Doushantuo Formation In China Research Articles

Spatial distribution of organic functional groups in Ediacaran acritarchs from the Doushantuo Formation in South China as revealed by micro-FTIR spectroscopy

Raman and Fourier-transform infrared (FTIR) microspectroscopic analyses were performed to examine the chemical signatures and their spatial distribution of organic-walled microfossils together with organic matter (OM) in a black chert nodule from the Ediacaran (635–551 Ma) Doushantuo Formation in China. Raman spectral parameters (I-1350/1600 values) reveal that the acritarchs, bundled filaments, and OM have different degrees of structural order, and that there is no significant difference in I-1350/1600 values among the different portions of individual acritarchs (i.e., inner structure, inner membrane, and outer wall). The IR mapping reveals portion-specific chemical signatures within the individual acritarch specimens. The inner membrane of Tianzhushania contains aliphatic C-H bonds. The acritarchs, including Tianzhushania, show chemically four types of inner structures: (1) aromatic C-H-rich type, (2) aliphatic C-H-rich type, (3) aromatic/aliphatic C-H-poor type, or (4) heterogeneous. All of the examined acritarchs have aromatic C-H rich outer wall, irrespective of the presence/absence of processes. These features support a eukaryotic cyst origin, although it is difficult to determine whether the acritarchs correspond to the cysts of Protista or Metazoa. The bundled filaments also consist of an aromatic C-H bond, but its origin is uncertain. The OM shows a high degree of variation in Raman spectral I-1350/1600 values, as does the IR spectral intensity ratio of asymmetric aliphatic CH3/CH2, alongside a heterogeneous spatial distribution of aromatic and aliphatic C-H bands. This suggests the contribution of various precursors derived from dead microbial cell debris and extracellular organic compounds. Overall, these results confirm the presence of diverse microorganisms in the Doushantuo microbiota. Furthermore, the spatial distribution of organic functional groups in individual microfossils could provide clues about the taxonomy of microfossils of unknown origin.

Diversification of heterotrophic protists at the eve of Cambrian explosion

Molecular clocks suggest that at least some heterotrophic protists, such as foraminifera, testate amoebae and tintinnids, were present in ecosystems as far back as 1000 Ma. Vase-shaped microfossils of earlier testate amoebae from the supergroups Amoebozoa and Rhizaria occur globally in pre-Sturtian shallow marine deposits, and have thus been considered as a potential biostratigraphic tool, especially at a time span between 789 and 729 Ma. Organic-rich three-dimensional tests having flask-like shapes, constricted necks, distinct and often thickened collars of possible tintinnids affinity were recovered from 715 to 635 Ma carbonate deposits from the Tsagaan Oloom Formation, southwestern Mongolia. Phosphatic scaly structures of unknown affinity were reported from mid-Neoproterozoic (pre-Sturtian) strata of northwest Canada. Anyhow, the fossil records of heterotrophic protists aftermath the Cryogenian age are still shroud in mist. The three putative ciliate fossils, namely Eotintinnopsis, Wujiangella, and Yonyangella from the Neoproterozoic Doushantuo Formation in China were reassessed and likely to be taphonomically and diagenetically distorted and altered acritarchs. Here, we report a diverse assemblage of problematic from the terminal Ediacaran Gaojiashan biota in southern Shaanxi Province, China. Apart from the renowned vase-shaped Protolagena and Sicylagena, likely thought to be the earliest foraminifera, new findings include a hollow pear-shaped structure with long extending, a solid spindle-shaped structure with straight narrow central tube. Possible foraminifera from the Gaojiashan biota may throw welcome new light to the long obscured history of heterotrophic protists at the eve of the Cambrian explosion.

Ediacaran Doushantuo-type biota discovered in Laurentia

The Ediacaran period (635–541 Ma) was a time of major environmental change, accompanied by a transition from a microbial world to the animal world we know today. Multicellular, macroscopic organisms preserved as casts and molds in Ediacaran siliciclastic rocks are preserved worldwide and provide snapshots of early organismal, including animal, evolution. Remarkable evolutionary advances are also witnessed by diverse cellular and subcellular phosphatized microfossils described from the Doushantuo Formation in China, the only source showing a diversified assemblage of microfossils. Here, we greatly extend the known distribution of this Doushantuo-type biota in reporting an Ediacaran Lagerstätte from Laurentia (Portfjeld Formation, North Greenland), with phosphatized animal-like eggs, embryos, acritarchs, and cyanobacteria, the age of which is constrained by the Shuram–Wonoka anomaly (c. 570–560 Ma). The discovery of these Ediacaran phosphatized microfossils from outside East Asia extends the distribution of the remarkable biota to a second palaeocontinent in the other hemisphere of the Ediacaran world, considerably expanding our understanding of the temporal and environmental distribution of organisms immediately prior to the Cambrian explosion.

Nano-Scale Spheroids and Fossils from the Ediacaran Doushantuo Formation in China

Nano-Scale Spheroids and Fossils from the Ediacaran Doushantuo Formation in China

On the coevolution of Ediacaran oceans and animals

Fe speciation and S-isotope of pyrite data from the terminal Proterozoic Sheepbed Formation in Canada and Doushantuo Formation in China reveal that ocean deep waters were anoxic after the global glaciations (snowball Earth) ending 635 million years ago, but that marine sulfate concentrations and inferentially atmospheric oxygen levels were higher than before the glaciations. This supports a long-postulated link between oxygen levels and the emergence of eumetazoa. Subsequent ventilation of the deep ocean, inferred from shifts in Fe speciation in Newfoundland (previously published data) and western Canada (this report), paved the way for Ediacaran macrobiota to colonize the deep seafloors.

Precambrian animal diversity: putative phosphatized embryos from the Doushantuo Formation of China.

Putative fossil embryos and larvae from the Precambrian phosphorite rocks of the Doushantuo Formation in Southwest China have been examined in thin section by bright field and polarized light microscopy. Although we cannot completely exclude a nonbiological or nonmetazoan origin, we identified what appear to be modern cnidarian developmental stages, including both anthozoan planula larvae and hydrozoan embryos. Most importantly, the sections contain a variety of small (</=200 microm) structures that greatly resemble gastrula stage embryos of modern bilaterian forms.