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| 1 | Paleo-productivity evolution across the Permian-Triassic boundary and quantitative calculation of primary productivity of black rock series from the Dalong Formation, South China显示文摘The change of the primary productivity across the Permian-Triassic boundary(PTB)remains controversial.In this study,records from two deep-water sections in South China(Xiakou and Xinmin sections)show the primary productivity decreased gradually from the latest Permian to the earliest Triassic,and five evolutionary stages Increase-Decrease-Recovery-RecessionStagnation)can be observed from Clarkina changxingensis-C.deflecta to Hindeodus parvus-Isarcicella isarcica zones.Primary productivity decreased abruptly from the base of C.meishanensis zone.Besides,for adjusting to the deterioration of the oceanic environment,the primary producers in the oceanic surface had changed to acritarch and cyanobacteria,which were more tolerant of stressful environment.Then the producers were under huge stagnation in the H.parvus-I.isarcica zone.The values of quantitative calculation of the primary productivity from the black rock series in the Dalong Formation were very high,corresponding to that of an upwelling area in modern ocean,which shows that the strata of the Dalong Formation in the study region are potential hydrocarbon source-rocks.This result may come from the fact that South China craton was located at the equatorial upwelling area during the Permian-Triassic transitions.But organic matter contents were different in various sections because they could be affected by redox conditions and diagenesis process after burial. | SHEN Jun ZHOU Lian FENG QingLai ZHANG MuHui LEI Yong ZHANG Ning YU JianXin GU SongZhu | 2014 | Science China Earth Sciences2014，57，7： | 8 |
| 2 | Late Triassic(Norian)Conodont Apparatuses Revealed by Conodont Clusters from Yunnan Province,Southwestern China显示文摘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. | Weiping Zeng Mark A.Purnell Haishui Jiang Muhui Zhang | 2021 | Journal of Earth Science2021，32，3： | 2 |
| 3 | Middle Triassic(Anisian)Conodont Biostratigraphy at the Shaiwa Section,Guizhou,South China显示文摘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. | Binxian Qin Martyn Lee Golding Haishui Jiang Yan Chen Muhui Zhang Li Kang Dacheng Wang Jinling Yuan | 2021 | Journal of Earth Science2021，32，3： | 0 |
| 4 | First Records of Late Triassic Conodont Fauna andδ13Ccarb from the Dengdengqiao Section,Dangchang County,Gansu Province,Northwestern China显示文摘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.Theδ13Ccarb 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. | Hanxiao Li Miaoyan Wang Muhui Zhang Paul B.Wignall Manuel Rigo Yanlong Chen Xianlang Wu Zhumin Ouyang Baojin Wu Zhaoyang Yi Zaitian Zhang Xulong Lai | 2021 | Journal of Earth Science2021，32，3： | 0 |
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