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.
{"title":"Taphonomy and depositional history of the Southfork Quarry (Cypress Hills Formation, late Eocene) in southwestern Saskatchewan, Canada","authors":"Meagan M. Gilbert, Frank H. McDougall","doi":"10.1139/cjes-2021-0161","DOIUrl":"https://doi.org/10.1139/cjes-2021-0161","url":null,"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.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"118 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77923524","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}
T. James, A. Blais-Stevens, J. Clague, D. Forbes, A. LeBlanc, Sharon L. Smith
No abstract for this introductory article.
这篇介绍性文章没有摘要。
{"title":"Introduction to Landscape & Seascape Responses to Canada’s Changing Climate","authors":"T. James, A. Blais-Stevens, J. Clague, D. Forbes, A. LeBlanc, Sharon L. Smith","doi":"10.1139/cjes-2022-0095","DOIUrl":"https://doi.org/10.1139/cjes-2022-0095","url":null,"abstract":"No abstract for this introductory article.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"95 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88407892","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}
Rocio Pedreira Perez, A. Tremblay, Yannick Daoudène, J. David, D. Bandyayera
The Nemiscau subprovince is a metasedimentary rocks-dominated sequence of the eastern Archean Superior Province. Previous structural and metamorphic studies suggested that it was the result of subduction-related, accretionary and collisional tectonics with adjacent plutonic terranes during the Kenorean orogeny. This study integrates various sets of structural, metamorphic and U-Pb geochronological data suggesting a long-lasting tectonometamorphic evolution between ca. 2843 and 2598 Ma. A non-uniformitarian tectonic model for the Archean more adequately accounts for synchronous vertical and horizontal tectonism as preserved in the Nemiscau basin.
{"title":"Structural evolution and U-Pb geochronology of the metasedimentary Nemiscau subprovince, Canada: implications for Archean tectonics in the Superior Province","authors":"Rocio Pedreira Perez, A. Tremblay, Yannick Daoudène, J. David, D. Bandyayera","doi":"10.1139/cjes-2022-0054","DOIUrl":"https://doi.org/10.1139/cjes-2022-0054","url":null,"abstract":"The Nemiscau subprovince is a metasedimentary rocks-dominated sequence of the eastern Archean Superior Province. Previous structural and metamorphic studies suggested that it was the result of subduction-related, accretionary and collisional tectonics with adjacent plutonic terranes during the Kenorean orogeny. This study integrates various sets of structural, metamorphic and U-Pb geochronological data suggesting a long-lasting tectonometamorphic evolution between ca. 2843 and 2598 Ma. A non-uniformitarian tectonic model for the Archean more adequately accounts for synchronous vertical and horizontal tectonism as preserved in the Nemiscau basin.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87328412","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 Cretaceous Western Interior Basin reflects the interplay between the North American craton and allochthonous terranes to the west. We divide the basinal stratigraphy into three successions, Aptian-Albian, Cenomanian-Turonian, and Santonian-Maastrichtian, each related to periods of deformation in the adjacent fold-thrust belt. Here we focus on the Cenomanian-Turonian succession, where progressive west to east uplift and fluvial incision of older Aptian-Albian sedimentary rocks (Cedar Mtn-San Pitch-Thermopolis-Skull Creek-Mannville) are interpreted as a migrating forebulge. Uplift was underway at 103 Ma in the west (Paddy-Blackleaf-Muddy sandstones) and propagated eastward throughout the trough by 99.5 Ma (Viking-Bow Island-Newcastle sandstones). The incised fluvial valleys were subsequently filled by swampy and shallow marine facies, then overlain by dark, marine Neogastroplites-bearing shale and associated bentonites of the 100-97.5 Ma Shell Creek-Mowry-Slater River-Goodrich-Shaftesbury-Westgate shales. The shales are characterized by a distinctive condensed horizon with abundant fish scales, teeth, and bones. They are interpreted as outer-trench slope deposits, with the overlying anoxic horizon representing a starved isochronous unit formed atop the slope deposits. The starved horizon is overlain by prodeltaic muddy clinoforms of easterly migrating clastic wedges (Trevor-Dunvegan-Frontier-Cintura-Mexcala) that can be traced 800 km atop the fish-scale hash and contain hinterland-derived 99-90 Ma detrital zircons. Although the Western Interior Basin has long been considered a retro-arc trough, the overall succession instead suggests that the Cretaceous-Turonian part represents a collisional foredeep created during the ~100 Ma collision between the arc-bearing Peninsular Ranges composite terrane and North America. The accretion brought tyrannosaurids, pachycephalosaurs, snakes and marsupials to North America.
白垩纪西部内陆盆地反映了北美克拉通与西部异域地体的相互作用。将盆地地层划分为阿普梯—阿尔梯、塞诺曼梯—图尔梯和圣东梯—马斯特里赫特3个序列，每个序列与相邻褶皱冲断带的变形期有关。这里我们关注的是Cenomanian-Turonian演替，其中较老的Aptian-Albian沉积岩(Cedar mtnn - san Pitch-Thermopolis-Skull Creek-Mannville)的西向东递进隆起和河流切割被解释为迁移前隆起。西部103ma (paddy - blackleafy - muddy砂岩)抬升，东部99.5 Ma (Viking-Bow Island-Newcastle砂岩)抬升。切割的河流山谷随后被沼泽和浅海相填满，然后被100-97.5 Ma的贝壳溪-莫里-斯莱特河-古德里奇-沙夫茨伯里-韦斯特盖特页岩的暗色海相新胃长岩页岩和伴生的斑长岩覆盖。页岩的特点是一个独特的浓缩层，有丰富的鱼鳞、牙齿和骨头。它们被解释为沟外斜坡沉积物，上覆的缺氧层代表在斜坡沉积物上形成的饥饿等时单元。贫水层上覆盖着前三角洲泥质斜形，由东移的碎屑楔块(特雷弗-邓维根-前沿-辛图拉-梅卡拉)组成，在鱼鳞砾岩顶部可追溯800公里，含有来自内陆的99-90 Ma碎屑锆石。尽管西部内陆盆地长期以来一直被认为是一个弧后槽，但整体序列表明，白垩纪- turonian部分是在含弧的半岛山脉复合地体与北美碰撞~100 Ma期间形成的碰撞前深。这次增生把暴龙、厚头龙、蛇和有袋动物带到了北美。
{"title":"The mid-Cretaceous Peninsular Ranges orogeny: a new slant on Cordilleran tectonics? III: The orogenic foredeep","authors":"R. Hildebrand, Bhattacharya J., J. Whalen","doi":"10.1139/cjes-2022-0089","DOIUrl":"https://doi.org/10.1139/cjes-2022-0089","url":null,"abstract":"The Cretaceous Western Interior Basin reflects the interplay between the North American craton and allochthonous terranes to the west. We divide the basinal stratigraphy into three successions, Aptian-Albian, Cenomanian-Turonian, and Santonian-Maastrichtian, each related to periods of deformation in the adjacent fold-thrust belt. Here we focus on the Cenomanian-Turonian succession, where progressive west to east uplift and fluvial incision of older Aptian-Albian sedimentary rocks (Cedar Mtn-San Pitch-Thermopolis-Skull Creek-Mannville) are interpreted as a migrating forebulge. Uplift was underway at 103 Ma in the west (Paddy-Blackleaf-Muddy sandstones) and propagated eastward throughout the trough by 99.5 Ma (Viking-Bow Island-Newcastle sandstones). The incised fluvial valleys were subsequently filled by swampy and shallow marine facies, then overlain by dark, marine Neogastroplites-bearing shale and associated bentonites of the 100-97.5 Ma Shell Creek-Mowry-Slater River-Goodrich-Shaftesbury-Westgate shales. The shales are characterized by a distinctive condensed horizon with abundant fish scales, teeth, and bones. They are interpreted as outer-trench slope deposits, with the overlying anoxic horizon representing a starved isochronous unit formed atop the slope deposits. The starved horizon is overlain by prodeltaic muddy clinoforms of easterly migrating clastic wedges (Trevor-Dunvegan-Frontier-Cintura-Mexcala) that can be traced 800 km atop the fish-scale hash and contain hinterland-derived 99-90 Ma detrital zircons. Although the Western Interior Basin has long been considered a retro-arc trough, the overall succession instead suggests that the Cretaceous-Turonian part represents a collisional foredeep created during the ~100 Ma collision between the arc-bearing Peninsular Ranges composite terrane and North America. The accretion brought tyrannosaurids, pachycephalosaurs, snakes and marsupials to North America.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"52 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85417481","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}
Quantitatively determining the amount of chemical weathering within sedimentary rocks (and weathering profiles) took a major step forward with the creation of the chemical index of alteration (CIA) forty years ago. The CIA relates the proportion of immobile aluminum to the mobile cations calcium, sodium, and potassium and is grounded in empirical and modeled geochemical data for mineral reactions that occur during hydrolysis. However, the CIA should be applied cautiously because it is a one-dimensional value that in the most complex situations, as with clastic sedimentary rocks, homogenizes the compositional inputs of source, weathering, sorting, and diagenesis. Subsequently developed two-dimensional ternary diagrams (Al2O3–CaO*+Na2O–K2O; Al2O3–CaO*+Na2O+K2O–FeO+MgO) permitted the capacity to explore mineralogical-geochemical pathways in data sets that may separate those inputs, but interpreting the ternary diagrams may be complicated because they differentiate and group certain elements. Here we develop a three-dimensional tetrahedral diagram (Al2O3–CaO*+Na2O–K2O–FeO+MgO, A-CN-K-FM) that incorporates the same critical elements and permits the simultaneous assessment of felsic and mafic rocks and minerals on the same diagram, while retaining the ability to separate plagioclase from alkali feldspar and monitor post-depositional potassium changes. Using the tetrahedral plot, we show that both the CIA value and positions on the 2D ternary diagrams can generate potentially misleading interpretations without properly budgeting the ferromagnesian components in parallel. We first show how the tetrahedron works, then use it with numerous previously published examples to identify how the competing mafic and felsic inputs shape the composition of source rocks, weathering profiles, actively transporting sediment, paleosols, and sedimentary rocks in sedimentary petrogenesis.
40年前，随着化学蚀变指数(CIA)的建立，定量确定沉积岩中化学风化作用(和风化剖面)的数量迈出了重要的一步。CIA将不动铝的比例与可动阳离子钙、钠和钾联系起来，并以水解过程中发生的矿物反应的经验和模拟地球化学数据为基础。然而，CIA应谨慎应用，因为它是一个一维值，在最复杂的情况下，如碎屑沉积岩，均质化了物源、风化、分选和成岩作用的成分输入。随后建立了二维三元图(Al2O3-CaO *+ Na2O-K2O;Al2O3-CaO *+Na2O+ K2O-FeO +MgO)允许在可能分离这些输入的数据集中探索矿物-地球化学途径的能力，但解释三元图可能很复杂，因为它们区分和分组某些元素。在这里，我们建立了一个三维四面体图(Al2O3-CaO *+ na20 - k20 - feo +MgO, a - cn - k - fm)，它包含了相同的关键元素，并允许在同一图上同时评估长英质和基性岩石和矿物，同时保留了将斜长石与碱长石分离并监测沉积后钾变化的能力。利用四面体图，我们发现在二维三元图上的CIA值和位置都可能产生潜在的误导性解释，而没有适当地并行预算氧化铁成分。我们首先展示了四面体是如何工作的，然后用它与许多先前发表的例子来确定相互竞争的基性和长英质输入如何塑造烃源岩的组成，风化剖面，在沉积岩石成因中积极运输沉积物，古土壤和沉积岩。
{"title":"Petrogenesis of siliciclastic sediments and sedimentary rocks explored in three-dimensional Al2O3 – CaO*+Na2O – K2O – FeO+MgO (A-CN-K-FM) compositional space","authors":"C. Fedo, M. Babechuk","doi":"10.1139/cjes-2022-0051","DOIUrl":"https://doi.org/10.1139/cjes-2022-0051","url":null,"abstract":"Quantitatively determining the amount of chemical weathering within sedimentary rocks (and weathering profiles) took a major step forward with the creation of the chemical index of alteration (CIA) forty years ago. The CIA relates the proportion of immobile aluminum to the mobile cations calcium, sodium, and potassium and is grounded in empirical and modeled geochemical data for mineral reactions that occur during hydrolysis. However, the CIA should be applied cautiously because it is a one-dimensional value that in the most complex situations, as with clastic sedimentary rocks, homogenizes the compositional inputs of source, weathering, sorting, and diagenesis. Subsequently developed two-dimensional ternary diagrams (Al2O3–CaO*+Na2O–K2O; Al2O3–CaO*+Na2O+K2O–FeO+MgO) permitted the capacity to explore mineralogical-geochemical pathways in data sets that may separate those inputs, but interpreting the ternary diagrams may be complicated because they differentiate and group certain elements. Here we develop a three-dimensional tetrahedral diagram (Al2O3–CaO*+Na2O–K2O–FeO+MgO, A-CN-K-FM) that incorporates the same critical elements and permits the simultaneous assessment of felsic and mafic rocks and minerals on the same diagram, while retaining the ability to separate plagioclase from alkali feldspar and monitor post-depositional potassium changes. Using the tetrahedral plot, we show that both the CIA value and positions on the 2D ternary diagrams can generate potentially misleading interpretations without properly budgeting the ferromagnesian components in parallel. We first show how the tetrahedron works, then use it with numerous previously published examples to identify how the competing mafic and felsic inputs shape the composition of source rocks, weathering profiles, actively transporting sediment, paleosols, and sedimentary rocks in sedimentary petrogenesis.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"54 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82236105","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}
François Malenfant, D. Whalen, P. Fraser, D. van Proosdij
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 Northwest and Southeast zones. The average annual linear regression rate (LRR) rate during the 1950-2018 observation period was -3.8 m∙a-1. The end point rate (EPR) was calculated for six observation periods: 1950-1972, 1972-1985, 1985-2000, 2000-2018, 2013-2018. A mean EPR of -5.5 ± 0.7 m∙a-1 was calculated for the 2000-2018 period, and a maximum retreat rate of 46.7 ± 2.1 m∙a-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-1) compared to moraine deposits (2.7 m∙a-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.
{"title":"Rapid coastal erosion of ice-bonded deposits on Pelly Island, southeastern Beaufort Sea, Inuvialuit Settlement Region, western Canadian Arctic","authors":"François Malenfant, D. Whalen, P. Fraser, D. van Proosdij","doi":"10.1139/cjes-2021-0118","DOIUrl":"https://doi.org/10.1139/cjes-2021-0118","url":null,"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 Northwest and Southeast zones. The average annual linear regression rate (LRR) rate during the 1950-2018 observation period was -3.8 m∙a-1. The end point rate (EPR) was calculated for six observation periods: 1950-1972, 1972-1985, 1985-2000, 2000-2018, 2013-2018. A mean EPR of -5.5 ± 0.7 m∙a-1 was calculated for the 2000-2018 period, and a maximum retreat rate of 46.7 ± 2.1 m∙a-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-1) compared to moraine deposits (2.7 m∙a-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.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"38-40 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78293125","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}
Quaternary sediment in the Labrador Sea was derived from many proglacial sources in Greenland and eastern Canada. Understanding the spatial and temporal changes in sediment provenance provides information on ice extent and sediment dispersal patterns. Variations in mineral composition of sediment from late Quaternary cores has been determined by a whole pattern quantitative X-ray diffraction procedure. Mineral facies were extracted statistically by a supervised analysis of 90 samples from bedrock and ice-rafted clasts, which were then used to predict the most probable mineral facies in 1443 marine sediment samples. We used a non-parametric Classification Decision Tree (CDT) to validate that decision. Only 26% of the samples were misclassified in the CDT. The six facies identified consisted of four facies reflecting differences in the composition of Canadian and Greenland Precambrian igneous and metamorphic bedrock, a set of samples dominated by high wt%s of calcite and dolomite (detrital carbonate (DC) and Hudson Strait Heinrich (HS-H) events), and a “shale” facies. We isolated 284 sediments from the HS-H detrital carbonate facies and determined that they could be divided into four categories based on differences in their mineral proportions. These categories vary geographically, based on non-carbonate sediment supply during these events from Greenland, the Canadian Shield, the Appalachians and the outer continental shelf. In the Holocene of the Labrador Sea, dolomite is derived from Baffin Bay and abundance of calcite is influenced by both biogenic productivity and dissolution.
{"title":"Late Quaternary changes in sediment sources in the Labrador Sea","authors":"J. Andrews, D. Piper","doi":"10.1139/cjes-2022-0026","DOIUrl":"https://doi.org/10.1139/cjes-2022-0026","url":null,"abstract":"Quaternary sediment in the Labrador Sea was derived from many proglacial sources in Greenland and eastern Canada. Understanding the spatial and temporal changes in sediment provenance provides information on ice extent and sediment dispersal patterns. Variations in mineral composition of sediment from late Quaternary cores has been determined by a whole pattern quantitative X-ray diffraction procedure. Mineral facies were extracted statistically by a supervised analysis of 90 samples from bedrock and ice-rafted clasts, which were then used to predict the most probable mineral facies in 1443 marine sediment samples. We used a non-parametric Classification Decision Tree (CDT) to validate that decision. Only 26% of the samples were misclassified in the CDT. The six facies identified consisted of four facies reflecting differences in the composition of Canadian and Greenland Precambrian igneous and metamorphic bedrock, a set of samples dominated by high wt%s of calcite and dolomite (detrital carbonate (DC) and Hudson Strait Heinrich (HS-H) events), and a “shale” facies. We isolated 284 sediments from the HS-H detrital carbonate facies and determined that they could be divided into four categories based on differences in their mineral proportions. These categories vary geographically, based on non-carbonate sediment supply during these events from Greenland, the Canadian Shield, the Appalachians and the outer continental shelf. In the Holocene of the Labrador Sea, dolomite is derived from Baffin Bay and abundance of calcite is influenced by both biogenic productivity and dissolution.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"17 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88229782","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}
Abstract The Halifax County complex (HCC) is a meta-ultramafic/metamafic body that crops out along the easternmost exposed part of the Carolina superterrane in northeastern North Carolina. Petrographic and mineral chemistry studies were undertaken to place some constraints on the evolution of the HCC. HCC amphiboles are zoned, with hornblende cores and actinolitic rims. Feldspar minerals span the whole plagioclase- and potassium-feldspar spectrum. Evolved olivines (Fo69-75) are primary, and pyroxenes plot in the enstatite, pigeonite, augite and diopside fields. Low TiO2 (<0.8 wt%) clinopyroxenes and highly calcic plagioclases are consistent with origin of the HCC at an island-arc setting. Chlorites are characterized by wide variations in their Si atoms per formula unit but have restricted total Fe concentrations. Potassium feldspar in the HCC likely originated during adularization or potassification. Chlorite thermometry yields temperatures of formation of 241-300 oC. Application of hornblende-plagioclase thermometers yields average temperatures of 648 oC consistent with amphibolite facies conditions as well as greenschist facies conditions, at pressures of up to 6.5 kbars. Clinopyroxene and evolved olivine compositions are both consistent with an island arc origin for the HCC. Amphibolite facies metamorphisms recorded by HCC rocks likely represent metamorphism of the HCC during arc-arc terrane collision, whereas greenschist metamorphism is interpreted to record the temperatures of thrusting of the HCC onto its present location at pressures of <3 kbars in Alleghanian times during the final assembly of the Appalachians. Results reported here have implications for the origin of comparable metamorphosed mafic-ultramafic rocks encountered along ancient orogenic belts worldwide.
{"title":"Petrology of the Halifax County complex, North Carolina, Southern Appalachians: constraints from petrography, mineral chemistry, and geothermobarometry","authors":"J. Chaumba","doi":"10.1139/cjes-2022-0037","DOIUrl":"https://doi.org/10.1139/cjes-2022-0037","url":null,"abstract":"Abstract The Halifax County complex (HCC) is a meta-ultramafic/metamafic body that crops out along the easternmost exposed part of the Carolina superterrane in northeastern North Carolina. Petrographic and mineral chemistry studies were undertaken to place some constraints on the evolution of the HCC. HCC amphiboles are zoned, with hornblende cores and actinolitic rims. Feldspar minerals span the whole plagioclase- and potassium-feldspar spectrum. Evolved olivines (Fo69-75) are primary, and pyroxenes plot in the enstatite, pigeonite, augite and diopside fields. Low TiO2 (<0.8 wt%) clinopyroxenes and highly calcic plagioclases are consistent with origin of the HCC at an island-arc setting. Chlorites are characterized by wide variations in their Si atoms per formula unit but have restricted total Fe concentrations. Potassium feldspar in the HCC likely originated during adularization or potassification. Chlorite thermometry yields temperatures of formation of 241-300 oC. Application of hornblende-plagioclase thermometers yields average temperatures of 648 oC consistent with amphibolite facies conditions as well as greenschist facies conditions, at pressures of up to 6.5 kbars. Clinopyroxene and evolved olivine compositions are both consistent with an island arc origin for the HCC. Amphibolite facies metamorphisms recorded by HCC rocks likely represent metamorphism of the HCC during arc-arc terrane collision, whereas greenschist metamorphism is interpreted to record the temperatures of thrusting of the HCC onto its present location at pressures of <3 kbars in Alleghanian times during the final assembly of the Appalachians. Results reported here have implications for the origin of comparable metamorphosed mafic-ultramafic rocks encountered along ancient orogenic belts worldwide.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"323 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74346642","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}
Derek Drayson, A. Camacho, M. Sanborn-Barrie, D. Regis, K. Larson, Alix Osinchuk, S. Dufrane
The recently recognized Sanagak Lake shear zone (SLsz) is a 165 km long, southwest striking corridor of high-strain rocks that transects the southern portion of Boothia Peninsula, Nunavut. This zone records pervasive deformation (DSL1) at conditions of ~0.52 GPa and ~700°C, and localized deformation (DSL2) at ≥ 0.5 GPa and 300-500°C that preserve left lateral and right lateral senses of movement, respectively. Neocrystallized DSL1 titanite in a hornblende-bearing granodiorite yield an age of 1804 ± 6 Ma, interpreted to be the timing of DSL1. The timing of DSL2 is loosely bracketed by 40Ar/39Ar hornblende (1814 ± 3 Ma) and biotite (1743 ± 1 Ma) cooling ages since the deformation temperature falls between the estimated closure temperature of these minerals. Similar rock types and metamorphic conditions on either side of the shear zone rule out the SLsz as a terrane boundary. Rather, strain localization may have been triggered by thermal softening related to the emplacement of a northeast-trending belt of high-temperature granites south of the shear zone between 1840 and 1820 Ma. Deformation and metamorphism at ca. 1.81 Ga south of Boothia Peninsula and in the central Rae (Committee Bay belt) has been attributed to the Superior Province colliding with the southeastern margin of the Rae craton, such that the SLsz may too have formed in response to far-field stresses derived from this collision. The absence of ca. 1.81 Ga tectonic fabrics north of the shear zone, indicates that the SLsz marks the northwestern extent of mid-crustal, Trans-Hudson related tectonometamorphism.
{"title":"Deformation history and tectonic significance of the Sanagak Lake shear zone, Boothia Peninsula, Nunavut","authors":"Derek Drayson, A. Camacho, M. Sanborn-Barrie, D. Regis, K. Larson, Alix Osinchuk, S. Dufrane","doi":"10.1139/cjes-2022-0046","DOIUrl":"https://doi.org/10.1139/cjes-2022-0046","url":null,"abstract":"The recently recognized Sanagak Lake shear zone (SLsz) is a 165 km long, southwest striking corridor of high-strain rocks that transects the southern portion of Boothia Peninsula, Nunavut. This zone records pervasive deformation (DSL1) at conditions of ~0.52 GPa and ~700°C, and localized deformation (DSL2) at ≥ 0.5 GPa and 300-500°C that preserve left lateral and right lateral senses of movement, respectively. Neocrystallized DSL1 titanite in a hornblende-bearing granodiorite yield an age of 1804 ± 6 Ma, interpreted to be the timing of DSL1. The timing of DSL2 is loosely bracketed by 40Ar/39Ar hornblende (1814 ± 3 Ma) and biotite (1743 ± 1 Ma) cooling ages since the deformation temperature falls between the estimated closure temperature of these minerals. Similar rock types and metamorphic conditions on either side of the shear zone rule out the SLsz as a terrane boundary. Rather, strain localization may have been triggered by thermal softening related to the emplacement of a northeast-trending belt of high-temperature granites south of the shear zone between 1840 and 1820 Ma. Deformation and metamorphism at ca. 1.81 Ga south of Boothia Peninsula and in the central Rae (Committee Bay belt) has been attributed to the Superior Province colliding with the southeastern margin of the Rae craton, such that the SLsz may too have formed in response to far-field stresses derived from this collision. The absence of ca. 1.81 Ga tectonic fabrics north of the shear zone, indicates that the SLsz marks the northwestern extent of mid-crustal, Trans-Hudson related tectonometamorphism.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"22 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89635487","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 Avalonia microcontinent has diagnostic terminal Ediacaran–Ordovician lithostratigraphy, depositional sequence architecture, and igneous activity that extends for 2000+ km and reflects epeirogeny related to the Avalonian transform fault. Avalonia records an abrupt early Middle Cambrian (late Wuliuan) change from green, purple, or light grey to overlying black, dark grey, and brown facies in platform and off-platform areas (Meguma, North Wales). This change within one trilobite zone marks onset of ca. 26 m.y. of shallow-marine anoxia/strong dysoxia lasting into the Ordovician with Hatch Hill OMZ onlap onto the shelf. A Bakken model (new, based on the middle Paleozoic Bakken Formation) is applied to shallow-shelf–shoreline organic-rich mud deposition. Erosion of greenish Avalonian depositional sequence (Ads) 7 was followed by Ads 8 tilting, volcanism, debris flows, and bentonite deposition on a cryptic unconformity in SE Newfoundland. The early Middle Cambrian age of the Ads 7–8 boundary is obscured by referring the lower Manuels River Formation and Cristallinium cambriense Zone to the younger Drumian Stage. Ads 8 has thin ashes in coterminous British and American Avalonia where erosion and subaerial exposure with caliche development preceded onlap of upper Middle or Upper Cambrian Ads 9 black muds and sands. The green–black change emphasizes Avalonian unity; it precludes multiple Avalonian “micro-terranes” or assigning parts of Avalonia to West Gondwana or “Ganderia” (the Little River, Brookville, and Bras d’Or “terranes” are part of the Avalonian marginal platform). Coeval green–black transitions and similar later Cambrian faunas show comparable paleoenvironments in Avalonia and Baltica.
阿瓦洛尼亚微大陆具有诊断性的埃迪卡拉—奥陶系晚期岩石地层、沉积层序构型和火成岩活动，延伸2000+ km，反映了与阿瓦洛尼亚转换断层有关的造陆作用。Avalonia记录了中寒武纪早期(五流晚期)台地和台地外地区从绿色、紫色或浅灰色到覆盖的黑色、深灰色和棕色相的突变(北威尔士Meguma)。在一个三叶虫带内的这种变化标志着大约26英里的浅海缺氧/强缺氧的开始，这种缺氧持续到奥陶纪，并与Hatch Hill OMZ重叠到大陆架上。将以中古生代巴肯组为研究对象的新巴肯模型应用于浅海架-岸线富有机质泥质沉积。在纽芬兰东南部，绿色Avalonian沉积层序(Ads) 7的侵蚀之后是Ads 8的倾斜、火山作用、碎屑流和膨润土沉积。通过将下曼努埃尔河组和水晶寒武纪带与更年轻的德鲁米安阶段相比较，可以模糊ad7 - 8的中寒武纪早期。广告8在邻近的英国和美国阿瓦洛尼亚有薄薄的灰烬，在那里，侵蚀和地面暴露与石灰发育先于中上寒武纪或上寒武纪黑色泥浆和沙子的覆盖。绿黑色的变化强调了阿瓦洛尼亚的统一;它排除了多个阿瓦洛尼亚“微地体”或将阿瓦洛尼亚的部分地区划分为西冈瓦纳或“Ganderia”(小河，布鲁克维尔和布拉斯达尔“地体”是阿瓦洛尼亚边缘台地的一部分)。在阿瓦洛尼亚和波罗的海，同时期的绿黑过渡和类似的寒武纪晚期动物群显示出相似的古环境。
{"title":"Trans-Avalonian green–black boundary (early Middle Cambrian): transform fault-driven epeirogeny and onset of 26 m.y. of shallow marine anoxia in Avalonia (Rhode Island–Belgium) and Baltica","authors":"E. Landing, S. Westrop, G. Geyer","doi":"10.1139/cjes-2022-0065","DOIUrl":"https://doi.org/10.1139/cjes-2022-0065","url":null,"abstract":"The Avalonia microcontinent has diagnostic terminal Ediacaran–Ordovician lithostratigraphy, depositional sequence architecture, and igneous activity that extends for 2000+ km and reflects epeirogeny related to the Avalonian transform fault. Avalonia records an abrupt early Middle Cambrian (late Wuliuan) change from green, purple, or light grey to overlying black, dark grey, and brown facies in platform and off-platform areas (Meguma, North Wales). This change within one trilobite zone marks onset of ca. 26 m.y. of shallow-marine anoxia/strong dysoxia lasting into the Ordovician with Hatch Hill OMZ onlap onto the shelf. A Bakken model (new, based on the middle Paleozoic Bakken Formation) is applied to shallow-shelf–shoreline organic-rich mud deposition. Erosion of greenish Avalonian depositional sequence (Ads) 7 was followed by Ads 8 tilting, volcanism, debris flows, and bentonite deposition on a cryptic unconformity in SE Newfoundland. The early Middle Cambrian age of the Ads 7–8 boundary is obscured by referring the lower Manuels River Formation and Cristallinium cambriense Zone to the younger Drumian Stage. Ads 8 has thin ashes in coterminous British and American Avalonia where erosion and subaerial exposure with caliche development preceded onlap of upper Middle or Upper Cambrian Ads 9 black muds and sands. The green–black change emphasizes Avalonian unity; it precludes multiple Avalonian “micro-terranes” or assigning parts of Avalonia to West Gondwana or “Ganderia” (the Little River, Brookville, and Bras d’Or “terranes” are part of the Avalonian marginal platform). Coeval green–black transitions and similar later Cambrian faunas show comparable paleoenvironments in Avalonia and Baltica.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"23 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82517661","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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