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The Borkewehr section near Balve at the southeastern end of the Remscheid-Altena Anticline is currently the best and most complete Devonian/Carboniferous Boundary (DCB) succession of the Rhenish Massif, Germany. Based on a multidisciplinary approach, focusing on refined conodont and ammonoid biostratigraphy, microfacies analyses, sequence stratigraphy, carbon isotopes (Corg and Ccarb), trace element geochemistry, including REE data, and cyclostratigraphy, the section is proposed as a candidate for the new basal Carboniferous GSSP. The succession represents a pelagic “seamount” setting. It spans the upper Famennian to lower Viséan, with a condensed development of most Rhenish lithostratigraphic units and sedimentary sequences. It is the type-section of the oxic and strongly cyclic, fossiliferous Wocklum Limestone and of important uppermost Famennian and basal Carboniferous index species. The First Appearance Datum (FAD) of Protognathodus kockeli s.str., in a phylogenetic succession from the ancestral Pr. semikockeli n. sp., is proposed as future GSSP level. This FAD is sandwiched between many other marker levels for global correlation. Below are, from base to top, the transgressive base of the at least partly anoxic Hangenberg Black Shale (base Lower Hangenberg Crisis Interval), the Hangenberg Regression (onset of siltstones of the basal Middle Crisis Interval), the level of maximum regression, indicated by maximum Zr/Al values, and the initial transgression of the basal Upper Crisis Interval, marked by the re-onset of carbonate deposition. Above follow the locally cryptogenic FAD of Siphonodella (Eosiphonodella) sulcata s.l. at the base of the post-Crisis Interval (Hangenberg Limestone), associated with a conodont biofacies shift, the FAD of Si. (Eo.) bransoni, and, much higher, the sharp Lower Alum Shale Event at the base of the classical middle Tournaisian. The significance of the section is greatly enlarged by its precise correlation with numerous other Rhenish DCB sections that provide important additional data on faunas, geochemistry, geochronological ages, and magnetic susceptibility. The new Borkewehr data suggest changes of weathering intensity, based on Rb/K and K/Al trends, and Milankovitch cyclicity associated with the climate changes of the Hangenberg Crisis. The local conodont extinction rate at the top of the Wocklum Limestone lies at 57 % while there are no survivors in ammonoids, trilobites, or deep-water corals. Positive carbon isotopic shifts of carbonate in the Upper Crisis Interval and of Corg in the Middle Crisis Interval are decoupled, which suggests complex underlying processes that are not yet understood.

The lower/upper Emsian boundary witnessed prominent diversification of biostratigraphically important genera Polygnathus Hinde, Caudicriodus Bultynck, and Latericriodus Muller. In contrast, conodonts previously reported around this boundary from the South China Block were characterized by relatively low species or subspecies diversity, and only a few widely distributed and extensively studied zone-defining taxa were recorded. In this paper, conodonts from the Daliantang Formation at the Daliantang section (Guangnan, southeastern Yunnan), one of the representative sections of the transitional facies between the benthic Xiangzhou facies and the pelagic Nandan facies, are investigated. The conodont fauna shows a remarkably high species or subspecies diversity, with fourteen taxa that are assignable to the notoperbonus Zone and inversus Zone. Five polygnathid species are described: P. gronbergi Klapper and Jonson, P. inversus Klapper and Jonson, Polygnathus sp. B, P. luciae Martinez-Perez and Valenzuela-Rios, and P. mashkovae Bardashev. The latter two are reported for the first time from the South China Block. Additionally, three icriodontid taxa are also described, of which L. guangnanensis n. sp. is characterized by distinctly chevron-shaped transverse rows in the anterior part and a well-developed process branching off to the outer side. The new conodont record increases our understanding of the diversification and faunal composition around the lower/upper Emsian boundary in the South China Block. It contributes to the regional and inter-regional biostratigraphical correlation between shallower- and deeper-water facies and also furnishes important South China material for future discussion and deliberation on the position of the lower/upper Emsian boundary.

The Devonian-Carboniferous transition is marked by major perturbations to the Earth’s climate system and marine redox conditions, a first-order mass extinction, and the succeeding marine ecosystem recovery, recording a sequence of environmental and biotic events. In South China, there exist numerous well-preserved and continuous Devonian-Carboniferous boundary successions that were formed in low-latitude passive margin basin, and this presents a unique opportunity to decipher the strata along a proximal to basinal transect using integrated biostratigraphical, event-stratigraphical, and geochemical approaches. Our geochemical data (δ13Ccarb, δ15Nbulk, δ238U and Mo/U enrichments, I/Ca ratio) indicated local and global C-N cycling perturbations and marine anoxia in the main phase of the Hangenberg Crisis interval (Middle Siphonodella praesulcata Zone), which coincided with a major regression in South China. Stromatoporoid biostromes and most typical Devonian faunas did not survive into the interval, and the deep-water black shales yield only opportunistic survivors, such as ammonoid Postclymenia cf. evoluta and bivalve Guerichina, along with miospores belonging to the LN Zone. The upper Hangenberg Crisis interval (Upper Si. praesulcata Zone, equal to the Protognathodus kockeli Zone) is marked by initial post-glacial transgression, a global δ13Ccarb spike, and opportunistic faunal blooms, coincident with conodont biofacies shift to the polygnathid-protognathodid biofacies. The Protognathodus fauna, nearly absent from platform facies, is often found in the condensed upper crisis interval of the basin, slope, and platform margin facies within the Youjiang Basin, although the abundance is extremely low and the phylogenetic lineage of Pr. meischneri-Pr. collinsoni-Pr. kockeli cannot be recognised in most successions. In South China, the first occurrence of Pr. kockeli seems to correspond to lithofacies changes, recorded in the first level of transgression just above the Hangenberg Sandstone event. Multiple lines of evidence, including great spatial heterogeneity of δ13Ccarb and δ15Nbulk records, extremes of redox proxies, and lack of macrofossils, suggest that marine habitats remained in a critical/turbulent state during the Upper Si. praesulcata Zone, triggering the opportunistic blooms and minor extinctions. Following the crisis intervals, radiation/recovery of many fossil groups did not occur until the upper part of the Siphonodella sulcata Zone to the Si. duplicata Zone. In particular, a negative shift of δ13Ccarb to pre-crisis values occurring near the base of the Si. sulcata/Pr. kuehni Zone could be recognised worldwide. The research history, current status, and achievement of Devonian-Carboniferous boundary in China are briefly reviewed.

Lime mud (i.e., micrite) is a major component of carbonate deposits. Various mechanisms (biotic versus abiotic) have been proposed for the formation of lime mud in Earth’s history. However, the detailed role that microbes play in the nucleation and subsequent precipitation of micrites remains to be resolved. Herein we undertook a detailed geobiological characterization of laminated lime mudstone from the Middle Triassic Guanling Formation in Yunnan Province, southwestern China. Morphological features, together with previous geobiological investigations, suggest that the laminated lime mudstones represent the former presence of microbial mats. These lime mudstones consist mainly of calcite, dolomite and quartz, with clay minerals and pyrites as subordinate components. In particular, micro-analysis shows copious nano-globules (65–878 nm) and capsule-shaped nano-rods in laminations. These low-Mg calcite nano-globule aggregates are closely associated with mucilaginous biofilms resembling extracellular polymeric substances (EPS). Nano-sized globules coalesce to form semi-euhedral micrite crystals. We suggest that a decaying hydrolytic destruction of the EPS by microbial communities within microbial mat leads to the precipitation of the nano-globules by enhancing alkalinity in local micro-environment. As an intermediate, these nano-globules further aggregate to form micrite crystals possibly through a dissolution-reprecipitation process.

A new species of rugose coral, Sanidophyllum dubium n. sp., and the typical Emsian (Early Devonian) rugose coral Xystriphylloides nobilis are described from the Mia Le Formation in northern Vietnam. The lower Emsian index conodonts ranging from the Polygnathus excavatus zone to the P. nothoperbonus zone are illustrated. The biostratigraphic correlation between northern Vietnam and South China shows that the Mia Le Formation in northern Vietnam is early Emsian in age, and its upper part can be correlated with the lower part of the Shizhou Member of the Yukiang Formation in Liujing, Guangxi and its equivalents in South China. Based on the study of the lower Emsian biostratigraphic sequence, the disappearance of Xystriphylloides nobilis fauna in the overlying bed of the uppermost Mia Le Formation and the extinction of the “tonkinensis fauna” (sensu lato) in the interval between the basal Si Phai Formation and the uppermost Mia Le Formation demonstrate the influence of the Yujiang Event in northern Vietnam.

An integrated study of biostratigraphy, microfacies, and stable carbon isotope stratigraphy was carried out on the late Famennian-early Asselian carbonates of the Long’an section in Guangxi, South China. Stable carbon isotope studies in the Long’an section have revealed four major positive shifts of δ13C values in the Carboniferous strata in South China. The first shift occurred in the Siphonodella dasaibaensia zone in the Tournaisian, with an amplitude of 4.19‰. The second shift occurred near the Visean/Serpukhovian boundary, with an amplitude of 2.63‰. The third shift occurred in the Serpukhovian, with an amplitude of 3.95‰. The fourth shift occurred in the Kasimovian, with an amplitude of 3.69‰. Furthermore, there were several brief positive δ13C shifts during the late Famennian to early Tournaisian. All of these shifts can be well correlated globally, and each corresponds to sea-level regressions in South China and Euro-America, indicating increases in ocean primary productivity and global cooling events. Chronologically, the four major positive excursions of δ13C, together with several brief positive δ13C shifts that were observed during the late Famennian to the early Tournaisian, correspond to the well-accepted Glacial I, II, and III events.

Carboniferous conodonts from the candidate GSSPs of the four stages Serpukhovian, Moscovian, Kasimovian and Gzhelian in the Naqing and the adjacent sections of South China have been intensely studied in recent decades. The Carboniferous conodont zonation of China is updated based on the conodont material from South China; 39 conodont zones including 11 Tournaisian zones, 4 Visean zones, 3 Serpukhovian zones, 6 Bashkirian zones, 5 Moscovian zones, 5 Kasimovian zones and 5 Gzhelian zones are separated and discussed in detail. Species of the genera Siphonodella, Polygnathus, Protognathodus and Gnathodus dominate the zonation for Early Mississippian (Tournaisian) strata, Pseudognathodus, Lochriea and Gnathodus are most important for the zonation for Middle and Late Mississippian (Visean and Serpukhovian) strata, Declinog-nathodus, Idiognathoides, Neognathodus provide the zonation of early Bashkirian strata and Diplognathodus, Mesogondolella, Idiognathodus and the related genera Swadelina and Streptognathodus provide the zonation for late Bashkirian through the middle and late Pennsylvanian interval. In South China, the Carboniferous conodont zonation is mainly characterized by deep-water conodont biofacies with Siphonodella, Lochriea, Gnathodus, Declinognathodus, Idiognathoides, "Streptognathodus" expansus group, Diplognathodus and Streptognathodus. The updated Carboniferous conodont zonation of China is dominated mainly by cosmopolitan species, which may eventually allow refined global correlation.

A new Devonian oxygen isotope record based on 180 measurements of conodont apatite is reported from South China. The comparison with published Devonian δ18Oapatite data shows a considerable offset between records from different paleocontinents. This difference can be interpreted by regional variations in salinity, with the epicontinental seas having a distinctly lower salinity and δ18Oseawater than the open ocean due to the influence of fresh-water runoff. Our findings suggest that the oxygen isotope record from open ocean settings is the preferred archive for reconstructing the history of ocean temperature and/or ice volume over the Phanerozoic. Despite regional differences, the South China and European records show similar long-term trends characterized by a pronounced cooling during the Pragian to Eifelian followed by significant warming over the Eifelian/Givetian to Frasnian, and a further cooling starting in the Famennian, accelerating in the earliest Carboniferous. The Early Devonian cooling coincided with early vascular plant root − soil interactions and a significant diversity increase in both spores and megaplant fossils, suggesting that the rise of rooted vascular plants may have played a key role in triggering climate cooling. Subsequent climatic warming over the Middle to Late Devonian transition may have been linked to metamorphic CO2 input from the Acadian Orogeny, while Famennian cooling occurred in a context of exposure and weathering of basalts and ophiolites and coincided with the advent of seed plants. We conclude that climate changes during the Devonian were likely driven by a combination of plant evolutionary advances and changes in tectonics. We further test these interpretations by running the COPSE (Carbon, Oxygen, Phosphorus, Sulfur and Evolution) biogeochemical model. The model prediction is capable of reproducing the pCO2 record under these scenarios, although the model is not capable of reproducing the degree of temperature variation, likely due to its simplicity.

The expansion of land plants is considered to have played a key role in triggering the Late Paleozoic Ice Age (LPIA), but evidence linking climatic events to terrestrial floral changes is limited. Here, we generated bulk carbonate δ13C, conodont δ18O and 87Sr/86Sr profiles from the lowermost Carboniferous of South China and Vietnam in order to investigate their relationship to contemporaneous land plant evolution. Climatic cooling in the mid-Tournaisian coincided with large perturbations to the global carbon cycle and continental weathering regimes as well as with a major diversification episode among seed plants. These relationships are consistent with terrestrial floral changes triggering intensified weathering of basalts (i.e., lower 87Sr/86Sr), enhanced marine productivity (i.e., higher δ13Ccarb), and reduced atmospheric pCO2 and attendant global cooling (i.e., higher conodont δ18O). The results of our study suggest that expansion of terrestrial floras was a key driver of Early Carboniferous climate change.

© 2020 This study is a detailed palaeontological and palaeoecological analysis of a middle Givetian (Middle Devonian) high-diversity patch reef located in a platform interior setting in South China. The location is Jiwozhai, Guizhou Province, in the Dushan Formation. A total of 83 species (including 23 undetermined species) belonging to 44 genera of reef organisms were identified, based on a detailed statistical analysis from 28 quadrats on the vertical section of the patch reef. The main reef builders are laminar and encrusting-behaviour stromatoporoids, laminar tabulate corals, and laminar encrusting chaetetids, forming coverstones to build the reef framework, while abundant massive and branching tabulate corals and solitary rugose corals are also important for the formation of the reef by filling the spaces between the components of the coverstones. Reef dwellers including brachiopods, bryozoans, tubeworms, calcified cyanobacteria and gastropods, are only scarcely distributed in the Jiwozhai patch reef, having little impact on the distribution pattern. Consistent with the densely distributed species at Jiwozhai, complex ecological relationships, including extensive encrustations, spatial competition, and symbiosis have also been found among different organisms. The high biodiversity level of the Jiwozhai patch reef in platform interior emphasizes that understanding of species richness and diversity of functional groups in different habitats is critical for Givetian reef ecosystem reconstruction. Location of the patch reef in a platform interior may be the reason for the high diversity biota. The results from the Jiwozhai patch reef are evidence for a stable reef structure with evenly distributed major reef-frame builders and complex ecological relationships. The high level of species diversity is a common feature in South China, as well localities of many other palaeocontinents during the Givetian Period. Strategic Priority Research Program (B) of Chinese Academy of Sciences (XDB26000000), National Natural Science Foundation of China (grant Nos. 41772004, 41802002) and Geological Survey projects of China geological survey (No. DD20201121, 12120113063200).

Syringoporoid tabulate corals are one of the most common benthic sessile organisms in the upper Famennian Etoucun Formation at the Huilong section, Guilin, South China. A multivariate morphometric analysis based on five morphological characters was applied to 29 coralla from three intervals in the formation. Cluster analysis, principal coordinate analysis, non-metric multidimensional scaling, and an examination of the qualitative morphological characteristics revealed the presence of four morphospecies representing Chia hunanensis Jia, 1977, Tetraporinus virgatus Tchudinova, 1986, Fuchungopora multispinosa Lin, 1963, and a new species designated as F. huilongensis. Interval A belongs to foraminifer biozones DFZ4 to DFZ6 and contains abundant C. hunanensis and scattered coralla of T. virgatus, whereas intervals B and C which are within foraminifer biozone DFZ7 contain abundant F. multispinosa, sporadic F. huilongensis, and rare fragmented corallites of C. hunanensis. The coralla are commonly tilted or overturned, which is especially obvious in intervals B and C, indicating that most of them settled on a soft substrate and were subjected to periodic high-energy events. The species of Fuchungopora display flexible growth strategies characterised by the fusion of their corallites. The high diversity of syringoporids recorded from South China indicates an obvious radiation of the tabulate corals in the uppermost Famennian. Syringoporids accounted for the majority of tabulate corals recorded in South China in the upper Famennian and represented a relatively high level of palaeobiodiversity before the Hangenberg Crisis.

The Global Boundary Stratotype Sections and Points (GSSPs) for the bases of all seven international Devonian stages have been formally defined and ratified by IUGS till 1996, and nowadays, the main tasks for Devonian stratigraphers include further subdivision of these standard stages, strictly constrained absolute ages for the boundaries, and precise neritic-pelagic and marine-terrestrial correlations using multidisciplinary stratigraphy methods. Establishment of high-resolution Devonian integrative stratigraphy framework and timescale of China would play an important role in improving regional and international correlation, facilitating the recognition of important stratigraphic levels in different paleogeographic settings, and understanding the evolution pattern of biota, paleoclimate and paleoenvironment during this critical interval. Based on well-studied bio- and chronostratigraphy of Devonian in South China and adjacent areas, in combination with recent achievements in carbon isotope stratigraphy, event stratigraphy and radioactive isotope ages, this paper briefly summarize the research history and current status of Devonian chronostratigraphy of China, and for the first time introduce Devonian integrative stratigraphy framework of China. Up to date, few studies have been conducted on the astronomical cyclostratigraphy and high-resolution radioactive isotope dating in Devonian of China, which should be our main focuses in the near future.

The Carboniferous period lasted about 60 Myr, from ~358.9 Ma to ~298.9 Ma. According to the International Commission on Stratigraphy, the Carboniferous System is subdivided into two subsystems, i.e., Mississippian and Pennsylvanian, including 6 series and 7 stages. The Global Stratotype Sections and Points (GSSPs) of three stages have been ratified, the Tournaisian, Visean, and Bashkirian stages. The GSSPs of the remaining four stages (i.e., the Serpukhovian, Moscovian, Kasimovian, and Gzhelian) have not been ratified so far. This paper outlines Carboniferous stratigraphic subdivision and correlation on the basis of detailed biostratigraphy mainly from South China, and summarizes the Carboniferous chronostratigraphic framework of China. High-resolution biostratigraphic study reveals 37 conodont zones, 24 foraminiferal (including fusulinid) zones, 13 ammonoid zones, 10 brachiopod zones, and 10 rugose coral zones in the Carboniferous of China. The biostratigraphic framework based on these biozones warrants the precise correlation of regional stratigraphy of China (including 2 subsystems, 4 series, and 8 stages) to that of the other regions globally. Meanwhile, the Carboniferous chemo-, sequence-, cyclo-, and event-stratigraphy of China have been intensively studied and can also be correlated worldwide. Future studies on the Carboniferous in China should focus on (1) the correlation between shallow- and deep-water facies and between marine and continental facies, (2) high-resolution astronomical cyclostratigraphy, and (3) paleoenvironment and paleoclimate analysis based on geochemical proxies such as strontium and oxygen isotopes, as well as stomatal indices of fossil plants.

Offshore benthic communities were sparse after the end-Ordovician mass extinction. The recent discovery of diverse, abundant sponges in south-eastern China (Anhui and Zhejiang provinces) that flourished during the Hirnantian (Late Ordovician) post-extinction interval raises questions over the extent and ecological significance of the sponge community at that time. This paper dramatically expands the scale of the Hirnantian sponge fauna within South China, with seven new occurrences across 2000 km. These occurrences cross the Ordovician–Silurian boundary interval in the marginal and submerged platform areas of the Yangtze Sea in Jiangsu, Hubei, Hunan, Chongqing and Sichuan provinces. In condensed sections (platform-margin facies), the occurrences are normally represented by extensive spiculite layers, but several sites yield entire, exceptionally preserved body fossils; at Ganggangshan (near Nanjing, Jiangsu Province), such preservation is abundant. The new occurrences are combined with palaeogeographic and tectonic reconstructions to produce a model for the distribution and preservation of the sponge fauna. We argue that the exceptional preservation was due largely to nepheloid layers that were generated during rapid post-glacial transgression that flooded the weathered land surface of the uplifted Cathaysia Block. Nepheloid-layer collapse led to rapid deposition of suspended sediment within the deeper parts of the intra-plate, restricted basin and on adjacent platform margins and slopes. The suspended sediment influx also introduced abundant nutrients to the water column, as indicated by a significant δ13C excursion during the sponge-bearing mudstone interval at Ganggangshan. The combined sponge assemblage was dominant over large areas of the Hirnantian offshore sea floor across South China. We predict that similar occurrences with exceptional preservation will also be found in other continental blocks: abundant articulated sponges may be encountered particularly in restricted basin successions containing rapidly deposited graptolitic mudstones near the Ordovician–Silurian boundary.

The Late Devonian biotic crisis has been studied for a long time mainly on the basis of its taxonomic severity, but with little attention paid on the relationship between biogeography and evolutionary dynamics. In this study, brachiopod faunas across the biotic crisis are surveyed based on revised data compiled from 15 sections in South China. Data of brachiopod faunas are plotted using a network method to detect biogeographic variation and dynamics through the upper Frasnian, lower and middle Famennian. In addition, frequency analysis is performed on the occurrence of brachiopod faunas within the different localities and depositional settings through time. These data show significant taxonomic loss in the five depositional zones in South China, particularly in the littoral clastic and restricted-platform facies. Refuges during the survival interval were probably located in deeper water zones, especially in the inter-platform basin, but also in the peritidal and the open carbonate platform. A decrease of biogeographic connections within the brachiopod occurrence network, accompanied with an increase of low frequency taxa in the survival and recovery intervals, supports biogeographic divergence of ecological preferences of survival and recovery faunas in South China, as well as a turnover of brachiopod faunas through the biotic crisis. Reasons for variation of biogeographic distribution and connections are less known, besides the faunal colonisation that facilitated by sea-level fluctuation through the biotic crisis.

The Yujiang Event is reported here as a newly recognized event that occurred during the deposition of the Early Devonian Yukiang Formation in Liujing, Guangxi, and its equivalents in South China. The first episode of the Yujiang Event is characterized by the extinction of biostrome that is constructed mainly by colonies of rugose coral, tabulatimorph coral and bryozoan as well as the extinction of evolved biota including some brachiopods, bivalves, etc. The age of the first episode of the Yujiang Event dated by conodonts is at the beginning or the lower part of the Polygnathus nothoperbonus Zone. The main episode of Yujiang Event is evidenced by the extinction of the Rostrospirifer tonkinensis Fauna (sensu lato) at the top of Yukiang Formation and by the sudden occurrences of the dolostones and dolomitic limestone of the overlying Moding Formation. At the basal part of the Moding Formation, the new finding of conodont Polygnathus nothoperbonus and dacryconarids Nowakia (N.) barrandei indicates that this episode of Yujiang Event may occur in the upper part of the Polygnathus nothoperbonus Zone. Overlying the Yukiang Formation and its equivalent beds, various lithic deposits correspondingly yielding different biota can be seen widely in many localities and sections in South China and northern Vietnam. Therefore, the Yujiang Event can be recognized not only as a biotic extinction event, but also as a geological event.

The age of the Yukiang (Yujiang) Formation has been shrouded in controversy for more than 75 years. New investigation at the Liujing section, Hengxian County, Guangxi, has revealed a conodont sequence assignable to two Early Devonian conodont zonations: the Eognathodus kindlei?–Polygnathus pireneae Zone and the Polygnathus nothoperbonus Zone from oldest to youngest. The Gaoling and Mahuangling members of the Nahkaoling (Nagaoling) Formation and the overlying Xiayiling Member and lower part of the Shizhou Member of the Yukiang Formation are proven to belong to the Pragian Eognathodus kindlei?–Polygnathus pireneae Zone. The co-occurrence of Polygnathus pireneae and Pol. sokolovi in the lower part of the Shizhou Member demonstrates that this interval can be approximately correlated with the uppermost part of the Polygnathus pireneae Zone. However, precise level identification of the Pragian–Emsian Boundary (PEB) in the Liujing section remains dfficult due to the scarcity of suitable limestone samples for conodont analysis from the middle and upper parts of the Shizhou Member. The Daliancun and Liujing members of the Yukiang Formation and the lower part of the overlying Moding Formation are assigned to the Polygnathus nothoperbonus Zone with the nominal species of this biozone ranging from the bottom of the Daliancun Member to the lower part of the Moding Formation.

The Pennsylvanian to lower Permian succession at Madiyi, South China, represents a nearshore mixed siliciclastic-carbonate system characterized by cyclic sedimentation patterns along a depth gradient from continental siliciclastics to marine open platform carbonates. Various palaeokarst features related to subaerial exposure are widely distributed. Additionally, pedogenesis was pervasive. The identification of twenty-eight sedimentary cycles grouped into five sequences allows the reconstruction of a relative sea-level curve. The cycles represent higher frequency changes superimposed on the long-term evolution. After the initial transgression, the sea level remained relatively low in the late Bashkirian to early Moscovian. Then, it rose stepwise until a major drop occurred in the late Moscovian. Afterwards, the sea level rose again, but marine sedimentation ceased during at least the early Kasimovian. The area was flooded in the late Kasimovian, and the sea level rose until a late Gzhelian sea-level drop. The subsequent marine sequence contains uppermost Gzhelian to upper Asselian deposits, which are capped by lower Permian continental facies associated with a major regional regression. Shallow to deeper marine sedimentary settings recorded high-frequency sea-level changes throughout South China during the late Bashkirian to Asselian. The main transgression–regression cycles are clearly associated with different depositional settings during several time intervals. Furthermore, the good correlations among South China, Ukraine, and the U.S. Mid-continent are rooted in the impact of Gondwanan glaciations on the global sedimentation patterns. However, not all changes at Madiyi are the result of glacio-eustatic sea-level fluctuations; some are related to the local subsidence history and the rise of the Xuefeng Uplift.

LU, J.-F., QIE, W.-Q. & CHEN, X.-Q., July 2016. Pragian and lower Emsian (Lower Devonian) conodonts from Liujing, Guangxi, South China. Alcheringa 40, xxx–xxx. ISSN 0311-5518.Lower Devonian (Pragian and Emsian) conodonts are described from the Liujing section in Guangxi, South China, highlighting the phylogeny of early polygnathids and establishing the basis for faunal correlations with deposits throughout the world. Records of Eognathodus kuangi sp. nov. and E. nagaolingensis Xiong increase the biodiversity of the Pragian eognathodids in South China and represent intermediate stages and probably the latest eognathodids in the evolutionary succession from Eognathodus to Polygnathus. During this evolutionary succession, the degeneration of the sulcus (or the flattening of the upper platform surface) is the most important morphological change, especially in the eognathodid lineage. Polygnathus trilinearis, P. pireneae and P. sokolovi are recognized together for the first time in South China. The contemporan...

A high-resolution and continuous conodont apatite oxygen isotope record spanning the late Visean to Middle Permian is reported from South China, which is interpreted with respect to the ice volume and/or tropical seawater temperature history of the Late Paleozoic Ice Age (LPIA). The presented δ18O record shows significant fluctuations in δ18O from the late Visean to Middle Permian with highest values observed in the Bashkirian (Early Pennsylvanian). The δ18O maximum coincides with a major eustatic sea level fall recorded in low-latitude successions and postdates the significant increases in 87Sr/86Sr and δ13Ccarb measured on well-preserved brachiopod calcite, which can be interpreted as reflecting intensified weathering as consequence of the closure of Rheic Ocean as well as enhanced carbon burial. Both processes may have contributed to lower greenhouse gas levels and cooled down the Earth's surface, triggering the maximum glaciation. The high Bashkirian δ18O values are interpreted to represent the glacial maximum of the LPIA. A coeval change in faunal composition and a decreasing diversity in climate-sensitive marine invertebrates can be ascribed to icehouse cooling and/or loss of habitat. Despite inconsistencies with earlier interpretations that the Early Permian represented the glacial maximum of the LPIA as inferred from Gondwanan glacial sediments records, the suggested Bashkirian glacial maximum agrees well with ice extent estimates based on the regional tectonic history in Gondwana, which suggests that the Bashkirian glaciation occurred during Gondwana interior uplift promoting maximum ice cover of the entire LPIA. However, maximum glaciation is only poorly represented in the depositional record because large parts of the glacial deposits were possibly removed by erosion as outlined by a major regional unconformity.

The end-Devonian was a critical interval in Earth history recording the transition from the Early Paleozoic greenhouse climate to the Late Paleozoic icehouse climate. A mass extinction at this time (the Hangenberg extinction) eliminated ~ 21% of genera and ~ 16% of families of marine invertebrates, although its causes remain poorly understood. The marine nitrogen cycle is intimately related to the nutrient status of seawater, microbial community composition, and the redox condition of the oceans, and, thus, it may provide insights into the mechanism(s) of the end-Devonian mass extinction and climate change. Here, we analyzed high-stratigraphic-resolution bulk-sediment nitrogen isotope variation (δ 15 N bulk ) in three sections from South China: (1) Long'an, an isolated carbonate platform section, (2) Qilinzhai, a shallow-water carbonate platform section between the Yangtze Oldland and the Youjiang Trough, and (3) Malanbian, a shallow-water carbonate platform section between the Yangtze and Cathaysia oldlands and distant from deep-water areas. Our δ 15 N bulk records show a major perturbation to the marine nitrogen cycle in the Middle Siphonodella praesulcata Zone, which is marked by a decline in δ 15 N bullk from + 4‰ to 0‰ at Long'an and from + 4.5‰ to + 2.5‰ at Malanbian. This perturbation coincided with the main end-Devonian mass extinction as well as with a negative shift in carbonate carbon isotopes (δ 13 C carb ). The shift to lower δ 15 N values suggests locally enhanced nitrogen fixation, possibly as a consequence of increased denitrification in response to globally expanded marine anoxia. Thus, these δ 15 N bulk data are consistent with the hypothesis that intense anoxia was the immediate cause of the end-Devonian mass extinction. The δ 15 N bulk records generated in this study suggest that there was significant spatial and temporal variation in the nitrogen isotope composition of seawater nitrate in the Yangtze marginal sea during the latest Devonian. This variation may have been related to the complex paleogeography of the South China Craton, which contained numerous isolated and continent-attached platforms and deep-water basins that influenced watermass circulation, nutrient inventories and primary productivity levels, and watermass ventilation and redox conditions.

To date, 37 species and 2 subspecies (36 species plus 1 species that with 2 subspecies) of the ostracode genus Cribroconcha Cooper, 1941 have been reported worldwide, ranging in age from the Middle Devonian to the Early Permian with an acme during the Carboniferous. Based on the geographical distribution and morphological characteristics of Cribroconcha, two evolutionary lineages (i.e., Lineage 1 and Lineage 2) are identified, which originated in the European and the Kazakhstan plates, respectively. Lineage 1 can be subdivided into three types: 1-A (stable type), 1-B (reshaped type) and 1-C (spiny type). Lineage 2 has a simpler pattern of evolution compared to Lineage 1. Although there were certain accompanying changes in the morphology of carapaces, the general pattern and most successful evolutionary novelty of Cribroconcha appears to be the appearance of spiny forms in the Early Carboniferous, which continued to be preserved until the Early Permian. The habitats of Cribroconcha may have changed from shallow, warm waters to deep, calm and colder waters in the basinal environments. Four Cribroconcha biozones, extending from the Givetian Stage to Serpukhovian Stage are established in the Euramerica plate, namely C. beckmanni Zone, C. triquetra triquetra Zone, C. cooperi Zone and C. caneyensis Zone.

The Guadalupian Epoch is marked by the formation of the Pangean supercontinent, global sea-level change, rifting and drifting of the Cimmerian continents, formation of large igneous provinces and dramatic biotic changes. A high-resolution biostratigraphic, chemostratigraphic and high-precision geochronologic framework of this critical transition is fundamental to understanding these events. Extensive studies of the latest Cisuralian and Guadalupian Series in both South China and North America reveal the same conodont lineages, but the conodont interval zones based on Jinogondolella within the Guadalupian Series are slightly diachronous. High-precision U-Pb geochronological studies (CA-ID-TIMS method) calibrate the base of the Guadalupian Series (base Roadian) at 273.01 ± 0.14 Ma. A previously reported age from an ash bed overlying the Emeishan flood basalts, 259.51 ± 0.21 Ma, is adopted for the Guadalupian/Lopingian boundary (GLB). Based on recently published geochronology and Bayesian age modeling from the Guadalupian Series, the base of the Capitanian is constrained at 264.28 ± 0.16 Ma and the base of the Wordian is interpolated to be 266.9 ± 0.4 Ma. The Illawarra Reversal is of early-middle Wordian age. Both North America and South China possess a distinct negative δ13Ccarb excursion of 3-5‰ at the latest Kungurian and early Roadian (LK-ER CIE), which coincides with the early stages of a significant 3rd order sea-level rise. The large end-Guadalupian δ13Ccarb negative excursion may have been affected by post-depositional diagenesis or a warming event associated with the Emeishan volcanism. The 87Sr/86Sr ratios in both regions declined from the latest Kungurian to the late Capitanian, but have different ratios and reveal several fluctuations in the middle Guadalupian. Measured δ18Oapatite values suggest that the Delaware Basin was 3-4°C cooler than the eastern Yangtze Block. Analysis of a new high-resolution database of marine taxa indicates only a minor pre-Lopingian diversity drop from 261.04 Ma to 259.98 Ma, which coincides with the peak Emeishan volcanism. The widely-perceived “end-Guadalupian mass extinction” in North America is evidently masked by, and possibly an artefact of, a stratigraphic truncation effect due to rapid lithofacies changes from limestone to laminated evaporites with the closure of the west Texas basins.

The global Hangenberg Crisis near the Devonian-Carboniferous boundary (DCB) represents one of the major Phanerozoic mass extinction events, which shaped the roots of modern vertebrate biodiversity. Marine anoxia has been cited as the proximate kill mechanism for this event. However, the detailed timing, duration, and extent of global marine redox chemistry changes across this critical interval remain controversial because most of the studies to date only constrain changes in local or regional redox chemistry. Thus, opinions on the significance of anoxia as a kill mechanism are variable—from anoxia being a primary driver to being relatively unimportant. In this study, we explore the evolution of global marine redox chemistry using U isotopes of marine limestones. The δ 238 U trends at Long'an section in South China document systematic oscillations with three negative shifts punctuated by two positive events in between. The magnitude of the δ 238 U oscillations implies that the sediments do not record contemporaneous seawater with a constant offset at all times. The lack of covariation between δ 238 U data and diagenetic indicators (e.g., Mn and Sr contents, Mn/Sr ratio, δ 18 O) suggests that the δ 238 U trends are not produced by the same post-depositional diagenetic processes. Instead, trace-metal enrichments suggest that more reducing conditions prevailed during the deposition of the two positive events. We present plausible model scenarios that fit the observed δ 238 U trends in the context of redox-sensitive trace metal data suggesting marine anoxia expanded in the latest Devonian oceans to cover >5% of the continental shelf seafloor area. The rapid expansion of marine anoxia coincident with the onset of the Hangenberg Crisis supports marine anoxia as an important kill mechanism. Biogeochemical modeling of the coupled C-P-U cycles suggests that intensified continental weathering, for example, assisted by the spread of seed plants with deeper root systems at this time, could have triggered expansion of marine anoxia and other global changes (e.g., positive excursion in δ 13 Ccarb and decrease in sea surface temperature) in the latest Devonian. The anoxic event is inferred to have been transient as climatic cooling would have reduced weathering fluxes.

To improve regional and intercontinental correlation of the uppermost Devonian–lowermost Carboniferous, we examined the conodont faunas and carbon isotopic records of the Tangbagou Formation in the Qilinzhai section, southern Guizhou, South China. The Tangbagou Formation is a succession of mixed carbonate–siliciclastic rocks that accumulated on a shallow-water platform under normal marine conditions. Seven conodont zones for shallow-water biofacies in South China, the Cl. gilwernensis–Cl. unicornis Zone, the Po. spicatus Zone, the Si. homosimplex Zone, the Si. sinensis Zone, the Si. eurylobata Zone, the Ps. multistriatus Zone and the Po. co. porcatus Zone in ascending order, are recognized in the Tangbagou Formation. Although apparently limited in its value for global correlation, this conodont zonation is more applicable to shallow-water biofacies in South China. Carbonate samples have yielded carbon isotopic signatures consistent with those recorded in Euroamerica sections, in particular showing four distinct characteristics: (1) the peak values of Hangenberg Carbon Isotope Excursion (HICE) during the latest Devonian, (2) a minor positive shift (P1) in the Si. homosimplex Zone during the early Tournaisian, (3) a second minor positive shift (P2) in the Si. sinensis Zone and (4) the middle Tournaisian Carbon Isotope Excursion (TICE) in the middle part of the Tangbagou Formation. The similarity in peak values (~5.5‰) and magnitude of TICE for the Qilinzhai and Belgian sections indicates that the Euro-asia δ13Ccarb trends may reflect the changes in global mean ocean δ13CDIC, rather than having been overprinted by local carbon cycling. Integration of conodont biostratigraphy and δ13C stratigraphy provides a powerful tool for stratigraphic correlation. Copyright © 2015 John Wiley & Sons, Ltd.

Carbonate carbon (δ13Ccarb) and bulk nitrogen (δ15N) isotopic variation during the mid-Tournaisian was analyzed in the Malanbian and Long'an sections of South China. Their C-isotope profiles document a large positive excursion, herein termed the ‘mid-Tournaisian carbon isotope excursion’ (TICE), during the Siphonodella isosticha conodont Zone, although its magnitude differed between the two sections (> 6‰ at Malanbian versus ~ 3‰ at Long'an). The TICE event coincided with sedimentologic and oxygen-isotopic evidence of climatic cooling and glaciation during the mid-Tournaisian. It was probably triggered by an increase in organic carbon burial rates linked to changes in global-ocean circulation. The study sections also document a large positive shift in δ15N, from 1.7‰ to 4.2‰ at Malanbian and from 1.5‰ to 3.8‰ at Long'an. The N-isotope shift shows no termination within the study sections and is likely to mark the onset of an extended interval of 15N-enriched marine nitrate that lasted for the duration of the Late Paleozoic Ice Age. Its initiation coincided with TICE and thus may have been linked to ocean-circulation changes that resulted in intensified upwelling and an increase in water-column denitrification. The continuation of the N-isotope shift over millions of years may have been linked to glacio-eustatic fall and a long-term shift in the locus of denitrification from continental-shelf sediments to continent-margin oxygen-minimum zones. The TICE event thus marks the onset of sustained continental glaciation during the Late Paleozoic Ice Age.

An integrated study of the litho-, bio-, and chemostratigraphy of the Devonian–Carboniferous boundary at four sections (Qilinzhai, Malanbian, Gedongguan and Long'an) in South China was undertaken in order to better understand paleoenvironmental changes and controls on δ 13 C carb variation during the Hangenberg Crisis. Sedimentological data record a major regression in the Middle Siphonodella praesulcata Zone, which coincided with the Hangenberg Extinction (HE) in South China. Our new δ 13 C carb data document a negative δ 13 C carb shift near the base of the Middle S. praesulcata Zone, which may have been related to the HE. Prior to and during the HE, respiration of organic matter contributed abundant 12 C-enriched dissolved inorganic carbon (DIC) to the restricted Nanning carbonate platform, resulting in a negative vertical δ 13 C DIC gradient in the study area. In the Upper S. praesulcata Zone, all four sections exhibit a positive δ 13 C carb shift, suggesting that a vigorous biological pump existed in the aftermath of the latest Devonian glaciation. However, peak δ 13 C carb values differ markedly among the study sections, suggesting that local carbon cycling processes played an important role during the initial post-glacial transgression.

The conodont faunas of Tournaisian shallow-water carbonates from central Guangxi are described mainly for biostratigraphic purposes. A complete series of samples was collected from the Long’an and Du’an formations in the Long’an section. These formations are characterized by lime-mudstone, skeletal and peloidal wackestone, packstone and grainstone with typical shallow-water biota. Overall, these samples produced 809 identifiable Pl elements, belonging to 50 species in 11 genera, of which one species and one subspecies are new. The fauna enables the establishment of seven biozones (in ascending order): Polygnathus spicatus, Siphonodella homosimplex, S. sinensis, S. dasaibaensis, Polygnathus communis carina Acme, Gnathodus cuneiformis, and P. communis porcatus zones. Based on these new collections from central Guangxi and on data from the literature, a conflated Tournaisian conodont zonation is proposed for shallow-water successions in South China. Most of the conodont zones correlate well with their counterparts recognized in Western Europe, which may be of greater significance in stratigraphic correlation than previously thought.

The Late Paleozoic (Early Devonian to Middle Permian) was an interval of profound changes in Earth-surface systems, reflected in dynamic interplay among the biosphere, hydrosphere, atmosphere, and geosphere. Major events transpired, including the colonization of landmasses by vascular plants, the assembly of the supercontinent Pangea, two first-order mass extinctions (the Frasnian-Famennian and Devonian-Carboniferous boundary events), and the most severe icehouse climate mode of the Phanerozoic (the Late Paleozoic Ice Age, LPIA). The goals of the present review are (1) to summarize major global developments in climate, oceanography, and paleobiology during the Late Paleozoic, (2) to examine the roles of land plant evolution, global tectonics, and large igneous province magmatism in driving these developments, and (3) to serve as an introduction to the 23 contributions to this special issue of Palaeogeography, Palaeoclimatology, Palaeoecology, indicating how they advance our knowledge of various scientific issues related to these developments.

Mercury (Hg) chemostratigraphy is an efficient tool for tracing distal volcanism, as suggested in many recent studies. In our research, we focused on Hg and other trace element contents in two Devonian-Carboniferous boundary sections from two different and spatially distant areas. The Lesni lom section (Czech Republic) was located in the south-eastern part of the Laurussia plate and the Duli (Guangxi, China) section in the South China Plate. In both studied sections, the highest Hg, Hg/Fexs or Hg/Al values occurred at the Devonian-Carboniferous boundary. In Lesni lom, organic matter remineralization was connected with origin of pyrite which sequestered a part of the Hg content. The decoupling of Hg and TOC within the Duli section strata and the significant correlation with Al and Fe may suggest that Hg is hosted primarily by clay particles, derived from the landmass into the marine realm. Mercury was also incorporated into pyrites but the poor correlation between Hg and TS (total sulfur) indicates a possible loss of S during oxygenation events. In the Lesni lom section, and partly in the Duli section, Fe and Mn redox cycling may have played an important role in sediment Hg content. Both sections were influenced by widespread hydrothermal and volcanic activity, indicated by positive Eu anomalies, MSI, Fe/Ti, Zr/Al2O3 and Ti/Al2O3 values. It remains to be clarified whether, besides the interplay of local magmatic activity and redox oscillations, there may have been some additional influence of the multi-phase Viluy Large Igneous Province, although its younger phase (364.4 ± 1.7 Ma) slightly precedes the Hg anomalies obtained.

A middle Viséan (Mississippian) coral biostrome is reported for the first time from the Shangsi Formation in Yashui area, central Guizhou Province, southwestern China (palaeogeographically located in eastern Palaeotethys). The biostrome, which is about 500 m across and 2.5–3.9 m thick, is laterally variable and composed of rugose and tabulate corals with low taxonomic diversity comprising 4 rugose and 1 tabulate coral species belonging to 5 genera. Three growth stages of the biostrome are distinguished, based on different compositions of coral taxa. Average coral contents of the biostrome increase from 38.7% to 72.0% upward and themain builders are Siphonodendron pentalaxoidea, Syringopora sp. and Kueichouphyllumsinense. Associated fossils include abundant brachiopods, crinoids and common foraminifers togetherwith rare calcareous algae, bryozoans, gastropods and ostracods. Relative sea-level changes are interpreted to have controlled growth and demise of the biostrome, which grew continuously during sea-level rise and decreasing water energy, as evident from the gradually increasing of micrite content and in situ coral colonies. However, the biostrome declined and died as the sea level fell and hydrodynamic energy strengthened, indicated by an increase of bioclasts and sparry calcite cement (indicating lack of micritic matrix due to higher energy) overlying the biostrome. This coral biostrome has similar biotic composition to middle to late Viséan coral biostromes in Europe and North Africa (western Palaeotethys). The approximately coeval occurrence of coral biostromes in both eastern and western Palaeotethys suggests that a relatively global warm episode existed during the Viséan Stage. Prof. F.T. Fürsich of Erlangen University and Dr. J.T. Chen of Nanjing Institute of Geology and Paleontology, Drs. Yuping Qi and Zhaoliang Ma, Dr.Markus Aretz and National Natural Science Foundation of China

Evaluating the pre-Jurassic marine source rocks in China has been difficult because these rocks are generally too high- or over-maturated for most traditional methods to work. As to the remaining parameter TOC (%), its lower limit for recognizing the carbonate source rocks in China has been in dispute. Nineteen Phanerozoic sections in the Middle-Upper Yangtze Platform and the Guizhou-Hunan-Guangxi Basin have been studied in search for a different approach to complementing the traditional evaluation method for these source rocks. We have applied a geobiological approach to tracing the organic carbon (OC) output and accumulation from the living stage (primary productivity) to the post-mortem deposited remains, and finally to the preserved burial organics. Four biological and geological parameters are employed to represent the OC of the three stages. A series of proxies of these parameters are discussed and integrated to establish a geobiological evaluation system independent of TOC and other traditional methods. Here we use the Guangyuan section in Sichuan as an example for the geobiological evaluation. Our results indicate that in the argillaceous rocks, the geobiological parameters show the qualified source rocks in accordance with high TOC values; but in the carbonates, the good source rocks delineated by the geobiological parameters have a wide range of TOC, from 0.03% to 1.59%, mostly