Shibantan Member Research Articles

Ubiquitous occurrence of organogenic dolomite in a late Ediacaran limestone-dominated succession from the Eastern Yangtze Gorges area of South China

The widespread occurrence of dolostones in Paleozoic and Precambrian sequences stands in stark contrast to the difficulty of precipitating dolomite in experiments at low temperature under abiotic conditions. The discoveries of dolomite within modern microbial mats and the successful synthesis of proto-dolomite under ambient conditions catalyzed by various microorganisms and organic molecules lend support to the development of organogenic dolomite models. Despite this, convincing evidence for ancient primary dolomite precipitation is rare, mainly due to post-depositional modifications of original textures and mineralogy. Here we present petrographic, mineralogical and C-isotopic data of carbonates preserving primary sedimentary textures in the late Ediacaran Shibantan Member of the Dengying Formation from the eastern Yangtze Gorges area, South China. These carbonates are characterized by calcite layers intercalated with millimeter-thick, organic-rich layers that contain up to 50 % dolomite. Petrographic observations and Raman imaging show that the dolomite occurs preferentially in microbial mats and is closely associated with organic matter. Scanning electron microscopy also revealed the presence of Mg-rich nanoscopic carbonate aggregates and ribbon-like microstructures akin to mineralized extracellular polymeric substances (EPS) in mat layers. These observations are inconsistent with replacive origins but instead support an organogenic origin for the Shibantan dolomite. The relatively high TOC (total organic carbon) contents and consistently positive δ13Ccarb values (up to +4.8 ‰) suggest enhanced burial of organic carbon produced in microbial mats during the Shibantan deposition. Subsequent organic degradation by microorganisms in anoxic, early diagenetic environments likely promoted the ubiquitous formation of organogenic dolomite in Shibantan microbial mats. Our study highlights the important roles of organogenic dolomites in interpreting the wide occurrence of Paleozoic and Precambrian dolostones.

Interaction of Shibantan Biota and environment in the terminal Ediacaran ocean: Evidence from I/(Ca+Mg) and sulfur isotopes

The terminal Ediacaran (∼551–539 Ma) was a crucial period in Earth’s history that witnessed the first appearance of skeletonized animals and complex ecosystems (e.g., the Shibantan Biota) in the ocean. However, the trigger for such biological innovations and their feedbacks to the environment are still poorly understood. In this study, to explore possible interactions between the Shibantan Biota and the oceanic environment, we carried out an integrated investigation of I/(Ca+Mg) along with sulfur isotopes of carbonate-associated sulfate (δ34SCAS) and pyrite (δ34Spy) in the Shibantan Member of the Dengying Formation at Wuhe (South China) where the Shibantan Biota was recovered. Our I/(Ca+Mg) profile yields fluctuating values in the range of 0.03 to 1.86 μmol/mol, corresponding to oxygen concentrations between 1–3 μM and 20–70 μM in the water column of the study area. This result indicates that the oxygen levels in shallow-water environments of the terminal Ediacaran ocean were generally low and the Shibantan Biota must have had low physiological requirements of oxygen. Variably high δ34SCAS values (+31.8‰ to +55.7‰, mean ± 1σ: +41.0 ± 5.2‰) were observed in studied unit, implying low sulfate concentrations in the terminal Ediacaran ocean, consistent with contemporaneous expansion of seawater anoxia. Furthermore, isotopically superheavy pyrites (i.e., δ34Spy > δ34SCAS) are present in the lower Shibantan Member, concurrent with the occurrence of bioturbation in the sediments, suggesting controls by microbial sulfate reduction (MSR) in sulfate-limited porewaters followed by preferential re-oxidation of 32S-riched H2S under the influence of burrowing organisms. This finding supports that burrowing activity of infaunas of the Shibantan Biota may have enhanced sediment porewater oxygenation, thus likely expanding the ecosystem space available to early animals. Our study thus provides new insights into the coevolution of early animals and terminal Ediacaran ocean environments.

A new approach for investigating spatial relationships of ichnofossils: a case study of Ediacaran–Cambrian animal traces

AbstractTrace fossils record foraging behaviors, the search for resources in patchy environments, of animals in the rock record. Quantification of the strength, density, and nature of foraging behaviors enables the investigation of how these may have changed through time. Here, we present a novel approach to explore such patterns using spatial point process analyses to quantify the scale and strength of ichnofossil spatial distributions on horizontal bedding planes. To demonstrate the utility of this approach, we use two samples from the terminal Ediacaran Shibantan Member in South China (between 551 and 543 Ma) and the early Cambrian Nagaur Sandstone in northwestern India (between 539 and 509 Ma). We find that ichnotaxa on both surfaces exhibited significant nonhomogeneous lateral patterns, with distinct levels of heterogeneity exhibited by different types of trace fossils. In the Shibantan, two ichnotaxa show evidence for mutual positive aggregation over a shared resource, suggesting the ability to focus on optimal resource areas. Trace fossils from the Nagaur Sandstone exhibit more sophisticated foraging behavior, with greater niche differentiation. Critically, mark correlation functions highlight significant spatial autocorrelation of trace fossil orientations, demonstrating the greater ability of these Cambrian tracemakers to focus on optimal patches. Despite potential limitations, these analyses hint at changes in the development and optimization of foraging at the Ediacaran/Cambrian transition and highlight the potential of spatial point process analysis to tease apart subtle differences in behavior in the trace fossil record.

Dickinsonia from the Ediacaran Dengying Formation in the Yangtze Gorges area, South China

Dickinsonia is an iconic fossil of the Ediacara biota (~575–539 Ma). It was previously known from siliciclastic successions of the White Sea assemblage in Australia, Baltica, and possibly India. Here we describe Dickinsonia sp. from the terminal Ediacaran Shibantan Member limestone (ca. 551–543 Ma) of the Dengying Formation in the Yangtze Gorges area of South China. The stratigraphic distribution of Ediacara-type fossils in the Shibantan Member indicates that this biota uniquely preserves both the White Sea and Nama assemblages in stratigraphic succession. The new data presented here suggests that Dickinsonia had wider paleogeographic and paleoenvironmental distributions, implying its strong dispersal capability and environmental tolerance.

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

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

Terminal Ediacaran carbonate tempestites in the eastern Yangtze Gorges area, South China

The terminal Ediacaran Dengying Formation in the eastern Yangtze Gorges area, South China is well known for hosting diverse Ediacaran-type macrofossils and trace fossils. However, the depositional processes of this carbonate succession are still poorly known. Here we present detailed sedimentological data on the Dengying carbonates in four sections across the eastern Yangtze Gorges area, with an emphasis on tempestites in limestones of the Shibantan Member of Dengying Formation that have largely been overlooked. The Shibantan limestones in the studied sections contain extensive autochthonous microbial mats and storm-related deposits, including calcirudite, individual swaley cross-stratified calcarenites, hummocky cross-stratified fine- to very fine-grained calcarenites, normally graded calcarenites, calcarenite-calcisiltite beds in discrete units, and soft-sediment deformed beds. The spatial variation of facies suggests that the Shibantan Member was deposited on a carbonate ramp with an intra-ramp lagoon. With the upward shallowing of water depth and progradation of storm-generated sediments, the ramp gradually become steeper, as characterized by the occurrence of soft-sediment deformation structures and graded bedding in the middle of the member. The abundance of tempestites in the Shibantan limestones suggests that the Shibantan Basin was located in low-latitude regions frequently affected by tropical storms, consistent with previous paleogeographic reconstructions. Storm events probably brought nutrients into the environment and contributed to the rapid burial and preservation of macrofossils. The Shibantan limestones thus provide another example of a massflow-related taphonomic window for the Ediacaran organisms that is comparable to the fossil preservation style in the Ediacaran siliciclastic rocks.

Late Ediacaran trackways produced by bilaterian animals with paired appendages.

Ediacaran trace fossils provide key paleontological evidence for the evolution of early animals and their behaviors. Thus far, however, this fossil record has been limited to simple surface trails and relatively shallow burrows. We report possible trackways, preserved in association with burrows, from the terminal Ediacaran Shibantan Member (ca. 551 to ca. 541 million years ago) in the Yangtze Gorges area of South China. These trace fossils represent the earliest known trackways. They consist of two rows of imprints arranged in poorly organized series or repeated groups. These trackways may have been produced by bilaterian animals with paired appendages, although the phylum-level phylogenetic affinity of the trace makers remains unknown. It is possible that the trackways and associated burrows were produced by the same trace maker, indicating a complex behavior involving both walking and burrowing. Together, these trackways and burrows mark the arrival of a new era characterized by an increasing geobiological footprint of bilaterian animals.

Stable carbon isotopes of sedimentary kerogens and carbonaceous macrofossils from the Ediacaran Miaohe Member in South China: Implications for stratigraphic correlation and sources of sedimentary organic carbon

Ediacaran stratigraphic correlation depends on the integration of paleontological and δ13Ccarb data. However, these data often come from different lithologies (e.g., shales vs. carbonates), making it difficult to directly link biostratigraphic and chemostratigraphic markers. Ediacaran successions in South China consist of mixed carbonates and shales, offering an opportunity for integrated biostratigraphic and chemostratigraphic investigations. Black shales of the Ediacaran Miaohe Member in the Yangtze Gorges area contain macroalgae and Ediacara-type macrofossils, both preserved as carbonaceous compressions. The Miaohe Member has been traditionally regarded as an equivalent to Member IV of the uppermost Doushantuo Formation that records part of the Shuram negative δ13Ccarb excursion in South China. Thus, the Miaohe Member may have the potential to clarify the stratigraphic relationship between Ediacara-type fossils and the Shuram excursion. Recently, however, the Miaohe Member has been partially correlated with the Shibantan Member of the Dengying Formation (the “A” correlation) or partially with Member IV (the “Z” correlation). These correlations have different implications for the relationship between the Miaohe Member and the Shuram excursion. Here we test these two correlations using δ13C data of sedimentary kerogen or total organic carbon (δ13CorgTOC), taking advantage of the distinct δ13CorgTOC values between the Shibantan Member and Member IV. Our data show that δ13CorgTOC of the Miaohe Member is more similar to that of Member IV than to Shibantan Member, providing tentative support for the “Z” correlation. In addition, we also analyzed δ13Corg of individual carbonaceous compression fossils (δ13Corgtaxon), which have lower carbon isotope values than TOC. The data suggest that oxygenic photosynthesizers (e.g., macroalgae, cyanobacteria, and eukaryotic phytoplankton) were not the only contributors to sedimentary TOC. Methylotrophs, photoautotrophs, and chemoautotrophs living in anoxic waters or at the oxycline may have fixed recycled CO2 derived from organic carbon remineralization, thus contributing a significant amount of 13C-depleted organic carbon to sedimentary kerogen in the Miaohe Member.

Beyond the stony veil: Reconstructing the Earth’s earliest large animal traces via computed tomography X-ray imaging

Trace fossils are superb lines of evidence for examining the ancient biologic world because they offer an opportunity to infer behavioral ecology of organisms. However, traces can be difficult to parse from their matrix, which leads to the loss of important morphological and behavioral data. This is especially true for the earliest marine animal traces from the Ediacaran Period (635–541Ma), which are usually small (<5mm in diameter) and simple (mostly small horizontal trails and burrows), and are sometimes difficult to be distinguished from co-existing tubular body fossils. There is also evidence that the prevalence of microbial substrates in Ediacaran oceans may have influenced emerging trace makers in non-actualistic ways from a late Phanerozoic perspective (e.g., microbial mats may have facilitated a strong geochemical gradient across the sediment-water interface). Therefore, the discovery of the relatively large traces of Lamonte trevallis from the Ediacaran Shibantan Member of the Denying Formation (∼551–541Ma) in the Yangtze Gorges area of South China provides a unique opportunity to study early bioturbators. These trace fossils are large enough and have sufficient compositional contrast (relative to the matrix) for in situ analysis via X-ray computed tomography (CT) and microcomputed tomography (microCT). Each analytical method has its own advantages and disadvantages. CT scans can image larger specimens, but cannot adequately resolve small features of interest. MicroCT scans can achieve higher resolution, but can only be used with small samples and may involve more post-processing than CT scans. As demonstrated in this study, X-ray CT and microCT in combination with other 3D imaging techniques and resources have the potential to resolve the 3D morphology of Ediacaran trace fossils. A new Volumetric Bioturbation Intensity (VBI) is also proposed, which quantifies whole rock bioturbation using 3D analysis of subsurface traces. Combined with the ability to examine trace fossils in situ, the VBI can enhance our view of ancient ecologies and life’s enduring relationship with sediments.

A new modular palaeopascichnid fossil Curviacus ediacaranus new genus and species from the Ediacaran Dengying Formation in the Yangtze Gorges area of South China

AbstractNon-biomineralizing Ediacaran macrofossils are rare in carbonate facies, but they offer valuable information about their three-dimensional internal anatomy and can broaden our view about their taphonomy and palaeoecology. In this study, we report a new Ediacaran fossil, Curviacus ediacaranus new genus and species, from bituminous limestone of the Shibantan Member of the Dengying Formation in the Yangtze Gorges area of South China. Curviacus is reconstructed as a benthic modular organism consisting of serially arranged and crescent-shaped chambers. The chambers are confined by chamber walls that are replicated by calcispars, and are filled by micritic sediments. Such modular body construction is broadly similar to the co-occurring Yangtziramulus zhangii and other Ediacaran modular fossils, such as Palaeopascichnus. The preservation style of Curviacus is similar to Yangtziramulus, although the phylogenetic affinities of both genera remain unresolved. The new fossil adds to the diversity of Ediacaran modular organisms.

Stratigraphic position of the Ediacaran Miaohe biota and its constrains on the age of the upper Doushantuo δ13C anomaly in the Yangtze Gorges area, South China

The siliceous shale unit that hosts the Ediacaran Miaohe biota in the Yangtze Gorges area, commonly referred to as the Miaohe Member, has an age of 551±0.7Ma. This unit is thought to be time-equivalent with the Doushantuo Member IV, which marks the top of the upper Doushantuo negative δ13C excursion. New bio-, sequence- and chemostratigraphic studies presented here demonstrate that the Miaohe Member is significantly younger than the Doushantuo Member IV, most likely time-equivalent with the lower Shibantan Member of the Dengying Formation. The new findings indicate that the top of the Doushantuo Formation, i.e., the top of the upper Doushantuo/Shuram δ13C excursion, should be much older than 551Ma (likely ≥560Ma). The ocean oxygenation event documented from the Doushantuo Member IV black shales should also be older than 560Ma and predate the Miaohe biota for more than 10Ma.

Depositional dynamics of a bituminous carbonate facies in a tectonically induced intra-platform basin: the Shibantan Member (Dengying Formation, Ediacaran Period)

The Ediacaran Shibantan Member (Dengying Formation, South China) is characterised by a black, laminated bituminous limestone facies with diverse Ediacara-type organisms and trace fossils. However, still little is known about the evolution of the Shibantan basin and its sedimentary dynamics. A detailed sedimentological characterisation revealed that the Shibantan Member was deposited on a carbonate ramp system linked to an intra-platform basin. Evaporitic dolomites of the Hamajing Member (representing sub- to supratidal inner ramp environments above fair weather wave base) are sharply overlain by black, laminated limestones of the lower Shibantan Member, representing a subtidal lower- to middle ramp environment close to the storm wave base. This facies-shift implies a sudden local deepening event, probably due to a tectonically induced increase in subsidence. The Shibantan basin was subsequently filled as evidenced by the gradual transition into dark wavy dolomites deposited in a subtidal middle-ramp environment (i.e. between storm- and fair weather wave bases) and, eventually, the upper Dengying Formation (i.e. the Baimatuo Member), which represents the same depositional environments as the Hamajing Member. Sedimentation in the Shibantan basin was highly dynamic as evidenced by a distinct slumping horizon and mass-flow deposits, partly possibly due to synsedimentary tectonic processes. A microbial mat associated biota which includes Ediacara-type fossils is restricted to the lower Shibantan Member. The close spatial relationship between allochthonous event deposits and autochthonous fossil associations in this setting implies that the event deposits were not only important for the preservation of fossils, but probably also for the supply of nutrients.

Assessing Possibilities and Limitations for Biomarker Analyses on Outcrop Samples: A Case Study on Carbonates of the Shibantan Member (Ediacaran Period, Dengying Formation, South China)

The Shibantan Member (Dengying Formation, South China) represents one of only two carbonate settings with Ediacara-type organisms and offers a rare opportunity to study the biogeochemistry of these ecosystems. To evaluate possibilities and limitations for future biomarker studies on fossil-bearing outcrop samples of the Shibantan Member, we analysed the spatial distribution of hydrocarbons in extractable organic matter (i.e. bitumen) on a millimetre scale. Our study demonstrates that the sample and most likely also other rocks from the same setting are contaminated with petroleum-derived compounds that bear the potential for erroneous interpretations in palaeo-reconstructions. The contamination was revealed by distribution patterns and amounts of extractable n-alkanes and acyclic isoprenoids. The contamination is linked to the external weathering surfaces but also to cracks within the rock, and the extent most likely depends on concentration gradients between these contamination sources. Here we show that contamination can successfully be distinguished from syngenetic signals obtained from non-extractable organic matter (i.e. kerogen) using catalytic hydropyrolysis (HyPy). However, we observed that decalcification is necessary to achieve sufficient yields of kerogen-bound hydrocarbons and to avoid artificial alteration of the biomarker signals due to matrix effects.

Geobiology of a palaeoecosystem with Ediacara-type fossils: The Shibantan Member (Dengying Formation, South China)

Despite the importance of palaeoecosystems with Ediacara-type fossils for the early evolution of metazoans, only little is known about the interplay of geological and biological processes in these environments. The reason is that sedimentary structures, biogenic structures and (bio-) geochemical signatures (e.g. hydrocarbon biomarkers) are commonly not well preserved due to the predominance of volcanic and siliciclastic lithologies. The Shibantan Member (Dengying Formation, South China) is one of only few carbonate settings with Ediacara-type organisms worldwide and its lithology promises an excellent preservation of sedimentary facies and (bio-) geochemical signatures. Here we provide the first comprehensive geobiological characterisation of the Shibantan Member in order to reconstruct the interplay between sedimentary and (bio-) geochemical processes and to assess the microbial activities in the palaeoecosystem with Ediacara-type fossils. Facies analyses revealed that carbonate and organic matter were autochthonously formed by (bio-) geochemical processes linked to microbial mats. However, the material was frequently reworked and re-deposited within the same setting (i.e. para-autochthonous) as evidenced by small-scale (hummocky-) cross stratification, erosional contacts, lenticular bedding and load casts. Negative Ce anomalies (Ce/Ce*) and low V/Cr ratios demonstrate that molecular O2 was present in the water column, whereas characteristic Ni/Co-, V/(V+Ni), and V/Sc ratios suggest the contemporaneous presence of sub- to anoxic water. Taken together, these observations imply a temporarily stratified water body frequently mixed and ventilated by storms. 13C-enrichments in the Shibantan carbonates (δ13C=+3.29 to +3.98‰, VPDB) together with 13C-depletions of syngenetic n-alkanes cleaved from the extraction residue using catalytic hydropyrolysis (HyPy; δ13C=−31.7 to −36.3‰, VPDB) could indicate a significant withdrawal of 12C by primary producers that thrived within the mats. At the same time, sulphurised biomarkers in the bitumen and HyPy-pyrolysate hint at organic matter decomposition and concomitant sulphide production by sulphate reducing bacteria. When oxygen was available at the sediment–water interface due to mixing by storms, sulphide oxidising bacteria were possibly temporarily favoured. The results demonstrated that palaeoenvironmental conditions dynamically changed through a complex interplay of biogenic and abiogenic processes.

Interactions between Ediacaran animals and microbial mats: Insights from Lamonte trevallis, a new trace fossil from the Dengying Formation of South China

A new ichnogenus and ichnospecies, Lamonte trevallis, is formally described from the Shibantan Member limestone of the upper Ediacaran Dengying Formation, Yangtze Gorges area, South China. It is characterized by horizontal tunnels connected with short vertical burrows and surface trails. The horizontal burrows are elliptical or bilobed in transverse cross-section, preserved in full relief, and filled with carbonate intraclasts, micrites, as well as calcite and silica cements. They occur exclusively in silty, crinkled, and microlaminated layers that are interpreted as amalgamated cyanobacterial microbial mats; no burrows have been found in intraclastic layers adjacent to the microlaminated layers. The vertical traces are filled with the same material as the burrows, but they typically project through the crinkled microlaminae and are exposed on the bedding surface. The surface tracks are always preserved in negative epirelief or positive hyporelief and consist of two parallel series of either sharp scratch marks or small knobs. The burrow infill has δ18Ocarb and δ13Ccarb values distinct from, but intermediate between, microlaminated and intraclastic layers, consistent with petrographic observation that burrow infill consists of a mixture of early carbonate cements, intraclasts, and micrites. Bedding plane bioturbation intensity (20–40%)—measured as percentage of bedding plane area covered by L. trevallis traces—is comparable to similar measurements in pre-trilobite Cambrian carbonates. The exclusive occurrence of L. trevallis within microbial mats may have both taphonomic and ecological significance. These mats may have provided firm substrates and localized geochemical conditions that contributed to the structural integrity of the burrows, and they may have also facilitated early diagenetic cementation of burrow infill, thus facilitating burrow preservation. The close association of these burrows with microbial mats implies that the trace producers actively mined cyanobacterial mats to exploit oxygen or nutrient resources. The trace makers of L. trevallis were better able to utilize the resources around them than many other Ediacaran trace makers and provide an ichnological record of a flourishing benthic ecology in late Ediacaran oceans at the dawn of the agronomic revolution.

Comment on “Trace fossil evidence for Ediacaran bilaterian animals with complex behaviors” by Chen et al. [Precambrian Res. 224 (2013) 690–701

Trace fossils from the Shibantan Member of the Denying Formation (551–541Ma) of South China, interpreted by Chen and colleagues as evidence of undermat feeding, epibenthic locomotion and temporary dwelling of a small worm-like animal (Metazoa, Bilateria), show four features incompatible with that interpretation: (1) bulbous ends, (2) interruptions, (3) variable width, (4) narrow ends and (5) beaded levees. These features are better explained as due to formation of a sorocarp base, looping upward, shape changing, cell aggregation and slime nodules, respectively, of the slug (grex or pseudoplasmodium) phase of a cellular slime mold comparable with living Dictyostelium discoideum (Amoebozoa, Mycetozoa). Another three features are found in worm as well as slime mold trails: (6) transverse markings, (7) central ridge and (8) small size. Similar observations can be made, and mycetozoan affinities considered for comparable trace fossils from the 550Ma Ediacaran Member of South Australia, 558Ma Ust Pinega Formation of Russia, 585–600Ma Tacuari Formation of Uruguay, 1100Ma Chorhat Sandstone of India and 2000–1800Ma Stirling Range Sandstone of Western Australia. Slime molds are terrestrial eucaryotic protists, and may have a fossil record extending back as far as the likely 1900Ma age of aquatic metazoans.

A New Diverse Macrofossil Lagerstätte from the Uppermost Ediacaran of Southwestern China

Abstract: A new macrofossil Lagerstätte was discovered from the uppermost Ediacaran Jiucheng Member at Jinning and Jiangchuan of the eastern Yunnan, yielding numerous diverse well‐preserved thallophyte macrofossils. These include the previously‐known representatives of vendobionts, Vendotaenia and Tyrasotaenia, and the biggish multicellular benthos such as Chuaria‐like and Tawuia‐like fossils, as well as Longfengshaniaceaens with diverse holdfast structures. There are still some other problematic macrofossils with peculiar configurations as well as uncertain relatives. The distinct dominance of the giant, unbranching thallophytes occasionally with holdfast structures distinguishes this assemblage from the other Ediacaran macrofossil Lagerstättes in the Doushantuo Formation at Miaohe, Wenghui and Lantian, and the contemporary assemblage in the Shibantan Member of Dengying Formation, Yangtze Gorges area. This paper outlines the characteristics of some of the multicellular macrofossils from the Jiucheng Member at Jiangchuan. They include some macrofossils with different types of holdfast structure, larger Chuaria‐like and Tawuia‐like morphology and questionable affinities as well. The discovery of greater diverse macrofossil assemblages from the Jiucheng Member of eastern Yunnan has further indicated that an important diversification and evolutionary radiation of metaphytes took place in the latest Ediacaran time. This radiation of large‐scale, benthic metaphyte along with phytoplankton was likely important contributors to the early Cambrian explosion of metazoans.

Late precambrian pennatulids (sea pens) from the eastern Yangtze Gorge, China: Paracharnia gen. nov.

Pennatulids preserved as membranous carbonised compressions from the Shibantan Member, Dengying Formation, Sinian System in the Eastern Yangtze Gorge, Hubei Province represent the first genuine discovery of the late Precambrian Ediacara-type metazoan remains in China. The specimens were initially referred to Charnia Ford 1958 and described as C. dengyingensis by Ding and Chen in 1981. A re-examination of the type material and comparing it with other late Precambrian frond-like forms, particularly those from the Ediacara assemblage of South Australia and from the Charnwood assemblage of England, indicate that this Chinese species represents a distinct genus, Paracharnia gen. nov. Its characteristic polyp leaves, individually free-standing on distinct leaf-stalks along the lateral sides of the median stem, resemble those of many living sea pens represented by Pennatula, and contribute a significant feature to the Precambrian Charniidae Glaessner 1979. Its close association with abundant macroscopic algal remains of Vendotaenia sp. and its proximity to the overlying basal Cambrian small shelly fossil assemblages in the same succession emphasise its palaeontological and biostratigraphic significance.