Pub Date : 2016-12-15DOI: 10.12789/geocanj.2016.43.107
S. Karakis, B. Cameron, W. Kean
The viticultural history of Wisconsin started in the 1840s, with the very first vine plantings by Hungarian Agoston Haraszthy on the Wollersheim Winery property located in the Lake Wisconsin American Viticultural Area (AVA). This study examines the terroir of historic Wollersheim Winery, the only winery within the confines of the Lake Wisconsin AVA, to understand the interplay of environmental factors influencing the character and quality as well as the variability of Wollersheim wines. Soil texture, chemistry, and mineralogy in conjunction with precision viticulture tools such as electromagnetic induction and electrical resistivity tomography surveys, are utilized in the Wollersheim Winery terroir characterization and observation of spatially variable terroir at the vineyard scale. Establishing and comparing areas of variability at the plot level for two specific vineyard plots (Domaine Reserve and Lot 19) at Wollersheim Winery provides insight into the effects of soil properties and land characteristics on grape and wine production using precision viticulture tools. The viticultural future of Wisconsin looks quite favorable, as the number of wineries keeps rising to meet the demand for Wisconsin wine and local consumption. As climate change continues to affect the grape varieties cultivated across the world’s wine regions, more opportunities arise for Wisconsin to cultivate cool-climate European varieties, in addition to the American and French–American hybrid varieties currently dominating grape production in this glacially influenced wine region.RESUMEL'histoire viticole du Wisconsin a commence dans les annees 1840, avec les premieres plantations de vigne par le Hongrois Agoston Haraszthy sur la propriete du vignoble Wollersheim situe dans la region de l’American Viticultural Area (AVA) du lac Wisconsin. Cette etude porte sur le terroir historique du vignoble Wollersheim, le seul a l'interieur de l’AVA du lac Wisconsin, qui soit soumis a l'interaction des facteurs environnementaux qui influencent le caractere, la qualite et la variabilite des vins Wollersheim. La caracterisation et l’observation des variations spatiales du terroir a l’echelle du vignoble Wollersheim se font par l’etude de la texture du sol, sa chimie et sa mineralogie en conjonction avec des outils de viticulture de precision comme l'induction electromagnetique et la tomographie par resistivite electrique. En definissant des zones de variabilite au niveau de la parcelle et en les comparant pour deux parcelles de vignobles specifiques (domaine Reserve et lot 19) du vignoble Wollersheim on peut mieux comprendre les effets des proprietes du sol et des caracteristiques du paysage sur la production de raisin et de vin. Le nombre de vignoble augmentant pour repondre a la demande de vin du Wisconsin et a la demande locale, l'avenir viticole du Wisconsin semble assez prometteur. Comme le changement climatique continue d'influer sur la varietes des cepages cultives dans les regi
{"title":"Geology and Wine 14. Terroir of Historic Wollersheim Winery, Lake Wisconsin American Viticultural Area","authors":"S. Karakis, B. Cameron, W. Kean","doi":"10.12789/geocanj.2016.43.107","DOIUrl":"https://doi.org/10.12789/geocanj.2016.43.107","url":null,"abstract":"The viticultural history of Wisconsin started in the 1840s, with the very first vine plantings by Hungarian Agoston Haraszthy on the Wollersheim Winery property located in the Lake Wisconsin American Viticultural Area (AVA). This study examines the terroir of historic Wollersheim Winery, the only winery within the confines of the Lake Wisconsin AVA, to understand the interplay of environmental factors influencing the character and quality as well as the variability of Wollersheim wines. Soil texture, chemistry, and mineralogy in conjunction with precision viticulture tools such as electromagnetic induction and electrical resistivity tomography surveys, are utilized in the Wollersheim Winery terroir characterization and observation of spatially variable terroir at the vineyard scale. Establishing and comparing areas of variability at the plot level for two specific vineyard plots (Domaine Reserve and Lot 19) at Wollersheim Winery provides insight into the effects of soil properties and land characteristics on grape and wine production using precision viticulture tools. The viticultural future of Wisconsin looks quite favorable, as the number of wineries keeps rising to meet the demand for Wisconsin wine and local consumption. As climate change continues to affect the grape varieties cultivated across the world’s wine regions, more opportunities arise for Wisconsin to cultivate cool-climate European varieties, in addition to the American and French–American hybrid varieties currently dominating grape production in this glacially influenced wine region.RESUMEL'histoire viticole du Wisconsin a commence dans les annees 1840, avec les premieres plantations de vigne par le Hongrois Agoston Haraszthy sur la propriete du vignoble Wollersheim situe dans la region de l’American Viticultural Area (AVA) du lac Wisconsin. Cette etude porte sur le terroir historique du vignoble Wollersheim, le seul a l'interieur de l’AVA du lac Wisconsin, qui soit soumis a l'interaction des facteurs environnementaux qui influencent le caractere, la qualite et la variabilite des vins Wollersheim. La caracterisation et l’observation des variations spatiales du terroir a l’echelle du vignoble Wollersheim se font par l’etude de la texture du sol, sa chimie et sa mineralogie en conjonction avec des outils de viticulture de precision comme l'induction electromagnetique et la tomographie par resistivite electrique. En definissant des zones de variabilite au niveau de la parcelle et en les comparant pour deux parcelles de vignobles specifiques (domaine Reserve et lot 19) du vignoble Wollersheim on peut mieux comprendre les effets des proprietes du sol et des caracteristiques du paysage sur la production de raisin et de vin. Le nombre de vignoble augmentant pour repondre a la demande de vin du Wisconsin et a la demande locale, l'avenir viticole du Wisconsin semble assez prometteur. Comme le changement climatique continue d'influer sur la varietes des cepages cultives dans les regi","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"43 1","pages":"265-282"},"PeriodicalIF":0.0,"publicationDate":"2016-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66817673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-15DOI: 10.12789/GEOCANJ.2016.43.106
Victoria Yehl
{"title":"Commitment, Collaboration and Communication: The Backbones of Geoscience","authors":"Victoria Yehl","doi":"10.12789/GEOCANJ.2016.43.106","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2016.43.106","url":null,"abstract":"","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"43 1","pages":"227-230"},"PeriodicalIF":0.0,"publicationDate":"2016-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66817605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-15DOI: 10.12789/GEOCANJ.2016.43.109
H. Williams
Tuzo Wilson’s 1966 Nature paper entitled “Did the Atlantic close and then re-open?” is truly the major turning point in the history of ideas on the evolution of the Appalachian Orogen. For a hundred years, the Appalachian Orogen was the type geosyncline, and Appalachian evolution was viewed in fixist models of geosynclinal development. Contrasting faunal realms were always enigmatic and never properly explained by notions of land barriers. Equally enigmatic was the symmetry and two-sided nature of the Newfoundland cross-section that refuted the fixist idea that continents grew like trees by the outward addition of asymmetric peripheral rings. The Wilson Cycle of closing a proto-Atlantic Ocean, then re-opening the Atlantic Ocean provided an elegant and simple solution to these enigmas. Wilson realized that island arcs existed on the North American side of the proto-Atlantic, such as the present Notre Dame Subzone in Newfoundland, and that the major faunal boundary lay to the east of these volcanic rocks. He also realized that the early Paleozoic continents may have touched in the middle Ordovician, “...for thereafter the distinction between the Atlantic and Pacific faunal realms ceases to be marked.” One continent encroaching upon another in the middle and late Ordovician explained the former borderland concept of Charles Schuchert and Marshall Kay. Likewise, Kay’s island arcs were most in evidence during the early Ordovician, the time of major proto-Atlantic closing. Wilson also recognized irregularities in ocean closing, which occurs first at promontories, then at re-entrants, with resulting clastic wedges, and an overall change from early Paleozoic marine conditions to middle and late Paleozoic terrestrial conditions. The Taconic allochthons were also part of his ocean closing scenario. The proto-Atlantic was completely closed by the end of the Paleozoic, and major spreading of the Atlantic began in the Cretaceous. Wilson then went on to trace the former course of the proto-Atlantic along the length of the Appalachian–Caledonian chain from Spitsbergen to Florida. This is no small task. It is encouraging to see that the contemporary Newfoundland analysis supported his views, and that even Tuzo had trouble finding a suture along the New England segment of the system. Northwest Africa was accommodated with ease as a Hercynian orogenic belt, in some respects symmetrical to the southern Appalachians. An important corollary of the Wilson Cycle is that the assembly and eventual breakup of Pangaea must have been an event of major significance in world geology. This is certainly true in North America, where major orogenesis and accretion in the Cordilleran Orogen on the Pacific Margin corresponds to Atlantic opening. Since the 1966 Wilson paper, we have emerged from fixist geosynclinal models that were entrenched in the literature for 100 years. Still, the Appalachian Orogen is full of surprises and there are many secrets yet to be revealed. As so aptly
{"title":"Did the Atlantic close and then reopen?: A commentary","authors":"H. Williams","doi":"10.12789/GEOCANJ.2016.43.109","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2016.43.109","url":null,"abstract":"Tuzo Wilson’s 1966 Nature paper entitled “Did the Atlantic close and then re-open?” is truly the major turning point in the history of ideas on the evolution of the Appalachian Orogen. For a hundred years, the Appalachian Orogen was the type geosyncline, and Appalachian evolution was viewed in fixist models of geosynclinal development. Contrasting faunal realms were always enigmatic and never properly explained by notions of land barriers. Equally enigmatic was the symmetry and two-sided nature of the Newfoundland cross-section that refuted the fixist idea that continents grew like trees by the outward addition of asymmetric peripheral rings. The Wilson Cycle of closing a proto-Atlantic Ocean, then re-opening the Atlantic Ocean provided an elegant and simple solution to these enigmas. Wilson realized that island arcs existed on the North American side of the proto-Atlantic, such as the present Notre Dame Subzone in Newfoundland, and that the major faunal boundary lay to the east of these volcanic rocks. He also realized that the early Paleozoic continents may have touched in the middle Ordovician, “...for thereafter the distinction between the Atlantic and Pacific faunal realms ceases to be marked.” One continent encroaching upon another in the middle and late Ordovician explained the former borderland concept of Charles Schuchert and Marshall Kay. Likewise, Kay’s island arcs were most in evidence during the early Ordovician, the time of major proto-Atlantic closing. Wilson also recognized irregularities in ocean closing, which occurs first at promontories, then at re-entrants, with resulting clastic wedges, and an overall change from early Paleozoic marine conditions to middle and late Paleozoic terrestrial conditions. The Taconic allochthons were also part of his ocean closing scenario. The proto-Atlantic was completely closed by the end of the Paleozoic, and major spreading of the Atlantic began in the Cretaceous. Wilson then went on to trace the former course of the proto-Atlantic along the length of the Appalachian–Caledonian chain from Spitsbergen to Florida. This is no small task. It is encouraging to see that the contemporary Newfoundland analysis supported his views, and that even Tuzo had trouble finding a suture along the New England segment of the system. Northwest Africa was accommodated with ease as a Hercynian orogenic belt, in some respects symmetrical to the southern Appalachians. An important corollary of the Wilson Cycle is that the assembly and eventual breakup of Pangaea must have been an event of major significance in world geology. This is certainly true in North America, where major orogenesis and accretion in the Cordilleran Orogen on the Pacific Margin corresponds to Atlantic opening. Since the 1966 Wilson paper, we have emerged from fixist geosynclinal models that were entrenched in the literature for 100 years. Still, the Appalachian Orogen is full of surprises and there are many secrets yet to be revealed. As so aptly","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"43 1","pages":"286"},"PeriodicalIF":0.0,"publicationDate":"2016-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66817692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-15DOI: 10.12789/GEOCANJ.2016.43.105
J. Murphy
Plate reconstructions indicate that if the Yellowstone plume existed prior to 50 Ma, then it would have been overlain by oceanic lithosphere located to the west of the North American plate (NAP). In the context of models supporting long-lived easterly directed subduction of oceanic lithosphere beneath the NAP, the Yellowstone plume would have been progressively overridden by the NAP continental margin since that time, the effects of which should be apparent in the geological record. The role of this ‘ancestral’ Yellowstone plume and its related buoyant swell in influencing the Late Mesozoic–Cenozoic tectonic evolution of the southwestern United States is reviewed in the light of recent field, analytical and geophysical data, constraints provided by more refined paleogeographic constructions, and by insights derived from recent geodynamic modeling of the interaction of a plume and a subduction zone. Geodynamic models suggesting that the ascent of plumes is either stalled or destroyed at subduction zones have focused attention on the role of gaps or tears in the subducted slab that permit the flow of plume material from the lower to the upper plate during subduction. These models imply that the ascent of plumes may be significantly deflected as plume material migrates from the lower to the upper plate, so that the connection between the hot spot track calculated from plate reconstructions and the manifestations of plume activity in the upper plate may be far more diffuse compared to the more precise relationships in the oceanic domain. Other geodynamic models support the hypothesis that subduction of oceanic plateau material beneath the NAP correlates with the generation of a flat slab, which has long been held to have been a defining characteristic of the Laramide orogeny in the western United States, the dominant Late Mesozoic–Early Cenozoic orogenic episode affecting the NAP. Over the last 20 years, a growing body of evidence from a variety of approaches suggests that a plume existed between 70 and 50 Ma within the oceanic realm close to the NAP margin in a similar location and with similar vigour to the modern Yellowstone hot spot. If so, interaction of this plume with the margin would have been preceded by that of its buoyant swell and related oceanic plateau, a scenario which could have generated the flat slab subduction that characterizes the Laramide orogeny. Unless this plume was destroyed by subduction, it would have gone into an incubation period when it was overridden by the North American margin. During this incubation period, plume material could have migrated into the upper plate via slab windows or tears or around the lateral margins of the slab, in a manner consistent with recent laboratory models. The resulting magmatic activity may be located at considerable distance from the calculated hot spot track. The current distribution of plumes and their buoyant swells suggests that their interaction with subduction zones should
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Pub Date : 2016-12-15DOI: 10.12789/GEOCANJ.2016.43.108
J. Dewey
{"title":"Tuzo Wilson: An Appreciation on the 50th Anniversary of his 1966 Paper","authors":"J. Dewey","doi":"10.12789/GEOCANJ.2016.43.108","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2016.43.108","url":null,"abstract":"","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"43 1","pages":"283-285"},"PeriodicalIF":0.0,"publicationDate":"2016-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66817680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-15DOI: 10.12789/GEOCANJ.2016.43.110
D. Kellett, L. Godin
BACK TO WHERE IT BEGAN The Department of Geological Sciences and Geological Engineering of Queen’s University, in Kingston, Ontario, will host the 2017 Annual meeting of the GAC–MAC. The meeting will coincide with the 175 anniversary of the founding of the Geological Survey of Canada, which was established by the legislature of the Province of Canada in 1842, in Kingston, and with Canada’s 150 anniversary celebrations. The local geology surrounding Kingston, commonly called the Limestone City, does not disappoint and multiple field trips associated with the meeting will take advantage of its unique location. Kingston is located at the eastern end of Lake Ontario, where the St. Lawrence River begins, draining the waters of the Great Lakes into the Gulf of St. Lawrence. The transition from lake to river occurs east of Kingston Harbour, where the nearly flat-lying Early Paleozoic limestone, rimming the eastern Lake Ontario basin, border against a NW-SE trending, low ridge of Grenvillian Precambrian basement rocks, locally known as the Frontenac Arch, which connects the southeastern Ontario part of the Canadian Shield with the Adirondack Massif of northern New York State. The crystalline basement rocks form a resistant ridge over which the St. Lawrence River flows northeastward from Lake Ontario, creating the ‘Thousand Islands,’ a well-known tourist and cottage region along the international border that now also includes a National Park. The 2017 Kingston GAC–MAC meeting will provide seven field trip opportunities that span from Proterozoic geology to the present, and cover a wide range of Earth Sciences sub-disciplines, from geomorphology to hydrology, from Quaternary geology to metallogeny, and from tectonics to sedimentology. Trips range in length from one to five days, as homegrown as a day trip touring the local geology highlights of Kingston’s environs, and as far-afield as a five day transect traversing the accreted terranes of the Newfoundland Appalachians. The one-day ‘Bedrock to Beaches’ field trip will take participants from Kingston to Prince Edward County and back. Along the way, participants will track one billion years of evolution of the Kingston region. They will contemplate metasedimentary rocks that were heated, squeezed, and intruded by granite ca. 1170 million years ago, sandstone deposited by rivers and wind ca. 490 million years ago, limestone and shale deposited in tropical seawater ca. 455 million years ago, faults that displaced the limestone perhaps 176 million years ago, drumlins shaped by a continental ice-sheet about 20,000 years ago, a shoreline created by a giant proglacial lake ca. 13,200 years ago, and a thin soil full of frost-heaved limestone nodules that nowadays nourishes many of the best vineyards in ‘the County.’ Another one-day trip will explore local shallow neritic marine carbonate rocks on a tropical Ordovician Earth. Shallow water marine carbonate rocks are beautifully exposed in the Kingston area and many
{"title":"Kingston 2017: GAC–MAC Joint Annual Meeting Field Trips","authors":"D. Kellett, L. Godin","doi":"10.12789/GEOCANJ.2016.43.110","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2016.43.110","url":null,"abstract":"BACK TO WHERE IT BEGAN The Department of Geological Sciences and Geological Engineering of Queen’s University, in Kingston, Ontario, will host the 2017 Annual meeting of the GAC–MAC. The meeting will coincide with the 175 anniversary of the founding of the Geological Survey of Canada, which was established by the legislature of the Province of Canada in 1842, in Kingston, and with Canada’s 150 anniversary celebrations. The local geology surrounding Kingston, commonly called the Limestone City, does not disappoint and multiple field trips associated with the meeting will take advantage of its unique location. Kingston is located at the eastern end of Lake Ontario, where the St. Lawrence River begins, draining the waters of the Great Lakes into the Gulf of St. Lawrence. The transition from lake to river occurs east of Kingston Harbour, where the nearly flat-lying Early Paleozoic limestone, rimming the eastern Lake Ontario basin, border against a NW-SE trending, low ridge of Grenvillian Precambrian basement rocks, locally known as the Frontenac Arch, which connects the southeastern Ontario part of the Canadian Shield with the Adirondack Massif of northern New York State. The crystalline basement rocks form a resistant ridge over which the St. Lawrence River flows northeastward from Lake Ontario, creating the ‘Thousand Islands,’ a well-known tourist and cottage region along the international border that now also includes a National Park. The 2017 Kingston GAC–MAC meeting will provide seven field trip opportunities that span from Proterozoic geology to the present, and cover a wide range of Earth Sciences sub-disciplines, from geomorphology to hydrology, from Quaternary geology to metallogeny, and from tectonics to sedimentology. Trips range in length from one to five days, as homegrown as a day trip touring the local geology highlights of Kingston’s environs, and as far-afield as a five day transect traversing the accreted terranes of the Newfoundland Appalachians. The one-day ‘Bedrock to Beaches’ field trip will take participants from Kingston to Prince Edward County and back. Along the way, participants will track one billion years of evolution of the Kingston region. They will contemplate metasedimentary rocks that were heated, squeezed, and intruded by granite ca. 1170 million years ago, sandstone deposited by rivers and wind ca. 490 million years ago, limestone and shale deposited in tropical seawater ca. 455 million years ago, faults that displaced the limestone perhaps 176 million years ago, drumlins shaped by a continental ice-sheet about 20,000 years ago, a shoreline created by a giant proglacial lake ca. 13,200 years ago, and a thin soil full of frost-heaved limestone nodules that nowadays nourishes many of the best vineyards in ‘the County.’ Another one-day trip will explore local shallow neritic marine carbonate rocks on a tropical Ordovician Earth. Shallow water marine carbonate rocks are beautifully exposed in the Kingston area and many","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"43 1","pages":"287-289"},"PeriodicalIF":0.0,"publicationDate":"2016-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66817764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-15DOI: 10.12789/GEOCANJ.2016.43.112
T. Christie
{"title":"The Metallogeny of Lode Gold Deposits: A Syngenetic Perspective","authors":"T. Christie","doi":"10.12789/GEOCANJ.2016.43.112","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2016.43.112","url":null,"abstract":"","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"43 1","pages":"291-293"},"PeriodicalIF":0.0,"publicationDate":"2016-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66817778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-09-30DOI: 10.12789/GEOCANJ.2016.43.102
C. Lewis
The Laurentian Great Lakes are a chain of five large water bodies and connecting rivers that constitute the headwaters of the St. Lawrence River. Collectively they form one of the largest reservoirs of surface freshwater on the planet with an aggregate volume of >22,000 km3. Early interpretations of the postglacial lake history implicitly assumed that the Great Lakes always overflowed their outlets. A study of Lake Winnipeg which concluded that lack of water in a dry climate had dried that lake for millennia led to re-evaluation of the Great Lakes water-level history. Using the empirical information of glacioisostatic rebound derived from 14C-dated and uptilted Great Lake paleo-shorelines, a method of computation was developed to test the paradigm of continuous lake overflow. The method evaluated site and outlet uplift independently, and lowlevel indicators such as submerged tree stumps rooted beneath the present Great Lakes were found to be lower than the lowestpossible corresponding basin outlet. Results confirmed the low-level, closed-basin hydrological status of the early Great Lakes. This status is consistent with paleoclimatic inferences of aridity during the early Holocene before establishment of the present patterns of atmospheric circulation which now bring adequate precipitation to maintain the overflowing lakes. In a sense, the early to middle Holocene phase of dry climate and low water levels is a natural experiment to illustrate the sensitivity of the Great Lakes to climate change in this era of global warming, should their climate shift to one much drier than present, or future major diversions of their waters be permitted.RESUMELes Grands Lacs Laurentiens sont une chaine de cinq grandes etendues d’eau connectees par des rivieres, constituant la source du Fleuve St-Laurent. Collectivement, ils forment un des plus grands reservoirs d’eau douce de surface de la planete avec un volume total de plus de >22,000 km3. Les premieresinterpretations de l’histoire postglaciaire des lacs supposaient implicitement que les Grands Lacs debordaient a leurs exutoires. Une etude du Lac Winnipeg, qui concluait qu’un deficit en eau durant un episode de climat aride avait desseche le lac pendant des millenaires dans le passe, a mene a la reevaluation de l’histoire du niveau de l’eau des Grands Lacs. En utilisant des donnees empiriques du relevement glacio-isostatique, derivees de littoral anciens sureleves dates au 14C, une methode de calcul a ete developpee pour tester le paradigme d’unedecharge lacustre continue. La methode a evalue le soulevement des sites et des exutoires independamment, et il a ete constate que les indicateurs de bas niveau tels que des troncs d’arbres submerges, enracines en dessous des Grands Lacs actuels, etaient en fait sous le niveau de l’exutoire correspondant le plus bas. Les resultats confirment le bas niveau et le statut de basin hydrologique ferme des Grand Lacs dans le passe. Ce statut est coherent avec des evidences pal
劳伦斯五大湖是由五个大型水体和连接的河流组成的，它们构成了圣劳伦斯河的源头。它们共同构成了地球上最大的地表淡水水库之一，总容量为22,000立方千米。对冰期后湖泊历史的早期解释隐含地假设五大湖总是溢出它们的出口。一项对温尼伯湖的研究得出结论，干燥气候下的缺水导致该湖干涸了数千年，这导致了对五大湖水位历史的重新评估。利用14c年代和上倾的大湖古岸线冰川均衡反弹的经验信息，建立了一种验证湖泊连续溢出范式的计算方法。该方法独立评估了站点和出水口的隆升，发现当前五大湖下方的淹没树桩等低水位指标低于相应的最低可能的盆地出水口。结果证实了五大湖早期的低水位、闭流域水文状态。这一状况与全新世早期干旱的古气候推断相一致，而现在的大气环流模式建立之前，降水充足，维持了溢流湖泊的存在。从某种意义上说，全新世早期到中期的干燥气候和低水位阶段是一个自然的实验，可以说明在这个全球变暖的时代，五大湖对气候变化的敏感性，如果它们的气候转向比现在更干燥，或者未来允许对其水域进行重大改道。Laurentiens grandes Laurentiens(圣罗兰大湖)是圣罗兰(saint - laurent)的源头之一。集合，地层和大型水库，加上地球表面的水，平均体积总积为22,000立方千米。《冰川后的历史》的首演诠释了《冰川后的历史》的隐含意义，《冰川后的历史》的隐含意义是《冰川后的历史》的隐含意义。在温尼伯湖，我们的结论是，我们的气候变化是由气候变化引起的，我们的研究是由气候变化引起的，我们的研究是由气候变化引起的，我们的研究是由气候变化引起的，我们的研究是由气候变化引起的，我们的研究是由气候变化引起的。利用与冰川均衡相关的经验，推导出14C以来的沿海古地层学特征，推导出了一种计算方法，并将其发展为非冰川湖泊的典型模型。该方法是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法，它的价值是一种独立的方法。这些研究结果证实了我们对大湖区流域水文学研究的新认识。Ce statut est相干用des证据paleoclimatiques d 'aridite盟亮相de l 'Holocene旅行车de l 'etablissement des模式循环atmospherique actuels, apportent des数量de降水一说盟maintien des浅滩lacustres。全新世的气候变化，全新世的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化，全新时代的气候变化。
{"title":"Geoscience Medallist 1. Understanding the Holocene Closed-Basin Phases (Lowstands) of the Laurentian Great Lakes and Their Significance","authors":"C. Lewis","doi":"10.12789/GEOCANJ.2016.43.102","DOIUrl":"https://doi.org/10.12789/GEOCANJ.2016.43.102","url":null,"abstract":"The Laurentian Great Lakes are a chain of five large water bodies and connecting rivers that constitute the headwaters of the St. Lawrence River. Collectively they form one of the largest reservoirs of surface freshwater on the planet with an aggregate volume of >22,000 km3. Early interpretations of the postglacial lake history implicitly assumed that the Great Lakes always overflowed their outlets. A study of Lake Winnipeg which concluded that lack of water in a dry climate had dried that lake for millennia led to re-evaluation of the Great Lakes water-level history. Using the empirical information of glacioisostatic rebound derived from 14C-dated and uptilted Great Lake paleo-shorelines, a method of computation was developed to test the paradigm of continuous lake overflow. The method evaluated site and outlet uplift independently, and lowlevel indicators such as submerged tree stumps rooted beneath the present Great Lakes were found to be lower than the lowestpossible corresponding basin outlet. Results confirmed the low-level, closed-basin hydrological status of the early Great Lakes. This status is consistent with paleoclimatic inferences of aridity during the early Holocene before establishment of the present patterns of atmospheric circulation which now bring adequate precipitation to maintain the overflowing lakes. In a sense, the early to middle Holocene phase of dry climate and low water levels is a natural experiment to illustrate the sensitivity of the Great Lakes to climate change in this era of global warming, should their climate shift to one much drier than present, or future major diversions of their waters be permitted.RESUMELes Grands Lacs Laurentiens sont une chaine de cinq grandes etendues d’eau connectees par des rivieres, constituant la source du Fleuve St-Laurent. Collectivement, ils forment un des plus grands reservoirs d’eau douce de surface de la planete avec un volume total de plus de >22,000 km3. Les premieresinterpretations de l’histoire postglaciaire des lacs supposaient implicitement que les Grands Lacs debordaient a leurs exutoires. Une etude du Lac Winnipeg, qui concluait qu’un deficit en eau durant un episode de climat aride avait desseche le lac pendant des millenaires dans le passe, a mene a la reevaluation de l’histoire du niveau de l’eau des Grands Lacs. En utilisant des donnees empiriques du relevement glacio-isostatique, derivees de littoral anciens sureleves dates au 14C, une methode de calcul a ete developpee pour tester le paradigme d’unedecharge lacustre continue. La methode a evalue le soulevement des sites et des exutoires independamment, et il a ete constate que les indicateurs de bas niveau tels que des troncs d’arbres submerges, enracines en dessous des Grands Lacs actuels, etaient en fait sous le niveau de l’exutoire correspondant le plus bas. Les resultats confirment le bas niveau et le statut de basin hydrologique ferme des Grand Lacs dans le passe. Ce statut est coherent avec des evidences pal","PeriodicalId":55106,"journal":{"name":"Geoscience Canada","volume":"43 1","pages":"179-197"},"PeriodicalIF":0.0,"publicationDate":"2016-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66817812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-09-30DOI: 10.12789/geocanj.2016.43.103
A. Kerr
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Pub Date : 2016-09-30DOI: 10.12789/GEOCANJ.2016.43.100
A. Schoonmaker, W. Kidd, Tristan J. Ashcroft
Foreland magmatism occurs in the lower plate during arc–continent or continent–continent collision, although it is uncommon. Ancient examples are recognized by a stratigraphic section into which mafic lavas and/or shallow sills are emplaced at a level at the top of a passive margin cover sequence, or within the overlying deeper water deposits that include mudrocks and flysch-type turbidites. Extensional structures associated with the emplacement of the volcanic rocks may develop slightly prior to or contemporaneous with the arrival of the approaching thrust front. We have selected twelve examples of magmatism in collisional forelands, modern and ancient, and have compared the tectonic associations of the magmatism with the magmatic geochemistry. Foreland magmatic settings fall into two strikingly distinct geochemical groups: a more enriched alkaline group (Rhine-type) and a more heterogeneous tholeiitic group (Maine-type) that may show traces of prior subduction processes. In the examples where the contemporaneous extensional structures are known, faults and basins develop parallel to the thrust front for the tholeiitic group and have oblique orientations, in several cases at a high angle to the thrust front, for the alkaline group. The geochemical results are quite sufficiently distinct to permit discrimination of these two foreland magmatic rock suites from each other in ancient examples where the foreland setting is clear from geological evidence. However, magmatic products of the same range of compositions can be generated in other tectonic environments (rifts, back-arc basins), so the geochemical characteristics alone are insufficient to identify a foreland basin setting. The alkaline Rhine-type group formed primarily in response to localized upwelling convective activity from the sub-asthenospheric mantle beneath the lower plate during collision while the tholeiitic Maine-type group formed primarily in response to melting of subcontinental asthenospheric mantle during extension of the lower plate by slab pull, and resulting lithospheric detachment. It is possible that there has been a long-term secular decrease in the occurrence of the Maine-type foreland magmatism since the early Proterozoic. RESUME Bien que peu frequent, il arrive qu’un magmatisme d’avantpays se produise dans la plaque inferieure durant une collision arc-continent ou continent-continent. Des exemples anciens ont ete decrits dans une coupe stratigraphique renfermant des laves mafiques et/ou des filons-couches au haut d’une sequence de couverture de marge passive, ou au sein de depots de plus grandes profondeurs comme des boues ou des turbidites de type flysch. Des structures d’etirement associees a la mise en place des roches volcaniques peuvent se developper un peu avant ou en meme temps que l’arrivee du front de chevauchement. Nous avons choisi douze exemples de magmatisme au sein d’avant-pays de collision, modernes et anciens, et nous avons compare les associations tect
在弧-陆或陆-陆碰撞过程中，下板块发生前陆岩浆活动，但并不常见。古代的例子可以通过地层剖面来识别，其中基性熔岩和/或浅层岩位于被动边缘覆盖层序的顶部，或位于包括泥岩和飞状浊积岩在内的上覆较深的水沉积物中。与火山岩侵位有关的伸展构造可能在接近的逆冲锋到来之前或同时发育。我们选取了12个现代和古代碰撞前陆的岩浆活动实例，并将岩浆活动的构造关联与岩浆地球化学进行了比较。前陆岩浆环境分为两个明显不同的地球化学组:一个更富碱性的组(莱茵型)和一个更不均匀的拉斑岩组(缅因型)，可能显示出先前俯冲过程的痕迹。在已知同生伸展构造的例子中，拉斑岩组的断层和盆地平行于逆冲前缘发育，碱性组的断层和盆地呈斜向，在某些情况下与逆冲前缘成大角度。地球化学结果非常明显，可以在地质证据清楚的前陆背景的古例中区分这两个前陆岩浆岩组。然而，在其他构造环境(裂谷、弧后盆地)中也可以产生相同成分范围的岩浆产物，因此仅凭地球化学特征不足以确定前陆盆地环境。碱性莱茵型群主要是由于碰撞过程中下板块下亚软流圈地幔的局部上升流对流活动而形成的，而拉斑缅因型群主要是由于下板块拉张过程中次大陆软流圈地幔的熔融导致岩石圈分离而形成的。早元古代以来，缅因型前陆岩浆活动可能长期减少。随着时间的不断深入，我们会发现岩浆活动频繁，岩浆活动频繁，岩浆活动频繁，岩浆活动频繁，岩浆活动频繁，岩浆活动频繁，岩浆活动频繁。例如，古生代沉积有双地层特征、双地层特征、双沉积特征、双沉积特征、双沉积特征、双沉积特征、双沉积特征、双沉积特征、双沉积特征、双浊积特征。“结构与结构”是一种“结构与结构”的结合，“结构与结构”是一种“结构与结构”，“结构与结构”是一种“结构与结构”，“结构与结构”是一种“结构与结构”。在现代和古代的碰撞中，在构造和地球化学的碰撞中，在构造和地球化学的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中，在构造和岩浆的碰撞中。先锋型岩浆构造可分为两组不同的地质构造:ⅰ组碱性+富集型(rhin型)、ⅰ组溶蚀+非均质型(maine型)和ⅰ组溶蚀+非均质型(maine型)。在这些例子中，我们可以看到构造的平行发展，我们可以看到构造的平行发展，我们可以看到构造的平行发展，我们可以看到构造的平行发展，我们可以看到构造的平行发展，我们可以看到构造的平行发展，我们可以看到构造的平行发展，我们可以看到构造的平行发展。结果geochimiques是说不同的倒permettre德高尚的两个套件de罗氏magmatiques在旧的这些例子或者配置d 'avant-pays est evidente de la sa学界不相上下。在此基础上，构造构造、构造构造(岩浆岩、盆地)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)、构造构造(岩浆岩、盆地-弧)等。Le groupe alcalin de type-Rhin年代是principalement形式的反应有一个activite d 'eruption de对流问题du披风sous-asthenospherique苏la斑块inferieure杜兰特拉碰撞,那么,Le groupe tholeiitique de type-Maine年代是印版principalement en la融合反应du披风sous-continental asthenospherique杜兰特l 'extension de la斑块inferieure etirement de la斑块,et Le detachement lithospherique decoule,。元古宙的代表，最可能的是，它将在缅因州的岩浆活动中长期持续下去。
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