A new spinicaudatan species Ordosestheria chottsensis from the lower Barremian uppermost Bouhedma Formation of southern Tunisia. Spinicaudatans are large, bivalved crustaceans, which are common components of temporary water bodies, such as inland ponds, floodplain pools, rice field or margins of large lakes. But they can also occur in more saline environments such as large playa lakes and coastal salt flats. Their life cycle is relatively short. Some species can finish their life cycle within two to three weeks, i.e. from hatching from the eggs to the oviposition. Fossil spinicaudatans are often recovered from fine lacustrine mudstones and shales. Because of their wide distribution and quick evolution, fossil clam shrimps are very useful for the subdivision and correlation of non-marine strata. The non-marine Lower Cretaceous strata extend from Morocco to Egypt across the Saharan African, and were deposited along the southern shoreline of the Neotethyan Ocean. The dinosaur fossils from these strata provided important evidence for the breakup of Gondwana and the progressive isolation of the African continent. The non-marine sequences are also of an important socioeconomic importance as one of the global largest freshwater aquifer systems in one of the most arid regions in the world. Recently, Prof. LI Gang’s working group from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and scientists from Tunisa have recovered spinicaudatan Ordosestheria chottsensis from the lower Barremian Bouhedma Formation in the northern Chotts range of southern Tunisia. Ordosestheria was first described from the lower Aptian Jingchuan Formation of the Ordos Basin in northwestern China. The early Barremian occurrence of the genus in Tunisia suggests that ordosestheriids have most likely originated in North Africa and then dispersed to East Asia in the Aptian to become a component of the well-known Jehol Biota. Moreover, the occurrence of fossil spinicaudatans in two horizons respectively from the Bouhedma and Sidi A？ch formations indicates the interaction of freshwater and marine conditions that characterized the northern African margin as part of widespread complex paralic environments over the Chotts and Gafsa areas during the Barremian. This research was funded by Tunisian Ministry of Scientific Research, Major Basic Research Projects of the Ministry of Science and Technology, China (973 Project), and National Natural Science Foundation of China. Related information of this paper: Li, G., Boukhalfa, K., Teng, X., Soussi, M., Ben Ali, W., Ouaja, M., Houla, Y. 2017. New Early Cretaceous clam shrimps (Spinicaudata) from uppermost Bouhedma Formation of northern Chotts range, southern Tunisia: Taxonomy, stratigraphy and palaeoenvironmental implications. Cretaceous Research 72: 124-133.
High-resolution δ13C chemostratigraphy of the Ordovician succession in the Tingskullen drill core from ？land, southeastern Sweden δ13C chemostratigraphy has been accepted as a powerful tool for correlation of carbonate successions on a regional as well as global scale. A large number of studies focusing on the Ordovician Period have been published over the last ten years in order to clarify the framework of carbon isotope chemostratigraphy. Recently, Dr. WU Rongchang from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and colleagues from Lund university (Sweden) and University of Erlangen-Nürnberg (Germany) have carried out carbon isotope analysis of the Lower through Middle Ordovician cool-water carbonates of the Tingskullen core from the island of ？land in southern Sweden, revealing one of the few and most complete records of the MDICE (Middle Darriwilian Isotope Carbon Excursion) from Baltoscandia. Based on a core section penetrating the condensed Lower–Middle Ordovician succession (46 m) on the island of ？land, southeastern Sweden, this study provides an integrated scheme for carbon isotope chemostratigraphy (313 samples) and conodont biostratigraphy (29 samples) for this period. The carbonate succession in the Tingskullen core records 12 conodont zones and 6 subzones, including the Oepikodus evae, Trapezognathus diprion, Baltoniodus triangularis, B. navis, B. norrlandicus, Lenodus antivariabilis, L. variabilis, Yangtzeplacognathus crassus, Eoplacognathus pseudoplanus (Microzarkodina hagetiana and Microzarkodina ozarkodella subzones), E. suecicus, Pygodus serra (E. foliaceus, E. reclinatus, E. robustus and E. lindstroemi subzones) and Pygodus anserinus zones in ascending order. The δ13C record reveals an apparently complete record of the MDICE, including a rising limb, a well-defined peak and a falling limb. The anomaly covers a thickness of c. 27m in the core and spans the Eoplacognathus pseudoplanus, E. suecicus, Pygodus serra and P. anserinus conodont zones. Combined with the new, detailed conodont biostratigraphy, the MDICE in the Tingskullen core can be used for detailed correlation with successions from Baltica, North America, the Argentine Precordillera, South China and North China. This study is supported by the National Natural Science Foundation of China, the Swedish Research Council and Crafoord Foundation and the Deutsche Forschungsgemeinschaft. Article information: Wu, R.C., Calner, M., Lehnert, O. 2017. Integrated conodont biostratigraphy and carbon isotope chemostratigraphy in the Lower–Middle Ordovician of southern Sweden reveals a complete record of the MDICE. Geological Magazine, 154(2): 334-353. DOI:
A seven-cell specimen of Tianzhushania Recently, Dr. YIN Zongjun from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and his international colleagues from University of Bristol and Swedish Museum of Natural History published a research paper on nuclei structures in embryo-like fossils from the 609-million-year-old Ediacaran Weng’an biota. As one of the oldest plausible claims of animals in the fossil record, the embryo-like microfossils from the Ediacaran Weng’an Biota have long been expected to afford new insights into the developmental evolution of animal body plans. Furthermore, they are among the most remarkable instances of fossilization, not merely preserving component cells, but also intracellular structures. These include small features interpreted as lipid vesicles or yolk granules and Large Intracellular Structures (LISs) whose interpretation is more controversial. The LISs have a consistent size and location, sometimes occur paired in cells, positioned parallel to an anticipated plane of cell division, and can be elongated or dumbbell-shaped, suggesting possible ongoing division. They were originally considered as nuclei, spindle bundles, or other organelles and most subsequent biological interpretations have focused on a nucleus interpretation. However, this interpretation has been controversial, perhaps because details of cytokinesis have been invoked to exclude the affinity of fossils from crown-Metazoa, but also because of a prevailing notion that nuclei cannot be fossilized in early eukaryote microfossils. Hence, in this paper, Dr. Yin and his co-authors sought to test the established taphonomic models for the LISs and to reassess their origin not only to constrain affinities of these embryo-like fossils but also to better understand the early eukaryotic fossil record. Dr. YIN and his colleagues present new data on the structure, morphology, and development of the LISs in these embryo-like fossils, based on Synchrotron Radiation X-ray Tomographic Microscopy and quantitative computed tomographic analysis. These data include specimens lacking post-decay void-filling mineralization, which allows to further test alternative taphonomic models used to interpret the origin of LISs and reassess their origin. All the lines of evidence, including consistency in the number, shape, position, and relative size (LIS-to-cytoplasm ratio) of the LISs, as well as their occurrence within preserved cytoplasm, preclude their interpretation as artefacts resulting from taphonomic or diagenetic processes and support their interpretation as cell nuclei, because nuclei are the only intracellular structure that can account for the observed regularity in number, size, position, volumetric relationships of the LISs and the evidence for division in concert with the host cell. These findings confirm that the fossils are the remains of eukaryotes and not of bacteria as previously suggested. The identification of nuclei within the Weng’an Biota, along with plausible reports from Phanerozoic deposits, indicates that nuclei can be preserved in the fossil record, contrary to general expectation. Their preservation as external molds, in some instances in association with probable nucleoli, suggests that the nucleus was less susceptible to mineral replication than the surrounding cytoplasm. The reassessment of the origin of these LISs in the Weng’an embryo-like fossils has potentially important implications for understanding Precambrian microfossils, where a record of nuclei or other organelles could enable identification of early eukaryotes and help to constrain the timing and nature of eukaryotic evolution. Reports of preserved organelles in Precambrian fossils have generally lacked sufficient support and have consequently been discounted. However, the Weng’an embryo-like fossils suggest that revisiting these reports might be profitable. Article information: Zongjun Yin, John A. Cunningham, Kelly Vargas, Stefan Bengtson, Maoyan Zhu, Philip C. J. Donoghue, 2017, Nuclei and nucleoli in embryo-like fossils from the Ediacaran Weng’an Biota, Precambrian Research, Volume 301, October 2017, Pages 145-151
Paleoenvironments (glaciation, atmospheric and oceanic oxygenation) associated with the biodiversification The Cambrian explosion of diverse bilaterian clades is considered to have proceeded in three phases preserved in the fossil record: (1) the appearance of basal metazoan phyla in Late Ediacaran time; (2) the first occurrence of biomineralization and the widespread occurrence of small shelly fossils (SSFs); (3) the emergence of the three supraphylogenetic clades during Cambrian stage 3. Though these biological events have been attributed to environmental modifications, notably oxygenation of the global ocean, specifics of the relationship between the emergence and diversification of metazoans and atmospheric-oceanic oxygenation remain unresolved. Recently, Dr. ZHANG Junpeng and Pro. ZHANG Yuandong from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, together with Pro. FAN Tailiang from China University of Geosciences (Beijing), utilized the geochemical proxy and N isotope record of the Ediacaran–Cambrian boundary preserved in intra-shelf basin, slope, and slope basin deposits of the Yangtze Sea to assess the ocean redox state during the Early Cambrian metazoan radiation. During Early Cambrian time, the water column of the shallow shelf remained oxygenated, accumulating widespread carbonate sediment as exemplified by the Xiaotan section in the eastern Yunnan province and studied sections in the Three Gorge Area. Intra-shelf basins, including the Zhongnan section, became anoxic or even euxinic, as suggested by the present and previous investigations. Further, the presence of largely negative δ15N excursions as well as elevated Mo/U and Fepy/FeHR ratios observed in the studied sections may reflect local establishment of photic zone anoxia. Clearly, δ15N profiles of the deeper water Nangao and Longbizui sections display more consistently negative values than are documented from the intra-shelf Zhongnan section suggesting that these deposits experienced a protracted period of strongly reducing conditions. In summary, the commonly ferruginous sub-photic water column of the Yangtze Sea margin experienced local anoxia or euxinia in intra-shelf basin and upper slope regions of the basin. Such diverse paleo-marine environmental conditions characterized the continental shelf of the Yangtze Sea in the face of the Cambrian explosion. They proposed that the coupling of ocean chemistry and Early Cambrian animal diversification was not a simple cause-and-effect relationship, but rather a complex interaction. Specifically, it is likely that animal diversification expanded not only temporally but also spatially from the shallow shelf to deep-water environments in tandem with progressive oxygenation of the extensive continental margin. This study was financially supported by Chinese Academy of Sciences (XDB10010100, XDPB05) and Ministry of Land and Resources of the People’s Republic of China (2009GYXQ15). Article information: Zhang, J.P., Fan, T.L., Zhang, Y.D., Lash, G.G., Li, Y.F., Wu, Y., 2017. Heterogenous oceanic redox conditions through the Ediacaran-Cambrian boundary limited the metazoan zonation. Scientific Reports 7, 8550.
Representative fossil spores and pollen grains from the Late Triassic Xujiahe Formation in Hechuan of Sichuan Basin The end-Triassic mass extinction (201.36±0.17 Ma) is one of the five largest Phanerozoic extinction events, and massive biotic crises occurred in both the marine and terrestrial realms. However, in East Asia, the Triassic-Jurassic terrestrial records are scarce compared with Europe and North America. In South China, the Upper Triassic strata of the Xujiahe Formation (latest Norian to Rhaetian) are well developed in the Sichuan Basin and contain diverse fossil plant assemblages, offering an ideal window to decipher the terrestrial ecosystem variations prior to the end-Triassic event. A research team led by Prof. WANG Yongdong at Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) has reported their recent results on the Late Triassic terrestrial ecosystem variations in the southern Sichuan Basin. Their results have been recently published online in an international geoscience journal Geological Magazine of Cambridge University Press. This study was carried out by Dr. LI Liqin, Prof. WANG Yongdong, Prof. LIU Zhaosheng from NIGPAS and Prof. Vivi Vajda from Swedish Museum of Natural History in Sweden. They reported a detailed palynological study from the Upper Triassic Xujiahe Formation in Hechuan of Chongqing, southern Sichuan Basin. The palynological analysis revealed a well-preserved terrestrial palynoflora of high diversity, comprising 184 species in 75 genera of spores and pollen. Three palynological assemblages were recognized, reflecting terrestrial successions throughout the entire interval with significant changes of the vegetation. Cycads/bennettites, ginkgophytes and conifers show an increasing trend into younger deposits, while ferns and lycopsids decrease in relative abundance. The Late Triassic vegetation underwent changes from lowland fern forest to a mixed forest with more canopy trees. Palynoflora diversity and the variations of terrestrial ecosystem and palaeoclimate in the Late Triassic Xujiahe Formation from the Hechuan region, Sichuan Basin The researchers applied the Spore-pollen Morphological Group (SMG) method and Sporomorph EcoGroup (SEG) model to interpret the palaeoclimate features. The results reveal that the lower part of the Xujiahe Formation was deposited under relatively warm and humid conditions with an overall cooling and drying trend from latest Norian to Rhaetian time, accompanied by a general decrease of ferns and simultaneous increase of gymnosperms, and a decline in diversity of miospores. The present palynological record shows a gradual ecosystem degradation extended over the Norian–Rhaetian interval. This suggests that the cooling and drying climate from latest Norian to Rhaetian time may have caused a gradual ecosystem breakdown during latest Triassic time, and later triggered the end-Triassic biotic crisis. This study presents new data from East Asia on variations within the terrestrial ecosystem prior to the end-Triassic extinction event; and also provides important information for understanding the changes in the vegetation preceding the end-Triassic event. This research was funded by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences; the National Natural Sciences Foundation of China; the State Key Program of Research and Development of Ministry of Science and Technology, China; the State Key Laboratory of Palaeobiology and Stratigraphy; and the Swedish Research Council and the Lund University Carbon Cycle Centre. This is a contribution to the IGCP project 632. Article information: Liqin Li, Yongdong Wang*, Vivi Vajda, Zhaosheng Liu, 2017. Late Triassic ecosystem variations inferred by palynological records from Hechuan, southern Sichuan Basin, China. Geological Magazine. Doi: 10.1017/S0016756817000735 (*corresponding author).
Reconstruction of Orthrozanclus elongata n. sp. in life Orthrozanclus is a shell-bearing, sclerite covered Cambrian organism of uncertain taxonomic affinity, seemingly representing an intermediate between its fellow problematica Wiwaxia and Halkieria. Attempts to group these slug-like taxa into a single ‘halwaxiid’ clade nevertheless present structural and evolutionary difficulties. Recently, Prof. ZHAO Fangchen and colleagues from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, with Dr. Smith Martin from Durham University, report a new species of Orthrozanclus from the early Cambrian Chengjiang Lagerst？tte, published in Scientific Reports. The scleritome arrangement and constitution in this material corroborates the link between Orthrozanclus and Halkieria, but not with Wiwaxia — and calls into question its purported relationship with molluscs. Instead, the tripartite construction of the halkieriid scleritome finds a more compelling parallel in the camenellan tommotiids, relatives of the brachiopods and phoronids. Such a phylogenetic position would indicate the presence of a scleritome in the common ancestor of the three major trochozoan lineages, Mollusca, Annelida and Brachiozoa. On this view, the absence of fossil Ediacaran sclerites is evidence against any ‘Precambrian prelude’ to the explosive diversification of these phyla in the Cambrian, 540–530 million years ago. Orthrozanclus elongate from the Cambrian Chengjiang Biota This research was supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences and the National Natural Science Foundation of China. Related information: Zhao, F.C., Smith, M.R., Yin, Z.J., Zeng, H., Li, G.X., Zhu, M.Y., 2017. Orthrozanclus elongata n. sp. and the significance of sclerite-covered taxa for early trochozoan evolution. Scientific reports, doi:10.1038/s41598-017-16304-6 News stories: https://www.altmetric.com/details/29369309/news
Researchers report exceptionally well-preserved fossil tree trunks approximately 374 million years old from Xinjiang, Northwest China. These fossils suggest that earth’s earliest forest trees were able to achieve great size by a unique method that involved building a hollow cylindrical skeleton of interconnected, growing, woody strands that both tore itself apart and collapsed under its own weight in a controlled manner as the tree’s diameter expanded. The evolution of trees and forests in the Middle to Late Devonian Period, 393–359 million years ago, profoundly transformed the terrestrial environment and atmosphere. The oldest fossil trees belong to the class Cladoxylopsida. In general, their water-conducting system was a ring of hundreds of individual strands of xylem (water-conducting cells) that were interconnected in many places. However, how these structures grew and how the trees became tall enough to make a forest are still unclear. Researchers from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS), Cardiff University (UK) and the State University of New York at Binghamton (USA) report exceptionally well-preserved fossil tree trunks approximately 374 million years old from Xinjiang, Northwest China. These fossils suggest that earth’s earliest forest trees were able to achieve great size by a unique method that involved building a hollow cylindrical skeleton of interconnected, growing, woody strands that both tore itself apart and collapsed under its own weight in a controlled manner as the tree’s diameter expanded. The finding was published in Proceedings of the National Academy of Sciences (PNAS) on Oct. 23. Cladoxylopsida included the earliest large trees that formed critical components of globally transformative pioneering forest ecosystems in the Middle and early Late Devonian (ca. 393–372 Ma). Well-known cladoxylopsid fossils include the up to ～1-m-diameter sandstone casts known from Middle Devonian strata in New York State. The cladoxylopsid trunk structure comprised a more or less distinct cylinder of numerous separate cauline xylem strands connected internally with a network of medullary xylem strands and, near the base, externally with downward-growing roots, all embedded within parenchyma. However, the means by which this complex vascular system was able to grow to a large diameter is unknown. In this research, a team of scientists led by Dr. XU Honghe from NIGPAS carried out a theoretical study on how earliest trees grow, based on exceptional, up to ～70-cm diameter silicified fossil trunks with extensive preservation of cellular anatomy from the early Late Devonian (Frasnian, ca. 374 Ma) in Tacheng, Xinjiang in northwest China. Xinjiang trunk expansion is associated with a cylindrical zone of diffuse secondary growth within ground and cortical parenchyma and with production of a large amount of wood containing rays and growth increments produced by normal cambria, both surrounding individual xylem strands. The xylem system accommodates expansion by tearing individual strand interconnections during secondary development. This mode of growth seems capable of producing trees of large size. Understanding the structure and growth of cladoxylopsids informs the analysis of canopy competition within early forests with the potential to drive global processes. The study has been published online: Xu H-H, Berry CM, Stein W, Wang Y, Tang P, Fu Q. 2017. Unique growth strategy in the Earth’s first trees revealed in silicified fossil trunks from China. PNAS. The largest silicified trunk in the field, with a maximum diameter of ～70 cm, from the Upper Devonian of Xinjiang, Northwest China. Image by XU Honghe. The transverse plane of a trunk from the Upper Devonian of Xinjiang. Note at least 33 cauline xylem strands forming a double cylinder, with some in the process of dividing. Letters indicate the different slices; numbers indicate the cauline strands. Image by XU Honghe.
A research group report their latest study on the astronomical cycles and magnetostratigraphy of the Late Triassic Xujiahe Formation of South China. Their study provides key evidence for resolving the decade-long controversy on the Late Triassic time scale; it also has significant implications on the global correlation of the end-Triassic mass extinction event and global climate and environmental changes. The Triassic Period (252-201 million years ago) is bounded by two mass extinctions, but the time scale of the Late Triassic still remains controversial. A new study published in Earth and Planetary Science Letters, a top journal of geoscience sheds light on this critical problem. A research group led by Prof. HUANG Chunju at China University of Geosciences (Wuhan) and Prof. WANG Yongdong at Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences report their latest study on the astronomical cycles and magnetostratigraphy of the Late Triassic Xujiahe Formation of South China. Their study provides key evidence for resolving the decade-long controversy on the Late Triassic time scale; it also has significant implications on the global correlation of the end-Triassic mass extinction event and global climate and environmental changes. The Milankovitch theory that quasi-periodic oscillations in the Earth-Sun position have induced prominent 10 to 100 thousand year variations in the stratigraphic record of climate is widely accepted. Reversals of the Earth’s magnetic polarity field are geologically rapid events. These provide the cornerstone for the high-resolution geochronology. The astronomically tuned geomagnetic polarity time scale of the Newark Supergroup of North America provides a "global reference" for the Late Triassic time scale. However, the Newark reference scale has been challenged regarding its age scale and completeness. Therefore, an independent astronomical-tuned magnetic polarity zonation is required to verify the Newark reference scale. Sichuan Basin is a large and typical Mesozoic terrestrial basin in eastern Asia. The dinosaur-track-bearing Xujiahe Formation has abundant and diverse fossils plants and fauna; it is one of the key resource beds for coal and gas. The Xujiahe Formation deposited in the lacustrine-fluvial environment ca. 200 million years ago. The chronology of the formation is quite uncertain that hampers global correlation with Upper Triassic marine sections. In past years, the research team conducted an integrated study on the biodiversity and environmental change across the Triassic-Jurassic transition in the Sichuan Basin. Collaborated with international geologists, the team did a five-year long integrate study of astronomical cycles and magnetic stratigraphy from four sections in Xuanhan, Hechuan and Guangyuan regions of the Sichuan Basin from 2012 to 2016. Variations in natural gamma-ray and magnetic susceptibility that reflect variable continental weathering in the source regions of the Xujiahe Formation are paced by Milankovitch cycles, especially the 100-kyr short eccentricity and 405-kyr long eccentricity. They compiled a multiple million years astronomical calibrated magnetic stratigraphy for the Xujiahe Formation that also has dating from detrital zircons and regional biostratigraphy. The age of the Xujiahe Formation was accordingly assigned to the late Norian to the Triassic-Jurassic boundary 201.3 to 207.2 million years ago. For the first time, the cycle-calibrated magnetostratigraphy of the Xujiahe Formation is compared directly via the magnetic-polarity zones to the astronomical cycles of the Newark Supergroup. The Sichuan-Newark time scale is compatible with the magnetostratigraphy from the candidate Global Boundary Stratotype Section and Point (called 'Golden Spike' in the geological community) for the Norian-Rhaetian boundary interval in Italy. A cooling event recovered from the oxygen isotope at the Italian Golden Spike is consistent with a similar event indicated from the fossil wood Xenoxylon at the Xujiahe Formation. Furthermore, age of the earliest dinosaur footprints in China is also dated to the middle Rhaetian (ca. 204 Ma). This study greatly improves the chronologic resolution of the Xujiahe Formation. It also helps to resolve the controversy about the completeness and reliability of the Newark reference scale. This is the first solid evidence from China that provides critical constraint for the Late Triassic Time Scale. An international reviewer said this paper is “extremely concise and to the point, and presents interesting data that will be of use to the ongoing debate on the duration and subdivisions of the Late Triassic”. This study was co-sponsored by the National Natural Sciences Foundation of China, Strategic Priority Research Program (B) of the Chinese Academy of Sciences, 973 program, 111 Project, China Scholarship Council, and Overseas Distinguished Teacher Program of the Ministry of Education. Prof. Chunju Huang and Yongdong Wang are two corresponding authors of the study. Read more at: Li, Mingsong, Zhang, Yang, Huang, Chunju*, Ogg, James, Hinnov, Linda, Wang, Yongdong*, Zou, Zhuoyan, Li, Liqin. 2017. Astronomical tuning and magnetostratigraphy of the Upper Triassic Xujiahe Formation of South China and Newark Supergroup of North America: implications for the Late Triassic time scale. Earth and Planetary Science Letters, 475: 207-223. http://dx.doi.org/10.1016/j.epsl.2017.07.015
Prof. WANG Yongdong Nanjing Institute of Geology and Palaeontology E-mail: ydwang@nigpas.ac.cn
There is a drowning event in the Yangtze Platform that happened during Floian to Dapingian age, which refers to curtailment or shut down of shallow water carbonate platform and reef production, and has resulted in the changes of depositional regime. What makes this event more important is the coincidence with Great Ordovician Biodiversification Event (GOBE). The GOBE is a rapid radiation of marine biodiversity in Ordovician Period, especially during the Early to Middle Ordovician. Conducting case studies in South China for more than ten years, Chinese researchers have already achieved quite a few detailed results in this process. But researches about its mechanism and environmental background are still insufficient. Thus, a detailed study on the process of this drowning event is necessary. Field photos. (A) and (B) are Microbialite and lithoclastic grainstone of the Hunghuayuan Formation respectively, which is the deposits before drowning; (C) is the boundary (white line) between the Hunghuayuan Formation and the overlying Zitai Formation; (D), (E) and (F) show the characters of the Zitai's deposits after drowning. Coins in A, B, D and E are 2 cm in diameter, while hammer in C and pen in F are 28 cm and 14 cm in length respectively. Recently, Ph.D. candidate LUAN Xiaocong, Prof. ZHAN Renbin and other researchers form Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, in collaboration with sedimentologists and paleontologists from Peking University and University of Cincinnati, USA, have been carrying out the sedimentological study on the Lower-Middle Ordovician succession at Xiangshuidong, southwestern Hubei Province. Their investigation shows that the drowning event appear as the replacement of pure grey grainstones and packstones of the Hunghuayuan Formation by purple red, argillaceous limestone of the Zitai Formation and correlative units, which are mixed siliciclastic and carbonate deposits. The drowning was gradual and fluctuating, starting as a marginal shoal, through the inner ramp, and becoming a stable ramp setting. This drowning is mainly attributed to a global sea-level rise, and an increase of terrigenous supply that resulted from local tectonic movement (i.e. the initiation of collision between the South China and Cathaysia blocks). After drowning, red offshore marine facies were well developed along the platform margin, indicating an oxic sea bottom environment during the first acme of GOBE in South China. The changes in environments associated with this transition may have provided new evolutionary opportunities that contributed to the Middle Ordovician diversification. It is a key for us to further understand the detailed process of GOBE in South China.
Component vertical successions, microfacies distribution and sea-level change of the Hunghuayuan (HHYF) and the Zitai (ZTF) formations at Xiangshuidong section. Abbreviations: FHF, Fenhsiang Formation; KNTF, Kuniutan Formation; T., thickness; M, mudstone; W, wackestone; P, packstone; G, grainstone; R, reef; clr., color; SW, storm wave base; FW, fair weather wave base; HST, Highstand Systems Tract; TST, Transgressive Systems Tract; CS, Condensed section. Related information of this paper: Luan Xiaocong, Carlton E. Brett, Zhan Renbin, Liu Jianbo, Wu Rongchang, Liang Yan. 2017. Microfacies analysis of the Lower-Middle Ordovician succession at Xiangshuidong, southwestern Hubei Province, and the drowning and shelf-ramp transition of a carbonate platform in the Yangtze region. Palaeogeography, Palaeoclimatology, Palaeoecology. https://doi.org/10.1016/j.palaeo.2017.06.004
CA analysis of conodont faunas using the Jaccard and Raup-Crick similarity coefficients: A, B – ‘Pre-Telychian’ interval, C, D – Telychian interval The Llandovery of the Silurian is an important period for the evolution of conodonts. After the end Ordovician mass extinction, conodont animal started to recover and then radiate in the Llandovery, with significant changes in the fauna and the diversity. The study on the paleobiogeographic pattern of the conodont animal, will help us understand the distribution pattern of conodont animal during the transitional period and its relationships with the paleo-environmental changes. Recently, Dr. CHEN Zhongyang and Prof. FAN Junxuan from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, together with Dr. Peep M？nnik from Institute of Geology, Tallinn University of Technology, Estonia, reconstructed the Llandovery conodont provincialism based on the revised conodont occurrences from 250 localities around the world. Several quantitative methods were adopted in their analyses. The result indicates a surprising, longitudinal distribution pattern, which was mostly controlled by the ocean current circulation, rather than temperature. Moreover, they investigated the paleobiogeographic pattern of conodont animal since Early Ordovician. They found that the conodont animal showed apparent longitudinal distribution pattern during the whole Ordovician, while a sudden change happened during the Ordovician-Silurian transition. They inferred that the Hirnantian glaciation and the simultaneous mass extinction could be the major controlling factor which resulted in the reorganization of the conodont fauna and the significant change in its living habits and ecological requirement. However, additional studies and a more comprehensive data set are needed to reveal the mechanism of these changes. The study was supported by the National Natural Science Foundation of China, Chinese Academy of Sciences and the Estonian Research Council. Article information: Zhongyang Chen, Peep M？nnik, Junxuan Fan*. 2017. Llandovery (Silurian) conodont provincialism: An update based on quantitative analysis. Palaeogeography, Palaeoclimatology, Palaeoecology. https://doi.org/10.1016/j.palaeo.2017.07.023.
