共查询到20条相似文献，搜索用时 31 毫秒
1.
I. V. Golovanova K. N. Danukalov V. I. Kozlov V. N. Puchkov V. E. Pavlov Y. Gallet N. M. Levashova G. S. Sirota R. R. Khairullin M. L. Bazhenov 《Izvestiya Physics of the Solid Earth》2011,47(7):623-635
We have carried out paleomagnetic studies of the Upper Vendian sedimentary rocks from the Bashkirian Meganticlinorium (Southern
Ural). The rocks were sampled at three localities spread over more than 100 km. Totally, more than 300 samples were collected
from about 40 sampling sites. Stepwise thermal demagnetization up to 700°C revealed a stable component of magnetization of
either polarity in 25 sites. The fold test and the reversal test for this component are positive, which is usually regarded
as a sound argument in favor of the primary origin of magnetization. However, the Basu paleomagnetic pole (longitude 187.3°E,
latitude 1.1°N) is located near the Late Ordovician-Early Silurian segment of the apparent polar wander path for Baltica,
which might indicate a Paleozoic remagnetization of Vendian rocks. In this work we analyze different interpretations of the
obtained results and evaluate the reliability of the Late Riphean and Vendian paleomagnetic data for Baltica. 相似文献
2.
Although paleomagnetic study of the Early Paleozoic for the North China Block (NCB) has witnessed rapid progress since the 1980s, significant difference in the results can be found from the widespread areas in North China. Besides the paleomagnetic techniques used in the laboratories, the difference of these Paleozoic poles could also be due to the early and late Mesozoic remagnetization in the eastern part of China. It is therefore necessary to carry out systematic paleomagnetic and rock magnetic studies for the Early Paleozoic rocks in the NCB. The remagnetizarion re-sults from the northwestern part of Henan Province are reported, and related geological implications are discussed. 相似文献
3.
A. G. Iosifidi V. A. Mikhailova V. V. Popov E. S. Sergienko A. V. Danilova N. M. Otmas 《Izvestiya Physics of the Solid Earth》2018,54(1):163-177
New data for the Early and Late Carboniferous sections of the Russian platform (Moscow syneclise and Donbass) are presented. Magneto-mineralogical studies are carried out to identify the magnetic minerals—carriers of natural remanent magnetization. Extensive Late Paleozoic remagnetization of Carboniferous rocks is revealed. The obtained paleomagnetic data allowed us to determine the average paleomagnetic poles for the Gzhelian, Serpukhovian, and Visean stages of Carboniferous deposits of the Moscow syneclise. 相似文献
4.
A. M. Fetisova R. V. Veselovskiy F. Scholze Yu. P. Balabanov 《Izvestiya Physics of the Solid Earth》2018,54(1):150-162
The results of detailed paleomagnetic studies in seven Upper Permian and Lower Triassic reference sections of East Europe (Middle Volga and Orenburg region) and Central Germany are presented. For each section, the coefficient of inclination shallowing f (King, 1955) is estimated by the Elongation–Inclination (E–I) method (Tauxe and Kent, 2004) and is found to vary from 0.4 to 0.9. The paleomagnetic directions, corrected for the inclination shallowing, are used to calculate the new Late Permian–Early Triassic paleomagnetic pole for the East European Platform (N = 7, PLat = 52.1°, PLong = 155.8°, A95 = 6.6°). Based on this pole, the geocentric axial dipole hypothesis close to the Paleozoic/Mesozoic boundary is tested by the single plate method. The absence of the statistically significant distinction between the obtained pole and the average Permian–Triassic (P–Tr) paleomagnetic pole of the Siberian Platform and the coeval pole of the North American Platform corrected for the opening of the Atlantic (Shatsillo et al., 2006) is interpreted by us as evidence that ~250 Ma the configuration of the magnetic field of the Earth was predominantly dipolar; i.e., the contribution of nondipole components was at most 10% of the main magnetic field. In our opinion, the hypothesis of the nondipolity of the geomagnetic field at the P–Tr boundary, which has been repeatedly discussed in recent decades (Van der Voo and Torsvik, 2001; Bazhenov and Shatsillo, 2010; Veselovskiy and Pavlov, 2006), resulted from disregarding the effect of inclination shallowing in the paleomagnetic determinations from sedimentary rocks of “stable” Europe (the East European platform and West European plate). 相似文献
5.
Giovanni Muttoni Dennis V. Kent James E.T. Channell 《Earth and Planetary Science Letters》1996,140(1-4):97-112
A new early Late Triassic paleopole for Adria has been obtained from the Val Sabbia Sandstone in the Southern Alps. As Early Permian and Jurassic-Cretaceous paleomagnetic data from para-autochthonous regions of Adria such as the Southern Alps are consistent with ‘African’ APWPs[1–2], paleomagnetic data from this region can be used to bolster the West Gondwana APWP in the poorly known Late Permian-Triassic time interval. The Southern Alpine paleopoles are integrated with the West Gondwana and Laurussia APWPs of Van der Voo [1] and used to generate a tectonic model for the evolution of Pangea. The Early Permian overall mean paleopole for West Gondwana and Adria, in conjunction with the coeval Laurussia paleopole, support Pangea B of Morel and Irving [3]. The Late Permian/Early Triassic and the Middle/Late Triassic paleopoles from Adria and Laurussia support Pangea A-2 of Van der Voo and French [4]. The phase of transcurrent motion between Laurasia and Gondwana[5] that caused the Pangea B to A-2 transition occurred essentially in the Permian (at the end of Variscan orogeny) with an average relative velocity of approximately 10 cm/yr. Finally, the Late Triassic/Early Jurassic paleopoles from West Gondwana and Laurussia agree with Pangea A-1 of Bullard et al. [6], the widely accepted Pangea configuration at the time of the Jurassic breakup. 相似文献
6.
A. V. Shatsillo V. I. Paverman V. E. Pavlov 《Izvestiya Physics of the Solid Earth》2007,43(10):880-889
The paper presents results derived from study of the Silurian of the Nyuya-Berezovskii facial province. Variegated sedimentary rocks of the Meutian and Kurungian series (Llandoverian, Wenlockian, and lower Ludlovian) are studied. Detailed thermal demagnetizations of the collections revealed two stable magnetization components; one of them (Ds = 193.8, Is = 19.2; k = 10.7, α95 = 6.1) is bipolar and is likely to have formed during or shortly after the rock formation, i.e., in the interval from the Early Silurian to the beginning of the Late Silurian. The second component is unipolar and apparently metachronous, and its formation time can be bounded by the latest Early to the Middle Devonian. Based on the paleomagnetic results of this study, paleolatitudes and kinematics of Siberia are estimated for the Middle Paleozoic. The inferred paleomagnetic poles provide additional constraints on the Middle Paleozoic segment of the apparent polar wander path from the Siberian platform. 相似文献
7.
A. N. Khramov 《Izvestiya Physics of the Solid Earth》2007,43(10):800-810
The paper analyzes previously published results of studies of detailed records of geomagnetic reversals in sedimentary and volcanic sequences of the Paleozoic in the Siberian and Eastern European platforms. It is shown that the processes of geomagnetic reversals, both in the Early Paleozoic and at the end of this era, are well described by a model in which the transitional field is controlled by an equatorial dipole. During a reversal, this dipole maintained a magnetic field at the Earth’s surface whose intensity amounted to about 20% of the intensity before and after the reversal. The equatorial dipole existed before and during the reversal and was responsible for the deviation from antipodality of paleomagnetic poles of adjacent polarity chrons (the so-called reversal bias). The position of the equatorial dipole axis during the Paleozoic correlates with the supposed geometry of convective motions in the mantle at that time. 相似文献
8.
New paleomagnetic data are presented for Proterozoic metamorphic and Cambrian terrigenous-carbonate complexes of the southern Far East of Russia (Primor’e and the Amur and Trans-Baikal regions). Taking into account our results obtained previously, the paper presents revised positions of the paleomagnetic pole corresponding to the Riphean-Lower Paleozoic segment of the apparent polar wander path for terranes of the Amur plate (the Argun and Bureya-Khanka orogenic belts) in comparison with poles from the Siberian and North Chinese plates. It is shown that the paleolatitude positions of the Amur terranes were stable in space and time during the interval from the late Riphean to the end of the Early Cambrian: they were located in equatorial zones of the Northern and Southern hemispheres. 相似文献
9.
The paleomagnetic study of the Lower Ordovician and Cambrian sedimentary rocks exposed on the Narva River’s right bank revealed a multicomponent composition of natural remanent magnetization. Among four distinguished medium- and high-temperature magnetization components, the bipolar component, which carries the reversal test, is probably the primary component and reflects the geomagnetic field direction and variations during the Late Cambrian and Early Ordovician. The pole positions corresponding to this component have coordinates 22°N, 87°E (dp/dm = 5°/6°) for the Late Cambrian, and 18°N, 55°E (dp/dm = 5°/7°) for the Early Ordovician (Tremadocian and Arenigian). Together with the recently published paleomagnetic poles for the sections of the Early Ordovician in the Leningrad Region and the series of poles obtained when the Ordovician limestones were studied in Sweden, these poles form new key frameworks for the Upper Cambrian-Middle Ordovician segment of the apparent polar-wander path (APWP) for the Baltica. Based on these data, we propose a renewed version of the APWP segment: the model of the Baltica motion as its clockwise turn by 68° around the remote Euler pole. This motion around the great circle describes (with an error of A95 = 10°) both variations in the Baltic position from 500 to 456 Ma ago in paleolatitude and its turn relative to paleomeridians. According to the monopolar components of natural remanent magnetization detected in the Narva rocks, the South Pole positions are 2°S, 351°E (dp/dm = 5°/9°), 39°S, 327°E, (dp/dm = 4°/7°), and 42°S and 311°E (dp/dm = 9°/13°). It is assumed that these components reflect regional remagnetization events in the Silurian, Late Permian, and Triassic. 相似文献
10.
Paleomagnetic constraints on the tectonic history of the major blocks of China duing the Phanerozoic
Zhu Rixiang Yang Zhenyu Wu Hanning Ma Xinghua Huang Baochun Meng Zifang Fang Dajun 《中国科学D辑(英文版)》1998,41(2):1-19
Paleomagnetic study of China and its constraints on Asia tectonics has been a hot spot. Some new paleomagnetic data from three major blocks of China. North China Block (NCB), Yangtze Block (YZB) and Tarim Block (TRM) are first reported, and then available published Phanerozoic paleomagnetic poles from these blocks with the goal of placing constraints on the drift history and paleocontinental reconstruction are critically reviewed. It was found that all three major blocks were located at the mid-low latitude in the Southern Hemisphere during the Early Paleozoic. The NCB was probably independent in terms of dynamics. its drift history was dominant by latitudinal placement accompanying rotation in the Early Paleozoic. The YZB was close to Gondwanaland in Cambrian, and separated from Gondwanaland during the Late-Middle Ordovician. The TRM was part of Gondwanaland, and might be close to the YZB and Australia in the Early Paleozoic. Paleomagnetic data show that the TRM was separated from Gondwanaland during the Late-Middle Ordovician, and then drifted northward. The TRM was sutured to Siberia and Kazakstan blocks during the Permian, however, the composite Mongolia-NCB block did not collide with Siberia till Late Jurassic. During Late Permian to Late Triassic, the NCB and YZB were characterized by northern latitudinal placement and rotation on the pivot in the Dabie area. The NCB and YZB collided first in the eastern part where they were located at northern latitude of about 6°—8°, and a triangular oceanic basin remained in the Late Permian. The suturing zone was located at northern latitude of 25° where the two blocks collided at the western part in the Late Triassic. The collision between the two blocks propagated westward after the YZB rotated about 70° relative to the NCB during the Late Permian to Middle Jurassic. Then two blocks were northward drifting (about 5°) together with relative rotating and crust shortening. It was such scissors-like collision procedure that produced intensive compression in the eastern part of suturing zone between the NCB and YZB, in which continental crust subducted into the upper mantle in the Late Permian, and then the ultrahigh-pressure rocks extruded in the Late Triassic. Paleomagnetic data also indicate that three major blocks have been together clockwise rotating about 20° relative to present-day rotation axis since the Late Jurassic. It was proposed that Lahsa Block and India subcontinent successively northward subducted and collided with Eurasia or collision between Pacific/Philippines plates and Eurasia might be responsible for this clockwise rotating of Chinese continent. 相似文献
11.
Seismicityof the Novaya Zemlya archipelago: relocated event catalog from 1974 to 2014 总被引：1，自引：1，他引：0
Alexey N. Morozov Vladimir E. Asming Natalya V. Vaganova Yana V. Konechnaya Yana A. Mikhaylova Zinaida A. Evtyugina 《Journal of Seismology》2017,21(6):1439-1466
We have relocated seismic events registered in the area of the Novaya Zemlya Archipelago, which are not identified as nuclear explosions but are probably of tectonic nature. For the relocation, we collected all available seismic bulletins and waveform data. The location was performed by applying a modified method of generalized beamforming. Verification of the modified method and selection of the travel time model were performed using data on two Novaya Zemlya nuclear explosions that occurred on 02.11.1974 and 24.10.1990. The modified method and the BARENTS travel time model provide sufficient accuracy for event location in the region. The relocation procedure was applied for 9 seismic events registered in the area of the Novaya Zemlya Archipelago. As a result, the new coordinates of the five events turned out to be significantly different from those that were defined previously. 相似文献
12.
Paleomagnetic samples were collected from 190 m of the Late Carboniferous/Early Permian Casper Formation in southeastern Wyoming. A total of 549 samples was drilled near the vicinity of Horse Creek Station at an average stratigraphic interval of 33 cm. All samples were reversely magnetized. Rock magnetic analyses indicate that the primary carrier of remanence in the formation is hematite. A selection criterion applied to the partial demagnetized data restricted the sample population to 233, resulting in a paleomagnetic North Pole located at 47.4°N, 127.4°E (δp=0.7;δm=1.4). The Casper pole agrees well with other Late Carboniferous/Early Permian poles for cratonic North America. The tight clustering of these paleomagnetic poles suggests that little apparent polar motion with respect to North America occurred during this time. Comparing the stable North American poles with paleomagnetic poles from Late Carboniferous/Early Permian strata of the New England-Canadian Maritime region (Acadia) indicates that this region did not reach its present position relative to North America until at least the Early Permian. 相似文献
13.
用热退磁辅以交变退磁方法对采自塔里木盆地阿克苏地区四石厂剖面47个采样点518块标本进行了逐步磁清洗和测试。由本征剩磁方向统计得到塔里木地台晚古生代的古地磁极位置(晚泥盆世φ=10.5°S、λ=151.2°E;晚石炭世φ=52.2°N、λ=179.5°E;早二叠世φ=56.5°N,λ=190.1°E)。古地磁结果表明:塔里木地台在晚古生代是北方大陆的块体之一。从晚石炭世至早二叠世塔里木地台已和北方的哈萨克斯坦板块、西伯利亚地台、俄罗斯地台等连成一片,并且从中生代以来它们之间的相对位置没有发生过大规模的变动 相似文献
14.
Belén Oliva-Urcia Emilio L. Pueyo Juan C. Larrasoaña 《Earth and Planetary Science Letters》2008,265(3-4):525-534
New paleomagnetic analyses of Triassic, Cretaceous and Eocene strata in the south-central Pyrenees show evidence for a widespread remagnetization, located along the southern border of the Axial Zone, the Internal Sierras, and the northern part of the Jaca-Pamplona basin. This remagnetization, always reversed in polarity, was acquired after an extensive period of Late Eocene–Early Oligocene folding and tilting in the area, and affects limestones, sandstones, marls and red beds. In addition, a characteristic prefolding component was identified in 30% of Upper Cretaceous and Triassic red beds. These results, together with a revaluation of previously published paleomagnetic data from the central Pyrenees, indicate that the spatial distribution of the postfolding remagnetization coincides with that of a domain of pressure solution cleavage. A relationship between the intensity of the remagnetization and the characteristic (prefolding component) with respect to the density of cleavage surfaces, leads us to propose a mechanism for the remagnetization related to the development of pressure solution cleavage that is framed within the tectonic evolution of the central Pyrenees. Partial dissolution of rock under tectonic compression leads to the liberation and subsequent accumulation of insoluble minerals in cleavage planes. Magnetic grains are part of the relatively insoluble residue, and they reorient in the presence of the ambient field after they are freed during dissolution of the rock matrix. Chemical reequilibrium (dissolution and/or neoformation of magnetic carriers) during this process cannot be excluded. The remagnetization mechanism we propose can help to explain widespread remagnetizations in low to moderately deformed rocks without the need of large-scale migration of orogenic fluids. 相似文献
15.
Basal Paleozoic Tapeats Sandstone (Early and Middle Cambrian) in northern and central Arizona exhibits mixed polarity and a low-latitude paleomagnetic pole. Carbonates of Middle and early Late Cambrian age, and directly superposed carbonate and carbonate-cemented strata of latest Middle(?) and early Late Devonian age, are characterized by reversed polarity and high-latitude poles. The high-latitude Middle Cambrian pole, which appears to record a large but brief excursion of the polar wandering path, is considered provisional pending additional work. The Devonian data from Arizona indicate that a shift of the pole to a “late Paleozoic” position had occurred by Middle Devonian time. 相似文献
16.
本文报道塔里木地块阿克苏—柯坪—巴楚地区奥陶纪古地磁研究新结果.对采自44个采点的灰岩、泥灰岩及泥质砂岩样品的系统岩石磁学和古地磁学研究表明,所有样品可分成两组：第一类样品以赤铁矿和少量磁铁矿为主要载磁矿物,该类样品通常可分离出特征剩磁组分A;第二类样品以磁铁矿为主要载磁矿物,系统退磁揭示出这类样品中存在特征剩磁组分B.特征剩磁组分A分布于绝大多数奥陶纪样品中,具有双极性,但褶皱检验结果为负,推测其可能为新生代重磁化.特征剩磁组分B仅能从少部分中晚奥陶世样品中分离出,但褶皱检验结果为正,且其所对应古地磁极位置（40.7°S,183.3°E,dp/dm=4.8°/6.9°）与塔里木地块古生代中期以来的古地磁极位置显著差别,表明其很可能为岩石形成时期所获得的原生剩磁.古地磁结果表明塔里木地块中晚奥陶世位于南半球中低纬度地区,很可能与扬子地块一起位于冈瓦纳古大陆的边缘;中晚奥陶世之后,塔里木地块通过大幅度北向漂移和顺时针旋转,逐步与冈瓦纳大陆分离、并越过古赤道;至晚石炭世,塔里木地块已到达古亚洲洋构造域的南缘. 相似文献
17.
烃源岩热演化是含油气盆地烃源岩评价的基本内容之一,也是油气动态成藏研究的基础.通过系统分析地层沉积样式,结合盆地热史恢复结果,应用Easy%Ro化学动力学模型,模拟了四川盆地86口代表性钻井和200余口人工井点震旦系-下古生界烃源岩热演化史.结果表明,在盆地不同构造单元,下寒武统和下志留统烃源岩热演化特征存在明显差异,并据此建立了四种热演化模式:①加里东期成熟,早晚二叠世期间快速演化定型,以川南地区下寒武统烃源岩为代表;②加里东期未熟,早晚二叠世期间一次快速演化定型,以川西南下寒武统和川南下志留统烃源岩为代表;③加里东期成熟,晚海西-燕山期再次增熟,以川东、川北地区下寒武统烃源岩为代表;④加里东期未熟,晚海西-燕山期持续增熟,以川中地区下寒武统和川东、川北下志留统烃源岩为代表.通过对比研究沉积速率、热流和增温速率之间的耦合关系,剖析了四川盆地震旦系-下古生界烃源岩热演化的控制因素,即川西南和川南局部地区主要受控于早晚二叠世期间峨眉山地幔柱和玄武岩的异常热效应,而盆地其它地区则受沉积地层埋深增热和盆地热流演化的共同作用,其中沉积地层埋深增热对烃源岩增温效应更加显著. 相似文献
18.
A. M. Fetisova R. V. Veselovskiy Yu. P. Balabanov N. V. Sal’naya 《Izvestiya Physics of the Solid Earth》2017,53(5):635-644
One of the key challenges which are traditionally encountered in studying the paleomagnetism of terrigenous sedimentary strata is the necessity to allow for the effect of shallowing of paleomagnetic inclinations which takes place under the compaction of the sediment at the early stages of diagenesis and most clearly manifests itself in the case of midlatitude sedimentation. Traditionally, estimating the coefficient of inclination flattening (f) implies routine re-deposition experiments and studying their magnetic anisotropy (Kodama, 2012), which is not possible in every standard paleomagnetic laboratory. The Elongation–Inclination (E–I) statistical method for estimating the coefficient of inclination shallowing, which was recently suggested in (Tauxe and Kent, 2004), does not require the investigation of the rock material in a specially equipped laboratory but toughens the requirements on the paleomagnetic data and, primarily, regarding the volume of the data, which significantly restricts the possibilities of the post factum estimation and correction for inclination shallowing. In this work, we present the results of the paleomagnetic reinvestigation of the Puchezh and Zhukov ravine (ravine) reference sections of the Upper Permian and Lower Triassic rocks in the Middle Volga region. The obtained paleomagnetic data allowed us to estimate the coefficient of inclination shallowing f by the E–I method: for both sections, it is f = 0.9. This method was also used by us for the paleomagnetic data that were previously obtained for the Permian–Triassic rocks of the Monastyrskii ravine (Monastirskoje) section (Gialanella et al., 1997), where the inclination shallowing coefficient was estimated at f = 0.6. 相似文献
19.
V. A. Bol’shakov 《Izvestiya Physics of the Solid Earth》2017,53(2):293-310
The results of numerous rock magnetic and paleomagnetic studies of Pleistocene deposits in the Loess Plateau in China which were obtained over a period of a few decades are analyzed. It is shown that two important problems remain unsolved. These are (1) developing the particular mechanism of “magnetic enhancement” in the soils, probably with a more accurate assessment of the level of effect of various natural factors causing qualitative changes in the magnetic fraction of the soil. Here, both the chemical composition of the newly crystallized magnetic mineral causing this enhancement and the parameters of the corresponding secondary (chemical) magnetization process should be determined. (2) Fixing the exact climate-stratigraphic position of the main paleomagnetic benchmarks of the Pleistocene, primarily the Matuyama–Brunhes reversal. In contrast to many conclusions, it is inferred that the Pleistocene paleoclimatic loess-soil record in China generally disagrees with the oxygen isotope (OI) record in the deep-sea sediments. This inconsistency is particularly significant for the Matuyama chron deposits. 相似文献
20.
Magdalena Kądziałko-Hofmokl Jacek Szczepański Tomasz Werner Maria Jeleńska Krzysztof Nejbert 《Acta Geophysica》2013,61(3):535-568
The results of palaeomagnetic, rock magnetic, and microscopic study of Early Paleozoic metabasites and granulites from the Orlica?nie?nik Dome (OSD, Sudetes) have been combined with geochronological data. In the eastern part of the OSD (?nie?nik Massif, SM) ferrimagnetic pyrrhotite is prevalent, accompanied by various amounts of Fe-oxides. In the western part of the OSD (Orlica-Bystrzyca Massif, OBM) Fe-oxides dominate. All magnetic minerals originated during hydrothermal and weathering processes. The palaeomagnetic study revealed the presence of three secondary components of natural remanence: Late Carboniferous, Late Permian, and Mesozoic. Two Paleozoic components are related to volcanic activity in the Sudetes. They are carried by pyrrhotite and Fe-oxides and were isolated only in SM rocks. The Mesozoic component was determined in both parts of the OSD and is carried by Fe-oxides. It covers a time span, from ～160 to ～40 Ma, corresponding to a long period of alteration. 相似文献