From Late Cretaceous to early Tertiary in eastern China, a large number of inland saline oil and gas basins developed, such as Shengli Oilfield, Zhongyuan Oilfield, Jiangsu Oilfield and Jianghan Oilfield. Since the discovery of marine calcium algae and ostracod fossils in Shengli Oilfield in 1979, whether marine transgression has occurred in eastern China has become the focus of petroleum academic debate. The horizon where transgression occurs often enriches evaporite and main source rock. Therefore, this problem has caused academic debate for more than 40 years. From Late Cretaceous to early Tertiary in eastern China, a large number of inland saline oil and gas basins developed, such as Shengli Oilfield, Zhongyuan Oilfield, Jiangsu Oilfield and Jianghan Oilfield. Since the discovery of marine calcium algae and ostracod fossils in Shengli Oilfield in 1979, whether marine transgression has occurred in eastern China has become the focus of petroleum academic debate. The horizon where transgression occurs often enriches evaporite and main source rock. Therefore, this problem has caused academic debate for more than 40 years. Among them, Professor HE Chengquan from Nanjing Institute of Geology and paleontology, Chinese Academy of Sciences (NIGPAS), thinks that some dinoflagellate fossils from Shengli oil field in Bohai Bay Basin are marine origin, and they appear in the transgressive sediments in western Xinjiang at the same time. While according to the geochemical analysis of marine geologists from TongJi University, the strontium isotopic compositions of calcareous nannofossil shells are obviously higher than that of the same period of seawater, indicating that these organisms lived in inland salt lake environment which is obviously different from that of seawater. Seawater intrusion can occur in a short period of time, which is difficult to preserve in geological records. Salt deposits can record very short-term geological events in geological history. In order to solve this puzzle, Associate Professor MENG Fanwei, of Nanjing Institute of Geology and paleontology, Chinese Academy of Sciences (NIGPAS), cooperated with Professor NI Pei of Nanjing University and Dr. Galamay of Ukrainian Academy of Sciences to conduct a preliminary study on the drilling of Jintan Salt Mine in Jiangsu Province, China. In the lower part of salt deposit in the Jintan basin, the brine composition in the fluid inclusion is similar to the seawater in the same period, while the brine component in the upper part of the salt deposit is gradually transformed into the inland salt lake component. The research results have been published in Marine and Petroleum Geology online, a well-known international academic journal in the field of petroleum geology. This discovery strongly supports the view that transgression exists in eastern China. However, due to the influence of inland environment after seawater intrusion, the sedimentary environment of "marine source continental facies" has been formed, and the composition of brine has changed greatly. This discovery not only solves the long-standing controversy in the petroleum field of China, but also provides a theoretical basis for the correct evaluation of source rocks from Late Cretaceous to early Tertiary in oil and gas fields in eastern China. The research was supported by the China Israel cooperation project of NSFC and the original innovation project "from 0 to 1". Reference: Fan-wei Meng, Anatoliy R. Galamay, Pei Ni, Naveed Ahsan, Saif Ur Rehman, Composition of middle-late Eocene salt lakes in the Jintan Basin of eastern China: Evidence of marine transgressions, Marine and Petroleum Geology, Volume 122, 2020, 104644, https://www.sciencedirect.com/science/article/pii/S026481722030427X Photomicrographs showing primary fluid inclusion banding in hopper halite from the Jintan Basin Results and comparative analysis of fluid inclusions in the Eocene non-marine halite (our data) with modern seawater (McCaffrey et al., 1987), marine Eocene halite (after Ayora et al., 1994) on a Janecke diagram (after Valyashko, 1962)
Ediacara-type organisms are an assemblage of macroscopic, soft-bodied eukaryotes that are prosperous in the late Ediacaran (~571–539 Ma). They constitute a unique macroscopic fossil biota prior to the Cambrian explosion—the Ediacara biota, representing a landmark in the evolution of early macroscopic organisms. Ediacara-type organisms are an assemblage of macroscopic, soft-bodied eukaryotes that are prosperous in the late Ediacaran (~571–539 Ma). They constitute a unique macroscopic fossil biota prior to the Cambrian explosion—the Ediacara biota, representing a landmark in the evolution of early macroscopic organisms. Probably there is nothing as enigmatic as the iconic frondose fossils in the Ediacara biota. A typical frondose fossil consists of an upright leaf-like body (petalodium), a connecting stem, and a basal attachment disc. Frondose fossils are widespread and abundant in the Ediacara biota. However, due to their simple external morphology and preservation without internal anatomical information, such information about their phylogenetic affinities still limited. Early researchers interpreted them as early pennatula phosphorea according to the similarity of their overall morphology, but ontogenetic and phylogenetic evidence has rejected this hypothesis. Recent studies suggest that these frondose fossils might represent crown- or total-groups of the Metazoa. In 2014, a type of frondose fossil—Charniodiscus was reported from the Shibantan biota (i.e., the Shibantan assemblage of the Ediacara biota) in the Ediacaran Dengying Formation, Yangtze Gorges area, Hubei, China. However, recent studies have revealed that the type species of Charniodiscus is a frondose fossil with fractal branching and multiple petalodia. Hence, it is questionable to place the frondose fossils from the Yangtze Gorges area in Charniodiscus. Lately, PhD candidate WANG Xiaopeng, Assoc. Prof. PANG Ke, and Prof. CHEN Zhe et al. from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) and Prof. XIAO Shuhai from Virginia Tech scrutinized and revised a major group of frondose fossils from the Shibantan biota. Related results have been published online in Journal of Paleontology recently (free open access). The study shows that the morphological of the frondose fossils from the Yangtze Gorges area are more similar to Arborea which is a bi-petaloid frondose fossil without fractal branching pattern, rather than the type species of Charniodiscus. As a result, the researchers placed these fronds into Arborea. They identified four species of Arborea from the Shibantan biota, including the type species Arborea arborea, Arborea denticulata new species, and two unnamed species, Arborea sp. A and Arborea sp. B. Biometric and principle component analysis were also conducted, and these results showed that Charniodiscus sp. from the Bonavista Peninsula, Newfoundland, Canada is indistinguishable from Arborea arborea. Therefore, they are synonymized. This research also shows that frondose fossils still have a high diversity even in the latest Ediacaran, providing important evidence for understanding the evolution during the transition between the Ediacaran and Cambrian. The Shibantan Member in South China and the Khatyspyt Formation in Arctic Siberia represent the only two carbonate successions that are known to host morphologically complex, soft-bodied Ediacara-type macrofossils. This study also includes taphonomic analysis and a model to explain the preservation mechanism of Arborea. authigenic calcite might have played an important taphonomic role in the preservation of Arborea from the Shibantan biota. This research was supported by the Chinese Academy of Sciences, the National Natural Science Foundation of China, the Chinese Ministry of Science and Technology, the Science Foundation of Jiangsu Province of China, and the State Key Laboratory of Palaeobiology and Stratigraphy. Reference: Wang, X., Pang, K.*, Chen, Z.*, Wan, B., Xiao, S., Zhou, C., Yuan, X., 2020. The Ediacaran frondose fossil Arborea from the Shibantan limestone of South China. Journal of Paleontology, in press. DOI: 10.1017/jpa.2020.1043. Arborea deticulata n. sp. from the Shibantan biota Arborea arborea from the Shibantan biota Arborea sp. A (1-4) and Arborea sp. B (5-6) from the Shibantan biota Petrographic observations and proposed preservation mechanism of Arborea
As enigmatic stem-group euarthropods and some of the earliest apex predators, the radiodonts are iconic animals of the Cambrian Explosion. Distinctive features of this group include a head with a pair of frontal appendages and a radial oral cone, and a trunk with swimming flaps and setal structures. As one of the two main lineages of radiodonts, the hurdiids are characterized by a tripartite cephalic carapace composed of a dorsal central element and paired lateral elements, a pair of frontal appendages bearing elongate blade-shaped endites and a tetraradial oral cone. As enigmatic stem-group euarthropods and some of the earliest apex predators, the radiodonts are iconic animals of the Cambrian Explosion. Distinctive features of this group include a head with a pair of frontal appendages and a radial oral cone, and a trunk with swimming flaps and setal structures. As one of the two main lineages of radiodonts, the hurdiids are characterized by a tripartite cephalic carapace composed of a dorsal central element and paired lateral elements, a pair of frontal appendages bearing elongate blade-shaped endites and a tetraradial oral cone. Our understanding of the morphological and ecological diversity of hurdiids has greatly improved in recent years, which has revealed the important roles of hurdiids in the complex Cambrian ecosystems. Although the Hurdiidae has a cosmopolitan distribution in the Cambrian, their Miaolingian occurrences are restricted to Laurentia and the knowledge of their diversity during this time has potentially been biased and incomplete. Recently, leading by Prof. ZHAO Fangchen, postgraduate SUN Zhixin and Dr. ZENG Han from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) described two hurdiid genera from the middle Cambrian at Shandong province, which represent the first discoveries of hurdiid radiodonts in North China. Relevant results have been published in the journals Palaeogeography, Palaeoclimatology, Palaeoecology and Journal of Paleontology. Cordaticaris striatus gen. et sp. nov. was collected from the middle Cambrian (Miaolingian, Drumian) Zhangxia Formation in Linyi City, Shandong Province. This new taxon is characterized by a heart-shaped central element with linear ornament, frontal appendages equipped with nine blade-like endites including seven subequal elongate endites, a node-bearing ‘peytoia’-type oral cone, and a trunk covered with rows of setal structures. Cordaticaris not only enriches the taxonomic diversity of Hurdiidae, but also further exhibits the great morphological disparity of hurdiids. The discovery of soft-bodied fossils in the Zhangxia Formation also stresses the great potential of the Miaolingian strata of North China for the preservation of non-biomineralized organisms. Cambroraster, first discovered from the Burgess Shale in 2019, is readily distinguishable from other hurdiid taxa by its central head sclerite with deep posterior notches, a rounded anterior margin, and posterolateral processes bearing multiple spines. New specimens of Cambroraster were collected from the Upper Shale Member of the Mantou Formation (uppermost Wuliuan) in Weifang City, Shandong Province. This discovery suggests that Cambroraster had dispersed over a wide biogeographic range, and indicates that the Upper Shale Member of the Mantou Formation is a promising Burgess Shale-type Lagerstatte. This work is financially supported by the Strategic Priority Research Program (B) of Chinese Academy of Sciences, National Natural Science Foundation of China, Jiangsu Basic Research Project, and the State Key Laboratory of Palaeobiology and Stratigraphy. Reference: Sun, Z.X., Zeng, H., Zhao, F.C.*, 2020. A new middle Cambrian radiodont from North China: implications for morphological disparity and spatial distribution of hurdiids. Palaeogeography. Palaeoclimatology, Palaeoecology 558:109947. https://doi.org/10.1016/j.palaeo.2020.109947. Sun, Z.X., Zeng, H., Zhao, F.C.*, 2020. Occurrence of the hurdiid radiodont Cambroraster in the middle Cambrian (Wuliuan) Mantou Formation of North China. Journal of Paleontology, https://doi.org/10.1017/jpa.2020.21. The central element and oral cone of Cordaticaris striatus, and stratigraphic and paleogeographic distribution of hurdiid radiodonts Artistic reconstruction of Cordaticaris striatus on the Cambrian sea（Image Credit: Joschua Knüppe） Cambroraster cf. falcatus from the Cambrian (Miaolingian, Wuliuan) Upper Shale Member, Mantou Formation in Weifang City, Shandong Province, North China, and the dorsal (left) view and ventral (right) view of a Cambroraster model
The Baoshan region (Sibumasu Terrane) of Yunnan Province, SW China, is one of the best locations to study the Wenlock to Pridoli conodonts in China. Conodont fauna of the “Lichaiba” and Niushiping formations were preliminarily reported during the IGCP 591 Field Meeting in 2014. The Baoshan region (Sibumasu Terrane) of Yunnan Province, SW China, is one of the best locations to study the Wenlock to Pridoli conodonts in China. Conodont fauna of the "Lichaiba" and Niushiping formations were preliminarily reported during the IGCP 591 Field Meeting in 2014. Recently, a more detailed analysis of conodont collections from the Silurian strata of the Laojianshan section in the Baoshan region was carried out by Dr. CHEN Zhongyang, Prof. WANG Chengyuan and their colleagues from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), together with Dr. Peep Mannik from Tallinn University of Technology. A revised dating of the section is provided based on the conodont biostratigraphy. The results have been published online in Geological Journal. In stratigraphically ascending order, the Pterospathodus amorphognathoides amorphognathoides Zonal Group, the Pterospathodus pennatus procerus Superbiozone, the Ozarkodina sagitta sagitta Biozone, the Kockelella ortus absidata Biozone, the Kockelella crassa Biozone, the Polygnathoides siluricus Biozone and the "Ozarkodina" eosteinhornensis s.l. Interval Biozone were recognized. Several landslides were also recognized, especially two major landslides which cover the base of the "Lichaiba" and Niushiping formations respectively. The conodont faunas recovered indicate that the "Lichaiba Formation" corresponds to the upper Telychian–upper Wenlock, and the Niushiping Formation to the Ludlow–Pridoli. Part of the Ireviken Event, that is, from Datum 3 to Datum 4 can be recognized from the studied section. The late Telychian conodont fauna from the Laojianshan section is characteristic of distal, open-shelf depositional environments. This research was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Science and Technology Major Project of China, the State Key Laboratory of Palaeobiology and the Eesti Teadusagentuur. This is also a contribution to the IGCP Project 652 'Reading geologic time in Paleozoic sedimentary rocks'. Reference: Chen, Z.Y., Mannik, P., Wang, C.Y.*, Fang, X., Chen, T.E., Ma, X., Zhang, Y.D., Silurian conodont biostratigraphy of the Laojianshan section, Baoshan, Yunnan Province, SW China. Geological Journal. https://doi.org/10.1002/gj.3813 Range chart of conodont species from the Laojianshan section Conodonts from the "Lichaiba" Formation
Among the earliest fossil ants known, haidomyrmecine ‘hell ants’ from Cretaceous amber reveal an ancient and dramatic early burst radiation of adaptive forms. These eusocial Cretaceous taxa diverged from extant lineages prior to the most recent common ancestor of all living ants and possessed bizarre scythe-like mouthparts along with a striking array of horn-like cephalic projections. Despite the morphological breadth of the fifteen thousand known extant ant species, phenotypic syndromes found in the Cretaceous are without parallel and the evolutionary drivers of extinct diversity are unknown. Among the earliest fossil ants known, haidomyrmecine ‘hell ants’ from Cretaceous amber reveal an ancient and dramatic early burst radiation of adaptive forms. These eusocial Cretaceous taxa diverged from extant lineages prior to the most recent common ancestor of all living ants and possessed bizarre scythe-like mouthparts along with a striking array of horn-like cephalic projections. Despite the morphological breadth of the fifteen thousand known extant ant species, phenotypic syndromes found in the Cretaceous are without parallel and the evolutionary drivers of extinct diversity are unknown. Now, an international research group from U.S., France, and China has proposed a mechanistic explanation for aberrant hell ant morphology, and thus providing new insight into the evolution of hell ants. The research was co-led by Prof. WANG Bo from the Nanjing Institute of Geology and Palaeontology (NIGPAS) of the Chinese Academy of Sciences. Results were published in Current Biology on August 6. The researchers have provided a mechanistic explanation for aberrant hell ant morphology through phylogenetic reconstruction and comparative methods, as well as a newly reported specimen. They reported a remarkable instance of fossilized predation that provides direct evidence for the function of dorsoventrally-expanded mandibles and elaborate horns. These findings confirmed the hypothesis that hell ants captured other arthropods between mandible and horn in a manner that could only be achieved by articulating their mouthparts in an axial plane perpendicular to that of modern ants. The head capsule and mandibles of haidomyrmecines are uniquely integrated as a consequence of this predatory mode and covary across species while finding no evidence of such modular integration in extant ant groups. The results of this study suggest an extinct early burst adaptive radiation into morphospace that is unoccupied by any living taxon, triggered by an innovation in mouthpart movement and subsequent modular covariation between mandible and horn. The new results also suggest that hell ant cephalic integration – analogous to the vertebrate skull – triggered a pathway for an ancient adaptive radiation and expansion into morphospace unoccupied by any living taxon. Reference: Barden P.*, Perrichot V.*, Wang Bo* (2020) Specialized predation drives aberrant morphological integration and diversity in the earliest ants. Current Biology. https://doi.org/10.1016/j.cub.2020.06.106. Reconstructions of haidomyrmecine hell ants Phylogeny and cephalic homology of hell ants and modern lineages Morphospace and evolutionary integration of living and Cretaceous ants
Known as the third pole of the earth, the magnificent Qinghai-Xizang plateau used to be a vast ocean millions of years ago and its vicissitudes have become one of the hotspots of the geological research. Stratigraphy is the basis for diachronic reconstruction of this process, with biostratigraphy the most fundamental method and fossils often the most reliable evidence for the age of strata. However, due to extreme natural conditions and intense tectonic deformation and metamorphism, fossil collection and biostratigraphic research in the Qinghai-Xizang plateau are very difficult and the progress has been very slow. The Neo-Tethys realm in southern Xizang, as represented by the Yarlung Zangbo Suture Zone, is such a prominent sample where the Mesozoic and Cenozoic strata bear many problems and arguments, which has already become a restrict to other researches. Known as the third pole of the earth, the magnificent Qinghai-Xizang plateau used to be a vast ocean millions of years ago and its vicissitudes have become one of the hotspots of the geological research. Stratigraphy is the basis for diachronic reconstruction of this process, with biostratigraphy the most fundamental method and fossils often the most reliable evidence for the age of strata. However, due to extreme natural conditions and intense tectonic deformation and metamorphism, fossil collection and biostratigraphic research in the Qinghai-Xizang plateau are very difficult and the progress has been very slow. The Neo-Tethys realm in southern Xizang, as represented by the Yarlung Zangbo Suture Zone, is such a prominent sample where the Mesozoic and Cenozoic strata bear many problems and arguments, which has already become a restrict to other researches. Recently, Professor LI Jianguo and his colleagues from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) established a new integrated biostratigraphic framework for the Triassic–Paleogene strata in Neo-Tethyan realm in southern Xizang based on a combination of their own material and progress and other previous researches. The results have been published online in the Journal of Asian Earth Sciences, an international comprehensive journal of geology. Many blanks in biostratigraphy got filled in this framework and much progress has been made for fossils that were never or weakly studied in the past, particularly microfossils such as conodonts, radiolarians, and miospores. For those well-studied fossils, essential supplement or improvement has been made. The new framework is improved by a series of new biostratigraphic zones, many of which are well correlated with the international standard, such as those of Lower Triassic conodonts and ammonites, uppermost Triassic–Lower Jurassic ammonites, and Upper Cretaceous planktonic foraminifers and calcareous nanofossils. A total of four integrated biostratigraphic charts are compiled in units of period, all consisting of key fossils for stratigraphic division and correlation of that period, such as ammonites, conodonts, bivalves, radiolarians, foraminifers and calcareous nanofossils. Based on these biostratigraphic advances, the authors also discussed and clarified some questions or arguments on the definition, division, correlation and age of some Triassic to Paleogene strata in southern Xizang. The duration of the new integrated biostratigraphic framework is roughly the time that the Neo-Tethys Ocean evolved from its opening by the rifting of Lhasa-Gondese block from the northern margin of Gondwana to its closure as a consequence of the Indian–Eurasian collision. In this respect, this research will provide as an important stratigraphic reference for the study of the evolution of Neo-Tethys and other geological researches on the Qinghai-Xizang Plateau. The relevant research was supported by the Second Tibetan Plateau Scientific Expedition and Research, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences and the National Natural Science Foundation of China. Reference: Jianguo Li*, Miaoqin Lin, Yixiao Wu, Hui Luo, Jungang Peng, Lin Mu, Bo Xu, Chao Zhang, 2020. New biostratigraphic framework for the Triassic–Paleogene in the Neo-Tethys realm of southern Xizang (Tibet), China. Journal of Asian Earth Sciences, https://doi.org/10.1016/j.jseaes.2020.104369. The new integrated biostratigraphic charts of the Triassic-Paleogene strata in the studied area
Reefs are the most complicated and diverse ecosystems in the ocean, with highest levels of species diversity, habitat diversity, community structure and functional diversity. Therefore, they represent one of the most significant genetic treasures in the evolution of Earth life. Metazoan reef ecosystem reached its Phanerozoic acme in Givetian (Middle Devonian), however, detailed studies on the reef biodiversity, ecological interactions and community composition of Givetian reefs are still lacking, limiting our further understanding of the palaeobiodiversity change pattern and evolutionary model of reef ecosystem in critical geological time intervals. Reefs are the most complicated and diverse ecosystems in the ocean, with highest levels of species diversity, habitat diversity, community structure and functional diversity. Therefore, they represent one of the most significant genetic treasures in the evolution of Earth life. Metazoan reef ecosystem reached its Phanerozoic acme in Givetian (Middle Devonian), however, detailed studies on the reef biodiversity, ecological interactions and community composition of Givetian reefs are still lacking, limiting our further understanding of the palaeobiodiversity change pattern and evolutionary model of reef ecosystem in critical geological time intervals. Recently, a systematic study of the Givetian reef biodiversity was carried out by an international research group led by Assoc. Profs. QIE Wenkun and LIANG Kun, Mater HUANG Jiayuan from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), and collaborators from Brunel University, Guizhou University and Wuhan Center of Geological Survey, China Geological Survey. Related paper has been published online in Palaeogeography, Palaeoclimatology, Palaeoecology. The team focuses on the detailed palaeontological and palaeoecological analysis of a Givetian reef located in Dushan Formation, Dahekou section, Guizhou Province, South China. In this study, 665 samples were collected in-situ in 7 m2 by 28 quadrats (50í50 cm) of the vertical reef outcrop, with 2804 thin sections being made and 10823 fossils being described. Detailed statistics of biodiversity and community paleoecology were carried out based on these large amounts of systematic data. As so far, a total of 83 species belonging to 44 genera of 8 phyla were identified within 7 m2 of the Jiwozhai patch reef, including rugose corals (29 species, 9 genera), stromatoporoids (16 species, 10 genera), tabulate corals (13 species, 9 genera), brachiopods (16 species, 8 genera), Bryozoans (4 species, 4 genera), calcified cyanobacteria (3 species, 3 genera), chaetetids (1 species, 1 genera) and tubeworms (1 species, 1 genera). Among them, stromatoporoids (N=755), tabulate corals (N=630), rugose corals (N=198) and chaetetids (N=144) are the most common organisms. Consistent with the densely distributed species at Jiwozhai, complex ecological relationships, including extensive encrustations (N=716), spatial competition (N=35) and symbiosis (N=58) have also been found among different organisms. The in-situ collection of fossils and the sketch of the reef outcrop with high density clarify the spatial distribution characteristics of the reef organisms in Middle Devonian, which shows the stability of the spatial distribution of the main reef-building organisms while the discrepancy between the secondary reef-building organisms and the reef-dwelling organisms. This study would provide important reference for the further correlation of global paleogeography and interpretation of the evolution and distribution patterns of the reef diversity during geological time. This work is financially supported by the Strategic Priority Research Program (B) of Chinese Academy of Sciences, National Natural Science Foundation of China and Geological Survey Projects of China Geological Survey. Reference: Huang, J., Liang, K.*, Wang, Y., Liao, W., Guo, W., Kershaw, S., Jeon, J., Qiao, L., Song, J., Ma, J., Li, Y., Tu, B., Tian, Y., Wang, Y., Wang, Y., Ma, J., Luo, M., Qie, W.*, 2020. The Jiwozhai patch reef: A palaeobiodiversity hotspot in middle Givetian (Devonian) of South China. Palaeogeography, Palaeoclimatology, Palaeoecology, https://doi.org/10.1016/j.palaeo.2020.109895 The Givetian Jiwozhai patch reef of Middle Devonian in Dushan, Guizhou Stromatoporoids and chaetetids in the Jiwozhai patch reef Biotic interactions among the reef organisms in the Jiwozhai patch reef Statistics of biodiversity and abundance (Frequency) of Jiwozhai reef
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
