The Sichuan Basin is one of the most gas-productive continental basins in China, especially with the giant gas fields recently discovered in Puguang and Guang’an regions in the Sichuan Province. The terrestrial coals and mudstones of the Upper Triassic Xujiahe Formation and the Lower Jurassic Zhenzhuchong Formation represent one of the most significant hydrocarbon source rocks within the basin, especially in the western, central, and southern Sichuan Basin. In the northeastern Sichuan Basin, diverse and abundant fossils have been reported from the Xujiahe and Zhenzhuchong Formations, however, paleoenvironment and hydrocarbon significances of these fossils are still less documented, and petroleum studies and exploration of these successions remain limited. The Sichuan Basin is one of the most gas-productive continental basins in China, especially with the giant gas fields recently discovered in Puguang and Guang’an regions in the Sichuan Province. The terrestrial coals and mudstones of the Upper Triassic Xujiahe Formation and the Lower Jurassic Zhenzhuchong Formation represent one of the most significant hydrocarbon source rocks within the basin, especially in the western, central, and southern Sichuan Basin. In the northeastern Sichuan Basin, diverse and abundant fossils have been reported from the Xujiahe and Zhenzhuchong Formations, however, paleoenvironment and hydrocarbon significances of these fossils are still less documented, and petroleum studies and exploration of these successions remain limited. Recently, Dr. LI Liqin, Prof. WANG Yongdong from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Science (NIGPAS), and Prof. Vivi VAJDA from the Swedish Museum of Natural History, Sweden, reported palynofacies analysis results for the first time in the Sichuan Basin, combining with thermal alteration index and geochemical data, interpreted the paleoenvironment and hydrocarbon potential of the Upper Triassic Xujiahe Formation and the Lower Jurassic Zhenzhuchong Formation in the northeastern Sichuan Basin. This result was recently published online an Elsevier international journal Palaeoworld. The palynofacies analysis results showed that, the Upper Triassic and Lower Jurassic sediments in the Sichuan Basin were dominated by phytoclasts, with less abundant palynomorphs and sparse amorphous organic matters (AOMs). Four palynofacies assemblages were identified, reflecting deposition settings in a general proximal and oxic fluvial-deltaic environment, with two distal–proximal sedimentary cycles. The prominent dominance of opaque phytoclasts within the lower Zhenzhuchong Formation may be related to frequent wildfires across the Triassic–Jurassic transition. Palynofacies data (especially the abundance of opaque phytoclasts) may reflect 400 kyr eccentricity cyclicity pattern. The periodic abundance of opaque particles in the studied section may have been caused by increased runoff in the fluvial-delta environment under obliquity cycle-controlled monsoon climate. The present study suggests high potential of palynofacies analysis for cross-regional correlation for the Mesozoic sequences. However, higher resolution palynofacies data are needed in the future, to test the mechanism how orbital cyclicity controls terrestrial sedimentary environment. The palynofacies and thermal alteration index (TAI), combined with geochemical data indicated the presence of type III kerogen in mature to post-mature phases, suggesting gas potential of the Xujiahe and Zhenzhuchong formations in the northeastern Sichuan Basin. This study provides significant implications for better understanding the paleoenvironment variations during the Triassic–Jurassic transition and the future gas exploration in this area. This research was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences, the State Key Laboratory of Palaeobiology and Stratigraphy, and the Swedish Research Council. Reference: Li L., Wang Y., Vajda V., 2020. Palynofacies analysis for interpreting paleoenvironment and hydrocarbon potential of Triassic–Jurassic strata in the Sichuan Basin, China. Palaeoworld. https://doi.org/10.1016/j.palwor.2020.04.007. Lithology, sampled horizons and palynofacies data for the Xujiahe and lower Zhenzhuchong formations at the Qilixia section in the Sichuan Basin APP ternary plots for the analyzed sediments from the Xujiahe and Zhenzhuchong formations at Qilixia Section in the Sichuan Basin
The Triassic–Jurassic (T–J) transition interval (ca. 200 Ma) is characterized by a major mass extinction, one of the five largest Phanerozoic extinctions in Earth history. Major biotic turnover occurred in both marine and terrestrial realms. Much emphasis has been placed on the marine Triassic–Jurassic successions, however, studies on the terrestrial response to this event is still limited, especially in the eastern Tethys region of eastern Asia. In the northeastern Sichuan Basin of South China, the Upper Triassic and the Lower Jurassic successions are well exposed and continuously developed, yielding diverse fossil plant remains, providing important material for exploring the continental ecosystem conditions across the T–J transition in the eastern Tethys. The Triassic–Jurassic (T–J) transition interval (ca. 200 Ma) is characterized by a major mass extinction, one of the five largest Phanerozoic extinctions in Earth history. Major biotic turnover occurred in both marine and terrestrial realms. Much emphasis has been placed on the marine Triassic–Jurassic successions, however, studies on the terrestrial response to this event is still limited, especially in the eastern Tethys region of eastern Asia. In the northeastern Sichuan Basin of South China, the Upper Triassic and the Lower Jurassic successions are well exposed and continuously developed, yielding diverse fossil plant remains, providing important material for exploring the continental ecosystem conditions across the T–J transition in the eastern Tethys. In recent decade, a research team leading by Prof. WANG Yongdong from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Science (NIGPAS) has conducted a series investigations in this region. Recently, Dr. LI Liqin, Prof. WANG Yongdong from NIGPAS, Prof. Wolfram M. Kürschner from the University of Oslo, Dr. Micha Ruhl from the University of Dublin and Prof. Vivi Vajda from the Swedish Museum of Natural History, published a new study in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, which reported about palaeovegetation and palaeoclimate changes across the Triassic–Jurassic transition in the Sichuan Basin, China. A detailed palynological study was performed from the Qilixia section in Xuanhan County of the Sichuan Basin, China, spanning the Upper Triassic (Norian–Rhaetian) (Xujiahe Formation) to the Lower Jurassic (Hettangian–Sinemurian) (lower Zhenzhuchong Formation). Five palynological assemblages were identified, in combination of Principal Components Analysis (PCA) and Sporomorph EcoGroup (SEG) model, they reveal significant ecosystem fluctuations across the Triassic–Jurassic transition. The palynological analysis indicates a lowland fern flora and a warm and humid climate in the Late Triassic (Norian to Rhaetian), interrupted by a cooler interval at the Norian–Rhaetian transition, and followed by a mixed mid-storey forest under cooler and drier condition in the latest Rhaetian. This is followed by a fern-dominated lowland vegetation and a warmer and drier climate during the Triassic–Jurassic transition, and a flora with abundant cheirolepid conifers in the Hettangian–Sinemurian. Most interestingly, the significantly dominant fern vegetation at the Triassic–Jurassic transition interval is similar to the changes reported from geographically widespread sites. The short cooling at the end Triassic and preceding a period of warmer condition at the Early Jurassic, is comparable with records from the western Tethyan realm. It likely reflects (global) vegetation turnover and climatic fluctuations at this time. This global response in vegetation and climate may suggest that, the CAMP emplacement, with a significant influx of SO2 and sulphate aerosols into atmosphere, causing an initial cooling at the latest Triassic. It was later outpaced by global warming from elevated CO2 release in the Triassic–Jurassic transition interval. This study represents the best and higher resolution palynological records of the Triassic and Jurassic transition in siuthern China, providing important evidence for terrestrial ecosystem response to the Triassic–Jurassic event from the eastern Tethys area. This research was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences, the State Key Laboratory of Palaeobiology and Stratigraphy, and the Swedish Research Council. Reference: Li L., Wang Y*., Kürschner, W.M., Ruhl, M., Vajda V.*, 2020. Palaeovegetation and palaeoclimate changes across the Triassic–Jurassic transition in the Sichuan Basin, China. Palaeogeography Palaeoclimatology Palaeoecology. https://doi.org/10.1016/j.palaeo.2020.109891. Late Triassic spores and pollen representative taxa from Xuanhan of Sichuan Basin Early Jurasic spores and pollen representative taxa from Xuanhan of Sichuan Basin Late Triassic–Early Jurassic palynological assemblages and palaeovegetation reconstruction of the Sichuan Basin
Late Triassic–Early Jurassic palynoflora and palaeoclimate implications for the Sichuan Basin
The cephalopod Sinoceras chinense (Foord) is regarded as the index fossil of the Upper Ordovician Pagoda Formation on the Yangtze Platform of South China, with a likely age of early Katian. S. chinense was previously only known from the Upper Ordovician of Chinese blocks/terranes, including South China, Tarim, Tibet (Xizang) and western Yunnan. The cephalopod Sinoceras chinense (Foord) is regarded as the index fossil of the Upper Ordovician Pagoda Formation on the Yangtze Platform of South China, with a likely age of early Katian. S. chinense was previously only known from the Upper Ordovician of Chinese blocks/terranes, including South China, Tarim, Tibet (Xizang) and western Yunnan. During January 2020, an international research team lead by Dr. FANG Xiang from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), and Prof. Clive BURRETT from Mahasarakham University conducted a Sino-Thai joint field trip in western Thailand. During the fieldwork, the first identification of S. chinense is confirmed. This work has been published online in Palaeoworld. These specimens were recorded in a geoconservation named “Nautiloid Site”, located in Si Sawat county of Kanchanaburi Province, western Thailand. Previously, these specimens were wrongly identified as actinocerids, which results in the misjudgments on geological time of the upper part of Tha Manao Formation. The exact identification of S. chinense suggests the upper part of Tha Manao Formation age of early Katian of Late Ordovician, providing evidence for the stratigraphic correlation between the upper part of the Tha Manao Formation in Thailand and the Pagoda Formation (and contemporaneous units) in China. Western Thailand, combined with Baoshan region of western Yunnan, was located on Sibumasu Terrane during the Early Palaeozoic. The confirmed identification of S. chinense in Thailand is the first record in Thailand and alsothe first report in a region outside of China.Moreover, the discovery of the species in the Sibumasu Terrane provides strong support for the palaeogeographic reconstruction and pronounced palaeobiogeographic changes from the Middle to Late Ordovician among the peri-Gondwanan regions. This research has been supported by CAS Strategic Priority Research Program, The Second Tibetan Plateau Scientific Expedition and Research, State Key Laboratory of Palaeobiology and Stratigraphy, Ministry of Nature and Resources of China, and Mahasarakham University. Reference: Fang, X., Li, C., Li, W.J., Burrett, C., Udchachon, M., Zhang, Y.D., 2020. Sinoceras chinense (Foord, 1888) in western Thailand: first identification outside China. Palaeowolrd. https://doi.org/10.1016/j.palwor.2020.06.004 Sinoceras chinense, collected from Si Sawat county of Kanchanabura Province, western Thaialand Distribution of S. chinense in the northeastern peri-Gondwana region
Fossil woods preserved in deposits through the process of permineralization play a crucial role in reconstructing the floristics aspects of ancient forest ecosystems and climatic conditions in deep time. Fossil woods have been widely discovered in terrestrial ecosystems from the dinosaurs ages in the Jurassic and Cretaceous. In China, the fossil woods are mainly documented in the northern China region; however, the records in southern China are relatively poor. Fossil woods preserved in deposits through the process of permineralization play a crucial role in reconstructing the floristics aspects of ancient forest ecosystems and climatic conditions in deep time. Fossil woods have been widely discovered in terrestrial ecosystems from the dinosaurs ages in the Jurassic and Cretaceous. In China, the fossil woods are mainly documented in the northern China region; however, the records in southern China are relatively poor. Recently, a new extinct species of conifer wood dated over 100 million years, i.e. Brachyoxylon zhoui was reported by a research team lead by Prof. WANG Yongdong at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) and Dr. JIANG Zikun at the Chinese Academy of Geological Sciences, in conjunction with the other researchers at the Zhejiang Museum of Natural History, Shenyang Normal University, and University of Bonn in Germany. This finding was recently published in the international journal Historical Biology. The fossil wood specimen was found in the Early Cretaceous Guantou Formation (about 110 Ma) in Yongkang City of Zhejiang Province, which is anatomically different from any reported fossil woods in Zhejiang. Based on comparisons between the present fossil wood material and other relative fossil woods worldwide, a new species of the morphogenus Brachyoxylon, i.e. Brachyoxylon zhoui was established by the research team. The specific name zhoui is dedicated to Prof. ZHOU Zhiyan from Nanjing for his contributions to Palaeonbotany. The terrestrial sediments, largely deposited during the Early Cretaceous in Zhejiang, contain vertebrate fossils, such as dinosaur bones and eggs, and additionally yield abundant fossil woods. The new fossil wood material is silicified and part of the secondary xylem of the tree. The new species is characterized by distinct growth rings, a mixed type of radial tracheary pitting, araucarioid cross-field pitting, high uniseriate rays, and traumatic resin canals. The quantitative analysis of the growth ring was carried out by researchers, indicating that the forest composition was evergreen with a Leaf Retention Time (LRT) of 3–15 years. Combined with the analysis of sedimentology, palynology and paleosols, researchers assume that the Zhejiang region was dominated by a subtropical to tropical and relatively semiarid climate during the Early Cretaceous. The discovery of Brachyoxylon zhoui not only enriches the understanding of the fossil forest composition and paleoclimate but also provides the essential evidence to reconstruct the paleohabitats of dinosaurs in the Early Cretaceous of Zhejiang Province. The study was co-corresponded by Dr. JIANG Zikun at the Chinese Academy of Geological Sciences and Prof. WANG Yongdong at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, other co-authors include Dr. WU Hao at the Zhejiang Museum of Natural History, Associate Professor TIAN Ning at the Shenyang Normal University, and Ph.D. candidate XIE Aowei at the University of Bonn in Germany. This research was co-supported by the National Natural Sciences Foundation of China, the Strategic Priority Program (B) of CAS, the State Key Program for Basic Research & Development of Ministry of Science & Technology of China and the State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS). Reference: Jiang Zikun*, Hao Wu, Ning Tian, Yongdong Wang*, Aowei Xie, 2020. A New Species of Conifer Wood Brachyoxylon from South China and its Palaeoclimatic Implications. Historical Biology, https://doi.org/10.1080/08912963.2020.1755282 The anatomical structures of growth rings, radial tracheary pitting in fossil conifer wood Brachyoxylon zhoui from the Early Cretaceous in Zhejiang Province of China The anatomical structures of cross-field pitting and xylem rays in fossil conifer wood Brachyoxylon zhoui from the Early Cretaceous in Zhejiang Province of China The quantitative analysis of the growth ring and paleoclimate of fossil conifer wood Brachyoxylon zhoui from the Early Cretaceous in Zhejiang Province of China
Trace fossils are the behavioural records of ancient organisms, representing the archives of the interactions between organisms and their living substrates. As a special kind of fossil types, trace fossils may include trails, tracks, burrows and feces excreted by animals (coprolites). Trace fossils are the behavioural records of ancient organisms, representing the archives of the interactions between organisms and their living substrates. As a special kind of fossil types, trace fossils may include trails, tracks, burrows and feces excreted by animals (coprolites). The trace makers may include both skeletonized as well as soft-bodied organisms. Soft bodied organisms normally are seldom to be preserved as fossils. Hence trace fossils potentially provide more complete records of both infaunal and epifaunal organisms, thus facilitating the study of community structures and composition of ancient ecosystems. These characteristics make trace fossils as ideal agents to explore the evolution of early life on Earth, infaunal responses to environmental extremes during mass extinctions, palaeoenvironmental interpretations, and characterization and recognition of significant stratigraphical boundaries in petroleum geology. Recently, Dr. LUO Mao from Nanjing Institute of Geology and Palaeontology , Chinese Academy of Sciences (NIGPAS) collaborated with Prof. SHI Guangrong and Dr. Lee Sangmin from University of Wollongong, Australia, had discovered a new trace fossil assemblage dominated by a potential bivalve trace (Parahaentzschelinia) from the Lower Permian Snapper Point Formation, which records deposition in a storm-influenced delta front environment. Related research results have been published in Palaeogeography Palaeoclimatology Palaeoecology. The dense populations of Parahaentzschelinia trace occurred in two sections, forming stacked Parahaentzschelinia ichnofabrics. Researchers interpreted these ichnofabrics as equilibrium structures, which reflect the trace maker actively adjust their living positions in response to the shifted sediment-water interface, in seeking to remain in an optimal (equilibrium) living position with the local hydrodynamic and depositional conditions (e.g., increased sedimentation or periodic erosion). The trace Parahaentzschelinia is an irregular, funnel-shaped burrow with multiple mud and sand-filled tubes radiating vertically or obliquely upward to the sediment surfaces. Distinct meniscate fills composed of alternating sand and mud laminae are characteristic of nearly all tubes, which are superimposed laterally and vertically. These dense, irregular funnel-shaped burrows may be produced by tellinid-like bivalves based on observations on the metabolic behaviour and burrow morphologies of modern tellinids. According to Dr. LUO Mao, the meniscate fills in Parahaentzschelinia isp. may be the result of successive movements of the siphons, leaving alternating sand and mud laminae. Statistical analysis of burrow lengths and numbers of burrow adjustments suggests up to seven sequences of sediment accumulation events, supplying 3–13 cm thick clastic deposits at each time. A conservative sedimentation rate of 0.24 cm/year was estimated on the basis of two stacked Parahaentzschelinia ichnofabrics and the probable maximum lifespan of modern tellinid genus. This rate is generally comparable to those derived from modern deltaic environments, lending further support to the interpretation that the ichnofabrics were formed in and characteristic of a deltaic setting. The research highlights the utility of stacked equilibrium structures as a sensitive indicator of certain depositional regimes, and its applicability for assessing sedimentation rates as well as depositional conditions in the geological past. The research has been jointed supported by the Strategic Priority Research Program of Chinese Academy of Sciences, the CAS Talents Program, the National Natural Science Foundation of China, and an Australian Research Council. Reference: Luo M*., Shi, G.R*., Lee, S., 2020, Stacked Parahaentzschelinia ichnofabrics from the Lower Permian of the southern Sydney Basin, southeastern Australia: Palaeoecologic and palaeoenvironmental significance. Palaeogeography, Palaeoclimatology, Palaeoecology 541, 109538. doi.org/10.1016/j.palaeo.2019.109538 Intergated section logs of the studied sections at Pretty Beach south (left) and O’Hara Island (right), which both represent the lower part of the Snapper Point Formtion in the southern Sydney Basin Densely occurred Parahaentzschelinia from the section at O’Hara Island. A, Parahaentzschelinia isp. recording sequence of event sedimentation layers. Black arrows indicate individual Parahaentzschelinia isp.. B, Schematic artwork showing the re-adjustments of Parahaentzschelinia to episodic sediment deposition in A
The end-Permian Mass Extinction (EPME) is widely considered to record the largest biodiversity loss coupled with the most severe ecological impact in Earth history. More than 90% of the marine species were killed in less than 200 000 years. In the aftermath of this catastrophe, the Early Triassic was characterized by large, frequent fluctuations in carbon isotopes, extremely high sea-surface temperatures, and widespread anoxic conditions, and even oceanic acidification in the global oceans. The subsequent marine biotic recovery in the Early Triassic has been delayed for a prolonged interval of around 6 million years due to persistent warming and anoxia. The end-Permian Mass Extinction (EPME) is widely considered to record the largest biodiversity loss coupled with the most severe ecological impact in Earth history. More than 90% of the marine species were killed in less than 200 000 years. In the aftermath of this catastrophe, the Early Triassic was characterized by large, frequent fluctuations in carbon isotopes, extremely high sea-surface temperatures, and widespread anoxic conditions, and even oceanic acidification in the global oceans. The subsequent marine biotic recovery in the Early Triassic has been delayed for a prolonged interval of around 6 million years due to persistent warming and anoxia. Studying the biotic recovery after the biggest mass extinction would help us understand the responses and evolutionary mechanism of ecosystems through extreme environmental changes, but also give implications to the management of modern marine ecosystems under global environmental change as those abovementioned environmental extremes are adversely affecting the livelihood of marine organisms. The impact of the EPME on behavioural aspects of the infauna, as reflected in the global abundance and diversity of trace fossils, is less explored. In many instances, trace fossils represent the behavioural records of soft-bodied organisms that have null to very limited preservation in the fossil record. They often supply vital ecological information on ancient communities not available from body-fossil documentations. In order to better understand the behavioural responses of trace makers to environmental perturbations, Dr. LUO Mao and his collaborators including Prof. Luis A. Buatois from University of Saskatchewan, Prof. SHI Guangrong from University of Wollongong, and Prof. CHEN Zhongqiangfrom China University of Geosciences (Wuhan) has compiled a global Permian？Triassic trace-fossil database. The research aims to give a comprehensive review of long-term ichnodiversity and ichnodisparity changes following the EPME, and assess how infaunal organisms behaved in response to the extinction crisis and during the biotic recovery intervals. The results have been published online in the GSA Bulletin, an international comprehensive geology journal. The study, led by Dr. LUO Mao, has depicted the global ichnodiversity and ichnodisparity change from late Permian to Middle Triassic comprising twelve time slices. Importantly, they found that global ichnodiversity and ichnodisparity maintained their pre-extinction level after the end-Permian mass extinction. In particular, late Permian global ichnodiversity and ichnodisparity maintained their level until the Griesbachian, followed by a sharp loss in the Dienerian stage. This result in diversity of trace fossils is in contrast to that of body fossils. A further analysis of the tiering composition of ichnogenera from each time slices showed that Early Triassic trace fossils are dominated by shallower tiered ichnogenera when compared with pre- and post-extinction trace fossil compositions. Furthermore, such difference in tier composition is statistically obvious. Dr. LUO Mao and his collaborators interpreted that such global ichnodiversity change might have be a taphonomic effect caused by the wide-spread occurrence of microbial mat substrate during the Early Triassic. The development of firm substrates enhanced by microbial mat enveloping, aiding the preservation of shallow-tiered trace fossils, and maintaining the high ichnodiversity level in the earliest Triassic. The dataset, and the ichnodiversity trends revealed by Dr. LUO Mao and his collaborators suggested that the high ichnodiversity and ichnodisparity in the earliest Triassic is best explained as a taphonomic artifact. The sustained high ichnodiversity in the Griesbachian, combined with the preferential occurrence of shallow-tier bioturbation structures suggests limited mixing of seafloor sediments, which have drawn parallels with substrate conditions proposed for Ediacaran-Fortunian strata. The research has been jointed supported by the Strategic Priority Research Program of Chinese Academy of Sciences, the CAS Talents Program, and the National Natural Science Foundation of China. Reference: Luo, M*., Buatois, L.A., Shi, G.R., Chen, Z.Q., 2020. Infaunal response during the end-Permian mass extinction. https://doi.org/10.1130/B35524.1. Line chart diagram summarizing variation in global ichnodiversity (a) and ichnodisparity (b) in comparison with the global generic richness of body fossils (c) Change in ichnofossil tiering levels from late Permian to Middle Triassic expressed as area plots Box plots comparing the percentage of different tiering groups between Early Triassic and pre- (late Permian) and post-extinction (Middle Triassic) intervals General trend of relative abundance of microbialites in the Lower–Middle Triassic
Trace fossils, as behavioural records of organisms in the geological past, have been proved useful in deciphering the mechanisms and timing of biotic recovery after mass extinctions. In many cases, trace fossils record the behaviours of soft-bodied organisms that have null to very limited preservation potential in the fossil record. They often provide significant ecologic information on ancient communities not available from the study of body fossils. Trace fossils, as behavioural records of organisms in the geological past, have been proved useful in deciphering the mechanisms and timing of biotic recovery after mass extinctions. In many cases, trace fossils record the behaviours of soft-bodied organisms that have null to very limited preservation potential in the fossil record. They often provide significant ecologic information on ancient communities not available from the study of body fossils. More and more ichnologists focused on ichnological records during mass extinctions and subsequent biotic recovery intervals, with numerous studies emphasizing ichnological proxies as indicators of biotic recovery process after the latest Permian, when the the end-Permian mass extinction (EPME) has caused the highest biodiversity loss coupled with the most profound ecological impact in Phanerozoic Earth history. The vast majority of ichnological studies have focused on elucidating the timing and patterns of ecosystem recovery after the EPME, leading to the establishment of various ichnological parameters (e.g., ichnodiversity, bioturbation indices, bedding plane bioturbation indices, burrow sizes, tiering, trace-fossil complexity) as proxies for unraveling the pacing and processes of biotic recovery in the Early Triassic. However, some recognitions derived from ichnological studies seem to be inconsistent with those from body fossil observations (prolonged, stepwise recovery versus fast recovery). In addition, there are also cases whereby different ichnologists choose to use different parameters (e.g., ichnofabric indices and bioturbation indices) for documenting the same ichnological features. These discrepancies pose a need to critically evaluate current and popular ichnological parameters and the scopes of their applicability. Recently, Dr. LUO Mao from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) in collaboration with Prof. SHI Guangrong from University of Wollongong (Australia), Prof. Buatois from University of Saskatchewan (Canada), and Prof. CHEN Zhongqiang from China University of Geoscience (Wuhan) presented a critical review on the use of various ichnological parameters as relative proxies for unravelling ecosystem recovery after the EPME in order to place them on more solid theoretical grounds. In their study, the significance and caveats of various ichnological parameters and their limitations are clarified and discussed in detail, in the hope that these proxies will be more appropriately used in the future studies dealing with mass extinctions and biotic recoveries. Related research results has been published online in the comprehensive geology journal Earth-Science Reviews. According to Dr. LUO Mao, ichnodiversity, ichnodisparity, burrow sizes are good indicators of biotic recovery, while bedding plane bioturbation indices remain to be explored further as various studies suggest that on bedding planes, trace-fossil distribution can be heterogeneous on a scale of meters to decimeters. In terms of tiering, the composition of the different tiers (e.g., shallow, intermediate, and deep tier) should be reconstructed rather than only considering the penetration depth of burrows. Further, it is worth noting that evaluating the benthic ecospace occupation and ecosystem engineering through the analysis of trace fossils would be a promising approach. Based on current ichnological studies from the Permian-Triassic interval and researchers own observations, Dr. LUO Mao and his collaborators have reached several main recognitions for biotic recovery after the end-Permian mass extinction. These are: (1) Distribution of varying oxic conditions results in the disparate patterns of benthic macrofaunal recovery (including trace-making organisms) in the Early Triassic. Such oxic conditions in the shallow-marine ‘habitable zone’ possibly aid a faster recovery of trace-making organisms in the earliest Triassic. (2) The widespread matground-dominated ecosystems could have inhabited a variety of metazoans (including trace makers) during the Earl Triassic recovery interval. (3) Low bioturbation intensities in the Lower Triassic strata may be a reason leading to enhanced pyrite burial and prolonged low sulfate concentrations in the Early Triassic ocean. This research has been supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the CAS Pioneer Hundred Talents Program, and by grants from NSFC. Reference: Luo, M*., Shi, G.R., Buatois, L.A., Chen, Z.Q., 2020. Trace fossils as proxy for biotic recovery after the end-Permian mass extinction: A critical review. Earth-Science Reviews, Volume 203, 103059. Trend of ichnodiversity along a depositional profile (modified from Buatois and Mángano, 2013)
Trend of burrow-size changes for typical ichnotaxa (Planolites, Rhizocorallium, Thalassinoides) from Permian to Middle Triassic (global data) Tiering structure as expressed by the maximum penetration depth and ichnological composition at different sediment depths
Integrated marine geochemical variations and general bioturbation intensity during the Permian-Triassic interval, with geochemical cycling models established for the Late Permian, Early Triassic, and Middle Triassic respectively
Ordovician corals in eastern Australia are mostly confined to the Upper Ordovician series, with the earliest tabulates occurring in strata which span the uppermost Darriwilian (upper Middle Ordovician) to basal Sandbian (lower Upper Ordovician) interval. Recognition of the biostratigraphic utility of coral faunas in the field as an adjunct to mapping Ordovician limestones in NSW led previous authors to propose a series of four coral/stromatoporoid faunas: C/S I–IV from oldest (Eastonian 1, equivalent to latest Sandbian–earliest Katian) to youngest (Bolindian 1–2, or latest Katian). Such a local biostratigraphic framework permits an accurate means of dating field collections in the region, and has also enhanced our understanding of the evolutionary history of corals and stromatoporoids during this time interval. Ordovician corals in eastern Australia are mostly confined to the Upper Ordovician series, with the earliest tabulates occurring in strata which span the uppermost Darriwilian (upper Middle Ordovician) to basal Sandbian (lower Upper Ordovician) interval. Recognition of the biostratigraphic utility of coral faunas in the field as an adjunct to mapping Ordovician limestones in NSW led previous authors to propose a series of four coral/stromatoporoid faunas: C/S I–IV from oldest (Eastonian 1, equivalent to latest Sandbian–earliest Katian) to youngest (Bolindian 1–2, or latest Katian). Such a local biostratigraphic framework permits an accurate means of dating field collections in the region, and has also enhanced our understanding of the evolutionary history of corals and stromatoporoids during this time interval. Corals representing the sole occurrence of C/S Fauna IV of the regional biostratigraphic scheme occur in limestone in the uppermost Malachis Hill Formation of the Bowan Park area, central New South Wales. Though this coral fauna is restricted to a relatively thin limestone band, exposed intermittently for approximately 1.5 km, its significance greatly outweighs this in terms of completing the coral biostratigraphic scheme and also in contributing to the knowledge of the biogeographic relationships of the region in the Late Ordovician. Recently, Dr. WANG Guangxu from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) and his colleagues Ian. G. Percival and ZHEN Yong Yi from Geological Survey of New South Wales described corals from the uppermost Malachis Hill Formation in central NSW. Related research results have been published online in the international geoscience journal Alcheringa. New species described and illustrated from this fauna include the rugosan Bowanophyllum ramosum and tabulate Hemiagetiolites longiseptatus. Also three other distinct species of Hemiagetiolites, H. spinimarginatus (Hall, 1975), H. cf. H. palaeofavositoides (Lin & Chow, 1977) and H. sp., an unnamed species of Paleofavosites, and three heliolitine corals, Heliolites waicunensis Lin & Chow, 1977, Navoites cargoensis (Hill, 1957) and Plasmoporella sp. were documented. These descriptions, which complete knowledge of the entire fauna collected over 50 years, enable interesting conclusions to be drawn regarding palaeogeographic affinities of this youngest in situ Ordovician coral fauna known from eastern Australia. Its remarkable similarities to contemporaneous coral faunas from South Tien Shan and the Chu-Ili Terrane indicate strong connections between eastern Australia and the latter two terranes, supporting their positioning in equatorial latitudes of eastern peri-Gondwana. However, it is puzzling that fewer similarities exist between the eastern Australian coral fauna and those from rocks of Katian age in SE China, which may be due to either a slightly younger age of the former fauna or a relatively higher palaeolatitudinal position of South China. This research was jointly supported by the National Science Foundation of China, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences. Reference: Wang, G. X., Percival, I. G. & Zhen, Y. Y., 2020. The youngest Ordovician (latest Katian) coral fauna from eastern Australia, in the uppermost Malachis Hill Formation of central New South Wales. Alcheringa (https://doi.org/10.1080/03115518.2020.1747540) A new rugose coral Bowanophyllum ramosum documented from the Malachis Hill Formation of central New South Wales, eastern Australia
Cordaitaleans, as close relatives of modern conifers, had a long geological history in the Cathaysia from the Visean (Mississippian, lower Carboniferous) to the end of Permian. They became prominent since the late Pennsylvanian, and best developed during the Cisuralian (early Permian) in North China, serving as the volumetrically dominant to subdominant elements of wetland floras. Architecture and ecology of the Cathaysian cordaitaleans from non-peat-forming environments are poorly known. Cordaitaleans, as close relatives of modern conifers, had a long geological history in the Cathaysia from the Visean (Mississippian, lower Carboniferous) to the end of Permian. They became prominent since the late Pennsylvanian, and best developed during the Cisuralian (early Permian) in North China, serving as the volumetrically dominant to subdominant elements of wetland floras. Architecture and ecology of the Cathaysian cordaitaleans from non-peat-forming environments are poorly known. Dr. WANG Mingli and other researchers from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), recently found 211 giant cordaitalean trunks and described their morphology and brief anatomical features from the Cisuralian Taiyuan Formation in Yangquan, Shanxi Province, North China. This results have been published online in Palaeoworld. It is reported that the discovery of the giant cordaitalean trunks has attracted great attention from the local government, and has been listed as a key protection object by the Yangquan City Planning and Natural Resources Bureau. It is planned to build a fossil remains park and museum on this basis. These trunks are characterized by the Artisia-like pith and pycnoxylic xylem. Absence of growth rings in the logs suggests they grew under non-seasonal humid tropical conditions. They are preserved in sandstone bodies interpreted as deposits of distributary river channels on the delta plain. Several trunks with attached rooting systems indicate that these trees may have been growing on channel levees or delta plains and brought into the channels by lateral bank erosion. Allometric estimates of tree height suggests that the largest trees were up to approximately 43.5 m tall. Mature cordaitaleans with straight trunks were probably the tallest trees and formed the canopy of the riparian forest in North China during the Cisuralian. This study was supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences, the National Natural Science Foundation of China, Youth Innovation Promotion Association CAS and the National Science Foundation. Reference: Wan, M.L., Yang, W., Wan, S., Li, D.D., Zhou, W.M., He, X.Z., Wang, J., 2020. Giant cordaitalean trees in early Permian riparian canopies in North China: Evidence from anatomically preserved trunks in Yangquan, Shanxi Province. Palaeoworld, https://doi.org/10.1016/j.palwor.2020.04.008
Chrono- and lithostratigraphy of the Taiyuan Formation in Yangquan, Qinshui Basin, Shanxi Province, North China(A), in addition to the gross morphology (B-D) and anatomical features (E-H) of the trunks.
Reefs are important marine ecosystems in marine, and an excellent tool for tracking marine ecosystem changes, especially through mass extinction transitions. During the geological history, the earliest marine reef ecosystems were formed of stromatolites and flourished during the Precambrian before declining in the Phanerozoic. Metazoan reefs first appeared in the late Ediacaran and proliferated during the Phanerozoic, albeit with time gaps after mass extinction events, which are often marked by microbial reef proliferation. During the Middle-Late Devonian, the largest area of metazoan (stromatoporoid-coral) reefs of the Phanerozoic occurred, which covered about five million square kilometres (10 times the surface area of modern reef ecosystems). The Late Devonian Frasnian-Famennian (F-F) Kellwasser and the end-Devonian Hangenberg extinctions caused the collapse and disappearance of stromatoporoid-coral ecosystems, respectively. The succeeding Mississippian has long been assumed to be an interval dominated by microbial reefs, and lack of metazoan reefs. Small-sized metazoan reefs gradually reappeared during the middle-late Mississippian (Visean Stage). However, due to low-resolution and limited data available in previous studies, the timing and style of metazoan reef recovery in the Mississippian are unclear. Recently, Dr. YAO Le from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), Dr. Markus Aretz from the University of Toulouse 3, and Prof. Paul, B. Wignall from the University of Leeds, systematically reviewed and documented the reef composition, distribution and evolutionary process from the Late Devonian to Mississippian, and uncovered the re-emergence of the Mississippian coral reef ecosystems after the Late Devonian mass extinctions. Relevant findings were published online on 16th December, 2019 in Earth-Science Reviews. Previous reports of the late Visean coral bioconstructions from the Western Europe and North Africa (western Palaeotethys Ocean), may mark the first metazoan reef proliferation after the Hangenberg extinction. In this study, abundant coral reefs, coral frameworks and coral biostromes were described from the late Visean strata on the South China Block (eastern Palaeotethys Ocean). The occurrence of these coral bioconstructions further suggests that the late Visean coral reef recovery may have been a widespread phenomenon. Based on the high-resolution reef database constructed in this study, three sub-intervals of the Mississippian metazoan reef recovery were distinguished, which are (1) metazoan “reef gap” phase (MRG) without metazoan reefs during the Tournaisian; (2) metazoan reef re-establishment phase (MRR) containing a few metazoan reefs from early Visean to early part of the late Visean; and (3) metazoan reef proliferation phase (MRP) with global coral reef flourishment during the middle part of the late Visean (late Asbian to early Brigantian substages). Coral reef proliferation at this time showed that the Mississippian was not solely a period dominated by microbial reefs. Late Visean coral reef development coincided with increased nektonic and benthic diversity, showing that stable marine ecosystems developed during this time. Even compared with other slow reef-recovery intervals, such as the middle-late Cambrian and Early-Middle Triassic with the intervals until the MRR and MRP of 5 Ma and 2 Ma, and 15 and 9 Ma respectively, the Mississippian metazoan reef recovery was the longest in reef history with about 12 Ma and 23 Ma until the MRR and MRP, respectively. Harsh climatic and oceanic conditions were present during the Mississippian, mainly including the widespread marine anoxia during the middle part of Tournaisian and the following recurrent glacial and interglacial climatic episodes with frequent changes in sea level, sedimentary facies and sea-water surface temperature, which may have stymied metazoan reef recovery during this time. During the late Visean, marine communities flourished during a phase of relative warm conditions and high sea level, and coincided with the long-delayed re-emergence of coral reef ecosystems after the Late Devonian extinctions. This research was supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences, the National Natural Science Foundation of China, and the Natural Science Foundation of Jiangsu Province. Article information：Yao, L*., Aretz, M., Wignall, P.B., Chen, J.T., Vachard, D., Qi, Y.P., Shen S.Z., Wang, X.D., 2019. The longest delay: Re-emergence of coral reef ecosystems after the Late Devonian extinctions. Earth-Science Reviews. DOI: https://doi.org/10.1016/j.earscirev.2019.103060. Composition and evolutionary pattern of the Late Devonian to Mississippian reefs, and their relations to coeval changes in reef builders and palaeoenvironments Field (A-E), polished-slab (F-G) and thin-section photographs of the late Visean (Mississippian) coral reefs in South China
Field photographs of the late Visean coral reefs from other areas, e.g., Morocco (A), England (B-D), Australia (E) and Japan (F)
