Abundant graphite particles occur in amphibolite-grade quartzite of the Archean–Paleoproterozoic Wutai Metamorphic Complex in the Wutaishan area of North China. Petrographic thin section observations suggest that the graphite particles occur within and between quartzite clasts and are heterogeneous in origin. Using HF maceration techniques, the Wutai graphite particles were extracted for further investigation. Laser Raman spectroscopic analysis of a population of extracted graphite discs indicated that they experienced a maximum metamorphic temperature of 513 ± 50°C, which is consistent with the metamorphic grade of the host rock and supports their indigenicity. Scanning and transmission electron microscopy revealed that the particles bear morphological features (such as hexagonal sheets of graphite crystals) related to metamorphism and crystal growth, but a small fraction of them (graphite discs) are characterized by a circular morphology, distinct marginal concentric folds, surficial wrinkles, and complex nanostructures. Ion microprobe analysis of individual graphite discs showed that their carbon isotope compositions range from −7.4‰ to −35.9‰ V-PDB (Vienna Pee Dee Belemnite), with an average of −20.3‰, which is comparable to bulk analysis of extracted carbonaceous material. The range of their size, ultrastructures, and isotopic signatures suggests that the morphology and geochemistry of the Wutai graphite discs were overprinted by metamorphism and their ultimate carbon source probably had diverse origins that included abiotic processes. We considered both biotic and abiotic origins of the carbon source and graphite disc morphologies and cannot falsify the possibility that some circular graphite discs characterized by marginal folds and surficial wrinkles represent deflated, compressed, and subsequently graphitized organic-walled vesicles. Together with reports by other authors of acanthomorphic acritarchs from greenschist-amphibolite-grade metamorphic rocks, this study suggests that it is worthwhile to examine carbonaceous materials preserved in highly metamorphosed rocks for possible evidence of ancient life.
Research Article| May 01, 2004 New constraints on the ages of Neoproterozoic glaciations in south China Chuanming Zhou; Chuanming Zhou 1Nanjing Institute of Geology and Paleontology, Nanjing 210008, China, and Department of Geosciences, Virginia Polytechnic Institute, Blacksburg, Virginia 24061, USA Search for other works by this author on: GSW Google Scholar Robert Tucker; Robert Tucker 2Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri 63130, USA Search for other works by this author on: GSW Google Scholar Shuhai Xiao; Shuhai Xiao 3Department of Geosciences, Virginia Polytechnic Institute, Blacksburg, Virginia 24061, USA Search for other works by this author on: GSW Google Scholar Zhanxiong Peng; Zhanxiong Peng 4Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri 63130, USA Search for other works by this author on: GSW Google Scholar Xunlai Yuan; Xunlai Yuan 5Nanjing Institute of Geology and Paleontology, Nanjing 210008, China Search for other works by this author on: GSW Google Scholar Zhe Chen Zhe Chen 5Nanjing Institute of Geology and Paleontology, Nanjing 210008, China Search for other works by this author on: GSW Google Scholar Author and Article Information Chuanming Zhou 1Nanjing Institute of Geology and Paleontology, Nanjing 210008, China, and Department of Geosciences, Virginia Polytechnic Institute, Blacksburg, Virginia 24061, USA Robert Tucker 2Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri 63130, USA Shuhai Xiao 3Department of Geosciences, Virginia Polytechnic Institute, Blacksburg, Virginia 24061, USA Zhanxiong Peng 4Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri 63130, USA Xunlai Yuan 5Nanjing Institute of Geology and Paleontology, Nanjing 210008, China Zhe Chen 5Nanjing Institute of Geology and Paleontology, Nanjing 210008, China Publisher: Geological Society of America Received: 22 Oct 2003 Revision Received: 12 Jan 2004 Accepted: 14 Jan 2004 First Online: 02 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2004) 32 (5): 437–440. https://doi.org/10.1130/G20286.1 Article history Received: 22 Oct 2003 Revision Received: 12 Jan 2004 Accepted: 14 Jan 2004 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Chuanming Zhou, Robert Tucker, Shuhai Xiao, Zhanxiong Peng, Xunlai Yuan, Zhe Chen; New constraints on the ages of Neoproterozoic glaciations in south China. Geology 2004;; 32 (5): 437–440. doi: https://doi.org/10.1130/G20286.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The most complete Neoproterozoic successions in south China contain three diamictite intervals in the Changan, Tiesiao, and Nantuo Formations. The youngest and most widespread Nantuo glacial deposit overlies the Datangpo Formation and underlies the fossil- rich Doushantuo Formation. Previous authors have correlated the Nantuo diamictite to either Sturtian or Marinoan glacial deposits elsewhere. Here we report sedimentary and δ13C chemostratigraphic data of the Doushantuo cap dolostone, which overlies the Nantuo Formation. Facies-dependent variation in δ13C is interpreted as evidence for spatial heterogeneity in δ13C and/or temporal diachroneity in the initiation of cap carbonate sedimentation. Sedimentary and chemostratigraphic data are indicative of a Marinoan age for the Nantuo glaciation. This inference is supported by a new U-Pb zircon age of 663 ± 4 Ma from a tuffaceous bed in the Datangpo Formation. The new date and other isotopic ages from south China constrain the age of the Changan and Tiesiao glaciation(s) as between 761 ± 8 Ma and 663 ± 4 Ma, and the Nantuo glaciation as between 663 ± 4 Ma and 599 ± 4 Ma. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Abstract Non-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.
Research Article| April 01, 2005 Skeletogenesis and asexual reproduction in the earliest biomineralizing animal Cloudina Hong Hua; Hong Hua 1Department of Geology and Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, China Search for other works by this author on: GSW Google Scholar Zhe Chen; Zhe Chen 2Nanjing Institute of Geology and Paleontology, Nanjing 210008, China Search for other works by this author on: GSW Google Scholar Xunlai Yuan; Xunlai Yuan 2Nanjing Institute of Geology and Paleontology, Nanjing 210008, China Search for other works by this author on: GSW Google Scholar Luyi Zhang; Luyi Zhang 3Xi'an Institute of Geology and Mineral Resources, Xi'an 710054, China Search for other works by this author on: GSW Google Scholar Shuhai Xiao Shuhai Xiao 4Department of Geosciences, Virginia Polytechnic Institute, Blacksburg, Virginia 24061, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Hong Hua 1Department of Geology and Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, China Zhe Chen 2Nanjing Institute of Geology and Paleontology, Nanjing 210008, China Xunlai Yuan 2Nanjing Institute of Geology and Paleontology, Nanjing 210008, China Luyi Zhang 3Xi'an Institute of Geology and Mineral Resources, Xi'an 710054, China Shuhai Xiao 4Department of Geosciences, Virginia Polytechnic Institute, Blacksburg, Virginia 24061, USA Publisher: Geological Society of America Received: 13 Sep 2004 Revision Received: 16 Dec 2004 Accepted: 17 Dec 2004 First Online: 02 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2005) 33 (4): 277–280. https://doi.org/10.1130/G21198.1 Article history Received: 13 Sep 2004 Revision Received: 16 Dec 2004 Accepted: 17 Dec 2004 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Hong Hua, Zhe Chen, Xunlai Yuan, Luyi Zhang, Shuhai Xiao; Skeletogenesis and asexual reproduction in the earliest biomineralizing animal Cloudina. Geology 2005;; 33 (4): 277–280. doi: https://doi.org/10.1130/G21198.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The tubular fossil Cloudina is emerging as an important Ediacaran index fossil. However, its morphology, skeletogenesis, reproduction, and phylogenetic affinity have not been fully resolved. New material from the Dengying Formation of south China confirms that Cloudina tubes consist of eccentrically and sometimes deeply nested funnels and that the tubes lack transverse cross-walls, inconsistent with the traditional cone-in-cone morphological reconstruction. Tube walls are composed of micrometer-sized, more or less equant crystals. A number of Cloudina tubes branch dichotomously, in which daughter funnels split within parent ones. The Cloudina animal is interpreted to have been able to initiate biomineralization of new funnels within old ones. Its skeleton was probably secreted as calcite crystals suspended in organic matrix; the crystals do not appear to have nucleated and grown on a sheeted substrate. It was clearly capable of asexual reproduction, through budding within parent funnels rather than at the apertural end. The morphology, skeletogenesis, and asexual reproduction of Cloudina are broadly similar to modern serpulid annelids, indicating possible phylogenetic relationships or morphological convergence. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Phosphatic sediments of the Late Neoproterozoic (ca. 600 million years old [Myr]) Doushantuo Formation at Weng'an, South China, contain fossils of multicellular algae preserved in anatomical detail. As revealed by light microscopy and scanning electron microscopy, these fossils include both simple pseudoparenchymatous thalli with apical growth but no cortex-medulla differentiation and more complex thalli characterized by cortex-medulla differentiation and structures interpretable as carposporophytes, suggesting a multiphasic life cycle. Simple pseudoparenchymatous thalli, represented by Wengania, Gremiphyca, and Thallophycoides, are interpreted as stem group florideophytes. In contrast, complex pseudoparenchymatous thalli, such as Thallophyca and Paramecia, compare more closely to fossil and living corallinaleans than to other florideophyte orders, although they also differ in some important aspects (e.g., lack of biocalcification). These more complex thalli are interpreted as early stem group corallinaleans that diverged before Paleozoic stem groups such as Arenigiphyllum, Petrophyton, Graticula, and Archaeolithophyllum. This phylogenetic interpretation implies that (1) the phylogenetic divergence between the Florideophyceae and its sister group, the Bangiales, must have taken place before Doushantuo time-an inference supported by the occurrence of bangialean fossils in Mesoproterozoic rocks; (2) the initial diversification of the florideophytes occurred no later than the Doushantuo time; and (3) the corallinalean clade had a "soft" (uncalcified) evolutionary history in the Neoproterozoic before evolving biocalcification in the Paleozoic and undergoing crown group diversification in the Mesozoic.
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