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Spatio-temporal carbon isotope variation during the Ediacaran period in South china and its impact on bio-evolution

science china earth sciences 2009年第10期52卷 1520-1528页

作者： wang xinqiang1 & shi xiaoying1,2 1 school of earth science and mineral resources, china university of geosciences, beijing 100083, china 2 State Key Laboratory of Geological Processes and mineral resources, beijing 100083, china school of earth science and mineral resources China University of Geosciences Beijing 100083 China State Key Laboratory of Geological Processes and mineral resources Beijing 100083 China

The Ediacaran period is characterized by the extremely negative carbon isotope anomalies and great biotic evolution in earth history. At least four negative carbon isotope anomalies have been reported from this interval in South china so far. It is traditionally argued that the isotope variations can be used as a useful tool for global correlation of Ediacaran succession; however, more and more researches argued against this idea. We reviewed the previously published carbon isotope data in South china, and distributed the mean values of a certain time to the paleogeographic maps. The results show that the carbon isotope values (δ13C) vary greatly in different environments, but a clear tendency of becoming lighter from shallow platform to deep basin, with a maximum variation up to 1‰ Moreover, the important changes in Ediacaran biota, marked by the introducing of new taxa or ecologic groups, seemed to always postdate the negative anomalies but coincide with the positive shift. If the negative excursions represented the oxidation of a large dissolved organic carbon (DOC) reservoir in the ocean, the diverse Ediacaran organisms and the carbon isotope anomalies may suggest totally different environments: oxic and anoxic/euxinic. We also suggest that the elimination of euxinic state through precipitation of pyrites is one of the important environment factors in prompting the Ediacaran bio-evolution.

关键词： Ediacaran South china carbon isotope spatio-temporal variations bio-evolution

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Pioneer organisms after F-F mass extinction in Dushan region,Guizhou Province,and their significance in establishing new ecosystem

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science china earth sciences 2006年第5期49卷 449-460页

作者： wang Yue1, 2, wang Xunlian1 & shi xiaoying1 1. school of earth sciences and resources, china university of geosciences, beijing 100083, china 2. school of resources and Environment, Guizhou university, Guiyang 550003, china 1. school of earth sciences and resources China University of Geosciences Beijing 100083 China 2. school of resources and Environment Guizhou University Guiyang 550003 China

After mass extinctions, most areas became “ecologically barren areas” lacking or even without ecosystem over an extensive region. Studying the pioneer organisms and the reconstruction process of a new ecosystem in the “ecologically barren area” is very important for revealing the evo- lution after bio-mass extinctions. In the Dushan region, Guizhou Province, china, the trace fossils appeared and flourished evidently earlier than body fossils after Frasnian-Famennian (F-F) mass extinction. The pioneer organisms and pathfinders in the “ecologically barren areas” are the trace-makers that are deposit-feeders with relatively simple structure and conformation on or near the deposit surface. The trace-makers have undergone an evolutionary process that their trace structures changed from simple to complex, and their living and moving areas and spaces enlarged from linear to planar and then to three-dimension spaces. Those characters show that the ability of the trace-makers to deposits and their efficiency of looking for food have been enhanced gradually and that those trace-makers constructed gradually a base for the new ecosystem. This process is similar to that of the trace fossils near the Precambrian-Cambrian boundary. In the Dushan area, only the recovery intervals have been identified for the Famennian body fossils, with no eminent radiation interval recognizable due to the Devonian-Carboniferous (C-D) mass ex- tinction. However, both the recovery and radiation intervals may be clearly recognized in the Famen- nian trace fossils based on their conformation and diversity. The evolution and diversification of the trace fossils in the “ecologically barren area” is considered to have played a role of necessary foun- dation for the recovery of body fossils in the ecological chain. With the gradual disappearance of the unfavourable environment factors resulting in the F-F mass extinction, a new ecosystem was reconstructed in the “ecologically barren area” through a three-

关键词： pioneer organisms, reconstruction of ecosystem, trace fossils, F-F mass extinction, Later Devonian, Dushan region, Guizhou Province, china.

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The Crustal Shortening and Reconstruction of the Main Terranes Through Mesozoic-Cenozoic in Qinghai-Tibet Plateau

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地学前缘 2009年第S1期16卷 270-271页

作者： Meifeng shi~(1,2),Yalin Li~2,Ke Cao~2 1.Chengdu Institute of Geology and mineral resources,Chengdu 610082,china. 2.school of earth sciences and resources,china university of geosciences(beijing),beijing 100083,china

It is one of hot issues in Tibetan research that is to study the mode,process and kinetics of the crustal shortening during *** this paper, on the basis of systematic collection,analysis and research of the existing data and results from Himalayas,Lhasa and Qiangtang terranes,we conducted the balanced cross-section *** the north Qiangtang,the line-balanced cross-section

关键词： Qinghai-Tibet Plateau crustal shortening shortening value terrane

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A Scheme of the Hierarchy for Sequence Stratigraphy

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Journal of earth science 1996年第1期15卷 1-12页

作者： wang Hongzhen shi xiaoying (Department of Geology and mineral resources, china university of geosciences, beijing 100083)

Depositional sequences may be distinguished into six ranks of units as giga-, mega-, meso-, ortho-, sub- and micro-sequence, and are interpreted to be formed during the eustatic cycles with time-intervals of 500-6000 Ma, 60-120 Ma, 30-40 Ma, 2-5 Ma, 0.1-0.4 Ma and 0.02-0.04 Ma respectively. All of them are thought to be essentially related to cosmological cycles, except the megasequence which may be caused by the long-term geothermal cycles on cratons. We deem that the depositional sequences, though often influenced variably by local tectonics and other factors, are primarily global and periodic in nature. We also hold that as one of the planets within the Galaxy, the earth must have been affected in various ways by other asteroids, and that the depositional sequences are merely the responses of the hydrosphere to the cosmological cycles in sedimentation.

关键词： hierarchy sequence stratigraphy,eustatic cycle cosmological cycle.

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An　Outline　of　Mesozoic　to　Paleogene　SequenceStratigraphy　and　Sea－Level　Changes　in　Northern　Himalayas，Southern　Xizang

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Journal of earth science 1995年第1期14卷 16-40页

作者： shi xiaoying Yin Jiarun(Department of Geology and mineral resources, china university of geosciences,beijing 100083)

In the Northern Himalayan region of Southern Xizang (Tibet),from the Lower Triassic to Upper Eocene 73 Sequences have been identified, with an average duration of 2.9 Ma;these can in turn be grouped into 24 super-Sequences and 6 super-sequence sets. During Mesozoic and Paleogene, several large sea - level falls occurred in the Eastern Neo-Tethys. Among the recognized sea- level falls, the important ones include those at the ages of 255 Ma, 215 Ma,177 Ma, 138 Ma, 103 Ma and 68 Ma .Those at 239 Ma, 215 Ma, 157 Ma,80 Ma, 50Ma and 36 Ma are also significant. The third-order Sequences and sea-level cycles Probably reflect mainly global sea - level fluctuations, while the higher rank cycles seem more closely related to the basin evolution of the Neo-Tethys. Based on the study, six major periods have been suggested for ths tectonic evolution of the Eastern Neo-Tethys and the plates, i. e. the Pangea Period (Pre-Triassic), continental rifting Period (Triassic to Early Jurassic ), inter-continental sea Period (Middle Jurassic ), continental divergence period (late Middle Jurassic to Early Cretaceous ), continental convergence period (Late Cretaceous ) and the continental collision Period (Paleogene ). These major Periods can be further subdivided into eight stages according to the basin evolution. In each of the periods and Stages, Sequences and their boundaries show clear characters related to the tectonic background. The study indicater that the initial breakup of the Pangea along the Indus- Yarlung may have taken Place around 239 Ma. The Late Bathonian to Early Callovian seems to have been a critical time in the evolution of the Neo-Tethys, with the turning Point around 158 Ma. The blocks split from the northern margin of the Gondwana continual did not obviously drift away from the Indian Plate until Callovian .The oceanic crust subduction in the Neo- Tethys may have Started at 113Ma, while the contraction of the ocean probably began at 107- 103 Ma. The initial contact of

关键词： Sequence stratigraphy sea-level change Mesozoic Cenozoic Northern Himalayas,southern Xizang.

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Paleogene Sequence Stratigraphy and Sea Level Change Cycles in South Xizang (Tibet) - Last Stage in Eastern Neo-Tethyan Evolution

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Journal of earth science 1996年第1期15卷 122-131页

作者： shi xiaoying Wan Xiaoqiao Jia Caiping (Department of Geology and mineral resources, china university of geosciences, beijing 100083)

The marine Paleogene at Gangba, south Tibet is characterized by shallow water deposits and in vertical succession shows a clear facies change from fluvial plain through carbonate platform to retro-platform mud flat. From the bottom of Danian to Upper Priabonian, nine 3rd -order depositional sequences are recognized, which in turn make up four supersequences and constitute two clear transgression-regression cycles. These requences were developed in a tectonic setting of strong compression resulted from the collision between the Indian and Eurasian plates. Between the Paleocene and Eocene, there exists an important hiatus that has consumed at least 5.5 Ma of deposition. This unconformity is thought to be created by the basement uplift coupled with eustatic fall and marks the basin transformation from epicontinental sea to remnant hay. The rapid basement subsidence and relative sea level rise in Late Eocene are thought to be caused by the loading flexure of the Eurasian continent onto the Indian plate, which resulted in the southward migration of depocenter in the epoch.

关键词： Paleogene sequence sea level cycle tectonic evolution south Tibet.

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Cambrian Sequence Stratigraphy and Sea Level Cycles of North china Platform

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Journal of earth science 1999年第2期18卷 20-28页

作者： shi xiaoying Mei shilong Chen Jianqiang Yang Xinde Department of Geology and mineral resources, china university of geosciences, beijing 100083

The Cambrian of the North china platform consists chiefly of shallow water deposits and shows the sedimentary characters of an epicontinental sea basin. Controlled mainly by global sea level changes and sedimentary influx, the depositional sequences all exhibit as composite sequences. From bottom upward, 14 sequences (3rd order) are recognized, which may be grouped into 5 sequence sets and further into 2 mesosequences (2nd order). It is suggested herein that the Cambrian/Ordovician boundary may better be set at the MFS (maximum flooding surface) of the sequence OSq1, above which the conodont Cordylodus lindstroemi occurs. This position is about 40 m above the traditional Cambrian/Ordovician boundary and is within the Yeli Formation.

关键词： Cambrian sequence stratigraphy sea level change cycle Cambrian/Ordovician boundary North china platform.

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Chemocline instability and isotope variations of the Ediacaran Doushantuo basin in South china

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science china earth sciences 2008年第11期51卷 1560-1569页

作者： JIANG GanQing ZHANG shiHong shi xiaoying wang xinqiang Department of Geoscience University of NevadaLas VegasNV 89154-4010USA school of earth sciences and resources China University of GeosciencesBeijing 100083China State Key Laboratory of Geological Process and mineral resources Beijing 100083China

Stable isotope analyses in sections across a shelf to basinal transect of the Ediacaran Doushantuo basin show substantial isotope variabilities. In Songlin section where sediments were deposited in an intrashelf basin, δ 13C values are persistently negative (_3‰ to _5‰, VPDB) through the entire Doushantuo Formation, similar to those obtained from the slope section in Wuhe (_5‰ to _10‰, VPDB). Shallow water sections in Weng'an and Duoding show two broad δ 13C anomalies overprinted with significant meter-scale variations, but none of the curves has similar absolute δ 13C values compared to the Yangtze Gorges areas in South china and other sections globally. Such isotope variations, if partially recording ancient seawater signature, imply spatial and temporal chemocline instability in the Doushantuo basin. In combination with available δ 13C records from other Ediacaran successions globally, the data from the Doushantuo basin are consistent, in first order, with the existence and oxidation of a large dissolved organic carbon (DOC) reservoir in Ediacaran oceans, but imply local environmental controls on Neoproterozoic isotope values and call attentions for using δ 13C anomalies as time lines in stratigraphic correlation.

关键词： Ediacaran isotopes chemocline early animals Doushantuo Formation South china

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New U-Pb age constraints on the upper Banxi Group and synchrony of the Sturtian glaciation in South china

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Geoscience Frontiers 2017年第5期8卷 1161-1173页

作者： Gaoyuan Song xinqiang wang xiaoying shi Ganqing Jiang school of earth science and resources China University of Geosciences (Beijing) Beijing 100083 China State Key Laboratory of Biogeology and Environmental Geology Beijing 100083 China Department of Geoscience University of Nevada Las Vegas NV 89154-4010 USA

The Nanhua basin in South china hosts well-preserved middle-late Neoproterozoic sedimentary and volcanic rocks that are critical for studying the basin evolution, the breakup of the supercontinent Rodinia, the nature and dynamics of the "snowball" earth and diversification of metazoans. Establishing a stratigraphic framework is crucial for better understanding the interactions between tectonic, paleoclimatic and biotic events recorded in the Nanhua basin, but existing stratigraphic correlations remain debated, particularly for pre-Ediacaran strata. Here we report new Laser Ablation Inductively Coupled Plasma Mass Spectrometry(LA-ICPMS) U-Pb zircon ages from the middle and topmost Wuqiangxi Formation(the upper stratigraphic unit of the Banxi Group) in Siduping, Hunan Province, South china. Two samples show similar age distribution, with two major peaks at ca. 820 Ma and 780 Ma and one minor peak at ca. 910 Ma, suggesting that the Wuqiangxi sandstone was mainly sourced from Neoproterozoic rocks. Two major age peaks correspond to two phases of magmatic events associated with the rifting of the Nanhua basin, and the minor peak at ca. 910 Ma may correspond to the Shuangxiwu volcanic arc magmatism, which represents pre-collision/amalgamation subduction on the southeastern margin of the Yangtze Block. The youngest zircon group from the topmost Wuqiangxi Formation has a weighted mean age of 714.6±5.2 Ma, which is likely close to the depositional age of the uppermost Banxi Group. This age, along with the ages reported from other sections, constrains that the Banxi Group was deposited between ca. 820 Ma and ca. 715 Ma. The age of 714.6±5.2 Ma from the top of the Wuqiangxi Formation is indistinguishable with the SIMS U-Pb age of 715.9± 2.8 Ma from the upper Gongdong Formation in the Sibao village section of northern Guangxi, South china. It is also, within uncertainties, overlapped with two TIMS U-Pb ages from pre-Sturtian strata in Oman and Canada. These ages indicate that th

关键词： Nanhua basin Wuqiangxi Formation Banxi Group U-Pb zircon ages Sturtian glaciation South china

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Nitrogen Isotopes from the Neoproterozoic Liulaobei Formation,North china:Implications for Nitrogen Cycling and Eukaryotic Evolution

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Journal of earth science 2022年第5期33卷 1309-1319页

作者： Ting Yang xinqiang wang Dongtao Xu xiaoying shi Yongbo Peng school of earth science and resources China University of GeosciencesBeijing100083China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing100083China International Center for Isotope Effect Research Nanjing UniversityNanjing210023China school of earth sciences and Engineering Nanjing UniversityNanjing210023China

The nitrogen isotope compositions(δ^(15)N )of sedimentary rocks can provide information about the nutrient N cycling and redox conditions that may have played important roles in biological evolution in earth’s *** considerableδ^(15)N data for the Precambrian have been published,there is a large gap during the Early Neoproterozoic that restrains our understanding of the linkages among N cycling,ocean redox changes and biological evolution during this key ***,we report bulkδ^(15)N and organic carbon isotope(^(δ)13C_(org))compositions as well as the total nitrogen(TN)and total organic carbon(TOC)contents from the Tonian fossiliferous Liulaobei Formation in the southern part of the North china ***δ^(15)N in the study section is dominated by very stable values centering around+4.3‰,which is moderately lower than that in modern sediments(~+6‰).These positiveδ^(15)N values were attributed to partial denitrification under low primary productivity(scenario 1)and/or denitrification coupled with dissimilatory nitrate reduction to ammonium(DNRA)(scenario 2).In either case,the availability of fixed nitrogen may have provided the nutrient N required to facilitate facilitated eukaryotic *** study highlights the pivotal role of nutrient N in the evolution of eukaryotes.

关键词： Neoproterozoic Tonian Liulaobei Formation nitrogen isotopes eukaryotic evolution nutrient limitation geochemistry

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