The Pagoda Formation is a unique Ordovician stratigraphic unit on South China Paleoplate, and extends widely on the Yangtze Platform for over 2000 km from east to west and 800 km from north to south. This carbonate unit deposits during the early Late Ordovician, with variable thicknesses from meters to a hundred meters, and the Pagoda network structure has been puzzling geologists, especially paleontologists, about its origin for nearly a century. It has been interpreted variously by different researchers and putatively as desiccation cracks, subaqueous shrinkage or syneresis cracks, biogenic traces, tectonic fracturing or loading structures. The researchers on Ordovician from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, in collaboration with sedimentologists and paleontologists from Peking University and Western University, Canada, have been carrying out the sedimentological and paleontological study for over ten years. And their investigation shows a significant regularity on the lateral and vertical distribution of the Pagoda Limestone’s lithologic features, thickness, fauna development etc., and the so called “time-specific” network structure also changes in its morphology with the change of paleogeographic background. In laboratory, by combining the results of paleontology, sedimentology, geochemistry, regional tectonics etc., the research group put forward a new explanation on the origin of the Upper Ordovician Pagoda Formation with network structure in South China. Such "time-specific" network structure is explained as a special kind of meganodules. Its formation require specific paleogeographic background, so South China Paleoplate might be located within equatorial zone (the main body of South China Paleoplate located within 10° south and north of the then equator). This conclusion further supports a specific position for South China during the Late Ordovician and early Silurian, where might be one of the radiation centres in the porcess of the Great Ordovician Biodiversification. Related information of this paper: Zhan Renbin, Jin Jisuo, Liu Jianbo, Patricia Corcoran, Luan Xiaocong and Wei Xin. 2015. Meganodular limestone of the Pagoda Formation: A time-specific carbonate facies in the Upper Orodovician of South China. Palaeogeography, Palaeoclimatology, Palaeoecology.
Fig. 1. A: Distribution of the Upper Ordovician Pagoda Formation, with variable thicknesses of the formation depicted by circles of different sizes(up to 90m); B: modern frequency and intensity map of hurricane/cyclone tracks, no appearance of the strong convection weather above within 10° of the equator; C: the proposed paleogeographic position of South China during Late Ordovician, straddled the equator, lacking of hurricanes and storms, providing well background conditions to the formation of Pagoda meganodular limestone. Fig. 2. Geochemical analyses of nodule and crack of the Pagoda Limestone, showing consistent differentiation (or not) of C, O and ICP-MS elemental contents between them, proving this new explanation of the Pagoda Limestone.
Fig. 3. Comparison of different kinds of nodular limestone (C, D, meganodular limestone, Pagoda Formation) and their interpreted origins (E, F, F showing the origin of the Pagoda Limestone). Scale bars = 10 cm.
The regional Tangbagouan Stage, named from the Tangbagou Formation in southern Guizhou, represents the first Carboniferous stage in China and is essentially equivalent to the global Tournaisian Stage. The Tangbagou Formaiton is a succession of mixed carbonate-siliciclastic rocks that accumulated on a shallow-water platform under normal marine conditions, and the biostratigraphic framework of which was mainly based on brachiopod and rugose coral associations. To constrain the precise age and improve regional and international stratigraphic correlations, Dr. QIE Wekun from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and his collegues present detailed conodont data coupled to carbon isotopic records of the Tangbagou Formation at its hypostratotype section and use this integrated approach to establish high-resolution bio- and chemostratigraphic framework for the Tangbagou Formation. In ascending order, seven conodont biozones are established in the shallow-water sediments, including the Cl. gilwernensis-Cl. unicornis, Po. spicatus, Si. homosimplex, Si. sinensis, Si. eurylobata, Ps. multistriatus and Po. co. porcatus zones. Four distinct positive δ13Ccarb shifts (HICE, P1, P2 and TICE) are also observed in this interval. The study shows that: 1) at its hypostratotype section, the Tangbagou Formation equates with the Upper Si. praesulcata Zone (latest Famennnian) to the middle part of the Sc. anchoralis-latus Zone (late Tournaisian); 2) in shallow-water facies, the Devonian-Carboniferous boundary is tentatively placed near the base of the Po. spicatus Zone, and within the falling limb after the peak values of the HICE; 3) the similarity in peak values and magnitude of TICE for the Qilinzhai and Belgian sections indicate that the Euro-asia δ13Ccarb trends may reflect the changes in global mean ocean δ13CDIC, rather than having been overprinted by local carbon cycling; 4) integration of conodont biostratigraphy and δ13C stratigraphy provides a powerful tool for stratigraphic correlation. The paper was published in Geological Journal, and this research was financially supported by the National Natural Science Foundation of China, Ministry of Science and Technology Foundation Project and State Key Laboratory of Palaeobiology and Stratigraphy, NIGPAS.Reference: Qie, W.K., Wang, X.D., Zhang, X.H., Ji, W.T., Grossman, E.L., Huang, X., Liu, J.S., Luo, G.M., 2015, Latest Devonian to earliest Carboniferous conodont and carbon isotope stratigraphy of a shallow-water sequence in South China. Geological Journal, http://dx.doi.org/10.1002/gj.2710. Integrated rugose coral, foraminifera and conodont biostratigraphy of the latest Devonian-earliest Carboniferous Tangbagou Formation in South China and correlation of δ13Ccarb profiles from the USA, Belgium and South China
Rudists (Order Hippuritida) differing from other mollusks by their bizarre shell-shape. They have important classification, evolutionary, stratigraphical and palaeobiogeographical implications, and the international rudist palaeontologists have carried out researches on rudists more than one and a half hundred years. But in China, there are only about ten publications about rudists and most of the taxa described by them need revision. Recently, based on the investigation of material newly collected and/or photographed in the field, and revision of the previous publications, four rudist species are described from the mid-Cretaceous Langshan Formation of Lhasa block, and their stratigraphical and palaeogeographical significance also clarified by Dr. RAO Xin from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and her colleagues. Auroradiolites gen. nov. was proposed for the grouping of SW Asian to Pacific radiolitid species formerly attributed to Eoradiolites and characterized by a compact (non-celluloprismatic) outer shell layer. The new genus is represented in the Langshan Formation by A. biconvexus (Yang et al., 1982), including several other synonymized taxa. Related information of this paper: Rao, X., Skelton, P. W., Sha, J. G., Cai, H. W. and Iba, Y. 2015. Mid-Cretaceous rudists (Bivalvia: Hippuritida) from the Langshan Formation, Lhasa Block, Tibet. Papers in Palaeontology. (First Published Online: 21 JUL 2015). Map showing the outcrop of the Langshan Formation in the Lhasa block The fossil localities in Rutog (A), Gegyai (B) and Zhongba(C) counties, and the lithological features of the Langshan Formation and the beds yielding rudists Auroradiolites gen. nov.; transverse sections of RV in adumbonal view plus myocardinal elements of LV
South China is an internationally significant region for the study of a series of bio-events across the Ordovician and Silurian transition, where the Global Boundary Stratotype Section and Point (GSSP) for the base of the Hirnantian Series is located. However, the early-middle Hirnantian carbonate sediments, i.e. the Kuanyinchiao Formation, are commonly underlain and overlain by black graptolitic shales of the Wufeng Formation and the Lungmachi Formation respectively. The lack of a complete carbonate sequence across the Ordovician and Silurian (O-S) boundary may cause some problems in the correlation between the GSSP area and the shallow-water carbonate sequence in low latitudes, where graptolites are either absent or very rare. Based on extensive investigation on more than 10 key O-S boundary sections in Shiqian County, northeastern Guizhou Province, Southwest China, Dr. WANG Guangxu from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and his colleagues find that a stratigraphically more complete O-S boundary sequence is exposed at Tunping of the study area, where the sequence could be further subdivided into four lithological layers ascendingly, i.e. Interval 2, 3, 4a and 4b. Only the rocks of Interval 4b can be correlated with limestone (commonly about 1 m thick) at other localities. These carbonate rocks have distinct lithology and contain abundant shelly fossils, including tabulate and rugose corals, conodonts, brachiopods, trilobites and stromatoporoids, many of which show close Silurian affinities suggesting a much younger age than the Kuanyinchiao Formation. This observation, together with some addititional evidence of graptolites indicative of the Akidograptus ascensus biozone immediately overlying the Interval 4b at a nearby section, implies that these shelly strata are of latest Hirnantian age (possibly straddling the O-S boundary). Hence they were most likely deposited after the Hirnantian glaciation, rather than representing glacial cool water sediments (the Kuanyinchiao Formation) as previously thought. Owing to their unique lithology and palaeontology, these newly recognized carbonate rocks, here formally named as the Shiqian Formation, add substantially to our knowledge of O-S boundary stratigraphy in this region. O-S boundary sequence in Shiqian area typically reflect global glacio-eustatic sea-level changes. The recognition of late Hirnantian carbonates together with shelly fossils completes the carbonate sequence of the O-S boundary in the Hirnantian GSSP area of South China. This necessitates the reconsideration of the patterns of faunal turnover of various shelly fossil groups in South China, and thus enhances correlation between the GSSP area and other carbonate-dominated regions lacking graptolites. Related information of this paper: Wang Guangxu, Zhan Renbin, Percival Ian G., Huang Bing, Li Yue, Wu Rongchang. 2015. Late Hirnantian (latest Ordovician) carbonate rocks and shelly fossils in Shiqian, northeastern Guizhou, Southwest China. Newsletters on Stratigraphy, 48(3): 241-252. (DOI: 10.1127/nos/2015/0062) Stratigraphic correlation of the Ordovician-Silurian boundary succession between Tunping (a) and other localities (b) in the Shiqian area, northeastern Guizhou. Note that numbers in parentheses indicate lithostratigraphic divisions used in this study. Palaeogeographical change of the Shiqian area through the Ordovician-Silurian transition and its correlation with Hirnantian glaciation and associated sea-level change. (a). Pre-Hirnantian carbonate sedimentation; (b). Exposure spanning the late Katian to the middle Hirnantian interval; (c). Late Hirnantian carbonate sedimentation associated with sea-level rise; (d). Middle Rhuddanian siliciclastic sedimentation after possible hiatus; (e). Generalized diagram showing the Hirnantian glaciation and its associated sea-level change, modified from Brenchley et al. (2006).
Carbon isotope chemostratigraphy has proved to be an efficient tool for refining the temporal correlation of ancient sedimentary successions. For the Ordovician period, numerous studies have been carried out over the last years, resulting in recognition of a series of distinct anomalies in the carbon isotope record. These ‘excursions’ form the basis for regional and global correlation of sedimentary packages that may be only a few metres thick or even less. Up to now, only one positive δ13C excursion has been formally named from this time interval, i.e., the Middle Darriwilian Isotope Carbon Excursion. Recently, Dr. WU Rongchang from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and colleagues from Lund university (Sweden) and University of Erlangen-Nürnberg (Germany) have carried out carbon isotope analysis of the Lower through Middle Ordovician cool-water carbonates of the Brunflo 2 core from near Brunflo in the J？mtland province of west-central Sweden. The studied succession is 41.55 m thick and includes, in ascending order, the Bj？rk？sholmen Formation, Latorp Limestone, T？yen Shale, and the Lanna, Holen,and Segerstad limestones. The result shows that two distinct positive δ13C excursions that can be used for intra- as well as inter-continental correlations. A positive excursion in the T？yen Shale probably correlates to the mid-late Floian and the Oepikodus evae Zone in Baltica and Precordillera, and the Reutterodus andinus Zone in North America. A continuous increase in δ13C values through the upper Holen Limestone and the preserved part of the overlying Segerstad Limestone is interpreted as the rising limb of the Middle Darriwilian Isotope Carbon Excursion (MDICE), an important tie-point for the global correlation of the J？mtland strata. This study is supported by the National Natural Science Foundation of China, the Swedish Research Council and Crafoord Foundation and the Deutsche Forschungsgemeinschaft.
Related information of this paper: Wu, R.C., Calner, M., Lehnert, O., Perterffy, O. & Joachimski, M.M., 2015. Lower–Middle Ordovician 13C chemostratigraphy of western Baltica (J？mtland, Sweden). Palaeoworld 24, 110–122. doi:10.1016/j.palwor.2015.01.003 Carbon isotope chemostratigraphy in the Brunflo 2 core from J？mtland, Sweden showing the levels of identified δ13C events: LTNICE (Late Tremadocian Negative Isotopic Carbon Excursion), LDNICE (Lower Darriwilian Negative Isotopic Carbon Excursion), and the rising limb of the MDICE (Middle Darriwilian Isotopic Carbon Excursion). There are many fluctuations in the Floian and Dapingian δ13C record; the assumed position of the BDNICE (Basal Dapingian Negative Isotopic Carbon Excursion) is placed in the lower Lanna Limestone where generally slightly lower values are observed.
The Tibet Plateau, which is the highest in the world, is relatively difficult to access; therefore, the stratigraphy and fossils in this area are poorly known although they are very important to interpret the palaeogeographical evolution of different tectonic blocks. Dr. YUAN Dongxun, Dr. ZHANG Yichun from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and their colleagues reported a new discovery of an abundant conodont fauna from the lowest part of the Xiala Formation in the central part of the Lhasa Block, Tibet. This conodont fauna includes three genera and four species (Mesogondolellaidahoensis, M. siciliensis, Vjalovognathusnicolli n. sp. and Hindeodus sp.). The conodont fauna indicates that the lowest part of the Xiala Formation is late Kungurian in age based on the presence of abundant Mesogondolellaidahoensis and the denticle characters of Vjalovognathu snicolli n. sp. The presence of the conodont genus Vjalovognathus, the associated small solitary corals and the absence of any fusulinids clearly suggest a cool-water condition in the lower part of the Xiala Formation. Thus, the Xiala Formation in the central Lhasa Block can be restricted to an age from late Kungurian to Wuchiapingian. This is in contrast to the warm-water faunas consisting of abundant fusulinids, compound and large solitary corals, and warm-water conodonts in the upper part of the Xiala Formation from late Guadalupian to Wuchiapingian in age. This dramatic faunal change suggests that either palaeoclimate had greatly changed from a cold condition to a warm condition after late Kungurian in the peri-Gondwanan region or the palaeogeographical position of the Lhasa Block had drifted northward into the warm-water regime from late Kungurian to Guadalupian. The new family Vjalovognathidae n. fam. and a new species (Vjalovognathusnicolli n. sp.) are proposed, based on abundant specimens from central Tibet.
Reference information of this paper: Yuan Dong-xun, Zhang Yi-chun, Shen Shu-zhong, Henderson, C.M., Zhang Yu-jie, Zhu Tong-xing, An Xian-yin, Feng Hong-zhen, 2015. Early Permian conodonts from the Xainza area, central Lhasa Block, Tibet and their palaeobiogeographical and palaeoclimatic implications.Journal of Systematic Palaeontology. DOI: 10.1080/14772019.2015.1052027. Generalized Permian succession in the Xianzaarea, ranges of fossils at the Mujiucuo section and their implication of palaeoclimatic changes Reconstruction showing the palaeogeographic distribution of Mesogondolellaidahoensis, M.siciliensis,Vjalovognathusshindyensis and V.nicolli. 1, Idaho; 2, West Texas; 3, Sicily; 4, Oman; 5, Pamir; 6, Shiquanhe, Tibet; 7, Xainza, Tibet; 8, Timor; 9, Canning Basin; 10, Carnarvon Basin; 11, Sverdrup Basin.
A Global Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. It is usually defined by the First Appearance Datum (FAD) of a certain taxon within a continuous evolutionary lineage of a fossil species at the stratotype section. For instance, the Permian-Triassic boundary (PTB) GSSP was defined by the FAD of the conodont Hindeodus parvus at the Meishan D Section, and it has been regarded as a unified standard to identify the PTB in the worldwide. However, with the great improvement of high precision radiometric dating technology and high-resoltuion chemostratigraphy, its accurancy and FAD at Meishan D Section is greatly challenged. Recently, Dr. YUAN Dong-xun and his colleagues from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences established a high-resolution conodont succession from a carbonate facies of the Changhsingian Stage and across the PTB at the Daijiagou section, about 35 km north to Chongqing City, Southwest China. Based on the high-resolution biostratigraphical framework at Daijiagou, the end-Permian mass extinction was rapid and it began in the base of the Clarkina meishanensis Zone. Associated with the extinction, a negative excursion of d13Ccarb started in the middle part of Clarkina yini Zone with a progressive shift of 1.6‰ to the middle part of the Clarkina meishanensis, followed by a sharp shift of 3.51‰ from the Clarkina meishanensis Zone to the Hindeodus parvus Zone. This study also suggests that the Triassic index species Hindeodus parvus co-occurred with Hindeodus changxingensis and Clarkina zhejiangensis and directly overlies the Clarkina meishanensis Zone at the Daijiagou section. All these data from the Daijiagou section and some previous studies of other sections in Sichuan, Guizhou provinces and Chongqing City suggest that the first occurrences of Hindeodus parvus are slightly earlier than the sharp negative excursion of d13Ccarb and the FAD at the Meishan GSSP section. They consider that the slight difference of the end-Permian mass extinction, chemostratigraphy and conodont biostratigraphy at Daijiagou and its adjacent areas is most likely subject to different lithofacies, fossil preservation, and the constraint on the stratigraphic resolution rather than a different tempo of the end-Permian mass extinction in a global sense. The controversial results of biostratigraphy and chemostratigraphy between the sections investigated in the paper and the Meishan GSSP section also provide some important implications that accurate chronocorrelation requires the evaluation of multiple, varied stratigraphcal signals rather than relying solely on the FAD of the Triassic index species Hindeodus parvus for recognizing the Permian–Triassic boundary (PTB). Information of the paper: Yuan Dong-xun, Chen Jun, Zhang Yi-chun, Zheng Quan-feng, Shen Shu-zhong, 2015. Changhsingian conodont succession and the end-Permian mass extinction event at the Daijiagou section in Chongqing, Southwest China. Journal of Asian Earth Sciences, 105: 234-251. DOI: 10.1016/j.jseaes.2015.04.002. d13Ccarb profile from upper Changhsingian to lowest Triassic at the Daijiagou section and its correlation with other sections in South China. The grey bar shows the whole negative shift of d13Ccarb in different sections, which is associated with the end-Permian mass extinction. The four sections shown here suggest a general consistent pattern in d13Ccarb profile. However, it is quite clear that the sharp negative excursions of the three sections in Sichuan and Guizhou provinces are all in the middle part of the Hindeodus parvus Zone (A-C), but the same sharp excursion is in the Clarkina meishanensis Zone at the Meishan section (D). Red line shows the correlation based on the first occurrences of Hindeodus parvus; blue line indicates the correlation based on the most negative d13Ccarb excursions. End-Permian mass extinction pattern at the Daijiagou section in Chongqing City.
A synthetic comparison and correlation between the marine and terrestrial end-Permian extinctions. The end-Permian mass extinction reflects the most severe life crisis during the Phanerozoic and was associated with major global environmental changes. However, the consistency of the time and pattern of the terrestrial and marine extinctions remains controversial. In recently, Dr. ZHANG Hua and colleagues from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and MIT presented detailed analyses of the high-resolution biostratigraphical and geochemical data from terrestrial sections in South China. Their analyses show that the transitional Kayitou Formation actually recorded the process of terrestrial mass extinction as evidenced by the mass disappearance of the Gigantopteris megaflora in the lower part, the dramatic reduction in abundance of palynomorphs in the middle, and the last occurrences of plant remains and abundant charcoal fossils in the uppermost part. It is associated with a distinct negative shift of d13Corg, beginning in the middle part of the formation, which is correlative with that in the top of Bed 26 at the marine Meishan section. In addition, the Kayitou Formation is characterized by a distinct shift of lithofacies of fresh lake-swamp or river flat environment from olive/grey/black mudstone, siltstone, fine to coarse sandstone in the lower part to gradually increasing maroon rocks, to purely maroon mudrocks with poorly-sorted breccia, calcic palaeosols and calcareous nodules in the lowest part of the Dongchuan Formation, which indicates a dramatic collapse of soil system associated with rapid deforestation and climatic warming and drying. In the coastal area, the Kayitou Formation contains marine beds with the typical Permian-Triassic mixed faunas and floras which are correlative with the latest Changhsingian marine mixed fauna 1 at Meishan. The Kayitou Formation also recorded a distinct transgression that began in the latest Changhsingian. All above phenomena suggest that the Kayitou Formation is actually the witness of the terrestrial end-Permian mass extinction; and it is mostly or entirely of latest Changhsingian (Permian), rather than Triassic age. This research was published in Palaeogeography, Palaeoclimatology, Palaeoecology. It was supported by the National Natural Science Foundation of China. Related information of this paper: Zhang, H., Cao, C.Q., Liu, X.L., Mu, L., Zheng, Q.F., Liu, F., Xiang, L., Liu, L.J., and Shen, S.Z., 2015. The terrestrial end-Permian mass extinction in South China: Palaeogeography, Palaeoclimatology, Palaeoecology, http://dx.doi.org/10.1016/j.palaeo.2015.07.002
Sinotubulites is a late Ediacaran biomineralizing tubular fossil with a probable animal affinity. It was first reported from the late Ediacaran Dengying Formation in the Three Gorges area, Hubei Province, South China. Subsequently increased fossil localities—including USA, Mexico, and recently central Spain—indicate that it has a worldwide geographic range, thus playing a significant role in intercontinental stratigraphic subdivision and correlation of late Ediacaran successions. As such, Sinotubulites would be served as another potential index fossil other than the coeval index fossil Cloudina. The poor preservational resolution of Sinotubulites specimens significantly limited a full morphological reconstruction and taxonomic disparity on this important taxon. Nonetheless, three dimensionally preserved Sinotubulites through authigenic phosphatization from the late Ediacaran Dengying Formation in southern Shaanxi Province, South China allows a more detailed paleobiological investigation. Recently, CAI Yaoping, a postdoctoral fellow at Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and his colleagues have documented a systematic study on Sinotubulites. The majority of previously published Sinotubulites species are considered as synonymous with the type species: S. baimatuoensis. Three new species—S. triangularis n. sp., S. pentacarinalis n. sp., and S. hexagonus n. sp.—are reported from the late Ediacaran Beiwan Member of the Dengying Formation in southern Shaanxi Province, South China. The three new species are similar to the type species in having nested, multilayered inner and outer tube walls. However, they are different in their polygonal cross sections and longitudinal ridges. S. baimatuoensis is more or less circular in cross section and lack longitudinal ridges on the outer tube wall, whereas S. triangularis, S. pentacarinalis, and S. hexagonus are respectively triangular, pentagonal, and hexagonal in cross section with three, five, and six longitudinal ridges on the exterior surface of the outer wall. The new material adds to the diversity of late Ediacaran biomineralizing animals. The triradial, pentaradial, and hexaradial tubes of S. triangularis, S. pentacarinalis, and S. hexagonus share some intriguing similarities in body symmetry with several early Cambrian tubular fossils, although these Cambrian tubes are not open at both ends. Still, it would be interesting to explore the tantalizing possibility of evolutionary continuity of triradial, pentaradial, and hexaradial tubular animals across the Precambrian–Cambrian boundary. Related information of this paper: Cai, Y., Xiao, S., Hua, H., Yuan, X., 2015. New material of the biomineralizing tubular fossil Sinotubulites from the late Ediacaran Dengying Formation, South China. Precambrian Research, 261(C), 12-24. Schematic diagram showing morphological reconstruction of the four species of Sinotubulites New species Sinotubulites triangularis showing triradial symmetry New species Sinotubulites pentacarinalis showing pentaradial symmetry
A paper entitled “Biostratinomic Analysis of Lycoptera Beds from the Early Cretaceous Yixian Formation, Western Liaoning, China” by Dr. PAN Yanhong et al. from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and their colleagues has been recently published in Palaeontology. Little is known about the palaeoenvironments of the Early Cretaceous lakes of western Liaoning. Uncertainties exist especially about the water depth, water temperatures and annual temperature fluctuations. Here, Dr. PAN et al. analyse the preservation of the most abundant fish of the lakes, the teleost Lycoptera, articulated skeletons of which occur in large concentrations suggestive of mass mortality. Taphonomic features such as degree of disarticulation, orientation patterns and displacement of skeletal elements reveal distinct preservational patterns. They suggest that the water temperature was low during winter and exhibited pronounced seasonal fluctuations. The depth of the lakes was not deep. Possible causes of the fish mortality are discussed, of which anoxia is favoured. This leads to a more refined palaeoenvironmental model for these palaeolakes, which harbour one of the most important Mesozoic Lagerst？tten. Related information of this paper: Yanhong Pan, Franz T. F Fürsich, Jiangyong Zhang, Yaqiong Wang, Xiaoting Zheng, 2015. Biostratinomic analysis of Lycoptera Beds from the Early Cretaceous Yixian Formation, Western Liaoning, China. Palaeontology, Vol 58, pp. 537-561. Examples of Lycoptera A B concentrations. A, monospecific concentration of Lycoptera davidi on slab 1, from Daxinfangzi village, deposited in IVPP. B, monospecific concentration of Lycoptera davidi on slab 2, from Daxinfangzi village, deposited in Tianyu Museum. C, monospecific concentration of Lycoptera muroii on slab 3, from Jinggangshan village, deposited in Tianyu Museum. All scale bars represent 5 cm. Model representing stages C and D mentioned in the text. A, during late autumn to early winter, upwelling toxic bottom waters caused mass mortality of a fish population. B, in winter, the fish carcasses sank to the anoxic lake floor, which favoured the high preservational fidelity of Lycoptera carcasses.
