Until now, most radiolarian investigations have been undertaken in the eastern and central segments. Less radiolarian studies have been done in the western segment, especially those involving any systematic research on the biostratigraphy and paleobiogeography of the radiolarians. The Yarlung Tsangpo suture zone (YTSZ) marks the collision boundary between the Eurasian Plate and the Indian Plate and remains geological records of the disappeared Neo-Tethyan ocean, which is a hotspot on the study about the Neo-Tethyan ocean evolution and the Qinghai-Tibet Plateau uplift. The YTSZ consists of eastern (Qushui–Motuo), central (Angren–Renbu) and western (Saga to the boundary of India–China) three segments. Until now, most radiolarian investigations have been undertaken in the eastern and central segments. Less radiolarian studies have been done in the western segment, especially those involving any systematic research on the biostratigraphy and paleobiogeography of the radiolarians. In recent years, well-preserved Jurassic-Cretaceous radiolarian fossils have been collected within the western YTSZ by the research group of Prof. LUO Hui from the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences (NIGPAS). Ph.D. candidate CUI Xiaohui and others from this group, cooperating with Prof. Jonathan C. Aitchison from the University of Queensland in Australia, make a detailed analysis of Early Cretaceous (Hauterivian to late Barremian) radiolarians from Jiangyema section in the west segment of the YTSZ. The results have been published in the international geological research journal Cretaceous Research. Two radiolarian zones and two subzones are recognized and respectively named as the Cecrops septemporatus zone, Aurisaturnalis carinatus zone, Aurisaturnalis carinatus carinatus subzone and Aurisaturnalis carinatus perforatus subzone. They can be correlated well with coeval radiolarian biozones between western Tethys and/or Japan, which provide a better biostratigraphical framework and reliable age constraints for parts of the Neo-Tethyan Ocean floor that were subducted beneath supra-subduction zone (SSZ) ophiolites in the western part of the YTSZ. Comparison of geochemical characteristics on discriminant graphs suggests that the bedded cherts were deposited in a deep oceanic basin near a continental margin. These results and integration of available radiolarian studies along the YTSZ suggest that the Neo-Tethys was a deep ocean between the Indian and Eurasian continents in which pelagic sedimentation was on-going until at least late Barremian time. This research was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of Chinese Academy of Sciences and the Second Tibetan Plateau Scientific Expedition and Research. Reference: Cui, X.H., Luo, H., Jonathan C.A., Li, X. Fang, P.Y., 2021. Early Cretaceous radiolarians and chert geochemistry from western Yarlung Tsangpo suture zone in Jiangyema section, Purang county, SW Tibet. Cretaceous Research, 125 104840. https://doi.org/10.1016/j.cretres.2021.104840. Simplified geological map of the Purang ophiolitic melange showing the location of studied section (modified after Liu et al., 2011) Comparison of Early Cretaceous radiolarian zones (modified after Gorican et al., 2018; Li et al., 2017) Scanning electron micrographs of selected radiolarians from siliceous samples in the Jiangyema section (1) Scanning electron micrographs of selected radiolarians from siliceous samples in the Jiangyema section (2)
In recent years, a particular pattern of marl tuffs has attracted increasing attention from geological colleagues and has become one of the major international hot topics. Think of a pattern consisting of two components, in biogenic limestones of deep-time: a) dark-colored ellipsoidal areas of various sizes and shapes, and b) curved light-colored areas filling the space between the ellipses. Is the pattern made of: 1) dark ellipsoidal objects with lightcoloured intervening spaces, or 2) a light-coloured complex curved framework with a dark infilling? This conundrum lies at the heart of the problem of distinguishing clotted micrite from sponges in micritic limestones. In recent years, a particular pattern of marl tuffs has attracted increasing attention from geological colleagues and has become one of the major international hot topics. Think of a pattern consisting of two components, in biogenic limestones of deep-time: a) dark-colored ellipsoidal areas of various sizes and shapes, and b) curved light-colored areas filling the space between the ellipses. Is the pattern made of: 1) dark ellipsoidal objects with lightcoloured intervening spaces, or 2) a light-coloured complex curved framework with a dark infilling? This conundrum lies at the heart of the problem of distinguishing clotted micrite from sponges in micritic limestones. Some curved structures resemble published images of interpreted sponges, raising the question of their nature, relevant to many carbonate studies including reefs and mud mounds throughout the Phanerozoic. A conundrum lies at the heart of the problem of distinguishing clotted micrite from sponges in micritic limestones. Understanding this issue is relevant for many carbonate studies in the Phanerozoic rock record, which include the widespread occurrence of reefs and mud mounds; the interpretations of presence of sponges are not necessarily always justified, affecting assessment of faunal assemblages, sedimentary processes and diagenesis. Recently, Prof. Yue Li and Dr. Qi-jian Li from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) and his collaborators from Brunel University try to demonstrate the issue mentioned above by using material from Early Silurian patch reefs rich in such complex fabrics. The results have been published online in the Sedimentary Record, an open access journal hosted by the International Society for Sedimentary Geology (SEPM). The study describes Early Silurian carbonate reef facies in the Ningqiang Formation containing amalgamated micritic masses, commonly layered, interpreted to have formed by bacterial processes creating clotted fabrics. In most cases, cavity infills comprise fabrics we interpret to be clotted micrite masses, and the layering presumably represents multiple events of infilling of open cavities (Fig. 1), perhaps as microbial micrites. Comparative images of modern lithistid desmas and keratose fibres and show that the size of lithistid desmas is comparable to the curved sparitic features in the Ningqiang Formation sediments, although keratose fibres are much smaller (Fig. 2). The implication of this work is that studies reporting lithistid and keratose sponges in limestones in the Phanerozoic records may warrant careful consideration of the interpretation of presence of sponges, that may have an impact on discussions of sedimentology and diagenesis, and of sponge palaeobiology and evolution. The attempt to identify keratose sponges, using 3D reconstruction that involved destructive grinding, is difficult to achieve, but may be necessary for confirmation. The arguments presented in this study have potential wider implications for the analysis of other carbonate structures, such as mud mounds in Devonian that include fabrics interpreted as sponges. This study was jointly supported by the Youth Innovation Promotion Association of CAS, grants from the Strategic Priority Research Program (B) of CAS and the National Natural Science Foundation of China. Reference: Stephen Kershaw, Qijian Li & Yue Li. 2021. Addressing a Phanerozoic carbonate facies conundrum—sponges or clotted micrite? Evidence from Early Silurian reefs, South China Block. Sedimentary Record, DOI: 10.2110/sedred.2021.1.03. Figure 1．(A) Plane-polarised light (PPL) view of bioturbated wackestone reef fill, with margin of irregular cavity (bottom and left). Large white areas are spar-filled cavities lacking sediment. (B and C) Cross-polarised light (XPL) views of enlargements of the two boxes in (A) showing details of cavity margin and contrast between wackestone reef matrix and amalgamated micritic cavity fills, that are layered. Yellow arrows in (A) and (B) mark the cavity edge. Middle Huashitou reef, Xuanhe, Sichuan Province. Figure 2. (A) View of amalgamated micrite with a second-generation cavity (lower centre) also filled with amalgamated micrite that is partly layered; a smaller round cavity, partly-filled, is shown centre-right. (B) Details of yellow box in (A) emphasising the round mass of sparite that might be a sponge. (C) Modern lithistid sponge desmas in transmitted light; note the difference in scale. (D) Modern keratose sponge fibres, at the same scale as the main picture, from an unidentified sponge, Bahamas.
A recent study on spectacular fossil plants preserved in a volcanic ash fall deposit—known as China’s "vegetational Pompeii,” in Inner Mongolia, China—has resolved a mystery that puzzled palaeontology for over a century: What are Noeggerathiales? A recent study on spectacular fossil plants preserved in a volcanic ash fall deposit—known as China's "vegetational Pompeii," in Inner Mongolia, China—has resolved a mystery that puzzled palaeontology for over a century: What are Noeggerathiales? The study, published in PNAS on March 8, was led by Prof. WANG Jun from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences and by Prof. David Dilcher from Indiana University (USA). Researchers from the UK, Czech Republic and Austria were also involved. The researchers confirmed that Noeggerathiales had the spore propagation mode of ferns and the vascular tissue of seed plants. They belonged to a sister group of seed plants, the former gymnosperm. Noeggerathiales were important peat-forming plants that lived approximately 325-251 million years ago. Although they were first recognized as a distinct plant group in the 1930s, scientists have long argued over their relationships with other plant groups. As a result, they were considered an evolutionary dead end. The researchers studied complete plants preserved in a 66-cm-thick bed of volcanic ash that fell 298 million years ago and smothered all the plants growing in a swamp. The ash prevented the fossils from being consumed by other organisms or decaying and thus preserved many complete individuals. From these complete plants, the scientists reconstructed a new species of Noeggerathiales named Paratingia wuhaia that finally allowed the groups affinity and evolutionary importance to be determined. These results show for the first time that Noeggerathiales were advanced members of the evolutionary lineage from which seed plants evolved. This is important as it shows Noeggerathiales are more closely related to seed plants than they are to other fern groups, and Noeggerathiales can no longer be considered an evolutionary dead end. The study also shows that the ancestral lineage from which seed plants evolved diversified alongside the earliest seed plant radiation during the Devonian, Carboniferous and Permian periods and did not rapidly die out as previously thought. Noeggerathiales are now recognized as an advanced group of –spore plant that evolved complex cone-like structures from modified leaves. Despite their reproductive sophistication, however, they were victims of profound environmental and climate changes during the Permian-Triassic mass extinction approximately 251 million years ago that destroyed swamp ecosystems globally. The "vegetational Pompeii" is certainly a fossil Lagerstatte, preserving a large number of materials that have huge potential for resolving mysteries in the area of palaeobotany. "The whole-plant Paratingia wuhaia reconstructed here represents a tip of the iceberg. The ongoing research based on the fossils from the 'vegetational Pompeii' may bring about more and more reconstruction of ancient plants," said Prof. WANG. The fossil collection from the "vegetational Pompeii" represents the largest number of plant fossils describing a coal-forming forest. Meanwhile, the research group has conducted the largest actual reconstruction of an ancient peat-forming swamp in the world. Reference: Jun Wang, Jason Hilton, Hermann W. Pfefferkorn, Shijun Wang, Yi Zhang, Jiri Bek, Josef Psenicka, Leyla J. Seyfullah, David Dilcher, 2021, Ancient noeggerathialean reveals the seed plant sister group diversified alongside the primary seed plant radiation, PNAS. https://doi.org/10.1073/pnas2013442118. Fig. 1 The type of specimen the new plant is based on, preserving the crown of the tree with leaves and its fertile organs attached to the stem (Image by NIGPAS) Fig. 2 Reconstruction of the peat-forming plant community in which the new species Paratingia wuhaia (yellow arrows) grew (Image by NIGPAS) Contact: LIU Yun, Propagandist Email: yunliu@nigpas.ac.cn Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Nanjing, Jiangsu 210008, China
Reconstructions of ancient sulfur cycling and redox conditions commonly rely on sulfur isotope measurements of sedimentary rocks and minerals. Ediacaran strata (635–541 Ma) record a large range of values in bulk sulfur isotope difference (Δ34S) between carbonate-associated sulfate (δ34SCAS) and sedimentary pyrite (δ34Spy), which has been interpreted as evidence of marine sulfate reservoir size change in space and time. However, bulk δ34Spy measurements could be misleading because pyrite forms under syngenetic, diagenetic, and metamorphic conditions, which differentially affect its isotope signature. Fortunately, these processes also impart recognizable changes in pyrite morphology. Reconstructions of ancient sulfur cycling and redox conditions commonly rely on sulfur isotope measurements of sedimentary rocks and minerals. Ediacaran strata (635–541 Ma) record a large range of values in bulk sulfur isotope difference (Δ34S) between carbonate-associated sulfate (δ34SCAS) and sedimentary pyrite (δ34Spy), which has been interpreted as evidence of marine sulfate reservoir size change in space and time. However, bulk δ34Spy measurements could be misleading because pyrite forms under syngenetic, diagenetic, and metamorphic conditions, which differentially affect its isotope signature. Fortunately, these processes also impart recognizable changes in pyrite morphology. To tease apart the complexity of Ediacaran bulk δ34Spy measurements, Dr. WANG Wei, Dr. GUAN Chengguo and Prof. ZHOU Chuanming from the Nanjing Institute of Geology and Paleaontology, Chinese Academy of Sciences (NIGPAS), with other researchers from the Institute of Geology and Geophysics, CAS (IGGCAS) used scanning electron microscopy and nanoscale secondary ion mass spectrometry to probe the morphology and geochemistry of sedimentary pyrite in an Ediacaran drill core of the South China block. The relevant results were published online in the internationally renowned journal Geology. Pyrite occurs as both framboidal and euhedral to subhedral crystals, which show largely distinct negative and positive δ34Spy values, respectively. Bulk δ34Spy measurements, therefore, reflect mixed signals derived from a combination of syndepositional and diagenetic processes. Whereas euhedral to subhedral crystals originated during diagenesis, the framboids likely formed in a euxinic seawater column or in shallow marine sediment. Although none of the forms of pyrite precisely record seawater chemistry, in situ framboid measurements may provide a more faithful record of the maximum isotope fractionation from seawater sulfate. This study exemplifies the fundamental problem with using bulk analyses of sulfur isotopes for paleoenvironmental reconstruction. Given that sulfate concentration is the main controlling factor for sulfur isotope fractionation, the consistently negative δ34S values in framboidal pyrite are suggestive of a larger Ediacaran sulfate reservoir than previously thought. The study was supported by the National Key Research and Development Program of China, the Chinese Academy of Sciences (CAS), and the National Natural Science Foundation of China. Reference: Wei Wang*, Yongliang Hu, A. Drew Muscente, Huan Cui, Chengguo Guan, Jialong Hao, Chuanming Zhou*, 2021, Revisiting Ediacaran sulfur isotope chemostratigraphy with in situ nanoSIMS analysis of sedimentary pyrite. Geology, v. 49, https://doi.org/10.1130/G48262.1 Fig.1 Profiles of sedimentary pyrite δ34S values in Lantian Formation drill core Fig.2 Dominant pyrite morphologies and in situ nanoSIMS sedimentary pyrite δ34S
Umenocoleidae is one of the most perplexing fossil insect groups. It was first established based on a specimen (Umenocoleus sinuatus Chen et T’an, 1973) from the Lower Cretaceous of Yumen City (Gansu Province, northwestern China). The systematic position of the genus has long been disputed, and it has variously been assigned to stem-group Coleoptera, Protelytroptera, Blattaria, stem-group Dictyoptera, or Mantodea, mainly because its sclerotized forewings and its forewing venation similar to stem-group Coleoptera, some groups of Dictyoptera, and Protelytroptera. Umenocoleidae is one of the most perplexing fossil insect groups. It was first established based on a specimen (Umenocoleus sinuatus Chen et T’an, 1973) from the Lower Cretaceous of Yumen City (Gansu Province, northwestern China). The systematic position of the genus has long been disputed, and it has variously been assigned to stem-group Coleoptera, Protelytroptera, Blattaria, stem-group Dictyoptera, or Mantodea, mainly because its sclerotized forewings and its forewing venation similar to stem-group Coleoptera, some groups of Dictyoptera, and Protelytroptera. Some researchers restricted Umenocoleidae to its type genus Umenocoleus and retransferred it to Coleoptera, proposing the placement of Umenocoleus as sister group to all other beetles, while the other genera remained in Dictyoptera. If it is true, the systematic position of Umenocoleidae will be very important for us to understand the origin and early evolution of Coleoptera. However, the placement of Umenocoleus is still under debate. Recently, Mr. LUO Cihang, a postgraduate student, supervised by Prof. WANG Bo and Prof. ZHANG Haichun come from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), studied new specimens from the type horizon of the type locality (Lower Cretaceous Zhonggou Formation at Jiuquan, Yumen City, China). The result indicates that the Umenocoleidae is likely a specialized taxon of Dictyoptera, sister to Alienoptera. The beetle-like appearance is a result of convergent evolution. This research was published on Palaeoworld. The research group described three new specimens from the type horizon of the type locality (Lower Cretaceous Zhonggou Formation of Yumen City, China), one of the type species, and two forewings of Ponopterix, a genus potentially closely related to Umenocoleus. They also re-examined the forewings of U. nervosus from the Lower Cretaceous Dalazi Formation, and two additional species (Enervipraeala nigra Luo, Xu et Jarzembowski, 2021, and another based on one undescribed specimen) preserved in mid-Cretaceous Kachin amber. The results revealed that though cup-shaped punctures on the forewings of Umenocoleidae are superficially similar to the window punctures of stem-group Coleoptera and extant Archostemata, their micro-structure are different. The researchers also carried out a phylogenetic analysis based on a matrix with 72 characters and 36 terminals, which provided robust evidence that the Umenocoleidae is a specialized taxon of Dictyoptera, sister to Alienoptera. Menocoleidae was a successful globally distributed family during the Early Cretaceous but had never been discovered from the Late Cretaceous, which probably accompanied by the decline of gymnosperms and in competition with wood-associated polyphagan beetles. Umenocoleidae (and also Alienopteridae) were apparently a failed attempt of roachoids to occupy a new microhabitat. This research was jointly funded by the Strategic Priority Research Program of the Chinese Academy of Sciences, the Second Tibetan Plateau Scientific Expedition and Research, and National Natural Science Foundation of China.Mr. Yan Fang and Ms. Chun-Zhao Wang of NIGPAS were acknowledged for their help with the SEM analysis. Reference:Luo, C.-H., Beutel, R.G., Thomson, U.R., Zheng, D.-R., Li, J.-H., Zhao, X.-Y., Zhang, H.-C., Wang, B., 2021. Beetle or roach: systematic position of the enigmatic Umenocoleidae based on new material from Zhonggou Formation in Jiuquan, Northwest China, and a morphocladistic analysis. Palaeoworld. https://doi.org/10.1016/j.palwor.2021.01.003 Fig. 1. Photographs and line drawings of Umenocoleidae Fig. 2. Systematic position and distribution of the Umenocoleidae Fig. 3. Ecological reconstruction of Umenocoleidae (drawing by Jahao Li) Contact: LIU Yun, Propagandist Email: yunliu@nigpas.ac.cn Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Nanjing, Jiangsu 210008, China
Although the Cretaceous is considered to have been a period with a warm-hot, greenhouse climate (Huber et al., 2002; O'Brien et al., 2017), Earth's climate during the Cretaceous underwent significant changes from a very warm mid-Cretaceous greenhouse climate to a long-term cooling period during the latest Cretaceous (Dhondt and Arthur, 1996; Linnert et al., 2018). Although the Cretaceous is considered to have been a period with a warm-hot, greenhouse climate (Huber et al., 2002; O'Brien et al., 2017), Earth's climate during the Cretaceous underwent significant changes from a very warm mid-Cretaceous greenhouse climate to a long-term cooling period during the latest Cretaceous (Dhondt and Arthur, 1996; Linnert et al., 2018). During the late Campanian–Maastrichtian, several major biotic events occurred, and a variable global greenhouse climate was established (Barrera, 1994; Macleod, 1994; Nordt et al., 2003; Wilf et al., 2003; Voigt et al., 2010; Jung et al., 2012). The Campanian–Maastrichtian Boundary Event (CMBE) represents a cooling phase registered in the δ18O values extracted from shells of planktonic and benthic foraminifera (Barrera, 1994). It was characterized by a negative δ13Ccarb excursion in bulk carbonates (Voigt et al., 2010), lasting ~1.6 Myr in the Campanian–Maastrichtian transition (ca. 72.1–70.5 Ma; Jung et al., 2012). The simultaneous biotic changes included the extinction of inoceramid bivalves at high latitudes (Johnson and Kauffman, 1990; Macleod and Huber, 1996), widespread changes of phytoplankton communities and expansion of cool water taxa (Linnert et al., 2016; Dameron et al., 2017), and the diversity of angiosperms declined abruptly in North American (Johnson, 1992). The Mid-Maastrichtian Event (MME) (ca. 69 Ma according to Frank et al., 2005) was first recognized because of the global extinction of inoceramid bivalves (MacLeod, 1994). The MME was marked by high atmospheric pCO2 on land (Wilf et al., 2003), an increase in ocean temperatures (Jung et al., 2013), and a positive carbon isotope excursion (Voigt et al., 2012). This warming trend has been found in the western Central Pacific (Jung et al., 2013) and South Atlantic (Li and Keller, 1999). The biotic changes included an abrupt disappearance of rudist reefs (Johnson and Kauffman, 1990), the extinction of a long-ranging, widespread group of bottom-dwelling inoceramids at low latitudes (Macleod, 1994; Macleod and Huber, 1996; Bralower et al., 2002; Dameron et al., 2017), and an increase in the diversity and abundance of ammonites in Antarctica (Witts et al., 2015). The latest Maastrichtian warming event (which took place during the last 450–110 kyr before the K/Pg boundary, Cretaceous/Paleogene boundary, according to Li and Keller, 1999) has been detected in marine and terrestrial systems, based on studies of oxygen isotopes of foraminifera in the South Atlantic (Li and Keller, 1999), leaf margin analysis used to estimate temperatures in North Dakota, USA (Wilf et al., 2003), and the estimation of atmospheric CO2 from pedogenic carbonate nodules in Texas, USA (Nordt et al., 2003). During this warming period, the planktonic foraminifera underwent a part of extinction, with the proliferation of opportunist disaster species and dwarfism (Abramovich and Keller, 2003; Abramovich et al., 2010), the major acme of the warm-water species of calcareous nannofossils were found in the Tropical Pacific, with a lowering of fertility levels and a drop of species richness (Thibault and Gardin, 2010), and the land plants in North Dakota became abundant and diversified (Wilf and Johnson, 2004). However, few studies have focused on the response of aquatic biotas to these significant global climate changes during the Late Cretaceous, and no terrestrial biotic response has previously been reported in the CMBE and MME due to the lack of continuous non-marine sequences rich in fossils. Dr. LI Sha, Prof. WANG Qifei and Prof. ZHANG Haichun, from the ‘Modern terrestrial ecosystem origin and early evolution’ at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), collaborated with Dr. Josep Sanjuan, from American University of Beirut-AUB, and Prof. WAN Xiaoqiao, from China University of Geosciences, Beijing, studied the response of the lacustrine flora in East Asia to global climate changes across the K/Pg boundary. This research was recently published on Global and Planetary Change. The global climate during the latest Cretaceous became variable, with several global warming and cooling trends in a context of a greenhouse Earth. The responses of marine ecosystems to these climate events are relatively well known worldwide; however, lacustrine responses are poorly known due to the less frequent and discontinuous terrestrial fossil records. The relative changes in charophyte diversity in continuous lacustrine sedimentary sequences from two basins in East Asia, i.e., Songliao and Jiaolai, are considered here for the first time to establish their correlation with global climate changes during the Late Cretaceous and K/Pg boundary, compared with the well-studied south European Ibero-Armorican Island. Lacustrine deposits correlated with the Campanian–Maastrichtian Boundary Event (CMBE), related to a long cooling period provided a relatively low diversity in East Asia. In contrast, we detected a diverse charophyte flora in lacustrine deposits correlated with the Mid-Maastrichtian Event (MME) in East Asia in a global warming trend. A higher charophyte diversity was further found in the End-Cretaceous global warming event due to speciation under the background of latest Maastrichtian warming event (LMWE). During the LMWE, Characeae species such as Microchara cristata reduced its size significantly due to environmental stress probably related to the Deccan volcanism. On the other hand, a general tendency of increasing the gyrogonite size in new Characeae taxa has been detected in populations extracted from lower Danian deposits, probably related to stable palaeoenvironmental conditions in a global cooling context. This study represents the first attempt to correlate the response of the charophyte flora to global climate changes in permanent lacustrine systems during the three main Late Cretaceous–early Danian climatic turnovers. This study was jointly funded by the National Natural Science Foundation of China, and Strategic Priority Pre-Research Program (B) of the Chinese Academy of Sciences. Reference: Li, S., Sanjuan, J., Wang, Q.F., Zhang, H.C., Wan, X.Q., 2021. Response of the lacustrine flora in East Asia to global climate changes across the K/Pg boundary. Global and Planetary Change, 197, 103400. https://doi.org/10.1016/j.gloplacha.2020.103400. Fig. 1. Stratigraphic log of the SK-1(N) borehole showing the position (modified after Li et al., 2019) and diversity of charophytes correlated with temperatures calculated based on paleosol carbonate clumped isotopes (Zhang et al., 2018), oxygen isotopes of benthic and planktonic foraminifera (Li and Keller, 1999), leaf-margin analysis (Wilf et al., 2003) and paleosol carbonate oxygen isotopes (Nordt et al., 2003). Abbreviations: CMBE, Campanian–Maastrichtian Boundary Event; MME: Mid-Maastrichtian Event; LMWE: latest Maastrichtian warming event. Fig. 2. Comprehensive terrestrial responses of the charophyte flora, the palynological flora, seed cones and the ostracod fauna to global climate events, such as speciation and the dwarfing effect, and size changes on a large time scale. Contact: LIU Yun, Propagandist Email: yunliu@nigpas.ac.cn Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Nanjing, Jiangsu 210008, China <!--[if supportFields]> ADDIN EN.REFLIST <![endif]--><!--[if supportFields]><![endif]-->
The Permian–Triassic transition witnessed the largest mass extinction event in Earth’s history, multiple mechanisms have been proposed to explain the cause of this catastrophe, however, relatively less attention has been paid to the paleogeography and major element chemistry of seawater and its possible link to mass extinction during this interval. Syndepositional massive marine dolostones could record the Mg isotope signature of contemporaneous seawater that hold clues of ancient Mg cycling. The Permian–Triassic transition witnessed the largest mass extinction event in Earth’s history, multiple mechanisms have been proposed to explain the cause of this catastrophe, however, relatively less attention has been paid to the paleogeography and major element chemistry of seawater and its possible link to mass extinction during this interval. Syndepositional massive marine dolostones could record the Mg isotope signature of contemporaneous seawater that hold clues of ancient Mg cycling. Recently, an international research team from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), Nanjing University and University of Innsbruck investigated Mg isotopes of dolomite from three widely spaced carbonate sections in the Paleotethys to trace oceanic Mg cycling during this critical period. The research results were published in the international journal Earth and Planetary Science Letters. They found remarkable variation of δ26Mgdolomite values around the End-Permian extinction interval and anti-correlated with global perturbations in δ13Ccarbonate recorded from different localities in the Paleotethys. Generally, the dolomite δ26Mg values displayed a first-order increase from -2.1±0.1‰ at the end Permian to -1.6±0.2‰ in the early Triassic. Based on the high-precision temporal model, our results suggest that the δ26Mg of seawater fluctuated by 0.4‰ within ~750 kyr across the Permian–Triassic transition. Modeling reveals that the high rate of change in δ26Mgseawater is attributed to dramatically intensified dolomitization in a restricted oceanic environment. The restriction could have occurred to local basins that were separated from each other, however, our data are also consistent with a hypothesis of the Paleotethys Ocean being episodically separated from the Panthalassa Ocean around the Permian-Triassic transition. The restriction events within the Paleotethys Ocean could have significantly weakened the ocean’s buffering capacity against external disturbances, and exacerbated marine environmental crisis to the marine ecosystem. This work was supported by the Strategic Priority Research Program of Chinese Academy of Sciences, the National Natural Science Foundation of China and the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences. Reference: Hu, Z., Li, W.*, Zhang, H.*, Krainer, K., Zheng, Q.-f., Xia, Z., Hu, W., Shen, S.-z., 2021. Mg isotope evidence for restriction events within the Paleotethys ocean around the Permian-Triassic transition. Earth and Planetary Science Letters 556, 116704. DOI: 10.1016/j.epsl.2020.116704. Fig1. Global paleogeography at ～252 Ma and the location of studied sections, Lithological and C-Mg isotopic variations of carbonates along the studied sections in Paleotethys. Fig2. A comparison dolomite δ26Mg from end Permian to early Triassic for the western and eastern Paleotethys. Contact: LIU Yun, Propagandist Email: yunliu@nigpas.ac.cn Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Nanjing, Jiangsu 210008, China
Previous studies have shown that the eukaryotic radiation continued from the Ediacaran Period to the Cambrian explosion, with when and how the earliest Ediacaran acanthomorphs occurred and diversified remaining not fully discussed, hampering our understanding to the initiation of the first global radiation of eukaryotes in Earth history. After more than one billion years of evolution and extreme conditions of the Neoproterozoic global glaciations, eukaryotic life began to thrive and diversify globally in the Ediacaran Period. This event initiated from the wide occurrence and diversification of the Ediacaran acanthomorphic acritarchs and multicellular algae. Previous studies have shown that the eukaryotic radiation continued from the Ediacaran Period to the Cambrian explosion, with when and how the earliest Ediacaran acanthomorphs occurred and diversified remaining not fully discussed, hampering our understanding to the initiation of the first global radiation of eukaryotes in Earth history. To resolve those problems, researchers from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences(NIGPAS), collaborating with researchers from the Virginia Tech., USA, have been working on the fossiliferous Ediacaran Doushantuo Formation in South China for decades, and one of their studies was published recently on Precambrian Research. Based on 1547 acanthomorphic acritarch specimens from the Doushantuo Formation at 3 sections, this work identified 24 genera and 69 species, including two new genera, six new species, five unnamed species, and three possible new forms tentatively placed in open nomenclatures, and discussed the temporal and spatial distribution of acanthomorphic acritarchs of the Doushantuo Formation, as well as implications for Ediacaran biostratigraphy. This paper reported acanthomorphs from the lowest chert nodule horizon of the Doushantuo Formation, with considerably high diversity, indicating a possible earlier appearance of these eukaryotic organisms, which has not been captured in the fossil record due to the lack of proper taphonomic conditions below this horizon. This finding also indicates that the First Appearance Data (FAD) of any acanthomorphic acritarch from this lowest chert nodule horizon in basal Member II may not serve as a good criterion for the base of the Second Ediacaran Stage (SES), thus other geological records are needed in searching for the basal boundary of SES. Upsection, altogether 21 species occurred within the 20 m strata above the cap dolostone, exceeding half of the total number of species (65.6%) from Member II of the Doushantuo Formation at Jiulongwan. Based on published cyclostratigraphic data, these results show that Ediacaran acanthomorphs diversified rapidly, reaching a considerably high diversity within about 10 Myrs after the end of Marinoan glaciation. In addition, combined with published acritarch data, this study discussed problems relating with biostratigraphic data from "composite sections", which had been widely used in previous studies, and proposed some regionally traceable taxa for future biostratigraphic studies of the Doushantuo Formation. This study was supported by the National Key R & D Program of China, National Natural Science Foundation of China, the Strategic Priority Research Program (B) of Chinese Academy of Sciences, and the U. S. National Science Foundation. Reference: Ouyang, Q., Zhou, C., Xiao, S., Guan, C., Chen, Z., Yuan, X., Sun, Y., 2021. Distribution of Ediacaran acanthomorphic acritarchs in the lower Doushantuo Formation of the Yangtze Gorges area, South China: Evolutionary and stratigraphic implications. Precambrian Research 353, 106005. https://doi.org/10.1016/j.precamres.2020.106005.
Newly erected genus and species Crassimembrana crispans gen. et sp. nov. and a new form Crassimembrana cf. C. crispans
Emended species Weissiella brevis emend. in this study
First appearance data (FADs) of some regionally traceable acanthomorph taxa in Member II from the Yangtze Gorges area
The surface and deep waters of the Philippine Sea flow into the South China Sea(SCS), and the Intermediate Water of the SCS into the Philippine Sea through the Luzon Strait, which shows a vertical "sandwich" structure from the surface to the bottom in the northeastern SCS. The studies about Benthic foraminferal and ostracodal have disclosed the late Pleistocene evolution of the deep water mass and ventilation in the SCS, which have provided important information of the paleo-environment. However, on the long-term scale, few dada was acquired from the SCS deep-water, especially for the water mass history before the final formation of the modern tectonic structure during the Miocene. During International Ocean Discovery Program (IODP) Expedition 367/368 in the northern SCS, the remarkable rhythmic reddish-brown and greenish-gray sediments were found during the Middle-Late Micoene, which provide valuable material to study the deep water property and its exchange with those of the Pacific Ocean. Professor LI Baohua from Nanjing institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), Dr. JIN Xiaobo, Professor LIU Chuanlian and others from Tongji University conducted experiments on the 442-497m sediment at site U1502 (water depth 3764m) through dealing with the sediment color reflectance, nannofossil composition, key element content, and clay minerals to determine the origin of these cyclicity-like color transitions during the late Miocene. The above result was recently published in Marine Geology: It is inferred that the in-situ formed amorphous hematite caused the coloration of the reddish sediments, in which ferrum and manganese contents were high and carbonate was not poorly preserved. Therefore, the occurrence of the cyclicity-like color transitions reflects the extent of deep-water ventilation in the abyssal SCS. Such changes in deep-water ventilation were possibly related to an orbital-forced rearrangement of deep oceanic circulation in the Pacific Ocean. A well-ventilated bottom water and less- preserved carbonate in these reddish sediments was proposed to be contributed by the stronger mixing of the northern- and southern-sourced deep-water during the interglacial period. While, during the glacial period, when the Antarctic ice sheet expanded, the formation of the Antarctic deep-water was enhanced and resulted in a more isolated and intensified deep stratification of the abyssal water masses in the SCS, forming the green colored sediments. This study also provides important informations on the formation, evolution and environmental influence of the SCS. This study was supported by the National Natural Science Foundation of China, the National Science and Technology Major Project of the Ministry of Science and Technology of China, and the Strategic Priority Research Program of the Chinese Academy of Sciences. Reference: Jin, Xiaobo, Xu, Juan, Li, Yanli, Qiao, Peijun, Wu, Li, Ling, Cheng, Li, Baohua*, Liu, Chuanlian*, 2020. Origin of the rhythmic reddish-brown and greenish-gray sediments in the abyssal South China Sea: Implications for oceanic circulation in the late Miocene. 430: 106378. https://doi.org/10.1016/j.margeo.2020.106378. Manganese and ferrum contents, magnetic susceptibility and sediment color reflectance a* at Site U1502A Schematic deep-water ventilation in the (SCS) and the Pacific deep oceanic circulation during the glacial/interglacial cycles
The opening of Drake and Tasmania passages, the closures of the Central American isthmus and Indonesia sea way, and shutdown and reopening of the Gibraltar Straight played important role on the global ocean circulation and further influence the climate system and environment. After the Strait of Gibraltar re-opened at 5.33 million years ago, warm high-salinity Mediterranean outflow water (MOW) showered into the Gulf of Cadiz, north Atlantic, penetrating north along the Portuguese slope, even to the Norwegian- Greenland Sea region, which enhances the North Atlantic deep-water density and helps drive Atlantic Meridional Overturning Circulation (AMOC). The opening of Drake and Tasmania passages, the closures of the Central American isthmus and Indonesia sea way, and shutdown and reopening of the Gibraltar Straight played important role on the global ocean circulation and further influence the climate system and environment. After the Strait of Gibraltar re-opened at 5.33 million years ago, warm high-salinity Mediterranean outflow water (MOW) showered into the Gulf of Cadiz, north Atlantic, penetrating north along the Portuguese slope, even to the Norwegian- Greenland Sea region, which enhances the North Atlantic deep-water density and helps drive Atlantic Meridional Overturning Circulation (AMOC). Foraminiferal fauna contains the rich information of the surrounding water, and responses sensitively to the environmental changes. The benthic foraminifera has the priority on the bottom water reconstruction. In collaboration with scientists form Portugal and Korea, Dr. GUO Qimei of Professor LI BaohuaI’s research group at Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences(NIGPAS) performed the paleoceanographic analyses on Integrated Ocean Drilling Program (IODP) Site U1391 off the Portuguese margin based on benthic foraminifera and stable Oxygen/ Carbon isotopes of their tests. The above result was recently published in Quaternary Science Reviews. The study reports the faunal composition and variation of benthic foraminifera during the last 1.3 Ma. Based on the high-resolution δ18O stratigraphy, “Elevated Epibenthos” group and Key species Planulina ariminensis contents of benthic foraminifera, the MOW dynamics across the middle Pleistocene transition (MPT) was reconstructed. The data suggests that the MOW intensity has typical glacial-interglacial cycles, an active MOW current during the interglacial periods and a sluggish MOW current during the glacial periods. The strength of MOW was enhanced during MISs 1, 9-11, 19-21, and 37-39, reaching the lately peak at MIS 11, when the sea level was considered to rise up to ~20 m above the present high-stand. The variation in the abundance of the “elevated epibenthos” group was dominated by ~41-kyr cycle prior to the MPT and by the ~100-kyr cycle after the MPT, which suggested there was an MPT-related shift in the MOW dynamics. The MOW variability of the last 1.3 Ma is the combination of the precession forcing and the obliquity forcing that work together. The precession forcing played an important role in the MOW dynamics of the entire time series, which explains the ~20-kyr high frequency oscillations in the “elevated epibenthos” record. The bottom water was well ventilated by MOW during the interglacial periods and by GNAIW during the glacial periods, and poorly ventilated during the glacial terminations. The study also delineates the partial evolution of Mediterranean outflow water after the reopening of the Gibraltar Straight. This work was supported by the Chinese Academy of Sciences (CAS) Strategic Priority Project, National Natural Science Foundation of China, the State Key Laboratory of Palaeobiology and Stratigraphy, and the Ministry of Ocean and Fisheries Korea (International Ocean Discovery Program) and IODP-China. Reference: Guo, Qimei*, Li, Baohua*, Voelker, Antje, Kim, Jin-Kyoung, 2020. Mediterranean Outflow Water dynamics across the middle Pleistocene transition based on a 1.3 million-year benthic foraminiferal record off the Portuguese margin. Quaternary Science Reviews, 247: 106567. https://doi.org/10.1016/j.quascirev.2020.106567. Guo, Qimei, Li, Baohua*, Kim, Jin-Kyoung, IODP Expedition 339 Scientists, 2017. Benthic foraminiferal assemblages and bottom water evolution off the Portuguese margin since the Middle Pleistocene. Global and Planetary Change, 150: 94-108. http://dx.doi.org/10.1016/j.gloplacha.2016.11.004. Contact: LIU Yun, Propagandist Email: yunliu@nigpas.ac.cn Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Nanjing, Jiangsu 210008, China General circulation pattern of the present Mediterranean Outflow Water (MOW) pathway in the eastern North Atlantic Scanning electron microscope pictures of the elevated epi-benthic foraminifera from Site U1391 Variation of the “Elevated Epibenthos” at Site U1391 during the last 1.3 Ma, its comparison with global oxygen stable isotope curve (LR04), local insolation and other paleoceanographic index
