This article presents a history of the development of U-Pb geochronology with emphasis on the role of Canadian researchers and some of its applications to Canadian geology. Modern U-Pb dating is the result of work by many individuals over the past 60 years, but the most important was Tom Krogh, who established methods that allowed determination of precise ages (<0.1% errors) on zircon using isotope dilution thermal ionization mass spectrometry (ID-TIMS). This was followed by the introduction of new analytical approaches by others, notably secondary ion mass spectrometry (SIMS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) that allow intra-crystal domains to be dated. U-Pb geochronology is now an indispensable tool for understanding the Earth. In collaboration with field mapping it has vastly improved our understanding of the geological history of Canada as well as understanding important geological events such as mass extinctions, secular changes in geological processes and the birth of the solar system.
{"title":"U-PB GEOCHRONOLOGY: ITS DEVELOPMENT AND IMPORTANCE IN CANADA","authors":"D. Davis","doi":"10.1139/cjes-2023-0009","DOIUrl":"https://doi.org/10.1139/cjes-2023-0009","url":null,"abstract":"This article presents a history of the development of U-Pb geochronology with emphasis on the role of Canadian researchers and some of its applications to Canadian geology. Modern U-Pb dating is the result of work by many individuals over the past 60 years, but the most important was Tom Krogh, who established methods that allowed determination of precise ages (<0.1% errors) on zircon using isotope dilution thermal ionization mass spectrometry (ID-TIMS). This was followed by the introduction of new analytical approaches by others, notably secondary ion mass spectrometry (SIMS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) that allow intra-crystal domains to be dated. U-Pb geochronology is now an indispensable tool for understanding the Earth. In collaboration with field mapping it has vastly improved our understanding of the geological history of Canada as well as understanding important geological events such as mass extinctions, secular changes in geological processes and the birth of the solar system.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"63 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89356153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mount Garibaldi Volcanic System (MGVS) is the southernmost member of Garibaldi Volcanic Belt (GVB), the northern (Canadian) segment of the Cascade Volcanic Arc. Temporally episodic explosive to effusive eruptions may be associated with peak ice unloading after glacial maxima. Rapid and widespread deglaciation of the overlying ice sheet, and glacial rebound, have altered the physical characteristics of the landscape whilst the system is thought to have been in long repose for over 10 000 years. Over the last 60 years, the region has become heavily populated due to increased tourism and all-season recreation opportunities. MGVS poses the greatest volcanic threat to the human population and built infrastructure between Vancouver and the resort municipality of Whistler. We believe that this system is a priority for further scientific research, given that its already “very high” overall threat score would likely increase if there was a better understanding of its eruptive history and hazards. Using published and field evidence, we show that potential hazards, related to the volcanic environment of this system, to the settlement of Squamish include voluminous lava flows, pyroclastic density currents triggered by lava dome collapse, tephra fallout, debris flows, and lahars. As relatively few exposures in the system have been dated using modern geochronological techniques, we take this opportunity to (re)calibrate published radiocarbon ages of relatively recent eruptions in GVB.
{"title":"Mount Garibaldi: hazard potential from a long-dormant volcanic system in the Pacific Northwest","authors":"Conner A. G. Morison, C. Hickson","doi":"10.1139/cjes-2022-0067","DOIUrl":"https://doi.org/10.1139/cjes-2022-0067","url":null,"abstract":"Mount Garibaldi Volcanic System (MGVS) is the southernmost member of Garibaldi Volcanic Belt (GVB), the northern (Canadian) segment of the Cascade Volcanic Arc. Temporally episodic explosive to effusive eruptions may be associated with peak ice unloading after glacial maxima. Rapid and widespread deglaciation of the overlying ice sheet, and glacial rebound, have altered the physical characteristics of the landscape whilst the system is thought to have been in long repose for over 10 000 years. Over the last 60 years, the region has become heavily populated due to increased tourism and all-season recreation opportunities. MGVS poses the greatest volcanic threat to the human population and built infrastructure between Vancouver and the resort municipality of Whistler. We believe that this system is a priority for further scientific research, given that its already “very high” overall threat score would likely increase if there was a better understanding of its eruptive history and hazards. Using published and field evidence, we show that potential hazards, related to the volcanic environment of this system, to the settlement of Squamish include voluminous lava flows, pyroclastic density currents triggered by lava dome collapse, tephra fallout, debris flows, and lahars. As relatively few exposures in the system have been dated using modern geochronological techniques, we take this opportunity to (re)calibrate published radiocarbon ages of relatively recent eruptions in GVB.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"161 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84786744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Maryam Errami, A. Algouti, Abdellah Algouti, A. Farah
This study provides the first evaluation of the potential of both Landsat-8 Operational Land Imager (OLI) sensor images and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) data, for automated lineament extraction in the south side of Marrakech High Atlas (MHA), (Telouet-Tighza area). After image corrections, enhancement methods such as Principal Component Analysis (PCA), Band Composite (BC) and Directional Filter (DF) were adopted in order to create new images that provide high visibility of linear structures. The new Landsat BC image used in this study was selected based on the calculation of the optimum index factor (OIF) and Correlation Index. In addition to the Landsat image, the SRTM DEM is used to detect structural lineaments in the area, by generating shaded relief images. Multi-source data, such as Band Ratio (BR) image, geological maps and fieldwork, were used to eliminate the non-geological lineaments extracted. The results indicate that automated method was applied successfully for lineament mapping in this area, by detailing the main tectonic faults. Moreover, new lineaments are identified and are validated by field works. Structural lineaments extracted show compatibility in their direction, length, distribution and density with the tectonic evolution of the study area. A total of 2945 lineaments are extracted with major ENE-WSW, and predominant E-W directions. The new structural map shows more structural information compared with the geological map of this area, and exemplifies the performance of Landsat-8 OLI bands and SRTM data in this kind of study.
{"title":"Mapping and analysis of structural lineaments using SRTM radar data and Landsat-8 OLI image: an example from the Telouet-Tighza area, Marrakech High Atlas, Morocco","authors":"Maryam Errami, A. Algouti, Abdellah Algouti, A. Farah","doi":"10.1139/cjes-2022-0113","DOIUrl":"https://doi.org/10.1139/cjes-2022-0113","url":null,"abstract":"This study provides the first evaluation of the potential of both Landsat-8 Operational Land Imager (OLI) sensor images and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) data, for automated lineament extraction in the south side of Marrakech High Atlas (MHA), (Telouet-Tighza area). After image corrections, enhancement methods such as Principal Component Analysis (PCA), Band Composite (BC) and Directional Filter (DF) were adopted in order to create new images that provide high visibility of linear structures. The new Landsat BC image used in this study was selected based on the calculation of the optimum index factor (OIF) and Correlation Index. In addition to the Landsat image, the SRTM DEM is used to detect structural lineaments in the area, by generating shaded relief images. Multi-source data, such as Band Ratio (BR) image, geological maps and fieldwork, were used to eliminate the non-geological lineaments extracted. The results indicate that automated method was applied successfully for lineament mapping in this area, by detailing the main tectonic faults. Moreover, new lineaments are identified and are validated by field works. Structural lineaments extracted show compatibility in their direction, length, distribution and density with the tectonic evolution of the study area. A total of 2945 lineaments are extracted with major ENE-WSW, and predominant E-W directions. The new structural map shows more structural information compared with the geological map of this area, and exemplifies the performance of Landsat-8 OLI bands and SRTM data in this kind of study.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"25 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90497281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kirsti P. R. Medig, D. Thorkelson, E. Turner, R. Rainbird, H. Gibson, D. Marshall
Geochemical and geochronological data from the Pinguicula Group and unit PR1 of the lower Fifteenmile Group (Yukon, Canada) provide information on sediment provenance and timing of break-up of supercontinent Columbia and seaway development on Laurentia’s northwestern margin. The older unit PR1, in the Coal Creek inlier, has a near-unimodal detrital zircon population with an age of 1499 ± 3 Ma. The Pinguicula Group detrital zircon data, in the Wernecke and Hart River inliers, display a polymodal detrital zircon population with a maximum age of <1322 ± 23 Ma. Using detrital zircon signatures, Sm–Nd isotopic data, and C-isotopic signatures, lithostratigraphic correlations between the Pinguicula Group in the Wernecke and Hart River inliers are confirmed, whereas the Pinguicula Group and unit PR1 are no longer considered correlative. The zircon population in unit PR1 requires a proximal source, but sources of this age are not known in western Laurentia. Based on detrital zircon and Sm–Nd data, sediment in unit PR1 was derived from the Mt. Isa inlier in northeastern Australia sometime after 1460 Ma. Unit PR1 correlates with older Mesoproterozoic successions, including the Belt-Purcell, that were deposited during break-up of supercontinent Columbia, and contain sediment from Australia and the Mawson continent. Mesoproterozoic successions deposited after 1.45 Ga, including the Missoula Group, lack North American Magmatic Gap (NAMG)-aged zircon and instead record sediment provenance from southern Laurentia, as north Australia and the Mawson continent rifted from Laurentia’s western margin. The Pinguicula Group has few NAMG-aged grains that were probably recycled from older Mesoproterozoic basins.
{"title":"Mesoproterozoic basins (Yukon, Canada) in the evolution of supercontinent Columbia","authors":"Kirsti P. R. Medig, D. Thorkelson, E. Turner, R. Rainbird, H. Gibson, D. Marshall","doi":"10.1139/cjes-2022-0055","DOIUrl":"https://doi.org/10.1139/cjes-2022-0055","url":null,"abstract":"Geochemical and geochronological data from the Pinguicula Group and unit PR1 of the lower Fifteenmile Group (Yukon, Canada) provide information on sediment provenance and timing of break-up of supercontinent Columbia and seaway development on Laurentia’s northwestern margin. The older unit PR1, in the Coal Creek inlier, has a near-unimodal detrital zircon population with an age of 1499 ± 3 Ma. The Pinguicula Group detrital zircon data, in the Wernecke and Hart River inliers, display a polymodal detrital zircon population with a maximum age of <1322 ± 23 Ma. Using detrital zircon signatures, Sm–Nd isotopic data, and C-isotopic signatures, lithostratigraphic correlations between the Pinguicula Group in the Wernecke and Hart River inliers are confirmed, whereas the Pinguicula Group and unit PR1 are no longer considered correlative. The zircon population in unit PR1 requires a proximal source, but sources of this age are not known in western Laurentia. Based on detrital zircon and Sm–Nd data, sediment in unit PR1 was derived from the Mt. Isa inlier in northeastern Australia sometime after 1460 Ma. Unit PR1 correlates with older Mesoproterozoic successions, including the Belt-Purcell, that were deposited during break-up of supercontinent Columbia, and contain sediment from Australia and the Mawson continent. Mesoproterozoic successions deposited after 1.45 Ga, including the Missoula Group, lack North American Magmatic Gap (NAMG)-aged zircon and instead record sediment provenance from southern Laurentia, as north Australia and the Mawson continent rifted from Laurentia’s western margin. The Pinguicula Group has few NAMG-aged grains that were probably recycled from older Mesoproterozoic basins.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"236 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75537999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dinosaurs have attracted varying degrees of scientific and public interest since their initial description in 1824. Interest has steadily increased, however, since the late 1960s when the Dinosaur Renaissance began, and when the Canadian Journal of Earth Sciences started to publish. Since then, there has been a feedback system (international in scope) promoting increased scientific activity and ever-increasing public attention. This has led to ever more dinosaur discoveries internationally; increased numbers of museums and parks displaying dinosaurs; more publications, blogs, and other media on dinosaurs; and (most importantly) increased numbers of people and institutions doing research on dinosaurs. About 30 new species of dinosaurs are now being described every year, adding to the more than 1000 species already known. Furthermore, it is now acknowledged by most biologists and palaeontologists that modern birds are the direct descendants of dinosaurs, and that they are classified as part of the Dinosauria. Recognizing that there are more than 11 000 species of living dinosaurs has given us a better understanding of many aspects of the biology of nonavian dinosaurs. Along with technological improvements, this has revealed new—and often surprising—facts about their anatomy (bones, soft tissues, and even colours), interrelationships, biomechanics, growth and variation, ecology, physiology, behaviour, and extinction. In spite of the intensity of research over the last six decades, there is no indication that the discovery of new species and new facts about their biology is slowing down. It is quite clear that there is still a lot to be learned!
{"title":"Celebrating dinosaurs: their behaviour, evolution, growth, and physiology","authors":"P. Currie","doi":"10.1139/cjes-2022-0131","DOIUrl":"https://doi.org/10.1139/cjes-2022-0131","url":null,"abstract":"Dinosaurs have attracted varying degrees of scientific and public interest since their initial description in 1824. Interest has steadily increased, however, since the late 1960s when the Dinosaur Renaissance began, and when the Canadian Journal of Earth Sciences started to publish. Since then, there has been a feedback system (international in scope) promoting increased scientific activity and ever-increasing public attention. This has led to ever more dinosaur discoveries internationally; increased numbers of museums and parks displaying dinosaurs; more publications, blogs, and other media on dinosaurs; and (most importantly) increased numbers of people and institutions doing research on dinosaurs. About 30 new species of dinosaurs are now being described every year, adding to the more than 1000 species already known. Furthermore, it is now acknowledged by most biologists and palaeontologists that modern birds are the direct descendants of dinosaurs, and that they are classified as part of the Dinosauria. Recognizing that there are more than 11 000 species of living dinosaurs has given us a better understanding of many aspects of the biology of nonavian dinosaurs. Along with technological improvements, this has revealed new—and often surprising—facts about their anatomy (bones, soft tissues, and even colours), interrelationships, biomechanics, growth and variation, ecology, physiology, behaviour, and extinction. In spite of the intensity of research over the last six decades, there is no indication that the discovery of new species and new facts about their biology is slowing down. It is quite clear that there is still a lot to be learned!","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"6 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87624793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In intraplate areas where regional tectonic strain is accommodated by reactivation of pre-existing structures, the level of seismic hazard associated with faults in may be underestimated due to the poor surface expression of faults, scattered earthquake distribution, and long earthquake recurrence intervals. The cause of seismicity in eastern Canada remains unresolved. This is partially because surface expression of faults have been eroded during glacial and deglacial periods and in many cases are undetectable until a seismic event. Morphotectonic analysis has been widely applied to assess relative tectonic activity in various geological settings. To establish whether active uplift is occurring and to investigate the spatial distribution of uplift rates, 131 bedrock drainage basins in the Ottawa-Bonnechere Graben (OBG) were analysed. The aim of this was to: 1) test the applicability of geomorphic indices for quantifying active deformation, 2) quantify the spatiotemporal distribution of relative uplift rates, and 3) explore the implications for faulting mechanisms, deformation styles, and ultimately regional seismic hazard. We measured valley floor width-to-height ratio (Vf), basin elongation ratio (Re), basin hypsometric integral (HI), and normalized channel steepness index (ksn). The results demonstrate that high relative uplift rates occur in all six bedrock escarpment sections studied and suggests that are possibly associated with regional broad wavelength uplift (epeirogeny) resulting from a likely complex interaction between far field tectonic stress and glacial isostatic adjustment (GIA). Our analysis showed that Vf, Re, and ksn reveals no considerable spatial differences in high relative uplift rates, consistent with the Canadian base network GPS uplift rates.
{"title":"Tectonic geomorphology of the Ottawa-Bonnechere Graben, Eastern Canada: implications for regional uplift and intraplate seismicity","authors":"U. K. Gusti, A. Peace, J. Rimando","doi":"10.1139/cjes-2022-0137","DOIUrl":"https://doi.org/10.1139/cjes-2022-0137","url":null,"abstract":"In intraplate areas where regional tectonic strain is accommodated by reactivation of pre-existing structures, the level of seismic hazard associated with faults in may be underestimated due to the poor surface expression of faults, scattered earthquake distribution, and long earthquake recurrence intervals. The cause of seismicity in eastern Canada remains unresolved. This is partially because surface expression of faults have been eroded during glacial and deglacial periods and in many cases are undetectable until a seismic event. Morphotectonic analysis has been widely applied to assess relative tectonic activity in various geological settings. To establish whether active uplift is occurring and to investigate the spatial distribution of uplift rates, 131 bedrock drainage basins in the Ottawa-Bonnechere Graben (OBG) were analysed. The aim of this was to: 1) test the applicability of geomorphic indices for quantifying active deformation, 2) quantify the spatiotemporal distribution of relative uplift rates, and 3) explore the implications for faulting mechanisms, deformation styles, and ultimately regional seismic hazard. We measured valley floor width-to-height ratio (Vf), basin elongation ratio (Re), basin hypsometric integral (HI), and normalized channel steepness index (ksn). The results demonstrate that high relative uplift rates occur in all six bedrock escarpment sections studied and suggests that are possibly associated with regional broad wavelength uplift (epeirogeny) resulting from a likely complex interaction between far field tectonic stress and glacial isostatic adjustment (GIA). Our analysis showed that Vf, Re, and ksn reveals no considerable spatial differences in high relative uplift rates, consistent with the Canadian base network GPS uplift rates.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"36 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87270126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Robert David Meek, A. Ielpi, R. Rainbird, W. Davis
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 reveal 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 up-section 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.
中元古代Husky Creek组是一个层间红层和玄武岩包裹体，覆盖在约2.5公里厚的区域广泛的玄武岩高原上，与1.27 Ga Mackenzie大火成岩省相连。这种演替为研究同时期河流沉积和洪水玄武岩火山作用之间的相互作用提供了机会。赫斯基河组厚度约1900 m，主要由河道和次级洪泛平原组成，以风成地层为主，岩屑碎屑与玄武岩流穿插。对Husky Creek组4个地层的碎屑锆石颗粒进行U-Pb定年，揭示了两个主要的年龄组:(1)1270 Ma峰属于Mackenzie大火成岩省;(2)前1.6 Ga碎屑锆石年龄，反映了Laurentia西北部的广泛地区，并被解释为来自霍恩比湾盆地下伏沉积岩的再循环。1270 Ma左右的锆石颗粒比例上剖面降低，砂岩成分成熟度增加，反映了火山堆埋藏时期流域的扩张，随着Husky Creek组的积累，循环作用更加明显。赫斯基河组沉积在麦肯齐火成岩事件的末期，由西流的河流沉积到一个地理上受限制的盆地，该盆地位于一个广阔的基性火山高原之上。这篇论文提供了在地球上最大的火成岩事件之一之后的河流盆地发展的见解。
{"title":"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.","authors":"Robert David Meek, A. Ielpi, R. Rainbird, W. Davis","doi":"10.1139/cjes-2022-0059","DOIUrl":"https://doi.org/10.1139/cjes-2022-0059","url":null,"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 reveal 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 up-section 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.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"15 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88133252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Mesnard Quartzite of Paleoproterozoic age is believed to represent among the first preserved cratonal continental rocks in the Lake Superior region, was deposited above Archean basement in the Marquette structural trough and is estimated to contain more than 99% sandstone (now quartzite) beds. The Mesnard Quartzite is interpreted to have been deposited largely by tidal currents. Evidence of tidal current deposition includes lack of wave-influenced structures such as hummocky cross-beds, and presence of strongly unidirectional paleocurrents from cross-beds, mud-drapes on cross-bed foresets, evidence of current reversal including herringbone cross-bedding and sigmoidal cross-bedding. Sandstone bedding types include homogeneous or structureless beds, parallel-laminated beds, cross-beds, and symmetric ripple marks. Unidirectional paleocurrents from cross-beds are largely subparallel to the axis of the Marquette structural trough, leading to the interpretation that the trough was subsiding during deposition. Cross-bed set thickness and symmetric ripple marks both support the interpretation of shallow water marine deposition, likely only a few meters. Although the Mesnard Quartzite is on the order of 110 m thick, there is no evidence of internal sequence boundaries or flooding surfaces, and low accommodation during deposition is inferred. The climate during deposition is interpreted to be humid, and tropical to subtropical based on the quartz arenite composition. Deposition likely occurred in a failed rift basin or in an intracratonic extensional basin.
{"title":"Cratonal tidal deposits of the Paleoproterozoic Mesnard Quartzite, Lake Superior region: interpretation challenges","authors":"D. Larue","doi":"10.1139/cjes-2022-0049","DOIUrl":"https://doi.org/10.1139/cjes-2022-0049","url":null,"abstract":"The Mesnard Quartzite of Paleoproterozoic age is believed to represent among the first preserved cratonal continental rocks in the Lake Superior region, was deposited above Archean basement in the Marquette structural trough and is estimated to contain more than 99% sandstone (now quartzite) beds. The Mesnard Quartzite is interpreted to have been deposited largely by tidal currents. Evidence of tidal current deposition includes lack of wave-influenced structures such as hummocky cross-beds, and presence of strongly unidirectional paleocurrents from cross-beds, mud-drapes on cross-bed foresets, evidence of current reversal including herringbone cross-bedding and sigmoidal cross-bedding. Sandstone bedding types include homogeneous or structureless beds, parallel-laminated beds, cross-beds, and symmetric ripple marks. Unidirectional paleocurrents from cross-beds are largely subparallel to the axis of the Marquette structural trough, leading to the interpretation that the trough was subsiding during deposition. Cross-bed set thickness and symmetric ripple marks both support the interpretation of shallow water marine deposition, likely only a few meters. Although the Mesnard Quartzite is on the order of 110 m thick, there is no evidence of internal sequence boundaries or flooding surfaces, and low accommodation during deposition is inferred. The climate during deposition is interpreted to be humid, and tropical to subtropical based on the quartz arenite composition. Deposition likely occurred in a failed rift basin or in an intracratonic extensional basin.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"12 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82136141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sedimentary rocks of the Ocoee Supergroup crop out in the Appalachian Blue Ridge of western North Carolina and eastern Tennessee. This ~12 km thick sequence of strata was mapped as nonconformably overlying Mesoproterozoic crystalline basement (about 1.20-1.02 Ga) and beneath the lower Cambrian Chilhowee Group, leading to the traditional interpretation that the Ocoee Supergroup was deposited between about 1.02 and 0.54 Ga. This interpretation was challenged by Unrug and Unrug (1990) and Unrug and others (2000), who claimed that Paleozoic fossils were recovered from rocks of the Walden Creek Group (upper Ocoee), and thereby created a new tectonic model for the origin of Laurentia. To resolve the age controversy concerning the time of deposition of the Ocoee Supergroup, diagenetic xenotime overgrowths on detrital zircon and diagenetic monazite on detrital monazite were dated by the U-Pb method. Sensitive high resolution ion microprobe (SHRIMP) ages of diagenetic xenotime from three samples of sandstone (Thunderhead Sandstone, Cades Sandstone, and Shields Formation) indicate that the Ocoee Supergroup was deposited in the interval of about 580-550 Ma. A sample of Sandsuck Formation (uppermost Ocoee) yielded xenotime overgrowths of about 410 Ma, probably related to post-depositional low-grade metamorphism. Various origins of xenotime overgrowths may be distinguished by trace element distributions. Ages and trace element concentrations of monazite overgrowths support the xenotime age results, although concordia systematics are complicated by high concentrations of common Pb and inheritance of ages ~1.2 and 0.6 Ga. These age data support the observed field relations for a late Neoproterozoic depositional age of the Ocoee Supergroup.
{"title":"SHRIMP U-Pb geochronology of Mesoproterozoic basement and overlying Ocoee Supergroup, NC-TN: dating diagenetic xenotime and monazite overgrowths on detrital minerals to determine the age of sedimentary deposition","authors":"J. Aleinikoff, C. Southworth, C. Fanning","doi":"10.1139/cjes-2022-0093","DOIUrl":"https://doi.org/10.1139/cjes-2022-0093","url":null,"abstract":"Sedimentary rocks of the Ocoee Supergroup crop out in the Appalachian Blue Ridge of western North Carolina and eastern Tennessee. This ~12 km thick sequence of strata was mapped as nonconformably overlying Mesoproterozoic crystalline basement (about 1.20-1.02 Ga) and beneath the lower Cambrian Chilhowee Group, leading to the traditional interpretation that the Ocoee Supergroup was deposited between about 1.02 and 0.54 Ga. This interpretation was challenged by Unrug and Unrug (1990) and Unrug and others (2000), who claimed that Paleozoic fossils were recovered from rocks of the Walden Creek Group (upper Ocoee), and thereby created a new tectonic model for the origin of Laurentia. To resolve the age controversy concerning the time of deposition of the Ocoee Supergroup, diagenetic xenotime overgrowths on detrital zircon and diagenetic monazite on detrital monazite were dated by the U-Pb method. Sensitive high resolution ion microprobe (SHRIMP) ages of diagenetic xenotime from three samples of sandstone (Thunderhead Sandstone, Cades Sandstone, and Shields Formation) indicate that the Ocoee Supergroup was deposited in the interval of about 580-550 Ma. A sample of Sandsuck Formation (uppermost Ocoee) yielded xenotime overgrowths of about 410 Ma, probably related to post-depositional low-grade metamorphism. Various origins of xenotime overgrowths may be distinguished by trace element distributions. Ages and trace element concentrations of monazite overgrowths support the xenotime age results, although concordia systematics are complicated by high concentrations of common Pb and inheritance of ages ~1.2 and 0.6 Ga. These age data support the observed field relations for a late Neoproterozoic depositional age of the Ocoee Supergroup.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"15 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75396530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Newfoundland and Labrador Shelves Bioregion, located on the glaciated continental shelf and adjacent continental slope of eastern Canada, is classified into units that reflect its great physiographic diversity. There are ten shelf units: bedrock zone, fiord systems, major inlet, shelf-crossing troughs, four types of offshore banks, basin, and disturbed (glaciotectonic) terrain. There are three units on the continental slope: channelized areas, trough-mouth areas, and large sedimentary drifts. A series of vignettes illustrates both the distinguishing characteristics of the principal geomorphic units and the morphologic diversity within them. A sediment mobility analysis reveals that wave and current-generated disturbance is dominant and largely depth-controlled within the shelf units, while the south-flowing Labrador Current impacts sediment transport and mobility along the continental slope.
{"title":"Geomorphic diversity of the Newfoundland and Labrador Shelves Bioregion","authors":"J. Shaw, Michael Z. Li, V. Kostylev","doi":"10.1139/cjes-2022-0080","DOIUrl":"https://doi.org/10.1139/cjes-2022-0080","url":null,"abstract":"The Newfoundland and Labrador Shelves Bioregion, located on the glaciated continental shelf and adjacent continental slope of eastern Canada, is classified into units that reflect its great physiographic diversity. There are ten shelf units: bedrock zone, fiord systems, major inlet, shelf-crossing troughs, four types of offshore banks, basin, and disturbed (glaciotectonic) terrain. There are three units on the continental slope: channelized areas, trough-mouth areas, and large sedimentary drifts. A series of vignettes illustrates both the distinguishing characteristics of the principal geomorphic units and the morphologic diversity within them. A sediment mobility analysis reveals that wave and current-generated disturbance is dominant and largely depth-controlled within the shelf units, while the south-flowing Labrador Current impacts sediment transport and mobility along the continental slope.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"53 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91002734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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