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Seismic reflection stratigraphy of Lac Simard, Quebec, Canada: mass flow sedimentation in glacial Lake Barlow-Ojibway 加拿大魁北克Simard湖的地震反射地层学:Barlow-Ojibway冰川湖的物质流沉积
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-08 DOI: 10.1139/cjes-2023-0027
A.J. Yu, N. Eyles, M. Doughty, S. Bukhari
Lac Simard is a glaciated Shield basin situated in the Western Quebec Seismic Zone, an area of recurrent intraplate seismicity encompassing several densely populated areas. Previous works nearby have demonstrated that sediments preserved in lake basins hold the potential to serve as valuable archives of paleoseismicity. Correspondingly, a high-resolution chirp seismic reflection survey was conducted in Lac Simard, with results showing four acoustic facies (Af-1 to Af-4) within two stratigraphic successions (SS-1 and SS-2). The lowermost SS-1 is dominated by high-amplitude, laminated Af-2, interpreted as lateglacial varves deposited by suspension from primarily overflows and interflows during glacial lake ponding following deglaciation. Suspension deposition of Af-2 was episodically interrupted by stacked, chaotically bedded, weakly graded to opaque, channelled Af-3 interpreted as either debris flows or high-density turbidity currents. Presence of silt-clast breccias in Af-3 also suggests downslope collapse and reworking of varves from basin sidewalls. The overlying SS-2 is dominated by weakly reflective, laminated, high-frequency varved Af-4, suggesting a continuing seasonal control on postglacial sedimentation but with relative sediment starvation. A basin-wide erosional unconformity separating SS-1 and postglacial SS-2 records the abrupt drainage of glacial Lake Barlow-Ojibway around 8 000 years ago. Considering the history of lake floor disturbance in the region, mass flow facies Af-3 may be seismogenic, and thus, have regional tectonic significance. However, we cannot rule out the possibility of mass flows triggered by abrupt inflows of meltwater and sediment from a highly dynamic retreating Laurentide Ice Sheet prone to surging.
Lac Simard是一个冰川覆盖的盾状盆地,位于魁北克西部地震带,这是一个经常发生板内地震活动的地区,包括几个人口稠密的地区。之前的研究表明,保存在湖盆中的沉积物有可能成为古地震活动的宝贵档案。相应地,在Lac Simard进行了高分辨率啁啾地震反射测量,结果显示了两个地层序列(SS-1和SS-2)中的四个声学相(Af-1至Af-4)。最底层的SS-1以高振幅、层状的Af-2为主,被解释为冰川消融后冰湖积水期间主要溢流和间流悬浮沉积的冰川阀。Af-2的悬浮沉积偶尔会被堆积的、混乱的层状、弱分级到不透明的、通道化的Af-3打断,这被解释为泥石流或高密度浊度流。af3区粉屑角砾岩的存在也表明盆地侧壁的下坡塌陷和阀门改造。上覆的SS-2以弱反射、层状、高频变异的Af-4为主,表明冰川后沉积存在持续的季节控制,但存在相对的沉积物饥饿。分离SS-1和冰川后SS-2的一个盆地范围的侵蚀不整合记录了大约8000年前巴洛-奥吉布韦冰川湖的突然排水。结合该地区湖底扰动的历史,认为Af-3块流相可能为发震相,具有区域构造意义。然而,我们不能排除由高度动态退缩的劳伦泰德冰盖的融水和沉积物突然流入引发大量流动的可能性。
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引用次数: 0
Multiple forms of bioimmuration in a coral–crinoid–bryozoan association from the Middle Devonian Onondaga Formation of southeastern Ontario 安大略省东南部中泥盆世奥内达加组珊瑚-海百合-苔藓虫群落的多种生物免疫形式
4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-01 DOI: 10.1139/cjes-2023-0002
James Thomka, Lilian Gunderson
A large favositid tabulate coral colony from the Middle Devonian Edgecliff Member of the Onondaga Formation, collected from Port Colborne, southernmost Ontario, is described herein because of several noteworthy paleontological features preserved via overgrowth by the coral. The initial substratum colonized and subsequently overgrown by the favositid was a large solitary rugose coral, and outward growth resulted in overgrowth of multiple macrofossils, including relatively long portions of large-diameter (probably camerate) crinoid columns. The crinoid columns, which likely represent portions of robust, recumbent dististelar attachment structures, are otherwise known almost entirely from isolated columnals at the collection locality and similar high-energy biostromal lithofacies in the Edgecliff Member elsewhere. One of the crinoid columns is encrusted by a stenolaemate bryozoan containing several examples of a parasitic bioclaustration structure similar to Catellocaula. Hence, the composite coral–crinoid–bryozoan association contains two forms of bioimmuration: preservation of the relatively intact crinoid columns via overgrowth and eventual incorporation into the base of the tabulate coral and preservation of the outline of the bioclaustrated organism (potentially an ascidian tunicate) via embedment in the bryozoan. This specimen serves as a testament to the diversity of biotic interactions and preservational mechanisms that occurred in Paleozoic carbonate build-ups.
从安大略省最南端的科尔伯恩港收集的中泥盆世奥农达加组边缘崖成员的一个大型有利的表状珊瑚群,在这里被描述,因为珊瑚的过度生长保留了几个值得注意的古生物特征。最初的基质是一种巨大的孤独的褶皱珊瑚,随后被扶植,向外生长导致了多个大型化石的过度生长,包括大直径(可能是照相的)海百合柱的相对较长的部分。海百合柱可能代表了部分坚固的、平卧的双柱状附着结构,除此之外,几乎完全是从收集地点的孤立柱状和其他地方的Edgecliff成员的类似高能生物基质岩相中得知的。其中一根似海百合的柱体被一种狭窄的苔藓虫包裹着,其中包含几个类似于Catellocaula的寄生生物闭锁结构的例子。因此,珊瑚-海百合-苔藓虫的复合组合包含两种形式的生物免疫:通过过度生长保存相对完整的海百合柱,并最终合并到表状珊瑚的基部;通过嵌入苔藓虫保存生物螯合生物(可能是海鞘)的轮廓。该标本证明了古生代碳酸盐沉积中生物相互作用和保存机制的多样性。
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引用次数: 0
Paralava and clinker from the Canadian Arctic: A record of combustion metamorphism dating back to the late Miocene 加拿大北极地区的残岩和熟料:可追溯到中新世晚期的燃烧变质作用记录
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-05-26 DOI: 10.1139/cjes-2022-0142
L. Reinhardt, Solveig Estrada, R. Dohrmann, Nikola Koglin, K. Piepjohn, J. Galloway
Outcrops with conspicuous reddish to yellow-colored clinker, blackish paralava, and blends of both with a breccia-like appearance occur across the Canadian Arctic. We examined such rocks on Ellesmere Island, Banks Island, and the Mackenzie Delta area. These rocks are a product from natural combustion of bituminous shale and low-rank coal seams in Cretaceous and Paleogene host sedimentary rocks, respectively. The main mineral phases of clinker and silicate paralava samples are comprised of quartz + hematite ± feldspars ± cristobalite (or tridymite) ± cordierite–sekaninaite ± clinopyroxene ± sillimanite ± glass. Slag-like iron-oxide paralava (74–95 wt.% total Fe2O3) consisting of hematite ± magnetite ± clinopyroxene occur in Paleogene host sedimentary rocks rich in siderite concretions. The whole-rock geochemical composition of clinker and silicate paralava shows similarities for samples from the same outcrop. Regional and local specific elemental enrichments are mainly inherited from the sedimentary protoliths, which are characterized by volcanogenic input (Paleocene sedimentary rocks) or oxygen depleted depositional conditions (Upper Cretaceous bituminous sedimentary rocks). Spontaneous combustion could take place when the organic-rich sedimentary rocks become exposed to atmospheric oxygen. This process has occurred at least since the Messinian stage (Miocene) on Ellesmere Island (6.1 ± 0.2 Ma; 40Ar39Ar incremental heating dating on whole-rock paralava) and continues until now. An active combustion process on scree from a coal seam and clastic Eureka Sound Group sedimentary rocks was observed on Ellesmere Island.
露头带有明显的红色到黄色的熟料,带黑色的斜岩,以及两者的混合,具有角砾岩样的外观,出现在加拿大的北极地区。我们在埃尔斯米尔岛、班克斯岛和麦肯齐三角洲地区检查了这种岩石。这些岩石分别是白垩系和古近系寄主沉积岩中烟煤页岩和低煤阶煤层自然燃烧的产物。熟料和硅酸盐副矿渣样品的主要矿物相为石英+赤铁矿±长石±方英石(或黄璧石)±堇青石-绢云石±斜辉石±硅线石±玻璃。由赤铁矿±磁铁矿±斜辉石组成的渣状氧化铁副岩(74 ~ 95 wt.%总Fe2O3)产于富含菱铁矿结核的古近系寄主沉积岩中。同一露头样品的熟料和硅酸盐副滑石的全岩地球化学组成具有相似性。区域和局部特定元素富集主要继承自沉积原岩,其特征为火山源输入(古新世沉积岩)或缺氧沉积条件(上白垩统沥青沉积岩)。当富含有机物的沉积岩暴露在大气中的氧气中时,就会发生自燃。这一过程至少在埃尔斯米尔岛(6.1±0.2 Ma)的迈西尼亚阶段(中新世)开始发生;40Ar39Ar增量加热定年(全岩准斜岩),并持续至今。在埃尔斯米尔岛(Ellesmere Island)观察到煤层和碎屑尤里卡海峡群沉积岩在岩石上的活跃燃烧过程。
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引用次数: 0
Petrogenesis and tectonic significance of the Early Cretaceous Xizhelimu diorite in Keyouzhongqi, Inner Mongolia, China 内蒙古可游中旗早白垩世喜直里木闪长岩成因及构造意义
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-05-24 DOI: 10.1139/cjes-2022-0094
L. Tian, Deyou Sun, Jun Gou, Zhong-hua He, Duo Zhang
In order to determine the emplacement age, petrogenesis and geodynamic setting of the Xizhelimu diorite in Keyouzhongqi, Inner Mongolia of northeastern China, a detailed study of the petrography, geochronology and whole-rock geochemistry has been conducted. Geological and petrographic studies show that the Xizhelimu diorite is zoned: the central lithofacies zone is composed of medium-fine-grained monzodiorite and quartz diorite, and the marginal lithofacies zone is fine-grained diorite. The zircon U-Pb dating results show that the ages of the central and marginal facies are 133.5 ± 1.9 Ma and 133.4 ± 1.4 Ma, respectively. The whole-rock rare earth and trace element characteristics of the Xizhelimu diorite show an O-type adakite affinity. Combining the analysis of zircon Hf isotope composition (εHf(t) values of +7.7 to +10.0), the geochemical features of whole rock, and the results of partial melting modeling we suggest that the parental magma of the Xizhelimu diorite was derived from the partial melting of altered oceanic crust mixing with subducting sediments at shallow depths. In the early stage of Early Cretaceous, the Xizhelimu diorite originated in an extensional setting, mainly related to the closure of the western part of the Mongol–Okhotsk Ocean. The upwelling asthenospheric flow in this extensional setting induced partial melting of the paleo-oceanic crust to form the parental magma of the Xizhelimu diorite.
为确定内蒙古克酉中旗喜直里木闪长岩的侵位时代、岩石成因和地球动力学背景,对其岩石学、年代学和全岩地球化学进行了详细的研究。地质岩相学研究表明,喜直里木闪长岩具有分带性:中部岩相带为中细粒二黄长岩和石英闪长岩,边缘岩相带为细粒闪长岩。锆石U-Pb定年结果表明,中、边缘相年龄分别为133.5±1.9 Ma和133.4±1.4 Ma。西柘木闪长岩全岩稀土及微量元素特征表现为o型埃达奇岩亲和。结合锆石Hf同位素组成分析(εHf(t)值为+7.7 ~ +10.0)、全岩地球化学特征及部分熔融模拟结果,认为喜直里木闪长岩母岩浆来源于蚀变洋壳与浅部俯冲沉积物的部分熔融混合作用。早白垩世早期,喜泽里木闪长岩形成于拉张环境,主要与蒙古-鄂霍次克洋西部的闭合有关。伸展背景下的软流上涌导致古洋壳部分熔融,形成了西柘木闪长岩的母岩浆。
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引用次数: 0
Systematics and biostratigraphy of a new trilobite fauna collected from the subsurface Earlie Formation (Wuliuan Stage, Miaolingian Series, Cambrian) in southwestern Saskatchewan 萨斯喀彻温西南部寒武系苗岭系五流期地下早地层三叶虫新动物群的系统学与生物地层学
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-05-19 DOI: 10.1139/cjes-2023-0003
N. M. Handkamer, Andrei Ichaso, B. Pratt, M. Mángano, L. Buatois
Trilobites were recovered from four cores of the middle Cambrian Earlie Formation in southwestern Saskatchewan. Fossils occur in silty mudstone with interbedded siltstone and limestone, deposited in the inner detrital belt of the craton interior, under low-energy, subtidal conditions. Taxa identified include Kootenia dawsoni (Walcott 1889), Asaphiscus wheeleri Meek 1873, Blainia gregaria Walcott 1916b, Parehmania princeps Deiss 1939b, Ehmania weedi Resser 1935, Bolaspis labrosa (Walcott 1916a), and corynexochid gen. and sp. indet., indicating an age ranging from the lower to upper Altiocculus subzone of the Ehmaniella Zone, upper Wuliuan Stage. The upper Eldon and lower Pika formations located farther west in subsurface Alberta and the Rocky Mountains are considered to be age equivalent. Biostratigraphy confirms that strata overlying the Basal Sandstone Unit are diachronous and become progressively younger eastward. The trilobite fauna is lower in diversity relative to those in temporally equivalent units in the Rocky Mountains as well as the Great Basin, indicating that it may have experienced some environmental stressors, and that seafloor colonization was sporadic and opportunistic.
在萨斯喀彻温省西南部中寒武纪早地层的四个岩心中发现了三叶虫。化石产于粉砂质泥岩中,粉砂岩与灰岩互层,沉积于克拉通内部的内碎屑带,处于低能、潮下条件下。已鉴定的分类群包括Kootenia dawsoni (Walcott 1889)、Asaphiscus wheeleri Meek(1873)、Blainia gregaria Walcott 1916b、Parehmania princeps Deiss 1939b、Ehmania weedi Resser 1935、Bolaspis labrosa (Walcott 1916a)和corynexochid geni和sp. indet。,表明其年龄介于上五流期伊曼尼亚菌带的下至上高架亚带。上Eldon和下Pika地层位于阿尔伯塔地下和落基山脉以西,被认为是年龄相当的。生物地层学证实,覆盖在基底砂岩单元上的地层是历时性的,向东逐渐年轻化。与落基山脉和大盆地的三叶虫群落相比,三叶虫群落的多样性较低,这表明它可能经历了一些环境压力,并且海底殖民是零星的和机会性的。
{"title":"Systematics and biostratigraphy of a new trilobite fauna collected from the subsurface Earlie Formation (Wuliuan Stage, Miaolingian Series, Cambrian) in southwestern Saskatchewan","authors":"N. M. Handkamer, Andrei Ichaso, B. Pratt, M. Mángano, L. Buatois","doi":"10.1139/cjes-2023-0003","DOIUrl":"https://doi.org/10.1139/cjes-2023-0003","url":null,"abstract":"Trilobites were recovered from four cores of the middle Cambrian Earlie Formation in southwestern Saskatchewan. Fossils occur in silty mudstone with interbedded siltstone and limestone, deposited in the inner detrital belt of the craton interior, under low-energy, subtidal conditions. Taxa identified include Kootenia dawsoni (Walcott 1889), Asaphiscus wheeleri Meek 1873, Blainia gregaria Walcott 1916b, Parehmania princeps Deiss 1939b, Ehmania weedi Resser 1935, Bolaspis labrosa (Walcott 1916a), and corynexochid gen. and sp. indet., indicating an age ranging from the lower to upper Altiocculus subzone of the Ehmaniella Zone, upper Wuliuan Stage. The upper Eldon and lower Pika formations located farther west in subsurface Alberta and the Rocky Mountains are considered to be age equivalent. Biostratigraphy confirms that strata overlying the Basal Sandstone Unit are diachronous and become progressively younger eastward. The trilobite fauna is lower in diversity relative to those in temporally equivalent units in the Rocky Mountains as well as the Great Basin, indicating that it may have experienced some environmental stressors, and that seafloor colonization was sporadic and opportunistic.","PeriodicalId":9567,"journal":{"name":"Canadian Journal of Earth Sciences","volume":"15 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82021116","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}
引用次数: 0
Discussion: The Terreneuvian MacCodrum Brook section, Mira terrane, Cape Breton Island, Nova Scotia, Canada: age constraints from ash layers, organic-walled microfossils, and trace fossils 讨论:Terreneuvian MacCodrum Brook剖面,Mira terrane, Cape Breton Island, Nova Scotia, Canada:来自灰层,有机壁微化石和微量化石的年龄限制
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-05-19 DOI: 10.1139/cjes-2023-0031
E. Landing, G. Geyer
Exhaustive similarities in terminal Ediacaran–Ordovician cover sequences between tectonic inliers in the Appalachian–Caledonian (A–C) orogen define the Avalonian terrane from coastal northeast North America through southern Britain to Belgium. However, Barr et al. effectively block inclusion of the Mira belt (Mb) in Avalonia by masking a long-documented trans-Avalonian succession under locally defined lithostratigraphic names that prove to be confusing homonyms of themselves. Earlier revisions of Mira belt stratigraphy allow assignment of the Mira belt to a precise location in the Avalonian strike-slip regime—on the marginal–inner platform transition just as the northern Antigonish Highlands and southeast Burin Peninsula. The Mira belt is a tectonic inlier not a “terrane” in the A–C orogen.
阿巴拉契亚-加里多尼亚造山带(A-C)构造内层之间埃迪卡拉末期-奥陶系盖层序列的彻底相似性定义了从北美东北部沿海到英国南部到比利时的阿瓦洛尼亚地体。然而,Barr等人通过在当地定义的岩石地层名称下掩盖长期记录的跨阿瓦洛尼亚演替,有效地阻止了米拉带(Mb)在阿瓦洛尼亚的包裹体,这些名称被证明是混淆的同音异义词。早期对米拉带地层学的修正允许将米拉带精确地定位在阿瓦洛尼亚走滑体系的边缘-内台地过渡上,就像安提戈尼什高地北部和布林半岛东南部一样。米拉带是a - c造山带中的构造断层,而不是“地体”。
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引用次数: 2
Magnetotelluric imaging of the magmatic and geothermal systems beneath Mount Meager, southwestern Canada 加拿大西南部蒂尼山地下岩浆和地热系统的大地电磁成像
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-05-11 DOI: 10.1139/cjes-2022-0136
C. Hanneson, M. Unsworth
Magnetotelluric data were collected on and around the Mount Meager Volcanic Complex, an active volcanic complex with eruptions ~2,400 and ~24,300 years ago. 3-D inversion was used to create an electrical resistivity model to a depth > 20 km. The model is characterized by high resistivity (> 100 Ωm) in the upper 6-7 km, implying relatively dry, unaltered rock. Within this resistive layer, localized conductors are observed in the upper 2 km beneath Pylon Peak and Fish Creek, corresponding to low-permeability clay-rich layers, acting as caprocks to geothermal fluids below. Beneath the resistive upper crust, there is a large conductor at ~5-15 km below sea level with an average resistivity of ~3 Ωm. Laboratory experiments of melt resistivity and petrological data from erupted volcanic rocks were used to interpret the model. The magma body (deep conductor) is inferred to have a minimum volume of ~2×10^12 m^3 comprising ~18-32% dacitic-to-trachydacitic melt with ~6-8 wt% H2O at a temperature of ~800-900ºC. This is below the melt fraction of an eruptible magma body. Resolution tests suggest it might be regional in extent, not localized beneath Mount Meager. There are fluid pathways from the northern part of the magma body, up toward Mount Meager and nearby fumaroles. This model is a significant advancement from its predecessors, created 20-40 years ago, providing the first deep 3-D image of this volcanic system. Along with other geophysical and geological models of the Garibaldi Geothermal Energy Project, it will reduce the exploration risk associated with geothermal energy development.
大地电磁资料是在蒂尼火山复合体上及其周围收集的,蒂尼火山复合体是一个活火山复合体,大约在2400年至24300年前喷发。利用三维反演技术建立了深度> 20 km的电阻率模型。模型上部6 ~ 7 km具有高电阻率特征(> 100 Ωm),表明岩石相对干燥,未蚀变。在这个电阻层中,在Pylon Peak和Fish Creek下方2公里处观察到局部导体,对应于低渗透的富粘土层,充当地下地热流体的盖层。在具有电阻性的上地壳之下,在海平面以下~5 ~ 15 km处有一条大导体,平均电阻率为~3 Ωm。利用熔体电阻率实验和火山喷发岩石学资料对模型进行了解释。推断岩浆体(深部导体)的最小体积为~2×10^12 m^3,由~18-32%的英质-粗英质熔体和~6-8 wt%的H2O组成,温度为~800-900℃。这低于可喷发岩浆体的熔融部分。分辨率测试表明,它可能是区域性的,而不是蒂尼山下的局部区域。岩浆体北部有流体通道,流向蒂尼山和附近的喷气孔。这个模型与20-40年前创建的模型相比是一个重大的进步,它提供了这个火山系统的第一个深三维图像。与加里波第地热能项目的其他地球物理和地质模型一起,它将降低与地热能开发相关的勘探风险。
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引用次数: 0
Onshore–offshore correlation of central Lake Erie glacial deposits 伊利湖中部冰川沉积物的陆上-海上对比
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-05-11 DOI: 10.1139/cjes-2023-0017
M. Lewis, G. Cameron, P. Barnett, B. Todd
Dive observations, echogram transects, core sampling and a seismic profile revealed that the lake bed of north-central Lake Erie is an extensive terrace cut by storm waves and currents. The terrace is an erosional unconformity on which Late Wisconsinan (Port Bruce and Mackinaw) glacial units crop out. Beds of massive diamictons, and glaciolacustrine sediments containing parallel reflections, crop out alternately from west to east, resulting from an oscillatory ice retreat. These beds correlate with the Port Stanley Drift (Port Bruce phase) and Wentworth Drift (Mackinaw phase) exposed in nearby shore bluffs and onshore moraines. The Port Bruce glacier and earlier readvances formed ice tongues and ice shelves in the central basin. Diamicton layers, some with debris flows, constitute the Port Stanley Till (offshore units M and O). A glaciolacustrine unit N was deposited during Port Bruce glacier recessions. Glaciolacustrine unit P lies between Port Bruce unit O and the Mackinaw Wentworth Till, unit Q. A subsequent glaciolacustrine unit R overlaps unit Q. The onshore Galt and Moffat moraines, composed of Wentworth Till, correlate with ridges of the Norfolk moraine unit Q which extend across Lake Erie between the base of Long Point, Ontario, and Erie, Pennsylvania. The onshore Paris moraine appears to have been eroded on the wave-cut terrace and is evident offshore only near the south shore of Lake Erie. Laminated unit S, younger than unit R, occurs in the western part of central Erie basin, and correlates with overflow of Lake Algonquin from the Huron basin.
潜水观测、回声图样带、岩心取样和地震剖面显示,伊利湖中北部的湖床是一个被风暴波和水流切割的广阔梯田。阶地是威斯康辛州晚期(布鲁斯港和麦基诺港)冰川单元的侵蚀不整合面。由于振荡性的冰退缩,巨大的砾岩床和含有平行反射的冰湖沉积物从西到东交替出现。这些床与斯坦利港漂移(布鲁斯港阶段)和温特沃斯漂移(麦基诺阶段)相对应,暴露在附近的海岸悬崖和岸上冰碛上。布鲁斯港冰川和早期的冰川在中部盆地形成了冰舌和冰架。在布鲁斯港冰川衰退期沉积了一个冰川湖单元N,其中一些带有泥石流,构成了斯坦利港蒂尔(离岸单元M和O)。冰川湖单元P位于布鲁斯港单元O和麦基诺温特沃斯蒂尔单元Q之间,随后的冰川湖单元R与Q单元重叠。由温特沃斯蒂尔组成的陆上高尔特冰碛和莫法特冰碛与诺福克冰碛单元Q的山脊相关,后者从安大略省的长点基地延伸到宾夕法尼亚州的伊利湖。巴黎岸上的冰碛似乎已经在波浪切割的阶地上被侵蚀了,只有在伊利湖南岸附近才有明显的离岸。层状单元S比层状单元R更年轻,出现在伊利盆地中部西部,与休伦盆地的阿尔冈昆湖溢流有关。
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引用次数: 0
Crustal eduction and slab-failure magmatism in an Orosirian (2.05−1.80 Ga) post-collisional cratonic foredeep: geochronology of Seton volcanics and Compton laccoliths, Tu Cho (Great Slave Lake), NWT, Canada orosiian (2.05 ~ 1.80 Ga)碰撞后克拉通前深的地壳喷发和板块破裂岩浆作用:加拿大Tu Cho (Great Slave Lake) Seton火山和Compton泥质岩的年代学
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-05-01 DOI: 10.1139/cjes-2023-0011
P. Hoffman, F. Macdonald, S. Bowring, Ramezani JR Jahan, R. Buchwaldt, R. Hildebrand, J. Whalen
Three Orosirian basins and associated foreland thrust-fold belts are preserved on the margins of Slave craton. All three are related to orogenic belts where oceans opened and later closed uniting new crustal partners. Great Slave basin differs from Kilhigok and Coronation basins in ways that have defied explanation. It lacks a passive-margin sequence and hosts two discrete igneous suites, separated by large-scale thrusting, occurring well after the adjacent paleocean had closed. Here we report U-Pb zircon geochronology by CA-ID-TIMS for a member of each suite to constrain the age and origin of post-collisional thrusting. A widespread pulse of mainly phreatic alkaline volcanism, coeval with renewed foredeep flexure, occurred at 1889.0±0.7 Ma (2σ internal error). A quartz-monzodiorite body, one of a belt-parallel chain of laccoliths that postdate thrusting, was emplaced at 1866.9±0.9 Ma. These ages bracket renewed foredeep sedimentation and thrusting that telescoped major facies zones and was rooted within the basin. The older age is 70 and 30−60 Myr younger than collision in Thelon and Taltson orogen, respectively. We attribute post-collisional thrusting and foredeep subsidence to ‘eduction’—the upward and outward ejection of partly-subducted crust—and postulate that the top of the ejected wedge was a normal-sense detachment fault projecting beneath Nonacho basin. We infer that eduction was triggered by slab failure, producing alkaline volcanism, and ended with delamination and laccolith emplacement. Eduction was facilitated by tradewind–driven erosion. Delamination was enabled by crustal transfer to the educted wedge, reducing footwall buoyancy. Slab-failure and/or delamination removed the passive margin.
在奴克拉通边缘保存着3个奥陶纪盆地及其相关的前陆逆冲褶皱带。这三个都与造山带有关,在造山带中,海洋打开又关闭,形成了新的地壳伙伴。大奴隶盆地与Kilhigok和Coronation盆地的不同之处在于无法解释。它缺乏被动边缘层序,拥有两个离散的火成岩套,被大规模的逆冲分隔开,发生在邻近的古海洋关闭之后。本文利用CA-ID-TIMS对每组地层进行了U-Pb锆石年代学分析,以确定碰撞后逆冲作用的年龄和成因。在1889.0±0.7 Ma (2σ内误差)发生了广泛的以潜水碱性火山活动为主的脉冲,与前深挠曲的恢复同时发生。在1866.9±0.9 Ma的位置发现了一个石英-二黄长石体,它是逆冲运动后的带状平行链中的一个。这些时代包含了更新的前深沉积和冲断作用,这些沉积和冲断作用扩展了主要的相带,并扎根于盆地内部。在Thelon造山带和Taltson造山带,碰撞年龄分别比碰撞年龄小70和30 ~ 60 Myr。我们将碰撞后的逆冲和前深下沉归因于“喷出”——部分俯冲的地壳向上和向外喷出——并假设喷出的楔块顶部是一个正常意义上的滑脱断层,突出在诺纳乔盆地之下。我们推断,喷出是由板岩破坏引发的,产生碱性火山作用,并以脱层和泥质侵位结束。信风驱动的侵蚀促进了土壤的流失。地壳转移到排出的楔块,降低了下盘浮力,从而实现了分层。板坯破坏和/或分层消除了被动边缘。
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引用次数: 1
Petrogenesis and geochemical evidence from Early Jurassic intrusive rocks and their implications for subduction of the Paleo-Pacific Plate in the Yanbian area, Northeast China 延边地区早侏罗世侵入岩的岩石成因、地球化学证据及其对古太平洋板块俯冲作用的启示
IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-04-27 DOI: 10.1139/cjes-2022-0119
xinwen zhang, Jing‐gui Sun, Zhikai Xu, Yang Liu, Chuntao Zhao
Subduction of the Paleo-Pacific Plate plays a key role in the Early Jurassic magmatism evolution in the Yanbian area, Northeast China. In this paper, zircon U–Pb ages, whole-rock geochemical and Sr–Nd–Hf isotopic compositions are presented. The Early Jurassic gabbros, diorite enclaves, granodiorites and granites ages range from 183 to 189 Ma. They are characterized by enrichment in LILEs and depletion in HFSEs. The gabbros are classified as low- and medium-K tholeiitic, granodiorites and granites are high-K calc-alkaline I-type, and diorite enclaves are calc-alkaline transitional series. The gabbros have zircon εHf(t) values of +6.81 to +9.89, whole-rock 87Sr/86Sr(i) = 0.7043-0.7044 and εNd(t) from +2.72 to +2.80. The diorite enclaves have zircons with εHf(t) values of +8.26 to +12.80, whole-rock 87Sr/86Sr(i) = 0.7051 and εNd(t) from +0.96 to +1.09. The granodiorites and granites have zircon εHf(t) values of +7.59 to +12.87, whole-rock 87Sr/86Sr(i) = 0.7042-0.7066 and εNd(t) from +2.33 to +2.61. These data indicate that gabbroic magmas were derived from partial melting of a depleted mantle wedge metasomatized by subduction-related fluids. The basaltic magma underplated and heated the juvenile crust, whereas the granodiorites and granites might be the product of fractional crystallization of a mixture of basaltic and felsic magmas or derived from partial melting of the juvenile lower crust. Our data constrain the petrogenesis of these Early Jurassic intrusive rocks which are attributed to subduction of the Paleo-Pacific Plate beneath Eurasia continent in northeastern China.
古太平洋板块的俯冲作用在东北延边地区早侏罗世岩浆活动演化中起着关键作用。本文给出了锆石U-Pb年龄、全岩地球化学和Sr-Nd-Hf同位素组成。早侏罗世辉长岩、闪长岩包裹体、花岗闪长岩和花岗岩年龄为183 ~ 189 Ma。它们的特点是LILEs富集,HFSEs耗竭。辉长岩为低钾和中钾拉斑岩,花岗闪长岩和花岗岩为高钾钙碱性i型,闪长岩包体为钙碱性过渡系列。辉长岩锆石εHf(t)值为+6.81 ~ +9.89,全岩87Sr/86Sr(i)值为0.7043 ~ 0.7044,εNd(t)值为+2.72 ~ +2.80。闪长岩包体锆石εHf(t)值为+8.26 ~ +12.80,全岩87Sr/86Sr(i) = 0.7051, εNd(t)值为+0.96 ~ +1.09。花岗闪长岩和花岗岩锆石εHf(t)值为+7.59 ~ +12.87,全岩87Sr/86Sr(i)值为0.7042 ~ 0.7066,εNd(t)值为+2.33 ~ +2.61。这些资料表明,辉长岩岩浆来自于俯冲相关流体交代的衰竭地幔楔的部分熔融。玄武岩岩浆在幼期地壳下包裹并加热,而花岗闪长岩和花岗岩可能是玄武岩和长英质岩浆混合的分馏结晶产物,或来自幼期下地壳的部分熔融。我们的资料限制了中国东北早侏罗世侵入岩的岩石成因,这些侵入岩是由古太平洋板块俯冲到欧亚大陆之下造成的。
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引用次数: 0
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Canadian Journal of Earth Sciences
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