlroy and Walter, 1997; Gehling, 1999; Seilacher, 2007]. The regular arrangement of ridges in
2 ACCEPTED MANUSCRIPT Arumberia is akin of the quilted body plan of vendobiont organisms (Arumberia was originally compared to
Natalia villiersiensis, Nasepia altae, and Baikalina sessilis), although the paucity of distinctive margins to individuals calls for a broader comparison with dissipative systems (to which the vendobiont construction may seemingly belong). With the rare exception of two lower Neoproterozoic localities, one in the Diabaig
Formation of northwest Scotland [Callow et al. 2011] and another in the Zilmerdak Formation of South
Urals (pers. obs.), and one early Palaeozoic locality in the Port Lazo Formation of France [Bland, 1984;
Davies et al. 2016], Arumberia appears to be restricted to the uppermost Ediacaran strata, which presents a serious obstacle to the inorganic interpretation. Furthermore, Ediacaran fossil occurrences of Arumberia in
Australia, Avalonia, Baltica, Siberia and India are all confined to intertidal or delta-plain settings subject to periodic desiccation or fluctuating salinity [Bland, 1984; Gehling, 1999; McIlroy et al. 2005; Mapstone and
McIlroy, 2006; Kumar and Pandey, 2008; Kolesnikov et al. 2012, 2015].
The prospect of discovering relict elements of Ediacaran ecosystems that survived in modern biosphere has been tremendously appealing, but very few convincing analogues have been found.
Xenophyophores, a group of giant deep-sea multinucleate rhizopodial protists are sometimes regarded as model organisms for vendobiont palaeobiology and even as possible living counterparts of Ediacaran palaeopascichnids [Zhuravlev, 1993; Seilacher et al. 2003; Seilacher and Mrinjek, 2011]. Another example are the detached cormidial bracts of siphonophore organisms [O’Hara et al. 2016] that have been compared to Ediacaran fossils Albumares brunsae, Anfesta stankovskii, and Rugoconites enigmaticus [Just et al. 2014]. In addition, concentric ring structures occasionallyBSGF observed in modern microbial mats resemble some of the Ediacaran discoidal fossils, specifically Cyclomedusa davidi and Ediacaria flindersi [Grazhdankin and
Gerdes, 2007; Banerjee et al. 2014]. Here we describe fanning-out and curved series of macroscopic ridges on the surface on a newly formed microbial mat and discuss their similarities with the enigmatic Ediacaran fossil Arumberia banksi.
FIELD OBSERVATIONS
In the summer of 2015, we studied modern microbial mats growing in salterns of the Salines de
Guérande Cooperative of Loire-Atlantique, Region of Pays de la Loire, western France (fig. 1A, B). Each saltern, called “salina” (fig. 2A–B) by local residents and cooperative workers, represents a system of reservoirs that are fed by seawater flowing through narrow channels and, occasionally, tubes. During spring tides the turbid seawater from a tide input channel (étier) passes through a gate (controlled by a salt worker)
3 ACCEPTED MANUSCRIPT and enters a special first decantation pond (vasière) where the suspended particles settle down as water salinity increases due to evaporation. Salinity has been measured by refractometer in each pond along the entire water circuit in three salinas (fig. 2A). The water becomes progressively more clear and salty (and hence of higher density) as it flows through an optional secondary filtering decantation pond (cobier) and a chain of fares ponds (salinity values vary between 5.5% and 17%) until it reaches the maximum clarity and salinity in brine storage adernes ponds (salinity up to 34%). The salt is collected in œillets ponds where salt workers (paludières) regularly sweep the salt crystals with a wooden spade and pile it on a round platform called the ladure. The floor in the salina (except for the œillets ponds) is covered with halotolerant microbial mats which stabilise the sediment and prevent it from further suspension by meteoric water and wind action
[Giani et al. 1989; Gerdes et al. 1993, 1994; Gerdes, 2007]. The uppermost layer in microbial mats is dominated by cyanobacteria and diatom algae. The layers underneath record a steep gradient in redox potential. The fares and adernes ponds are cleaned, on average, once every 10 years when the perennial microbial mats are completely removed.
The sediment underneath the microbial mats in fares and adernes ponds of the salinas is thinly laminated being a result of interaction between epibenthic microbial biomass production in the mats, metabolic processes therein, and sedimentation. This so called siliciclastic biolaminite (sensu [Gerdes and
Krumbein 1987; Bouougri and Porada 2002, 2007, 2011]) in some of the abandoned salinas reaches the thickness of 60 mm. We estimate that the average rate of the biolaminite deposit accumulation in the studied salinas is 2 mm per year. BSGF The series of subparallel, curved and fanning-out rugae (figs 2C and 3A–C) was first observed on the surface of microbial mats in July 2015 in a fare pond of the salina of Scovéno near the village of
Kervalet. According to the paludier Charles Perraud, the microbial mat in the salina Scovéno is eight years old. The water in the pond is still, except at certain periods when the gates between the cobier and fares are open. The floor in the fare pond is slightly domed so that water depth varies from 0–5 mm in the centre to
20–30 mm at the periphery. The rugae were restricted to an area where the perennial microbial mat was disturbed in April 2015 during reconstruction of the ponds (salt workers occasionally remove the cohesive, microbially stabilised mud, together with the microbial mat, and use it to strengthen levees between the fares, adernes, and œillets ponds). The newly formed microbial mat with the rugae is relatively thin (1–2 mm) and consists of alternating three light and two dark laminae (fig. 4A, B). Microscopic observations revealed that this mat is composed of oscillatorian cyanobacteria. The fanning-out and curved sets of rugae are aligned in the direction from the centre of the pond along the gentle slope towards one of the margins
4 ACCEPTED MANUSCRIPT (fig. 2B). Occasional branching of individual rugae has also been observed (fig. 3A). The rugae are spaced
1–10 mm apart. The height of the rugae reaches 2 mm, while the width varies from 1 mm to 3 mm (fig. 3B).
Thin sections have revealed that the rugae are undulations on the surface repeated across the entire depth of the microbial mat (fig. 4A). This is also visible macroscopically in areas where the uppermost thin biofilm is partially destroyed exposing the surface of the underlying lamina (fig. 3C). The structure therefore formed on the surface of a newly formed microbial mat and persisted with no visible change in morphology as the mat continued to grow. These rugae even survived heavy rainfall and flooding in August 2015. We also observed a recurrence of the rugae in the following year (July 2016) in similarly disturbed microbial mats of the salinas of Scovéno and Petit Sibéron (fig. 5).
ON THE POSSIBLE NATURE OF THE RUGAE
The nature of the rugae observed in modern microbial mats near Kervalet remains enigmatic. There is no discernible evidence of physical destruction (cracks, lacerations) of the microbial mat (sensu [Schieber,
2004; Eriksson et al. 2007]), therefore it seems unlikely that the rugae are formed by desiccation, shrinkage or salt crystallisation processes. Nor could they be mechanical rake marks left by salt workers. Furthermore, the alignment of the rugae down in the direction of the slope (not across the slope) suggests that sliding deformation of the microbial mat could not be responsible for the formation of the structure. The rugae, therefore, is a manifestation of biologicalBSGF processes in microbial mats. Many microbial species are capable of forming multicellular structures comprising similarly elaborate wrinkles and rugae, yet the factors governing their architecture are poorly understood. One study suggests that the formation of rugae on the surface of microbial biofilm is a redox-driven adaptation that maximises oxygen accessibility [Dietrich et al. 2013]. An experimental decrease in atmospheric oxygen concentration from 22% to 5% had the reproducible effect of increasing the number of rugae on the biofilm; increasing oxygen concentration to 35%, in contrast, markedly suppressed wrinkling, resulting in flat, featureless biofilm [Kolodkin-Gal et al. 2013]. Another work has shown that rugae form as a result of vertical mechanical buckling of the biofilm triggered by localised cell death during growth [Asally et al.
2012]. Microscopic studies reveal a channel beneath each ruga that could be part of a larger network system for enhanced transport of nutrients within the biofilm [Wilking et al. 2013]. Rugose variants of microbial biofilms in general exhibit increased levels of resistance to several environmental stresses [Fong and Yildiz,
2007].
5 ACCEPTED MANUSCRIPT We did not conduct any in situ environmental measurements or microbiological observations during our reconnaissance survey in the salinas. Therefore, we refrain from interpreting the observed rugae in the salina near Kervalet as a response to any single chemical, physical or biological insult.
IMPLICATIONS FOR EDIACARAN PALAEOBIOLOGY
The rugae in the salina of Scovéno near the village of Kervalet resemble Arumberia, an enigmatic structure reported worldwide, primarily in uppermost Ediacaran strata. Arumberia banksi was first described as a problematic coelenterate fossil organism characterised by “hollow compressible ribbed bodies composed originally of flexible tissue, of conical to cylindrical shape,” with a blunt apex and indistinct distal margin
[Glaessner and Walter, 1975, p. 61]. It was subsequently reinterpreted as a sedimentary structure, specifically current rills or flute marks in cohesive muddy substrate [Brasier, 1979; Jenkins, 1981; Jenkins et al. 1981;
McIlroy and Walter, 1997]. The exact nature of Arumberia is currently debated, with interpretations ranging from a procumbent colonial organism [Bland, 1984], to a distinct type of microbial community [Kolesnikov et al. 2012, 2015], to a putative microbially-induced sedimentary structure [Gehling, 1999; McIlroy et al.
2005; Kumar and Pandey, 2008, 2009; Callow et al. 2011; Kumar and Ahmad, 2014; Davies et al. 2016], to slide marks underneath tough biomats that were exposed to tractional currents loaded with sediment
[Seilacher, 2007]. Apart from the type locality in central Australia, confirmed terminal Ediacaran occurrences of Arumberia have been known from Newfoundland,BSGF England and Wales, northeastern Europe, Central and South Urals, Eastern Sayan, Lake Baikal area, Central India and Rajasthan [Bland, 1984; McIlroy et al.
2005; Kolesnikov et al. 2012, 2015; Kumar and Pandey, 2008, 2009; pers. obs.]. In addition, Arumberia has been reported from lower Palaeozoic strata in Brittany, France [Bland, 1984; Davies et al. 2016].
Uppermost Ediacaran strata in the Central and South Urals, Russia (fig. 1A) represent perhaps one of the most informative Arumberia fossil localities. Arumberia in the Central Urals is restricted to the Krutikha
Member of the Chernokamen Formation (Sylvitsa Group) interpreted as an intertidal low delta plain depositional system [Grazhdankin et al. 2009; Kolesnikov et al. 2012]. In the South Urals, Arumberia is confined to thick sandstone bodies within the Zigan Formation (Asha Group) interpreted as tidal shoreface depositional systems [Kolesnikov et al. 2015]. As many as six varieties of Arumberia have been initially recognised in these localities, including subparallel or fanning-out series of rugae (Arumberia banksi s.str.) and subparallel series of branching rugae (Arumberia vindhyanensis). On closer inspection, however, two varieties referred to as Arumberia usvaensis and Arumberia multykensis [Kolesnikov et al. 2012] turned out
6 ACCEPTED MANUSCRIPT to be preservational morphs of Arumberia banksi s.str., whereas the remaining two varieties, specifically
Arumberia beckeri and Arumberia ollii, represent compressed filamentous and ribbon-shaped macrofossils defined by authigenic clay minerals and are most likely unrelated to Arumberia. The fossil localities in the
Urals have nevertheless yielded important insights into the biostratinomy of Arumberia.
The original description of Arumberia was based on information taken from lower bedding surfaces because the fossils had been thought to be similar in preservation to other soft-bodied organisms in the
Ediacara Member of South Australia [Glaessner and Walter, 1975; Glaessner, 1979]. This assumption turned out to be misleading because Arumberia is often found on upper bedding surface of sandstone interbeds in contact with overlying shales (figs. 3D–F and 4C, D). It therefore seems more reasonable to describe
Arumberia as positive epirelief consisting of subparallel or fanning-out series of straight, slightly arcuate, occasionally bifurcating and branching ridges, or rugae [Bland, 1984; McIlroy et al. 2005; Kolesnikov et al.
2015].
Thin sections reveal that the fossil Arumberia (preserved as epirelief) is always confined to thin intervals characterised by a submillimetre-scale biolamination and that the rugae are repeated across several laminae (figs 3F and 4C, D). The siliciclastic biolaminites (fig. 6A–C) are always restricted to low energy, intertidal to supratidal depositional environment characterised by periodic exposure and occasional high- energy storm events or floods [Bouougri and Porada, 2002, 2007, 2011]. The studied sedimentary successions of the Chernokamen and Zigan formations in the Urals also preserve the record of desiccation, fluctuating salinity and flooding [KolesnikovBSGF et al. 2012, 2015]. Thick packages of siliciclastic biolaminites (fig. 6D–G) are also notable in the logged sections; however, the Arumberia fabric has only been observed in thin biolaminites (fig. 4C). Although high energy storm or flood events could occasionally smother the rugae, the natural habitat of Arumberia was most likely to be low energy, if not calm, intertidal flats.
That there is a correspondence between the alignment of rugae in Arumberia and the palaeocurrent direction measured from trough cross-strata sets and flute casts in the host sedimentary succession has long been appreciated [Glaessner and Walter, 1975; Bland, 1984; Kolesnikov et al. 2012], but the importance of this observation remains obscure. The current alignment of the rugae could be a rheotropic response of the microbial community to tidal flow. Alternatively, this could be interpreted as a tropic response of the microbial community to local slope in competition for sunlight. By all means, a current shear stress in microbially bound sediment has been ruled out by our observations.
Some of the features in the fossil material are almost identical to the structure observed in the salina of Scovéno. Similarity is observed both in the arrangement and in the internal structure of the rugae (figs 3
7 ACCEPTED MANUSCRIPT and 4). Thus, the rugae in both the fossil Arumberia and in the modern structure are 0.5–2.0 mm thick, spaced 1–10 mm apart, and repeated across several laminae. Furthermore, in a number of specimens,
Arumberia appears to originate abruptly along a curved ledge (fig. 3A, D) identical to what we have observed in the salina of Scovéno. The fossil Arumberia, therefore, could be interpreted as a macroscopic structure formed on the surface of microbial mat in response to environmental factors. This seems entirely plausible, given the restriction of the fossil Arumberia to intertidal or delta-plain settings subject to periodic desiccation or fluctuating salinity.
Our observations suggest that Arumberia is more likely to be a morphological feature of highly organised microbial colonies [Kolesnikov et al. 2012, 2015] than a product of microbially mediated adhesion, accretion or baffling of sediment. This, of course, echoes the widely discussed remarks by Bland
[1984] that Arumberia is a mould of a procumbent colony. Macroscopic morphology of microbial biofilms and colonies in general is a manifestation of several biological strategies adopted by microorganisms to cope with stress conditions, such as nutrient deprivation, oxygen depletion, antibiotics and host defences.
Recognition of colony morphotypes in scientific and clinical laboratories sometimes serves as an auxiliary means for evaluating phenotypic variation in microorganisms and even inferring about bacterial diversity
[Sousa et al. 2013]. We therefore suggest that in the future the name Arumberia is used to identify a specific morphotype of a microbial mat. By the same token, Latin names of some of the Ediacaran discoidal fossils can be used to differentiate between morphotypes of microbial colonies [Grazhdankin and Gerdes, 2007]. BSGF CONCLUSION
Supposing the structure observed in microbial mats near Kervalet is a modern analogue to the fossil
Arumberia, various aspects of late Ediacaran palaeobiology can now be readdressed. The appearance of the arumberiamorph structure in the uppermost Ediacaran strata coincides with a decline in diversity of soft- bodied organisms, an event that is sometimes referred to as the Kotlinian Crisis [Sokolov, 1990; Brasier,
1992; Brasier and Lindsay, 2001; Grazhdankin, 2014; Kolesnikov et al. 2015]. The crisis was preceded by a global sea level lowstand (the so-called ‘Kotlin regression’) and a build-up of nutrients in stratified marine reservoirs. The subsequent global rise of sea level could potentially trigger an overturn of a stratified water column and a collapse of coastal marine ecosystems [Brasier and Lindsay, 2001]. The occurrence of fossil
Arumberia in intertidal and delta-plain settings, therefore, could be a response of microbial ecosystems to an environmental stress such as redox heterogeneity of terminal Ediacaran shallow marine basins. Although the
8 ACCEPTED MANUSCRIPT analogy with modern microbial mats is not precise, the fossil arumberiamorph structure is just the kind of images that might be returned from the unmanned rover exploration of other planets, and is a reminder that even a simple geomicrobiological system may be different, perhaps very different, than is sometimes imagined.
Acknowledgements. – This study was supported by the Russian Science Foundation grant 14-17-00409 and by a CNRS-INSU 2016 – INTERRVIE grant. Our collaboration has been made possible through funding of the CNRS-DRI grant no. ED26110, a grant of the French Ministry of Higher Education and Research –
DERCI in support of the French-Siberian Center of Training & Research, a PhD Metchnikov grant of the
French Embassy in Moscow and a Russian Foundation for Basic Research grant 15-05-01512. We thank the paludiers Charles Perraud, Gilles Dessomme and Sylvain Dubreil, as well as the Salines de Guérande
Cooperative for generously sharing their knowledge and experience and allowing the observation and collection of the material. Constructive remarks by two anonymous reviewers improved the initial manuscript.
References
Asally M., Kittisopikul M., Rué P,. Du Y., Hu Z., Çağatay T., Robinson A.B., Lu H., Garcia-Ojalvo J. & Süel G.M. (2012). – Localized cell death focusesBSGF mechanical forces during 3D pattering in a biofilm. – PNAS, 109 (46), 18891–18896.
Banerjee S., Sardar S. & Eriksson P.G. (2014). – Palaeoenvironmental and biostratigraphic implications of microbial mat-related structures: examples from the modern Gulf of Cambay and the Precambrian Vindhyan
Basin, India. – Journal of Palaeogeography, 3, 127–144.
Bland B.H. (1984). – Arumberia Glaessner & Walter, a review of its potential for correlation in the region of precambrian-cambrian boundary. – Geological Magazine, 121 (6), 625–633.
Bouougri E. & Porada H. (2002). – Mat-related sedimentary structures in Neoproterozoic pertidal passive margin deposits of the West African Craton (Anti-Atlas Morocco). – Sedimetary Geology, 153, 85–106.
9 ACCEPTED MANUSCRIPT Bouougri E.H. & Porada H. (2007). – Siliciclastic biolaminites indicative of widespread microbial mats in the Neoproterozoic Nama Group of Namibia. – Journal of Afrcian Earth Sciences, 48, 38–48.
Bouougri E.H. & Porada H. (2011). – Biolaminated Siliciclastic Deposits. In: J. Reitner, N. Quéric and G.
Arp, Eds, Advances in Stromatolite Geobiology. Lecture Notes in Earth Sciences. – Springer-Verlag (Berlin)
507–524.
Brasier M.D. (1979). – The Cambrian radiation event. In: M.S. House, Ed, The Origin of Major Invertebrate
Groups. Systematics Association Special Volume No. 12. – Academic Press (London and New York) 103–
159.
Brasier M.D. (1992). – Background to the Cambrian Explosion. – Journal of the Geological Society of
London, 149, 585–587.
Brasier M.D. & Lindsay J.F. (2001). – Did supercontinental amalgamation trigger the “Cambrian
Explosion”. In: A. Zhuravlev and R. Riding, Eds, The Ecology of the Cambrian Radiation. – Columbia
University Press (New York) 69–89.
Callow R.H.T., Battison L. & Brasier M.D.BSGF (2011). – Diverse microbially induced sedimentary structures from 1 Ga lakes of the Diabaig Formation, Torridon Group, northwest Scotland. – Sedimentary Geology,
239, 117–128.
Davies N.S., Liu A.G., Gibling M.R. & Miller R.F. (2016). – Resolving MISS conceptions and misconceptions: A geological approach to sedimentary surface textures generated by microbial abiotic processes. – Earth-Sciences Reviews, 154, 210–246.
Dietrich L.E., Okegbe C., Price-Whelan A., Sakhtah H., Hunter R.C. & Newman D.K. (2013). – Bacterial
Community Morphogenesis Is Intimately Linked to the Intracellular Redox State. – Journal of Bacteriology,
195 (7), 1371–1380.
10 ACCEPTED MANUSCRIPT Eriksson P.G., Schieber J., Bouougri E., Gerdes G., Porada H., Banerjee S., Bose P.K. & Sarkar S. (2007). –
Classification of structures left by microbial mats in their host sediment. In: J. Schieber, P.K. Bose, P.G.
Eriksson, S. Banerjee, S. Sarkar, O. Catuneanu and W. Alterma, Eds, An Atlas of Microbial Mat Features
Preserved within the Clastic Rock Record. – Elsevier Verlag (Berlin) 39–52.
Fong J.C.N. & Yildiz F.H. (2007). – The rbmBCDEF gene cluster modulates development of rugose colony morphology and biofilm formation in Vibrio cholerae. – Journal of Bacteriology, 189 (6), 2319–2330.
Gehling J.G. (1999). – Microbial mats in Terminal Proterozoic siliciclastics: Ediacaran death masks. –
Palaios, 14, 40–57.
Gerdes G. (2007). – Structures left by modern microbial mats in their host sediments. In: J. Schieber, P.K.
Bose, P.G. Eriksson, S. Sarkar, W. Altermann and O. Catuneanu, Eds, Atlas of Microbial Mat Features preserved within the Siliciclastic Rock Record. – Elsevier Verlag (Berlin) 5–38.
Gerdes G. & Krumbein W.E. (1987). – Biolaminated deposits. In: G.M. Bhattacharya, G.M. Friedmann, H.J.
Neugebauer and A. Seilacher, Eds, Lecture notes in Earth Sciences. – Springer-Verlag (Berlin) 9, 1–183.
Gerdes G., Claes M., Dunajtschik-PiewakBSGF K., Riege H.W., Krumbein W.E.O. & Reineck H.W. (1993). – Contribution of Microbial Mats to Sedimentary Surface Structures. – Facies, 29, 61–74.
Gerdes G., Krumbein W.E. & Reineck H.E. (1994). – Microbial mats as architects of sedimentary surface structures. In: W.E. Krumbein, D.M. Paterson and L.J. Stal, Eds, Biostabilization of Sediments. – Bibliotheks und Informationssystem der Carl von Ossietzky Universität (Oldenburg, Germany) 165–182.
Giani D., Seeler J., Giani L. & Krumbein W.E. (1989). – Microbial mats and physicochemistry in a saltern in the Bretagne (France) and in a laboratory scale saltern model. – FEMS Microbiology Ecology, 62, 151–162.
Glaessner M.F. (1979). – Biogeography and biostratigraphy. Precambrian. In: R.A. Robinson and C.
Teichert, Eds, Treatise on Invertebrate Paleontology. Part A. Introduction. – Geological Society of America
11 ACCEPTED MANUSCRIPT (Boulder) 79–118.
Glaessner M.F. & Walter M.R. (1975). – New precambrian fossils from the Arumbera sandstone, Northern
Territory, Australia. – Alcheringa, 1, 59–69.
Grazhdankin D. (2014). – Patterns of evolution of the Ediacaran soft-bodied biota. – Journal of
Paleontology, 88 (2), 269–283.
Grazhdankin D. & Gerdes G. (2007). – Ediacaran microbial colonies. –Lethaia, 40, 201–210.
Grazhdankin D.V., Maslov A.V. & Krupenin M.T. (2009). – Structure and depositional history of the Vendian
Sylvitsa Group in the western flank of the Central Urals. – Stratigraphy and Geological Correlation, 17,
475–492.
Jenkins R.J.F. (1981). – The concept of an “Ediacaran” period and its stratigraphic significance in Australia.
– Transactions of the Royal Society of South Australia, 105, 179–194.
Jenkins R.J.F., Plummer P.S. & Moriarty K.C. (1981). – Late precambrian pseudofossils from the Flinders Ranges, South Australia. – TransactionsBSGF of the Royal Society of South Australia, 105, 67–84.
Just J., Kristensen R.M. $ Olesen J. (2014). – Dendrogramma, new genus, with two new non-bilaterian species from the marine bathyal of Southeastern Australia (Animalia, Metazoa incertae sedis) – with similarities to some medusoids from the Precambrian Ediacara. – PLOS ONE, 9 (9), e102976.
Kolesnikov A.V., Grazhdankin D.V. & Maslov A.V. (2012). – Arumberia-type structures in the Upper
Vendian of the Urals. – Doklady Earth Sciences, 447 (1), 1233–1239.
Kolesnikov A.V., Marusin V.V., Nagovitsin K.E., Maslov A.V. & Grazhdankin D.V. (2015). – Ediacaran biota in the aftermath of the Kotlinian Crisis: Asha Group of the South Urals. – Precambrian Research, 263, 59–
78.
12 ACCEPTED MANUSCRIPT Kolodkin-Gal I., Elsholz A.K.W., Muth C., Girguis P.R., Kolter R. & Losick R. (2013). – Respiration control of multicellularity in Bacillus subtilis by a complex of the cytochrome chain with a membrane-embedded histidine kinase. – Genes & Development, 27, 887–899.
Kumar S. & Ahmad S. (2014). – Microbially induced sedimentary structures (MISS) from the Ediacaran
Jodhpur Sandstone, Marwar Supergroup, western Rajasthan. – Journal of Asian Earth Sciences, 91, 352–
361.
Kumar S. & Pandey S.K. (2008). – Arumberia banksi and associated fossils from the neoproterozoic Maihar
Sandstone, Vindhyan Supergroup, Central India. – Journal of the Palaeontological Society of India, 53 (1),
83–97.
Kumar S. & Pandey S.K. (2009). – Note on the occurrence of Arumberia banksi and associated fossils from the Jodhpur Sandstone, Marwar Supergroup, western Rajasthan. – Journal of the Palaeontological Society of
India, 54 (2), 171–178.
Mapstone N.B. & McIlroy D. (2006). – Ediacaran fossil preservation: taphonomy and diagenesis of a discoid biota from the Amadeus Basin, central Australia. – Precambrian Research, 149, 126–148. BSGF McIlroy D. & Walter M.R. (1997). – A reconsideration of the biogenicity of Arumberia banksi Glaessner &
Walter. – Alcheringa, 21, 79–80.
McIlroy D., Crimes T.P. & Pauley J.C. (2005). – Fossils and matgrounds from the Neoproterozoic
Longmyndian Supergroup, Shropshire UK. – Geological Magazine, 142 (4), 441–455.
O’Hara T.D., Hugall A.F., MacIntosh H., Naughton K.M., Williams A. & Moussalli A. (2016).
Dendrogramma is a siphonophore. – Current Biology, 26, R457–R458.
Schieber J. (2004). – Microbial mats in the siliciclastic rock record: a summary of diagnostic features. In:
P.G. Eriksson, W. Altermann, D.R. Nelson, W.U. Mueller and O. Catuneanu, Eds, The Precambrian Earth:
Tempos and Events. Developments in Precambrian Geology. – Elsevier, Verlag (Berlin) 12, 663–673.
13 ACCEPTED MANUSCRIPT Seilacher A. (2007). – Trace Fossil Analysis. – Springer-Verlag (Berlin).
Seilacher A. & Mrinjek E. (2011). – Benkovac Stone (Eocene, Croatia): a deep-sea Plattenkalk? – Swiss
Journal of Geosciences, 104 (Supplement 1), 159–166.
Seilacher A., Grazhdankin D. & Legouta A (2003). – Ediacaran Biota: the dawn of animal life in the shadow of giant protists. – Paleontological Research, 7, 43–54.
Sokolov B.S. (1990). – The Vendian System: historical-geological and paleontological substantiation. In:
B.S. Sokolov and M.A. Fedonkin, Eds, The Vendian System. Vol. 2. Regional Geology. – Springer (Berlin)
226–242.
Sousa T., Chung A., Pereira A., Piedade A.P. & Morais P.V. (2013). – Aerobic uranium immobilization by
Rhodanobacter A2-61 through formation of intracellular uranium-phosphate complexes. – Metallomics, 5,
390–397.
Wilking J.N., Zaburdaev V., De Volder M., Losick R., Brenner M.P. & Weitz D.A. (2013). – Liquid transport facilitated by channels in Bacillus subtilisBSGF biofilms. – PNAS, 110 (3), 848–852.
Zhuravlev A.Y. (1993). – Were Ediacaran Vendobionta multicellulars? – Neues Jahrbuch für Geologie und
Paläontologie, Abhandlungen, 190 (2/3), 299–314.
Figure captions
Fig. 1. Location of the studied site in western France and of the illustrated fossil material from the Urals (A); location of the Guérande salinas in the Pays de la Loire region (B).
Fig. 2. Occurrence of the arumberiamorph structure in modern microbial mats: detailed map of Salina
Scovéno with salinity measures (A); View over the salina of Scovéno near the village of Kervalet (B); arumberiamorph structure observed on the surface of a modern microbial mat (C).
14 ACCEPTED MANUSCRIPT Fig. 3. Similarity between the structure observed in modern microbial mats near Kervalet (A–C) and the fossil Arumberia (D–F). The fossil examples are from the uppermost Ediacaran strata of the Zigan
Formation, Asha Group cropping out along the Zigan River in the South Urals (D, E) and the Chernokamen
Formation, Sylvytsa Group cropping out along the Usva River in the Central Urals (F). Refer to figure 1 for location of the fossil material.
Fig. 4. Similarity in internal structure of the rugae (marked as “R”) in thin siliciclastic biolaminites (marked as “b”) in the modern (A, B) and fossil (C, D) material in cross-section (A, C) and surface view (B, D). The fossil examples (C, D) are from the Chernokamen Formation, Sylvytsa Group cropping out along the Usva
River in the Central Urals. Refer to figure 1 for location of the fossil material.
Fig. 5. Recurrence of the rugae in the following year in the salinas of Scovéno (A) and Petit Sibérone (B).
Persistence of the rugae after the detachment of the microbial mat in the fares ponds of the salina of Scovéno
(C, D).
Fig. 6. Thick modern (A–C) and fossil (D–G) siliciclastic biolaminites. The fossil examples are from the
Chernokamen Formation, Sylvytsa Group (D, E) and Zigan Formation, Asha Group (F, G). Refer to figure 1 for location of the fossil material. BSGF
15 ACCEPTED MANUSCRIPT BSGF
Figure 1.
16 ACCEPTED MANUSCRIPT BSGF
Figure 2.
17 ACCEPTED MANUSCRIPT BSGF
Figure 3.
18 ACCEPTED MANUSCRIPT BSGF
Figure 4.
19 ACCEPTED MANUSCRIPT BSGF
Figure 5.
20 ACCEPTED MANUSCRIPT Figure 6. BSGF
21 ACCEPTED MANUSCRIPT