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2. Best Paper Award 2018
- Author
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Polat, Ali
- Subjects
Science publishing -- Achievements and awards ,Earth sciences ,Geological Association of Canada -- Achievements and awards - Abstract
The Canadian Journal of Earth Sciences 'Best Paper Award' is an annual award given jointly by Canadian Science Publishing (CSP) and the Geological Association of Canada (GAC). It reflects the [...]
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- 2019
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3. Best Paper Award 2016.
- Author
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Polat, Ali
- Subjects
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EARTH sciences , *OROGENIC belts - Abstract
The article announces that the GAC–CSP Canadian Journal of Earth Sciences Best Paper Award for 2016 has been presented to Richard A. Glen and colleagues for their study related to different styles of non-collisional orogens and implications for crustal growth.
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- 2017
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4. Best Paper Award 2015.
- Author
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Polat, Ali
- Subjects
STRATIGRAPHIC geology ,EARTH sciences ,AWARDS - Abstract
The article announces the selection of "Chronostratigraphy of the Hottah Terrane and Great Bear Magmatic Zone of Wopmay Orogen, Canada and Exploration of a Terrane Translation Model" by Luke Ootes et al. as the winner of the 2015 "Canadian Journal of Earth Sciences" Best Paper Award.
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- 2016
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5. Canada's maritime frontier: the science legacy of Canada's extended continental shelf mapping for UNCLOS
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Mosher, David C., Dickson, Mary-Lynn, Shimeld, John, Jackson, H. Ruth, Oakey, Gordon N., Boggild, Kai, Campbell, D. Calvin, Travaglini, Paola, Rainey, Walta-Anne, Murphy, Alain, Dehler, Sonya, and Ells, John
- Subjects
Continental margins -- Environmental aspects -- Models ,Ocean bottom -- Models -- Environmental aspects ,Earth sciences ,United Nations Convention on the Law of the Sea - Abstract
Canada ratified the United Nations Convention on the Law of the Sea (UNCLOS) in 2003. With that ratification is an obligation to submit data and information to the U.N. pertaining to the limits of the country's extended continental shelf (ECS); the portion of the juridical continental shelf that extends beyond 200 nautical miles. A team of Canadian scientists, managers, and legal experts that included representation from three Federal Departments (Natural Resources Canada, Fisheries and Oceans Canada, and Global Affairs Canada) with additional support from other departments, spent 13 years compiling and acquiring data to provide the scientific evidence to support delineation of Canada's seaward most maritime limit. The submission has the potential to provide Canada with 2.4 million km (2) of additional submarine landmass in the Atlantic and the Arctic oceans over which Canada exercises sovereign rights for the purpose of exploring and exploiting its natural resources. Specific information such as the tectonic framework of the continental margin, the geomorphology of the margin and in particular the continental slope, the geologic nature of adjoined ridges, rises, and plateaux, and sediment thickness within adjacent basins are examples of fundamental pieces of geoscientific information needed to substantiate Canada's outermost maritime limits. This paper highlights a number of segments of Canada's continental margins to showcase this scientific evidence and how it is applied in the UNCLOS context. In doing so, the paper demonstrates the geologic complexity of Canada's margins as illustrated in scientific publications that have resulted from these new data collections, while at the same time presenting new scientific evidence and interpretations. This collection of data and information provides a wealth of new knowledge in Canada's offshore regions. The massive data compilation in the Atlantic led to conception of continental margins, in a source-to-sink scenario, as having an equilibrium base level or graded form, comparable to river systems. Departures from this shape relate to the interplay of sedimentary processes and in particular to those processes that do not fit the source-to-sink paradigm. For example, a significant part of the Atlantic margin is shown to be heavily influenced by along-slope geostrophic currents that generated massive contourite drift deposits. These deposits reflect lateral transport of sediment that had a significant impact on the morphology of the margin. The role of mass transport processes in shaping continental margins is also highlighted, and in particular the collapses of entire segments of the margin were observed. The prominent role mass failure processes play in delivering sediment to the adjacent abyssal plain is also critical in the ECS context. These observations challenge the entrenched notion of a continental margin comprising a shelf, slope, and rise and in particular the concept of the 'continental rise'. Prior to 2006, regions of the Arctic Ocean seaward of the Canadian landmass had fewer than 5000 km of seismic reflection data. The massive efforts of Arctic coastal States to map their margins for ECS purposes have led to a leap in technological advances to acquire data in ice-covered seas and have led to a wealth of new geoscientific knowledge. Perhaps foremost amongst this knowledge is demonstration that Canada Basin is indeed a fully developed ocean basin, albeit significantly infilled with sediment. Based on this knowledge and identification of related structures, new realistic tectonic scenarios for opening of the Amerasia Basin are proposed that include a significant component of transform or strike-slip motions. With seismic velocity and rock sample information, the continental nature of Alpha and Mendeleev ridges has been substantiated. Even bathymetric data were lacking in the Arctic and new editions of seafloor maps now support grids of 500 m spacing; although some regions remain sparse. Once thought to be relatively stagnant, sedimentary processes such as found in many ocean basins were discovered in the Arctic Ocean. Evidence of geostrophic currents, sediment mass failures, and deep-sea turbidity current channels were found to be ubiquitous, even in the deepest parts of the Arctic's basins. Key words: United Nations Convention on the Law of the Sea, extended continental shelf, continental margin, Atlantic Ocean, Arctic Ocean, 1. Introduction It is a common adage that we know more about the Moon and Mars than we do about the oceans on Earth. As an example, according to the [...]
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- 2023
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6. Reply to the Discussion by Landing and Geyer on "The Terreneuvian MacCodrum Brook section, Mira terrane, Cape Breton Island, Nova Scotia, Canada: age constraints from ash layers, organic-walled microfossils, and trace fossils".
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Barr, Sandra M., White, Chris E., Palacios, Teodoro, Jensen, Sören, van Rooyen, Deanne, and Crowley, James L.
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TRACE fossils ,FOSSIL microorganisms ,ENVIRONMENTAL sciences ,GEOLOGICAL surveys ,EARTH sciences ,ISLANDS - Published
- 2023
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7. R.A. Daly's early model of seafloor generation 40 years before the Vine-Matthews hypothesis: an outstanding theoretical achievement inspired by field work on St. Helena in 1921-1922.
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Letsch, Dominik and Murphy, Brendan
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PLANETARY atmospheres ,STRUCTURAL geology ,LITHOSPHERE ,EARTH sciences - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2015
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8. Structure from motion used to revive archived aerial photographs for geomorphological analysis: an example from Mount Meager volcano, British Columbia, Canada
- Author
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Roberti, Gioachino, Ward, Brent C., deVries, Benjamin van Wyk, Perotti, Luigi, Giardino, Marco, Friele, Pierre A., Clague, John J., Menounos, Brian, Anderson, Leif S., and Freschi, Stefano
- Subjects
Glaciers -- Models ,Volcanoes -- Models -- Canada ,Geomorphology -- Models ,Landslides -- Models -- Canada ,Algorithms -- Usage ,Photogrammetry -- Usage ,Algorithm ,Earth sciences - Abstract
High-resolution topographic modeling has become more accessible due to the development of structure from motion (SfM)-image-matching algorithms in digital photogrammetry. Large archival databases of historical aerial photographs are available in university, public, and government libraries, commonly as paper copies. The photographs can be in poor condition (i.e., deformed by humidity, scratched, or annotated). In addition, the negatives, as well as metadata, may be missing. Processing such photographs using classic stereo-photogrammetry is difficult and, in many instances, impossible. SfM can be applied to these photosets to access the valuable archive of geomorphic changes over the past century. In this paper, we illustrate the utility of the SfM technique using 568 digitized vertical aerial photographs of Mount Meager volcano, located in southwestern British Columbia, Canada. We use the aerial photographs, which span the period from 1947 to 2006, to track glaciers and glacier-landslide interactions on the volcano. Over this period, glaciers have thinned and retreated, interrupted by minor advances in the 1960s and 1970s. Landslides are frequent on the volcano and contribute to debris cover on the glaciers affecting the ablation process. SfM processing of the aerial photographs allowed us to unlock geomorphic information and reconstruct landscape change that would otherwise have been impossible. The results from SfM provide a visually effective way of presenting landscape change to a broad public audience, as a form of virtual geoheritage. The approach can thus be broadly applied in scientific and professional practices for improving land planning and hazard management. Key words: historical aerial photographs, structure from motion, glacier change, landslides, debris-covered glaciers. La modelisation topographique de haute resolution est devenue plus accessible en raison du developpement d'algorithmes de jumelage d'images de type << structure from motion >> (SfM, structure acquise a partir d'un mouvement) en photogrammetrie numerique. D'imposantes bases de donnees d'archives de photographies aeriennes sont disponibles dans les bibliotheques universitaires, publiques et gouvernementales, generalement en version papier. Ces photographies peuvent etre en mauvais etat (c.-a-d., deformees par l'humidite, egratignees ou annotees). En outre, des negatifs, ainsi que des metadonnees, peuvent manquer a l'appel. Le traitement de telles photographies par stereophoto-grammetrie classique est difficile, voire impossible dans bien des cas. La SfM peut etre appliquee a ses ensembles de photos pour acceder a l'important registre de changements geomorphologiques durant le siecle passe qu'ils renferment. Nous illustrons l'utilisation de la methode SfM en utilisant 568 photographies aeriennes verticales numerisees du volcan du mont Meager, dans le sud-ouest de la Colombie-Britannique (Canada). Nous utilisons les photographies aeriennes, qui couvrent la periode de 1947 a 2006, pour suivre les glaciers et les interactions entre glaciers et glissements de terrain sur le volcan. Cette periode est marquee par l'amincissement et le retrait des glaciers, interrompus par des avancees mineures dans les annees 1960 et 1970. Les glissements de terrain sont frequents sur le volcan et participent a l'accumulation d'un couvert de debris sur les glaciers qui influence le processus d'ablation. Le traitement SfM des photographies aeriennes nous a permis d'extraire de l'information geomorphologique et de reconstituer les changements du paysage, ce qui n'aurait pas ete possible autrement. Les resultats de SfM offrent un moyen visuellement efficace de presenter des modifications du paysage au grand public, comme geopatrimoine virtuel. L'approche peut ainsi etre appliquee largement dans les domaines scientifique et professionnel pour ameliorer l'amenagement du territoire et la gestion des risques. [Traduit par la Redaction] Mots-cles : photographies aeriennes passees, << structure from motion >>, modification de glaciers, glissements de terrain, glaciers couverts de debris., Introduction Reconstructions of geomorphic change over time are fundamental in many landform and natural hazard studies. Such landscape reconstructions are essential for following the evolution of features that might cause [...]
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- 2021
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9. Introduction to the Special issue of the Canadian Journal of Earth Sciences, "Magmatic and metallogenic processes associated with large igneous provinces".
- Author
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Williamson, Marie-Claude and Saumur, Benoit M.
- Subjects
IGNEOUS provinces ,EARTH sciences ,MINES & mineral resources ,IGNEOUS rocks ,GEOCHEMISTRY ,PETROLOGY - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
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10. Revisiting Russell's troodontid: autecology, physiology, and speculative tool use
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Varricchio, D.J., Hogan, J.D., and Freimuth, W.J.
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Biological research ,Biology, Experimental ,Theropoda -- Natural history -- Behavior ,Trace fossils -- Research ,Earth sciences - Abstract
Dale Russell described the osteology, morphology, and ecology of the small theropod 'Stenonychosaurus inequalis' in two papers, speculating on its life habits, brain power, vision, movement, feeding, and hand capabilities. Russell even pondered a tool-using dinosauroid, the hypothetical troodontid descendant if the lineage had survived the Cretaceous-Paleogene extinction event. We revisit the life habits of the North American troodontids Troodon formosus and Latenivenatrix mcmasterae in part by reviewing various trace fossils of T. formosus discovered in Montana. These fossils include egg clutches, a nest, and recently discovered regurgitalites. We also contemplate the possibility of dinosaur tool use. Troodon likely constructed earthen nests in the same way that ratites and other birds did to create their nesting scrapes through backward hindlimb kicks. The more complex clutch architecture suggests dexterous movement of the eggs, potentially requiring manual manipulation. Functionally, reproductive traces support elevated body temperatures and a metabolic output that approach but do not equal that of modern birds. Brooding would require very high energy investment from the adult. The regurgitalites largely contain multi-individual aggregations of the marsupialiform Alphadon and support Russell's hypotheses of troodontids as crepuscular to nocturnal, intelligent, small game hunters with elevated metabolism and enhanced vision. Tool use in a few crocodilians and widely among extant birds suggests a reasonable possibility of this behavior in nonavian dinosaurs. Whether an avian-comparable encephalization quotient and freed forelimbs would make North American troodontids good candidates for exhibiting such behavior remains an open and speculative question. However, given the minimal modification made to tools by modern archosaurs, recognition of fossil tools poses a challenging problem. Key words: Troodon, troodontid, reproduction, encephalization quotient, regurgitalites, gastric pellets, trace fossils, tool use, physiology. Dale Russell a decrit l'osteologie, la morphologie et l'ecologie du petit theropode [much less than] Stenonychosaurus inequalis [much greater than] dans deux articles, emettant des hypotheses sur ses habitudes de vie, ses capacites cerebrales, sa vision, ses deplacements, son alimentation et sa dexterite. Il a meme envisage un dinosauroide se servant d'outils, ledescendant hypothetiquede troodontides, si cette lignee devait avoir survecu a l'extinction du Cretace-Paleogene. Nous reexaminons les habitudes de vie des troodontides nord-americains Troodon formosus et Latenivenatrix mcmasterae en partie par l'examen de differents ichnofossiles de T. formosus decouverts au Montana. Ceux-ci comprennent des pontes, un nid et des regurgitalites decouvertes recemment. Nous considerons egalement la possibilite d'utilisation d'outils par des dinosaures. Les Troodon construisaient vraisemblablement des nids de terre a l'instar de ratites ou autres oiseaux qui font leurs nids en creusant la terre par des coups de leurs membres posterieurs vers l'arriere. L'architecture complexe des pontes semble indiquer une grande dexterite pour deplacer les ceufs, necessitant potentiellement une manipulation manuelle. Du point de vue fonctionnel, les ichnofossiles associes a la reproduction appuient l'interpretation de temperatures elevees du corps et d'un metabolisme s'approchant de celui des oiseaux modernes, sans toutefois l'egaler. La couvaison aurait requis un tres grand investissement energetique des adultes. Les regurgitalites contiennent principalement des agregations de restes de plusieurs individus du marsupialiforme Alphadon et appuient les hypotheses de Dale Russell selon lesquelles les troodontides etaient des chasseurs crepusculaires a nocturnes et intelligents de petit gibier caracterises par un metabolisme eleve et une excellente vue. L'utilisation d'outils chez quelques crocodiliens et tres repandue chez les oiseaux actuels laisse entrevoir une possibilite raisonnable d'un tel comportement chez des dinosaures non aviens. La question a savoir si un quotient d'encephalisation semblable a celui des oiseaux et des membres anterieurs liberes pourraient faire des troodontides nord-americains des bons candidats pour presenter un tel comportement demeure ouverte et hypothetique. Etant donne le peu de modifications apportees aux outils par les archosaures modernes, la reconnaissance d'outils fossiles constitue un defi problematique. [Traduit par la Redaction] Mots-cles: Troodon, troodontides, reproduction, quotient d'encephalisation, regurgitalites, boulettes gastriques, ichnofossiles, utilisation d'outils, physiologie., Introduction Dale Russell summarized the osteology, morphology, and ecology of the troodontid dinosaur 'Stenonychosaurus inequalis' in two papers (Russell 1969; Russell and Seguin 1982). In the first paper, Russell (1969) [...]
- Published
- 2021
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11. Salt anomalies in potash beds of the Esterhazy Member, Devonian Prairie Evaporite Formation, Saskatchewan, Canada
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Cisyk, David E.
- Subjects
Earth sciences - Abstract
The Esterhazy Member of the western Canada Prairie Evaporite has been mined underground for sylvite (KCl) since the early 1960s. Although the geology of the Esterhazy Member ore body is largely considered a regional flat lying continuous series of thin potash hosting beds, there are numerous occurrences where the ore has been either replaced or removed leaving behind uneconomical halite-rich sections. An explanation of the underlying controls on the formation of these salt anomalies has been somewhat elusive although the overwhelming assumption remains that these features developed in lows on a salina. This paper proposes that salt anomalies formed because of two processes, early compaction of carbonate shoals of the Winnipegosis Formation and tectonics that resulted in multiple stages of block movement during the deposition of the upper Prairie Evaporite. Since these two processes can result in a significantly different size to a salt anomaly, encountering one or the other type can have a significant effect on the economics of the ore body. This paper looks at some of the geological methods that might provide geologists with means to predicting salt anomalies. Key words: Prairie Evaporite Formation, potash mining, salt anomalies, Winnipegosis Formation. Le membre d'Esterhazy de la Formation d'evaporite des Prairies de l'Ouest canadien fait l'objet d'une exploitation souterraine pour la sylvite (KCl) depuis le debut des annees 1960. Si la geologie du membre d'Esterhazy est generalement consideree comme etant une serie generalement horizontale et continue a l'echelle regionale de minces lits contenant de la potasse, dans de nombreux endroits, le minerai a ete soit remplace ou retire, laissant des sequences riches en halite sans interet sur le plan economique. L'explication des controles qui sous-tendent la formation de ces anomalies de sel s'est averee quelque peu problematique, bien que l'hypothese dominante demeure voulant qu'elles se soient formees dans des depressions dans une salina. Le present article propose que les anomalies de sel se sont formees en raison de deux processus, soit la compaction precoce de haut-fond de carbonates de la Formation de Winnipegosis et une tectonique qui a produit differentes phases de deplacement de blocs durant le depot de la partie superieure de la Formation d'evaporite des Praires. Comme ces deux processus peuvent produire des anomalies de sel de tailles significativement differentes, le fait de rencontrer l'un ou l'autre des deux types peut avoir une importante incidence sur les parametres economiques du corps mineralise. L'article se penche sur certaines des methodes geologiques qui pourraient aider les geologues a predire les anomalies de sel. [Traduit par la Redaction] Mots-cles: Formation d'evaporite des Prairies, exploitation de la potasse, anomalies de sel, Formation de Winnipegosis., Introduction The Prairie Evaporite Formation of Saskatchewan, Canada, is a Devonian evaporite deposit of Givetian age, and a world class source of sylvite (KCl). The formative Elk Point Basin, which [...]
- Published
- 2020
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12. The theory of undercurrent from the Austrian alpine geologist Otto Ampferer (1875-1947): first conceptual ideas on the way to plate tectonics
- Author
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Dullo, Wolf-Christian and Pfaffl, Fritz A.
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Hydrothermal systems (Geology) -- Surveys -- Analysis ,Sea-floor spreading -- Surveys -- Analysis ,Geospatial data -- Surveys -- Analysis ,Tectonics (Geology) -- Surveys -- Analysis ,Earth -- Mantle ,Earth sciences - Abstract
In his paper 'Uber das Bewegungsbild von Faltengebirgen' [On the movement pattern of folded mountains], published in the almanac of the Austrian Geological Survey in Vienna, Otto Ampferer from Innsbruck (Austria) presented a series of geotectonic considerations and interpretations, which today are summarized under the term 'theory of undercurrent'. The interpretation of these processes occurring in the deep crust of the Earth and in the upper mantle was mainly kinematic. For a long time, the tectonic passivity of the magma being anorogenic was dogma until Ampferer's undercurrent theory changed this in 1906, according to which folds and thrusts on the Earth's surface portray motions of the deeper magmatic substratum. In these undercurrents, Ampferer recognized the crucial forces that lead to the formation of ocean basins and high mountains on the edges of the drifting continents. In his paper on the history of the formation of the Atlantic region, he presented already, in 1941, a process anticipating what is now known as seafloor spreading. Dans son article intitule <>, publie dans l'almanach de la Commission geologique d'Autriche a Vienne, Otto Ampferer, d'Innsbruck (Autriche), presentait une serie de considerations et d'interpretations geotectoniques que resume aujourd'hui le terme<>. L'interpretation de ces processus se produisant dans la croute profonde de la terre et dans le manteau superieur etait principalement cinematique. Longtemps, la passivite tectonique du magma comme etant anorogenique etait un dogme, jusqu'a l'avenement de la theorie des sous-courants d'Ampferer en 1906, selon laquelle les plis et chevauchements a la surface de la Terre refletent des mouvements du substrat magmatique plus profond. Dans ces sous-courants, Ampferer reconnaissait des forces cruciales menant a la formation de bassins oceaniques et de hautes montagnes aux bordures des continents en derive. Dans son article sur l'histoire de la formation de la region atlantique, il presentait deja, en 1941, un processus qui anticipait ce que nous designons aujourd'hui l'expansion des fonds oceaniques., Biography Otto Ampferer was born on 1 December 1875 in Hotting near Innsbruck (Tyrol, Austria). His father was a postman and he, as well as his wife, came from old [...]
- Published
- 2019
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13. Landscape and Seascape Responses to Canada's Changing Climate.
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James, Thomas S., Blais-Stevens, Andrée, Clague, John J., Forbes, Donald L., LeBlanc, Anne-Marie, and Smith, Sharon L.
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CLIMATE change ,EARTH sciences ,BARRIER islands ,LANDSCAPES ,GLACIAL isostasy - Abstract
An introduction is presented in which the editor discusses articles within the issue on topics including changes occurring on the Earth's surface across a spectrum of spatial and temporal scales, influence of climate change on the Earth's surface in northern and coastal regions, and features and landforms generated during decline and aftermath of continental glaciation.
- Published
- 2022
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14. Petrogenesis and geochemical evidence from early Jurassic intrusive rocks and their implications for subduction of the Paleo-Pacific Plate in the Yanbian area, Northeast China
- Author
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Zhang, Xinwen, Sun, Jinggui, Xu, Zhikai, Liu, Yang, and Zhao, Chuntao
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Manchuria -- Natural history ,Plate tectonics -- Research ,Petrogenesis -- Research ,Intrusions (Geology) -- Chemical properties -- Natural history ,Subduction zones (Geology) -- Chemical properties -- Natural history ,Earth sciences research ,Earth sciences - Abstract
Subduction of the Paleo-Pacific Plate plays a key role in the Early Jurassic magmatism evolution in the Yanbian area, Northeast China. In this paper, zircon U-Pb ages, whole-rock geochemical, and Sr-Nd-Hf isotopic compositions are presented. The Early Jurassic gabbros, diorite enclaves, granodiorites, and granites ages range from 183 to 189 Ma. They are characterized by enrichment in large-ion lithophile elements and depletion in high-field strength elements. The gabbros are classified as low-and medium-K tholeiitic, granodiorites and granites are high-K calc-alkaline I-type, and diorite enclaves are calc-alkaline transitional series. The gabbros have zircon [epsilon] Hf(t) values of 6.81-9.89, whole-rock [.sup.87]Sr/[.sup.86][Sr.sub.(i)] = 0.7043-0.7044, and [epsilon] Nd(t) from 2.72 to 2.80. The diorite enclaves have zircons with [epsilon] Hf(t) values of 8.26-12.80, whole-rock [.sup.87]Sr/[.sup.86][Sr.sub.(i)] = 0.7051, and [epsilon] Nd(t) from 0.96 to 1.09. The granodiorites and granites have zircon [epsilon] Hf(t) values of 7.59-12.87, whole-rock [.sup.87]Sr/[.sup.86][Sr.sub.(i)] = 0.7042-0.7066, and [epsilon]Nd(t) from 2.33 to 2.61. These data indicate that gabbroic magmas were derived from partial melting of a depleted mantle wedge metasomatized by subduction-related fluids. The basaltic magma underplated and heated the juvenile crust, whereas the granodiorites and granites might be the product of fractional crystallization of a mixture of basaltic and felsic magmas or derived from partial melting of the juvenile lower crust. Our data constrain the petrogenesis of these Early Jurassic intrusive rocks which are attributed to subduction of the Paleo-Pacific Plate beneath Eurasia continent in northeastern China. Key words: Early Jurassic, intrusive rocks, petrogenesis, Paleo-Pacific Plate subduction, Sr-Nd-Hf isotope, Yanbian area, 1. Introduction Understanding the generation and emplacement of granitic magmas is necessary to deduce the internal structure, formation, and evolution of continental crust (Pearce 1983; Barbarin 1999; Condie and Kroner [...]
- Published
- 2023
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15. Late Paleoarchean to Neoarchean sedimentation on the Singhbhum Craton, eastern India: a synthesis
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De, Shuvabrata, Mazumder, Rajat, Chaudhuri, Trisrota, and Bauer, Wilfried
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Cratons -- Environmental aspects ,Geomorphology -- Analysis ,Sedimentation -- Analysis ,Sedimentary basins -- Environmental aspects ,Facies (Geology) -- Environmental aspects ,Earth sciences - Abstract
Subaerial rise of Earth's first continents took place 3.3-3.2 Ga years ago. This had significant influence on the ocean, atmosphere, and biosphere. Two important sedimentological consequences of continental emersion were (1) development of terrestrial (alluvial fan-fluvial-aeolian) depositional systems and (2) formation of shallow-marine sedimentary basins near the continental margin. Late Paleoarchean-Neoarchean terrestrial deposits, including development of an extensive paleosol around 3.2 Ga, and Meso-Neoarchean shallow-marine deposits have been reported from the Singhbhum Craton, eastern India from several localities. However, lateral and vertical changes in sedimentary facies associations and stratigraphic correlation between these terrestrial to shallow-marine sedimentary deposits have not yet been investigated. In this paper, we have reviewed the sedimentological characteristics of Late Paleoarchean to Neoarchean (3.2-2.8 Ga) stratigraphic successions of the Singhbhum Craton and have discussed sea level change and mode of stratigraphic sequence building. Our analysis shows that Singhbhum granitoid complex was emplaced around 3.3 Ga in an intracontinental setting, resulting in high continental freeboard conditions that triggered terrestrial (alluvial fan-braided fluvial) sedimentation (Dhosrapahar Formation). Continental sedimentation continued until ca. 3.0 Ga. In the eastern (Simlipal Group), western (Birtola Formation), and southwestern (the Mankarchua, Mahagiri, and Keonjhar formations) parts, shallow-marine sedimentation occurred after 3.0 Ga as a result of transgression. However, in the northern part (Dhanjori Formation), continental sedimentation prevailed throughout the Archean. These Late Paleoarchean to Neoarchean terrestrial and near-coastal successions of Singhbhum Craton should be the prime targets for intense geobiological research. Key words: Paleoarchean, Mesoarchean, sedimentation, continental emergence, Singhbhum Craton, India, 1. Introduction It has been proposed that significant increase of continental freeboard (elevation of continents from the mean sea level, Taylor and McLennan 1985) took place in the early Paleoproterozoic [...]
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- 2023
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16. Detrital zircon geochronology and provenance of the Mesoproterozoic Husky Creek Formation: a fluvial sandstone recording the waning stages of one of Earth's largest magmatic episodes
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Meek, Robert D., Ielpi, Alessandro, Rainbird, Robert H., and Davis, William J.
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Zircon -- Composition -- Testing ,Large igneous provinces -- Environmental aspects ,Geochronology -- Analysis ,Geomorphology -- Analysis ,Sandstone -- Composition -- Testing ,Volcanism -- Analysis ,Earth sciences - Abstract
The Mesoproterozoic Husky Creek Formation is an interlayered redbed and basalt package that overlies a ca. 2.5 km thick, regionally extensive basaltic plateau linked to the 1.27 Ga Mackenzie Large Igneous Province. This succession provides an opportunity to study the interaction between contemporaneous fluvial sedimentation and flood basalt volcanism. The Husky Creek Formation is approximately 1900 m thick, consisting predominantly of fluvial channel and subordinate floodplain and eolian strata dominated by lithic detritus intercalated with basalt flows. U-Pb dating of detrital zircon grains collected from four stratigraphic levels in the Husky Creek Formation reveals two main age groupings: (1) a 1270 Ma peak attributed to the Mackenzie Large Igneous Province; and (2) Pre-1.6 Ga detrital zircon ages, which reflect sources from a broad region of northwestern Laurentia and are interpreted to be recycled from underlying sedimentary rocks of the Hornby Bay Basin. An upsection decrease in the proportion of ca. 1270 Ma zircon grains, coupled with increasing sandstone compositional maturity, reflects the expansion of the drainage basin during burial of a volcanic pile, with recycling becoming more dominant as the Husky Creek Formation accumulated. The Husky Creek Formation was deposited in the waning stages of the Mackenzie Igneous Event by west-flowing rivers into a geographically restricted basin above an extensive mafic volcanic plateau. This paper provides insight into fluvial basin development during the aftermath of one of Earth's largest igneous events. Key words: fluvial sedimentology, Mackenzie LIP, Husky Creek Formation, Mesoproterozoic, detrital zircon geochronology, Introduction Large igneous provinces (LIPs), and particularlycontinental flood basalts, have been a subject of substantial research targeting their relationship to mantle plumes and continental breakup (Ernst and Buchan 1997). While [...]
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- 2023
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17. Significance of the metasomatized lithospheric mantle in the formation of early basalts and Cu--platinum group element sulfide mineralization in the Coldwell Complex, Midcontinent Rift, Canada
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Good, David J. and Lightfoot, Peter C.
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Rare earth metals ,Basalt ,Earth -- Mantle ,Sulfides ,Magmatism ,Earth sciences - Abstract
A diverse suite of tholeiitic to alkaline basalt and gabbroic intrusions located in the Coldwell Complex on the northern margin of the Midcontinent Rift exhibit unusual trace element signatures that show enriched large ion lithophile elements and light rare earth elements with negative Nb and Zr anomalies. These features are not typical of magmas derived by partial melting within or above a rising mantle plume, as might be expected in an early Midcontinent Rift magmatic event. In this paper, we provide a detailed geochemical study of a 500 m thick sequence of metabasalt that represents the earliest stage of magmatism in the Coldwell Complex. We show that contamination or crystallization processes or subsequent metasomatism cannot explain the trace element variations. Instead, we propose partial melting in a metasomatized Subcontinental Lithospheric Mantle source to explain the decoupled behavior of large ion lithophile elements from light rare earth elements and heavy rare earth elements and rare earth elements from high field strength elements and the enriched Nd isotope signature of metabasalt. Similar features occur in unit 5b of the Mamainse Point Volcanic Group located at the northern margin of the Rift. An objective of this paper is to relate Two Duck Lake gabbro, host rock for low-sulfur, high precious metal sulfide mineralization at the Marathon deposit, to the metabasalt sequence. The excellent match of trace element abundances in Two Duck Lake gabbro to metabasalt unit 3 confirms an early Coldwell Complex age for metabasalt and a Subcontinental Lithospheric Mantle source for Cu--platinum group element mineralized gabbros. Une succession diversifiée de basaltes tholéiitiques à alcalins et d'intrusions gabbroïques située dans le complexe de Coldwell à la bordure nord du rift médio-continental présente des signatures d'éléments traces inhabituelles qui montrent un enrichissement en éléments lithophiles à grand rayon ionique et en terres rares légères avec des anomalies négatives de Nb et Zr. Ces caractéristiques ne sont pas typiques de magmas issus d'une fusion partielle au-dessus d'un panache mantellique ascendant ou à l'intérieur de celui-ci, à l'instar de ce qui serait attendu durant un épisode magmatique associé au début du rifting médio-continental. Nous présentons une étude géochimique détaillée d'une séquence de 500 m d'épaisseur de métabasaltes qui représente le tout début du magmatisme dans le complexe de Coldwell. Nous démontrons que des processus de contamination ou de cristallisation ou encore un métasomatisme subséquent ne peuvent expliquer les variations des éléments traces. Nous proposons plutôt que la fusion partielle dans une source dans le manteau lithosphérique subcontinental métasomatisé explique le découplage du comportement des éléments lithophiles à grand rayon ionique de celui des terres rares légères et des terres rares lourdes, et le découplage du comportement des terres rares de celui des éléments à forte liaison atomique, ainsi que la signature enrichie des isotopes de Nd des métabasaltes. Des caractéristiques semblables sont observées dans l'unité 5b du Groupe volcanique de Mamainse Point situé à la bordure nord du rift. Un des objectifs du présent article est de relier le gabbro de Two Duck Lake, la roche hôte de la minéralisation en sulfures riche en métaux précieux et pauvre en soufre au gisement Marathon, à la séquence de métabasaltes. L'excellente concordance des abondances d'éléments traces dans le gabbro de Two Duck Lake et dans l'unité 3 des métabasaltes confirme un âge du début de la formation du complexe de Coldwell pour les métabasaltes et une source dans le manteau lithosphérique subcontinental pour les gabbros minéralisés en Cu--élément du groupe platine. [Traduit par la Rédaction], Introduction The Coldwell Complex (CC) in Ontario, Canada (Fig. 1), provides not only a complete record of alkaline intrusive magmatism (Mitchell and Platt 1978, 1982; Mitchell et al. 1993) during [...]
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- 2019
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18. Rapid coastal erosion of ice-bonded deposits on Pelly Island, southeastern Beaufort Sea, Inuvialuit Settlement Region, western Canadian Arctic
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Malenfant, François, Whalen, D., Fraser, P., and Proosdij, D. van
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Deltas -- Research ,Geomorphological research ,Beach erosion -- Research ,Earth sciences - Abstract
This paper quantifies rates of shoreline change and investigates the influence of surficial geology on shoreline dynamics between 1950 and 2018 on Pelly Island, located 10 km off the Mackenzie Delta. Long-term changes in shoreline position were calculated using imagery analysis and Analysing Moving Boundaries Using R (AMBUR). The influence of shoreline exposure to predominant storm direction and influence of surficial geology were examined for northwestern and southeastern zones. The average annual linear regression rate (LRR) rate during the 1950-2018 observation period was -3.8 m*[a.sup.-1]. The end point rate (EPR) was calculated for seven observation periods: 1950-1972, 1972-1985, 1985-2000, 2000-2018, 2000-2013, 2013-2018, and 1950-2018. A mean EPR of -5.5 [+ or -] 0.7 m*[a.sup.-1] was calculated for the 2000-2018 period, and a maximum retreat rate of 46.7 [+ or -] 2.1 m*[a.sup.-1] was recorded during the 2013-2018 observation period. By comparing the rate of change for sections of historical shorelines with differing surficial geology and exposure to storms, it was possible to draw conclusions on why Pelly Island continues to have the highest retreat rates in the Mackenzie-Beaufort region. Greater retreat rates were observed in lacustrine deposits (5.3 m*[a.sup.-1]) compared with moraine deposits (2.7 m*[a.sup.-1]). In addition, shoreline exposure to the predominant storm direction from the northwest was found to be a major influence on rates of shoreline change in all observation periods. Key words: imagery analysis, shoreline retreat, surficial geology, exposure to storms. Le présent article quantifie les taux de changement des berges et explore l'influence de la géologie de surface sur la dynamique des berges de 1950 à 2018 autour de l'île Pelly, située à 10 km au large du delta du fleuve Mackenzie. Les variations à long terme de l'emplacement des berges ont été calculées à l'aide de l'analyse d'images et du logiciel AMBUR (Analysing Moving Boundaries Using R). L'influence de l'exposition des berges à la direction dominante des tempêtes et l'influence de la géologie de surface ont été examinées pour les secteurs nord-ouest et sud-est. Le taux de recul linéaire (TRL) annuel moyen durant la période d'observation de 1950 à 2018 est de -3,8 m*[a.sup.-1]. Le taux entre points de fin (TPF) a été calculé pour sept périodes d'observation, à savoir : 1950-1972, 1972-1985, 1985-2000, 2000-2018, 2000-2013, 2013-2018 et 1950-2018. Un TRL moyen de -5.5 [+ or -] 0,7 m*[a.sup.-1] a été calculé pour la période de 2000-2018 et un taux de recul maximum de 46,7 [+ or -] 2,1 m*[a.sup.-1] a été enregistré durant la période d'observation de 2013-2018. En comparant le taux de changement pour des sections de berges passées présentant différentes geologies de surface et expositions aux tempêtes, il est possible de tirer des conclusions sur les raisons pour lesquelles l'île Pelly continue de présenter les taux de recul les plus élevés de la région de Mackenzie-Beaufort. Les taux de recul observés sont plus importants pour les dépôts lacustres (5,3 m*[a.sup.-1]) que pour les dépôts de moraine (2,7 m*[a.sup.-1]). En outre, l'exposition des berges à la direction dominante des tempêtes émanant du nord-ouest s'avère exercer une influence majeure sur les taux de changement des berges pour toutes les périodes d'observation. [Traduit par la Rédaction] Mots-clés : analyse d'image, recul de berges, géologie de surface, exposition aux tempêtes., Introduction During the 1950-2000 period, permafrost coastlines along the circum-Arctic were eroding at a mean rate of -0.5 m*[a.sup.-1] (Lantuit et al. 2012). Some of the highest reported rates of [...]
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- 2022
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19. Taphonomy and depositional history of the Southfork Quarry (Cypress Hills Formation, late Eocene) in southwestern Saskatchewan, Canada
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Gilbert, Meagan M. and Mcdougall, Frank H.
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Saskatchewan -- Natural history ,Rock formations -- Research ,Formations (Geology) -- Research ,Sedimentation and deposition -- Research ,Geological research ,Earth sciences - Abstract
The Eocene to Miocene Cypress Hills Formation (CHF) spans 28 million years and forms the conglomeratic caprock of the Cypress Hills and Swift Current plateaus in southwestern Saskatchewan and southeastern Alberta. These stacked fluvial, floodplain, and lacustrine deposits preserve the only high latitude, non-polar mammalian fossil assemblage (Uintan to Hemingfordian land mammal stages) in Canada. The Quarry is the oldest CHF (Chadronian 1, late Eocene) site documented in the Cypress Hills region north of the town of Eastend. The Quarry was originally discovered in 1962, after bones were found to be eroding out of the base of a road cut north of the ghost town of South Fork on the southeastern flanks of the Cypress Hills. Numerous field campaigns have resulted in the collection of fossils from a multitaxonomic bonebed. This paper presents a detailed sedimentologic, paleontologic, and taphonomic study to establish a depositional environment framework of the Southfork Quarry. This site was deposited at the onset of the Eocene--Oligocene climate transition, a critical time of climate change during the Paleogene. Six facies and two facies associations are characterized for the Quarry, shifting from a braided-fluvial system to a debris flow-filled incised channel. Patterns of skeletal accumulations and bone surface modification indicate that the assemblage accumulated over a significant interval of time in different depositional environments. This study provides critical insight into environmental shifts driven by climate change and relates these findings to a broader understanding of the Eocene--Oligocene transition in North America. Key words: Paleogene, fluvial, Western Canada, Chadronian, Megacerops coloradensis La Formation éocène à miocène des collines du Cyprès couvre 28 millions d'années et forme la roche conglomératique recouvrant les plateaux des collines du Cyprès et de Swift Current dans le sud-ouest de la Saskatchewan et le sud-est de l'Alberta. Ces dépôts fluviaux, lacustres et de plaine inondable empilés préservent le seul assemblage fossile mammalien non polaire de haute latitude (étages mammaliens continentaux Uintien à Hemingfordien) au Canada. La carrière Southfork représente le site de la Formation des collines du Cyprès (Chadronien 1, ?ocène tardif) le plus ancien documenté dans la région des collines du Cyprès au nord du village d'Eastend. La carrière a été découverte en 1962, après la découverte d'ossements exposés par l'érosion à la base d'une tranchée de route au nord du village fantôme de South Fork, sur les flancs sud-est des collines du Cyprès. De nombreuses campagnes de terrain se sont traduites par la collecte de fossiles d'un lit à ossements multitaxonomique. L'article présente une étude sédimentologique, paléontologique et taphonomique détaillée visant à établir un cadre pour le milieu de dépôt de la carrière de Southfork. Ce site a été déposé au début de la transition climatique éocène-oligocène, une période de changement climatique clé durant le Paléogène. Six faciès et deux associations de faciès sont caractérisés pour la carrière, passant d'un réseau fluvial anastomosé à un chenal encaissé rempli par des coulées de débris. Les motifs d'accumulation de squelettes et de modification des surfaces des os indiquent que l'assemblage s'est accumulé durant un intervalle de temps important dans différents milieux de dépôt. L'étude fournit de nouveaux renseignements clés sur des changements environnementaux induits par des changements climatiques et relie ces constatations à une compréhension plus large de la transition de l'?ocène à l'Oligocène en Amérique du Nord. [Traduit par la Rédaction] Mots-clés : Paléogène, fluvial, Ouest canadien, Chadronien, Megacerops coloradensis, Introduction The Eocene toMiocene Cypress Hills Formation (CHF) spans 28 million years, forming the conglomeratic caprock of the Cypress Hills plateau in southwestern Saskatchewan and southeastern Alberta (Fig. 1). The [...]
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- 2022
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20. Regional geology and tectonic framework of the Southern Indian domain, Trans-Hudson orogen, Manitoba
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Martins, T., Rayner, N., Corrigan, D., and Kremer, P.
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Manitoba -- Environmental aspects -- Natural history ,Geochronology -- Research ,Geological research ,Tectonics (Geology) -- Research ,Earth sciences - Abstract
The collaborative federal--provincial Southern Indian Lake project in north-central Manitoba covered an area of more than 3500 [km.sup.2] of the Trans-Hudson orogen. Regional-scale geological mapping, sampling, and lithogeochemical, isotopic, and geochronological studies resulted in the identification of distinct assemblages of supracrustal rocks and varied episodes of plutonism. A granodiorite gneiss dated at ca. 2520 Ma is interpreted to represent the basement of the Southern Indian domain and is considered a separate crustal domain, named the Partridge Breast block. The Churchill River assemblage is composed of juvenile pillow basalt with intervening clastic sedimentary rocks, possibly a reflection of plume magmatism related to initial rifting of the Hearne craton margin. The Pukatawakan Bay assemblage consists mainly of massive to pillowed, juvenile metabasaltic rocks and associated basinal metasedimentary rocks. The Partridge Breast Lake assemblage is dominated by continental-arc volcanic and volcaniclastic rocks associated with basinal metasedimentary rocks. The Strawberry Island assemblage, consisting of arenite and polymictic conglomerate, is interpreted to have been deposited in a foreland-basin basin or intra-orogen pull-apart basin environment. The Whyme Bay assemblage is characterized by fluvial-alluvial orogenic sediments and is temporally linked to the Sickle Group rocks in the Lynn Lake greenstone belt. Granitoid rocks, dominantly monzogranite and granodiorite, range in age from ca. 1890 to 1830 Ma and occur throughout the Southern Indian domain, and intermediate and mafic intrusions of similar ages are also present. In this paper, we integrate these new data into a tectonic framework for the Southern Indian domain of the Trans-Hudson orogen in Manitoba. Key words: tectonics, Trans-Husdon orogen, regional geology, Manitoba, Southern Indian domain, geochemistry, detrital geochronology. Resume : Le projet du lac Southern Indian, une collaboration federale--provinciale, dans le centre-nord du Manitoba, a couvert une superficie de plus de 3500 [km.sup.2] de l'orogene trans-hudsonien. La cartographie geologique, l'echantillonnage et des etudes lithogeochimiques, isotopiques et geochronologiques a l'echelle regionale ont mene a la delimitation de differents assemblages de roches supracrustales et episodes de plutonisme. Un gneiss granodioritique ayant donne un age d'environ 2520 Ma est interprete comme representant le socle du domaine de Southern Indian et constituant un domaine crustal distinct appele le bloc de Partridge Breast. L'assemblage du fleuve Churchill est compose de basaltes en coussins juveniles dans lesquels sont intercalees des roches sedimentaires clastiques, refletant possiblement un magmatisme de panache associe au rifting initial de la bordure du craton de Hearne. L'assemblage de la baie de Pukatawakan est principalement constitue de roches metabasaltiques juveniles massives a en coussins et de roches metasedimentaires de bassin associees. Dans l'assemblage du lac Partridge Breast, des roches volcaniques et volcanoclastiques d'arc continental associees a des roches metasedimentaires de bassin sont dominantes. L'assemblage de File Strawberry, constitue d'arenites et de conglomerate polymictiques, est interprete comme ayant ete depose dans un milieu de bassin d'avant-pays ou de bassin de transtension intraorogenique. L'assemblage de la baie de Whyme est caracterise par des sediments orogeniques fluviaux-alluviaux et est relie dans le temps aux roches du Groupe de Sickle dans la ceinture de roches vertes du lac Lynn. Des roches granitoides a predominance de monzogranite et granodiorite ont des ages allant d'environ 1890 a 1830 Ma et sont presentes partout dans le domaine de Southern Indian, et des intrusions intermediaires et mafiques d'ages semblables sont egalement presentes. Le present article integre ces nouvelles donnees dans un cadre tectonique pour le domaine de Southern Indian de l'orogene trans-hudsonien au Manitoba. [Traduit par la Redaction] Mots-cles: tectonique, orogene trans-hudsonien, geologie regionale, Manitoba, domaine de Southern Indian, geochimie, geochronologie de mineraux detritiques., Introduction The 'Trans-Hudson orogen' (THO) (Hoffman 1981; Lewry et al. 1981) is the belt of deformed and metamorphosed rocks that developed as a result of the Paleoproterozoic closure of the [...]
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- 2022
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21. Multi-criteria assessment approach of slow-moving urban landslide hazard: the case of Moulay Yacoub, Morocco
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Obda, Ilias, Kharim, Younes El, Bounab, Ali, Lahrach, Abderrahim, Ahniche, Mohammed, and Mansouri, Hamou
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Building failures -- Environmental aspects -- Morocco ,Landslides -- Environmental aspects -- Models ,Urbanization -- Environmental aspects ,Structural stability -- Environmental aspects ,Earth sciences - Abstract
During many decades, the town of Moulay Yacoub underwent an important urban expansion to meet the high demand on housing fuelled by tourism activities, which constitute the backbone of the town's economy. Unfortunately, the majority of buildings, both private and public, suffer from varying levels of damage related to the lithological, climate, and geomorphic settings of the area. In fact, the town is built on a marly hill prone to various types of mass movements, ranging from shallow soil creep to large slides. In addition, vertical displacement related to swelling/shrinkage behaviour of these Miocene marls is widespread in the area. The present paper presents a multi-disciplinary approach to investigate the activity and the interaction between slow-moving urban landslides and expansive soils within the urban perimeter of Moulay Yacoub. In fact, the severe seasonal contrast characterised by intense rainfall over short periods constitutes the main triggering factor of the instability phenomena in the region. Moreover, the desiccation cracks affecting marly soils are indicators of their expansive behaviour, which is very obvious in geotechnical tests results. The other geotechnical parameters obtained from laboratory tests show that the shallow marl samples are severely weathered compared with those of the compact material extracted at greater depth. The borehole data and seismic noise survey allows the detection of several impedance contrasts corresponding to the weathered layer--bedrock boundary, which in some cases corresponds to the rupture surface of the inventoried landslides. The very slow but perennial activity of the later processes is well documented by the inclinometers, the PS-InSAR monitoring, and building damage assessment surveys. Indeed, this case study highlights the complementarity of techniques used in this multi-disciplinary approach that give a multi-faceted understanding of slope instability processes and should provide a blueprint for future site-specific studies in the region. Key words: urban landslide, expansive soils, multi-disciplinary analysis, building damage. Pendant de nombreuses décennies, la ville de Moulay Yacoub a connu une importante urbanisation en réponse à la forte demande de logements induite par l'activité touristique, qui constitue l'épine dorsale de l'économie de la ville. Mal-heureusement, la majorité des immeubles, tant privés que publics, ont subi des dommages d'intensité variable associés aux contexte lithologique, climatique et géomorphologique de la région. La ville est en effet construite sur une colline mar-neuse propice à différents types de mouvements de terrain allant du fluage de sols peu profonds à de grands glissements. En outre, des déplacements verticaux associés au comportement de gonflement et retrait de ces marnes miocènes sont répandus dans la région. L'article présente une approche multidisciplinaire à l'étude de l'activité et des interactions de glissements de terrain urbains de faible vélocité et de sols gonflants à l'intérieur du périmètre urbain de Moulay Yacoub. L'important contraste saisonnier caractérisé par des pluies intenses sur de courtes périodes est le principal élément déclen-cheur de phénomènes d'instabilité dans la région. En outre, des fissures de dessiccation en terrains marneux constituent des indicateurs du comportement gonflant de ces derniers, que les résultats d'essais géotechniques font clairement ressortir. Les autres paramètres géotechniques obtenus d'essais en laboratoire montrent une intense météorisation des échantillons de marnes peu profondes comparativement aux matériaux compacts à plus grande profondeur. Les données de forage et levés de bruit sismique font ressortir plusieurs contrastes d'impédance correspondant au contact de la couche météori-sée et du roc qui, dans certains cas, coïncide avec la surface de rupture des glissements de terrain recensés. L'activité très lente, mais soutenue des processus plus récents est bien documentée par les essais inclinométriques, la surveillance par PS-InSAR et les évaluations des dommages aux bâtiments. La présente étude de cas souligne notamment la complémentarité des techniques utilisées dans cette approche multidisciplinaire, qui permet une compréhension multifactorielle des processus d'instabilité des pentes et devrait constituer un modèle pour des études de site futures dans la région. [Traduit par la Rédaction] Mots-clés : glissement de terrain urbain, sols gonflants, analyse multidisciplinaire, dommages aux immeubles., Introduction Slope mass movements are among the most widespread geological hazards in the world (Schuster 1996; Schuster and Highland 2001). In urban extensions worldwide, the local construction and land use [...]
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- 2022
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22. Quartz arenites of the Cambro-Ordovician Kamouraska Formation, Quebec Appalachians, Canada: II. Eolian sands in deep-sea sedimentary gravity-flow deposits
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Malhame, Pierre and Hesse, Reinhard
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Quebec -- Natural history ,Appalachian Mountains -- Natural history ,Sand -- Natural history -- Environmental aspects ,Geological research ,Sedimentation -- Research ,Earth sciences - Abstract
The Kamouraska Formation is a quartz-arenitic unit of latest Cambrian--earliest Ordovician age in the Quebec Appalachians that was deposited by hyperconcentrated to concentrated density flows in a meandering submarine canyon on the continental slope bordering the Iapetus Ocean, as outlined in a companion paper. Detailed petrographic study of the quartz arenites of the Kamouraska Formation combined with scanning electron microscopy of grain surface textures suggests that the quartz sands are of eolian origin having been derived from an inland desert or, less likely, a barrier beach dune system. Transport of the mature quartz-arenitic sand onto the shelf and deposition into the deep sea was not accompanied by substantial mixing with material from other sources thus preserving the inherited eolian characteristics. A modern analogue for the eolian interpretation of the deep-sea quartz-arenite beds is as follows: thick, Late Pleistocene eolian sand beds on a modern abyssal plain in the East Atlantic referred to as eolian-sand turbidites that were deposited in the deep sea during glacial sea level lowstands when eolian sand transport to canyon heads was enabled by an exposed and shortened shelf. Similarly, an established sea level lowstand at the Cambro-Ordovician boundary would have facilitated the introduction of eolian sand of the Kamouraska Foundation into canyon heads on the upper slope from where turbidity currents and related density flows were triggered. Correlation of the Kamouraska Formation with the quartz arenites of the Cairnside Formation of Quebec (Keeseville Formation in northern New York State, Nepean Formation in southern Ontario) links the deep-sea deposits with remnants of an inland dune system. La Formation de Kamouraska est constituee d'une unite d'arenite quartzique (Cambrien superieur--Ordovicien inferieur) dans les Appalaches du Quebec; elle a ete deposee par des courants de densite hyperconcentres a concentres dans un canyon sous-marin a meandres sur la pente continentale a la bordure de l'Ocean Iapetus, tel que souligne dans un article complementaire. Une etude petrographique detaillee des arenites quartziques de la Formation de Kamouraska jumelee a une microscopie electronique a balayage des textures de surface des grains suggerent que les sables quartzeux sont d'origine eolienne et qu'ils proviennent d'un desert d'arriere-pays ou, ce qui est moins probable, d'un systeme de dunes de cordon littoral. Le transport du sable arenite-quartz mature sur la plateforme continentale et sa deposition en mer profonde n'ont pas ete accompagnes d'un malaxage important avec du materiel d'autres sources, preservant ainsi les caracteristiques eoliennes heritees. Un analogue moderne pour l'interpretation eolienne des lits d'arenite quartzique de mer profonde est le suivant: d'epais lits de sables eoliens (Pleistocene tardif) sur une plaine abyssale moderne dans l'Atlantique Est, connus en tant que turbidites de sables eoliens, qui ont ete deposes en mer profonde durant les periodes de bas niveau de la mer en periode glaciaire lorsque le transport du sable eolien vers les tetes des canyons a ete aide par une plateforme exposee et raccourcie. De la meme maniere, une periode de bas niveau de la mer a la limite entre le Cambrien et l'Ordovicien aurait facilite l'introduction du sable eolien Kamouraska dans les tetes des canyons sur la pente superieure d'ou des courants de turbidite et des ecoulements de densite associes etaient declenches. Une correlation entre la Formation de Kamouraska et les arenites quartziques de la Formation Cairnside du Quebec (Formation Keeseville du Nord de l'Etat de New York, Formation Nepean de l'Ontario) relie les depots de mer profonde a des reliques d'un systeme de dunes d'arriere-pays. [Traduit par le Redaction], Introduction The Cambro-Ordovician Kamouraska Formation in the Quebec Appalachians has been interpreted in a companion paper by Malhame and Hesse (2011) as a deep-water clastic succession consisting of sedimentary gravity [...]
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- 2015
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23. Chemostratigraphy as a tool for sequence stratigraphy in the Devonian Hare Indian Formation in the Mackenzie Mountains and Central Mackenzie Valley, Northwest Territories, Canada
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Harris, Brette S., LaGrange, Maya T., Biddle, Sara K., Playter, Tiffany L., Fiess, Kathryn M., and Gingras, Murray K.
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Marine sediments -- Composition ,Rock formations -- Environmental aspects ,Geology, Stratigraphic -- Analysis ,Formations (Geology) -- Environmental aspects ,Argillaceous rocks -- Environmental aspects ,Earth sciences - Abstract
The Hare Indian Formation (HIF) is a late Eifelian to Givetian organic-rich mudstone constituting the lower portion of the Horn River Group (HRG), which has been minimally scrutinized in the literature. This paper proposes depositional environments and a sequence stratigraphic framework for the HIF. Using composition data collected via energy-dispersive X-ray fluorescence, geochemical proxies inform detrital input, silica source, and paleoredox conditions. Cross-plots and chemostratigraphic profiles of detritally sourced Al, Ti, and K and redox-sensitive Mo and V inform depositional and stratigraphic constraints. Silica proportions vary, indicating that sediment was derived from detrital and biogenic sources. Al, Ti, and K distributions increase upwards, showing increased continentally sourced minerals. Redox-sensitive metals are highest in the Bluefish Member (BM), suggesting intermittent euxinia. Based on the presence of continental and pelagic sediments, the sedimentary environment is interpreted as proximal- to mid-shelf. These proxies guide systems tract interpretations. Si and redox-sensitive metal concentrations peak higher in the BM, accompanied by lowered concentrations of Al, Ti, and K, suggesting a maximum flooding surface. At the top of the Prohibition and Bell Creek members, redox-sensitive enrichments are lower with higher concentrations of Al, Ti, and K, suggesting a maximum regressive surface. Transgression occurred during the initial deposition of the BM, followed by regression for the remainder of the HIF. The sedimentology of the HIF can be difficult to decipher; the use of chemostratigraphy supports its geological history (including sedimentation trends and a local record of relative sea level) using methods that may be applied to other finegrained successions. Key words: chemostratigraphy, Hare Indian Formation, Horn River Group, Devonian, Givetian, mudstone, fine-grained, sequence stratigraphy, geochemistry, Northwest Territories, Central Mackenzie Valley, Mackenzie Mountains, XRF, X-ray fluorescence. La Formation de Hare Indian (FHI) est un mudstone tardi-eifelien a givetien riche en matiere organique constituant la partie inferieure du Groupe de Horn River (GHR), qui a fait l'objet de peu d' etudes publiees. Le present article propose des milieux de depot et un cadre de stratigraphie sequentielle pour la FHI. A la lumiere de donnees de composition obtenues par fluorescence X a dispersion d' energie, des variables substitutives geochimiques apportent des precisions sur les apports detritiques, les sources de silice et les conditions d'oxydoreduction passees. Des graphiques de correlation et des profils chimiostratigraphiques de l'Al, du Ti et du K de source detritique et du Mo et du V, qui sont sensibles aux conditions d'oxydoreduction, mettent en lumiere des contraintes stratigraphiques et de sedimentation. Les proportions de silice varient, indiquant que les sediments proviennent de sources detritiques et biogenes. Les concentrations d'Al, de Ti et de K augmentent vers le haut, indiquant une augmentation de mineraux de source continentale. Les proportions des metaux sensibles a l'oxydoreduction sont les plus grandes dans le membre de Bluefish (MB), laissant croire a un euxinisme intermittent. Etant donne la presence de sediments continentaux et pelagiques, un milieu sedimentaire de plateforme proximale a mediale est interprete. Ces variables substitutives guident l'interpretation des corteges de depot. Les concentrations de Si et de metaux sensibles a l'oxydoreduction atteignent un maximum plus haut dans le MB, accompagne de concentrations moindres d'Al, de Ti et de K, ce qui indiquerait une surface d'inondation maximum. Au sommet des membres de Prohibition et de Bell Creek, les enrichissements de metaux sensibles a l'oxydoreduction sont plus faibles et les concentrations d'Al, de Ti et de K, plus grandes, ce qui indiquerait une surface de regression maximum. Une transgression s'est produite durant le depot initial du MB, suivie d'une regression pour le reste de la FHI. La sedimentologie de la FHI peut etre difficile a etablir; l'utilisation de la chimiostratigraphie appuie son histoire geologique (y compris les tendances de sedimentation et un registre local du niveau relatif de la mer) en faisant appel a des methodes qui pourraient etre appliquees a d'autres successions a grains fins. [Traduit par la Redaction] Mots-cles : chimiostratigraphie, Formation de Hare Indian, Groupe de Horn River, Devonien, Givetien, mudstone, a grains fins, stratigraphie sequentielle, geochimie, Territoires du Nord-Ouest, vallee centrale du fleuve Mackenzie, monts Mackenzie, fluorescence X., Introduction Unconventional reservoirs have become increasingly prevalent in the energy industry and, as such, organic-rich mudstones have become common targets of exploration and production in basins across North America. This [...]
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- 2022
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24. A high-resolution, continuous δ13C record spanning the Ordovician-Silurian boundary on Anticosti Island, eastern Canada1.
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Mauviel, Alain, Desrochers, André, and Jin, Jisuo
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CHEMOSTRATIGRAPHY ,GEOCHEMISTRY ,STRATIGRAPHIC geology ,ANTICOSTI Island aster ,EARTH sciences - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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- 2016
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25. Two braincases of Daspletosaurus (Theropoda: Tyrannosauridae): anatomy and comparison
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Carabajal, Ariana Paulina, Currie, Philip J., Dudgeon, Thomas W., Larsson, Hans C.E., and Miyashita, Tetsuto
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Theropoda -- Natural history ,Skull -- Natural history ,Earth sciences - Abstract
For sheer complexity, braincases are generally considered anatomically conservative. However, recent research on the braincases of tyrannosaurids have revealed extensive morphological variations. This line of inquiry has its root in Dale Russell's review of tyrannosaurids in which he established Daspletosaurus torosus--a large tyrannosaurine from the Campanian of southern Alberta. In the wake of systematic revisions to tyrannosaurines previously assigned to Daspletosaurus, one potentially distinct species remains undescribed. This paper describes and compares a braincase referable to this species with that of the holotype for Daspletosaurus torosus using computerized-tomography-based reconstructions. The two braincases have numerous differences externally and internally. The specimen of Daspletosaurus sp. has a bottlenecked olfactory tract, short and vertical lagena, and a developed ascending column of the anterior tympanic recess. The holotype of Daspletosaurus torosus has many unusual traits, including an anteriorly positioned trochlear root, elongate common carotid canal, distinct chamber of the basisphenoid recess, asymmetry in the internal basipterygoid aperture, and laterally reduced but medially expanded subcondylar recess. This comparison also identified characters that potentially unite the two species of Daspletosaurus, including deep midbrain flexures in the endocasts. However, many character variations in the braincases are known in other tyrannosaurids to correlate with body size and maturity, or represent individual variations. Therefore, taxonomic and phylogenetic signals can be isolated from background variations in a more comprehensive approach by using additional specimens. New information on the two braincases of Daspletosaurus is consistent with the emerging view of tyrannosaurid braincases as highly variable, ontogenetically dynamic character complexes. Key words: endocast, inner ear, pneumaticity, Late Cretaceous, Campanian, Alberta, Laramidia. Du seul point de vue de la complexite, l'anatomie des boites craniennes est generalement consideree comme etant conservative. Des recherches recentes sur les boites craniennes de tyrannosaurides ont toutefois revele une grande variabilite morpho-logique. Cette avenue d'etude prend sa source dans la synthese sur les tyrannosaurides de Dale Russell, dans laquelle l'auteur etablit Daspletosaurus torosus, un grand tyrannosaurine du Campanien du sud de l'Alberta. A la suite de revisions systematiques de tyrannosaurines precedemment affectes a Daspletosaurus, une espece potentiellement distincte demeure non decrite. Le present article decrit une boite cranienne pouvant etre referee a cette espece et la compare a celle de l'holotype de Daspletosaurus torosus en utilisant des reconstitutions basees sur la tomographie par ordinateur. De nombreuses differences tant externes qu'internes existent entre les deux boites craniennes. Le specimen de Daspletosaurus sp. presente des voies olfactives en goulot d'etranglement, une lagena courte et verticale, ainsi qu'une colonne ascendante developpee du recessus tympanique anterieur. L'holotype de Daspletosaurus torosus presente de nombreux caracteres inhabituels, dont une racine trochleaire positionnee anterieurement, un canal carotidien commun allonge, une cavite distincte du recessus basispheno'ide, une asymetrie de l'ouverture basip-terygo'ide interne et un recessus subcondylaire reduit lateralement, mais agrandi medialement. Cette comparaison fait egalement ressortir des caracteres qui pourraient unir les deux especes de Daspletosaurus, dont de profondes flexures mesen-cephales dans les endocastes. Il est toutefois etabli que de nombreuses variations de caracteres dans les boites craniennes chez d'autres tyrannosaurides sont correlees a la taille du corps et a la maturite ou representent des variations individuelles. Des signaux taxonomiques et phylogenetiques peuvent done etre isoles des variations de fond par une approche plus exhaustive en faisant appel a d'autres specimens. Les nouveaux renseignements sur les deux boites craniennes de Daspletosaurus concordent avec l'opinion emergente selon laquelle les boites craniennes de tyrannosaurides constituent des complexes de caracteres tres variables et dynamiques sur le plan ontogenique. [Traduit par la Redaction] Mots-cles: endocaste, oreille interne, pneumaticite, Cretace tardif, Campanien, Alberta, Laramidie., Introduction The description of Daspletosaurus torosus Russell, 1970 ushered in the modern era of research on North American tyrannosaur-ids. To Dale A. Russell, erecting Daspletosaurus was not a simple taxonomic [...]
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- 2021
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26. Geological correlation between northern Cyprus and southern Anatolia
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Yilmaz, Yücel
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Asia Minor -- Natural history ,Cyprus -- Natural history ,Stratigraphic correlation -- Analysis ,Tectonics (Geology) -- Comparative analysis ,Earth sciences - Abstract
The island of Cyprus constitutes a fragment of southern Anatolia separated from the mainland by left-oblique transtension in late Cenozoic time. However, a geological framework of offset features of south-central Anatolia, for comparison of Cyprus with a source region within and west of the southeastern Anatolian suture zone, has not yet been developed. In this paper, I enumerate, describe, and compare a full suite of potentially correlative spatial and temporal elements exposed in both regions. Northern Cyprus and south-central Anatolia have identical tectonostratigraphic units. At the base of both belts, crop out ophiolitic mélange--accretionary complex generated during the northward subduction of the NeoTethyan Oceanic lithosphere from the Late Cretaceous until the end of middle Eocene. The nappes of the Taurus carbonate platform were thrust above this internally chaotic unit during late Eocene. They began to move as a coherent nappe pile from that time onward. An asymmetrical flysch basin was formed in front of this southward-moving nappe pile during the early Miocene. The nappes were then thrust over the flysch basin fill and caused its tight folding. Cyprus separated from Anatolia in the Pleistocene--Holocene when transtensional oblique faults with dip-slip components caused the development of the Adana and Iskenderun basins and the separation of Cyprus from Anatolia. Keywords: geology, Cyprus, southeastern Anatolia, correlation, tectonics. L'île de Chypre constitue un fragment de lAnatolie méridionale séparé du continent par transtension senestre-oblique au Cénozoïque tardif. Un cadre géologique d'éléments déportés du centre sud de lAnatolie, pour les fins de comparaison de Chypre avec une région source au sein et à l'ouest de la zone de suture du sud-est de lAnatolie, n'a pas encore été élaboré. Dans le présent article, j'énumère, décris et compare un ensemble complet d'éléments spatiaux et temporels potentiellement corrélés exposés dans les deux régions. Le nord de Chypre et le centre-sud de lAnatolie présentent des unités tectonostratigraphiques identiques. À la base des deux ceintures affleure un complexe accrétionnaire-de mélange ophiolitique produit durant la subduction vers le nord de la lithosphère océanique néotéthysienne du Crétacé tardif jusqu'à la fin de l'Eocène moyen. Les nappes de la plateforme carbonatée de Taurus ont été charriées sur cette unité intérieurement chaotique durant l'Eocène tardif. Elles ont par la suite commencé à se déplacer en tant que pile de nappes cohérente. Un bassin de flysch asymétrique s'est formé devant cette pile de nappes se déplaçant vers le sud, durant le Miocène précoce. Les nappes ont ensuite été charriées sur les dépôts de remplissage du bassin de flysch, causant leur plissement serré. Chypre s'est séparée de lAnatolie au Pléistocène--Holocène quand des failles obliques de transtension avec des composants à rejet-pendage ont entraîné la formation des bassins d'Adana et d'Iskenderun et la séparation de Chypre de lAnatolie. [Traduit par la Rédaction] Mots-clés : géologie, Chypre, sud-est de lAnatolie, corrélation, tectonique., Introduction Over the last century and a half, several studies have focused on general or specific geological aspects of Cyprus (Gaudry 1862; Russell 1882; Reed 1929; Henson et al. 1949; [...]
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- 2021
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27. Lower Cambrian (Series 2) small shelly fossils from along Nares Strait (Nunavut and Greenland; Laurentia)
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Peel, John S. and Skovsted, Christian B.
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Fossils -- Natural history ,Earth sciences - Abstract
Three small assemblages of lower Cambrian (Cambrian Series 2, Stage 4) small shelly fossils are described from Laurentian strata astride Nares Strait. The fauna from the Humboldt Formation of Daugaard-Jensen Land, North Greenland, is derived from inner shelf sediments deposited on the stable craton of the Inglefield Land High. Fossils from Judge Daly Promontory, eastern Ellesmere Island, Nunavut, occur in strata of the Cambrian Ellesmere Group (Kane Basin Formation) that have been structurally juxtaposed against older strata; they were originally assigned to the Kennedy Channel Formation, which is now considered to be of Neoproterozoic age. A similar fauna from offshore environments of the Aftenstjerneso Formation in northern Nyeboe Land, North Greenland, reflects the regional structural and sedimentological continuity with the Canadian Cambrian succession. Pojetaia robsonae sp.nov.is described from Judge Daly Promontory. Key words: Lower Cambrian, small shelly fossils, Ellesmere Island, North Greenland, Laurentia. Trois petits assemblages de petits fossiles a coquille du Cambrien inferieur (serie 2, etage 4 du Cambrien) provenant de strates laurentiennes qui enjambent le detroit de Nares sont decrits. L'assemblage provenant de la Formation de Humboldt de la region de Daugaard-Jensen (Groenland septentrional) est derive de sediments de plateforme interne deposes sur le craton stable des hauteursde la region d'Inglefield. Les fossiles provenant du promontoire Judge Daly de l'est de l'ile d'Ellesmere (Nunavut) sont presents dans des strates du Groupe cambrien d'Ellesmere (Formation du basin Kane) juxtaposees structuralement a des strates plus anciennes; elles avaient a l'origine ete affectees a la Formation du passage Kennedy, aujourd'hui consideree etre d'age neoproterozoique. Un assemblage semblable de milieux extracotiers de la Formation d'Aftenstjerneso, dans le nord de la peninsule Nyeboe (Groenland septentrional), temoigne de la continuite structurale et sedimentologique regionale avec la sequence cambrienne canadienne. Pojetaia robsonae sp. nov., provenant du promontoire Judge Daly, est decrit. Mots-cles: Cambrien inferieur, petits fossiles a coquille, ile d'Ellesmere, Groenland septentrional, Laurentie., Introduction This paper describes and compares three assemblages of lower Cambrian (Cambrian Series 2) fossils from localities astride Nares Strait, the narrow seaway separating eastern Ellesmere Island, Nunavut, from the [...]
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- 2021
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28. Potential-field modelling of the prospective Chibougamau area (northeastern Abitibi subprovince, Quebec, Canada) using geological, geophysical, and petrophysical constraints
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Maleki, Amir, Smith, Richard, Eshaghi, Esmaeil, Mathieu, Lucie, Snyder, David, and Naghizadeh, Mostafa
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Prospecting -- Geophysical methods ,Geology, Structural -- Analysis ,Cratons -- Environmental aspects ,Earth sciences - Abstract
This paper focusses on obtaining a better understanding of the subsurface geology of the Chibougamau area, in the northeast of the Abitibi greenstone belt (Superior craton), using geophysical data collected along a 128 km long traverse with a rough southwest--northeast orientation. We have constructed two-dimensional (2D) models of the study area that are consistent with newly collected gravity data and high-resolution magnetic data sets. The initial models were constrained at depth by an interpretation of a new seismic section and at surface by the bedrock geology and known geometry of lithological units. The attributes of the model were constrained using petrophysical measurements so that the final model is compatible with all available geological and geophysical data. The potential-field data modelling resolved the geometry of plutons and magnetic bodies that are transparent on seismic sections. The new model is consistent with the known structural geology, such as open folding, and provides an improvement in estimating the size, shape, and depth of the Barlow and Chibougamau plutons. The Chibougamau pluton is known to be associated with Cu--Au magmatic-hydrothermal mineralisation and, as the volume and geometry of intrusive bodies is paramount to the exploration of such mineralisation, the modelling presented here provides a scientific foundation to exploration models focused on such mineralisation. Key words: geophysics, potential-field modelling, 2.5D modelling, geological modelling, geological, seismic and petrophysical constraints, gravity and magnetic. L'article est axe sur l'etablissement d'une meilleure comprehension de la geologie du sous-sol de la region de Chibougamau, dans le nord-est de la ceinture de roches vertes de l'Abitibi (craton du Superieur), a la lumiere de donnees geophysiques recueillies le long d'une traverse de 128 km d'orientation approximativement sud-ouest--nord-est. Nous avons construit des modeles bidimensionnels (2D) de la region a l'etude qui concordent avec des donnees gravimetriques et des ensembles de donnees magnetiques de haute resolution nouvellement acquis. Les modeles initiaux ont ete delimites en profondeur par l'interpretation d'une nouvelle coupe sismique et en surface par la geologie du substrat rocheux et la geometrie connue des unites lithologiques. Les attributs du modele ont ete etablis en utilisant des mesures petrophysiques, le modele final etant ainsi compatible avec toutes les donnees geologiques et geophysiques disponibles. La modelisation des donnees de champ de potentiel a permis de cerner la geometrie de plutons et de corps magnetiques qui sont transparents sur les coupes sismiques. Le nouveau modele s'accorde avec les elements connus de la geologie structurale, comme un plissement ouvert, et ameliore l'estimation de la taille, de la forme et de la profondeur des plutons de Barlow et de Chibougamau. Il est etabli que ce dernier est associe a une mineralisation magmatique-hydrothermale a Cu--Au et, comme le volume et la geometrie des corps intrusifs revetent une importance capitale dans l'exploration pour ce type de mineralisation, la modelisation presentee constitue un fondement scientifique pour les modeles d'exploration axes sur ce type de mineralisation. [Traduit par la Redaction] Mots-cles : geophysique, modelisation du champ de potentiel, modelisation en 2,5D, modelisation geologique, contraintes geologiques, sismiques et petrophysiques, gravite et magnetisme., Introduction The Metal Earth project aims to better understand the differences between greenstone belts in the Abitibi and Wabigoon belts of the Superior craton of Canada that are well endowed [...]
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- 2021
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29. Stratigraphy and sedimentology of the Pennsylvanian Grande Anse Formation, Cumberland Basin, eastern Canada: its relationship to salt tectonics and coeval strata of the Joggins World Heritage Site
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Bahr, Fadel and Keighley, Dave
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North America -- Economic aspects ,Lithofacies -- Environmental aspects ,Sedimentology -- Research ,Geology, Stratigraphic -- Research ,Geological research ,Tectonics (Geology) -- Research ,Sedimentary basins -- Environmental aspects ,Earth sciences - Abstract
The Cumberland Basin is one of several sedimentary basins composing the late Paleozoic Maritimes Basin complex of eastern Canada. Pennsylvanian salt tectonics in the Cumberland Basin caused two salt mini-basins to evolve on either side of the Minudie Anticline, a salt wall. South of the wall (Athol Syncline), along the Joggins World Heritage shoreline, an--3000 m succession of strata (Little River, Joggins, Springhill Mines, and Ragged Reef formations) accumulated conformably on the Boss Point Formation. North of the wall (Black Point sub-basin), the biostratigraphically equivalent, but mostly unstudied,--600 m thick succession of Grande Anse Formation lies in angular unconformity on folded and faulted Boss Point and basal Little River formations. Grande Anse Formation sedimentology indicates four lithofacies associations: floodplain (LA1), braided channel (LA2), sheet flood (LA3), and debris flow deposits (LA4). One possible model has the Black Point sub-basin with its own hydrological system, completely separated from the Athol Syncline. A low subsidence rate combined with the low sedimentation rate produced the--600 m thick sand- and mud-prone succession that was contemporaneous with the--3 km succession to the south. The second model proposes that north of the salt wall was exposed to erosion during accumulation of Joggins and Springhill Mines formation strata to the south. Subsequently, the sediment of the lithologically similar Ragged Reef and Grande Anse formations either (i) onlapped to the north, unconformably on the folded Boss Point; or (ii) unconformably-disconformably on the underlying strata after a period of time indistinguishable in the biostratigraphic record. Key words: Grande Anse Formation, Joggins, salt tectonics, stratigraphy, sedimentology. Le bassin de Cumberland estun des bassins sedimentaires qui composent le complexe tardi-paleozoique de bassins des Maritimes, dans l'est du Canada. Une tectonique salifere au Pennsylvanien dans le bassin de Cumberland a entraine la formation de deux mini-bassins de sel de part et d'autre de l'anticlinal de Minudie, un mur de sel. Au sud du mur (synclinal dAthol), le long du littoral du Patrimoine mondial de Joggins, une sequence de quelque 3000 m de strates (Formations de Little River, Joggins, Springhill Mines et Ragged Reef) s'est accumulee de maniere concordante sur la Formation de Boss Point. Au nord du mur (sous-bassin de Black Point), la sequence equivalente du point de vue biostratigraphique, mais generalement non etudiee, de --600 m de la Formation de Grande Anse repose en discordance angulaire sur des roches plissees et faillees de la Formation de Boss Point et de la base de la Formation de Little River. La sedimentologie de la Formation de Grande Anse indique quatre associations de lithofacies, a savoir, des depots de plaines inondables (LA1), de chenaux anastomoses (LA2), d'inondations en nappe (LA3) et de coulees de debris (LA4). Dans un modele possible, le sous-bassin de Black Point et son reseau hydrologique sont completement separes du synclinal dAthol. Une faible vitesse de subsidence combinee a un faible taux de sedimentation a produit la sequence de--600 m riche en sable et en boue contemporaine de la sequence de--3 km situee au sud. Le deuxieme modele propose que le nord du mur de sel ait ete expose a l'erosion durant l'accumulation de strates des Formations de Joggins et Springhill Mines au sud. Par la suite, les sediments des Formations de Ragged Reef et de Grande Anse, semblables sur le plan lithologique, ont soit (i) ete deposes en discordance sur les roches plissees de la Formation de Boss Point, qu'elles ont debordees vers le nord ou (ii) ont ete deposes en discordance sur les strates sous-jacentes apres un intervalle de temps indistinguable dans le profil biostratigraphie. [Traduit par la Redaction] Mots-cles: Formation de Grande Anse, Joggins, tectonique salifere, stratigraphie, sedimentologie., Introduction This paper provides the first detailed study of the Grande Anse Formation through the logging of its three main coastal outcrop localities on both sides of the New Brunswick-Nova [...]
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- 2021
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30. Filling process and filling characteristic analysis of Paleogene Baxian sag in Bohai Bay basin, China
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Zhang, Zili, Zhu, Xiaomin, Zhang, Ruifeng, Fu, Sheng, and Zhang, Jing
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Faults (Geology) -- Natural history -- Properties ,Morphotectonics -- Analysis ,Sedimentary basins -- Natural history -- Structure -- Discovery and exploration ,Earth sciences - Abstract
In addition to core, logging, and other previous research results, this paper determines the fault development and tectonic evolution process of the Baxian sag with the Paleogene rift stage based on 3D seismic data. The Paleogene tectonic evolution of the sag can be divided into three episodes and six evolution stages, and three types of faults are identified: intensely active normal, active normal, and weakly active normal. One first-order sequence, three second-order sequences, and fourteen third-order sequences of the Paleogene Baxian sag were created, and fifteen sequence boundaries were recognised. According to the rifting background and sedimentary facies development characteristics of each episode, five combination types of the depositional system associations were identified, including alluvial fan-fluvial and braided-delta-lacustrine in an early rifting episode, delta-lacustrine and nearshore subaqueous fan-lacustrine in the middle rifting episode, and fluvial-flood plain in the late rifting episode. Six response models of filling and the evolution process in Paleogene Baxian sag were concluded. The multi-episodes tectonic cycles of faulted lake basins resulted in complex paleogeomorphology and variable provenance supply, forming abundant sequence structure patterns and different filling and evolution processes of faulted lake basins. The stable rifting stage is favourable to form and preserve high-quality source rock, and develop various sedimentary facies and sandbody types, which is a potential area for exploration of a lithologic stratigraphic oil and gas reservoir. Key words: sequence depositional model, basin filling process, depositional system, tectonic evolution, Paleogene, Baxian sag. En plus de descriptions de carottes de forage et d'autres résultats de recherche antérieurs, le présent article établit le processus de développement de failles et d'évolution tectonique de l'affaissement de Baxian combiné au rift paléogène à la lumière de données de sismique 3D. L'évolution tectonique paléogène de l'affaissement peut être subdivisée en trois épisodes et six phases d'évolution, et trois types de failles sont relevés, à savoir : des failles normales très actives, des failles normales actives et des failles normales peu actives. Une séquence de premier ordre, trois séquences de deuxième ordre et quatorze séquences de troisième ordre de l'affaissement paléogène de Baxian ont été créées, et quinze limites de séquences ont été cernées. À la lumière du contexte de rifting et des caractéristiques de développement des faciès sédimentaires de chaque épisode, cinq types de combinaison d'associations de systèmes de dépôt ont été identifiés, soit des types à cône alluvial-fluvial et deltaïque anastomosé-lacustre durant l'épisode de rifting précoce, deltaïque-lacustre et à cône subaquatique littoral-lacustre durant l'épisode de rifting intermédiaire, et fluvial-de plaine alluviale durant l'épisode de rifting tardif. Il en découle six modèles de remplissage et le processus d'évolution de l'affaissement paléogène de Baxian. Les cycles tectoniques à épisodes multiples des bassins lacustres faillés ont produit une paléogéomorphologie complexe et des apports de provenances variées, formant de nombreux motifs de structure de séquence et différents processus de remplissage et d'évolution de bassins lacustres faillés. L'étape du rifting stable a pu favoriser la formation et la préservation de roches sources de qualité et le développement de faciès sédimentaires et de types de dépôts de sable variés, ce qui en fait un secteur à fort potentiel d'exploration pour la présence d'un réservoir lithologique et stratigraphique de pétrole et de gaz. [Traduit par la Rédaction] Mots-clés : modèle de dépôt de séquences, processus de remplissage de bassin, système de dépôt, évolution tectonique, Paléogène, affaissement de Baxian., Introduction The formation and development of sequence stratigraphy in marine basins is mainly controlled by four factors, tectonic movement, sea level change, sediment supply rate, and climate (Galloway 1975; Posamentier [...]
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- 2021
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31. Geochronology, geochemistry, and Hf isotopic compositions of early Permian syenogranite and diabase from the northern Great Xing'an Range, northeastern China: petrogenesis and tectonic implications
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Sun, Yong-gang, Li, Bi-le, Sun, Feng-yue, Ding, Qing-feng, Qian, Ye, Li, Liang, Xu, Qing-lin, and Li, Yu-jin
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Geodynamics -- Research ,Geochronology -- Research ,Petrogenesis -- Research ,Geological research ,Tectonics (Geology) -- Research ,Magmatism -- Research ,Earth sciences - Abstract
Geodynamic evolution in the late Paleozoic is significant for understanding the final amalgamation of the Central Asian Orogenic Belt (CAOB). No consensus has yet been reached regarding the late Paleozoic geodynamic evolution of the northern Great Xing'an Range (GXR) in northeastern China, the eastern CAOB. Furthermore, late Paleozoic syenogranitediabase dyke association is present in the Xiaokele area in northern GXR. It provides an important opportunity to understand the nature of magmatism and the geodynamic evolution during this period. This paper presents new zircon U-Pb ages, zircon Hf isotopic compositions, and geochemical data of whole rocks for Xiaokele syenogranite and diabase. Zircon U-Pb dating suggests that the Xiaokele syenogranite (292.5 [+ or -] 0.9 Ma) and diabase (298.3 [+ or -] 1.5 Ma) were emplaced during the early Permian. The Xiaokele syenogranites have high Si[O.sub.2] contents, low MgO contents, and enriched zircon [[epsilon].sub.Hf](t) values, suggesting that their primary magma was generated by the partial melting of the juvenile crustal material. The Xiaokele diabases have low Si[O.sub.2] contents, high MgO contents, are enriched in large-ion lithophile elements, depleted in high-field-strength elements, and exhibit enriched zircon [[epsilon].sub.Hf](t) values. They derived from a lithospheric mantle source that had previously been metasomatized by slab-derived fluids. Combined with previous research results, we believe that the continent-continent collision between the Xing'an and Songliao blocks occurred during the late early Carboniferous - early late Carboniferous (330-310 Ma), and the two blocks were transformed into a post-collisional extensional setting during the latest Carboniferous - early Permian. Key words: early Permian, syenogranite, diabase, post-collisional extensional setting, Xiaokele, northern Great Xing'an Range. L'evolution geodynamique au Paleozoique tardif est importante pour la comprehension de l'amalgamation finale de la ceinture orogenique d'Asie centrale (COAC). Aucun consensus n'a encore ete etabli quant a l'evolution geodynamique au Paleozoique tardif du Grand Xing'an (GX) septentrional de l'est de la COAC dans le nord-est de la Chine. En outre, une association d'age paleozoique tardif de syenogranite et de dykes de diabase est presente dans la region de Xiaokele du GX septentrional, qui offre une bonne occasion de mieux comprendre la nature du magmatisme et de l'evolution geodynamique durant cette periode. L'article presente de nouveaux ages U-Pb sur zircons, des donnees sur la composition des isotopes de Hf des zircons et des donnees geochimiques sur roche totale pour le syenogranite et la diabase de Xiaokele. La datation U-Pb sur zircons indiquerait que le syenogranite (292,5 [+ or -] 0,9 Ma) et la diabase (298,3 [+ or -] 1,5 Ma) de Xiaokele ont ete mis en place durant le Permien precoce. Les syenogranites de Xiaokele ont des teneurs elevees en Si[O.sub.2] et faibles MgO et presentent des valeurs enrichies de [[epsilon].sub.Hf](t) des zircons, ce qui indiquerait que leur magma primaire est un produit de la fusion partielle de materiau crustal juvenile. Les diabases de Xiaokele ont des teneurs en Si[O.sub.2] faibles et en MgO elevees et sont enrichies en elements lithophiles a grand rayon ionique, appauvries en elements a forte liaison atomique et presentent des valeurs enrichies de [[epsilon].sub.Hf](t) des zircons. Elles proviennent d'une source dans le manteau lithospherique ayant prealablement subi un metasomatisme cause par des fluides issus d'une plaque subductee. A la lumiere de ces resultats et de resultats de travaux anterieurs, nous croyons que la collision continent-continent des blocs de Xing'an et de Songliao s'est produite durant l'intervalle du Carbonifere precoce tardif au Carbonifere tardif precoce (330 Ma-310 Ma) et que les deux blocs se sont transformes en un milieu d'extension post-collision durant l'intervalle de la fin du Carbonifere au Permien precoce. [Traduit par la Redaction] Mots-cles: Permien precoce, syenogranite, diabase, milieu d'extension post-collision, Xiaokele, Grand Xing'an septentrional., Introduction The tectonic evolution of orogenic belts is characterized by changes in the associated magmatic composition (Harris et al. 1986). Post-collisional magmatism, as one of the common characteristics of many [...]
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- 2020
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32. Long-term nivation rates, Cathedral Massif, northwestern British Columbia
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Nyland, Kelsey E. and Nelson, Frederick E.
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British Columbia -- Environmental aspects ,Drone aircraft -- Usage ,Erosion -- Analysis ,Geomorphology -- Research ,Geological research ,Landforms -- Environmental aspects ,Earth sciences - Abstract
Cryoplanation terraces (CTs) are large (3000-800 000 [m.sup.2]) erosional landforms found in upland periglacial environments. Two hypotheses for the formation of CTs are supported in contemporary literature: (1) CT formation is controlled primarily by geologic structure; and (2) CTs are climatically controlled through nivation, a suite of erosional processes associated with late-lying snowbanks. A persistent question in periglacial geomorphology is whether nivation can produce CT-scale landforms. This paper examines the unusual deglaciation history of 'Frost Ridge' on the Cathedral Massif, northwestern British Columbia, to estimate long-term denudation attributable to nivation processes active since the last glacial maximum. Frost Ridge forms one flank of an east--west-oriented glacial valley. During deglaciation, marginal drainage created V-shaped erosional notches on both valley walls. Minimization of solar radiation on the steep north-facing wall (Frost Ridge) allowed snowbanks to accumulate and persist in the marginal drainage features and nivation processes to erode the slope. Today, several large nivation hollows (incipient CTs) are present near the summit of Frost Ridge, while the V-shaped marginal drainage features are preserved at lower elevations and on the opposite, south-facing valley wall. A high-resolution survey using an unmanned aerial vehicle (UAV) allowed volumes of marginal drainage and incipient terrace features to be compared. Based on this volumetric comparison, denudation rates are estimated to range from 4.2 to 125.8 mm/kyr, which are comparable with relatively short-term nivation rates reported from Antarctica and mid-latitude alpine periglacial areas. Key words: periglacial geomorphology, nivation, cryoplanation, UAV Survey, volumetric erosion estimation. Les terrasses de cryoplanation (TC) sont de vastes (3000-800 000 [m.sup.2]) reliefs d'érosion observés en milieux périglaciaires secs. La documentation contemporaine appuie les deux hypothèses suivantes concernant la formation des TC : (1) elle est principalement contrôlée par la structure géologique et (2) le climat, par l'entremise de la nivation, une série de processus d'érosion associés aux amas de neige persistants, contrôle les TC. Une question persistante en géomorphologie périglaciaire est à savoir si la nivation peut produire des reliefs de l'ampleur des TC. Le présent article se penche sur l'historique inhabituel de déglaciation de << Frost Ridge >>, dans le massif Cathedral du nord-ouest de la Colombie-Britannique, afin d'estimer la dénudation à long terme attribuable aux processus de nivation à l'oeuvre depuis le dernier maximum glaciaire. Frost Ridge forme un des flancs d'une vallée glaciaire d'orientation est--ouest. Durant la déglaciation, le drainage marginal a formé des encoches d'érosion en V dans les deux parois de la vallée. La minimisation du rayonnement solaire sur le mur abrupt donnant vers le nord (Frost Ridge) a permis l'accumulation d'amas de neige et leur persistance dans des éléments produits par le drainage marginal, ainsi que l'érosion de la pente par des processus de nivation. Aujourd'hui, plusieurs grandes niches de nivation (TC naissantes) sont présentes près du sommet de Frost Ridge, alors que les éléments en V issus du drainage marginal sont préservés à plus basses altitudes et sur la paroi opposée de la vallée, donnant vers le sud. Un levé de haute résolution réalisé à l'aide d'un aéronef sans pilote (ASP) a permis une comparaison des volumes des éléments de drainage marginal et des terrasses naissantes. Les taux de dénudation estimésà lalumière decette comparaison volumétrique vont de4,2 à 125,8 mm/kyr, ce qui est comparableà des taux de nivation de durée relativement courte documentés en Antarctique et dans des régions périglaciaires alpines de latitudes intermédiaires. [Traduit par la Rédaction] Mots-clés : géomorphologie périglaciaire, nivation, cryoplanation, levé par USP, estimation volumétrique de l'érosion., Introduction Cryoplanation terraces (CTs) are large landforms consisting of alternating steep and shallow slope segments and repeating sedimentological patterns (Demek 1969; Reger 1975). From a distance, these landforms resemble immense [...]
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- 2020
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33. Origin and paleoenvironmental reconstruction of phosphorus-bearing sandstones of the Cambrian Xinji Formation, southwestern margin of the Ordos Basin, China
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Liang, Jiwei, Tao, Wenxing, and Ma, Xiaojun
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X-rays -- Diffraction ,Rare earth metals -- Discovery and exploration ,Calcite crystals -- Discovery and exploration ,Carbonates -- Discovery and exploration ,Rocks, Sedimentary -- Discovery and exploration ,Continental margins -- Discovery and exploration ,Clay -- Discovery and exploration ,Basalt -- Discovery and exploration ,Earth sciences - Abstract
Increasing exploration interest in oil and gas hosted by early Cambrian strata has focused research efforts on early Cambrian sandstones. The origin of phosphorus and the paleoenvironment of phosphorus-bearing sandstones from the Xinji Formation are discussed in this paper. X-ray diffraction, optical microscopy, grain size analysis, total organic carbon, and the concentrations of major, trace, and rare earth elements (REEs) are analyzed in this work. The sandstones are mostly sublitharenite with calcareous cement. The content of the sandstone samples is quartz (39.8%--73.9%), with illite (7.9%--27.6%) and calcite (4.5%--29%). The mineral particles of sandstone samples are mainly well sorted with a fine particle size, suggesting strong paleohydrodynamic force. The value of Si[O.sub.2] is 37.69%--78.19%, followed by [Al.sub.2][O.sub.3] (6.11%--13.67%). Compared with upper continental crust, the boron in the sandstone samples is relatively enriched, whereas Sc, Sr, and Ba are relatively depleted. The [SIGMA]REE content is 124.46-323.99 ppm. Phosphorus is of biogenic origin and enriched by upwelling current. The source of the Xinji Formation sandstone samples was mainly a mixture of sedimentary rock, granite, and alkali basalt, with the provenance of terrestrial clastic materials. The sandstone was deposited under oxic conditions and a warm and humid paleoclimate with saline to brackish features on a passive continental margin. Phosphorus occurring in sandstones is sensitive to paleoclimate and can be used as an indicator to judge paleoclimate, as it is more enriched in warm and humid weather. Key words: geochemistry, paleoenvironment, phosphorus-bearing sandstones, Xinji Formation, Ordos Basin. L'interet croissant pour l'exploration petroliere et gaziere dans des strates d'age cambrien precoce a eu pour consequence d'axer des efforts de recherche sur des gres de cet age. L'origine du phosphore et le paleomilieu de gres contenant du phosphore de la Formation de Xinji sont examines. La diffraction X, la microscopie optique, l'analyse granulometrique, ainsi que l'analyse du carbone organique total et des concentrations d'elements majeurs et en traces et des terres rares ont ete effectuees. Les gres sont pour la plupart des sublitharenites a ciment calcareux. Les teneurs des echantillons de gres en quartz sont de 39,8-73,9 %, avec de l'illite (7,9-27,6 %) et de la calcite (4,5-29 %). Les grains de mineraux sont principalement bien classes et de granulometrie fine, ce qui indiquerait de grandes forces paleohydrodynamiques. Les teneurs en Si[O.sub.2] sont de 37,69-78,19 %, suivies de l'[Al.sub.2][O.sub.3] (6,11-13,67 %). Par rapport a la croute continentale superieure, le bore est relativement enrichi dans les echantillons de gres, alors que le Sc, le Sr et le Ba sont appauvris. Les concentrations en terres rares totales ([SIGMA]REE) sont de 124,46 ppm--323,99 ppm. Le phosphore est d'origine biogenique et enrichi par des courants de remontee. La source des gres etudies de la Formation de Xinji etait principalement constituee d'un melange de roche sedimentaire, de granite et de basalte alcalin, la provenance des materiaux clastiques etant terrestre. Les gres se sont deposes dans des conditions oxydantes et chaudes, dans un paleoclimat humide et dans un milieu de marge continentale passive caracterise par des eaux salines a saumatres. Le phosphore dans les gres est sensible au paleoclimat et peut etre utilise comme indicateur de ce dernier, son enrichissement refletant des conditions meteorologiques chaudes et humides. [Traduit par la Redaction] Mots-cles: geochimie, paleomilieu, gres contenant du phosphore, Formation de Xinji, bassin d'Ordos., Introduction The Ordos Basin is the largest petroliferous basin in China (Zhang 2000; Hou et al. 2003; Xi et al. 2006; Liu et al. 2009; Shi et al. 2009). Current [...]
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- 2020
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34. Petrogenesis and tectonic implications of the Late Triassic Nangou granodiorite porphyry in the Eastern Kunlun Orogenic Belt, northern Tibetan Plateau
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Yan, Jiaming, Sun, Fengyue, Qian, Ye, Tian, Nan, Yan, Zhengping, Zhang, Yongsheng, and Yang, Ximing
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Granite ,Rare earth metals ,Petrogenesis ,Porphyry ,Tectonics (Geology) ,Earth -- Crust ,Magmatism ,Earth sciences - Abstract
Triassic granitic magmatism is widespread in the Eastern Kunlun Orogenic Belt (EKOB), northern Tibetan Plateau. Some of the granitoids are characterized by high Sr and low Y contents, and consequently high Sr/Y ratios. These high Sr/Y-ratio granitoids are often interpreted as adakitic rocks, originating from the thickened continental lower crust. However, studies have shown that granitoids with high Sr/Y ratios may have formed via other geological processes. This paper reports U-Pb ages, geochemical and Sr-Nd-Hf isotopic data for newly discovered granodiorite porphyries in the Kunlun River area of the Eastern Kunlun Orogenic Belt, and discusses whether the EKOB experienced crustal thickening during the Triassic. The granodiorite porphyries crystallized at 205 Ma. They have some adakitic characteristics with Si[O.sub.2] = 66.96-69.68 wt.%, Sr/Y ratios = 31-43, La/Yb = 26.9-57.9, Y= 8.47-11.3, Yb = 0.75-1.30, and MgO = 0.44-0.99 wt.%. However, the relatively flat heavy rare earth element patterns indicate that garnet was not the main residue in the magma source. In addition, combined with Nd-Hf isotopic data, these results indicate that the timing of the original generation of the crustal sources of the granodiorites should be Mesoproterozoic, with the involvement of older (Paleoproterozoic) components. The granodiorite porphyries were emplaced in a post-collisional environment after the northward subduction of Paleo-Tethyan oceanic lithosphere, and without thickening of the continental crust. Key words: Kunlun River granodiorite porphyries, U-Pb ages, Sr-Nd-Hf isotopes, Paleo-Tethys Ocean, Eastern Kunlun Orogenic Belt (EKOB). Un magmatisme granitique triasique est repandu dans la ceinture orogenique du Kunlun oriental (COKO) du nord du plateau Tibetain. Certains des granitoides sont caracterises par de fortes teneurs en Sr et de faibles teneurs en Y, pour des rapports Sr/Y eleves. Ces granitoides a Sr/Y eleves sont souvent interpretes comme etant des roches adakitiques provenant de la croute continentale epaissie. Des etudes ont toutefois demontre que des granitoides a Sr/Y eleves pourraient s'etre formes par d'autres processus geologiques. Nous faisons etat d'ages U-Pb et de donnees geochimiques et sur les isotopes de Sr-Nd-Hf pour des porphyres de granodiorite nouvellement decouverts dans la region de la riviere Kunlun de la COKO, et abordons la question d'un eventuel epaississement crustal de la COKO durant le Trias. Les porphyres de granodiorite ont cristallise a 205 Ma. Ils presentent certaines caracteristiques adakitiques, a savoir : Si[O.sub.2] = 66,96-69,68 % en poids, Sr/Y = 31-43, La/Yb = 26,9-57,9, Y = 8,47-11,3, Yb = 0,75-1,30, MgO = 0,44-0,99 % en poids. Les spectres de terres rares lourdes relativement plats indiquent toutefois que le grenat n'etait pas le principal residu dans la source du magma. En outre, combines a des donnees sur les isotopes de Nd-Hf, ces resultats indiquent que la production initiale des sources crustales des granodiorites devrait s'etre produite au Mesoproterozoique, et qu'elle a fait intervenir des composants plus vieux (paleoproterozoiques). Les porphyres de granodiorite ont ete mis en place dans un milieu post-collision apres la subduction vers le nord de lithosphere oceanique paleo-tethysienne, sans epaississement de la croute continentale. [Traduit par la Redaction] Mots-cles : porphyres de granodiorite de la riviere Kunlun, ages U-Pb, isotopes de Sr-Nd-Hf, ocean paleo-tethysien, ceinture orogenique du Kunlun oriental (COKO)., Introduction Defant and Drummond (1990) defined adakitic rocks as high-Si[O.sub.2] (>56 wt.%) arc volcanic rocks derived directly from the melts of young ( The EKOB is a large-scale tectonomagmatic belt [...]
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- 2020
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35. Identification of sequence stratigraphy in the Dongying Formation of the Liaoxi low uplift, Bohai Bay Basin, China
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Zhou, Guangzhao, Hu, Zhiming, Duan, Xianggang, and Chang, Jin
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Lithofacies -- Models ,Rock formations -- Models ,Geology, Stratigraphic -- Methods ,Formations (Geology) -- Models ,Uplift (Geology) -- Models ,Tectonics (Geology) -- Models ,Earth sciences - Abstract
A change in sea level (or lake level) causes a change in accommodation space and sediment compensation, which then controls the formation and evolution of sequences. A multidisciplinary approach based on the integration of clay minerals, major and trace elements, paleosalinity, and three-dimensional seismic data were applied to interpret the stratigraphic sequence of the Dongying Formation in the Liaoxi low uplift. The sequence surface indicates that multistage tectonic action, paleoclimate, paleosalinity, and lake level change jointly controlled the sequence stratigraphy. The illite and illite-smectite mixed layers indicate an arid to semi-arid climate, whereas kaolinite implies humid conditions. Based on this principle, it is clear that the stratigraphic sequence is closely related to paleoclimate. Interpretation of the continental or marine character of the sediments via paleosalinity is increasingly based on the concentration of some trace elements. Hence, the sequence surface can be better evaluated through paleosalinity data. Based on the Sr/Ba and boron content, paleosalinity was evaluated and the sequence boundary was identified. Analysis of the concentration of major and trace elements was used to identify the lithology of the sedimentary region and further discern the stratigraphic sequence. These sequences are composed of lowstand, transgressive, and highstand system tracts. The work herein aimed to understand the reasons for the changes in sequences under the paleoclimate. In addition, major and trace elements, studied together with paleosalinity and clay mineral content, result in the determination of implications for sequence stratigraphy in many other basins. This paper can provide a novel method for comprehensively discerning a sequence surface. Key words: sequence stratigraphy, Dongying Formation, Liaoxi low uplift, Bohai Bay Basin, major and trace elements, paleosalinity. Un changement du niveau de la mer (ou du niveau d'un lac) entraine un changement de l'espace d'accommodation et de la compensation de sediments qui, lui, controle la formation et l'evolution des sequences. Une approche multidisciplinaire reposant sur l'integration de donnees sur les argiles, les elements majeurs et en traces et la paleosalinite et de donnees de sismique tridimensionnelle a ete appliquee a l'interpretation de la sequence stratigraphique de la Formation de Dongying dans le soulevement bas de Liaoxi. La surface de la sequence indique qu'une activite tectonique en plusieurs etapes, le paleoclimat, la paleosalinite et les changements des niveaux de lac ont controle conjointement la stratigraphie sequentielle. Les couches d'illite et d'illite-smectite mixtes indiquent un climat aride a semi-aride, alors que la kaolinite temoigne de conditions humides. Partant de ce principe, il est clair que la sequence stratigraphique est etroitement reliee au paleoclimat. L'interpretation du caractere continental ou marin des sediments a partir de la paleosalinite repose de plus en plus sur la concentration de certains elements en traces. La surface de la sequence est donc mieux evaluee a la lumiere de donnees de paleosalinitie. Les valeurs des rapports Sr/Ba et les teneurs en bore ont ete utilisees pour evaluer la paleosalinite et etablir la limite de la sequence. L'analyse des concentrations d'elements majeurs et en traces a ete utilisee pour etablir la lithologie de la region sedimentaire et caracteriser plus en detail la sequence stratigraphique. Ces sequences sont composees de corteges de bas niveau, transgressifs et de haut niveau. Les travaux presentes visent a etablir les causes des changements dans les sequences au vu du paleoclimat. Les elements majeurs et en traces etudies de concert avec la paleosalinite et les concentrations des argiles jettent en outre un meilleur eclairage sur la stratigraphie sequentielle dans de nombreux autres basins. L'article presente une nouvelle approche pour delimiter de maniere exhaustive la surface d'une sequence. [Traduit par la Redaction] Mots-cles : stratigraphie sequentielle, Formation de Dongying, soulevement bas de Liaoxi, bassin de la baie Bohai, elements majeurs et en traces, paleosalinite., Introduction Sequence stratigraphy is a new subdiscipline formed by the combination of tectonic geology and sedimentology (Bouaziz et al. 2002; Gharbi et al. 2015; Jacquin et al. 1991). As a [...]
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36. The Kanaka Creek fossil flora (Huntingdon Formation), British Columbia, Canada--paleoenvironment and evidence for Paleocene age using palynology and macroflora
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Mathewes, Rolf W., Greenwood, David R., and Love, Renee L.
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Plants -- Analysis ,Coniferous forests -- Analysis ,Fossils -- Analysis ,Zirconium -- Analysis ,Sediments (Geology) -- Analysis ,Earth sciences ,Simon Fraser University ,Royal British Columbia Museum - Abstract
Paleogene sediments of the Huntingdon Formation, a correlative to the Chuckanut Formation of neighbouring Washington State, USA, are exposed in the Greater Vancouver area, British Columbia, Canada. Palynology and plant macrofossils suggest the Kanaka Creek section is Paleocene rather than Eocene in age. Detrital zircon dating is less decisive, yet indicates the Kanaka rocks are no older than Maastrichtian. Analyses of plant macro- and micro-fossils suggest an early to middle Paleocene age for the Kanaka fossil flora. Paleocene indicators include macrofossils such as Platanus bella, Archeampelos, Hamamelites inequalis, and Ditaxocladus, and pollen taxa such as Paraalnipollenites, Triporopollenites mullensis, and Duplopollis. Paleogene taxa such as Woodwardia maxonii, Macclintockia, and Glyptostrobus dominate the flora. Fungal spores including the Late Cretaceous Pesavisparva and the Paleogene Pesavis tagluensis are notable age indicators. Physiognomy of 41 angiosperm leaf morphotypes from Kanaka Creek yields mean annual temperatures in the microthermal to lower mesothermal range (11.2 [+ or -] 4.3 to 14.6 [+ or -] 2.7 [degrees]C from leaf margin analysis; 14.8 [+ or -] 2.1 [degrees]C from Climate Leaf Analysis Multivariate Program), with mild winters (cold month mean temperature 3.9 [+ or -] 3.4 [degrees]C). Paleoclimate was cooler than the upper Paleocene and Eocene members of the Chuckanut Formation. Mean annual precipitation is estimated at ~140 cm with large uncertainties. The Kanaka paleoflora is reconstructed as a mixed conifer-broadleaf forest, sharing common taxa with other western North American Paleocene floras and growing in a temperate moist climate. Kanaka Creek is a rare coastal Paleocene plant locality that provides new insights into coastal vegetation and climate prior to the Paleocene-Eocene Thermal Maximum. Key words: Paleocene, paleobotany, palynology, paleoclimate, Huntingdon Formation, Kanaka Creek. Résumé : Des sédiments paléogènes de la Formation d'Huntingdon, une formation corrélative de la Formation de Chuckanut de l'État voisin de Washington (États-Unis), sont exposés dans la région de Vancouver (Colombie-Britannique, Canada). La palynologie et les macrofossiles de plantes donnent à penser que la coupe de Kanaka Creek est d'âge paléocène plutôt qu'éocène. Si la datation de zircons détritiques est moins concluante, elle indique toutefois que l'âge des roches de Kanaka n'est pas plus vieux que le Maastrichtien. Des analyses de macro- et microfossiles de plantes indiqueraient un âge paléocène précoce à moyen pour la flore fossile de Kanaka. Parmi les indicateurs paléocènes figurent des macrofossiles tels que Platanus bella, Archeampelos, Hamamelites inequalis et Ditaxocladus et des taxons de pollen tels que Paraalnipollenites, Triporopollenites mullensis et Duplopollis. Des taxons paléogènes comme Woodwardia maxonii, Macclintockia et Glyptostrobus sont dominants dans la flore. Des spores fongiques comprenant Pesavis parva d'âge crétacé tardif et Pesavis tagluensis d'âge paléogène sont des indicateurs d'âge notables. L'analyse physionomique de 41 morphotypes de feuilles d'angiosperme de Kanaka Creek produit des températures annuelles moyennes dans une fourchette allant de microthermique à mésothermique inférieure (de 11,2 [+ ou -] 4,3 [degré]C à 14,6 [+ ou -] 2,7 [degré]C obtenues de l'analyse de bordures de feuille, LMA; 14,8 [+ ou -] 2,1 [degré]C obtenue de CLAMP), avec des hivers doux (température moyenne des mois froids : 3,9 [+ or -] 3,4 [degré]C). Le paléoclimat était plus frais que ce qu'enregistrent les membres paléocène supérieur et éocène de la Formation de Chuckanut. Les précipitations annuelles moyennes sont estimées à ~140 cm, avec d'importantes incertitudes. La reconstitution de la paléoflore de Kanaka donne une forêt mixte à conifères-caducifoliés ayant des taxons en commun avec d'autres flores paléocènes de l'ouest de l'Amérique du Nord et croissant dans un climat tempéré humide. Kanaka Creek est une rare localité de plantes paléocènes côtières qui fournit de nouveaux renseignements sur la végétation et le climat côtiers avant le maximum thermique du passage Paléocène/Éocène. [Traduit par la Rédaction] Mots-clés : Paléocène, paléobotanique, palynologie, paléoclimat, Formation d'Huntingdon, Kanaka Creek., Introduction The main objectives of this paper are to assess the age assignment and paleoclimate of the Kanaka Creek paleoflora, southwestern British Columbia, Canada, using plant macrofossils as well as [...]
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- 2020
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37. Geochemistry, zircon geochronology, and isotopic systematics of the Zhanbuzhale granites in the East Kunlun, Qinghai Province, northwestern China: implications for the tectonic setting
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Li, Hao-Ran, Qian, Ye, Sun, Feng-Yue, and Li, Liang
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Granite ,Geochronology ,Petrogenesis ,Marine accidents ,Tectonics (Geology) ,Zirconium ,Earth sciences - Abstract
The Zhanbuzhale region, in the Eastern Kunlun Orogen of northwestern China, is characterized by large volumes of Phanerozoic granitoid rocks and is an ideal region for investigating the tectonic evolution of the Paleo-Tethys system. However, the exact timing of the final closure of the Paleo-Tethys Ocean and initial continental collision remains controversial because of a lack of precise geochronological and detailed geochemical data. In this paper, we report new zircon U-Pb ages and mineralogical, petrographic, and geochemical data for samples of Middle Triassic granodiorite and alkali feldspar granite from the Zhanbuzhale region. The zircon U-Pb ages indicate that the granodiorite and alkali feldspar granite formed at 239 and 236 Ma, respectively. The granodiorites are high-K calc-alkaline, metaluminous, high Sr content, high Sr/Y ratios, low Y content, and show adakite-like affinities. The alkali feldspar granites display high Si[O.sub.2], extremely low MgO, and low Zr+Nb+Ce+Y contents as well as low [Fe.sub.2][O.sub.3]t/MgO ratios, showing metaluminous to peraluminous and high-K calc-alkaline features. Geochemical and petrological characteristics of the alkali feldspar granites suggest that they are highly fractionated I-type granites. The granodiorites and alkali feldspar granites have zircon [[epsilon].sub.Hf](t) values ranging from -2.26 to -0.18, and from -2.17 to +2.18, respectively. Together with regional geological data, we propose that the Triassic (approximately 239-236 Ma) granitoids were generated during the later stages of northward subduction of the Paleo-Tethys oceanic plate, and that the initial stage of collision between the East Kunlun and the Bayan Har-Songpan Ganzi terrane occurred at approximately 236-227 Ma. Key words: Eastern Kunlun Orogen, Middle Triassic granitic rocks, petrogenesis, Paleo-Tethys. La region de Zhanbuzhale, dans la ceinture orogenique du Kunlun oriental du nord-ouest de la Chine, est caracterisee par de grands volumes de roches granitoides phanerozoiques et est une region ideale pour l'etude de l'evolution tectonique du systeme du Paleo-Tethys. Le moment exact de la fermeture definitive de l'ocean Paleo-Tethys et de la collision continentale initiale fait toujours debat en raison du manque de donnees geochronologiques precises et de donnees geochimiques detaillees. Nous faisons etat de nouveaux ages U-Pb sur zircons et de nouvelles donnees mineralogiques, petrographiques et geochimiques pour des echantillons de granodiorite et de granite a feldspath alcalin du Trias moyen de la region de Zhanbuzhale. Les ages U-Pb sur zircons indiquent que la granodiorite et le granite a feldspath alcalin se sont formes a 239 Ma et 236 Ma, respectivement. Les granodiorites sont riches en K, calcoalcalins, metalumineuses, riches en Sr, pauvres en Y, ont des rapports Sr/Y eleves et montrent des affinites adakitiques. Les granites a feldspath alcalin sont riches en Si[O.sub.2], extremement pauvres en MgO, ont de faibles teneurs de Zr+Nb+Ce+Y, de faibles rapports [Fe.sub.2][O.sub.3]t/MgO, et sont metalumineux a hyperalumineux, calcoalcalins et riches en K. Les caracteristiques geochimiques et petrologiques des granites a feldspath alcalin donnent a penser qu'il s'agit de granites fortement fractionnes de type I. Les granodiorites et les granites a feldspath alcalin ont des valeurs de [[epsilon].sub.Hf](t) sur zircons allant de -2,26 a -0,18, et de -2,17 a +2,18, respectivement. Ces resultats, combines aux donnees geologiques regionales, nous permettent de proposer que les granitoides triasiques (environ 239 Ma - 236 Ma) ont ete produits vers la fin de la subduction vers le nord de la plaque oceanique Paleo-Tethys et que le debut de la collision entre le Kunlun oriental et le terrane de Bayan Har-Songpan Ganzi a eu lieu vers 236 Ma - 227 Ma. [Traduit par la Redaction] Mots-cles: ceinture orogenique du Kunlun oriental, roches granitiques du Trias moyen, petrogenese, Paleo-Tethys., Introduction The Eastern Kunlun Orogen (EKO), located on the southern margin of the Qaidam Block (QDM), contains numerous outcrops of Phanerozoic granitoid rocks. The EKO is one of the most [...]
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- 2020
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38. Revised stratigraphy of the middle Simcoe Group (Ordovician, upper Sandbian-Katian) in its type area: an integrated approach
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Paton, Timothy R. and Brett, Carlton E.
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Earth sciences - Abstract
The Upper Ordovician Bobcaygeon Formation of southern Ontario is a widespread unit that spans the Sandbian-Katian stage boundary and contains exceptionally preserved invertebrate fossil assemblages, including the famed 'Kirkfield echinoderm fauna.' However, the precise correlation of this interval remains poorly understood. This paper presents new data on high-resolution sequence and carbon isotope chemostratigraphy of the Bobcaygeon interval based on new quarry exposures and introduces refined definitions of unit boundaries based on allostratigraphic criteria. Sequence, chemo-, and biostratigraphic evidence indicate that the Bobcaygeon Formation represents a composite unit as it encompasses a major erosional unconformity. The Coboconk and Kirkfield formations, described in the early 20th century, were merged into a single unit, the Bobcaygeon, out of concern that the original lithostratigraphic divisions would be conflated with biostratigraphic zones of the same names. However, these biostratigraphic zones are no longer favoured, and the lower member of the Bobcaygeon is here elevated again to the status of formation (Coboconk Formation) and represents the uppermost portion of the Sandbian M4 sequence. The middle and upper members of the Bobcaygeon, herein reassigned to the Kirkfield Formation, represent the upper Sandbian to lower Katian M5A and M5B sequences recognized widely in the eastern and central United States. The term Bobcaygeon is retained and elevated to the rank of subgroup. The Kirkfield Formation is divided into three members and contacts are refined, placing a 1-2 m transgressive grainstone at the base of each sequence. These units are correlated with equivalent strata of New York and the Cincinnati Arch. Key words: Upper Ordovician, Kirkfield Formation, Bobcaygeon Formation, sequence stratigraphy, chemostratigraphy. La Formation de Bobcaygeon de l'Ordovicien superieur du sud de l'Ontario est une unite repandue qui chevauche la limite des etages Sandbiens et Katiens et renferme des assemblages de fossiles invertebres remarquablement bien preserves, dont la celebre << faune d'echinodermes de Kirkfield >>. La correlation precise de cet intervalle demeure toutefois mal comprise. L'article presente de nouvelles donnees de haute resolution sur la chimiostratigraphie sequentielle et des isotopes du carbone de l'intervalle de Bobcaygeon provenant de nouveaux affleurements en carriere et propose des definitions plus fines des limites d'unites basees sur des criteres allostratigraphiques. Les observations sequentielles, chimiostratigraphiques et biostratigraphiques indiquent que la Formation de Bobcaygeon represente une unite composite puisqu'elle renferme une importante discordance d'erosion. Les formations de Coboconk et Kirkfield, decrites au debut du [20.sup.e] siecle, avaient ete fusionnees en une seule unite, la Formation de Bobcaygeon, par peur que les divisions lithostratigraphiques originales ne soient confondues avec les zones biostratigraphiques portant les memes noms. L'usage de ces zones biostratigraphiques n'est toutefois plus preconise, et le membre inferieur de l'intervalle de Bobcaygeon est une fois de plus eleve au statut de formation (Formation de Coboconk) et represente la partie sommitale de la sequence sandbienne M4. Les membres intermediaire et superieur de l'intervalle de Bobcaygeon, reaffectes ici a la Formation de Kirkfield, representent les sequences M5A et M5B du Sandbien superieur au Katien inferieur reconnues largement dans l'est et le centre des Etats-Unis. Le terme Bobcaygeon est retenu et eleve au rang de sous-groupe. La Formation de Kirkfield est divisee en trois membres dont les contacts sont definis plus finement, en placant un grainstone transgressif de 1-2 m a la base de chaque sequence. Ces unites sont correlees a des strates equivalentes de l'Etat de New York et du bombement de Cincinnati. [Traduit par la Redaction] Mots-cles : Ordovicien superieur, Formation de Kirkfield, Formation de Bobcaygeon, stratigraphie sequentielle, chimiostratigraphie., Introduction Upper Ordovician sedimentary rocks in the Lake Simcoe area of southern Ontario, Canada (Fig. 1), dominated by shallow-water subtropical carbonates, provide key insights into paleoenvironments, sea level fluctuations, and [...]
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- 2020
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39. Special Issue in honour of Dale Alan Russell (1937–2019)1.
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Mallon, Jordan C., Currie, Philip J., and Stewart, Kathlyn M.
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DINOSAUR extinction ,DINOSAUR anatomy ,GEOLOGICAL time scales ,EARTH sciences ,SIZE of brain ,FOSSIL microorganisms - Published
- 2021
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40. Zircons to the front: accretionary history of the Rheno-Hercynian active margin (Variscides, Germany)
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Franke, Wolfgang, Huckriede, Hermann, O'Sullivan, Paul, and Wemmer, Klaus
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Exxon Mobil Corp. ,Petroleum industry -- Analysis ,Tectonics (Geology) -- Analysis ,Sedimentary basins -- Analysis ,Zirconium -- Analysis ,Sediments (Geology) -- Analysis ,Earth sciences - Abstract
Our paper reports the detrital zircon record from Late Devonian to late Carboniferous foreland basin deposits in the Rheno-Hercynian (RH) Variscides of Germany. Together with a review of petrography and detrital mineral ages from the literature, the data permit to reconstruct accretion and exhumation along the RH active margin. From Frasnian to latest Carboniferous, the main source (now eroded) was a north-Armorican microcontinent (Franconia) with magmatic rocks representing late Neoproterozoic arc or back-arc, Cambro-Ordovician rift and Silurian--Early Devonian subduction of the Rheic ocean and (or) RH rifting. At ca. 380 Ma, detrital magmatic zircons combined with high- to medium-pressure mica and detrital glaucophane suggest the existence of a paired metamorphic belt at the RH tectonic front. From the Visean onwards, zircons reveal younging of granitoid debris from ca. 380-360 Ma in Late Devonian sediments to ca. 320-300 Ma in the Westphalian C-D and Stephanian. Greywackes of the Namurian A record a change from dominant magmatic clasts toward meta-arenites associated with Baltoscandian zircons, which document accretion to and exhumation from the base of the orogenic wedge. Their source must be sought in metamorphosed Devonian sandstones of the type presently encountered in parts of the active margin crystallines (Mid-German Crystalline High), but in eroded higher units. Basal accretion implies heating of the lower plate beyond the brittle--ductile boundary and supports the model of a high-temperature regime before and during Variscan collision. Palinspastic restoration of the estimated volume of recycled material yields >100 km of distal shelf deposits lost in the process, which adds to the known shortening of the RH basin. The Variscan geology of southwestern England and southern Portugal and provenance studies in those areas are compatible with a geodynamic evolution similar to that in Germany. Key words: detrital zircon, U--Pb laser ICP-MS, foreland basin deposits, Rheno-Hercynian belt, Variscides. Nous rendons compte du registre des zircons detritiques de depots de bassin d'avant-pays d'ages devonien tardif a carbonifere tardif dans la zone rheno-hercynienne (RH) de la chame varisque d'Allemagne. Combinees a un examen de la petrographie et des ages de mineraux detritiques publies, les donnees permettent de reconstituer l'accretion et l'exhumation le long de la marge RH active. Du Frasnien a la fin du Carbonifere, la source principale (aujourd'hui erodee) etait un microcontinent nord-armoricain (la Franconie) avec des roches magmatiques representant un arc ou arriere-arc d'age neoproterozoique tardif, un rift cambro-ordovicien et la subduction du Silurien au Devonien precoce de l'ocean Rheique ou un rifting RH. Vers 380 Ma, des zircons magmatiques detritiques combines a des micas de haute a moyenne pression et du glaucophane detritique indiquer-aient l'existence d'une ceinture metamorphique jumelee au front tectonique RH vers 380 Ma. A partir du Viseen, les zircons revelent un rajeunissement des debris de granitoide a partir d'environ 380-360 Ma dans des sediments d'age devonien tardif a environ 320-300 Ma dans le Westphalien C-D et le Stephanien. Des grauwackes du Namurien A enregistrent le passage de clastes principalement magmatiques a des meta-arenites associees a des zircons baltoscandiens, qui documentent l'accretion a la base du biseau orogenique et l'exhumation subsequente. Leur source doit se trouver dans des gres devoniens metamorphises semblables a ceux qui se trouvent actuellement dans les roches cristallines de la marge active (ride cristalline medio-allemande), mais dans des unites plus hautes erodees. L'accretion basale signifie que la plaque inferieure a ete chauffee au-dela de la limite cassant--ductile et appuie le modele d'un regime de haute temperature avant et durant la collision varisque. La reconstitution palinspatique du volume estime de materiau recycle donne >100 km de depots de plateforme distale evacues durant le processus, ce qui vient s'ajouter au raccourcissement connu du bassin RH. La geologie varisque du sud-ouest de l'Angleterre et du sud du Portugal et des etudes de provenance dans ces regions sont compatibles avec une evolution geodynamique semblable a celle observee en AUemagne. Mots-cles : zircon detritique, analyse U--Pb par ICP-MS avec ablation au laser, depots de bassin d'avant-pays, ceinture rhenohercynienne, chame varisque., Introduction Rationale The Rheno-Hercynian (RH) Variscides (Portugal, southwestern England, Germany, Poland, Turkey) were formed from the infill of the narrow RH ocean. Closure of that ocean is documented, especially in [...]
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- 2019
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41. Musings in tectonics
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Dewey, John F.
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Ophiolites ,Plate tectonics ,Geomorphology ,Lithosphere ,Tectonics (Geology) ,Earth sciences - Abstract
I outline and discuss my career in the context of the history of structural geology and tectonics, the progressive developments that led to plate tectonics, the people who have encouraged and influenced me, the events that changed my life, my fifty six doctoral students who have taught me so much, and my principal interests in tectonics. I discuss, in particular, nine topics of special current interest: the evolution of Tibet, the geomorphology of the British Isles, transtension, the Precambrian, the complexities of plate boundary evolution, Appalachian-Caledonian evolution, ophiolites, the structure and strength of the lithosphere, and the subducting slab. Je presente un survol de ma carriere et une discussion de cette derniere dans le contexte de l'histoire de la geologie structurale et de la tectonique, des avancees progressives qui ont mene a la tectonique des plaques, des personnes qui m'ont encourage et influence, des evenements qui ont change ma vie, de mes 50 etudiants au doctorat qui m'ont tant appris et de mes principaux interets en tectonique. J'aborde plus particulierement neuf sujets d'interet actuel, soit l'evolution du Tibet, la geomorphologie des iles britanniques, la transtension, le Precambrien, les complexites de l'evolution des limites de plaques, l'evolution des Appalaches-Caledonides, les ophiolites, la structure et la resistance de la lithosphere et la plaque plongeante. [Traduit par la Redaction], Rationale This paper is unusual in its purpose and scope, and quite dissimilar to anything that I have written, although it is something that I have thought about for years. [...]
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- 2019
42. Observations: What for?
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Sengor, Celal A.M.
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Students ,Technical institutes ,College teachers ,Earth sciences - Abstract
Observations are to test hypotheses and without hypotheses there can be no usable observations. Geology student should be taught to be independent, bold, imaginative thinkers before they become assiduous observers. Key words: geological observation, role of hypotheses, geological education. Les observations servent a tester des hypotheses, et sans hypothese, il ne peut y avoir d'observations utiles. Il faut enseigner aux etudiants en geologie a etre des penseurs independants, audacieux et imaginatifs avant de devenir des observateurs assidus. Mots-cles: observation geologique, role des hypotheses, formation a la geologie., Acknowledgements in place of an introduction The purpose of this short paper was originally only to thank the people who made this special issue a reality. I have never dreamt [...]
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- 2019
43. Reply to the discussion by van Staal et al. on "The northern Appalachian terrane wreck model".
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Keppie, D.F., Keppie, J.D., and Dostal, J.
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STRUCTURAL geology ,SUTURE zones (Structural geology) ,EARTH sciences ,BACK-arc basins ,GEOLOGICAL surveys ,GEOLOGICAL cross sections - Abstract
In the article, the authors present a comparison of the terrane wreck (TW) model and the in-order terrane (IOT) model that were used in the analysis of rocks and other geological formations in the New Brunswick and Newfoundland areas in Canada. Other topics include the correlative histories of sequential and pseudosynchronous accretionary orogenesis in the IOT model, and the analysis of primary oceans and secondary faulting.
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- 2022
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44. Crustal structure of the metasedimentary Kisseynew domain and bounding volcanic–plutonic domains, Trans-Hudson orogen, Canada.
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Clowes, Ron M. and Roy, Baishali
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EARTH sciences ,SCIENCE projects ,VOLCANIC soils - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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- 2021
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45. Baffin Bay/Nares Strait surface (seafloor) sediment mineralogy: further investigations and methods to elucidate spatial variations in provenance
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Andrews, John T.
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X-rays -- Diffraction ,Clay minerals -- Methods -- Analysis -- Investigations ,Ice sheets -- Methods -- Analysis -- Investigations ,Sediments (Geology) -- Methods -- Analysis -- Investigations ,Company legal issue ,Earth sciences - Abstract
The goal of the paper is to ascertain whether there are significant regional variations in sediment mineral composition that might be used to elucidate ice sheet histories. The weight percentages of nonclay and clay minerals were determined by quantitative X-ray diffraction. Cluster analysis, an unsupervised learning approach, is used to group sediment mineralogy of 263 seafloor/core top samples between ~80[degrees]N and 62[degrees]N. The optimum number of clusters, based on 30 indexes, was three for the weight percentage data but varied with data transformations. Maps of the distribution of the three mineral clusters or facies indicate a significant difference in weight percentages between samples from the West Greenland and Baffin Island shelves. However, several indexes support a larger number of clusters and similar analyses of the spatial distribution and defining minerals of nine mineral facies indicated a strong association with the original three clusters and with broad geographic designations (i.e., West Greenland shelf, Baffin Island fiords, etc). Classification Decision Tree analysis indicates that this difference is primarily controlled by the percentages of plagioclase feldspars versus alkali feldspars. Key words: Baffin Bay, sediment mineralogy, X-ray diffraction, cluster analysis, decision tree. Le but du present article est de verifier si des variations regionales significatives de la composition minerale de sediments peuvent etre utilisees pour elucider l'evolution des calottes glaciaires. Les pourcentages en poids de mineraux argileux et non argileux ont ete determines par diffractometrie quantitative des rayons X. L'analyse typologique, une approche d'apprentissage non supervise, est employee pour regrouper la mineralogie de sediments issus de 263 echantillons du sommet de carottes du fond marin prelevees entre ~80[degrees]N et 62[degrees]N. Le nombre optimal de groupements, a la lumiere de 30 indices, est de trois, peu importe les transformations de donnees operees. Des cartes de la repartition des trois groupements de mineraux ou facies indiquent une difference significative du pourcentage en poids entre les echantillons des plateformes de l'ouest du Groenland et de l'ile de Baffin. Plusieurs indices appuient toutefois un plus grand nombre de groupements, et des analyses similaires de la repartition spatiale et de mineraux caracteristiques de neuf facies mineraux indiquent une forte association avec les trois groupements initiaux et avec de designations geographiques larges (c.-a-d. plateforme de l'ouest du Groenland, fjords de l'ile de Baffin, etc.). Une analyse de classement par arbre de decision indique que cette difference est principalement modulee par les pourcentages relatifs de feldspaths plagioclases et alcalins. [Traduit par la Redaction] Mots-cles: baie de Baffin, mineralogie des sediments, diffractometrie des rayons X, analyse typologique, arbre de decision., Introduction The provenance of glacial marine sediments can provide important information on ice sheet dynamics both temporally and spatially (Jaeger and Koppes 2016; Hemming 2004; Licht and Hemming 2017; Farmer [...]
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- 2019
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46. Geophysical inversion contributions to mineral exploration: lessons from the Footprints project
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Vallee, Marc A., Morris, William A., Perrouty, Stephane, Lee, Robert G., Wasyliuk, Ken, King, Julia J., Ansdell, Kevin, Mir, Reza, Shamsipour, Pejman, Farquharson, Colin G., Chouteau, Michel, Enkin, Randolph J., Smith, Richard S., and Pinet, Nicolas
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Mineral exploration -- Analysis -- Models ,Geophysical surveying -- Models -- Analysis ,Algorithms ,Mining industry ,Real estate development ,Gold industry ,Geophysics ,Uranium ,Earth sciences - Abstract
Magnetic and gravity inversions are used to create 2D or 3D models of the magnetic susceptibility and density, respectively, using potential field data. Unconstrained inversions generate an output based on mathematical constraints imposed by the inversion algorithm. Constrained inversions integrate lithological, structural, and petrophysical information in the inversion process to produce more geologically meaningful results. This study analyses the validity of this assertion in the context of the NSERC-CMIC Mineral Exploration Footprints project. Unconstrained and constrained geophysical inversions were computed for three mining sites: a gold site (Canadian Malartic, Quebec), a copper site (Highland Valley, British Columbia), and a uranium site (Millennium--McArthur River, Saskatchewan). After initially computing unconstrained inversions, constrained inversions were developed using physical property measurements, which directly link geophysics to geology, and lithological boundaries extracted from an interpreted geological model. While each derived geological model is consistent with the geophysical data, each site exhibited some magnetic complexity that confounded the inversion. The gold site includes regions with a strong magnetic signature that masks the more weakly magnetic zone, thereby hiding the magnetic signature associated with the ore body. Initial unconstrained inversions for the copper site yielded solutions with invalid depth extent. A consistency between the constrained model and the geological model is reached with iterative changes to the depth extent of the model. At the uranium site, the observed magnetic signal is weak, but the inversion provided some insights that could be interpreted in terms of an already known complexly folded geological model. Des inversions magnetiques et gravimetriques sont utilisees pour creer des modeles 2D et 3D de la susceptibilite magnetique et de la densite, respectivement, en utilisant des donnees de champ potentiel. Les inversions non contraintes generent un extrant base sur des contraintes mathematiques imposees par le logarithme d'inversion. Les inversions contraintes integrent de l'information lithologique, structurale et petrophysique au processus d'inversion pour produire des resultats plus signifiants sur le plan geologique. Nous analysons la validite de cette affirmation dans le contexte du projet Empreintes (Footprints) de l'exploration miniere du CRSNG et du CCIM. Des inversions geophysiques non contraintes et contraintes sont calculees pour trois sites miniers, soit un site aurifere (Canadian Malartic, Quebec), un site cuprifere (Highland Valley, Colombie-Britannique) et un site uranifere (Millennium--McArthur River, Saskatchewan). Apres le calcul initial d'inversions non contraintes, des inversions contraintes sont obtenues en utilisant des mesures de proprietes physiques qui relient directement la geophysique a lageologie, et des limites lithologiques extraites d'un modele geologique interprete. Si chaque modele geologique obtenu concorde avec les donnees geophysiques, tous les sites presentent une certaine complexite magnetique qui complique l'inversion. Le site aurifere comprend des regions a forte signature magnetique qui masque la zone plus faiblement magnetique, cachant ainsi la signature magnetique associee au corps mineralise. Les inversions non contraintes initiales pour le site cuprifere donnent des solutions caracterisees par un domaine de profondeur invalide. La coherence du modele contraint et du modele geologique est obtenue par des changements iteratifs au domaine de profondeur du modele. Au site uranifere, le signal magnetique observe est faible, mais l'inversion fournit certains renseignements dont l'interpretation pourrait concorder avec un modele geologique existant caracterise par un plissement complexe. [Traduit par la Redaction], Introduction Geophysical inversion methods considered in this paper are mathematical techniques developed to create geophysical models in 2D and 3D of the subsurface from airborne, ground, or borehole geophysical survey [...]
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- 2019
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47. Deep mineral exploration using multi-scale electromagnetic geophysics: the Lalor massive sulphide deposit case study
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Yang, Dikun, Fournier, Dominique, Kang, Seogi, Oldenburg, Douglas W., and Pinet, Nicolas
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Mineral exploration -- Case studies ,Geophysical surveying -- Methods -- Case studies ,Electromagnetic radiation -- Analysis ,Mining industry ,Comparative literature ,Sensors ,Technology ,Electromagnetism ,Workflow software ,Electrical conductivity ,Geophysics ,Earth sciences - Abstract
The Lalor deposit in Snow Lake, central Manitoba, is one of the most significant mineral discoveries in Canada in the past decade. Buried 600 m below the surface, the deposit remained undiscovered until a deep penetrating geophysical electromagnetic (EM) system was employed. Since then, the deposit has been a test site for many modern geophysical systems. This paper presents a comparative study of four EM data sets acquired at Lalor. We image the electrical conductivity structure of the subsurface by carrying out independent 3-D inversions of the data. The four data sets are acquired through airborne, surface, and borehole systems, including airborne natural source EM (ZTEM), airborne time-domain EM (HELITEM), surface large loop EM (SQUID), and borehole EM (PULSE-EM). ZTEM has good depth of penetration, but its inversion model may be biased if the background model is not properly chosen. The HELITEM system can complement ZTEM by validating the actual conductivity of the deposit. With the information provided by airborne surveys, surface EM can better define the geometry of the ore body at a local scale and help in defining drilling targets. Once boreholes are drilled, sensors can be sent downhole, possibly probing the ore lenses that are interbedded at a greater depth. Our 3-D imaging experiments demonstrate that modern geophysical technology is capable of making deep exploration and assisting a more informed process throughout the entire workflow from reconnaissance to drilling and development. Le gisement de Lalor a Snow Lake, dans le centre du Manitoba, constitue l'une des plus importantes decouvertes de la derniere decennie au Canada. Enfoui 600 m sous la surface, le gisement est demeure cache jusqu'a ce que soit utilise un systeme de sondage electromagnetique (EM) profond. Depuis, le gisement est un site d'essai pour de nombreux systemes geophysiques modernes. L'article presente une etude comparative de quatre ensembles de donnees EM acquis a Lalor. Nous produisons une image de la structure de conductivite electrique du sous-sol en realisant des inversions 3D independantes des donnees. Les quatre ensembles de donnees ont ete acquis avec des systemes aeroportes, de surface et de puits, dont l'EM de source naturelle aeroportee (ZTEM), l'EM a dimension temporelle aeroportee (HELITEM), l'EM par grande boucle en surface (SQUID) et l'EM de puits (PULSE-EM). La methode ZTEM offre une bonne profondeur de penetration, mais son modele d'inversion pourrait etre biaise si le modele de fond n'est pas bien selectionne. Le systeme HELITEM peut complementer le systeme ZTEM en validant la conductivite reelle du gisement. Combinee a l'information fournie par des leves aeroportes, l'EM en surface peut permettre de mieux definir la geometrie du corps mineralise a l'echelle locale et aider a etablir des cibles de forage. Une fois que des sondages sont fores, des capteurs peuvent etre envoyes dans le trou, pour possiblement sonder les lentilles mineralisees interstratifiees a de plus grandes profondeurs. Nos experiences d'imagerie 3D demontrent que la technologie geophysique moderne peut etre utilisee pour l'exploration en profondeur et peut favoriser un processus mieux eclaire a toutes les etapes, de la reconnaissance a la mise en valeur en passant par le forage. [Traduit par la Redaction], Introduction Volcanogenic massive sulphide (VMS) deposits are results of ancient hydrothermal activities in submarine volcanic terranes and are major sources of metals like zinc, copper, gold, silver, and lead (Galley [...]
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- 2019
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48. Applying laterally varying density corrections to ground gravity and airborne gravity gradiometry data: a case study from the Bathurst Mining Camp
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Tschirhart, Peter, Morris, William A., Mims, John, Ugalde, Hernan, and Pinet, Nicolas
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Mineral exploration -- Case studies ,Gravity surveying -- Case studies ,Density ,Earth sciences - Abstract
The influence of topography on gravity and gravity gradiometry measurements is profound and should be minimized prior to geological interpretation. The standard way of minimizing these effects is through the computation of a terrain correction. Terrain corrections require two inputs: topography and density. Often, geology and topography are inextricably intertwined: topography is caused by a change in geology. In geologic environments where there is a structural and (or) stratigraphic control on the near-surface mass distribution, using a single density value in the corrections leads to removal of the topographic effect of rocks having the chosen density. Any remaining gravity signal that correlates with topography is providing geological information. If the objective is to produce a gravity map with minimal topographic signal, then a regionally variable density correction is a means of compensating for this effect. In this paper, we demonstrate how to apply a spatially variable density correction using ground gravity and airborne gravity gradiometry data for the geologically complex Bathurst Mining Camp, northern New Brunswick, Canada. Ground gravity and airborne full tensor gravity gradiometry measurements are subdivided into a series of domains on the basis of the underlying tectonostratigraphic group. Terrain and Bouguer corrections are calculated for each domain using representative density values obtained from drill core and surface sampling throughout the Bathurst Mining Camp. The output from the spatially variable density correction is then compared with previous maps. Overall, the differences are subtle, but the spatially variably density allows for isolated anomalies to be better resolved. La topographie exerce une profonde influence sur la gravite et les mesures de gradio-gravimetrie, et cette influence devrait etre minimisee prealablement a toute interpretation geologique. L'approche normale pour minimiser ces effets est par le calcul d'une correction topographique. Cette derniere necessite deux intrants, soit la topographie et la densite. Souvent, la geologie et la topographie sont inextricablement liees, le relief etant cause par des variations de la geologie. Dans les environnements geologiques ou la repartition de la masse pres de la surface est controlee par la structure ou la stratigraphie, l'utilisation d'une valeur de densite unique dans les corrections mene au retrait de l'effet topographique de roches ayant la densite retenue. Tout signal gravimetrique restant qui est correle a la topographie fournit de l'information geologique. Si l'objectif est de produire une carte de la gravite avec un signal topographique minimal, une correction pour la densite variable a l'echelle regionale constitue un moyen de compenser cet effet. Nous montrons comment appliquer une correction pour la densite variable dans l'espace en utilisant des donnees de gravite au sol et de gradio-gravimetrie aeroportee pour le camp minier geologiquement complexe de Bathurst, dans le nord du Nouveau-Brunswick (Canada). Les mesures de gravimetrie de sol et de gradio-gravimetrie aeroportee a tenseur complet sont divisees en une serie de domaines bases sur le groupe tectonostratigraphique sous-jacent. Les corrections topographiques et de Bouguer sont calculees pour chaque domaine en utilisant des valeurs de densite representatives obtenues de carottes et de l'echantillonnage de surface a la grandeur du camp minier de Bathurst. Le resultat de la correction pour la densite variable dans l'espace est ensuite compare a des cartes anterieures. Dans l'ensemble, les differences sont subtiles, mais la densite variable dans l'espace permet une meilleure resolution des anomalies isolees. [Traduit par la Redaction], Introduction In its most basic form, the Bouguer gravity anomaly is the difference between the observed gravity at a location and the complete earth model. That is, the Bouguer anomaly [...]
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- 2019
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49. A New Year's Day icebreaker: icequakes on lakes in Alberta, Canada
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Kavanaugh, Jeffrey, Schultz, Ryan, Andriashek, Laurence D., van der Baan, Mirko, Ghofrani, Hadi, Atkinson, Gail, Utting, Daniel J., and Larson, Kyle
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Earthquakes -- Analysis -- Alberta ,Geological research ,Glaciers -- Environmental aspects ,Lakes -- Environmental aspects ,Water ,Water levels ,Earth sciences - Abstract
Any process that causes a sudden brittle failure of material has the potential to cause earthquake-like seismic events. Cryoseisms represent an underreported class of seismic event due to their (often) small magnitudes. In this paper, we document the phenomenon of some of the largest magnitude lake-associated icequakes ([M.sub.L] 2.0) yet reported. These events occurred nearly simultaneously (within ~2 h) on geographically separate lakes in Alberta, Canada, starting 1 January 2018. We conjecture that these events were caused by the sudden brittle failure of lake ice due to thermal expansion; the effects of the thermal expansion were compounded by the lack of insulating snow cover, high lake water levels, and a rapid onset of atmospheric warming. These factors also contributed to ice-jacking--a repeating process in which thermal contraction produces tensile cracks (leads) in lake ice that are then filled with water that is frozen during the cooling cycle. Thus, any subsequent thermal expansion must be accommodated by new deformation or brittle failure. This ice-jacking process caused creeping ground deformation after the initial brittle failure and again two weeks later following a second warming period. In many cases, the resulting ground deformation was significant enough to cause property damage.Tout processus entrainant une rupture fragile de materiau peut engendrer des evenements sismiques s'apparentant a des tremblements de terre. Les cryoseismes representent une classe sous-signalee d'evenements sismiques en raison de leurs magnitudes (souvent) faibles. Nous documentons le phenomene de certains des tremblements de glace associes a des lacs de plus grande magnitude ([M.sub.L] 2,0) signales a ce jour. Ces evenements se sont produits quasi simultanement (sur une periode d'environ 2 h) dans des lacs separes dans l'espace en Alberta (Canada), a compter du 1er janvier 2018. Nous postulons que ces evenements etaient causes par la rupture fragile soudaine de la glace de lac en raison de l'expansion thermique; les effets de l'expansion thermiques ont ete amplifies par l'absence d'une couverture de neige isolante, les niveaux eleves des lacs et le rechauffement atmospherique rapide. Ces facteurs ont egalement contribue au soulevement de la glace, un processus repetitif selon lequel la contraction thermique produit des fractures par traction (chenaux) dans la glace du lac qui se remplissent ensuite d'eau qui gele durant le cycle de refroidissement, de sorte que toute expansion thermique subsequente doit etre accommodee par une nouvelle deformation ou rupture fragile. Ce processus de soulevement de la glace a cause une deformation par reptation du sol apres la rupture fragile initiale, puis deux semaines plus tard, apres une deuxieme periode de rechauffement. Dans de nombreux cas, la deformation du sol en decoulant etait assez importante pour causer des dommages materiels. [Traduit par la Redaction], IntroductionCryoseisms are a class of seismic event that has garnered increased attention in recent years (Podolskiy and Walter 2016; Aster and Winberry 2017). Understandably, the major part of this attention [...]
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- 2019
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50. Description of a partial Dromiceiomimus (Dinosauria: Theropoda) skeleton with comments on the validity of the genus
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Macdonald, Ian, Currie, Philip J., and Sues, Hans-Dieter
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Phylogeny -- Analysis ,Animal remains (Archaeology) -- Analysis ,Dinosaurs -- Physiological aspects -- Identification and classification ,Earth sciences - Abstract
Dromiceiomimus brevitertius is a North American ornithomimid diagnosed primarily by the ratio of tibia length to femur length. It has recently, and perhaps incorrectly, been considered synonymous with Ornithomimus edmontonicus, with several authors questioning the utility of limb ratios in diagnosing taxa. While isolated ornithomimosaur material is common, specimens with sufficient diagnostic material to explore the question of synonymy are comparatively rare. The putative Dromiceiomimus specimen UALVP 16182 represents one of the few specimens in which diagnostic elements are available. It is therefore an important specimen for assessing the validity of Dromiceiomimus and for examining the utility of using limb proportions to diagnose ornithomimid taxa. In this paper, UALVP 16182 is described, the tibia/femur ratio is examined in closely related ornithomimid taxa, and the ratio is found to distinguish Dromiceiomimus from Gallimimus, Ornithomimus, and Struthiomimus. A phylogenetic analysis recovered Anserimimus and Ornithomimus as sister taxa with Dromiceiomimus as an outgroup. Comparison of the manus revealed differences in the morphology of metacarpal I and the flexor tubercle of manual ungual II-3. Differences also appear in the surangular and scapula. An examination of stratigraphic positions of various specimens indicates that Dromiceiomimus is generally higher in section than Ornithomimus, although there are too few specimens to be statistically significant. This study agrees with other studies in concluding that limb proportions are roughly isometric in small theropods like ornithomimids and that the tibia/femur ratio may therefore be useful for diagnosing certain small taxa. These findings suggest that Dromiceiomimus may indeed be a valid taxon.Dromiceiomimus brevitertius est un ornithomimide nord-americain identifie principalement sur la base du rapport des longueurs du tibia et du femur. Il a recemment, et peut-etre incorrectement, ete considere comme synonyme d'Ornithomimus edmontonicus, plusieurs auteurs remettant en question l'utilite des rapports de longueurs de membre pour l'identification de taxons. Si du materiau d'ornithomimosaure est repandu, les specimens pour lesquels le materiau diagnostique disponible est suffisant pour l'exploration de la synonymie sont relativement rares. Le specimen presume de Dromiceiomimus UALVP 16182 represente un des rares specimens pour lesquels des elements diagnostiques sont disponibles. Il s'agit donc d'un specimen important pour evaluer la validite de Dromiceiomimus et examiner l'utilite des proportions de membres pour identifier des taxons d'ornithomimides. Dans le present article, UALVP 16182 est decrit, le rapport tibia: femur est examine chez des taxons etroitement relies d ornithomimides et il est etabli que ce rapport permet de distinguer Dromiceiomimus de Gallimimus, Ornithomimus et Struthiomimus. Une analyse phylogenetique revele qu'Anserimimus et Ornithomimus sont des taxons freres et Dromiceiomimus, un exogroupe. Une comparaison de la main revele des differences dans la morphologie du metacarpien I et du tubercule carpien de l'ungueal manuel II-3. Des differences sont egalement presentes dans le surangulaire et la scapula. Un examen des positions stratigraphiques de differents specimens indique que Dromiceiomimus est generalement situe plus haut dans la coupe qu'Ornithomimus, bien que les specimens soient trop peu nombreux pour etre statistiquement significatifs. Les conclusions de la presente etude concordent avec celles d'etudes anterieures voulant que les proportions des membres soient a peu pres isometriques chez les petits theropodes comme les ornithomimides et que le rapport tibia: femur pourrait donc etre utile pour identifier certains petits taxons. Ces constatations donnent a penser que Dromiceiomimus pourrait bien etre un taxon valide. [Traduit par la Redaction], IntroductionOrnithomimosauria is a group of lightly built, cursorial theropods found mainly in the Cretaceous of Asia and North America (Makovicky et al. 2004). They resemble modern ratites like ostriches in [...]
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- 2019
- Full Text
- View/download PDF
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