Earthquakes and tsunamis are devastating geohazards with significant societal impacts. Most recent occurrences have shown that their impact on the stability of nations–societies and the world geopolitics is immense, potentially triggering a tipping point for a major downturn in the global economy. This Special Publication presents the most current information on the causes and effects of some of the modern and historical earthquake–tsunami events, and effective practices of risk assessment–disaster management, implemented by various governments, international organizations and intergovernmental agencies. Findings reported here show that the magnitude of human casualties and property loss resulting from earthquakes–tsunamis are highly variable around the globe, and that increased community, national and global resilience is significant to empower societal preparedness for such geohazards. It is clear that all stakeholders, including scientists, policymakers, governments, media and world organizations must work together to disseminate accurate, objective and timely information on geohazards, and to develop effective legislation for risk reduction and realistic hazard mitigation–management measures in our globally connected world of today.
{"title":"About this title - Characterization of Modern and Historical Seismic–Tsunamic Events, and Their Global–Societal Impacts","authors":"Y. Dilek, Y. Ogawa, Y. Okubo","doi":"10.1144/sp501","DOIUrl":"https://doi.org/10.1144/sp501","url":null,"abstract":"Earthquakes and tsunamis are devastating geohazards with significant societal impacts. Most recent occurrences have shown that their impact on the stability of nations–societies and the world geopolitics is immense, potentially triggering a tipping point for a major downturn in the global economy. This Special Publication presents the most current information on the causes and effects of some of the modern and historical earthquake–tsunami events, and effective practices of risk assessment–disaster management, implemented by various governments, international organizations and intergovernmental agencies. Findings reported here show that the magnitude of human casualties and property loss resulting from earthquakes–tsunamis are highly variable around the globe, and that increased community, national and global resilience is significant to empower societal preparedness for such geohazards. It is clear that all stakeholders, including scientists, policymakers, governments, media and world organizations must work together to disseminate accurate, objective and timely information on geohazards, and to develop effective legislation for risk reduction and realistic hazard mitigation–management measures in our globally connected world of today.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"26 1","pages":"NP - NP"},"PeriodicalIF":0.0,"publicationDate":"2021-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90518918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Weimu Xu, J. Weijers, M. Ruhl, E. Idiz, H. Jenkyns, J. Riding, O. Gorbanenko, S. Hesselbo
Abstract The organic-rich upper Lower Jurassic Da'anzhai Member (Ziliujing Formation) of the Sichuan Basin, China is the first stratigraphically well-constrained lacustrine succession associated with the Toarcian Oceanic Anoxic Event (T-OAE; c. 183 Ma). The expansion of the palaeo-Sichuan mega-lake, probably one of the most extensive freshwater systems to have existed on the planet, is marked by large-scale lacustrine organic productivity and carbon burial during the T-OAE, possibly owing to intensified hydrological cycling and nutrient supply. New molecular biomarker and organic petrographical analyses, combined with bulk organic and inorganic geochemical and palynological data, are presented here, providing insight into aquatic productivity, land-plant biodiversity and terrestrial ecosystem evolution in continental interiors during the T-OAE. We show that lacustrine algal growth during the T-OAE accounted for a significant organic-matter flux to the lakebed in the palaeo-Sichuan mega-lake. Lacustrine water-column stratification during the T-OAE facilitated the formation of dysoxic–anoxic conditions at the lake bottom, favouring organic-matter preservation and carbon sequestration into organic-rich black shales in the Sichuan Basin. We attribute the palaeo-Sichuan mega-lake expansion to enhanced hydrological cycling in a more vigorous monsoonal climate in the hinterland during the T-OAE greenhouse.
{"title":"Molecular and petrographical evidence for lacustrine environmental and biotic change in the palaeo-Sichuan mega-lake (China) during the Toarcian Oceanic Anoxic Event","authors":"Weimu Xu, J. Weijers, M. Ruhl, E. Idiz, H. Jenkyns, J. Riding, O. Gorbanenko, S. Hesselbo","doi":"10.1144/SP514-2021-2","DOIUrl":"https://doi.org/10.1144/SP514-2021-2","url":null,"abstract":"Abstract The organic-rich upper Lower Jurassic Da'anzhai Member (Ziliujing Formation) of the Sichuan Basin, China is the first stratigraphically well-constrained lacustrine succession associated with the Toarcian Oceanic Anoxic Event (T-OAE; c. 183 Ma). The expansion of the palaeo-Sichuan mega-lake, probably one of the most extensive freshwater systems to have existed on the planet, is marked by large-scale lacustrine organic productivity and carbon burial during the T-OAE, possibly owing to intensified hydrological cycling and nutrient supply. New molecular biomarker and organic petrographical analyses, combined with bulk organic and inorganic geochemical and palynological data, are presented here, providing insight into aquatic productivity, land-plant biodiversity and terrestrial ecosystem evolution in continental interiors during the T-OAE. We show that lacustrine algal growth during the T-OAE accounted for a significant organic-matter flux to the lakebed in the palaeo-Sichuan mega-lake. Lacustrine water-column stratification during the T-OAE facilitated the formation of dysoxic–anoxic conditions at the lake bottom, favouring organic-matter preservation and carbon sequestration into organic-rich black shales in the Sichuan Basin. We attribute the palaeo-Sichuan mega-lake expansion to enhanced hydrological cycling in a more vigorous monsoonal climate in the hinterland during the T-OAE greenhouse.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"18 1","pages":"335 - 357"},"PeriodicalIF":0.0,"publicationDate":"2021-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89651140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. O'Keefe, F. Marret, P. Osterloff, M. Pound, L. Shumilovskikh
Abstract Here we introduce the volume Applications of Non-Pollen Palynomorphs: from Palaeoenvironmental Reconstructions to Biostratigraphy. The study of non-pollen palynomorphs (NPPs) has a long and rich history that is interwoven with that of pollen-based studies. NPPs are among the oldest fossils on record and are instrumental in determining the origin and evolution of life, as well as studying origination and extinction events prior to the origin of pollen-producing angiosperms. This new volume on NPPs provides an up-to-date and seminal overview of the subject, linking deep-time and Quaternary study of the subject for the first time.
{"title":"Why a new volume on non-pollen palynomorphs?","authors":"J. O'Keefe, F. Marret, P. Osterloff, M. Pound, L. Shumilovskikh","doi":"10.1144/SP511-2021-83","DOIUrl":"https://doi.org/10.1144/SP511-2021-83","url":null,"abstract":"Abstract Here we introduce the volume Applications of Non-Pollen Palynomorphs: from Palaeoenvironmental Reconstructions to Biostratigraphy. The study of non-pollen palynomorphs (NPPs) has a long and rich history that is interwoven with that of pollen-based studies. NPPs are among the oldest fossils on record and are instrumental in determining the origin and evolution of life, as well as studying origination and extinction events prior to the origin of pollen-producing angiosperms. This new volume on NPPs provides an up-to-date and seminal overview of the subject, linking deep-time and Quaternary study of the subject for the first time.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"13 1","pages":"1 - 11"},"PeriodicalIF":0.0,"publicationDate":"2021-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89302869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Using forensic soil science and forensic geology as trace evidence and searches for burials is the theme of the papers in this Special Publication. The concept and design of this volume was initially established by the International Union of Geological Sciences, Initiative on Forensic Geology, which successfully brought together forensic geologists, forensic soil scientists, police officers and law enforcement agents in the investigation of crimes. In this introductory paper a brief overview is provided of the developments in interdisciplinary knowledge exchange with use of soil and geological materials (known as ‘earth materials’) in the search for burials and the provision of trace evidence. The aim is to provide background information on the role and value of understanding ‘earth materials’ ranging from the landscape scale, to the crime scene through to microscopic scale investigations to support law enforcement agencies in solving criminal, environmental, serious and organized crime, and terrorism. In this connection, recent advances in field and laboratory methods are highlighted. Finally, the 20 papers in the volume are briefly introduced and these include a diversity of global operational case studies that involve collection and analysis of earth material from crime scenes and searches for homicide graves and other buried targets.
{"title":"An introduction to forensic soil science and forensic geology: a synthesis","authors":"R. Fitzpatrick, L. Donnelly","doi":"10.1144/SP492-2021-81","DOIUrl":"https://doi.org/10.1144/SP492-2021-81","url":null,"abstract":"Abstract Using forensic soil science and forensic geology as trace evidence and searches for burials is the theme of the papers in this Special Publication. The concept and design of this volume was initially established by the International Union of Geological Sciences, Initiative on Forensic Geology, which successfully brought together forensic geologists, forensic soil scientists, police officers and law enforcement agents in the investigation of crimes. In this introductory paper a brief overview is provided of the developments in interdisciplinary knowledge exchange with use of soil and geological materials (known as ‘earth materials’) in the search for burials and the provision of trace evidence. The aim is to provide background information on the role and value of understanding ‘earth materials’ ranging from the landscape scale, to the crime scene through to microscopic scale investigations to support law enforcement agencies in solving criminal, environmental, serious and organized crime, and terrorism. In this connection, recent advances in field and laboratory methods are highlighted. Finally, the 20 papers in the volume are briefly introduced and these include a diversity of global operational case studies that involve collection and analysis of earth material from crime scenes and searches for homicide graves and other buried targets.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"42 1","pages":"1 - 32"},"PeriodicalIF":0.0,"publicationDate":"2021-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90569986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Northern Indian Shield and the western Himalaya have an impressive record of mafic magmatism. The Aravalli Craton preserved 2.3 Ga komatiitic (picritic) and 2.1–1.8 Ga tholeiities. Gwalior and Betul belts preserved 2.1 and 1.5–1.2 Ga tholeiites, respectively. Western Himalaya has preserved 2.1–1.8 Ga tholeiites in Garhwal and Himachal regions. Studied rocks depict enriched rare earth elements, large ion lithophile elements and depleted high field strength elements. Whereas komatiites/picrites represent higher degrees of partial melting (c. 35–40%) at higher temperatures (c. 1500°C), tholeiites represent lower degrees of partial melting (c. 10%) at lower temperatures (c. 1200°C). Our results indicate interaction of mantle plume with variably enriched subcontinental lithospheric mantle sources, causing generation of these varied magmatic suites of rocks. Whereas the higher temperature komatiitic/picritic melts from the Aravalli region appear to have been generated closer to the plume head, the lower temperature tholeiitic melts from the shield region and western Himalaya were generated towards the plume margins. Different terrains of the study have undergone plume tectonics causing the development of the rift valleys. The majority of these developed into aulacogens, except for the Aravalli basin, which developed into deeper marine facies.
{"title":"Petrogenesis and tectonic settings of Proterozoic mafic magmatism from the northern Indian Shield and the Himalaya: possible role for interaction of mantle plume with the subcontinental lithospheric mantle","authors":"T. Ahmad, I. Yousuf, H. Chauhan","doi":"10.1144/SP518-2021-14","DOIUrl":"https://doi.org/10.1144/SP518-2021-14","url":null,"abstract":"Abstract Northern Indian Shield and the western Himalaya have an impressive record of mafic magmatism. The Aravalli Craton preserved 2.3 Ga komatiitic (picritic) and 2.1–1.8 Ga tholeiities. Gwalior and Betul belts preserved 2.1 and 1.5–1.2 Ga tholeiites, respectively. Western Himalaya has preserved 2.1–1.8 Ga tholeiites in Garhwal and Himachal regions. Studied rocks depict enriched rare earth elements, large ion lithophile elements and depleted high field strength elements. Whereas komatiites/picrites represent higher degrees of partial melting (c. 35–40%) at higher temperatures (c. 1500°C), tholeiites represent lower degrees of partial melting (c. 10%) at lower temperatures (c. 1200°C). Our results indicate interaction of mantle plume with variably enriched subcontinental lithospheric mantle sources, causing generation of these varied magmatic suites of rocks. Whereas the higher temperature komatiitic/picritic melts from the Aravalli region appear to have been generated closer to the plume head, the lower temperature tholeiitic melts from the shield region and western Himalaya were generated towards the plume margins. Different terrains of the study have undergone plume tectonics causing the development of the rift valleys. The majority of these developed into aulacogens, except for the Aravalli basin, which developed into deeper marine facies.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"8 1","pages":"197 - 225"},"PeriodicalIF":0.0,"publicationDate":"2021-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73119739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
W. Davis, M. Collins, T. Rooney, Eric Brown, C. Stein, S. Stein, R. Moucha
Abstract Continental flood basalt provinces (CFBPs) are large igneous features formed by the extrusion of massive amounts of lavas that require significant evolution within the lithosphere. Although sequential lava flows are effective probes of magmatic systems, CFBPs are typically poorly preserved. We focus on lava flows from the well-preserved 1.1 Ga Keweenawan CFBP that erupted within the Midcontinent Rift System. We present a new geochemical, petrographic, and stratigraphic synthesis from the Main stage Portage Lake Volcanics (PLV). Flow-by-flow analysis of the PLV reveals that major element behaviour is decoupled from trace element behaviour; MgO exhibits limited variability, while compatible and incompatible trace elements deviate from high to low concentrations throughout the sequence. The concentrations of incompatible trace elements slightly decrease from the base of the sequence to the top. We investigate these observations by applying a recharge, evacuation, assimilation and fractional crystallization model to geochemical and petrographic data. Our modelling demonstrates a magmatic system experiencing increased evacuation rates while fractionation and assimilation rates decrease, indicating an increase in magmatic flux. The outcome of this modelling is a progressively more efficient magma system within the PLV. This study highlights the utility of joint petrographic and geochemical interpretation in constraining CFBP magma evolution.
大陆洪水玄武岩省(cfbp)是由大量熔岩挤压形成的大型火成岩特征，需要在岩石圈内进行重大演化。虽然序贯熔岩流是岩浆系统的有效探针，但cfbp通常保存较差。我们重点研究了保存完好的1.1 Ga Keweenawan CFBP在中大陆裂谷系喷发的熔岩流。本文提出了一种新的地球化学、岩石学和地层学合成方法。对PLV的逐流分析表明，主元素行为与微量元素行为是分离的;MgO表现出有限的变异性，而相容和不相容的微量元素在整个序列中从高浓度到低浓度偏离。不相容微量元素的浓度从序列底部到顶部略有下降。我们通过对地球化学和岩石学数据应用补给、疏散、同化和分数结晶模型来研究这些观察结果。我们的模拟表明，岩浆系统的疏散率增加，而分馏和同化率降低，表明岩浆通量增加。这种模拟的结果是，PLV内的岩浆系统逐渐变得更加有效。该研究突出了岩石学和地球化学联合解释在制约CFBP岩浆演化中的作用。
{"title":"Geochemical, petrographic, and stratigraphic analyses of the Portage Lake Volcanics of the Keweenawan CFBP: implications for the evolution of main stage volcanism in continental flood basalt provinces","authors":"W. Davis, M. Collins, T. Rooney, Eric Brown, C. Stein, S. Stein, R. Moucha","doi":"10.1144/SP518-2020-221","DOIUrl":"https://doi.org/10.1144/SP518-2020-221","url":null,"abstract":"Abstract Continental flood basalt provinces (CFBPs) are large igneous features formed by the extrusion of massive amounts of lavas that require significant evolution within the lithosphere. Although sequential lava flows are effective probes of magmatic systems, CFBPs are typically poorly preserved. We focus on lava flows from the well-preserved 1.1 Ga Keweenawan CFBP that erupted within the Midcontinent Rift System. We present a new geochemical, petrographic, and stratigraphic synthesis from the Main stage Portage Lake Volcanics (PLV). Flow-by-flow analysis of the PLV reveals that major element behaviour is decoupled from trace element behaviour; MgO exhibits limited variability, while compatible and incompatible trace elements deviate from high to low concentrations throughout the sequence. The concentrations of incompatible trace elements slightly decrease from the base of the sequence to the top. We investigate these observations by applying a recharge, evacuation, assimilation and fractional crystallization model to geochemical and petrographic data. Our modelling demonstrates a magmatic system experiencing increased evacuation rates while fractionation and assimilation rates decrease, indicating an increase in magmatic flux. The outcome of this modelling is a progressively more efficient magma system within the PLV. This study highlights the utility of joint petrographic and geochemical interpretation in constraining CFBP magma evolution.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"7 1","pages":"67 - 100"},"PeriodicalIF":0.0,"publicationDate":"2021-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89975217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. S. Kale, Gauri Dole, Shilpa Patil Pillai, Poushali Chatterjee, Makarand S. Bodas
Abstract We review and compare morphologies from continental basaltic lavas, using examples from the Deccan Volcanic Province to compile their internal configurations and mutual associations and compare them. The mechanism of endogenous transfer of lava within an insulating (rapidly developed) crust provides an efficient mode of dispersal of the molten lava in flood basalts. The growth of the lava flow can be achieved by a single extrusion or by multiple pulses of endogenous emplacement that enable the lava to efficiently spread over large areas and thicken. We show that the morphology of a lobe manifests the response of the molten lava to several parameters (including volumetric rate of emplacement, substrate topography, viscosity, vapour loss, etc.) that govern the dynamics and cooling history of basaltic lava after it starts to spread on the surface. The lateral transition from one morphology to another within lobes of a lava flow is a testimony to the interactive response of the lava dynamics and rheology to variation in the local systems in which they were emplaced. The morphologies do not evolve as rigid partitioned categories from ‘áā and pāhoehoe lava types' but as parametric progression of interactive variations in the spreading and cooling lava. A hierarchical recognition of lobes, flows and flow fields and mapping of the morphology (and their lateral transition or continuity) combined with the stacking patterns provides the volcanological framework for a sound stratigraphic mapping of flood basalts. Such an architectural documentation of flood basalt provinces will lead to robust models of their eruptive histories.
{"title":"Morphological types in the Deccan Volcanic Province, India: implications for emplacement dynamics of continental flood basalts","authors":"V. S. Kale, Gauri Dole, Shilpa Patil Pillai, Poushali Chatterjee, Makarand S. Bodas","doi":"10.1144/SP518-2020-246","DOIUrl":"https://doi.org/10.1144/SP518-2020-246","url":null,"abstract":"Abstract We review and compare morphologies from continental basaltic lavas, using examples from the Deccan Volcanic Province to compile their internal configurations and mutual associations and compare them. The mechanism of endogenous transfer of lava within an insulating (rapidly developed) crust provides an efficient mode of dispersal of the molten lava in flood basalts. The growth of the lava flow can be achieved by a single extrusion or by multiple pulses of endogenous emplacement that enable the lava to efficiently spread over large areas and thicken. We show that the morphology of a lobe manifests the response of the molten lava to several parameters (including volumetric rate of emplacement, substrate topography, viscosity, vapour loss, etc.) that govern the dynamics and cooling history of basaltic lava after it starts to spread on the surface. The lateral transition from one morphology to another within lobes of a lava flow is a testimony to the interactive response of the lava dynamics and rheology to variation in the local systems in which they were emplaced. The morphologies do not evolve as rigid partitioned categories from ‘áā and pāhoehoe lava types' but as parametric progression of interactive variations in the spreading and cooling lava. A hierarchical recognition of lobes, flows and flow fields and mapping of the morphology (and their lateral transition or continuity) combined with the stacking patterns provides the volcanological framework for a sound stratigraphic mapping of flood basalts. Such an architectural documentation of flood basalt provinces will lead to robust models of their eruptive histories.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"43 1","pages":"341 - 396"},"PeriodicalIF":0.0,"publicationDate":"2021-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74275610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. T. Pham, J. G. Shellnutt, T. Tran, S. Denyszyn, Y. Iizuka
Abstract The Permian silicic rocks in the Phan Si Pan (PSP) Uplift area and Tu Le (TL) basin of NW Vietnam (collectively the PSP–TL region) are associated with the Emeishan large igneous province (ELIP). The Permian Muong Hum, Phu Sa Phin and Nam Xe–Tam Duong granites and Tu Le rhyolites are alkali ferroan A1-type granitic rocks, which probably formed by fractional crystallization of high-Ti basaltic magma that was contaminated by melts derived from the Neoproterozoic host rocks. Zircon U–Pb laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) geochronology yielded weighted-mean 206Pb/238U ages of 246 ± 3 to 259 ± 3 Ma for granites, and 249 ± 3 and 254 ± 2 Ma for rhyolites. This is contrasted with previously published high precision U–Pb ages, obtained using chemical abrasion–isotope dilution–thermal ionization mass spectrometry method applied on the same zircon grains, which suggests that the calculated LA–ICP–MS U–Pb ages are variably inaccurate by up to 10 Ma, although at the single-grain level dates generally agree within uncertainty. The similarity of rock texture, whole-rock geochemistry, emplacement ages and fractionation phases between the PSP–TL region and silicic rocks in the Inner Zone ELIP (i.e. Panzhihua, Binchuan) suggests they were spatially proximal before being sinistrally displaced along the Ailao Shan–Red River shear zone.
摘要越南西北部潘四潘隆起区和土乐盆地(统称PSP - TL地区)的二叠系硅质岩与峨眉山大火成岩省(ELIP)有关。二叠系Muong Hum、Phu Sa Phin、Nam hsie - tam Duong花岗岩和Tu Le流纹岩均为碱铁质a1型花岗岩，可能是受新元古代主岩熔体污染的高钛玄武质岩浆分馏结晶形成的。锆石U-Pb激光烧蚀电感耦合等离子体质谱(LA-ICP-MS)地质年代学结果显示，花岗岩的206Pb/238U加权平均年龄为246±3 ~ 259±3 Ma，流纹岩的206Pb/238U加权平均年龄为249±3 ~ 254±2 Ma。这与先前发表的高精度U-Pb年龄(使用化学磨损-同位素稀释-热电离质谱法对同一锆石颗粒进行测定)形成对比，这表明LA-ICP-MS计算的U-Pb年龄误差高达10 Ma，尽管在单粒水平上的日期通常在不确定范围内一致。PSP-TL区与ELIP内带(攀枝花、宾川)的硅质岩在岩石结构、全岩地球化学、侵位年龄和分选阶段上的相似性表明，它们在空间上是近端的，然后沿哀牢山—红河剪切带进行了纵向位移。
{"title":"Petrogenesis of silicic rocks from the Phan Si Pan–Tu Le region of the Emeishan large igneous province, northwestern Vietnam","authors":"T. T. Pham, J. G. Shellnutt, T. Tran, S. Denyszyn, Y. Iizuka","doi":"10.1144/SP518-2020-253","DOIUrl":"https://doi.org/10.1144/SP518-2020-253","url":null,"abstract":"Abstract The Permian silicic rocks in the Phan Si Pan (PSP) Uplift area and Tu Le (TL) basin of NW Vietnam (collectively the PSP–TL region) are associated with the Emeishan large igneous province (ELIP). The Permian Muong Hum, Phu Sa Phin and Nam Xe–Tam Duong granites and Tu Le rhyolites are alkali ferroan A1-type granitic rocks, which probably formed by fractional crystallization of high-Ti basaltic magma that was contaminated by melts derived from the Neoproterozoic host rocks. Zircon U–Pb laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) geochronology yielded weighted-mean 206Pb/238U ages of 246 ± 3 to 259 ± 3 Ma for granites, and 249 ± 3 and 254 ± 2 Ma for rhyolites. This is contrasted with previously published high precision U–Pb ages, obtained using chemical abrasion–isotope dilution–thermal ionization mass spectrometry method applied on the same zircon grains, which suggests that the calculated LA–ICP–MS U–Pb ages are variably inaccurate by up to 10 Ma, although at the single-grain level dates generally agree within uncertainty. The similarity of rock texture, whole-rock geochemistry, emplacement ages and fractionation phases between the PSP–TL region and silicic rocks in the Inner Zone ELIP (i.e. Panzhihua, Binchuan) suggests they were spatially proximal before being sinistrally displaced along the Ailao Shan–Red River shear zone.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"34 1","pages":"227 - 254"},"PeriodicalIF":0.0,"publicationDate":"2021-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86447906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Rodrigues, Ricardo L. Silva, J. G. Mendonça Filho, M. Reolid, D. Sadki, M. J. Comas-Rengifo, A. Goy, L. V. Duarte
Abstract In this paper, we present a detailed review of upper Pliensbachian–lower Toarcian kerogen assemblages from the southern areas of the West Tethys shelf (between Morocco and northern Spain) and demonstrate the use of the Phytoclast Group as a tracer of palaeoenvironmental changes in the early Toarcian. The kerogen assemblages in the studied sections from the southern areas of the West Tethys shelf are dominated by the Phytoclast Group and terrestrial palynomorphs, although punctual increases in amorphous organic matter, freshwater (Botryococcus) and marine microplankton (dinoflagellate cysts, acritarchs and prasinophyte algae) were observed at specific stratigraphic intervals. The opaque/non-opaque phytoclasts ratio was used to trace changes in palaeoclimate and other palaeoenvironmental parameters and reflect climate gradients associated with water availability during early Toarcian. During the Pliensbachian–Toarcian and Jenkyns events, changes in kerogen assemblages in the southern areas of the West Tethys shelf correlated with changes in the northern Tethys and Panthalassa shelf. The acceleration of the hydrological cycle associated with the aforementioned events was less intense in the northern Gondwana, southern and western Iberian basins, a reflection of the palaeogeographic position of these basins within the semi-arid climate belt when compared with the northern Iberian region and other northern areas of the West Tethys and Panthalassa shelf, inserted in winter-wet and warm temperate climate belts. Amorphous organic matter enrichment associated with the Pliensbachian–Toarcian and Jenkyns events reflects an increase in primary productivity linked with increased continental weathering, fluvial runoff and riverine organic matter, and nutrient input into marine areas, inducing water column stratification and promoting the preservation of organic matter.
{"title":"The Phytoclast Group as a tracer of palaeoenvironmental changes in the early Toarcian","authors":"B. Rodrigues, Ricardo L. Silva, J. G. Mendonça Filho, M. Reolid, D. Sadki, M. J. Comas-Rengifo, A. Goy, L. V. Duarte","doi":"10.1144/SP514-2020-271","DOIUrl":"https://doi.org/10.1144/SP514-2020-271","url":null,"abstract":"Abstract In this paper, we present a detailed review of upper Pliensbachian–lower Toarcian kerogen assemblages from the southern areas of the West Tethys shelf (between Morocco and northern Spain) and demonstrate the use of the Phytoclast Group as a tracer of palaeoenvironmental changes in the early Toarcian. The kerogen assemblages in the studied sections from the southern areas of the West Tethys shelf are dominated by the Phytoclast Group and terrestrial palynomorphs, although punctual increases in amorphous organic matter, freshwater (Botryococcus) and marine microplankton (dinoflagellate cysts, acritarchs and prasinophyte algae) were observed at specific stratigraphic intervals. The opaque/non-opaque phytoclasts ratio was used to trace changes in palaeoclimate and other palaeoenvironmental parameters and reflect climate gradients associated with water availability during early Toarcian. During the Pliensbachian–Toarcian and Jenkyns events, changes in kerogen assemblages in the southern areas of the West Tethys shelf correlated with changes in the northern Tethys and Panthalassa shelf. The acceleration of the hydrological cycle associated with the aforementioned events was less intense in the northern Gondwana, southern and western Iberian basins, a reflection of the palaeogeographic position of these basins within the semi-arid climate belt when compared with the northern Iberian region and other northern areas of the West Tethys and Panthalassa shelf, inserted in winter-wet and warm temperate climate belts. Amorphous organic matter enrichment associated with the Pliensbachian–Toarcian and Jenkyns events reflects an increase in primary productivity linked with increased continental weathering, fluvial runoff and riverine organic matter, and nutrient input into marine areas, inducing water column stratification and promoting the preservation of organic matter.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"64 1","pages":"291 - 307"},"PeriodicalIF":0.0,"publicationDate":"2021-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78242617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Boomer, P. Copestake, K. Page, J. Huxtable, Tony Loy, P. Bown, T. Dunkley Jones, M. O'Callaghan, Sarah Hawkes, David Halfacree, Henry Reay, Natalie Caughtry
Abstract This study focuses on a condensed sequence of alternating carbonate–clastic sediments of the Barrington Member, Beacon Limestone Formation (latest Pliensbachian to early Toarcian) from Somerset (SW England). Abundant ammonites confirm (apart from the absence of the Clevelandicum and Tenuicostatum ammonite subchronozones) the presence of Hawskerense Subchronozone to Fallaciosum–Bingmanni subchronozones. Well-preserved, sometimes diverse assemblages of ostracods, foraminifera, nannofossils and low-diversity dinoflagellate assemblages support the chronostratigraphic framework. Stable-isotope analyses demonstrate the presence of a carbon isotope excursion, relating to the Toarcian Oceanic Anoxic Event, within the early Toarcian. Faunal, geochemical and sedimentological evidence suggest that deposition largely took place in a relatively deep-water (subwave base), mid-outer shelf environment under a well-mixed water column. However, reduced benthic diversity, the presence of weakly laminated sediments and changes in microplankton assemblage composition within the Toarcian Oceanic Anoxic Event indicates dysoxic, but probably never anoxic, bottom-water conditions during this event. The onset of the carbon isotope excursion coincides with extinction in the nannofossils and benthos, including the disappearance of the ostracod suborder Metacopina. Faunal evidence indicates connectivity with the Mediterranean region, not previously recorded for the UK during the early Toarcian.
{"title":"Biotic and stable-isotope characterization of the Toarcian Ocean Anoxic Event through a carbonate–clastic sequence from Somerset, UK","authors":"I. Boomer, P. Copestake, K. Page, J. Huxtable, Tony Loy, P. Bown, T. Dunkley Jones, M. O'Callaghan, Sarah Hawkes, David Halfacree, Henry Reay, Natalie Caughtry","doi":"10.1144/SP514-2020-263","DOIUrl":"https://doi.org/10.1144/SP514-2020-263","url":null,"abstract":"Abstract This study focuses on a condensed sequence of alternating carbonate–clastic sediments of the Barrington Member, Beacon Limestone Formation (latest Pliensbachian to early Toarcian) from Somerset (SW England). Abundant ammonites confirm (apart from the absence of the Clevelandicum and Tenuicostatum ammonite subchronozones) the presence of Hawskerense Subchronozone to Fallaciosum–Bingmanni subchronozones. Well-preserved, sometimes diverse assemblages of ostracods, foraminifera, nannofossils and low-diversity dinoflagellate assemblages support the chronostratigraphic framework. Stable-isotope analyses demonstrate the presence of a carbon isotope excursion, relating to the Toarcian Oceanic Anoxic Event, within the early Toarcian. Faunal, geochemical and sedimentological evidence suggest that deposition largely took place in a relatively deep-water (subwave base), mid-outer shelf environment under a well-mixed water column. However, reduced benthic diversity, the presence of weakly laminated sediments and changes in microplankton assemblage composition within the Toarcian Oceanic Anoxic Event indicates dysoxic, but probably never anoxic, bottom-water conditions during this event. The onset of the carbon isotope excursion coincides with extinction in the nannofossils and benthos, including the disappearance of the ostracod suborder Metacopina. Faunal evidence indicates connectivity with the Mediterranean region, not previously recorded for the UK during the early Toarcian.","PeriodicalId":22055,"journal":{"name":"Special Publications","volume":"452 1","pages":"239 - 268"},"PeriodicalIF":0.0,"publicationDate":"2021-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82926070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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