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1.
The results of our new paleomagnetic investigations on 21 sites in the Cévennes and Lure regions as well as previous studies demonstrate that all Mesozoic marly limestones of SE France exhibit similar paleomagnetic behavior with remagnetization disputed in age. The studied areas have the particularity to have been folded before (Late Eocene), the Alpine folding (Oligo–Miocene). Samples (201 marly limestones) dated from Lower Jurassic to Lower Cretaceous have been demagnetized by thermal treatment. They all present a well-defined component with a normal polarity which was mostly obtained between 200 and 350 °C. Numerous arguments lead from pretectonic to syntectonic widespread remagnetization related to orogenic fluid circulation affecting the whole basin. An Eocene age (between 35 and 40 Ma) is obtained for this remagnetization thanks both to the comparison of the average inclination of all regional paleomagnetic studies (+54.9°/−1.5°) with the expected paleomagnetic inclination and the syntectonic character of remagnetization. 相似文献
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黑龙江东部饶河境内的层状燧石是中生代完达山造山带蛇绿混杂岩的重要组成部分,这些层状燧石的构造意义成为人们关注的热点。对完达山造山带饶河三叠纪大佳河组层状燧石280余块定向手标本开展深入的古地磁研究,结果表明这些层状燧石遭受不同程度的重磁化,重磁化的时间推测为晚侏罗世中期—早白垩世之间。说明对黑龙江东部晚侏罗世—早白垩世存在太平洋板块俯冲的响应。本区重磁化的机制是太平洋板块向西俯冲导致的地体增生、拼贴过程中的造山带流体造成的区域性重磁化现象。 相似文献
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Sara Torres‐López Antonio M. Casas Juan José Villalaín Hamidou El Ouardi Bennacer Moussaid 《地学学报》2016,28(2):110-119
Palaeomagnetic data, and specifically remagnetizations, are used to constrain the geometric reconstruction at 100 Ma of three anticlines cored by gabbroic intrusions and Triassic shales in the Central High Atlas, Morocco. Previous palaeomagnetic results have revealed that the Mesozoic sediments of this region acquired a pervasive remagnetization at the end of the Early Cretaceous. The restoration of palaeomagnetic vectors to the remagnetization stage (100 Ma) allows us to determine the dip of the beds during this period and, thereby, to reconstruct structures during that time and determine the relative contributions of Mesozoic magmatic/diapiric uplift vs. Cenozoic compression to the present‐day dip. Our results indicate that three major anticlines in the Central High Atlas (Tasraft, Tassent and Tissila) were initiated to different degrees before the Late Cretaceous and were reactivated during Cenozoic compression to acquire their present‐day geometry. We also discuss the origin of these structures. 相似文献
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The paleomagnetic analysis of the Permo-Triassic redbeds outcropping in the western part of the Cantabric Chain and the small Mesozoic basin from the Asturias shows that these formations have a history of complex magnetization. Only a few sites did not experience the remagnetization processes and retained original directions. The most reliable results yield a paleomagnetic pole located at: lat. 49° N, long. 217° E (n = 11, 95 = 3.7°), which is suggested as reliable Permo-Triassic data for the Iberian plate. Two remagnetization phases are recognized: a moderate phase predating the folding gave rise to a first overprinting. It is connected with the distension which occurred in the Pyreneo-Cantabrian region during the upper Jurassic-lower Cretaceous. The main remagnetization phase which occurred after the folding is dated from the lower Tertiary, and can be related to the compression induced on the northern boundary of Iberia from upper Cretaceous onwards. In some cases this phase led to a complete replacement of the primary magnetization.
Previously published data, which were at the time interpreted as being European-like in direction, are attributed to this phase. Hence, our results do not support the hypothesis of a micro-plate called “le Danois block”, which was suggested in order to explain these results. We believe that there is no paleomagnetic evidence supporting the existence of a complicated boundary between Europe and Iberia during the mid-Cretaceous opening of the Bay of Biscay. 相似文献
5.
A. I. Chernova D. V. Metelkin V. A. Vernikovsky N. Yu. Matushkin 《Doklady Earth Sciences》2018,481(1):847-851
This study demonstrates rock-magnetic and paleomagnetic investigations of Devonian and Mesozoic deposits of Kotelny, Stolbovoy, and Great Lyakhovsky islands. The results indicate that local remagnetization took place on the southwestern periphery on the archipelago of the New Siberian Islands. A comparison of new data with the apparent polar wander path for Siberia shows that the remagnetization happened during collisional events between 140 and 80 Ma and affected only the marginal part of the terrane of the New Siberian Islands that was directly facing the deformation front. The consistent younging of the remagnetization age from the south to the north indicates dextral rotation of the terrane of the New Siberian Islands during its collision with Siberia. 相似文献
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Bondarenko G. E. Soloviev A. V. Tuchkova M. I. Garver J. I. Podgornyi I. I. 《Lithology and Mineral Resources》2003,38(2):162-176
The South Anyui fold zone (western Chukotka) is considered a suture zone related to closure of the South Anyui oceanic basin and collision of Eurasia with the Chukotka–Arctic Alaska microcontinent in the Early Cretaceous. The existence of a compensatory sedimentation basin (foredeep) during folding in the terminal Jurassic–initial Cretaceous remains debatable. This work presents first data on age estimates of detrital zircons from Upper Mesozoic terrigenous sequences of the South Anyui suture zone obtained by the fission-track method. The distal flysch of presumably Late Jurassic age and the proximal flysch of probably Late Triassic age were sampled in the Uyamkanda River basin. The fission-track dating showed that sandstones from the flysch sections contain detrital zircons of two different-age populations. Young zircon populations from sandstones of distal turbidites in the upper course of the Uyamkanda River (two samples) are 149 ± 10.2 and 155.4 ± 9.0 Ma old (Late Jurassic), whereas those from coarse-grained proximal turbidites sampled in the lower course of the Uyamkanda River (one sample) is 131.1 ± 7.5 Ma old (Early Cretaceous). The data obtained indicate that the Late Mesozoic folding in the South Anyui suture zone was accompanied by the formation of a marginal sedimentary basin. Sediments accumulated in this basin compose tectonic nappes that constitute a fold–thrust structure with the northern vergence. 相似文献
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地壳的拆离作用与华北克拉通破坏:晚中生代伸展构造约束 总被引：19，自引：0，他引：19
伸展条件下的地壳拆离作用是岩石圈减薄的重要浅部构造响应。晚中生代时期的伸展构造(包括拆离断层、变质核杂岩构造和断陷盆地)在华北、华南、东北和东蒙古及贝加尔地区普遍发育,它们切过上部地壳(断陷盆地)、中、上地壳(拆离断层)或中部地壳(变质核杂岩)。地壳拆离作用具有运动学极性(NWW或SEE)、几何学宏观(区域)对称与微观(局部)不对称性、遍布全区但不均匀性,以及形成时间的跨越性(140~60Ma)等特点,并使得地壳和岩石圈发生显著的减薄。本文研究揭示出现今岩石圈厚度变化与晚中生代伸展构造的发育程度和分布之间并没有必然的联系。其变化的基本规律是,除新生代裂陷发育区岩石圈厚度明显较小且厚度有迅速变化外,从华北向贝加尔地区总体的变化趋势是逐渐加厚,也即东亚地区岩石圈具有楔形形态。晚中生代时期的地壳(或地幔)拆离作用伴随着广泛的岩石圈减薄作用,区域岩石圈同时遭受到一定程度的减薄和破坏,华北克拉通在这一时期的破坏仅仅是区域岩石圈减薄在华北的具体体现。 相似文献
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《Journal of Asian Earth Sciences》1999,17(4):477-519
Paleomagnetic results from Upper Jurassic to Paleocene rocks in Peninsular Malaysia show counter clockwise (CCW) rotations, while clockwise rotations (CW) are predominantly found in older rocks. Continental redbeds of the Upper Jurassic to Lower Cretaceous Tembeling Group have a post folding remagnetization, giving a VGP at N54°E29°, corresponding to approximately 40° of CCW rotation relative to Eurasia and 60° CCW relative to the Indochina block (Khorat Plateau). Samples from Cretaceous to Paleocene mafic volcanics of the Kuantan dike swarm and the Segamat basalts give VGPs at N59°E47° and N34°E36°, respectively. These Malayasian data are indistinguishable from the Late Eocene and Oligocene VGPs reported for Borneo and the Celebes Sea and are similar to the Eocene VGPs reported for southwest Sulawesi and southwest Palawan. The occurrence of CCW deflected data over this large region suggests that much of Malaysia, Borneo, Sulawesi, and the Celebes Sea rotated approximately 30° to 40° CCW relative to the Geocentric Axial Dipole (GAD) between the Late Eocene and the Late Miocene, although not necessarily synchronously, nor as a single rigid plate. These regional CCW rotations are not consistent with simple extrusion based tectonic models. CW declinations have been measured in Late Triassic granites, Permian to Triassic volcanics, and remagnetized Paleozoic carbonates. The age of this magnetization is poorly understood and may be as old as Late Triassic, or as young as Middle or Late Cretaceous. The plate, or block rotations, giving rise to these directions are correspondingly weakly constrained. 相似文献
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D.V. Kovalenko 《Russian Geology and Geophysics》2010,51(4):387-403
Rock complexes in Mongolia experienced two remagnetization events. Almost all secondary remanence components of normal polarity were acquired apparently in the Cenozoic, after major deformation events, and those of reverse polarity were associated with intrusion of bimodal magmas during the Late Carboniferous–Permian reverse superchron. Active continental-margin sequences in some areas of Mongolia were folded prior to the Late Carboniferous–Permian magnetic event. The primary origin of magnetization in Late Paleozoic and Mesozoic rocks has been inferred to different degrees of reliability. According to paleolatitudes derived from most reliable paleomagnetic data, the analyzed rocks were located far north of the North China block throughout the Late Paleozoic and Early Mesozoic. Mongolia, as well as Siberia, moved from the south to the north in the Paleozoic, back from the north to the south between the latest Triassic and the latest Jurassic, and remained almost within the same latitudes in Cretaceous and Cenozoic time. These paleolatitudes show no statistical difference from those for the Siberian craton at least since the latest Permian (275–250 Ma). Older Mongolian complexes (with ages of 290, 316, and 330 Ma) likewise may have formed within the Siberian continent, which makes their paleomagnetic determinations applicable to calculate the polar wander path for Siberia. The paleolatitudes of Early Carboniferous sediments in Mongolia differ significantly from those of Siberia, either because of overprints from the reverse superchron or because they were deposited away from the Siberian margin. 相似文献
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广东梅县地区位于政和—大埔断裂南段之莲花山断裂带中。通过开展1:5万野外地质调查及室内研究表明,广东梅县地区存在晚中生代伸展构造体系,该体系主要由剥离断层和2个不同层次的剥离层组成,结合火山岩、侵入岩、沉积地层接触关系及高精度测年数据,讨论了该体系的形成时限,认为其形成和主导作用时期在晚侏罗世—早白垩世早期(160 ~135 Ma),最大伸展期在145 Ma左右; 前人认为莲花山断裂为早古生代俯冲带,但研究表明,其构造属性为晚侏罗世形成的剥离断层。因此,政和—大埔断裂一带很可能也存在晚中生代的伸展构造体系,说明华南主要构造形迹奠定于中生代,这为华南主要热液金属矿床区域成矿规律研究提供了新的参考模型。 相似文献
13.
华北克拉通晚中生代壳-幔拆离作用: 岩石流变学约束 总被引：6，自引：5，他引：1
大陆岩石圈的流变学结构对于岩石圈深部过程(壳/幔过程)有着深刻的影响,直接表现在岩石圈壳-幔结构与浅部构造上.本文注意到华北克拉通晚中生代岩石圈减薄期间地壳的伸展、拆离与减薄在不同地区的宏观、微观构造及地壳岩石流变学等方面的差异表现与区域变化,以及现今和晚中生代时期岩石圈厚度的不均匀性.讨论了以水为主体的地质流体的存在对于岩石圈流变性的影响.综合克拉通东部与西部地壳/地幔厚度变化特点以及下地壳和上地幔含水性特点,阐述了晚中生代时期华北克拉通岩石圈内部壳幔耦合与解耦的规律,提出了华北岩石圈壳-幔拆离作用模型以解释华北克拉通晚中生代岩石圈减薄的基本现象与深部过程.提出区域性伸展作用是岩石圈减薄的主要动力学因素,东部地区在晚中生代伸展作用过程中壳-幔具有典型的解耦性,上部地壳、下部地壳和岩石圈地幔的变形具有显著差异性.而西部区壳幔总体具有耦合性,下地壳与岩石圈地幔共同构成流变学强度很高且难以变形的岩石圈根. 相似文献
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晚三叠世-侏罗纪是羌塘盆地大型海相沉积盆地形成时期,是研究羌塘盆地形成过程、判别盆地性质的重要时期.本文通过区域构造、盆地充填建造和岩相古地理分析,提出了该时期的羌塘盆地并非晚三叠世前陆盆地(或弧后盆地)和侏罗纪弧后盆地(前陆盆地),而是晚三叠世早期(肖茶卡期)的陆表海盆地和晚三叠世诺利期-中侏罗世巴柔期(那底岗日期-雀莫错期)的坳陷-裂陷盆.肖茶卡期内陆盆地主要受可可西里-金沙江活动带的控制,沉积期后出现的海退事件可能与冈瓦纳大陆与欧亚大陆的碰撞作用有关;那底岗日期-索瓦期羌塘盆地的强烈拉张断陷可能反映冈瓦纳大陆边缘的总体构造背景. 相似文献
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广西十万大山前陆冲断推覆构造 总被引：8，自引：0，他引：8
通过十万大山盆地内地震剖面资料和ＴＭ遥感图象的地质构造解译,结合重力资料和野外地质观察及构造分析,阐述了十万大山前陆冲断推覆构造的发育特征和前陆盆地的构造演化。前陆冲断推覆构造由３个不同的构造变形带组成：卷入海西和印支期花岗岩体的逆冲断裂带、充填中生代陆相沉积并发生构造滑脱的前陆盆地和对应于华南准地台的前陆腹地。冲断推覆构造的形成和演化是与中、晚古生代钦州海槽晚二叠世的褶皱回返和中生代相继的构造复活密切联系的,它经历了３期主要构造应力作用事件：晚二叠世海西运动晚幕为冲断推覆构造的雏形期,晚三叠世印支运动晚幕的近ＳＮ向挤压是陆相前陆盆地的发育期;早白垩世末期燕山运动主幕ＮＷ—ＳＥ向挤压是现今十万大山前陆冲断推覆构造的成型期。 相似文献
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L.S. Shu X.M. Zhou P. Deng B. Wang S.Y. Jiang J.H. Yu X.X. Zhao 《Journal of Asian Earth Sciences》2009,34(3):376-391
In order to better understand the Mesozoic tectonic evolution of Southeast China Block (SECB in short), this paper describes geological features of Mesozoic basins that are widely distributed in the SECB. The analyzed data are derived from a regional geological investigation on various Mesozoic basins and a recently compiled 1:1,500,000 geological map of Mesozoic–Cenozoic basins. Two types of basin are distinguished according to their tectonic settings, namely, the post-orogenic basin (Type I) and the intracontinental extensional basin (Type II); the latter includes the graben and the half-graben or faulted-depression basins. Our studies suggest that the formation of these basins connects with the evolution of geotectonics of the SECB. The post-orogenic basin (Type I) was formed in areas from the piedmont to the intraland during the interval from Late Triassic to Early Jurassic; and the formation of the intracontinental extensional basin (Type II) connects with an intracontinental crustal thinning setting in the Late Mesozoic. The graben basin was generated during the Middle Jurassic and is associated with a bimodal volcanic eruption; and the half-graben or faulted-depression basin, filled mainly by the rhyolite, tuff and sedimentary rocks during Early Cretaceous, is occupied by the Late Cretaceous–Paleogene red-colored terrestrial clastic rocks. We noticed that the modern outcrops of numerous granites and basins occur in a similar level, and the Mesozoic granitic bodies contact with the adjacent basins by large normal faults, suggesting that the modern landforms between granites and basins were yielded by the late crustal movement. The modern basin and range framework was settled down in the Cretaceous. Abundant sedimentary structures are found in the various basins, from that the deposited environments and paleo-currents are concluded; during the Late Triassic–Early Jurassic time, the source areas were situated to the north and northeast sides of the outcrop region. In this paper, we present the study results on one geological and geographical separating unit and two separating fault zones. The Wuyi orogenic belt is a Late Mesozoic paleo-geographically separating unit, the Ganjiang fault zone behaves as the western boundary of Early Cretaceous volcanic rocks, and the Zhenghe–Dapu fault zone separates the SE-China Coastal Late Mesozoic volcanic-sedimentary basins and the Wuyi orogenic belt. Finally, we discuss the geodynamic mechanisms forming various basins, proposing a three-stage model of the Mesozoic sedimentary evolution. 相似文献
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西秦岭晚中生代火山岩出露于青海省泽库县多福屯地区、甘肃省夏河县红墙和甘加地区。初步研究表明,甘加火山岩属于一套钾质拉斑玄武岩。该玄武岩富集REE、LILE及HFSE,但轻、重稀土元素分馏程度及不相容元素含量均略低于典型OIB和西秦岭晚中生代钠质碱性玄武岩。岩浆起源于软流圈释放的小体积富挥发份硅酸盐熔体交代形成的富集岩石圈地幔,并在上升中经历了较大程度的镁铁质矿物的分离结晶作用。岩石具有典型的陆内OIB成因特点,既不同于前人提出的甘加海山玄武岩,也不属于“二叠纪隆务峡-甘加蛇绿岩”组成部分,而与西秦岭晚中生代钠质碱性玄武岩均为大陆裂谷系OIB型岩浆作用的产物。甘加玄武岩可能具有比较复杂的岩石组合,跨越了晚古生代到晚中生代的一个较长时间范围。西秦岭晚中生代的大陆裂谷作用夭折于岩石圈拉张的早期阶段,它的出现及研究区广泛发育的近SN向或NW向断裂,可能是贺兰-川滇南北构造带与大型走滑断裂系复杂叠加并相互影响与改造的表现。 相似文献
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辽东南地区晚中生代地层发育不甚完全,具有两期盆地叠合演化的特征,即早中侏罗世和早白垩世两个演化阶段,经历了2次伸展裂陷和2次挤压反转。在详细研究辽东南地区各盆地岩石地层序列、生物化石组合特征、年代地层格架以及区域地层对比的基础上,讨论了盆地的演化阶段和演化规律,指出是古太平洋板块向东亚大陆边缘不同方向的俯冲与走滑,以及来自北方西伯利亚板块的持续碰撞挤压的联合构造应力场制约了中国东北地区晚中生代盆地的裂陷过程和构造反转的演化,进而为揭示华北克拉通晚中生代岩石圈演化的动力学机制提供参考依据。 相似文献
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笔者通过胜利油区惠民凹陷南坡地区古生代地层的沉积相发育与分布特点的研究，并结合区域构造运动，揭示了该地区古生代奥陶纪到中生代侏罗纪的构造和沉积体系发展演化规律。结果表明，整个研究区在早古生代发育了一套碳酸盐潮坪体系，晚古生代为海陆过渡的三角洲沉积体系，中生代为一套陆相河流体系。三角洲体系又包括了石炭纪的海相三角洲和二叠纪的陆相湖泊三角洲。该区在古生代和中生代经历着多期次、多类型的构造－沉积演化，从整个演化过程来看，总体上体现了从海到陆的过程。在空间上，除了在早古生代沉积相对稳定外，晚 古生代和中生代均表现了较明显的沉降差异性。 相似文献