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1.
Frank R. Ettensohn 《Journal of Geodynamics》1997,23(3-4)
Both before and after inclusion of Laurussia in Pangea, the continent was a site of extensive epicontinental, marine, black-shale deposition, but from Pennsylvanian to Jurassic time when North America was an integral part of Pangea, the pattern of black-shale deposition was one of long-term decline. In North America the decline seems to have been greatest in Late Permian and Triassic times. Although this decline could have reflected a period of global cooling and a related decrease in organic productivity brought on by conditions associated with the supercontinent state, mapping the distribution of black shales in time and space on North American parts of Pangea suggests that the restricted availability of suitable repositories for organic-rich sediments may have been an equally important cause. In fact, mapping shows that the distribution of North American, Pangean, marine, black shales was greatest during Mississippian assembly of Laurussia when foreland-basin-type repositories were abundant and again during Late Jurassic fragmentation when rift-basin-type repositories were abundant. In both cases, tectonically conditioned basins formed the major repositories and promoted certain conditions that enhanced early basin anoxia.During Late Permian and Triassic time, when Pangea had been assembled, neither compressive orogenies nor crustal extension were major influences on North America. Consequently, suitable repositories were minimal and so was the extent of black-shale deposition. However, the continued presence of even a few major black-shale deposits during this time of minimum suggests that even low organic productivity was not a primary cause of decline and points to the possible significance of active continent assembly and breakup in generating tectonic-basin repositories conducive to accumulation and preservation of the organic matter that is nearly always present in quantities great enough to form major black-shale deposits. 相似文献
2.
3.
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
4.
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
5.
In order to test two different proposals for the poorly defined African Paleozoic apparent polar wander path (APWP), a paleomagnetic study was carried out on Ordovician through Carboniferous clastic sediments from the Cape Fold belt, west of the 22nd meridian. One proposal involves a relatively simple APWP connecting the Ordovician Gondwana poles in North Africa with the Late Paleozoic poles to the east of South Africa in a more or less straight line crossing the present equator in the Devonian. The other proposal adds a loop to this path, connecting Ordovician poles in North Africa with poles to the southwest of South Africa and then returning to central Africa. This loop would occur mainly in Silurian time. New results reported herein yield paleopoles in northern and central Africa for Ordovician to lowermost Silurian and Lower to Middle Devonian formations. The best determined paleopole of our study is for the Early Ordovician Graafwater Formation and falls at 28°N, 14°E (k = 25, α95 = 8.8°, N = 28 samples). The other paleopoles are not based on sufficient numbers of samples, but can help to constrain the apparent polar wander path for Gondwana. Our results give only paleopoles well to the north of South Africa and we observe no directions within the proposed loop. Hence, if the loop is real, it must have been of relatively short duration (60–70 Ma) and be essentially of Silurian/Early Devonian age, implying very high drift velocities for Gondwana (with respect to the pole) during that interval. 相似文献
6.
Tethyan ophiolites and Pangea break-up 总被引：6，自引：0，他引：6
Abstract The break‐up of Pangea began during the Triassic and was preceded by a generalized Permo‐Triassic formation of continental rifts along the future margins between Africa and Europe, between Africa and North America, and between North and South America. During the Middle–Late Triassic, an ocean basin cutting the eastern equatorial portion of the Pangea opened as a prograding branch of the Paleotethys or as a new ocean (the Eastern Tethys); westwards, continental rift basins developed. The Western Tethys and Central Atlantic began to open only during the Middle Jurassic. The timing of the break‐up can be hypothesized from data from the oceanic remnants of the peri‐Mediterranean and peri‐Caribbean regions (the Mesozoic ophiolites) and from the Atlantic ocean crust. In the Eastern Tethys, Middle–Late Triassic mid‐oceanic ridge basalt (MORB) ophiolites, Middle–Upper Jurassic MORB, island arc tholeiite (IAT) supra‐subduction ophiolites and Middle–Upper Jurassic metamorphic soles occur, suggesting that the ocean drifting was active from the Triassic to the Middle Jurassic. The compressive phases, as early as during the Middle Jurassic, were when the drifting was still active and caused the ocean closure at the Jurassic–Cretaceous boundary and, successively, the formation of the orogenic belts. The present scattering of the ophiolites is a consequence of the orogenesis: once the tectonic disturbances are removed, the Eastern Tethys ophiolites constitute a single alignment. In the Western Tethys only Middle–Upper Jurassic MORB ophiolites are present – this was the drifting time. The closure began during the Late Cretaceous and was completed during the Eocene. Along the area linking the Western Tethys to the Central Atlantic, the break‐up was realized through left lateral wrench movements. In the Central Atlantic – the link between the Western Tethys and the Caribbean Tethys – the drifting began at the same time and is still continuing. The Caribbean Tethys opened probably during the Late Jurassic–Early Cretaceous. The general picture rising from the previous data suggest a Pangea break‐up rejuvenating from east to west, from the Middle–Late Triassic to the Late Jurassic–Early Cretaceous. 相似文献
7.
Jean-Jacques Schott Raymond Montigny Robert Thuizat 《Earth and Planetary Science Letters》1981,53(3):457-470
A paleomagnetic and potassium-argon dating investigation has been carried out on a 530-km-long dike system which transects the western Iberian Peninsula in a northeasterly direction. The K-Ar age determinations were made on mineral separates exclusively. They range between 160 and 200 Ma and the authors suppose that this reflects the actual time interval of the intrusion, in accord with previous results. The paleomagnetic pole derived from 12 sites regularly distributed along the dike (71°N, 236°E) coincides well with other Mesozoic paleomagnetic poles from the western Africa. A contemporaneous pole from stable Europe is tentatively deduced from African and North American Late Triassic/Early Jurassic poles using different reconstruction models around the North Atlantic Ocean. The divergence between this pole and the Iberian pole corresponds to the result obtained for Permian poles. 相似文献
8.
Daniel Alberto Valencio 《Physics of the Earth and Planetary Interiors》1974,9(3):221-225
The South American palaeomagnetic poles published after the Upper Mantle Conference on Solid Earth Problems held at Buenos Aires in 1970, are summarized.The Late Palaeozoic-Cretaceous section of the South American polar wandering curve is now defined on the basis of twenty palaeomagnetic poles; these poles define five “age groups” at Late Carboniferous, Permo-Carboniferous, Middle Permian, Triassic and Cretaceous times.The comparison of the Late Palaeozoic-Mesozoic sections of the polar wandering curves of South America, Australia and Africa suggests that the former fragmentation of the Gondwana occurred in Late Carboniferous or Permo-Carboniferous times and that the origin of the South Atlantic Ocean took place after the Middle Jurassic (160 m.y.) but before the Early Cretaceous (120 m.y.). 相似文献
9.
XingFeng Yang Xin Cheng YaNan Zhou Lun Ma XiaoDong Zhang ZhaoSheng Yan XiMing Peng HaiLun Su HanNing Wu 《中国科学:地球科学(英文版)》2017,60(1):124-134
Results of a systematic paleomagnetic study are reported based on Late Carboniferous to Early Permian sedimentary rocks on the north slope of the Tanggula Mountains,in the northern Qiangtang terrane(NQT),Tibet,China.Data revealed that magnetic minerals in limestone samples from the Zarigen Formation(CP^z)are primarily composed of magnetite,while those in sandstone samples from the Nuoribagaribao Formation(Pnr)are dominated by hematite alone,or hematite and magnetite in combination.Progressive thermal,or alternating field,demagnetization allowed us to isolate a stable high temperature component(HTC)in 127 specimens from 16 sites which successfully passed the conglomerate test,consistent with primary remnance.The tilt-corrected mean direction for Late Carboniferous to Early Permian rocks in the northern Qiangtang terrane is D_s=30.2°,I_s=-40.9°,k_s=269.0,a_(95)=2.3°,N=16,which yields a corresponding paleomagnetic pole at 25.7°N,241.5°E(dp/dm=2.8°/1.7°),and a paleolatitude of 23.4°S.Our results,together with previously reported paleomagnetic data,indicate that:(1)the NQT in Tibet,China,was located at a low latitude in the southern hemisphere,and may have belonged to the northern margin of Gondwana during the Late Carboniferous to Early Permian;(2)the Paleo-Tethys Ocean was large during the Late Carboniferous to Early Permian,and(3)the NQT subsequently moved rapidly northwards,perhaps related to the fact that the Paleo-Tethys Ocean was rapidly contracting from the Late Permian to Late Triassic while the Bangong Lake-Nujiang Ocean,the northern branch of the Neo-Tethys Ocean,expanded rapidly during this time. 相似文献
10.
Structure of Sumatra and its implications for the tectonic assembly of Southeast Asia and the destruction of Paleotethys 总被引：3，自引：0，他引：3
It is now generally accepted that Southeast Asia is composed of continental blocks which separated from Gondwana with the formation of oceanic crust during the Paleozoic, and were accreted to Asia in the Late Paleozoic or Early Mesozoic, with the subduction of the intervening oceanic crust. From east to west the Malay peninsula and Sumatra are composed of three continental blocks: East Malaya with a Cathaysian Permian flora and fauna; Sibumasu, including the western part of the Malay peninsula and East Sumatra, with Late Carboniferous–Early Permian 'pebbly mudstones' interpreted as glaciogenic diamictites; and West Sumatra, again with Cathaysian fauna and flora. A further unit, the Woyla nappe, is interpreted as an intraoceanic arc thrust over the West Sumatra block in the mid Cretaceous. There are varied opinions concerning the age of collision of Sibumasu with East Malaya and the destruction of Paleotethys. In Thailand, radiolarites have been used as evidence that Paleotethys survived until after the Middle Triassic. In the Malay peninsula, structural evidence and the ages of granitic intrusions are used to support a Middle Permian to Early Triassic age for the destruction of Paleotethys. It is suggested that the West Sumatra block was derived from Cathaysia and emplaced against the western margin of Sibumasu by dextral transcurrent faulting along a zone of high deformation, the Medial Sumatra Tectonic Zone. These structural units can be traced northwards in Southeast Asia. The East Malaya block is considered to be part of the Indochina block, Sibumasu can be traced through Thailand into southern China, the Medial Sumatra Tectonic Zone is correlated with the Mogok Belt of Myanmar, the West Burma block is the extension of the West Sumatra block, from which it was separated by the formation of the Andaman Sea in the Miocene, and the Woyla nappe is correlated with the Mawgyi nappe of Myanmar. 相似文献
11.
Palynofloral changes in the Upper Paleozoic and Mesozoic of the Deocha-Pachami area,Birbhum Coalfield,West Bengal,India 总被引：1，自引：0，他引：1
Vijaya 《中国科学D辑(英文版)》2009,52(12):1932-1952
The study of Upper Paleozoic and Mesozoic palynomorphs in three boreholes from the Deocha-Pachami area, Birbhum Coalfield,
West Bengal, India, has allowed dating of the Talchir, Barakar, Dubrajpur, and Rajmahal formations, and revealed many hiatuses.
The lowermost unit, the Talchir Formation, yielded earliest Permian palynomorphs. The Barakar Formation, which includes coal-bearing
strata, was previously dated as Early Permian. However, data presented herein indicate an Early Permian to earliest Triassic
age for this unit-containing actually the Karharbari, Barakar s.s., Kulti, and Ranigang formations as well as the basal part
of the Panchet Formation. The overlying Dubrajpur Formation is Jurassic (Callovian to Tithonian), with an unconformity at
its base. The uppermost Dubrajpur Formation is Tithonian-Berriasian. The palynomorphs from the intertrappeans within the Rajmahal
Formation suggest an Early Cretaceous age. The revised ages of the Barakar and Dubrajpur formations are of major regional
significance. The distribution patterns of spore-pollen may provide a broad spectrum of paleoclimate during Permian, Late
Jurassic, and Early Cretaceous times, as there is no record of marine signatures in the study area. 相似文献
12.
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
13.
E. Salmon R. Montigny J.B. Edel A. Pique R. Thuizat M. Westphal 《Earth and Planetary Science Letters》1987,81(2-3)
The plutonic intrusion known as the Msissi norite (southern Morocco), which represents the single paleomagnetic reference pole for Africa in Devonian times, has been investigated. This Msissi intrusion is in fact an alkaline gabbro, a teschenite. K/Ar dating on separate biotites yields a 140 Ma age. Paleomagnetic results reveal a large scatter of isolated directions that precludes the computation of any Late Jurassic/Early Cretaceous paleopole. All these data lead us to reject this intrusion as a reference pole for the Devonian in Africa. The paleoposition of Africa in Devonian times remains, therefore, largely unknown. 相似文献
14.
Abstract In this paper, a summary of the tectonic history of the Mirdita ophiolitic nappe, northern Albania, is proposed by geological and structural data. The Mirdita ophiolitic nappe includes a subophiolite mélange, the Rubik complex, overlain by two ophiolite units, referred to as the Western and Eastern units. Its history started in the Early Triassic with a rifting stage followed by a Middle to Late Triassic oceanic opening between the Adria and Eurasia continental margins. Subsequently, in Early Jurassic time, the oceanic basin was affected by convergence with the development of a subduction zone. The existence of this subduction zone is provided by the occurrence of the supra‐subduction‐zone‐related magmatic sequences found in both the Western and Eastern units of the Mirdita ophiolitic nappe. During the Middle Jurassic, continuous convergence resulted in the obduction of the oceanic lithosphere, in two different stages – the intraoceanic and marginal stages. The intraoceanic stage is characterized by the westward thrusting of a young and still hot section of oceanic lithosphere leading to the development of a metamorphic sole. In the Late Jurassic, the marginal stage developed by the emplacement of the ophiolitic nappe onto the continental margin. During this second stage, the emplacement of the ophiolites resulted in the development of the Rubik complex. In the Early Cretaceous, the final emplacement of the ophiolites was followed by the unconformable sedimentation of the Barremian–Senonian platform carbonate. From the Late Cretaceous to the Middle Miocene, the Mirdita ophiolitic nappe was translated westward during the progressive migration of the deformation front toward the Adria Plate. In the Middle to Late Miocene, a thinning of the whole nappe pile was achieved by extensional tectonics, while the compression was still active in the westernmost areas of the Adria Plate. On the whole, the Miocene deformations resulted in the uplift and exposition of the Mirdita ophiolites as observed today. 相似文献
15.
The Mesozoic basins in Yanshan, China underwent several important tectonic transformations, including changes from a pre-Late Triassic marginal cratonic basin to a Late Triassic-Late Jurassic flexural basin and then to a late Late Jurassic-Early Cretaceous rift basin. In response to two violent intraplate deformation at Late Triassic and Late Jurassic, coarse fluvial depositional systems in Xingshikou and Tuchengzi Formations were deposited in front of thrust belts. Controlled by transform and extension faulting, fan deltas and lacustrine systems were deposited in Early Cretaceous basins. The composition of clastic debris in Late Triassic and Late Jurassic flexural basins respectively represents unroofing processes from Proterozoic to Archean and from early deposited, overlying pyroclastic rocks to basement rocks in provenance areas. Restored protobasins were gradually migrated toward nearly NEE to EW-trending from Early Jurassic to early Late Jurassic. The Early Cretaceous basins with a NNE-trending crossed over early-formed basins. The Early-Late Jurassic and Early Cretaceous basins were respectively controlled by different tectonic mechanisms. 相似文献
16.
P. Morel E. Irving L. Daly A. Moussine-Pouchkine 《Earth and Planetary Science Letters》1981,55(1):65-74
The characteristic magnetization of redbed samples from the upper part of the Série d'Abadla (probably Early Permian 31°N, 2.7°W) has a mean direction derived from 13 sites of D=129°, I=11°, k=59, α95=6° and a corresponding south paleopole at 29°S, 60°E, A95=5°. All directions have reversed polarity. The paleolatitude of the northern fringe of the Saharan craton was 6°±3°S, which is in excellent agreement with that for the Moroccan Meseta. Therefore, in all probability, there has been no paleolatitudinal displacement greater than about 500 km of the Moroccan Meseta relative to Africa since Permian time. Comparison of results from sedimentary rocks shows no evidence for relative rotation of the Moroccan Meseta since Permian time. Small apparent rotations are indicated by evidence from massive trachyandesite lavas from Morocco, but we argue that these could have arisen from the incomplete averaging of secular variation and uncertainties in estimates of paleohorizontal, rather than from true tectonic rotations. The combined latest Carboniferous/Early Permian paleopole for the Saharan craton and the Meseta differs form the path of apparent polar wandering for North America when the continents are assembled in Wegener's Pangea (Pangea A, in which northwest Africa is opposite North America). It is in reasonable agreement when the continents are assembled in the Pangea B configuration (northwest Africa opposite Europe). 相似文献
17.
The Shan-Thai Block, regarded traditionally as awhole geotectonic unit by the geologists engaged inthe study of geotectonic evolution of Southeast Asia, issituated to the west of the Ailaoshan and Nan-UttaraditSutures and to the east of the Shan Boundary Faults,and covers southwestern Yunnan, eastern Myanmar,most of Thailand, northwestern Laos, western Malay-sia, and Sumatra[1,2] (fig. 1). However, recent researchshows that it consists of two continental terranes fromGondwana and Cathay… 相似文献
18.
Flavien Choulet Michel Faure Dominique Cluzel Yan Chen Wei Lin Bo Wang Bei Xu 《中国科学:地球科学(英文版)》2016,59(1):25-57
The Altaid tectonic collage extends over Central Asia, exposing numerous accretionary orogens that can account for the Palaeozoic continental crust growth. A pluridisciplinary approach, using geochronological, geochemical, structural and palaeomagnetic tools was carried out to unravel the architecture and the evolution of West Junggar(Northwestern China), a segment of the Altaid Collage. A polycyclic geodynamic evolution is inferred and includes:(1) an Early Palaeozoic cycle, characterized by the closure of two oceanic basins bounded by island-arc systems;(2) an Early Devonian subduction jamming resulting in a minor-scale collision documented by thrusting, syntectonic sedimentation and subsequent crutal thinning associated with alkaline magmatism;(3) a Late Palaeozoic cycle, driven by the evolution of two opposite subduction zones developed upon the Early Palaeozoic basement. Detailed structural analysis and paleomagnetic data provide constraints for the late evolution of Junggar in the frame of the development of the Late Palaeozoic Kazakh orocline, which led to oblique subduction and transpression in the West Junggar accretionary complex. Progressive buckling of the Kazakh orocline further resulted in Late Carboniferous to Permian wrench tectonics, and lateral displacement of lithotectonic units. Block rotations that continued after the Late Triassic are due to diachronous intraplate reactivation. This scenario mirrors the Palaeozoic geodynamics of the Altaid Collage. Multiple Early Palaeozoic collisions of intra-oceanic arcs and micro continents have contributed to the formation of the Kazakhstan Microcontinent. Since the Late Palaeozoic, subductions formed around this microcontinent and the final oblique closure of oceanic domains resulted in the transcurrent collage of Tarim and Siberia cratons. Palaeozoic strike-slip faults were later reactivated during Mesozoic intracontinental tectonics. 相似文献
19.
We have obtained additional evidence for the Early Carboniferous paleomagnetic field for cratonic North America from study of the Barnett Formation of central Texas. A characteristic magnetization of this unit was isolated after thermal demagnetization at four sites (36 samples) out of eight sites (65 samples) collected. The mean direction of declination = 156.3°, inclination = 5.8° (N = 4 ,k = 905 , α95 = 3.0°), corresponds to a paleomagnetic pole position at lat. = 49.1°N,long. = 119.3°E (dp = 1.5° , dm = 3.0°). Field evidence suggests that characteristic magnetization was acquired very early in the history of the rock unit whereas the rejected sites are comprised of weakly magnetized limestones dominated by secondary components near the present-day field direction. Comparison of the Barnett pole with other Early Carboniferous (Mississippian) paleopoles from North America shows that it lies close to the apparent polar wander path for stable North America and that the divergence of paleopoles from the Northern Appalachians noted previously for the Devonian persisted into the Early Carboniferous. We interpret this difference in paleopoles as further evidence for the Northern Appalachian displaced terrain which we refer to here as Acadia, and the apparent coherence of Late Carboniferous paleopoles as indicating a large (～1500 km) motion of Acadia with respect to stable North America over a rather short time interval in the Carboniferous. 相似文献
20.
V. V. Abashev D. V. Metelkin N. E. Mikhal’tsov V. A. Vernikovsky N. Yu. Matushkin 《Izvestiya Physics of the Solid Earth》2017,53(5):677-694
The rock magnetic and paleomagnetic results from the Upper Paleozoic sedimentary sequences composing the isles of the Novaya Zemlya Archipelago are presented. The recorded temperature dependences of the magnetic susceptibility, the magnetic hysteresis parameters, and the results of the first-order reversal curve (FORC) measurements suggest the presence of single-domain or pseudo-single-domain magnetite and hematite grains in the rocks. The Upper Paleozoic deposits overall are promising for unraveling the tectonic evolution of the Barents–Kara region. Together with the rock magnetic data, the positive fold and reversal tests testify to the primary origin of the indentified magnetization components. However, the interpretation of the paleomagnetic data should take into account the probable inclination shallowing. New substantiation is offered for the paleomagnetic poles for Early Devonian and Late Permian. For the first time, paleomagnetic constraints are obtained for the Late Carboniferous boundary. It is shown that the Early Cimmerian deformation stage within the Paikhoi–Novaya Zemlya region is associated with the sinistral strike slip displacement along the Baidaratskii suture during which the internal structure of the Southern Novaya Zemlya segment could undergo shear in addition to the nappe-thrust transformations. The Northern Novaya Zemlya segment, which is shifted northwest with respect to the Southern segment, was deformed in the thrusting mode with an overall clockwise rotation of this segment relative to the East European Craton. 相似文献