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A new, latest Ordovician brachiopod fauna is systematically described from the Hwe Mawng Purple Shale Member (Hirnantian) of the Naungkangyi Group of Pa-thin area, Mandalay Region, Myanmar, revealing one of the most diverse representatives of the typical Hirnantia Fauna. Rhynchonelliformean, craniiformean and linguliformean brachiopods studied belong to 23 genera and a few indeterminate taxa, among which the most abundant genus Kinnella , along with the four common genera or subgenera ( Paromalomena , Pseudopholidops , Coolinia , and Dalmanella ), and other genera (such as Cliftonia , Draborthis , Hindella , Hirnantia , Leptaena , Mirorthis , Plectothyrella , Pseudopholidops , Skenidioides , and Xenocrania ) are recorded for the first time. This high diversity Hirnantia Fauna represents an ecological differentiation within the benthos of the Sibumasu Terrane during the end Ordovician global crisis. The palaeoeco-unit named herein as the Kinnella - Paromalomena community is assigned to lower BA3. This paper includes a taxonomic revision with the following conclusions: 1) Sinomena Zeng et al. and Yichangomena Zeng et al. are treated as junior synonyms of Eostropheodonta Bancroft; 2) Hubeinomena Zeng et al. is regarded as a juvenile form of Coolinia Bancroft; 3) Paramirorthis Zeng et al. is considered an immature growth stage of Mirorthis Zeng; 4) Shanomena Cocks and Fortey is treated as a junior synonym of Paromalomena Rong; 5) Scenidium ? medlicotti Reed is redesignated as the type species of Kinnella Bergstrom to replace Hirnantia ? kielanae Temple. The distribution of the Hirnantia Fauna in Myanmar, Thailand and western Yunnan of the Sibumasu Terrane highlights the distinctive nature of the Mandalay fauna, and the analysis of the Hirnantia Fauna of Sibumasu shows that Sibumasu was not located far from the South China and Lhasa palaeoplates during late Middle and Late Ordovician.

A new, high-diversity, latest Ordovician brachiopod fauna of nearly 800 brachiopod specimens was collected from the Wanyaoshu Formation (Hirnantian) in the Shaodihe section, Mangshi City, western Yunnan, Southwest China. Altogether 22 genera and two undetermined taxa were identified; dominant are Aegiromena, Anisopleurella, Fardenia, Dalmanella, Hirnantia and Hindella, less common, Paromalomena, Leptaena, Eostropheodonta, Cliftonia, Kinnella, Templeella and Plectothyrella, together with some rare Petrocrania, Xenocrania, Pseudopholidops, Palaeoleptostrophia, Skenidioides, Giraldibella, Draborthis, Dolerorthis and Toxorthis. This is one of the most diverse typical Hirnantia faunas, associated with the Kosov Province. The paleobiogeographic relationships between western Yunnan (Southwest China), Myanmar, Yichang (Central China), Tibet (Southwest China) and Kazakhstan are clarified using Network Analysis and NMDS. The fauna studied is most similar to that of Myanmar; both resided on the Sibumasu terrane. However, the recalculated network diagram, when including the data of Hirnantia fauna from the Prague Basin, indicates that the latter is more closely linked to that of western Yunnan, a testament to the very weak brachiopod provincialism during the Hirnantian, mainly due to the influence of dominant cosmopolitan taxa. Some species of the fauna display significant population variation. Two of the dominant taxa, Aegiromena and Anisopleurella are systematically described, whereas the other two common taxa, Fardenia and Hirnantia are measured and their outlines and internal structures analyzed.

Silurian is a period with the shortest duration in Phanerozoic except for the Neogene and Quaternary. It represents an important and unique interval when the biotic diversity recovered quickly after the end-Ordovician mass extinction, different paleoplates or terranes conjoined, big oceans disappeared or narrowed, climate and sea level changed frequently, global biotic provincialism became weaker, some primitive plants started to occupy the land. Silurian is also the first system of which all the chronostratigraphic stratotypes (i.e. the GSSPs) including four series and seven stages were established by the International Subcommission on Silurian Stratigraphy (ISSS). Nonetheless, during the post-GSSP studies conducted by ISSS in the middle 1980s, some Silurian GSSPs were found to have some congenital defects such as no index fossils available that hinder the high resolution subdivision and correlation on a regional or global scale. In this paper, based on the latest development of Silurian study in China, the progress in biostratigraphy, chronostratigraphy, event stratigraphy (such as facies differentiation, heterochrony of black shales, marine red beds, carbonate rocks and reefs), chemostratigraphy, and tectonic stratigraphy (e.g., widespread of the late Silurian rocks in South China and its tectonic implication) are systematically summarized. Some existing problems and the areas to be focused in future work are also discussed. It is suitable for chronostratigraphic study to concentrate not only on the boundary but also doing multidisciplinary analysis on the biotic, chemical, magnetic, environmental, and chronologic aspects, in order to enhance the reliability and the potential for regional and global correlation of a certain GSSP. Some important achievements are expected in these areas in the Silurian study in China: (1) ecostratigraphy and basin analysis of the Llandovery, and the correlation of integrative stratigraphy with a high resolution; (2) establishment of the Wenlock to Pridoli chronostratigraphic framework; (3) the chemo- and magnetic stratigraphy and the age of some key intervals and horizons; (4) further investigation on paleogeography and plate tectonics; and (5) origin and early evolution of the terrestrial ecosystem. Some new breakthroughs might occur in the restudy on some of those problematic GSSPs of some particular series and stages.

Marine red beds (MRBs) occur in many locations in the world during the Telychian Stage but it is unclear how they were related with the highly dynamic Silurian Earth system. To address this question, we conducted a case study involving geochronology, palaeogeographic reconstruction, facies analysis and sea-level history of the middle Telychian MRBs on the western Yangtze Platform of South China. Their distribution pattern indicates that the clastic MRBs owe their origin to the nearby oldlands. Facies analysis indicates that rocks during the study interval generally fall into three depositional belts: shallow subtidal, deep subtidal and shaly basinal belts. A chronostratigraphic framework constrained by both biostratigraphic data and eustatic events shows that, during the early Monoclimacis crenulata interval, olive-gray strata dominated both shallower (shallow and deep subtidal belts) and deeper (shaly basinal belt) settings, while distribution of the MRBs was restricted to deeper waters (shaly basinal belt) on the open-sea side of the platform. This situation changed after the middle M. crenulata interval when the MRB deposition was dominant in both shallower and deeper settings. The diachronous onset pattern of the MRBs coincided with prominent transitions in climatic conditions (from cooler to warmer), eustatic states (from regression to transgression), benthic faunas (decline of normal marine fauna and development of euryhaline assemblages) and reduced primary productivity in the shelf settings, most likely indicative of a change between different oceanic modes. Comparative studies suggest that, the widespread Telychian MRBs in both shallow and deeper water settings owe their origin to a very low organic carbon burial rate, which could be results of higher oxygen content in the ocean water and lower primary productivity.

Network and frequency distribution analyses of global brachiopod occurrences in the earliest Silurian (Rhuddanian–Aeronian) revealed that brachiopod recovery from the end-Ordovician mass extinction during the early–late Rhuddanian was represented mainly by the reestablishment of Late Ordovician cosmopolitan holdover taxa. Brachiopods nearly doubled their generic diversity from Rhuddanian to Aeronian, owing to the radiation of both endemic and cosmopolitan taxa, associated with an overall post-glacial amelioration of global environment and increased habitat heterogeneity as a result of marine transgressions and expansion of epeiric seas. A drastic turnover from the Ordovician-type to Silurian-type brachiopod faunas took place in the Aeronian, several million years after the terminal Ordovician mass extinction. Compared with the orders of orthides and strophomenides that radiated and predominated in the Ordovician, the atrypides and pentamerides displayed pulses of drastic diversification from the Rhuddanian to Aeronian, mainly in tropically located paleoplates, to become the most abundant and diverse brachiopod orders in the Silurian. Atrypides recovered in the early Rhuddanian, whereas diversification of pentamerides was delayed until the Aeronian and becoming widespread in South China, Kazakhstan terranes, Baltica, Avalonia, and Laurentia.

The end Ordovician mass extinction (EOME) was the second most severe biotic crisis in Phanerozoic, and has been widely linked to a major glaciation. However, robust geochronology of this interval is still lacking. Here we present four successive high-precision zircon U–Pb dates by isotope dilution thermal ionization mass spectrometry (ID-TIMS) for biostratigraphically well-constrained K-bentonites of a continuous Ordovician-Silurian boundary section at Wanhe, SW China. They include 444.65 ± 0.22 Ma (middle Dicellograptus complexus Biozone), 444.06 ± 0.20 Ma (lower Paraorthograptus pacificus Biozone), 443.81 ± 0.24 Ma (upper Tangyagraptus typicus Subzone), and 442.99 ± 0.17 Ma (upper Metabolograptus extraordinarius Biozone). Calculations based on sedimentation rates suggest a duration of 0.47 ± 0.34 Ma for the Hirnantian Stage, which is much shorter than previously thought (1.4 ± 2.05 Ma in the International Chronostratigraphic Chart ver. 2019/05). The new data also constrain the Hirnantian glacial maximum to ∼0.2 Ma, supporting that its brevity and intensity probably triggered the EOME. Keywords: ID-TIMS, K-bentonite, End Ordovician mass extinction (EOME), Hirnantian stage

The distribution pattern of early Telychian (turriculatus–crispus graptolite biozone) red beds in the Eastern Yangtze Platform of South China is reconstructed based on regional geologic data. The red beds are developed in three areas, which are separated by regions without red deposition. The distribution pattern indicates that the Cathaysian Oldland was the provenance of sediment rich in ferric oxides, which are essential for the formation of red beds. Silurian marine siliciclastic red beds, both in China and worldwide, tended to develop during times of relatively low sea level. Coeval hematitic oolites that formed far from the coast may record a change from reducing to oxidizing conditions in the ocean. Furthermore, it is likely that a fall in global sea level, a transition from reducing to oxidizing conditions in the ocean, and a cooling climate, all of which were closely related to the early Telychian Valgu Event, promoted the global development of marine red beds during this period.

Huang, B., Baarli, B.G., Zhan, R.B. & Rong, J.Y., October 2015. A new early Silurian brachiopod genus, Thulatrypa, from Norway and South China, and its palaeobiogeographical significance. Alcheringa 40, xxx–xxx. ISSN 0311-5518.The smooth atrypoid brachiopod Thulatrypa gen. nov. incorporates two species, a younger (T. gregaria) from Norway, and an older (T. orientalis) from South China, which collectively span the middle Rhuddanian through Aeronian. In Baltica, the genus thrived just below the storm wave base in a tropical BA4 setting extending slightly into BA3 and BA5 respectively, whereas in South China, its representative occurs in a much shallower assemblage (BA2–3). Their palaeobiogeographical implications are carefully investigated. This study supports the arguments that Thulatrypa may have originated in South China in the middle Rhuddanian and extended its range to eastern Baltica in the late Rhuddanian. Larvae may have drifted along a channel from the east to the southwest of Baltica, which suppor...

Classification of extinction events and their severity is generally based on taxonomic counts. The ecological impacts of such events have been categorized and prioritized but rarely tested with empirical data. The ecology of the end Ordovician extinction and subsequent biotic recovery is tracked through abundant and diverse brachiopod faunas in South China. The spatial and temporal ranges of some 6500 identified specimens, from 10 collections derived from six localities were investigated by network and cluster analyses, nonmetric multidimensional scaling and a species abundance model. Depth zonations and structure of brachiopod assemblages along an onshore-offshore gradient in the late Katian were similar to those in the latest Ordovician–earliest Silurian (post–extinction fauna). Within this ecological framework, deeper-water faunas are partly replaced by new taxa; siliciclastic substrates continued to be dominated by the more ‘Ordovician’ orthides and strophomenides, shallow-water carbonate environments hosted atrypides, athyridides and pentamerides, with the more typical Ordovician brachiopod fauna continuing to dominate until the late Rhuddanian. The end Ordovician extinctions tested the resilience of the brachiopod fauna without damage to its overall ecological structure; that commenced later at the end of the Rhuddanian.

The origin and pigmentation of red beds have long been investigated, but mainly on continental settings and carbonate facies (including deep marine red beds). This paper focuses on the shallow marine clastic red beds developed in South China during the Silurian. Based on the sedimentological and geochemical analyses on red layers, green layers and laminae of the Rongxi Formation (Llandovery, Lower Silurian) of Xiushan, southeastern Chongqing, known as the ‘lower red beds’ (LRBs), the following observations are made: (1) the LRBs are primary red beds whereas the green layers are secondary (i.e., formed during early diagenesis); (2) the color differentiation of sediments shows little relevance to the bottom redox potential shift but has a close relationship to grain size and sediment sorting which may be caused by sea level changes and tides. The controlling factors of LRBs pigmentation are significantly different from those of deep marine red beds, and some coeval red beds in North America and Europe. It is noted that, among the shallow marine clastic red beds, the sedimentological and geochemical signatures from the laminae seem to better indicate the environmental conditions than those derived from the layers.

A Foliomena fauna is reported for the first time from the Tarim paleoplate, and stratigraphically from the Yinpingshan Formation (upper Katian, Upper Ordovician) of Querqueke, Kuruktag region, northeastern Tarim, southern Xinjiang, Northwest China. The fauna includes seven species of brachiopods, amongst which three are new and four indeterminate: Anomaloglossa ? sp., Orbiculoidea ? sp., Foliomena xinjiangensis n. sp., Sericoidea minuta n. sp., Kassinella tarimensis n. sp., Rostricellula ? sp., and Anazyga ? sp. These species formed a Sericoidea - Kassinella Association, characterized by very small and well-preserved brachiopods, and well-developed laminations in its hosted mudstone, indicating a deep water environment (corresponding to lower BA5 to BA6). The faunal and sedimentological features suggest its affinity to the typical Foliomena faunal group of deep water origin. Numerical analyses show that the Foliomena fauna in late Katian time differentiated into two major paleogeographically related groups, and the Tarim association has a close faunal affinity to the representatives of this fauna in South China, indicating an active faunal exchange between Tarim and South China before the end-Ordovician mass extinction.

Silurian brachiopods of Middle Llandovery (Aeronian) ages are reviewed, and 215 genera are identified here, compared with 109 in the preceding Early Llandovery (Rhuddanian), indicating a recovery-radiation interval after the end-Ordovician mass extinction. The chief regions in which they are found are the continents of South China, Avalonia-Baltica, Laurentia and Siberia, which were all at tropical latitudes with the exception of Avalonia. In addition, the very large superterrane of Gondwana, although with patchy brachiopod distribution, included temperate faunas, as well as subtropical faunas (in Iran and Afghanistan). Aeronian brachiopods greatly increased in diversity, with dominance of four major groups: orthides and strophomenides (which had flourished previously in the Rhuddanian), pentamerides and atrypides (which became dominant in the Aeronian), and many newly evolved taxa, and occupied deeper water and wider ecological niches (level bottom and reef) than those in the Rhuddanian. Each of the continents has some endemic genera, but there is a greater proportion of them in South China, where some groups (such as the pentamerides and atrypides) are more diverse and others, such as the orthides, are much less common than elsewhere. Affinity indices (AI) show that two megaunits can be recognized: South China and Avalonia-Baltica-Laurentia (ABL); Siberia seems to have been loosely connected with ABL and even more loosely to South China presumably because of its geographical separation in the Northern Hemisphere. The separation of South China from the other megaunits is further supported by cluster analysis.

The brachiopod genus Dicoelosia is generally considered a typical deep-water taxon. New data suggest that some species of the genus may have invaded relatively shallow-water habitats during its geological history. However, there is scant evidence for its invasion of shallow-water environments after the terminal Ordovician mass extinction. Dicoelosia occurs in the shallower-water benthic shelly assemblages of the lower Niuchang Formation (upper Rhuddanian, Llandovery) of Meitan County, northern Guizhou Province, South China. Evidence of a move to shallow water includes its morphology and population structure, regional paleogeography, sedimentology, together with the abundance and diversity of its shallow-water associates. Following the biotic crisis, deep-water environments were barely habitable, and may have driven Dicoelosia into shallower-water niches. The taxon endured the less suitable shallow-water environments until the deep-water benthic zones ameliorated after the recovery, implying a shallow-water refugium existed after the biotic crisis. A new species Dicoelosia cathaysiensis is erected herein. There is only one record of this genus in South China and this unique occurrence may reflect the distinctive paleobiogeography and environments of this region.