Ages, Trace Elements and Hf-Isotopic Compositions of Zircons from Claystones around the Permian-Triassic Boundary in the Zunyi Section, South China: Implications for Nature and Tectonic Setting of the Volcanism

A growing body of evidence shows that volcanism near the Permian-Triassic boundary（PTB） may be crucial in triggering the Permian–Triassic（P–Tr） mass extinction. Thus, the ash beds near the PTB in South China may carry information on this event. Three volcanic ash layers, altered to clay, outcropped in the PTB beds in Zunyi Section, Guizhou Province, Southwest China. The U-Pb ages, trace elements, and Hf-isotope compositions of zircon grains from these three ash beds were analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons are mainly magmatic in origin（241-279 Ma） except for two inherited/xenocrystic zircons（939 and 2 325 Ma）. The ages of these magmatic zircons indicate three episodes of magmatism which occurred around the MiddleLate Permian boundary（-261.5 Ma, MLPB）, the Wuchiapingian-Changhsingian boundary（-254.5 Ma, WCB）, and the PTB（-250.5 Ma）, respectively. The first two episodes of magmatism near the MLPB and WCB may be attributed to magmatic inheritance or re-deposition. All magmatic zircons share similar trace-element and Hf-isotope compositions. They have Y, Hf, Th and U contents and Nb/Ta ratios are typical of zircons from silicic calc-alkaline magmas. These zircons also exhibit enriched Hf-isotope compositions with _（εHf）（t） values of-11.4 to ＋0.2, which suggests that the three magmatic episodes involved melting of the continental crust. The more enriched Hf-isotope composition （_（εHf）（t）=-11.4--4.8） of Bed ZY13（-250.5 Ma） implies more input of ancient crustal material in the magma. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggest that these three episodes of magmatism may take place along the convergent continent margin in or near southwestern South China as a result of the closure of the Palaeo-Tethys Ocean.

Microconchids from Microbialites near the Permian-Triassic Boundary in the Zuodeng Section, Baise Area, Guangxi Zhuang Autonomous Region, South China and Their Paleoenvironmental Implications

Abundant microconchid worm tubes were extracted from the microbialites deposit near the Permian-Triassic boundary at the Zuodeng Section, Baise area, Guangxi Zhuang Autonomous Re- gion, South China. These calcareous worm tubes were studied in both petrographic thin sections and isolated specimens using optical microscope and sensitive electronic microscope （SEM）, respectively. They are categorized into two morphological types： helically coiled and planispirally coiled tubes, which are assignable to Microconchus aberrans （Hohenstein, 1913） and M. utahesis （Zatofi et al., 2013）, respectively. The tube wall ultrastructnre is characterized by laminated micrites, which distinguish the studied microconchids from comparable microgastropods or spirorbid polychaete that usually has shell nltrastructnre of spar texture. The overwhelm majority of microconchids from the microbialite possess the planispirally coiled tubes. The lifestyle of extant, morphologically convergent spirorbids suggests that these planispirally coiled microconchids may have colonized in some local oxygenic oases probably produced by photosynthetic cyanobacteria in the oxygen-poor microbialite ecosystem in which they may have settled densely with high competition among various individuals and with other associated animals for oxygen consumption and food soucres. The deleterious environment condition of the mi- crobialite ecosystem immediately after the Permian-Triassic biocrisis is also indicated by various geochemical signals derived from the same section. Such a deleterious habitat may be inhospitable for most metazoans, but it has some local oxygenic oases that was favorable for opportunistic taxa to dwell.

Orbital Forcing and Sea-Level Changes in the Earliest Triassic of the Meishan Section,South China

The Earliest Triassic Yinkeng Formation is exposed at the well-known Meishan Section, South China, which contains the Global Stratotype of Section and Point （GSSP） for the Permian- Triassic boundary （PTB）. It records centimeter-scale rhythmic alternations comprised mainly by marl- stone and limestone. Seven types of couplet embedded in five types of bundles were recognized based on occurrence and thickness of the lithologic units, suggesting that their formation was controlled by cyclic processes. The various orders of cycles observed correlate well with other Early Triassic counterparts recorded in South China. Here, we present new cyclostratigraphic results based on lithologic thickness and relative carbonate content of the Yinkeng Formation. Power spectra of carbonate content show that the ratio of major wavelengths recognized throughout the formation is similar to that of the 100 kyr short eccentricity, 33 kyr obliquity, and 21 kyr precession cycles, indicating that astronomical sig- nals are recorded in the Earliest Triassic rhythmic succession. Consistence between pronounced lithologic rhythmicity and sea-level changes obtained from Fischer plots indicates that high-frequency climatic cycles may have driven sea-level changes immediately after the PTB mass extinction. Fur- thermore, the 4th-order sea-level changes interpreted from the sedimentary record match well with 100 kyr short eccentricity component of carbonate content, reflecting that the 100 kyr short eccentricity- induced climate changes may have likely controlled the deposition of 4th-order sequences recognized from rhythmic successions.

Palaeoecological Analysis of Trace Fossil Sinusichnus sinuosus from the Middle Triassic Guanling Formationin Southwestern China

The Luoping Biota discovered from the early Middle Triassic （Anisian） Guanling Formation of southwestern China represents a fully recovered shallow marine ecosystem, marking the end point of Early Triassic biotic recovery following the end-Permian mass extinction. Contemporaneously preserved are prolific trace fossils, which offer good opportunities to understand the palaeoecology of marine invertebrates from a fully recovered shallow marine ecosystem. Here we present a newly discovered sinuous branching burrow from the fossil-bearing unit in Member II of the Guanling Formation. Several features, including the horizontal regular sinuous nature, the branching pattern, typical H-junction, and the small wavelength/amplitude ratio of these sinuous structures within the burrow systems justify assignment of these traces as Sinusichnus sinuosus, a trace possibly produced by decapod crustaceans. Close association ofS. sinuosus with Rhizocorallium commune suggests a deposit-feeding strategy of these trace makers. The newly reported Anisian material from the Guanling Formation in Luoping represents first report of Sinusichnus from South China. The global record of Sinusichnus occurrence suggests that these burrows might have an older history than Early Middle Triassic.

A Taxonomic Re-Assessment of the Novispathodus waageni Group and Its Role in Defining the Base of the Olenekian (Lower Triassic)

Lower Triassic conodont biostratigraphy has been well studied around the world in the past decades, but the Induan-Olenekian boundary （IOB） remains undecided. The Novispathodus waageni group has been taxonomically re-assessed based on abundant new materials from the Jianshi and Chaohu sections, South China. New study shows that Nv. waageni typically possesses： （1） an approximately equi-dimentional P1 blade element, （2） an accurate upper profile with denticle height descending in both directions, （3） a denticulated posterior edge （lower denticles posterior of the highest denticle）, and （4） a round basal cavity outline. Of the three proposed subspecies of the waageni species, both Nv. waageni waageni （Sweet, 1970） and Nv. w. eowaageni （Zhao and Orchard, 2005） are valid, and the former differs clearly from Nv. w. eowaageni in having （1） a slightly higher length/height ratio （holotype=1.30 ： 1.23）, （2） a thicker blade, sometimes with medial thickening, （3） fewer （broader） denticles per unit length, （4） generally recurved denticles, not straight and upright, （5） highest denticles closer to posterior, （6） common differentiation of a posterior cusp, and （7） more sinuous basal profile, with increased posterior upturning. A third subspecies illustrated as Nv. waageni n. subsp. A sensu Goudemand, 2014 is not conspecific with older individuals of Nv. w. eowaageni, and also cannot be as- signed to the Nv. waageni group. Abundant new materials demonstrate a clear ontogenic process for Nv. w. eowaageni, indicating that Nv. w. eowaageni occurring in the Induan-Olenekian boundary （IOB） succession is rather stable. Small, earlier individuals （i.e., those from Bed 225 in Jianshi） are referred to as Nv. w. eowaageni Morphotype A, and are thought to have likely evolved from Ns. dieneri Morphotype 3, and to be the precursor of mature elements ofNv. w. eowaageni. The first appearance datum of Nv. w. eowaageni therefore is an ideal mark defining the IOB.

Efficacy and safety of antifibrinolytic agents in spinal surgery: a network meta-analysis

Background: Significant blood loss is still one of the most frequent complications in spinal surgery, which often necessitates blood transfusion. Massive perioperative blood loss and blood transfusion can create additional risks. Aprotinin, tranexamic acid (TXA), and epsilon-aminocaproic acid (EACA) are antifibrinolytics currently offered as prophylactic agents to reduce surgery-ass oci a ted blood loss. The aim of this study was to evaluate the efficacy and safety of aprotinin, EACA, and low/high doses of TXA in spinal surgery, and assess the use of which agent is the most optimal intervention using the network meta-analysis (NMA) method. Methods: Five electronic databases were searched, including PubMed, Cochrane Library, ScienceDirect, Embase, and Web of Science, from the inception to March 1,2018. Trials that were randomized and compared results between TXA, EACA, and placebo were identified. The NMA was conducted with software R 3.3.2 and STATA 14.0. Results: Thirty randomized controlled trial (RCT) studies were analyzed. Aprotinin (standardized mean difference [SMD]=-0.65, 95% credibility intervals [CrI;-1.25,-0.06]), low-dose TXA (SMD=-0.58, 95% CrI [-0.92,-0.25]), and high-dose TXA (SMD =-0.70, 95% CrI [-1.04,-0.36]) were more effective than the respective placebos in reducing intraoperative blood loss. Low-dose TXA (SMD=-1.90, 95% CrI [-3.32,-0.48]) and high-dose TXA (SMD =-2.31, 95% CrI [-3.75,-0.87]) had less postoperative blood loss. Low-dose TXA (SMD=-1.07, 95% CrI [-1.82,-0.31]) and high-dose TXA (SMD =-1.07, 95% CrI[-1.82,-0.31]) significantly reduced total blood loss. However, only high-dose TXA (SMD =-2.07, 95% CrI [-3.26,-0.87]) was more effective in reducing the amount of transfusion, and was significantly superior to low-dose TXA in this regard (SMD =-1.67, 95% CrI [-3.20,-0.13]). Furthermore, aprotinin (odds ratio [OR]= 0.16, 95% CrI [0.05, 0.54]), EACA (OR = 0.46, 95% CrI [0.22, 0.97]) and high dose of TXA (OR = 0.34, 95% CrI [0.19, 0.58]) had a significant reduction in transfusion rates. Antifibrinolytics did not show a significantly increased risk of postoperative thrombosis. Results of ranking probabilities indicated that high-dose TXA had the greatest efficacy and a relatively high safety level. Conclusions: The antifibrinolytic agents are able to reduce perioperative blood loss and transfusion requirement during spine surgery. And the high-dose TXA administration might be used as the optimal treatment to reduce blood loss and transfusion.

Exceptionally Preserved Caddisfly Larval Cases(Insecta) from the Lower Cretaceous of the Liupanshan Basin, Western China

Abundant well-preserved tubular fossils of caddisfly （Insecta： Trichoptera） larval cases are reported from the Early Cretaceous Madongshan and Naijiahe formations of the Liupanshan Basin, Ningxia Province, western China. Most cases were mainly preserved in life position and densely packed in various layers. Individual cases in each layer tended to be same in size and were erect and parallel to one another and open at both ends. In a transverse section cut perpendicular to the long axis of the cases, individual case appears to form a rounded ring. Small cases are elliptic in a cross-section oblique to the long axis of the cases. Tube walls are nearly subparallel to one another in longitudinal section with both ends being open. The caudal end of the case slightly tapers and usually points downward. The cases were closely packed, almost touching with one another and lacking bifurcate or connecting struc- ture. The overwhelming majority of cases were partially or fully filled with calcite. The case wall em- braces a medium particle layer flanked by inner and outer organic layers. Individual particles are ovate in outline and comprise cryptocrystalline or ganic pellets. SEM imaging shows that those pellets are sub-cylindrical in outline and elliptic in cross section, and are made primarily of calcium carbonate. All features observed justify the assignment of the Liupanshan caddisfly cases to ichnogenus Coprindusia. The extinct insect Ningxiapsyche fangi was found in association with the Liupanshan caddisfly larval cases, and thus could be the candidate of the potential trace-maker.

Permian Radiolarians from the A'nyemaqen Mélange Zone in the Huashixia Area of Madoi County,Qinghai Province,Western China,and Their Implications on Regional Tectonism

The Huashixia area in the Madoi County, Qinghai Province, western China is one of the most important areas for the studies of the formation and evolution of the A＇nyemaqen mélange zone due to the well exposed, relatively complete tectonostratigraphic successions. However, the timing and evolutionary process of the A＇nyemaqen paleo-ocean has long been poorly understood. Recently, we obtained abundant radiolarians from the siliceous rocks of the Maerzheng Formation of this mélange zone in Huashixia. Total 19 species in 10 radiolarian genera have been identified. They belong mainly to the Albaillellaria, Spumellaria, Entactinaria, and Latentifistularia. Four radiolarian assemblage zones are established, including： the Pseudoalbaillella rhombothoracata, Pseudoalbaillella scalprata, Ruzhencevispongus uralicus, and Follicucullus bipartitus-Follicucullus sp. cf. F. ventricosus zones. Radiolarian faunal correlations suggest a late Artinskian-early Kungurian age and late Capitanian-early Wuchiapingian age for the first two zones from the lower part and the last two zones from the upper parts of the Maerzheng Formation, respectively. All radiolarians are typical of deep water elements living in deep oceans in low latitudes during the Permian. Previously, the radiolarians of Early Carboniferous to Early Permian age and fusulinids of Early-Middle Permian age have also been reported from the A＇nyemaqen mélange successions. The combination of the newly found radiolarians with the previously reported faunal and microfloral assemblages as well as radiometric ages obtained from the same stratigraphic units indicates that the A＇nyemaqen paleo-ocean may have opened initially during the Early Carboniferous, expanded from the Early-Middle Permian, reached its acme in the early Late Permian, shrunk during the latest Permian to Early Triassic, and eventually was closed in the Middle Triassic.

Great Paleozoic-Mesozoic Biotic Turnings and Paleontological Education in China: A Tribute to the Achievements of Professor Zunyi Yang

Professor Zunyi Yang is a pioneer paleontologist who established the earliest Paleontological education and research in China, and has contributed his lifetime to promotion of Chinese paleontological education and researches as well as the studies on the Permian-Triassic （P-Tr） mass extinction and its possible causes. Yang has studied six fossil clades and trace fossils, together with his colleagues, he has established 6 new species of cephalopods, 1 new genus and 15 new species of gastropods, 8 new genera and 31 new species of bivalves, 17 new genera and 66 new species of brachiopods, 1 new genus and 4 new species of ophiuroids, 2 new genera and 7 new species of triopsids （Crustacea）, and 3 new ichnogenera and 7 new ichnospeeies of trace fossils. Yang led the 2nd IGCP working on the P-Tr mass extinction in the world. His group＇s excellent works on basic stratigraphy and paleontology enable the GSSP of P-~r boundary （PTB） to be ratified in China. Yang＇s earlier works on three-episode extinction pattern and volcanism-causing extinction hypothesis are also highlighted here to show how their first-hand data and initiative hypothesis have influenced the current and ongoing debates on the P-Tr crisis and possible causation. Yang school＇s extinction pattern is reviewed here, and their 2nd phase of extinction is marked by a dramatic loss in biodiversity, pointing to a widely accepted mass extinction. The 3rd extinction is characterized by ecological collapse of ecosystem structures and disappearance of the PTB microbialite ecosystem, while the 1st extinction （also prelude extinction） is indicated by the collapses of deep-water and reef ecosystems. Updated studies show that the volcanic ashes near the PTB originated from silicic, subduction-related igneous activity with little or no basaltic input. This subduction zone activity is related to closure of the Paleo-Tethys Ocean, and the intensity and frequency of the volcanic activity appear to increase near the P-Tr extinction interval. Hg anomalies （Hg/TOC ratios and Hg isotopes） were also detected from the P-Tr extinction interval, and they are interpreted as the results of enhanced volcanic-generated atmospheric mercury, which was injected by the violate eruption of the Siberian traps. Thus, the peak felsic volcanism is coeval with violate eruption of Siberian traps, and the coupled relationship between both types of volcanisms and biotic extinction suggests a causal relationship.

A New Machine-Learning Extracting Approach to Construct a Knowledge Base: A Case Study on Global Stromatolites over Geological Time

Within any scientific disciplines, a large amount of data are buried within various literature depositories and archives, making it difficult to manually extract useful information from the datum swamps. The machine-learning extraction of data therefore is necessary for the big-data-based studies. Here, we develop a new text-mining technique to reconstruct the global database of the Precambrian to Recent stromatolites, providing better understanding of secular changes of stromatolites though geological time. The step-by-step data extraction process is described as below. First, the PDF documents of stromatolite-containing literatures were collected, and converted into text formation. Second, a glossary and tag-labeling system using NLP(Natural Language Processing) software was employed to search for all possible candidate pairs from each sentence within the papers collected here. Third, each candidate pair and features were represented as a factor graph model using a series of heuristic procedures to score the weights of each pair feature. Occurrence data of stromatolites versus stratigraphical units(abbreviated as Strata), facies types, locations, and age worldwide were extracted from literatures, respectively, and their extraction accuracies are 92%/464, 87%/778, 92%/846, and 93%/405 from 3 750 scientific abstracts, respectively, and are 90%/1 734, 86%/2 869, 90%/2 055 and 91%/857 from 11 932 papers, respectively. A total of 10 072 unique datum items were identified. The newly obtained stromatolite dataset demonstrates that their stratigraphical occurrences reached a pronounced peak during the Proterozoic(2 500 – 541 Ma), followed by a distinct fall during the Early Phanerozoic, and overall fluctuations through the Phanerozoic(541–0 Ma). Globally, seven stromatolite hotspots were identified from the new dataset, including western United States, eastern United States, western Europe, India, South Africa, northern China, and southern China. The proportional occurrences of inland aquatic stromatolites remain rather low(~20%) in comparison to marine stromatolites from the Precambrian to Jurassic, and then display a significant increase(30%–70%) from the Cretaceous to the present.