scholarly journals Early animal evolution and highly oxygenated seafloor niches hosted by microbial mats

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Weiming Ding ◽  
Lin Dong ◽  
Yuanlin Sun ◽  
Haoran Ma ◽  
Yihe Xu ◽  
...  
Keyword(s):  
Oxygen Saturation ◽  
South China ◽  
Ferrous Iron ◽  
Microbial Mats ◽  
Trace Fossils ◽  
Water Interface ◽  
Animal Evolution ◽  
Environmental Background

Abstract The earliest unambiguous evidence for animals is represented by various trace fossils in the latest Ediacaran Period (550–541 Ma), suggesting that the earliest animals lived on or even penetrated into the seafloor. Yet, the O2 fugacity at the sediment-water interface (SWI) for the earliest animal proliferation is poorly defined. The preferential colonization of seafloor as a first step in animal evolution is also unusual. In order to understand the environmental background, we employed a new proxy, carbonate associated ferrous iron (Fecarb), to quantify the seafloor oxygenation. Fecarb of the latest Ediacaran Shibantan limestone in South China, which yields abundant animal traces, ranges from 2.27 to 85.43 ppm, corresponding to the seafloor O2 fugacity of 162 μmol/L to 297 μmol/L. These values are significantly higher than the oxygen saturation in seawater at the contemporary atmospheric pO2 levels. The highly oxygenated seafloor might be attributed to O2 production of the microbial mats. Despite the moderate atmospheric pO2 level, microbial mats possibly provided highly oxygenated niches for the evolution of benthic metazoans. Our model suggests that the O2 barrier could be locally overcome in the mat ground, questioning the long-held belief that atmospheric oxygenation was the key control of animal evolution.

Calcite lilypads and ledges at Lorusio Hot Springs, Kenya Rift Valley: travertine precipitation at the air-water interface

1999 ◽  
Vol 36 (4) ◽  
pp. 649-666 ◽  
Author(s):  
Robin W Renaut ◽  
Brian Jones ◽  
Caroline Le Turdu
Keyword(s):  
Water Surface ◽  
Microbial Mats ◽  
Hot Springs ◽  
Water Interface ◽  
Kenya Rift ◽  
Similar Morphology ◽  
Northern Kenya ◽  
Air Water Interface ◽  
Capillary Evaporation ◽  
Outflow Channel

Travertine forming at Lorusio Hot Springs in the northern Kenya Rift is constructed mainly by lilypads and ledges. The lilypads are flat, accretionary structures rooted to the substrate that are composed mostly of platy calcite crystals. They grow outward from a nucleus, subparallel to the water surface, at or just below the air-water interface. Precipitation results from rapid degassing of CO2. Ledges, which have a similar morphology and internal structure, are attached to the margin of a spring pool or outflow channel. As they grow laterally, lilypads and ledges may coalesce with their neighbours to produce thin (1-3 cm) beds of travertine, examples of which are exposed in subfossil deposits at the site. Once established, lilypads and ledges modify the outflow and can act as substrates for precipitation of other minerals and colonization by microbes on their cooler subaerial surfaces. Pore fluids are drawn upward through the lilypads by capillary evaporation. Amorphous silica then precipitates as surficial crusts upon microbial mats or forms spicular microstromatolites, some of which also contain calcite laminae. Efflorescent Na-CO3 salts commonly encrust the drier central platforms of the exposed lilypad. The unusual abundance of lilypads and ledges at Lorusio reflects (i) the low-relief setting and the hydrostatic head, which limit terrace development, and (ii) the high temperature (>75°C) of the waters, which inhibits colonization by microbial mats at crystal growth sites. Similar structures form in cave pools, evaporating brines, and freezing water at sites where precipitation is induced by several processes active at the air-water interface.

scholarly journals Late Ediacaran organic microfossils from Finland

2021 ◽  
pp. 1-14
Author(s):  
Sebastian Willman ◽  
Ben J. Slater
Keyword(s):  
Microbial Communities ◽  
Microbial Mats ◽  
Trace Fossils ◽  
Impact Structure ◽  
Meteorite Impact ◽  
Fine Grained ◽  
Body Fossil ◽  
New Evidence ◽  
Insight Into ◽  
Direct Body

Abstract Here we present a detailed accounting of organic microfossils from late Ediacaran sediments of Finland, from the island of Hailuoto (northwest Finnish coast), and the Saarijärvi meteorite impact structure (~170 km northeast of Hailuoto, mainland Finland). Fossils were recovered from fine-grained thermally immature mudstones and siltstones and are preserved in exquisite detail. The majority of recovered forms are sourced from filamentous prokaryotic and protistan-grade organisms forming interwoven microbial mats. Flattened Nostoc-ball-like masses of bundled Siphonophycus filaments are abundant, alongside Rugosoopsis and Palaeolyngbya of probable cyanobacterial origin. Acritarchs include Chuaria, Leiosphaeridia, Symplassosphaeridium and Synsphaeridium. Significantly, rare spine-shaped sclerites of bilaterian origin were recovered, providing new evidence for a nascent bilaterian fauna in the terminal Ediacaran. These findings offer a direct body-fossil insight into Ediacaran mat-forming microbial communities, and demonstrate that alongside trace fossils, detection of a bilaterian fauna prior to the Cambrian might also be sought among the emerging record of small carbonaceous fossils (SCFs).

scholarly journals The Ediacaran frondose fossil Arborea from the Shibantan limestone of South China

2020 ◽  
Vol 94 (6) ◽  
pp. 1034-1050 ◽  
Author(s):  
Xiaopeng Wang ◽  
Ke Pang ◽  
Zhe Chen ◽  
Bin Wan ◽  
Shuhai Xiao ◽  
...  
Keyword(s):  
New Species ◽  
South China ◽  
Type Species ◽  
Microbial Mats ◽  
Width Ratio ◽  
General Morphology ◽  
Dengying Formation ◽  
Length Width

AbstractBituminous limestone of the Ediacaran Shibantan Member of the Dengying Formation (551–539 Ma) in the Yangtze Gorges area contains a rare carbonate-hosted Ediacara-type macrofossil assemblage. This assemblage is dominated by the tubular fossil Wutubus Chen et al., 2014 and discoidal fossils, e.g., Hiemalora Fedonkin, 1982 and Aspidella Billings, 1872, but frondose organisms such as Charnia Ford, 1958, Rangea Gürich, 1929, and Arborea Glaessner and Wade, 1966 are also present. Herein, we report four species of Arborea from the Shibantan assemblage, including the type species Arborea arborea (Glaessner in Glaessner and Daily, 1959) Glaessner and Wade, 1966, Arborea denticulata new species, and two unnamed species, Arborea sp. A and Arborea sp. B. Arborea arborea is the most abundant frond in the Shibantan assemblage. Arborea denticulata n. sp. resembles Arborea arborea in general morphology but differs in its fewer primary branches and lower length/width ratio of primary branches. Arborea sp. A and Arborea sp. B are fronds with a Hiemalora-type basal attachment. Sealing by microbial mats and authigenic cementation may have played an important role in the preservation of Arborea in the Shibantan assemblage. The Shibantan material of Arborea extends the stratigraphic, ecological, and taphonomic ranges of this genus.UUID: http://zoobank.org/554f21da-5f09-4891-9deb-cbc00c41e5f1

Uppermost Permian trace fossils along a shelf to slope transect in South China and their implications for oceanic redox evolution and extinction pattern

2018 ◽  
Vol 167 ◽  
pp. 74-86 ◽  
Author(s):  
Li-Jun Zhang ◽  
Luis A. Buatois ◽  
M.Gabriela Mángano ◽  
Yi-Ming Gong ◽  
Qing-Lai Feng ◽  
...  
Keyword(s):  
South China ◽  
Trace Fossils ◽  
Redox Evolution

The Shibantan Lagerstätte: insights into the Proterozoic–Phanerozoic transition

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-135
Author(s):  
Shuhai Xiao ◽  
Zhe Chen ◽  
Ke Pang ◽  
Chuanming Zhou ◽  
Xunlai Yuan
Keyword(s):  
South China ◽  
Carbonate Rocks ◽  
Microbial Mats ◽  
Ecological Interactions ◽  
Benthic Organisms ◽  
Important Data ◽  
Ediacara Biota ◽  
Marine Carbonate ◽  
Fossil Assemblages ◽  
Marine Carbonate Rocks

The Shibantan Lagerstätte (551–543 Ma) in the Yangtse Gorges area in South China is one of the best-known examples of terminal Ediacaran fossil assemblages preserved in marine carbonate rocks. Taxonomically dominated by benthic organisms, the Shibantan Lagerstätte preserves various photoautotrophs, biomineralizing tubular fossils, Ediacara-type macrofossils (including rangeomorphs, arboreomorphs, erniettomorphs, palaeopascichnids, a possible dickinsoniomorph, the mobile bilaterian Yilingia and soft-bodied tubular fossils), abundant ichnofossils and a number of problematic and dubious fossils. Shibantan fossils provide intriguing insights into ecological interactions among mobile bilaterians, sessile benthic Ediacara-type organisms and microbial mats, thus offering important data to test various hypotheses accounting for the decline of the Ediacara biota and the concurrent expansion of bilaterian bioturbation and mobility across the Proterozoic–Phanerozoic transition.

Affinities and Taphonomy of a Cambrian Discoid from Guizhou, South China

2014 ◽  
Vol 88 (2) ◽  
pp. 339-347 ◽  
Author(s):  
Xinglian Yang ◽  
Yuanlong Zhao ◽  
Weiyi Wu ◽  
Zongyuan Sun ◽  
Haolin Zheng ◽  
...  
Keyword(s):  
South China ◽  
Extracellular Polymeric Substances ◽  
Microbial Mats ◽  
Burgess Shale ◽  
Mineral Precipitation ◽  
X Ray ◽  
Surrounding Matrix ◽  
Diagenetic Processes ◽  
Phylogenetic Affinities ◽  
Body Fossil

Disc-like fossils from siltstones of the Taozichong Formation (Cambrian) in the Qingzhen area, Guizhou, South China are reported here. They are similar to some Ediacaran and Phanerozoic discoidal fossils, and assigned to Tirasiana? disciformis? Palij, 1976. Based on the study of 43 specimens, dewatering or fluid escape structures, soft-sediment loading, scratch circles or other inorganic origins are ruled out, and the fossil is interpreted as a discoidal body fossil of unknown affinities rather than trace fossils. Energy-dispersive X-ray spectroscopy and elemental mapping analyses reveal that the discoid fossils contain higher concentrations of C, Fe, and P than the surrounding matrix, indicating the possible presence of pyrite, apatite, and organic carbon as a result of authigenic mineralization in association with decay and early diagenetic processes. The possible presence of extracellular polymeric substance suggests that the discs were surrounded by thin microbial mats composed primarily of extracellular polymeric substances, which facilitated their fossilization by promoting conditions that are favorable to secondary mineral precipitation. The new specimens provide useful information about the phylogenetic affinities of these early discoidal fossils and help us to better understand the taphonomic modes of non-biomineralizing organisms in Ediacara-type and Burgess Shale-type biotas.

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