New records of late Ediacaran microbiota from Poland

Abstract

a b s t r a c tNew records of organic-walled microfossils, including cyanobacteria, phytoplankton (certain acritarchs) and some microbiota of unknown biological affinities, are reported from the late Ediacaran Włodawa Formation in the Łopiennik IG-1 borehole, Poland. The microfossil association consists mostly of known species, which originated prior to the Cryogenian Period, evidence that these microorganisms survived the Neoproterozoic glacial epochs. The longevity of most of the species is extended herein to ca. 545 Ma. One species is new but described as gen. et sp. indet., because only a single specimen is available. Although the microfossils represent both prokaryotic and eukaryotic groups of organisms, and benthic and planktic modes of life, all, with the exception of Valkyria, are photoautotrophic aerobes. Metabolic processes of nutrition, respiration and reproductive cycles, and ecologic habitats of these biota and the evolutionary lineages to which they belong are analyzed with respect to the basic requirements needed to survive prolonged periods of environmental perturbation.All recorded here cyanobacteria are benthic microbial mat-dwellers, requiring ample water and regular oxygen supply and sun light for their metabolism. Planktic species of Leiosphaeridia studied here are considered to be green algae (chlorophyceans), forming resting cysts and alternating sexual/vegetative generations in their life cycle. They also required habitats of well-oxygenated open water in the photic zone and periodic access to bottom sediment (to rest the cyst) in order to survive the glacial epochs, as they evidently did. It is argued that the natural habitats of all these biota must have been preserved and ecologically functional throughout the Cryogenian Period, and have been robust enough to sustain viable populations and genetic stocks of at least some evolutionary lineages known at the time. This is a primary constraint imposed by contemporaneous marine biosphere on the Earth System model, which can be accepted among hypothetical versions of the Snowball Earth hypotheses based on sedimentological, geochemical, physical and other geological records. The Slushball Earth model, or comparable, is thus favoured over strict Snowball Earth model because it reconciles the habitable conditions with other envisaged geo-and physical conditions during the period.

The Ediacaran microbiota and the survival of Snowball Earth conditions

“…The latter isotopic dating is on the tuff layer at the top of the volcanogenic Sławatycze Formation in the Kaplonosy IG-1 borehole by U-Pb on zircon (Compston et al, 1995). The Kaplonosy IG-1 borehole is closely located (only some 30 km) to the Łopiennik IG-1 borehole and both successions belong to the same tectonic unit and contain the same Sławatycze Formation and the succeeding transgressive sequence, which is similar and correlated bio-and lithostratigraphically and by geophysical logging (Moczydłowska, 2008). The microbial association consists of prokaryotic benthic cyanobacteria and eukaryotic planktic microalgae of the genus Leiosphaeridia, and a morphologically more complex taxon Valkyria, whose affiliation and mode of life is not resolved with certainty, but it is likely a planktic and/or facultative benthic eukaryote (Moczydłowska, 2008;Fig.…”

“…1). This age is constrained by the isotopic age of the base of the Cambrian System at 542 Ma (Gradstein et al, 2004), which is recognized some 70-80 m above the studied record in a sedimentologically continuous succession in the Łopiennik IG-1 borehole, and the maximum age of the late Ediacaran succession in this region post-dating 551 ± 4 Ma (Compston et al, 1995;Moczydłowska, 2008). The latter isotopic dating is on the tuff layer at the top of the volcanogenic Sławatycze Formation in the Kaplonosy IG-1 borehole by U-Pb on zircon (Compston et al, 1995).…”

“…The symbol of red asterisk indicates the chronostratigraphic position of a new record from the Lublin Slope in Poland, estimated to at ca. 545 Ma (Moczydłowska, 2008). The formations consisting of the most diverse microbial assemblages are listed.…”

“…The objective evidence to infer the biological affinity and systematic position of some leiosphaerids is revealed by the trilaminar sheath structure of the cell wall, which is diagnostic for certain clades. Based on such studies and by comparing large populations of leiosphaerids, the species recorded in the Lublin association are recognized as planktic green algae from the Class Chlorophyceae (Talyzina and Moczydłowska, 2000;Arouri et al, 2000;Javaux et al, 2004;Moczydłowska, 2008). The natural habitat, which they have occupied, was a marine, welloxygenated basin in a photic zone, with an access to the sediment substrate for periodic resting/reproductive stage in their life cycle.…”

“…A newly described association of cyanobacterial, phytoplanktic and some of uncertain origin microfossils from the terminal Ediacaran in Poland clearly indicates that more species existed continuously through the times of Cryogenian glaciations (Moczydłowska, 2008). The microfossils derive from the Włodawa Formation in the Łopiennik IG-1 borehole on the Lublin Slope of the East European Platform (EEP).…”