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... Limestone samples were processed by dilute acetic acid (10%) (Jiang et al., 2007), mudstone samples were cracked by dithionite solution and hydrogen peroxide, and siliceous mudstone samples were dissolved by dilute hydrofluoric acid (5%). LST-an inorganic heavy liquid was used in conodont separation as described by Yuan et al. (2015). Fifteen species belonging to three genera (Clarkina, Hindeodus and Isarcicella) of conodont P1 elements were identified (1 553 from the Zhuqiao Section and 91 from the Shiligou Section), and some key species are illustrated in Plates 1 to 4. ...
... The excursion shows a negative excursion trend form the C. meishanensis Zone to I. isarcica Zone with the average -0.75‰. The δ 13 Ccarb values are variable around the PTB, and can not be compared with the Meishan Section (Shen et al., 2013;Xie et al., 2007) and other section in South China (Yuan et al., 2015;Shen et al., 2013), which is difficult to explain. It seems there are some noises of the carbon isotope excursion at the PTB of Zhuqiao, the carbonate dolomitization is obvious near the PTB of Zhuqiao Section (Fig. 3b), the carbonate dolomitization maybe one possible explanation. ...
Deep-water facies sections have advantages of recording complete information across the Permian-Triassic boundary (PTB). Here we present a detailed study on the conodont biostratigraphy and carbon isotope profile ranges from the Wuchiapingian-Changhsingian boundary (WCB) to the PTB of two deep-water facies sections at Zhuqiao and Shiligou in the Middle Yangtze region, western Hubei, South China. Fifteen species and three genera are identified. Eight conodont zones are recognized, in ascending order, they are the Clarkina orientalis, C. wangi, C. subcarinata, C. changxingensis, C. yini, C. meishanensis, Hindeodus parvus and Isarcicella isarcica zones. The onset of deposition of the deep-water siliceous strata of the Dalong Formation in western Hubei began in the Late Wuchiapingian and persisted to the Late Changhsingian. Carbon isotope negative excursions occur near both the WCB and PTB in both sections. The WCB δ¹³Ccarb negative excursion is in the C. orientalis and C. wangi zones. The PTB δ13Ccarb negative excursion began in the C. yini Zone and extended to the I. isarcica Zone. The absence of several Changhsingian zones may indicate the difficulty of extracting conodonts from siliceous strata or the presence of an intra-Changhsingian hiatus.
... The samples were crushed into small pieces and processed in a 10% solution of acetic acid. The process of extracting conodonts is detailed in Jiang et al. (2019) and Yuan, Jiang & Wang (2015). Six samples of the Madoupo section yielded conodonts (Table 2), but only five of the samples (MDP7, MDP8, MDP10, MDP12 and MDP25) yielded identifiable P 1 elements and these show a Color Alteration Index (CAI) of 1-1.5. ...
The Sevatian of the late Norian is one of the key intervals in biotic turnover and in changes of paleoclimate and paleoenvironments. Conodont faunas recovered from two sections of upper Norian strata of the Dashuitang and Nanshuba formations near Baoshan City in western Yunnan province provide new insights into the diversity and biostratigraphy of the Sevatian conodonts within China as well as globally. A lower Mockina ( M .) bidentata Zone and an upper Parvigondolella ( P .) andrusovi Zone are identified in this area according to the first occurrences of M. bidentata and of P. andrusovi . Rich conodont fauna of M. zapfei is detailed and presents various intraspecific forms. A total of 19 forms of P 1 elements are presented, which, when combined with the reported conodonts in the M. bidentata Zone, suggest that there was a peak in conodont diversity within the M. bidentata Zone. A biotic crisis in the uppermost M. bidentata Zone is recognized from the contrast between the diverse conodont fauna in the M. bidentata Zone and the rare conodonts in the P. andrusovi Zone. The conodont turnover during the middle Sevatian highlights the fact that the prolonged phases of the end-Triassic mass extinction probably began in the transition interval from M. bidentata Zone to P. andrusovi Zone.
... Then the residuals were sieved between 20-mesh and 160-mesh sieves and dried. After heavy liquid (2.80 g/cm 3 ) treatment (Jiang et al., 2004;Yuan et al., 2015b), conodont specimens were selected under the binocular microscope. Conodonts were photographed by Scanning Electron Microscopy (SEM) at China University of Geosciences (Beijing). ...
This study presents an integrated conodont succession from the Bozhou section, northern Guizhou Province, southwestern China. These conodonts were yielded from the Changhsingian Changhsing Formation and the Lower Triassic Yelang and Maocaopu Formations, which were deposited in the transitional setting between the clastic shelf and carbonate platform in the western margin of the Yangtze Platform. A total of 22 conodont species of six genera are identified, and 10 conodont zones are recognized from the top part of Changhsing Formation to the Yelang Formation, namely, the Clarkina changxingensis, C. yini, C. meishanensis, Hindeodus praeparvus, H. parvus, H. postparvus, Neoclarkina discreta, Sweetospathodus kummeli, Neospathodus dieneri, and Eurygnathodus costatus Zones in ascending order. Based on the conodont succession, the ages of Shabaowan, Yulongshan, and Jiujitan members of the Yelang Formation are recognized for the first time and assigned to the early Griesbachian, late Griesbachian, and latest Griesbachian to early Smithian. At this section, the Permian–Triassic boundary (PTB) is placed at the base of Bed 7–2, 10 cm below the top of Changhsing Formation, defined by the first occurrence (FO) of H. parvus. The Induan–Olenekian boundary (IOB) is drawn at the base of Bed 49–1, the uppermost part of Yelang Formation, based on the FO of Eu. costatus immediately overlying the Ns. dieneri Zone in the absence of Novispathodus waageni. The Bozhou conodont successions can be correlated well with other sections worldwide.
... All the samples were crushed into pieces of approximately 2-3 cm 3 and processed with 10% dilute acetic acid to dissolve carbonate. The acid-insoluble residues were carefully collected, and were density separated using lithium heteropolytungstate (a water-miscible, nontoxic, highdensity and inorganic heavy liquid for conodont separation) (Yuan et al., 2015). Initially, sample processing was intended to recover isolated conodonts to investigate the conodont biostratigraphy, but picking under stereomicroscopy recovered many fused clusters of elements. ...
Almost all aspects of conodont research rely on a sound taxonomy based on comparative analysis. This is founded on hypotheses of homology which ultimately rest on knowledge of the location of elements in the apparatus. Natural assemblages—fossils that preserve the articulated remains of the conodont skeletal apparatus—provide our only direct evidence for element location, but very few are known from the Late Triassic. Here we describe fused clusters (natural assemblages) from the late Norian limestone beds of the Nanshuba Formation in Baoshan, Yunnan Province, southwestern China. Recurrent arrangements and juxtaposition of S and M elements in multiple clusters reveal the composition of the apparatus of Mockina and, probably, Parvigondolella. They indicate that these taxa had a standard 15 elements ozarkodinid apparatus, and provide new insights into the morphology of the elements occupying the P2, M and S locations of the apparatus. The apparatus comprised a single alate (hibbardelliform) S0 element, paired breviform digyrate (grodelliform) S1 and (enantiognathiform) S2 elements, paired bipennate (hindeodelliform) S3 and S4 elements, paired breviform digyrate (cypridodellifrom) M elements, paired, modified-angulate P2 elements (with reduced or lacking ‘posterior’ process) and segminiplanate (mockiniform and parvigondolelliform) P1 elements. Our results will allow testing of the hypothesis that Mockina, Parvigondolella and Misikella—critical taxa in Late Triassic biostratigraphy—are closely related and possessed morphologically similar elements in homologous locations.
... Conodont samples were dissolved in a 10% solution of acetic acid. The residues were then separated using an LST-an inorganic heavy liquid (Yuan et al., 2015). Afterwards, the conodonts were collected using a stereoscopic binocular microscope and photographed using a scanning electron microscope (SEM). ...
Based on a study of 49 conodont and 57 geochemical samples from the Upper Triassic, carbonate-dominated Dengdengqiao Formation, Qinling Basin, China, the Carnian conodonts and carbon isotope records are first reported. Two genera and four species have been identified amongst 87 conodont elements: Mosherella praebudaensis, Mo. longnanensis sp. nov., Mo. sp., and “Misikella” longidentata. The presence of Mo. praebudaensis indicates that the lower part (bed 2) of the formation is attributable to the Julian (lower Carnian) substage. A radiolarian fauna identified in a previous study belongs to the upper Carnian, but the sampling horizon is unclear. The δ13Ccarb curve shows a ∼1.8‰ negative excursion beginning from upper part of bed 3, but its stratigraphic location is uncertain. The Dengdengqiao Formation is clearly at least partly of Carnian age but could include younger strata. The abundant calcareous algae at the section is probably due to some transport rather than preserved in site. The unusual ecosystem with rare marine organisms may reflect long-term stressful and unfavorable conditions at Dengdengqiao.
... Samples (each weighing > 5 kg) for obtaining conodonts were collected from the Guanyinya section (53 samples) and the Qingyangou section (13 samples). After dissolving in 10% acetic acid, the residues of these samples were separated using the LST heavy liquid method (Yuan et al., 2015) for collecting conodonts. A total of 627 conodonts are obtained from the 53 conodont samples of the Guanyinya section. ...
The Mid-Carnian Pluvial Episode (or “Carnian Wet Intermezzo”) interrupted the generally arid climate of the Triassic in different regions. An enhanced high-resolution time scale, especially with intercalibrated ammonoid, conodont and magnetic polarity zones, is required to understand the global coincidence of regional manifestations of this climatic change and possible causation factors. The termination of oolite-rich limestones and the initial influx of terrigenous debris at the Unit 1 to Unit 2 boundary in the Guanyinya and Qingyangou sections from Hanwang of the Sichuan Province, South China, are interpreted as a local shift from arid to humid climate. A detailed conodont sampling assigns this facies change to within the Mazzaella carnica range zone of the late Julian substage. Therefore, the conodont markers imply it is coeval with the onset of the mid-Carnian “ Rheingraben Event” at the Rappoltstein reference section in southern Germany; and ammonoids in that section enable correlation to the beginning of a negative carbon-isotope excursion that coincides with the termination of the Yangtze Platform at the Longchang reference section in Guizhou, South China. The first occurrence of Parapetella? guanyinensis sp. nov. is very close to the onset of the interpreted Carnian Pluvial Episode at Hanwang and to the cessation of widespread shallow-water carbonate facies in South China. In contrast to this “Intermezzo” episode in the West Tethys region, arid conditions did not resume in South China in the Eastern Tethys until long after the termination of this wet climate in late Julian.
... All samples were broken into fragments then dissolved in dilute acetic acid (10%) and a 2.80-2.82 g/mL heavy liquid solution (solution of lithium heteropolytungstates in water) was used to separate the conodonts from the residues (method see Yuan et al., 2015). In total 2 626 conodont elements belonging to Hindeodus, Isarcicella and Clarkina were obtained. ...
Two Permian-Triassic boundary (PTB) sections (Pojue and Dala) are well exposed in an isolated carbonate platform (Napo Platform) on the southwestern margin of the Nanpanjiang Basin, South China. These sections provide an insight into the transition across the PTB and a detailed investigation of the conodont biostratigraphy and inorganic carbon isotopes is presented. The PTB at the Pojue Section is placed at the base of Bed 10B (a dolomitized mudstone found below a microbialite horizon), defined by the first occurrence of Hindeodus parvus. At the Dala Section, four conodont zones occur. They are, in ascending order, the Hindeodus parvus Zone, Isarcicella staeschei Zone, Isarcicella isarcica Zone and Clarkina planata Zone. Comparison with the Pojue Section suggests the PTB at Dala also occurs at the base of dolomitized mudstone below a microbialite horizon, although the first occurrence of Hindeodus parvus is near the top of a microbialite bed: an occurrence that is also seen in other platform sections. The succeeding microbialite beds developed during the ongoing PTB mass extinction phase. This time was characterized by low carbon isotope values, and a microbialite ecosystem that provided a refuge for selected groups (bivalves, ostracods and microgastropods) that were likely tolerant of extremely high temperatures.
... All samples were broken into fragments then dissolved in dilute acetic acid (10%) and a 2.80-2.82 g/mL heavy liquid solution (solution of lithium heteropolytungstates in water) was used to separate the conodonts from the residues (method see Yuan et al., 2015). In total 2 626 conodont elements belonging to Hindeodus, Isarcicella and Clarkina were obtained. ...
As a marine microfossil with a long-lasting fossil record stretching from the Cambrian to the Triassic, the tiny conodont plays an important role for the study of the end-Permian mass extinction. In the past few decades, numerous studies on Permian-Triassic conodonts have been published. This paper summarizes the progress made on high-resolution conodont biostratigraphy, timing of the mass extinction across the Permian-Triassic Boundary, conodont apparatus and phylogeny, conodont size variation, conodont oxygen isotope as well as other isotopes and chemical elements. Finally, future perspectives are also discussed.
... The residue was wet sieved and dried at room temperature. Heavy liquid (lithium and sodium heteropolytungstates solution, 2.80 g/cm 3 , Yuan et al., 2015) was used for heavy liquid fractionation of residuals. A total of 1074 conodont elements are obtained and 446 elements can be used for taxonomic identification. ...
The subdivision of Ladinian and Carnian strata in Guizhou, South China has been a matter of intense debate because of the paucity of age-diagnostic faunas. Here we have carried out a detailed conodont biostratigraphic investigation on the Yangliujing, Zhuganpo and Wayao formations in the Yongyue section of western Guizhou Province. Conodonts are only prolific in the Zhuganpo and Wayao formations. Three genera and twenty species are identified, including two new species Quadralella wanlanensis n. sp. and Quadralella yongyueensis n. sp. They represent a rather endemic fauna of latest Ladinian to early Carnian age. Four conodont zones are established. They are, in the ascending order, the Paragondolella foliata, Quadralella polygnathiformis, Quadralella tadpole, and Quadralella aff. praelindae zones. Thus in the study area, the Zhuganpo Formation is generally of early Carnian (Julian 1) age whilst the Wayao Formation probably extends from the Julian 2 into the late Carnian (Tuvalian substage). The Ladinian–Carnian boundary (LCB) cannot be precisely defined due to the absence of the ammonoid Daxatina Canadensis and the paucity of conodonts. However, the LCB is unlikely lower than the Yangliujing–Zhuganpo formation contact. The Julian 1–Julian 2 (early Carnian) substages boundary is defined in the uppermost Zhuganpo Formation by the occurrence of basal Julian 2 ammonoid Austrotrachyceras ex gr. A. austriacum and is also evidenced by the disappearance of most short-range Julian 1 conodonts in the overlying Wayao Formation.
... 50-m-thick oolitic limestone in the Guanyinya (HWG) Section in Hanwang, Mianzhu to isolate conodonts. The limestone samples were dissolved in 10% acetic acid and then conodonts were separated by LST (solution of lithium heteropolytungstates in water) heavy liquid (method of Yuan et al., 2015). The conodonts were photographed with the Scanning Electron Microscope (SEM) at State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan). ...
Upper Triassic (Carnian) marine successions in the northwestern margin of Upper Yangtze Region (Sichuan Basin, China) show a lithological change from grey oolitic into a sponge-mound limestone (Units 1 and 2 of the lower member of the Ma'antang Formation), then overlain by greyish black to dark grey sandy shale and siltstone (Units 3 and 4 of the upper member of the Ma'antang Formation). Siliceous sponge mounds were built by Hexactinellida, and this succession was examined in three localities: Jushui section in Anxian (JS), and Guanyinya (HWG) and Qingyangou sections (HWQ) in Hanwang, Mianzhu. The conodont Quadralella polygnathiformis confirms a Carnian age for the biolithite and oolitic limestone of the lower Ma'antang Formation. Abundant ammonoids identified as belonging to the Discotropitid and Juvavitid families suggest a Tuvalian 1 (early Late Carnian) age for the lowermost part of the greyish black sandy shale that overlies the sponge mound at the Jushui Section. Field investigations and microfacies analysis suggest that sponge mounds had two stages of growth in relatively deeper water with low energy. The first sponge-growth mound stage ended in a regional karstified omission surface, and was followed by a sudden increase of siliciclastic input. Greyish black shales containing plant fossils cover a second Upper Carnian sponge mound stage, which is mainly recorded in HWG. The onset of these shales may be related to the Carnian Pluvial Phase (CPP) documented in the western Tethys region (e.g., in Italy, Austria and Hungary). The demise of the sponge mounds at all three sections may have been triggered by the joint effect of climatic changes associated with the fresh water input caused by CPP and with a relative sea-level change caused by local tectonic movements in the course of the Indosinian orogeny.
... Each sample was crushed into fragments and dissolved in 10% acetic acid. The slag samples were separated in new-type inorganic heavy liquid LST (solution of lithium heteropolytungstates in water) by the methods of Yuan et al. (2015a). In total, 608 conodont P 1 elements were obtained (Table 1), from which 16 species belonging to 7 genera (Plates 1-9) were identified (Table 2); the distributions of the species are illustrated in Fig. 2. ...
A sequence of successive conodont datums and zones for the Cisuralian and Guadalupian series for the South China region of the Equatorial Warm Water Province is proposed based on the Shaiwa section, Ziyun, Guizhou. The seven conodont zones in ascending order are: Sweetognathus aff. whitei Zone of Artinskian Stage, a set of three new Kungurian zones of Sweetognathus guizhouensis Zone, Sweetognathus subsymmetricus Zone, Mesogondolella nashuiensis Zone; the Mesogondolella idahoensis lamberti Zone of uppermost Kungurian, the Guadalupian zones of Jinogondolella aserrata followed by Jinogondolella postserrata. The base of the Kungurian Stage is tentatively defined by the first occurrence of S. guizhouensis, 174.5 m above the base of the Sidazhai Formation. This suite of conodont datums and zones will help to improve the global correlations of Permian strata of the Kungurian Stage.
The Shennongjia Group on the northern margin of the Yangtze Platform consists of thick marine carbonate and clastic rocks of the middle and late Mesoproterozoic Era. The middle part of the Shennongjia Group, i.e., the Taizi Formation, consists of sandstone and silty shale in the lower part and fine-crystalline limestone in the upper part. According to previous investigations, organic-walled microfossils of the Taizi Formation are the most abundant among the formations of the Shennongjia Group. To further improve the understanding of the biodiversity during the deposition of the Taizi Formation, we carry out a micropaleontological investigation on the fine-clastic rocks of the Taizi Formation from the Tiechanghe section, Shennongjia National Park, Hubei Province. Our investigation reveals a moderately diverse assemblage of organic-walled microfossils dominated by spherical vesicles and aggregates with a few complex vesicle forms. In addition, the fossil specimens of the Taizi assemblage are very small, generally ranging from 20 to 50 μm. A total of 11 microfossil taxa belonging to seven genera have been identified. These taxa include simple spherical form (Leiosphaeridia crassa, Leiosphaeridia minutissima, Leiosphaeridia jacutica, Leiosphaeridia bicrura, and Leiosphaeridia sp.), cell aggregate form (Synsphaeridium sp. and Eomicrocystis malgica), and complex vesicle form (Navifusa sp., Satka sp., Germinosphaera sp., and Arctacellularia tetragonala). As for biological affinity, prokaryotes are the predominant components, whereas eukaryotes are scarce. The low diversity and small individual size of the microfossils of the Taizi assemblage, which might be caused by a harsh living environment or insufficient essential nutrients, are significantly different from those of the earlier and later biological communities. Furthermore, the Taizi Formation has experienced low- to middle-grade metamorphism with peak metamorphic temperatures of ~280°C based on Raman geothermometers of individual organic-walled microfossils, which is higher than those of other well-preserved Proterozoic microfossils. The high burial temperature may affect the preservation quality of the microfossils of the Taizi assemblage.扬子台地北缘神农架群发育一套中元古代中期和晚期的海相碳酸盐岩与碎屑岩地层, 其中台子组是神农架群中部地层, 也是该群古生物化石丰度最高的组。本文利用化学浸泡法对中元古代中期台子组细粒碎屑岩进行微体化石研究, 结果显示: 台子组化石总的特征是组合简单、化石个体较小, 大部分标本直径介于20–50 μm。本文共鉴定出微体化石7属11种, 包括光面球形类Leiosphaeridia crassa、L. minutissima、L. jacutica、L. bicrura和Leiosphaeridia sp., 细胞聚合体Synsphaeridium sp.、Eomicrocystis malgica和相对复杂的疑源类Navifusa sp.、Satka sp.、Germinosphaera sp.与Arctacellularia tetragonala。台子组微体化石组合中原核生物是主要的化石类型,真核生物丰度很低。其化石多样性和膜壳平均直径远小于邻近时期的生物化石群落, 这可能与台子组沉积期的地表环境特征以及独特的生物群落特征有关。拉曼光谱分析表明台子组有机质处于较高的热演化阶段, 埋藏温度约280℃, 过高的埋藏温度也可能降低了台子组化石保存质量。
The Nanpanjiang Basin is a key area for paleontological and biostratigraphical study of the Middle Triassic. Herein we studied Middle Triassic conodonts from a well-exposed section, the Shaiwa Section, which is located at the northwest end of the Nanpanjiang Basin. A total of six Anisian conodont zones are recognized; in ascending order, they are: the Nicoraella germanica Zone, the Nicoraella kockeli Zone, the Paragondolella bulgarica Zone, the Neogondolella constricta Zone, the Neogondolella cornuta Zone, and the Paragondolella excelsa Zone, respectively. The first occurrence of Nicoraella kockeli defines the Bithynian-Pelsonian boundary. The Pelsonian-Illyrian boundary is defined by the first occurrence of Neogondolella constricta. The Anisian-Ladinian boundary cannot be recognized at the Shaiwa Section due to the absence of conodont indicative of the Ladinian. However, the new conodont data indicate that the uppermost strata could be very close to the boundary. The abrasion of conodont surfaces provides evidence for demonstrating reworking at the Shaiwa Section, which makes some conodonts possess a longer stratigraphic range than previously recorded. The variation in relative abundance between blade-shaped conodonts and platform conodonts indicates that segminiplanate elements probably preferred deeper and oxygenated environments whereas a restricted marine environment is more suitable for segminate elements.
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