Landscape ecological shift at the Permian‐Triassic boundary in Antarctica

Palaeosols across the Permian‐Triassic boundary in Antarctica provide evidence of a marked change in ecosystems at this greatest of all extinctions in the history of life on Earth. The boundary can now be recognised from evidence of carbon isotopic (δ¹³C) stratigraphy, reptiles of the earliest Triassic Lystrosaurus zone, and Late Permian glossopterid fructifications and pollen. The boundary is a profound change in palaeosols, with very different suites of pedotypes in Permian compared with Triassic sequences. Permian palaeosols include coals, rooted lithic sandstones and rooted tuffaceous silt‐stones. Triassic palaeosols in contrast are largely rooted, green‐red‐mottled claystones. These palaeosols represent a shift from Late Permian cold temperate broadleaf deciduous swamp woodlands to Early Triassic cool temperate conifer forests. Indications of more intense weathering during the earliest Triassic confirm a significantly warmer palaeoclimate in the earliest Triassic than in the latest Permian. Palaeoclimate remained humid with low evapotranspiration in both Permian and Triassic, but Triassic ecosystems were more oligotrophic, humus‐poor and more oxidised than Permian ones. Yet both Permian and Triassic palaeosols were unpodzolised, unlike soils today under such climates and vegetation. Palaeosols in Antarctica confirm several peculiarities of the earliest Triassic: (i) a global coal gap; (ii) a high‐latitude greenhouse; and (iii) a Gondwanan tuff gap. Palaeosols support evidence from fossil plants and reptiles and from carbon isotopic studies for a shift toward oligotrophic, low‐productivity ecosystems, dominated by opportunistic and stress‐tolerant organisms in the earliest Triassic. Life was difficult on land as well as in the sea following the terminal Permian mass extinction.     

陆相二叠系-三叠系界线研究进展

着重介绍了几个目前陆相二叠系—三叠系界线（TPTB）研究的重点剖面及其生物地层学研究进展；分析了陆相二叠系—三叠系界线综合地层学研究现状，包括生物地层学、事件地层学、同位素年代学、磁性地层学和层序地层学等；剖析了陆相二叠系-三叠系界线地层学研究中存在的问题及进一步的研究方向。生物地层方面，陆相二叠系-三叠系界线附近存在晚二叠世与早三叠世生物混生的层位，其中不同类别生物的时间界线常不一致，又由于陆相界线地层中含脊椎动物化石的层位一般较少，以脊椎动物化石（Lystrosaurus）为标准的精确界线常不确定，因而需重新寻找并确定陆相三叠系底界的标准化石。事件地层标志可能会成为连结海、陆相二叠系-三叠系界线地层高精度对比的纽带。     

桂西南柳桥地区深水相二叠系-三叠系界线剖面

桂西南柳桥地区上二叠统为厚约84m的浅灰—灰白色块状海绵蓝藻生物灰岩(生物礁),之上为浅灰绿色—暗灰色薄层状含远洋浮游生物硅质岩、含泥质硅质岩、硅质泥岩(大隆组),这套深水相的沉积岩夹有大量浅灰白色的粘土岩。上覆的三叠系罗楼组底部为黄色泥岩,夹多层灰白色粘土岩,往上渐变为灰色薄层状含大量双壳类、菊石化石的钙质泥岩、泥灰岩。柳桥地区晚二叠世末期沉积岩和中基性火山岩的特征显示其是在地壳裂解、快速沉降、相对海平面快速上升过程中迅速淹没台地边缘的生物礁而形成的深水相海盆,造成深水盆地与浅水台地并存,具有多岛洋的地理分布格局。东攀二叠系-三叠系界线剖面的露头完整,对剖面的岩石学特征、生物化石组合特征等方面的详细研究显示,该地区一直处于连续沉积的深水环境中,没有发生沉积间断,界线上下的岩石特征和生物组合特征较清楚。     

Palynological assemblages of non-marine rocks at the Permian–Triassic boundary, western Guizhou and eastern Yunnan, South China

Marine and non-marine facies of the Permian–Triassic boundary stratigraphic set (PTBST) are well developed in South China. Palynological assemblages enable subdivision and correlation of the Permian–Triassic boundary (PTB) rocks. Three palynological assemblages are recognized across the PTBST in two terrestrial PTB sections in western Guizhou and eastern Yunnan, South China. Assemblage 1 (Xuanwei Formation) is a Late Permian palynological assemblage dominated by ferns and pteridosperms, with minor gymnosperms. Most taxa are typical long-ranging Paleozoic forms, but the appearance of Lueckisporites confirms a Late Permian age for this assemblage. Assemblage 2 (PTBST) is marked by an abrupt decrease in palynomorph abundance and diversity, and thriving fungal/algal(?) spores. Assemblage 2 is still dominated by ferns and pteridosperms, with a few gymnosperms, but is characterized by a mixed palynoflora containing both Late Permian and Early Triassic elements. Most taxa are typical Late Permian ones also found in Assemblage 1, however, some taxa of Early Triassic aspect, e.g. Lundbladispora and Taeniaesporites, appeared for the first time. In Assemblage 3 (top Xuanwei Formation and Kayitou Formation), the proportion of gymnosperm pollen increases rapidly, exceeding that of ferns and pteridosperms, but the abundance of palynomorphs is still low. Typical Early Triassic taxa (such as Lundbladispora, Aratrisporites and Taeniaesporites) are present in greater abundance and confirms an Early Triassic age for this assemblage.     

Catastrophic environmental transition at the Permian-Triassic Neo-Tethyan margin of Gondwanaland: Geochemical,isotopic and sedimentological evidence in the Spiti Valley,India

Interpreting global consequences of the Permian-Triassic (P-Tr) extinction requires examination across paleogeographic realms of Pangaea. The Spiti Valley in India, remnant of the peri-Gondwanan shelf, preserved trails of this environmental catastrophe in the Neo-Tethys Ocean. We document new sedimentological observations and high-resolution trace element concentrations and carbon, oxygen, lead isotope data across the P-Tr boundary in Spiti. Framboidal pyrites, fossils and laminated lithology of the Late Permian shales indicate deeper anoxic depositional environment while δ¹³C_org excursions of 2.4‰ and 3.1‰ in Atargu and Guling outcrops, respectively, identify the P-Tr transition across a clayey, partly gypsiferous ferruginous layer. Sedimentological similarities of this layer to other Neo-Tethyan sections from Transcaucasia and Iran indicate subaqueous oxidation of shallow marine sediments on a regional scale. Light Rare Earth Element – enriched Late Permian shales with conspicuous Ce–Eu anomalies reflect their source from the adjacent Panjal Trap basalts (ca. 289 Ma) of Kashmir. Continental crustal Nb–Ta and Zr–Hf anomalies appear at the P-Tr boundary sediments, and prevail through the overlying Early Triassic carbonates. Original Pb isotope ratios, along with an increasing Pb abundance closer to the P-Tr boundary, distinguish the volcanic source of the Late Permian shales from the continental crustal siliciclastic signature of the Early Triassic carbonates. Our δ¹³C_org, trace element and Pb isotope record from Spiti indicate catastrophic changes in sediment sources and facies, with effects on carbon cycle and are consistent with an abrupt episode of marine regression and erosional forcing, also observed elsewhere along northern Gondwanaland. Simultaneous eruption of Siberian volcanics and bolide impacts in Parana basin of Brazil and elsewhere implicating impact-triggered volcanism, left catastrophic regional-global imprints on sea level, climate, marine anoxia and tectonic stability that connected the P-Tr crisis across terrestrial and marine realms worlwide.     

Ocean Chemistry Revealed by Mineralogical and Geochemical Evidence at the Permian–Triassic Mass Extinction, Offshore the Persian Gulf, Iran

The Upper Permian Dalan Formation and the Lower Triassic Kangan Formation in the Persian Gulf area are mainly composed of shallow marine facies limestone and dolomite. Two subsurface-cored intervals were investigated in order to understand the original mineralogy and paleoceanic conditions. The decreasing trend of Sr concentration in these deposits shows that aragonite was precipitated during the Late Permian and then gradually changed to calcite toward the Permian–Triassic boundary (PTB). The dissolution rate of aragonite decreased from 60 m below the PTB toward the boundary, with the only exception at 10 m below the Permian-Triassic Boundary (PTB) due to the Permian–Triassic unconformity in this region. The increasing trend of Mg/Ca ratio in a global scale at the end-Permian time shows that the interpreted variation of mineralogy does not result from the change of this ratio. The increasing pCO2 and decreasing pH are considered to be the main controlling factors. The increase of Ca2+ at the end-Permian time due to the input of meteoric waters is too little to fully compensate this effect. A local maximum of the Si content just at the PTB confirms the input of runoff waters.     

Stratigraphy, biostratigraphy and C-isotopes of the Permian–Triassic non-marine sequence at Dalongkou and Lucaogou, Xinjiang Province, China

Measured lithostratigraphic sections of the classic Permian–Triassic non-marine transitional sequences covering the upper Quanzijie, Wutonggou, Guodikeng and lower Jiucaiyuan Formations at Dalongkou and Lucaogou, Xinjiang Province, China are presented. These measured sections form the framework and reference sections for a range of multi-disciplinary studies of the P–T transition in this large ancient lake basin, including palynostratigraphy, vertebrate biostratigraphy, chemostratigraphy and magnetostratigraphy. The 121 m thick Wutonggou Formation at Dalongkou includes 12 sandstone units ranging in thickness from 0.5 to 10.5 m that represent cyclical coarse terrigenous input to the lake basin during the Late Permian. The rhythmically-bedded, mudstone-dominated Guodikeng Formation is 197 m and 209 m thick on the north and south limbs of the Dalongkou anticline, respectively, and 129 m thick at Lucaogou. Based on limited palynological data, the Permian–Triassic boundary was previously placed approximately 50 m below the top of this formation at Dalongkou. This boundary does not coincide with any mappable lithologic unit, such as the basal sandstones of the overlying Jiucaiyuan Formation, assigned to the Early Triassic. The presence of multiple organic δ¹³C-isotope excursions, mutant pollen, and multiple algal and conchostracan blooms in this formation, together with Late Permian palynomorphs, suggests that the Guodikeng Formation records multiple climatic perturbation signals representing environmental stress during the late Permian mass extinction interval. The overlap between the vertebrates Dicynodon and Lystrosaurus in the upper part of this formation, and the occurrence of late Permian spores and the latest Permian to earliest Triassic megaspore Otynisporites eotriassicus is consistent with a latest Permian age for at least part of the Guodikeng Formation. Palynostratigrahic placement of the Permian–Triassic boundary in the Junggar Basin remains problematic because key miospore taxa, such as Aratrisporites spp. are not present. Palynomorphs from the Guodikeng are assigned to two assemblages; the youngest, from the upper 100 m of the formation (and the overlying Jiucaiyuan Formation), contains both typical Permian elements and distinctive taxa that elsewhere are known from the Early Triassic of Canada, Greenland, Norway, and Russia. The latter include spores assigned to Pechorosporites disertus, Lundbladispora foveota, Naumovaspora striata, Decussatisporites mulstrigatus and Leptolepidites jonkerii. While the presence of Devonian and Carboniferous spores and Early Permian pollen demonstrate reworking is occurring in the Guodikeng assemblages, the sometimes common occurrence of Scutasporites sp. cf. Scutasporites unicus, and other pollen, suggests that the Late Permian elements are in place, and that the upper assemblage derives from a genuine transitional flora of Early Triassic aspect. In the Junggar Basin, biostratigraphic data and magnetostratigraphic data indicate that the Permian–Triassic boundary (GSSP Level) is in the middle to upper Guodikeng Formation and perhaps as high as the formational contact with the overlying Jiucaiyuan Formation.     

敏感性分析在烃源岩成熟度史模拟中的应用——以川东北地区普光5井古生界海相烃源岩为例

通过分析输人模型的参数对输出结果的影响,可以确定影响烃源岩成熟度史模拟的敏感性参数.本文应用Easy% Ro化学动力学模型,以普光5井为例,对川东北地区各期构造运动剥蚀厚度、古地表温度和古地温梯度进行了相关的敏感性分析.分析结果表明:研究区下寒武统、下志留统、下二叠统和上二叠统烃源岩现今成熟度状态完全受控于燕山运动晚幕...     

Organic carbon content and carbon isotope variations across the Permo-Triassic boundary in the Gartnerkofel-1 borehole,Carnic Alps,Austria

The Gartnerkofel borehole is one of the most thoroughly studied and described Permo-Triassic sections in the world. Detailed bulk organic carbon isotope studies show a negative base shift from ? 24‰ to ? 28‰ in the Latest Permian which latter value persists into the Earliest Triassic after which it decreases slightly to ? 26‰. Two strongly negative peaks of > ? 38‰ in the Latest Permian and a lesser peak of ? 31‰ in the Early Triassic are too negative to be due to a greater proportion of more negative organic matter and must be due to very negative methane effects. The overall change to more negative values across the Bulla/Tesero boundary fits the relative rise in sea level for this transition based on the facies changes. A positive shift in organic carbon isotope values at the Late Permian Event Horizon may be due to an increase in land-derived organic detritus at this level—a feature shown by all Tethyan Permo-Triassic boundary sections though these other sections do not have the same values. Carbonate carbon isotope trends are similar in all sections dropping by 2–3 units across the Permo-Triassic boundary. Gartnerkofel carbonate oxygen values are surprisingly, considering the ubiquitous dolomitization, compatible with values elsewhere and indicate reasonable tropical temperatures of 60 °C in the Latest Permian sabkhas to 20–40 °C in the overlying marine transition beds. Increased land-derived input at the Late Permian Event Horizon may be due to offshore transport by tsunamis whose deposits have been recognized in India at this level.     

Stratigraphy,biostratigraphy and C-isotopes of the Permian–Triassic non-marine sequence at Dalongkou and Lucaogou,Xinjiang Province,China

Measured lithostratigraphic sections of the classic Permian–Triassic non-marine transitional sequences covering the upper Quanzijie, Wutonggou, Guodikeng and lower Jiucaiyuan Formations at Dalongkou and Lucaogou, Xinjiang Province, China are presented. These measured sections form the framework and reference sections for a range of multi-disciplinary studies of the P–T transition in this large ancient lake basin, including palynostratigraphy, vertebrate biostratigraphy, chemostratigraphy and magnetostratigraphy. The 121 m thick Wutonggou Formation at Dalongkou includes 12 sandstone units ranging in thickness from 0.5 to 10.5 m that represent cyclical coarse terrigenous input to the lake basin during the Late Permian. The rhythmically-bedded, mudstone-dominated Guodikeng Formation is 197 m and 209 m thick on the north and south limbs of the Dalongkou anticline, respectively, and 129 m thick at Lucaogou. Based on limited palynological data, the Permian–Triassic boundary was previously placed approximately 50 m below the top of this formation at Dalongkou. This boundary does not coincide with any mappable lithologic unit, such as the basal sandstones of the overlying Jiucaiyuan Formation, assigned to the Early Triassic. The presence of multiple organic δ¹³C-isotope excursions, mutant pollen, and multiple algal and conchostracan blooms in this formation, together with Late Permian palynomorphs, suggests that the Guodikeng Formation records multiple climatic perturbation signals representing environmental stress during the late Permian mass extinction interval. The overlap between the vertebrates Dicynodon and Lystrosaurus in the upper part of this formation, and the occurrence of late Permian spores and the latest Permian to earliest Triassic megaspore Otynisporites eotriassicus is consistent with a latest Permian age for at least part of the Guodikeng Formation. Palynostratigrahic placement of the Permian–Triassic boundary in the Junggar Basin remains problematic because key miospore taxa, such as Aratrisporites spp. are not present. Palynomorphs from the Guodikeng are assigned to two assemblages; the youngest, from the upper 100 m of the formation (and the overlying Jiucaiyuan Formation), contains both typical Permian elements and distinctive taxa that elsewhere are known from the Early Triassic of Canada, Greenland, Norway, and Russia. The latter include spores assigned to Pechorosporites disertus, Lundbladispora foveota, Naumovaspora striata, Decussatisporites mulstrigatus and Leptolepidites jonkerii. While the presence of Devonian and Carboniferous spores and Early Permian pollen demonstrate reworking is occurring in the Guodikeng assemblages, the sometimes common occurrence of Scutasporites sp. cf. Scutasporites unicus, and other pollen, suggests that the Late Permian elements are in place, and that the upper assemblage derives from a genuine transitional flora of Early Triassic aspect. In the Junggar Basin, biostratigraphic data and magnetostratigraphic data indicate that the Permian–Triassic boundary (GSSP Level) is in the middle to upper Guodikeng Formation and perhaps as high as the formational contact with the overlying Jiucaiyuan Formation.     

The terminal Permian in European Russia: Vyaznikovian Horizon,Nedubrovo Member,and Permian–Triassic boundary

The comprehensive analysis of the data obtained on terrestrial vertebrata, ostracods, entomologic fauna, megaflora, and microflora in deposits of the Vyaznikovian Horizon and Nedubrovo Member, as well as the paleomagnetic data measured in enclosing rocks, confirms heterogeneity of these deposits. Accordingly, it is necessary to distinguish these two stratons in the terminal Permian of the East European Platform. The combined sequence of Triassic–Permian boundary deposits in the Moscow Syneclise, which is considered to be the most complete sequence in the East European Platform, is as follows (from bottom upward): Vyatkian deposits; Vyaznikovian Horizon, including Sokovka and Zhukovo members; Nedubrovo Member (Upper Permian); Astashikha and Ryabi members of the Vokhmian Horizon (Lower Triassic). None of the sequences of Permian–Triassic boundary deposits known in the area of study characterizes this sequence in full volume. In the north, the Triassic deposits are underlain by the Nedubrovo Member; in the south (the Klyazma River basin), the sections are underlain by the Vyaznikovian Horizon. The Permian–Triassic boundary adopted in the General Stratigraphic Scale of Russia for continental deposits of the East European platform (the lower boundary of the Astashikha Member) is more ancient than the one adopted in the International Stratigraphic Chart. The same geological situation is observed in the German Basin and other localities where Triassic continental deposits are developed. The ways of solving this problem are discussed in this article.     

Facies and evolution of the carbonate factory during the Permian–Triassic crisis in South Tibet,China

The nature of Phanerozoic carbonate factories is strongly controlled by the composition of carbonate‐producing faunas. During the Permian–Triassic mass extinction interval there was a major change in tropical shallow platform facies: Upper Permian bioclastic limestones are characterized by benthic communities with significant richness, for example, calcareous algae, fusulinids, brachiopods, corals, molluscs and sponges, while lowermost Triassic carbonates shift to dolomicrite‐dominated and bacteria‐dominated microbialites in the immediate aftermath of the Permian–Triassic mass extinction. However, the spatial–temporal pattern of carbonates distribution in high latitude regions in response to the Permian–Triassic mass extinction has received little attention. Facies and evolutionary patterns of a carbonate factory from the northern margin of peri‐Gondwana (palaeolatitude ca 40°S) are presented here based on four Permian–Triassic boundary sections that span proximal, inner to distal, and outer ramp settings from South Tibet. The results show that a cool‐water bryozoan‐dominated and echinoderm‐dominated carbonate ramp developed in the Late Permian in South Tibet. This was replaced abruptly, immediately after the Permian–Triassic mass extinction, by a benthic automicrite factory with minor amounts of calcifying metazoans developed in an inner/middle ramp setting, accompanied by transient subaerial exposure. Subsequently, an extensive homoclinal carbonate ramp developed in South Tibet in the Early Triassic, which mainly consists of homogenous dolomitic lime mudstone/wackestone that lacks evidence of metazoan frame‐builders. The sudden transition from a cool‐water, heterozoan dominated carbonate ramp to a warm‐water, metazoan‐free, homoclinal carbonate ramp following the Permian–Triassic mass extinction was the result of the combination of the loss of metazoan reef/mound builders, rapid sea‐level changes across Permian–Triassic mass extinction and profound global warming during the Early Triassic.     

Geochronology and Chemistry of the Ophiolite in the Southern Tianshan,Uzbekistan

The ophiolite in the southern Tianshan, Uzbekistan, is interrupted distributed along the northern border (NW‐trending) of the Nuratau Mountain. It's the suture zone between kyzylkum‐Alai and Kazakhstan paleo‐continents. In order to study the tectonic evolution of the Turkestan ocean during the Paleozoic, we present zircon U‐Pb ages, major element, trace element data for rocks from the ophiolite in the Nuratau segment. The ophiolite comprises the rock blocks of serpentinite, altered basalt, allalinite, altered diabase, pillowed basalt, limestone, etc and the matrix of quartz schist, forming the grid structure. The matrix suffers strong deformation and deterioration, while the mylonitization occurred in the western outcrop. New LA‐ICP‐MS zircon U‐Pb ages were determined for six magmatic rock blocks and two quartz schist matrix and these ages confirm the presence of Late Devonian‐Early Permian (ca. 411 to 294 Ma). Five zircon grains from greenschist facies metamorphic basic rock yielded a group minimum weighted mean age of 226 Ma, interpreted as the result of Late Triassic thermal event. The apex of zircon ages for 2 quartz schist is about 450 Ma (Late Ordovician). That indicates sedimentary material from the Late Ordovician. The basalt (SiO2=48.15‐49.93%) are Na‐enriched (average Na2O=2.32‐4.02%), with high HREE/LREE ratios (average=4.93), Weak positive anomalies (average Eu*/Eu=1.02) and convex‐type mantle‐normalized immobile trace elements patterns, which are similar to the geochemical characteristics of Alkaline Ocean island basalt (OIB) and subalkaline Oceanic plateau basalt (OPB). This ophiolite is characterized by Mantle (serpentinite) and Ocean crust (altered basalt, allalinite, pillowed basalt), formed in Early Devonian at the latest. During the evolution of the Turkestan ocean, the growth of OIB and OPB, Ordovician provided a large amount of sedimentary material. The earliest start time of the ocean closed and paleo‐continents assembly is the Early Permian. Afterward, a Late Triassic thermal event occurred on a region scale and is recorded by metamorphic zircon.     

Late Olenekian Radiolarians from Bedded Chert of Ashio Terrane, Northeast Japan,and Faunal Turnovers in Western Panthalassa during Early Triassic

Late Olenekian assemblages in the western Panthalassa have been recovered from bedded radiolarian chert sequences of an accretionary complex, the Ashio belt. These faunas are documented and considered in terms of radiolarian diversity and faunal turnover during the latest Permian to Middle Triassic time. The fauna includes 30 radiolarians belonging to Spumellaria or Entactinaria, with two relicts from the Late Permian. This late Olenekian fauna is markedly different from Permian and Asisian faunas, respectively, and is herein named the Minowa fauna. Study of the literaure indicates that radiolarian provinces were significantly disconnected between the western Panthalassa and eastern Tethys during late Olenekian time. Furthermore, 121 of 143 species disappeared during late Olenekian time, and in turn 118 new species appeared in the western Panthalassa around the Olenekian-Anisian boundary. It is concluded that faunal turnover occurred at least three times between the latest Permian and Middle Triassic.The first turnover is the Poalaozoie-type radiolarian extinction at the Permain-Triassic boundary,the second is the diversification of spheroidal Spumellaria and Entactinaria between early and late Olenekian time, and the third is a faunal turnover from the Minowa fauna to the true Mesozoic-type radiolarian famas that are characterized by mulit0segmented Nassellaria.     

Palaeoenvironmental significance of Late Permian palaeosols in the South‐Eastern Iberian Ranges,Spain

The Late Permian (Wuchiapingian) Alcotas Formation in the SE Iberian Ranges consists of one red alluvial succession where abundant soil profiles developed. Detailed petrographical and sedimentological studies in seven sections of the Alcotas Formation allow six different types of palaeosols, with distinctive characteristics and different palaeogeographical distribution, to be distinguished throughout the South‐eastern Iberian Basin. These characteristics are, in turn, related to topographic, climatic and tectonic controls. The vertical distribution of the palaeosols is used to differentiate the formation in three parts from bottom to top showing both drastic and gradual vertical upwards palaeoenvironmental changes in the sections. Reconstruction of palaeoenvironmental conditions based on palaeosols provides evidence for understanding the events that occurred during the Late Permian, some few millions of years before the well‐known Permian‐Triassic global crisis.     

滇黔桂盆地及其邻区二叠系与三叠系之交的淹没不整合面

滇黔桂盆地及其邻区在晚二叠世长兴晚期发生快速海侵,导致了第I幕淹没事件,研究区内的连陆台地大部分被淹没,形成大隆组硅质泥页岩系凝缩段地层和其下相对局限发育的第I幕淹没不整合面;在早三叠世印度初期发生更大规模的快速海侵,导致更大的第Ⅱ幕淹没事件,研究区内的连陆台地和孤立台地均被淹没,形成罗楼组、马脚岭组等同时异相沉积地层底部的钙质泥页岩系凝缩段地层和其下全区普遍发育的较为典型的第Ⅱ幕淹没不整合面。这两幕淹没不整合面合称二叠系与三叠系之交的淹没不整合面,它们是三级层序SQ₂₆的底界面,具有明显的穿时性;凝缩段是它们的主要标志。中二叠世冷坞末期和晚二叠世吴家坪末期的两幕东吴运动导致的研究区古地理背景的重大改变对淹没不整合面的发育有重要的影响。淹没不整合面的形成与二叠纪末期发生的全球淹没事件基本同步,是全球海平面急剧上升的结果,它对研究区的石油勘探具有积极的地质意义。     

Sedimentology of the continental end‐Permian extinction event in the Sydney Basin,eastern Australia

Upper Permian to Lower Triassic coastal plain successions of the Sydney Basin in eastern Australia have been investigated in outcrop and continuous drillcores. The purpose of the investigation is to provide an assessment of palaeoenvironmental change at high southern palaeolatitudes in a continental margin context for the late Permian (Lopingian), across the end‐Permian Extinction interval, and into the Early Triassic. These basins were affected by explosive volcanic eruptions during the late Permian and, to a much lesser extent, during the Early Triassic, allowing high‐resolution age determination on the numerous tuff horizons. Palaeobotanical and radiogenic isotope data indicate that the end‐Permian Extinction occurs at the top of the uppermost coal bed, and the Permo‐Triassic boundary either within an immediately overlying mudrock succession or within a succeeding channel sandstone body, depending on locality due to lateral variation. Late Permian depositional environments were initially (during the Wuchiapingian) shallow marine and deltaic, but coastal plain fluvial environments with extensive coal‐forming mires became progressively established during the early late Permian, reflected in numerous preserved coal seams. The fluvial style of coastal plain channel deposits varies geographically. However, apart from the loss of peat‐forming mires, no significant long‐term change in depositional style (grain size, sediment‐body architecture, or sediment dispersal direction) was noted across the end‐Permian Extinction (pinpointed by turnover of the palaeoflora). There is no evidence for immediate aridification across the boundary despite a loss of coal from these successions. Rather, the end‐Permian Extinction marks the base of a long‐term, progressive trend towards better‐drained alluvial conditions into the Early Triassic. Indeed, the floral turnover was immediately followed by a flooding event in basinal depocentres, following which fluvial systems similar to those active prior to the end‐Permian Extinction were re‐established. The age of the floral extinction is constrained to 252.54 ± 0.08 to 252.10 ± 0.06 Ma by a suite of new Chemical Abrasion Isotope Dilution Thermal Ionization Mass Spectrometry U‐Pb ages on zircon grains. Another new age indicates that the return to fluvial sedimentation similar to that before the end‐Permian Extinction occurred in the basal Triassic (prior to 251.51 ± 0.14 Ma). The character of the surface separating coal‐bearing pre‐end‐Permian Extinction from coal‐barren post‐end‐Permian Extinction strata varies across the basins. In basin‐central locations, the contact varies from disconformable, where a fluvial channel body has cut down to the level of the top coal, to conformable where the top coal is overlain by mudrocks and interbedded sandstone–siltstone facies. In basin‐marginal locations, however, the contact is a pronounced erosional disconformity with coarse‐grained alluvial facies overlying older Permian rocks. There is no evidence that the contact is everywhere a disconformity or unconformity.     

陆相二叠一三叠系界线划分和事件

我国陆相二叠—三叠系界线的划分主要依据古脊椎动物,孢粉,双壳类、介形虫和古植物等.这些化石组合特征在界线附近都有明显的变化.这种变化不仅可以用来划分界线,而且结合在界线附近其它非生物（沉积物的粒度和颜色等）的异常变化,可以看出在二叠—三叠纪之交曾发生过某种事件.     

鄂尔多斯盆地南缘上二叠统——中下三叠统地球化学特征及其古气候、古环境指示意义

为探索陆相湖泊环境记录中二叠纪—三叠纪之交古气候演化的信息,以鄂尔多斯盆地南缘陕西铜川石川河剖面上二叠统石千峰组(P3s)和三叠系的刘家沟组(T1l)、和尚沟组(T1h)、纸坊组(T2z)为研究对象,对界面上下地层开展了系统的矿物学、岩石学和地球化学研究。通过主量和微量元素、碳氧同位素以及TOC测试对古盐度、古氧化还原环境和古气候演化规律进行分析。测试结果显示在二叠系—三叠系(P/T)界线附近主、微量元素和碳、氧同位素发生较明显的变化,气候环境代用化学指标的波动指示了从晚二叠世至早中三叠世鄂尔多斯盆地的古气候、古环境的变化。研究结果表明上二叠统石千峰组形成于河流-三角洲沉积环境,氧化程度相对低,古气候相对温暖湿润;下三叠统刘家沟组与和尚沟组的紫红色砂泥岩代表水体较浅的河流-三角洲相,强氧化环境,气候干旱炎热;而到中三叠统纸坊组沉积期,湖平面上升,元素的迁移作用加强,氧化程度变弱,气温降低,气候转为半干旱半湿润气候。碳同位素分析结果显示,鄂尔多斯盆地陆相P/T界线上δ^13CPDB存在显著负偏,与全球范围内的海相P/T界线具有一致性,说明在华北地台陆相P/T界线上同样存在气候突变和生物灭绝等重大地质事件的沉积记录,与海相地层可对比。     

Accumulation and Reformation of Silurian Reservoir in the Northern Tarim Basin

Silurian sandstone in Tarim Basin has good reservoir properties and active oil and gas shows, especially thick widely-distributed bituminous sandstone. Currently, the Silurian was found containing both bitumen and conventional reservoirs, with petroleum originating from terrestrial and marine source rocks. The diversity of their distribution was the result of "three sources, three stages" accumulation and adjustment processes. "Three sources" refers to two sets of marine rocks in Cambrian and Middle-Upper Ordovician, and a set of terrestrial rock formed in Triassic in the Kuqa depression. "Three stages" represents three stages of accumulation, adjustment and reformation occurring in Late Caledonian, Late Hercynian and Late Himalayan, respectively. The study suggests that the Silurian bitumen is remnants of oil generated from Cambrian and Ordovician source rocks and accumulated in the sandstone reservoir during Late Caledonian-Early Hercynian and Late Hercynian stages, and then damaged by the subsequent two stages of tectonic uplift movements in Early Hercynian and Pre-Triassic. The authors presumed that the primary paleo-reservoirs formed during these two stages might be preserved in the Silurian in the southern deep part of the Tabei area. Except for the Yingmaili area where the Triassic terrestrial oil was from the Kuqa Depression during Late Himalayan Stage, all movable oil reservoirs originated from marine sources. They were secondary accumulations from underlying Ordovician after structure reverse during the Yanshan-Himalayan stage. Oil/gas shows mixed-source characteristics, and was mainly from Middle-Upper Ordovician. The complexity and diversity of the Silurian marine primary properties were just defined by these three stages of oil-gas charging and tectonic movements in the Tabei area.