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Revisiting the Mg isotopic systematics of siliciclastic components of sediments and sedimentary rocks:A new geochemical proxy of continental weathering in Earth's history

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Science China Earth Sciences 2024年第2期67卷 620-633页

作者： Tianzheng HUANG Bing SHEN Kangjun HUANG Meng NING Chao LI jinzhuang xue Yuanlin SUN Baoqi HUANG Key Laboratory of Orogenic Belt and Crustal Evolution MOESchool of Earth and Space SciencesPeking UniversityBeijing100871China State Key Laboratory of Continental Dynamics Shaanxi Key Laboratory of Early Life and EnvironmentsDepartment of GeologyNorthwest UniversityXi’an710069China Institute of Sedimentary Geology Chengdu University of TechnologyChengdu610059China Key Laboratory of Rhenium-Osmium Isotopic Geochemistry Chinese Academy of Geological SciencesBeijing100037China

The Mg isotopic compositions of siliciclastic components(δ^(26)Mg_(sili))of sediments and sedimentary rocks have been commonly used to constrain the intensity of continental weathering,based on observations of,(1)an upward enrichment of26Mg in modern weathering profiles,(2)preferential uptake of26Mg in soil clays,and(3)general positive correlations between weathering intensities andδ^(26)Mg_(sili)values.However,not all weathering profiles display an upward increase ofδ^(26)Mg_(sili),and not all soil clays enrich in26Mg,complicating the interpretations ofδ^(26)Mg_(sili)data of sediments and sedimentary rocks.To further explore the controls ofδ^(26)Mg_(sili)of sediments and sedimentary rocks,here we measuredδ^(26)Mg_(sili),mineralogical compositions and major element compositions of deep sea sediments from South China Sea(SCS)and carbonate rock samples from two late Paleozoic sections in South China.Carbonate samples show decreasing trends of both normalized Mg concentration(Mgnorm)andδ^(26)Mg_(sili)values with the increase of weathering intensity,while SCS sediments samples do not show any correlation between Mgnormorδ^(26)Mg_(sili)values and weathering intensity.A three-stages weathering model is developed to explain the observed Mgnorm andδ^(26)Mg_(sili)data.In the new model,weathering can be divided into three stages,(1)the preliminary weathering stage characterized by dissolution of primary minerals and formation of secondary clay minerals in saprolite,(2)the transitional stage with massive vermiculite and chlorite formation on the bottom of soil,and(3)the advanced stage showing dissolution of vermiculite and chlorite in the top of soil.The new model explains anδ^(26)Mg_(sili)increase and Mgnormdecrease with an increase weathering intensity in preliminary weathering stage and decrease of Mgnormandδ^(26)Mg_(sili)with increase weathering intensity in advanced weathering stage.The revised weathering model warrants the application of Mg isotope in the study of continental weathering in deep time.

关键词： Clay mineral Chemical weathering CIA Soil Weathering model

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Validating the deep time carbonate carbon isotope records: effect of benthic flux on seafloor carbonate

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Acta Geochimica 2021年第3期40卷 271-286页

作者： Weiming Ding Ting Nie Yongbo Peng Yuanlin Sun jinzhuang xue Bing Shen Key Laboratory of Orogenic Belts and Crustal Evolution MOESchool of Earth and Space SciencePeking UniversityBeijing 100871China School of Earth Sciences and Engineering Nanjing UniversityNanjing 210023China

It is a consensus that marine carbonate archives the isotopic composition of seawater dissolved inorganic carbon(DIC,δ13Csw),the largest active C reservoir in the hydrosphere.Carbonate carbon isotope(δ13Ccarb)excursions have been used to reflect perturbations of the global carbon cycle and related environmental change.However,the deep timeδ13Ccarb records indicate faster and more pronounced perturbations of the carbon cycle compared to the present day.Here,we reportδ13Ccarb and elemental compositions of Late Paleozoic carbonate sections from South China,showing negative correlations betweenδ13-Ccarb and Fe^(2+)content of carbonate(Fecarb).We suggest that,because Late Paleozoic carbonate was mainly produced by benthic carbonate-secreting organisms,δ13Ccarbrecorded the isotopic composition near the seafloor,where benthic flux derived from anaerobic organic matter degradation delivers both Fe2+and 13C-depleted DIC from porewater.The binary mixing between seawater and benthic flux would result in the deviation ofδ13Ccarb fromδ13Csw.The negative correlation implies thatδ13Ccarb is influenced by benthic flux and is affected by the seafloor redox and sedimentation rate.The deep time spatially heterogeneous and temporally oscillatoryδ13Ccarb records in the basin-scale could be alternatively attributed to the variations of local environmental factors rather than aδ13Csw depth-gradient.Thus,the seafloor carbonate precipitation is continuously affected by diagenetic reactions in sediments,suggesting thatδ13Ccarb recording the seawater DIC composition is conditional.Our study urges that the interpretation ofδ13Ccarb should also consider the sedimentary process and depositional environment of marine carbonate.

关键词： Fe^(2+)content of carbonate(Fecarb) Benthic flux Sediment Paleozoic South China

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Phylogeny of Devonian Lycopsids Inferred from Bayesian Phylogenetic Analyses

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Acta Geologica Sinica(English Edition) 2011年第3期85卷 569-580页

作者： xue jinzhuang The Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University Beijing 100871 China

To investigate the phylogeny of early lycopsids,cladistic analyses using both parsimony and Bayesian approaches are presented,with a data matrix of 33 morphological characters across 25 taxa. The resulting parsimony and Bayesian trees showed overall similarities in tree topologies.In the Bayesian tree,the Protolepidodendrales and the heterosporous lycopsids are recognized as two monophyletic groups,and within the latter group,the Isoetales sensu lato forms a subclade.This topology implies that the acquisition of a ligulate character evolved twice in the lycopsids,once in the protolepidodendralean Leclercqia Banks et al.,and once in the heterosporous lycopsid clade. Phylogenetic positions of several lycopsid plants previously reported from the Mid-Upper Devonian of South China,which have uncertain ordinal affinities,were estimated by the cladistic analyses;cf. Longostachys xue et Hao,Longostachys Zhu et al.,Monilistrobus Wang et Berry,and Yuguangia Hao et al.fall well within the Isoetales clade,as earliest members of this order,while Minostrobus Wang and Wuxia Berry et al.are nested within the basal part of the heterosporous lycopsids.Bayesian analyses are a very useful approach in systematic studies and can be applied in analyzing paleobotanical data sets as well.

关键词： Bayesian phylogenetics cladistic analysis lycopsid Protolepidodendrales Devonian

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Two Zosterophyll Plants from the Lower Devonian(Lochkovian)Xitun Formation of Northeastern Yunnan,China

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Acta Geologica Sinica(English Edition) 2009年第3期83卷 504-512页

作者： xue jinzhuang The Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University Beijing 100871 China

Two zosterophyll plants are described from the Lower Devonian （Lochkovian） Xitun Formation of Qujing, Yunnan, China. Xitunia spinitheca gen. et sp. nov. has stalked sporangia laterally attached on the axis in a helical arrangement. Sporangia are dorsoventrally flattened and composed of two unequal valves; the adaxial valve is round in face view, while the abaxial valve is larger than the former, triangular or wedge-shaped, and radially bears long spiny appendages along the distal margin. Xitunia shows new variation of sporangial morphology within the zosterophylls. Zosterophyllum minorstachyum sp. nov. has K-shaped branchings at the basal parts and small-sized terminal spikes, which consist of round to elliptical sporangia arranged helically. This paper provides new data on the diversity of plant types during Lochkovian when rare vascular plants were reported. As for various species of Zosterophyllum in South China, their apparent evolutionary trend of features from the Late Silurian to Early Devonian （Emsian） is discussed.

关键词： Early Devonian Lochkovian Xitunia gen. nov. zosterophyll ZosterophyUum

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A New Zosterophyll Plant,Ramoferis gen.nov.,from the Posongchong Formation of Lower Devonian (Pragian) of Southeastern Yunnan,China

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Acta Geologica Sinica(English Edition) 2011年第4期85卷 765-776页

作者： HAO Shougang xue jinzhuang Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China

A new genus and species,Ramoferis amalia gen.et sp.nov.,is described from the Early Devonian（Pragian）Posongchong Formation,Wenshan district of southeastern Yunnan,China.This plant has isodichotomous major axes,which also divide anisotomously distally to produce closely spaced lateral branches,often within fertile regions.The stalked round to reniform sporangia,borne laterally and spirally over several levels of branches,are distantly to moderately spaced or aggregated into distinct spikes.The stalks increase in width from the base to the sporangial junction resulting in a gradual transition between sporangium and stalk.Comparison with known zosterophylls shows that this plant is most similar to the genera Zosterophyllum and Wenshania,differing in the character combinations of sporangial shape,sporangium/stalk junction,stalk dimensions and orientation,and especially in both sterile and fertile branchlets being borne within the fertile zone.In addition,the observation and comparison indicate distinct variety in structure of sporangial border and suggest that the two-layered sporangium wall characterized by outer anticlinal layer and inner periclinal layer might represent potential synapomorphies,while the different dehiscence mechanism is an autapomorphy for each taxon in zosterophylls.

关键词： zosterophyll Early Devonian Posongchong Flora Yunnan

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Earliest record of megaphylls and leafy structures, and their initial diversification

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Chinese Science Bulletin 2013年第23期58卷 2784-2793页

作者： HAO ShouGang xue jinzhuang Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University

Evolutionary changes in the structure of leaves have had far-reaching effects on the anatomy and physiology of vascular plants, resulting in morphological diversity and species expansion. People have long been interested in the question of the nature of the morphology of early leaves and how they were attained. At least five lineages of euphyllophytes can be recognized among the Early Devonian fossil plants (Pragian age, ca. 410 Ma ago) of South China. Their different leaf precursors or "branch-leaf complexes" are believed to foreshadow true megaphylls with different venation patterns and configurations, indicating that multiple origins of megaphylls had occurred by the Early Devonian, much earlier than has previously been recognized. In addition to megaphylls in euphyllophytes, the laminate leaf-like appendages (sporophylls or bracts) occurred independently in several distantly related Early Devonian plant lineages, probably as a response to ecological factors such as high atmospheric CO 2 concentrations. This is a typical example of convergent evolution in early plants.

关键词：叶结构多元化植物解剖学早泥盆世二氧化碳浓度趋同进化叶片结构植物化石

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A New Lycopsid, Zhenglia radiata gen. et sp. nov., from the Lower Devonian Posongchong Formation of Southeastern Yunnan, China, and Its Evolutionary Significance

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Acta Geologica Sinica(English Edition) 2006年第1期80卷 11-19页

作者： HAO Shougang WANG Deming WANG Qi xue jinzhuang The Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University Beijing 100871 Institute of Botany Chinese Academy of Sciences Xiangshan Beijing 100093

A new plant, Zhenglia radiata gen. et sp. nov., from the Posongchong Formation （Early Devonian, Pragian age） of the Wenshan District of southeastern Yunnan Province, China is a small herbaceous lycopsid. The aerial branches divide into foliar and fertile stems. The arrangement of the leaf bases on the stem shows lepidodendroid-like phyllotaxy. Possibly the leaf base bears a ligulate pit. The microphyll consists of a swollen, decurrent base, and an entire, linear lamina. The fertile axis is composed of sporophylls arranged helically, forming a compact area similar to cone-like structure. Each sporophyll consists of a widened lateral extension and a distal lamina. The ovoid-elongate sporangia are attached adaxially on the surface of sporophylls. Based on morphological similarities, especially the undivided microphylls, the style of phyllotaxy, the form of the cone-like structures and sporangia, the new lycopsid Zhenglia radiata is placed in the order Protolepidodendrales and a possible evolutionary relationship with the arborescent lycopsids of the Late Devonian and Carboniferous is considered.

关键词： Devonian Pragian lycopsid microphyll sporophyll Posongchong flora China

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陆地植物的起源、早期演化及地球环境效应

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地球科学 2022年第10期47卷 3648-3664页

作者：薛进庄王嘉树李炳鑫黄璞刘乐北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室北京100871 中国科学院南京地质古生物研究所江苏南京210008 中国矿业大学地球科学与测绘工程学院北京100083

研究陆地植物在古生代的起源和早期演化(简称“植物登陆”)及它们对地表环境的塑造作用,对于理解地球系统的演化规律具有重要意义.证据表明,泥盆纪是维管植物辐射演化的关键时期,现代支系如石松类、真蕨类、楔叶类、种子植物等在该时期... 详细信息

研究陆地植物在古生代的起源和早期演化(简称“植物登陆”)及它们对地表环境的塑造作用,对于理解地球系统的演化规律具有重要意义.证据表明,泥盆纪是维管植物辐射演化的关键时期,现代支系如石松类、真蕨类、楔叶类、种子植物等在该时期奠基,根系、大型叶、次生木质部、种子等性状快速演化出现并复杂化,森林在中泥盆世以来成为陆地植被的重要组分.近年来,在古生代植被控制河流沉积体系的转变、陆地植物的化学风化增强效应、古生代陆地有机碳埋藏等的研究方面取得了重要进展.未来需要通过从基因到陆地生态系统等多个层次的研究,进一步揭示植物登陆的过程与机制,从微观、生境、区域到全球多个空间尺度,进一步研究植物登陆对地球环境的影响.

关键词：古生代陆地植物大陆风化作用碳循环森林湿地.

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云南曲靖下泥盆统桂家屯组一种新的工蕨类植物及栖生的微螺虫

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北京大学学报（自然科学版） 2022年第5期58卷 861-874页

作者：杨帅黄璞刘璐王嘉树张久东薛进庄造山带与地壳演化教育部重点实验室北京大学地球与空间科学学院北京100871 中国科学院南京地质古生物研究所南京210008 北京自然博物馆北京100050 宿州学院资源与土木工程学院宿州234000

记述发现于云南曲靖锅盖山剖面桂家屯组的一种早期维管植物。该植物茎轴裸露,根状茎以连续多次K型或H型分枝形成复杂的分枝系统,直立轴呈简单的二歧式分枝,孢子囊侧视呈匙形至卵形,螺旋状着生于穗轴上。该植物体型较小,保存较完整的根状... 详细信息

记述发现于云南曲靖锅盖山剖面桂家屯组的一种早期维管植物。该植物茎轴裸露,根状茎以连续多次K型或H型分枝形成复杂的分枝系统,直立轴呈简单的二歧式分枝,孢子囊侧视呈匙形至卵形,螺旋状着生于穗轴上。该植物体型较小,保存较完整的根状茎,但孢子囊穗的保存状况较差,孢子囊结构不够清晰,无明显可见的孢子囊开裂线,因此将其暂定为cf.Zosterophyllum sp.。尽管如此,该植物展现的性状特征不同于典型的Zosterophyllum及其他相关属种,丰富了人们对早期维管植物形态变异及桂家屯组植物组合的认识。在cf.Zosterophyllumsp.的直立轴表面栖生大量微螺虫(microconchids)标本,直径为0.7~2.2 mm。微螺虫是一种已灭绝的水生无脊椎动物,发现于晚奥陶世到中侏罗世末期地层中,其壳体为螺旋状的钙质管,习惯固着在包括植物在内的各种硬质基体上。微螺虫在cf.Zosterophyllumsp.的直立轴栖生,表明该植物在生长期间曾被水体淹没,之后微螺虫伴随植物茎干被搬运和埋藏。

关键词：早期维管植物工蕨类微螺虫桂家屯组下泥盆统

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早期维管植物辐射演化与长时间尺度水循环的耦合关系

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科学通报 2023年第12期68卷 1459-1472页

作者：薛进庄李炳鑫王嘉树刘乐黄璞熊聪慧沈冰北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室北京100871 中国矿业大学(北京)地球科学与测绘工程学院北京100083 中国科学院南京地质古生物研究所南京210008 兰州大学地质科学与矿产资源学院甘肃省西部矿产资源重点实验室兰州730000

志留纪-泥盆纪陆地革命以早期维管植物的起源和辐射演化为标志.早期维管植物的繁盛导致形成全新的土壤-植物-大气连续体(soil-plant-atmosphere continuum, SPAC).早期植物在根系、输导组织、气孔、叶片、个体大小和构型等方面的一系列... 详细信息

志留纪-泥盆纪陆地革命以早期维管植物的起源和辐射演化为标志.早期维管植物的繁盛导致形成全新的土壤-植物-大气连续体(soil-plant-atmosphere continuum, SPAC).早期植物在根系、输导组织、气孔、叶片、个体大小和构型等方面的一系列演化革新,深刻改变了SPAC中的水分传输过程与机制.由于根系的进化及其诱导的化学风化作用增强,泥盆纪以来的古土壤厚度逐渐增大、分层结构复杂化、组成成熟度增加、类型多样化.伴随着早期维管植物的演化, SPAC的空间范围极大扩展,生物可利用水资源增多,水分在SPAC中的循环过程更为复杂、高效.早期维管植物的辐射增强了植被-地貌-水循环之间的反馈机制.志留纪晚期以来,植被与水文、地貌、生物地球化学等物理和化学要素相互作用,维管植物型陆-海水文连续体(land-ocean hydrologic continuum, LOHC)形成并逐步发展,内陆水体流域至滨岸体系的地貌稳定性增强,由陆到海的生物地球化学循环、物质供给和迁移体系产生变革.早期维管植物通过SPAC、LOHC系统及其内部过程与全球水、碳循环耦合,表现为稳定的低地生境增多,植物残体和有机质的埋藏学窗口增多,以煤为代表的陆地有机碳埋藏增加,河流运输的陆源有机碳通量增大.目前对早期维管植物SPAC系统的研究,大多是定性描述和推测,如何开展定量研究与机理探讨是未来的重要挑战.从微观、生境、区域到全球的多个空间尺度,研究地质剖面中记录的长时间尺度维管植物型LOHC系统的演变,有助于解析早期植物演化、水-碳循环以及地表环境之间的耦合关系.

关键词：早期维管植物泥盆纪古土壤土壤-植物-大气连续体陆-海水文连续体碳循环

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