scholarly journals Evolution of Holdfast Diversity and Attachment Strategies of Ediacaran Benthic Macroalgae

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaopeng Wang ◽  
Mengyin Wu ◽  
Bin Wan ◽  
Changtai Niu ◽  
Wentao Zheng ◽  
...  
Keyword(s):  
Water Content ◽  
Functional Morphology ◽  
South China ◽  
Adaptive Response ◽  
Microbial Mats ◽  
Attachment Structures ◽  
Attachment Strategies ◽  
Benthic Macroalgae

Holdfast morphologies and attachment strategies of benthic macroalgae are somewhat flexible and controlled by both the substrate condition and species. Six forms (tapered base, globose holdfast, composite globose holdfast, discoidal holdfast, rhizoids and horizontal rhizomes) of attachment structures of Ediacaran benthic macroalgae are recognized from the early Ediacaran Lantian biota and late Ediacaran Miaohe biota in South China based on functional morphology. Each form is considered either adapted to firm substrates that dominate the Precambrian seafloor, or soft substrates that are more common in the Phanerozoic. The results show a diversification in both holdfast morphology and attachment strategies of macroalgae during the Ediacaran Period. In the early Ediacaran Lantian biota, none of the benthic macroalgae is adapted to soft substrates, while in the late Ediacaran Miaohe biota, a considerable number (41%) of species are adapted to relatively soft substrates. This shift might be an adaptive response to the diversification of macroalgae and a changing substrate condition during the Ediacaran Period: the decline of microbial mats and increase of water content in the sediments in the Ediacaran.

scholarly journals Constraining Mantle Heterogeneity beneath the South China Sea: A New Perspective on Magma Water Content

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 410 ◽  
Author(s):  
Wei Wang ◽  
Fengyou Chu ◽  
Xichang Wu ◽  
Zhenggang Li ◽  
Ling Chen ◽  
...  
Keyword(s):  
South China Sea ◽  
Water Content ◽  
South China ◽  
Mantle Source ◽  
Melt Inclusions ◽  
The South China Sea ◽  
Spreading Ridge ◽  
Mantle Heterogeneity ◽  
The South ◽  
China Sea

The nature of upper mantle is important to understand the evolution of the South China Sea (SCS); thus, we need better constrains on its mantle heterogeneity. Magma water concentration is a good indicator, but few data have been reported. However, the rarity of glass and melt inclusions and the special genesis for phenocrysts in SCS basalts present challenges to analyzing magmatic water content. Therefore, it is possible to estimate the water variations through the characteristics of partial melting and magma crystallization. We evaluated variations in Fe depletion, degree of melt fractions, and mantle source composition along the fossil spreading ridge (FSR) using SCS basalt data from published papers. We found that lava from the FSR 116.2° E, FSR 117.7° E, and non-FSR regions can be considered normal lava with normal water content; in contrast, lava from the FSR 117° E-carbonatite and 114.9–115.0° E basalts have higher water content and show evidence of strong Fe depletion during the fractional crystallization after elimination of the effects of plagioclase oversaturation. The enriched water in the 117° E-carbonatite basalts is contained in carbonated silicate melts, and that in the 114.9–115.0° E basalts results from mantle contamination with the lower continental crust. The lava from the 117° E-normal basalt has much lower water content because of the lesser influence of the Hainan plume. Therefore, there must be a mantle source compositional transition area between the southwestern and eastern sub-basins of the SCS, which have different mantle evolution histories. The mantle in the west is more affected by contamination with continental materials, while that in the east is more affected by the Hainan mantle plume.

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

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.

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.

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.

The effect of water content on the shear strength characteristics of granitic soils in South China

2019 ◽  
Vol 187 ◽  
pp. 50-59 ◽  
Author(s):  
Yujie Wei ◽  
Xinliang Wu ◽  
Jinwen Xia ◽  
Gerald A. Miller ◽  
Chongfa Cai ◽  
...  
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
South China ◽  
Strength Characteristics ◽  
Effect Of Water

scholarly journals Nondestructive Measurement of Water Content and Moisture Migration of Unsaturated Red Clays in South China

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Junhui Zhang ◽  
Qingping Jiang ◽  
Yuqing Zhang ◽  
Liangliang Dai ◽  
Houxuan Wu
Keyword(s):  
Ground Water ◽  
Water Content ◽  
Water Level ◽  
South China ◽  
Ground Water Level ◽  
Dry Density ◽  
Red Clay ◽  
Moisture Migration ◽  
X Ray ◽  
Highway Embankments

To reveal the moisture migration mechanism of the unsaturated red clays, which are sensitive to water content change and widely distributed in South China, and then rationally use them as a filling material for highway embankments, a method to measure the water content of red clay cylinders using X-ray computed tomography (CT) was proposed and verified. Then, studies on the moisture migrations in the red clays under the rainfall and ground water level were performed at different degrees of compaction. The results show that the relationship between dry density, water content, and CT value determined from X-ray CT tests can be used to nondestructively measure the water content of red clay cylinders at different migration time, which avoids the error reduced by the sample-to-sample variation. The rainfall, ground water level, and degree of compaction are factors that can significantly affect the moisture migration distance and migration rate. Some techniques, such as lowering groundwater table and increasing degree of compaction of the red clays, can be used to prevent or delay the moisture migration in highway embankments filled with red clays.

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