Pub Date : 2017-10-06DOI: 10.12789/geocanj.2017.44.122
M. Priddle
Three case studies in Canada are evaluated where a regulatory authority ruled that measures considered by some professionals to be without scientific basis and less protective of human health or the environment were the required courses of action. The three projects were in the field of environmental geoscience. In all three cases, the solution proposed by a Professional Geoscientist (P.Geo.) was opposed by a representative of a regulatory body that held authority for approval. The final outcomes that were approved by the regulator were less protective of human health (increased exposure to potential contaminants) and/or the environment (more resources used; higher contaminant exposure). In two of the three cases, the solutions were also more expensive to the client and the taxpayer. This paper explores the practice of professionalism in geoscience versus regulatory authorities that hold jurisdiction over geoscience in a broad sense. In each of the three cases, the professional opinions and analysis of the P.Geo. working for a private sector client were overridden by a professional (P.Geo. or Professional Engineer) in an approval authority. These three studies highlight the ethical decisions required by professional geoscientists in the face of regulators who hold control over areas of geoscience. Although the training of professionals is similar, regulators appear to be influenced by perceived risk as opposed to actual risk based on scientific evidence. Similarly, some policies do not have a solid scientific basis. As a result, sound scientific reasoning and resulting rational decisions may be hindered in regulatory decision-making. RESUME Trois etudes de cas canadiens sont evaluees, ou une autorite reglementaire a statue comme requises des mesures qui avaient ete declarees par des professionnels comme etant sans fondements scientifiques et moins protectrices pour la sante humaine ou les milieux de vie. Il s’agit de trois projets du domaine des geosciences des milieux de vie. Dans les trois cas, la solution proposee par un geologue professionnel (P.Geo.) a ete contestee par un representant d'un organisme reglementaire decisionnel. Les resultats definitifs approuves par l'organisme reglementaire protegeait moins la sante humaine (augmentation de l'exposition aux contaminants potentiels) et/ou le milieu de vie (plus de ressources utilisees; augmentation de l'exposition aux contaminants). Dans deux des trois cas, les solutions etaient egalement plus couteuses pour le client et le contribuable. Le present article explore la pratique professionnelle en geosciences par rapport a celle des autorites reglementaires qui ont juridiction dans le domaine des geosciences en general. Dans chacun de ces trois cas, les avis professionnels et l'analyse de P.Geo. travaillant pour un client du secteur prive ont ete supplantes par celui d’un professionnel (P.Geo. ou ingenieur professionnel) œuvrant a sein d’une autorite reglementaire. Ces trois etudes mettent en lu
{"title":"Geo-Ethics: What to do When Approval Authority Decisions Contradict Sound Science?","authors":"M. Priddle","doi":"10.12789/geocanj.2017.44.122","DOIUrl":"https://doi.org/10.12789/geocanj.2017.44.122","url":null,"abstract":"Three case studies in Canada are evaluated where a regulatory authority ruled that measures considered by some professionals to be without scientific basis and less protective of human health or the environment were the required courses of action. The three projects were in the field of environmental geoscience. In all three cases, the solution proposed by a Professional Geoscientist (P.Geo.) was opposed by a representative of a regulatory body that held authority for approval. The final outcomes that were approved by the regulator were less protective of human health (increased exposure to potential contaminants) and/or the environment (more resources used; higher contaminant exposure). In two of the three cases, the solutions were also more expensive to the client and the taxpayer. This paper explores the practice of professionalism in geoscience versus regulatory authorities that hold jurisdiction over geoscience in a broad sense. In each of the three cases, the professional opinions and analysis of the P.Geo. working for a private sector client were overridden by a professional (P.Geo. or Professional Engineer) in an approval authority. These three studies highlight the ethical decisions required by professional geoscientists in the face of regulators who hold control over areas of geoscience. Although the training of professionals is similar, regulators appear to be influenced by perceived risk as opposed to actual risk based on scientific evidence. Similarly, some policies do not have a solid scientific basis. As a result, sound scientific reasoning and resulting rational decisions may be hindered in regulatory decision-making. RESUME Trois etudes de cas canadiens sont evaluees, ou une autorite reglementaire a statue comme requises des mesures qui avaient ete declarees par des professionnels comme etant sans fondements scientifiques et moins protectrices pour la sante humaine ou les milieux de vie. Il s’agit de trois projets du domaine des geosciences des milieux de vie. Dans les trois cas, la solution proposee par un geologue professionnel (P.Geo.) a ete contestee par un representant d'un organisme reglementaire decisionnel. Les resultats definitifs approuves par l'organisme reglementaire protegeait moins la sante humaine (augmentation de l'exposition aux contaminants potentiels) et/ou le milieu de vie (plus de ressources utilisees; augmentation de l'exposition aux contaminants). Dans deux des trois cas, les solutions etaient egalement plus couteuses pour le client et le contribuable. Le present article explore la pratique professionnelle en geosciences par rapport a celle des autorites reglementaires qui ont juridiction dans le domaine des geosciences en general. Dans chacun de ces trois cas, les avis professionnels et l'analyse de P.Geo. travaillant pour un client du secteur prive ont ete supplantes par celui d’un professionnel (P.Geo. ou ingenieur professionnel) œuvrant a sein d’une autorite reglementaire. Ces trois etudes mettent en lu","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"44 1","pages":"119-123"},"PeriodicalIF":0.0,"publicationDate":"2017-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47288475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-10-06DOI: 10.12789/GEOCANJ.2017.44.120
A. Peace, G. Foulger, C. Schiffer, K. McCaffrey
Breakup between Greenland and Canada resulted in oceanic spreading in the Labrador Sea and Baffin Bay. These ocean basins are connected through the Davis Strait, a bathymetric high comprising primarily continental lithosphere, and the focus of the West Greenland Tertiary volcanic province. It has been suggested that a mantle plume facilitated this breakup and generated the associated magmatism. Plume-driven breakup predicts that the earliest, most extensive rifting, magmatism and initial seafloor spreading starts in the same locality, where the postulated plume impinged. Observations from the Labrador Sea–Baffin Bay area do not accord with these predictions. Thus, the plume hypothesis is not confirmed at this locality unless major ad hoc variants are accepted. A model that fits the observations better involves a thick continental lithospheric keel of orogenic origin beneath the Davis Strait that blocked the northward-propagating Labrador Sea rift resulting in locally enhanced magmatism. The Davis Strait lithosphere was thicker and more resilient to rifting because the adjacent Paleoproterozoic Nagssugtoqidian and Torngat orogenic belts contain structures unfavourably orientated with respect to the extensional stress field at the time.RESUMELa cassure entre le Groenland et le Canada a entraine une expansion oceanique de la mer du Labrador et de la baie de Baffin. Ces bassins oceaniques sont relies par le detroit de Davis, un haut bathymetrique constitue principalement de lithosphere continentale et de la province volcanique tertiaire de l'ouest du Groenland. Il a ete suggere qu'un panache du manteau a facilite cette cassure et genere le magmatisme associe. L’hypothese d’une cassure produite par panache du manteau predit que la premiere distension oceanique, la plus importante, le magmatisme et l'expansion oceanique initial se produisent la ou le panache mantelique touche la croute continentale. Or les observations dans la region de la mer du Labrador–baie de Baffin ne correspondent pas a ces predictions. Et donc l'hypothese du panache ne fonctionne pas dans cette region a moins que des facteurs ad hoc determinants ne soient presents. Un modele qui correspond mieux aux observations presuppose la presence d’une epaisse quille lithospherique continentale d'origine orogenique sous le detroit de Davis qui aurait bloque l’expansion oceanique de la mer du Labrador vers le nord, ce qui aurait provoque une augmentation du magmatisme localement. La lithosphere du detroit de Davis etait plus epaisse et plus resistante a l’expansion oceanique parce que les bandes orogeniques paleoproterozoiques du Nagssugtoqidian et de Torngat renferment des structures defavorablement orientees par rapport au champ de contraintes d’extensions de l'epoque.
格陵兰岛和加拿大之间的分裂导致了拉布拉多海和巴芬湾的海洋扩张。这些海洋盆地通过戴维斯海峡相连，戴维斯海峡是一个主要由大陆岩石圈组成的深海高地，也是西格陵兰第三纪火山省的焦点。有人认为，地幔柱促进了这次分裂，并产生了相关的岩浆活动。羽流驱动的破裂预示着最早、最广泛的裂谷、岩浆活动和最初的海底扩张开始于假定的羽流撞击的同一地点。拉布拉多海-巴芬湾地区的观测结果与这些预测不符。因此，羽流假说不能在这个地方得到证实，除非主要的特别变体被接受。一个更符合观测结果的模型是，在戴维斯海峡下面有一个厚的大陆岩石圈龙骨，它起源于造山带，阻挡了向北传播的拉布拉多海裂谷，导致局部岩浆活动增强。戴维斯海峡岩石圈较厚，抗裂能力较强，这是由于相邻的古元古代那萨木托起甸造山带和东伽特造山带在当时的伸展应力场中含有不利于定向的构造。resuma保证格陵兰和加拿大中心将在拉布拉多海和巴芬湾扩展海洋中心。海洋盆地与戴维斯盆地、大陆盆地和格陵兰岛西部火山盆地的水深构成原理相同。我的意思是说，我的意思是说，我的意思是说，我的意思是说，我的意思是说，我的意思是说，我的意思是说，我的意思是我的意思。假设d 'une保证了生产panache du manteau预估了最初的膨胀海洋，更重要的是，岩浆和膨胀海洋初始生产了panache mantelique和groute continental。在Labrador-baie de Baffin地区进行的观测中，新记者通过了一些预测。让我们做一个假设，假设我们的功能，假设我们的区域，假设我们的运动，假设我们的因素，假设我们的特殊决定因素，假设我们的存在。该模型对应的miaux观测假设了原始造山带的存在、岩石圈的存在、大陆的存在、Davis板块的存在、Labrador海板块的扩张、岩浆定位的增强。杜拉岩石圈底特律德戴维斯一个+ epaisse +地下女性l 'expansion oceanique因为莱斯·邦德:orogeniques paleoproterozoiques du Nagssugtoqidian et de Torngat renferment des结构defavorablement奥连特par融洽盟冠军德contraintes d 'extensions德伯爵。
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Pub Date : 2017-10-06DOI: 10.12789/GEOCANJ.2017.44.121
J. Hunt, R. Berry
Geometallurgy is a cross-disciplinary science that addresses the problem of teasing out the features of the rock mass that significantly influence mining and processing. Rocks are complex composite mixtures for which the basic building blocks are grains of minerals. The properties of the minerals, how they are bound together, and many other aspects of rock texture affect the entire mining value chain from exploration, through mining and processing, waste and tailings disposal, to refining and sales. This review presents rock properties (e.g. strength, composition, mineralogy, texture) significant in geometallurgy and examples of test methods available to measure or predict these properties. Geometallurgical data need to be quantitative and spatially constrained so they can be used in 3D modelling and mine planning. They also need to be obtainable relatively cheaply in order to be abundant enough to provide a statistically valid sample distribution for spatial modelling. Strong communication between different departments along the mining value chain is imperative so that data are produced and transferred in a useable form and duplication is avoided. The ultimate aim is to have 3D models that not only show the grade of valuable elements (or minerals), but also include rock properties that may influence mining and processing, so that decisions concerning mining and processing can be made holistically, i.e. the impacts of rock properties on all the cost centres in the mining process are taken into account. There are significant costs to improving ore deposit knowledge and it is very important to consider the cost-benefit curve when planning the level of geometallurgical effort that is appropriate in individual deposits.RESUMELa geometallurgie est une science interdisciplinaire qui s’interesse aux caracteristiques de la masse rocheuse qui influent de maniere significative sur l'exploitation miniere et le traitement du minerai. Les roches sont des melanges composites complexes dont les elements structurant de base sont des grains de mineraux. Les proprietes des mineraux, la facon dont ils sont lies entre eux, et de nombreux autres aspects de la texture des roches determinent l'ensemble de la chaine de valeur miniere, de l'exploration a l'extraction a la transformation, a l'elimination des dechets et des residus, jusqu'au raffinage et a la vente. La presente etude passe en revue les proprietes significatives de la roche (par ex. sa cohesion, sa composition, sa mineralogie, sa texture) en geometallurgie ainsi que des exemples de methodes d'essai disponibles pour mesurer ou predire ces proprietes. Les donnees geometallurgiques doivent etre quantitatives et localisees spatialement afin qu'elles puissent etre utilisees dans la modelisation 3D et la planification de la mine. Elles doivent egalement etre peu couteuses afin d'etre suffisamment nombreuses pour fournir une distribution d'echantillon statistiquement valide pour la modelisation spatiale. Une c
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Pub Date : 2017-07-21DOI: 10.12789/GEOCANJ.2017.44.118
O. Bonham, B. Broster, David Cane, Keith Johnson, K. Maclachlan
Competency-based assessment approaches to professional registration reflect the move by professions, both in Canada and around the world, away from traditional credentials-based assessments centred on a combination of academic achievements and supervised practice time. Entry to practice competencies are the abilities required to enable effective and safe entry-level practice in a profession. In 2012, Geoscientists Canada received funding from the Government of Canada’s Foreign Credentials Recognition Program. A central component of the funding involved the development of a competency profile to assist in assessment for licensing in the geoscience profession. Work concluded with the approval of the Competency Profile for Professional Geoscientists at Entry to Practice by Geoscientists Canada in November 2014. The Competency Profile comprises concise statements in plain language, setting out the skills and abilities that are required to be able to work as a geoscientist, in an effective and safe manner, independent of direct supervision. It covers competencies common to all geoscientists; competencies for the primary subdisciplines of geoscience (geology, environmental geoscience and geophysics); and a generic set of high level competences that can apply in any specific work context in geoscience. The paper is in two parts. Part 1 puts the concept of competencies in context and describes the approach taken to develop the profile, including: input from Subject Matter Experts (practising geoscientists representing a diverse sampling of the profession); extensive national consultation and refinement; and a validation procedure, including a survey of practising Canadian geoscientists. Part 2 introduces the profile, explains its structure, and provides examples of some of the competencies. The full competency profile can be obtained from the Geoscientists Canada website www.geoscientistscanada.ca. Future work will identify specific indicators of proficiency related to each competency and suggest appropriate methodologies to assess such competencies. It will also involve mapping the profile to the existing Canadian reference standard, Geoscience Knowledge and Experience Requirements for Professional Registration in Canada.RESUMELes approches d'evaluation basees sur les competences en vue de l'inscription professionnelle refletent l'abandon par les professions, tant au Canada que partout dans le monde, des evaluations classiques basees sur les titres de competences et axees sur une combinaison de realisations academiques et de temps de pratique supervisee. Les competences au niveau debutant sont les capacites requises pour une pratique efficace et en toute securite audit niveau dans une profession. En 2012, Geoscientifiques Canada a recu un financement du Programme de reconnaissance des titres de competences etrangers du gouvernement du Canada. Une composante centrale du financement incluait l’elaboration d'un profil des competences pour faciliter l'eval
基于能力的专业注册评估方法反映了加拿大和世界各地的专业人员从传统的以学历为基础的评估转向了以学术成就和监督实践时间相结合的评估。入门实践能力是指在一个职业中进行有效和安全的入门实践所需的能力。2012年，加拿大地质科学家获得了加拿大政府外国证书承认方案的资助。资金的一个核心组成部分涉及制定能力简介，以协助评估地球科学专业的许可证。2014年11月，加拿大地质科学家批准了《专业地质科学家执业能力简介》，从而完成了这项工作。能力简介包括简明的语言陈述，列出了作为一名地球科学家，以有效和安全的方式工作所需的技能和能力，独立于直接监督。它涵盖了所有地球科学家的共同能力；地球科学主要分支学科（地质学、环境地球科学和地球物理学）的能力；以及一套通用的高水平能力，可应用于地球科学的任何特定工作环境。本文分为两部分。第1部分将能力的概念放在上下文中，并描述了制定概况所采取的方法，包括：主题专家（代表该专业不同样本的执业地球科学家）的意见；广泛的全国协商和完善；以及验证程序，包括对加拿大执业地球科学家的调查。第2部分介绍了概要，解释了它的结构，并提供了一些能力的例子。完整的能力简介可从加拿大地球科学家网站www.geoscientistscanada.ca获得。未来的工作将确定与每种能力相关的具体能力指标，并提出评估这些能力的适当方法。它还将涉及将概况映射到现有的加拿大参考标准《加拿大专业注册的地球科学知识和经验要求》。RESUMELes approaches d’evaluation bases les capabilities en vue de l’铭文专业反映了对专业的放弃，tant au Canada que partout dans the world，评估类别基于能力水平，并结合了学术界和监管实践的时间。首次亮相的大学能力是对实践效率和职业安全审计能力的要求。2012年，加拿大地质科学协会为加拿大政府的能力评估计划提供了资金。联合国财务中心的组成包括制定能力简介，以促进对地球科学专业许可证的评估。2014年11月，这项工作获得了加拿大地质科学协会对首次亮相的地质科学专业人员能力的认可。能力简介包括明确的语言声明，定义了提高效率、安全性和独立性所需的能力和能力，以及地球科学。我们的能力与所有的地球科学相结合；地球科学初级学科（地质学、地球科学环境和地球物理学）的能力；以及高级大学应用程序在地球科学特定工作背景下的综合能力。文件由双方组成。各方在能力概念的背景下会面，并谴责了被采用的方法，以提高个人素质，包括：专家在该领域的贡献（地球科学专业人员代表了专业技术的多样性）；广泛的协商和完善国家梯队；以及验证程序，包括加拿大地质科学专业人员的询问。第二部分介绍了某些能力的概况、结构和四个例子。加拿大地质科学网站www.Geoscientifiques scanada.ca上提供了完整的能力简介。未来的工作识别了特定能力的指标，这是一种能力和评估方法的建议。根据加拿大现有的参考标准，以及加拿大的迫切需要和地球科学经验，我认为这需要加拿大专业人员的题词。
{"title":"The Development of Canada's Competency Profile for Professional Geoscientists at Entry-to-Practice","authors":"O. Bonham, B. Broster, David Cane, Keith Johnson, K. Maclachlan","doi":"10.12789/GEOCANJ.2017.44.118","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2017.44.118","url":null,"abstract":"Competency-based assessment approaches to professional registration reflect the move by professions, both in Canada and around the world, away from traditional credentials-based assessments centred on a combination of academic achievements and supervised practice time. Entry to practice competencies are the abilities required to enable effective and safe entry-level practice in a profession. In 2012, Geoscientists Canada received funding from the Government of Canada’s Foreign Credentials Recognition Program. A central component of the funding involved the development of a competency profile to assist in assessment for licensing in the geoscience profession. Work concluded with the approval of the Competency Profile for Professional Geoscientists at Entry to Practice by Geoscientists Canada in November 2014. The Competency Profile comprises concise statements in plain language, setting out the skills and abilities that are required to be able to work as a geoscientist, in an effective and safe manner, independent of direct supervision. It covers competencies common to all geoscientists; competencies for the primary subdisciplines of geoscience (geology, environmental geoscience and geophysics); and a generic set of high level competences that can apply in any specific work context in geoscience. The paper is in two parts. Part 1 puts the concept of competencies in context and describes the approach taken to develop the profile, including: input from Subject Matter Experts (practising geoscientists representing a diverse sampling of the profession); extensive national consultation and refinement; and a validation procedure, including a survey of practising Canadian geoscientists. Part 2 introduces the profile, explains its structure, and provides examples of some of the competencies. The full competency profile can be obtained from the Geoscientists Canada website www.geoscientistscanada.ca. Future work will identify specific indicators of proficiency related to each competency and suggest appropriate methodologies to assess such competencies. It will also involve mapping the profile to the existing Canadian reference standard, Geoscience Knowledge and Experience Requirements for Professional Registration in Canada.RESUMELes approches d'evaluation basees sur les competences en vue de l'inscription professionnelle refletent l'abandon par les professions, tant au Canada que partout dans le monde, des evaluations classiques basees sur les titres de competences et axees sur une combinaison de realisations academiques et de temps de pratique supervisee. Les competences au niveau debutant sont les capacites requises pour une pratique efficace et en toute securite audit niveau dans une profession. En 2012, Geoscientifiques Canada a recu un financement du Programme de reconnaissance des titres de competences etrangers du gouvernement du Canada. Une composante centrale du financement incluait l’elaboration d'un profil des competences pour faciliter l'eval","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"44 1","pages":"77-84"},"PeriodicalIF":0.0,"publicationDate":"2017-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46175722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-07-21DOI: 10.12789/GEOCANJ.2017.44.117
A. Liu, J. Matthews
Mistaken Point Ecological Reserve (MPER) World Heritage Site, on the southeastern coast of Newfoundland, Canada, is one of the foremost global Ediacaran fossil localities. MPER contains some of the oldest known assemblages of the soft-bodied Ediacaran macrobiota, and its fossils have contributed significantly to Ediacaran paleobiological research since their initial discovery in 1967. Preservation of multiple in situ benthic paleocommunities, some comprising thousands of specimens, has enabled research into Ediacaran paleoecology, ontogeny, taphonomy, taxonomy and morphology, offering insights into the possible phylogenetic positions of Ediacaran taxa within the tree of life. Meanwhile, a thick and continuous geological record enables the fossils to be placed within a well-resolved temporal and paleoenvironmental context spanning an interval of at least 10 million years. This article reviews the history of paleontological research at MPER, and highlights key discoveries that have shaped global thinking on the Ediacaran macrobiota.RESUMELe site du Patrimoine mondial de la Reserve ecologique de Mistaken Point (MPER), sur la cote sud-est de Terre-Neuve, au Canada, est l'une des principales localites fossiliferes ediacariennes de la planete. Le MPER renferme quelques-uns des plus anciens assemblages connus de macrobiote edicarien a parties molles, et ses fossiles ont contribue de maniere significative a la recherche paleobiologique ediacarienne depuis leur decouverte en 1967. La preservation de multiples paleocommunautes benthiques in situ, dont certaines comptant des milliers de specimens, a permis de faire des recherches en paleoecologie, ontogenese, taphonomie, taxonomie et morphologie de biotes ediacariens, ce qui a permis d’avoir un apercu de differentes positions phylogenetiques possibles des taxons ediacariens dans l'arborescence biologique. Aussi, grâce a une colonne geologique epaisse et continue, on a pu placer ces fossiles dans un contexte temporel et paleoenvironnemental bien circonscrit qui s’etend sur un intervalle d'au moins 10 millions d'annees. Cet article passe en revue l'histoire de la recherche paleontologique au MPER et souligne les decouvertes majeures qui ont faconne la reflexion sur le macrobiote ediacarien.
{"title":"Great Canadian Lagerstätten 6. Mistaken Point Ecological Reserve, Southeast Newfoundland","authors":"A. Liu, J. Matthews","doi":"10.12789/GEOCANJ.2017.44.117","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2017.44.117","url":null,"abstract":"Mistaken Point Ecological Reserve (MPER) World Heritage Site, on the southeastern coast of Newfoundland, Canada, is one of the foremost global Ediacaran fossil localities. MPER contains some of the oldest known assemblages of the soft-bodied Ediacaran macrobiota, and its fossils have contributed significantly to Ediacaran paleobiological research since their initial discovery in 1967. Preservation of multiple in situ benthic paleocommunities, some comprising thousands of specimens, has enabled research into Ediacaran paleoecology, ontogeny, taphonomy, taxonomy and morphology, offering insights into the possible phylogenetic positions of Ediacaran taxa within the tree of life. Meanwhile, a thick and continuous geological record enables the fossils to be placed within a well-resolved temporal and paleoenvironmental context spanning an interval of at least 10 million years. This article reviews the history of paleontological research at MPER, and highlights key discoveries that have shaped global thinking on the Ediacaran macrobiota.RESUMELe site du Patrimoine mondial de la Reserve ecologique de Mistaken Point (MPER), sur la cote sud-est de Terre-Neuve, au Canada, est l'une des principales localites fossiliferes ediacariennes de la planete. Le MPER renferme quelques-uns des plus anciens assemblages connus de macrobiote edicarien a parties molles, et ses fossiles ont contribue de maniere significative a la recherche paleobiologique ediacarienne depuis leur decouverte en 1967. La preservation de multiples paleocommunautes benthiques in situ, dont certaines comptant des milliers de specimens, a permis de faire des recherches en paleoecologie, ontogenese, taphonomie, taxonomie et morphologie de biotes ediacariens, ce qui a permis d’avoir un apercu de differentes positions phylogenetiques possibles des taxons ediacariens dans l'arborescence biologique. Aussi, grâce a une colonne geologique epaisse et continue, on a pu placer ces fossiles dans un contexte temporel et paleoenvironnemental bien circonscrit qui s’etend sur un intervalle d'au moins 10 millions d'annees. Cet article passe en revue l'histoire de la recherche paleontologique au MPER et souligne les decouvertes majeures qui ont faconne la reflexion sur le macrobiote ediacarien.","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"44 1","pages":"63-76"},"PeriodicalIF":0.0,"publicationDate":"2017-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44506971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-07-21DOI: 10.12789/GEOCANJ.2017.44.119
R. MacNaughton, G. Nowlan, A. Mccracken, K. Fallas
Since 2004, the Calgary office of the Geological Survey of Canada has been holding ‘Rock ‘n’ Fossil Road Shows’ at Calgary Public Library branches, in partnership with the Alberta Science Network and the Alberta Palaeontological Society. These now-annual earth science education outreach events have given more than 3700 people of all ages the opportunity to view, examine, and learn about GSC-Calgary’s collection of rocks, minerals, and fossils (including many museum quality pieces), have their own samples and collections identified by experts, and gain a better understanding of local and regional geology. This article describes what goes into organizing these events, reviews their evolution, and discusses reasons for their enduring success. The ‘Road Show’ approach can be viable in a range of settings and may be a good educational outreach option for research institutes with collections of interesting geological specimens and a critical mass of interested staff. RESUME Depuis 2004, le bureau de Calgary de la Commission geologique du Canada tient des representations de son spectacle itinerant « Roche et fossiles » dans les succursales de la bibliotheque publique de Calgary, en partenariat avec l’ Alberta Science Network et l’ Alberta Palaeontological Society . Ces activites de rayonnement en sciences de la Terre, maintenant annuels, ont deja offert a plus de 3700 personnes de tous âges la possibilite de voir, d'examiner et d'apprendre a partir de la collection de roches, de mineraux et de fossiles de la CGC-Calgary (certaines pieces de qualite museale), et de voir leurs propres echantillons et collections identifies par des experts, et ainsi obtenir une meilleure comprehension de la geologie locale et regionale. Le present article decrit les details de l'organisation de ces evenements, retrace leur evolution et revoit les raisons de leur succes durable. L'approche du « spectacle itinerant » peut etre viable dans differents contextes et peut etre une bonne option de sensibilisation educative pour les instituts de recherche disposant de collections de specimens geologiques interessants et d’une masse critique d’employes interesses.
{"title":"The 'Rock ‘n’ Fossil Road Show:' An Enduring Earth Science Educational Outreach Initiative in Calgary, Alberta","authors":"R. MacNaughton, G. Nowlan, A. Mccracken, K. Fallas","doi":"10.12789/GEOCANJ.2017.44.119","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2017.44.119","url":null,"abstract":"Since 2004, the Calgary office of the Geological Survey of Canada has been holding ‘Rock ‘n’ Fossil Road Shows’ at Calgary Public Library branches, in partnership with the Alberta Science Network and the Alberta Palaeontological Society. These now-annual earth science education outreach events have given more than 3700 people of all ages the opportunity to view, examine, and learn about GSC-Calgary’s collection of rocks, minerals, and fossils (including many museum quality pieces), have their own samples and collections identified by experts, and gain a better understanding of local and regional geology. This article describes what goes into organizing these events, reviews their evolution, and discusses reasons for their enduring success. The ‘Road Show’ approach can be viable in a range of settings and may be a good educational outreach option for research institutes with collections of interesting geological specimens and a critical mass of interested staff. RESUME Depuis 2004, le bureau de Calgary de la Commission geologique du Canada tient des representations de son spectacle itinerant « Roche et fossiles » dans les succursales de la bibliotheque publique de Calgary, en partenariat avec l’ Alberta Science Network et l’ Alberta Palaeontological Society . Ces activites de rayonnement en sciences de la Terre, maintenant annuels, ont deja offert a plus de 3700 personnes de tous âges la possibilite de voir, d'examiner et d'apprendre a partir de la collection de roches, de mineraux et de fossiles de la CGC-Calgary (certaines pieces de qualite museale), et de voir leurs propres echantillons et collections identifies par des experts, et ainsi obtenir une meilleure comprehension de la geologie locale et regionale. Le present article decrit les details de l'organisation de ces evenements, retrace leur evolution et revoit les raisons de leur succes durable. L'approche du « spectacle itinerant » peut etre viable dans differents contextes et peut etre une bonne option de sensibilisation educative pour les instituts de recherche disposant de collections de specimens geologiques interessants et d’une masse critique d’employes interesses.","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"44 1","pages":"85-90"},"PeriodicalIF":0.0,"publicationDate":"2017-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66817965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-04-20DOI: 10.12789/GEOCANJ.2017.44.116
J. Gosse, A. Ballantyne, Joel Barker, A. Csank, T. Fletcher, G. W. Grant, D. Greenwood, R. Macphee, N. Rybczynski
This short summary presents selected results of an ongoing investigation into the feedbacks that contribute to amplified Arctic warming. The consequences of warming for Arctic biodiversity and landscape response to global warmth are currently being interpreted. Arctic North American records of large-scale landscape and paleoenvironmental change during the Pliocene are exquisitely preserved and locked in permafrost, providing an opportunity for paleoenvironmental and faunal reconstruction with unprecedented quality and resolution. During a period of mean global temperatures only ~2.5°C above modern, the Pliocene molecular, isotopic, tree-ring, paleofaunal, and paleofloral records indicate that the high Arctic mean annual temperature was 11°C–19°C above modern values, pointing to a much shallower latitudinal temperature gradient than exists today. It appears that the intense Neogene warming caused thawing and weathering to liberate sediment and create a continuous and thick (>2.5 km in places) clastic wedge from at least Banks Island to Meighen Island to form a coastal plain that provided a highway for camels and other mammals to migrate and evolve in the high Arctic. In this summary we highlight the opportunities that exist for research on these and related topics with the PoLAR-FIT community. RESUME Ce bref resume presente les resultats choisis d'une enquete en cours sur les declencheurs qui contribuent a l’amplification du rechauffement de l'Arctique. Les consequences du rechauffement sur la biodiversite arctique et de la reponse du paysage au rechauffement climatique sont en cours d’etre interprete. Des dossiers nord-americains de paysage a grande echelle et le changement paleoenvironnementales durant le Pliocene sont exceptionnellement preserves et scellees dans un etat de congelation qui fournissant une occasion pour la reconstruction paleoenvironnementale et faunistique avec une qualite et une resolution sans precedent. Pendent une periode de rechauffement global seulement ~2,5°C au-dessus de moderne les dossiers, moleculaire, isotopique, annaux de croissance, paleofaunistique et paleovegetation indiquent que l'Arctique a connu une augmentation de la temperature annuelle moyenne de 11°C–19°C au-dessus de moderne, en montrant un inferieur gradient de temperature latitudinal qu'aujourd'hui. Il semble que le rechauffement intense pendent le Neogene a provoque la decongelation et erosion pour liberer les sediments et creer une plaine cotiere continuel et epaisse (> 2,5 km dans lieux) qui a fourni une route pour les chameaux et autres mammiferes pour migrer et evoluer dans l’Haut-Arctique. Dans ce resume, nous soulignons les opportunites qui existent pour la recherche sur ces sujets et les sujets connexes avec la communaute PoLAR-FIT.
{"title":"PoLAR-FIT: Pliocene Landscapes and Arctic Remains—Frozen in Time","authors":"J. Gosse, A. Ballantyne, Joel Barker, A. Csank, T. Fletcher, G. W. Grant, D. Greenwood, R. Macphee, N. Rybczynski","doi":"10.12789/GEOCANJ.2017.44.116","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2017.44.116","url":null,"abstract":"This short summary presents selected results of an ongoing investigation into the feedbacks that contribute to amplified Arctic warming. The consequences of warming for Arctic biodiversity and landscape response to global warmth are currently being interpreted. Arctic North American records of large-scale landscape and paleoenvironmental change during the Pliocene are exquisitely preserved and locked in permafrost, providing an opportunity for paleoenvironmental and faunal reconstruction with unprecedented quality and resolution. During a period of mean global temperatures only ~2.5°C above modern, the Pliocene molecular, isotopic, tree-ring, paleofaunal, and paleofloral records indicate that the high Arctic mean annual temperature was 11°C–19°C above modern values, pointing to a much shallower latitudinal temperature gradient than exists today. It appears that the intense Neogene warming caused thawing and weathering to liberate sediment and create a continuous and thick (>2.5 km in places) clastic wedge from at least Banks Island to Meighen Island to form a coastal plain that provided a highway for camels and other mammals to migrate and evolve in the high Arctic. In this summary we highlight the opportunities that exist for research on these and related topics with the PoLAR-FIT community. RESUME Ce bref resume presente les resultats choisis d'une enquete en cours sur les declencheurs qui contribuent a l’amplification du rechauffement de l'Arctique. Les consequences du rechauffement sur la biodiversite arctique et de la reponse du paysage au rechauffement climatique sont en cours d’etre interprete. Des dossiers nord-americains de paysage a grande echelle et le changement paleoenvironnementales durant le Pliocene sont exceptionnellement preserves et scellees dans un etat de congelation qui fournissant une occasion pour la reconstruction paleoenvironnementale et faunistique avec une qualite et une resolution sans precedent. Pendent une periode de rechauffement global seulement ~2,5°C au-dessus de moderne les dossiers, moleculaire, isotopique, annaux de croissance, paleofaunistique et paleovegetation indiquent que l'Arctique a connu une augmentation de la temperature annuelle moyenne de 11°C–19°C au-dessus de moderne, en montrant un inferieur gradient de temperature latitudinal qu'aujourd'hui. Il semble que le rechauffement intense pendent le Neogene a provoque la decongelation et erosion pour liberer les sediments et creer une plaine cotiere continuel et epaisse (> 2,5 km dans lieux) qui a fourni une route pour les chameaux et autres mammiferes pour migrer et evoluer dans l’Haut-Arctique. Dans ce resume, nous soulignons les opportunites qui existent pour la recherche sur ces sujets et les sujets connexes avec la communaute PoLAR-FIT.","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"44 1","pages":"47-54"},"PeriodicalIF":0.0,"publicationDate":"2017-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45158908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-04-20DOI: 10.12789/GEOCANJ.2017.44.114
C. Yakymchuk
Phase equilibria modelling has played a key role in enhancing our understanding of metamorphic processes. An important breakthrough in the last three decades has been the ability to construct phase diagrams by integrating internally consistent datasets of the thermodynamic properties of minerals, fluids and melts with activity–composition models for mixed phases that calculate end-member activities from end-member proportions. A major advance in applying phase equilibria modelling to natural rocks is using isochemical phase diagrams to explore the phase assemblages and reaction sequences applicable for a particular sample. The chemical systems used for modelling phase equilibria are continually evolving to provide closer approximations to the natural compositions of rocks and allow wider varieties of compositions to be modelled. Phase diagrams are now routinely applied to metasedimentary rocks, metabasites and intermediate to felsic intrusive rocks and more recently to ultramafic rocks and meteorites. While the principal application of these phase diagrams is quantifying the pressure and temperature evolution of metamorphic rocks, workers are now applying them to other fields across the geosciences. For example, phase equilibria modelling of hydrothermal alteration and the metamorphism of hydrothermally altered rocks can be used to determine ‘alteration vectors’ to hydrothermal mineral deposits. Combining the results of phase equilibria of rock-forming minerals with solubility equations of accessory minerals has provided new insights into the geological significance of U–Pb ages of accessory minerals commonly used in geochronology (e.g. zircon and monazite). Rheological models based on the results of phase equilibria modelling can be used to evaluate how the strength of the crust and mantle can change through metamorphic and metasomatic processes, which has implications for a range of orogenic processes, including the localization of earthquakes. Finally, phase equilibria modelling of fluid generation and consumption during metamorphism can be used to explore links between metamorphism and global geochemical cycles of carbon and sulphur, which may provide new insights into the secular change of the lithosphere, hydrosphere and atmosphere.RESUMELa modelisation des equilibres de phases a joue un role cle dans l’amelioration de notre comprehension des processus metamorphiques. Une percee importante au cours des trois dernieres decennies a ete la capacite de construire des diagrammes de phase en y integrant des ensembles de donnees coherentes des proprietes thermodynamiques des mineraux, des fluides et des bains magmatiques avec des modeles d'activite-composition pour des phases mixtes qui deduisent l’activite des membres extremes a partir des proportions des membres extremes. Une avancee majeure dans l'application de la modelisation d'equilibre de phase aux roches naturelles consiste a utiliser des diagrammes de phases isochimiques pour etudier les
相平衡模型在增强我们对变质过程的理解方面发挥了关键作用。在过去的三十年中，一个重要的突破是通过整合矿物、流体和熔体热力学性质的内部一致数据集，以及混合相的活性组成模型来构建相图的能力，该模型可以从端元比例计算端元活性。将相平衡模型应用于天然岩石的一个主要进展是使用等化学相图来探索适用于特定样品的相组合和反应序列。用于模拟相平衡的化学系统正在不断发展，以提供更接近岩石自然成分的近似，并允许更广泛的成分被建模。相图现在通常应用于变质沉积岩、变质岩和中英质侵入岩，最近应用于超镁铁质岩石和陨石。虽然这些相图的主要应用是量化变质岩的压力和温度演变，但工作人员现在正在将它们应用于地球科学的其他领域。例如，热液蚀变的相平衡模拟和热液蚀变岩的变质作用可用于确定热液矿床的“蚀变向量”。将造岩矿物相平衡结果与副矿物溶解度方程相结合，为年代学中常用的副矿物(如锆石、独居石)U-Pb年龄的地质意义提供了新的认识。基于相平衡模拟结果的流变模型可以用来评估地壳和地幔的强度如何通过变质和交代过程发生变化，这对一系列造山过程，包括地震的局部化都有影响。最后，利用变质作用过程中流体生成和消耗的相平衡模拟，可以探索变质作用与全球碳、硫地球化学循环之间的联系，为岩石圈、水圈和大气的长期变化提供新的认识。对过程变形的理解的改进，对过程变形的理解的改进，对过程变形的理解的改进。重要的课程有三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种，一种是三种。一种不可抗力的方法是:应用、建模、相平衡、自然规律，包括利用、相图、相等化学、相组合、相组合、反应序列，适用于各种特殊物质。Les systems chimiques利用了pour la建模、平衡、相演化、连续体、近似和方法、组分、自然、岩石和渗透、建模和大变化组分。相图分为两部分，一是相图、相图、相图、相图、相图、相图、相图、相图、相图、相图、相图、相图、相图、相图、相图、相图。相图的应用原理包括一个量词:演化、压力、温度、岩石变质、应用、维护和地球科学的特殊性质。例如，热液蚀变相的平衡模型和热液岩的变质模型、热液蚀变岩的变质模型、热液矿的变质岩的变质模型、热液矿的蚀变矢量模型、热液矿的变质岩的确定模型。des equilibres de La combinaison结果阶段des mineraux constitutifs des罗氏用des方程de solubilite des mineraux附件有的d我知道davantage苏尔La意义geologique des年龄U-Pb des mineraux附件couramment利用en geochronologie(比如锆石et独居石)。模型流变学的基础是模型化的结果，模型化的结果是平衡的结果，模型化的结果是平衡的结果，模型化的结果是平衡的结果，模型的结果是平衡的结果，模型的结果是平衡的结果，模型的结果是平衡的结果，模型的结果是平衡的结果，模型的结果是平衡的结果，模型的结果是平衡的结果，模型的结果是平衡的结果。 胀的平衡模型最后阶段在metamorphisme generation和吸收流体可用于探索hie metamorphisme之间联系和全球地球化学循环的碳和硫,这可以提供新视角变化seculaire lithosphere、l’hydrosphere和气氛。
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Pub Date : 2017-04-20DOI: 10.12789/GEOCANJ.2017.44.115
Jeffrey M. Minicucci
This article briefly examines the possible confusion pertaining to the discoveries of Precambrian (Ediacaran) fossils made in the self-governing British colony of Newfoundland in 1868 by the amateur naturalist, the Reverend Moses Harvey, and the subsequent description and naming of the fossil organism Aspidella terranovica in 1872 by Elkanah Billings, the father of Canadian paleontology. Both events could be misinterpreted as one transaction that began with the former event and ended with the latter event. Accounts published by Alexander Murray, the director of the Geological Survey of Newfoundland at the time, arguably may have inadvertently exacerbated the possibility for confusion. The determination of who first discovered fossils of A. terranovica and whose fossil material Billings primarily relied upon when he first described and named the taxon could be placed into doubt as a consequence. Although the confusion does not affect the undisputed priority that Billings holds in having described and named A. terranovica, the opportunity to remedy the confusion serves to benefit the historical record. The incomplete or ambiguous ascertaining and documenting of contextual information whenever an historically significant fossil discovery is made arguably may precipitate subsequent misinterpretations, distortions or omissions in the resulting historical narrative as it develops and becomes entrenched or mythologized in its retelling.RESUMECet article examine brievement la confusion possible concernant les decouvertes de fossiles Precambriens (Ediacaran) fabriques dans la colonie Britannique autonome de Terre-Neuve en 1868 par le naturaliste amateur, le Reverend Moses Harvey, et la description et l'appellation suivantes de l'organisme fossile Aspidella terranovica en 1872 par Elkanah Billings, le pere de la paleontologie Canadienne. Les deux evenements pourraient etre mal interpretes comme une transaction qui a commence avec l'evenement precedent et s'est terminee avec le dernier evenement. Les comptes publies par Alexander Murray, le directeur de la Commission Geologique de Terre-Neuve a l'epoque, ont sans doute peut-etre exacerbe par megarde la possibilite de confusion. La determination de qui a decouvert les fossiles d'abord de A. terranovica et dont Billings s'appuyait principalement sur le materiel fossile dont il a d'abord decrit et nomme le taxon pourrait etre mis en doute en consequence. Bien que la confusion ne porte pas atteinte a la priorite incontestee que Billings detient en ayant decrit et nomme A. terranovica, la possibilite de remedier a la confusion sert a beneficier du dossier historique. La constatation et la documentation incompletes ou ambigues de l'information contextuelle chaque fois qu'une decouverte fossilifere historiquement significative peut etre faite peut precipiter des interpretations, des distorsions ou des omissions subsequentes dans le recit historique resultant au fur et a mesure qu'il se developpe et devient ancre o
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Pub Date : 2017-04-20DOI: 10.12789/GEOCANJ.2017.44.113
R. Grieve
The current record of large-scale impact on Earth consists of close to 200 impact structures and some 30 impact events recorded in the stratigraphic record, only some of which are related to known structures. It is a preservation sample of a much larger production population, with the impact rate on Earth being higher than that of the moon. This is due to the Earth’s larger physical and gravitational cross-sections, with respect to asteroidal and cometary bodies entering the inner solar system. While terrestrial impact structures have been studied as the only source of ground-truth data on impact as a planetary process, it is becoming increasingly acknowledged that large-scale impact has had its effects on the geologic history of the Earth, itself. As extremely high energy events, impacts redistribute, disrupt and reprocess target lithologies, resulting in topographic, structural and thermal anomalies in the upper crust. This has resulted in many impact structures being the source of natural resources, including some world-class examples, such as gold and uranium at Vredefort, South Africa, Ni–Cu–PGE sulphides at Sudbury, Canada and hydrocarbons from the Campeche Bank, Mexico. Large-scale impact also has the potential to disrupt the terrestrial biosphere. The most devastating known example is the evidence for the role of impact in the Cretaceous–Paleocene (K–Pg) mass extinction event and the formation of the Chicxulub structure, Mexico. It also likely had a role in other, less dramatic, climatic excursions, such as the Paleocene–Eocene–Thermal Maximum (PETM) event. The impact rate was much higher in early Earth history and, while based on reasoned speculation, it is argued that the early surface of the Hadean Earth was replete with massive impact melt pools, in place of the large multiring basins that formed on the lower gravity moon in the same time-period. These melt pools would differentiate to form more felsic upper lithologies and, thus, are a potential source for Hadean-aged zircons, without invoking more modern geodynamic scenarios. The Earth-moon system is unique in the inner solar system and currently the best working hypothesis for its origin is a planetary-scale impact with the proto-Earth, after core formation at ca. 4.43 Ga. Future large-scale impact is a low probability event but with high consequences and has the potential to create a natural disaster of proportions unequalled by other geologic processes and threaten the extended future of human civilization, itself.RESUMELe bilan actuel de traces de grands impacts sur la Terre se compose de pres de 200 astroblemes et d'une trentaine d’impacts enregistres dans la stratigraphie, dont seulement certains sont lies a des astroblemes connus. Il s'agit d'echantillons preserves sur une population d’evenements beaucoup plus importante, le taux d'impact sur Terre etant superieur a celui de la lune. Cela tient aux plus grandes sections transversales physiques et gravitationnelles de la Terre
{"title":"Logan Medallist 4. Large-Scale Impact and Earth History","authors":"R. Grieve","doi":"10.12789/GEOCANJ.2017.44.113","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2017.44.113","url":null,"abstract":"The current record of large-scale impact on Earth consists of close to 200 impact structures and some 30 impact events recorded in the stratigraphic record, only some of which are related to known structures. It is a preservation sample of a much larger production population, with the impact rate on Earth being higher than that of the moon. This is due to the Earth’s larger physical and gravitational cross-sections, with respect to asteroidal and cometary bodies entering the inner solar system. While terrestrial impact structures have been studied as the only source of ground-truth data on impact as a planetary process, it is becoming increasingly acknowledged that large-scale impact has had its effects on the geologic history of the Earth, itself. As extremely high energy events, impacts redistribute, disrupt and reprocess target lithologies, resulting in topographic, structural and thermal anomalies in the upper crust. This has resulted in many impact structures being the source of natural resources, including some world-class examples, such as gold and uranium at Vredefort, South Africa, Ni–Cu–PGE sulphides at Sudbury, Canada and hydrocarbons from the Campeche Bank, Mexico. Large-scale impact also has the potential to disrupt the terrestrial biosphere. The most devastating known example is the evidence for the role of impact in the Cretaceous–Paleocene (K–Pg) mass extinction event and the formation of the Chicxulub structure, Mexico. It also likely had a role in other, less dramatic, climatic excursions, such as the Paleocene–Eocene–Thermal Maximum (PETM) event. The impact rate was much higher in early Earth history and, while based on reasoned speculation, it is argued that the early surface of the Hadean Earth was replete with massive impact melt pools, in place of the large multiring basins that formed on the lower gravity moon in the same time-period. These melt pools would differentiate to form more felsic upper lithologies and, thus, are a potential source for Hadean-aged zircons, without invoking more modern geodynamic scenarios. The Earth-moon system is unique in the inner solar system and currently the best working hypothesis for its origin is a planetary-scale impact with the proto-Earth, after core formation at ca. 4.43 Ga. Future large-scale impact is a low probability event but with high consequences and has the potential to create a natural disaster of proportions unequalled by other geologic processes and threaten the extended future of human civilization, itself.RESUMELe bilan actuel de traces de grands impacts sur la Terre se compose de pres de 200 astroblemes et d'une trentaine d’impacts enregistres dans la stratigraphie, dont seulement certains sont lies a des astroblemes connus. Il s'agit d'echantillons preserves sur une population d’evenements beaucoup plus importante, le taux d'impact sur Terre etant superieur a celui de la lune. Cela tient aux plus grandes sections transversales physiques et gravitationnelles de la Terre","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"44 1","pages":"1-26"},"PeriodicalIF":0.0,"publicationDate":"2017-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46822766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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