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1.
A paleomagnetic study of Late Mesozoic dolente dykes and sills and Paleozoic sediments from Spitsbergen, the main island of the Svalbard Archipelago, gives the position of the pole in the Late Mesozoic and Paleozoic as distinct from the corresponding poles of Europe and North America. The Paleozoic pole is to the south of corresponding poles for Europe and North America. The data suggest that Svalbard has moved independently of Europe and North America at least in the Late Mesozoic, and thus might behave as a microplate or block. 相似文献
2.
《International Geology Review》2012,54(9):1054-1066
Varying correlations of Triassic continental deposits are the chief cause of the differences in biogeographic zonation of the Triassic continents. In order to correlate the continental deposits of Triassic age on the basis of their plant fossils, one must appraise the stratlgraphic significance of the most important foral assemblages in Triassic deposits. Within the Triassic system there are plant fossil assemblages associated with marine deposits, which can be dated directly. Age of the plant assemblages In the German basin can be determined by correlation with the Alpine section. The age of the homotaxic plant fossil assemblages of Europe and Asia can be established on the basis of a comparison with the above-mentioned standard assemblages. Four phytostratigraphic horizons (the Indian, Olenekian-Anisian, Ladinian-Carnian, and Norian-Rhaetian) can be distinguished in Eurasia. Biogeographic zonation is considered separately for the time interval represented by each of these horizons. Correlation of the fossil floral assemblages of North America and Gondwana with those of Eurasia is based on different paleontological data (tetrapod fossils playing the leading part in North America). Maps of the biogeographic zonation of the continental Triassic were prepared for the Oleneklan-Anisian and the Ladinian- Carnian intervals of time; for the southern hemisphere these are based on the mobilist concept. —Author. 相似文献
3.
Early Cretaceous intracontinental movements within Africa and/or South America, to account for misfit problem in the pre-drift reconstruction of Western Gondwana, have been tested using palaeomagnetic poles from both continents. Each continent has been considered as comprising separate subplates according to the boundaries proposed by Pindell and Dewey (1982) and Curie (1983): i.e., northern Africa (
), southern Africa (
), northern South America (nsa) and southern South America (
). Visual and statistical distribution of Late Permian to Jurassic poles from the African subplates indicate two distinct groups before rotating
relative to
, while after the rotation they become indistinguishable. The distribution and sparsity of data from South America limit the study in this continent as the data are statistically indistinguishable before and after rotation of
with respect to
. When the test is extended to the reconstruction of Western Gondwana, the tightest grouping of the poles occurs when an intracontinental movement is assumed within Africa. This suggests that the misfit between the two continents is probably due to intracontinental deformation within Africa and not in South America. If confirmed, this may have profound implications in the kinematics of the processes related to the opening of the South and Central Atlantic Oceans and also the origin of the West African Rift System. 相似文献
4.
María Paula Iglesia Llanos Claudia Beatriz Prezzi 《International Journal of Earth Sciences》2013,102(3):745-759
From the Late Carboniferous until the Middle Jurassic, continents were assembled in a quasi-rigid supercontinent called Pangea. The first palaeomagnetic data of South America indicated that the continent remained stationary in similar present-day latitudes during most of the Mesozoic and even the Palaeozoic. However, new palaeomagnetic data suggest that such a scenario is not likely, at least for the Jurassic. In order to test the stationary versus the dynamic-continent model, we studied the Jurassic apparent polar wander paths of the major continents, that is, Eurasia, Africa and North America that all in all show the same shape and chronology of the tracks with respect to those from South America. We thus present a master path that could be useful for the Jurassic Pangea. One of the most remarkable features observed in the path is the change in pole positions at ~197 Ma (Early Jurassic), which denotes the cessation of the counter-clockwise rotation of Pangea and commencement of a clockwise rotation that brought about changes in palaeolatitude and orientation until the end of the Early Jurassic (185 Ma). Here, we analyse a number of phenomena that could have triggered the polar shift between 197 and 185 Ma and conclude that true polar wander is the most likely. In order to do this, we used Morgan’s (Tectonophysics 94:123–139, 1983) grid of hotspots and performed “absolute” palaeogeographical reconstructions of Pangea for the Late Triassic and Jurassic. The palaeolatitudes changes that we observe from our palaeomagnetic data are very well sustained by diverse palaeoclimatic proxies derived from geological and palaeoecological data at this time of both the southern and northern hemispheres. 相似文献
5.
世界上约60%的油气产自碳酸盐岩。全球哪些地区、哪些时代碳酸盐岩发育？其时空分布受哪些因素控制？弄清这些问题,不仅对我国海外油气勘探战略选区有指导作用,而且可为了解全球古地理环境演化提供重要信息。根据全球179个碳酸盐岩盆地的数据统计分析,对全球显生宙碳酸盐岩时空分布规律进行了研究,并探讨了其控制因素。在显生宙的各个地质时期,碳酸盐岩均有分布,但不同时期,碳酸盐岩发育程度不同。在泥盆纪、白垩纪和古近纪,碳酸盐岩分布广泛,而在志留纪、二叠纪、三叠纪和侏罗纪,分布局限。不同时期,碳酸盐岩发育地区不同。寒武纪-奥陶纪,碳酸盐岩主要分布于俄罗斯、中国、北美洲、澳大利亚;三叠纪以后,碳酸盐岩发育区域转移至中东、北欧、北非、南美洲;至古近纪和新近纪,碳酸盐岩发育区主要分布于中东、北非、南亚地区。研究表明,全球碳酸盐岩时空分布受大陆漂移和全球海平面变化控制。古生代,古劳亚大陆、西伯利亚、中国华南地区、澳大利亚均位于赤道附近温暖浅海地带,碳酸盐岩发育,上述地区是这一时期碳酸盐岩分布主要区域;冈瓦纳大陆在古生代位于高纬度区,碳酸盐岩少。中生代,古劳亚大陆漂移至高纬度区,碳酸盐岩减少;冈瓦纳大陆解体为南美板块、非洲板块并漂移至低纬度区,发育碳酸盐岩。新生代,碳酸盐岩在南亚地区的增多,这也和板块的位置相印证。另外,当全球海平面上升时,海侵形成广阔的陆表海,碳酸盐岩广泛发育;当全球海平面下降时,海退形成陆缘海,碳酸盐岩发育面积减小。 相似文献
6.
郯庐断裂带东侧华南地块部分逆时针转动——古地磁新证据 总被引：3，自引：0，他引：3
本文对郯庐断裂带东西两侧的莱阳、六安、庐枞和怀宁等中新生代盆地内的中三叠世至早白垩世沉积构造变形进行了古地磁研究。采样区大多数特征磁化方向通过了褶皱检验或反极性检验,从上述地区共获得了10个可靠的中三叠世-早白垩世的古地磁极。该结果与华南地块的视极移曲线对比,可以看出,从中侏罗世以来,郯庐断裂带东西两侧不存在大规模地水平相对位移。但是,断裂带东边的华南地块部分存在15°-25°的逆时针转动。这种转动主要应发生在晚侏罗世,主要与华南、华北地块的碰撞以及太平洋板块的挤压有关。 相似文献
7.
A paleomagnetic study of the late Middle to possibly early Late Cambrian Liberty Hills Formation in the Ellsworth Mountains, Antarctica, reveals a stable magnetization with positive fold and reversal tests. The paleopole is based on 16 sites from volcanic and sedimentary rocks and lies at lat 7.3 degrees N and long 326.3 degrees E (A95=6.0&j0;). The new paleomagnetic data support the view that the Ellsworth Mountains are part of a microplate-the Ellsworth-Whitmore Mountains crustal block-that rotated independently of the main Gondwana continental blocks during breakup. The Liberty Hills pole differs from both previous poles recovered from Cambrian rocks in the Ellsworth Mountains and from the available Gondwana reference pole data. Our pole indicates a more northerly prebreakup position for the Ellsworth Mountains than previously suggested, contradicting the overwhelming geologic evidence for a prebreakup position close to southern Africa. The reasons for this are uncertain, but we suggest that problems with the Gondwana apparent polar wander path may be important. More well constrained, early Paleozoic paleomagnetic data are required from the Ellsworth Mountains and the Gondwana continents if the data are to constrain further the Middle-Late Cambrian location of the Ellsworth-Whitmore Mountains block. 相似文献
8.
J.-C. Rage 《Cretaceous Research》1981,2(1):65-84
Terrestrial vertebrates offer possibilities of reconstructing the migrations by land-routes followed during the late Cretaceous on the peri-Atlantic continents (North America, South America, Europe, Africa). South America and Africa were not separated before the Aptian. Later, migrations could still have occurred between Africa and South America during the late Cretaceous by a land-route (probably discontinuous) situated on the Rio Grande Rise-Walvis Ridge barrier; it is not impossible that some amphibia used this route. In Laurasia, two provinces were largely separated during the early part of the late Cretaceous: Euramerica and Asiamerica in the terminology of Cox (1974), (that is, Europe plus eastern North America and Asia plus western North America). During the latest Cretaceous, western North America became connected with Euramerica, but probably separated from Asia. During the latest Cretaceous, a route, probably terrestrial, permitted important faunal exchanges between South America and Laurasia; this connection was situated in the Caribbean region, perhaps where Central America is today. Limited faunal exchange occurred between Euramerica and North Africa. 相似文献
9.
《International Geology Review》2012,54(10):1118-1134
The fact that the magnetic pole has drifted during the course of geological time is a well established fact. The author endorses the agreement of paleomagnetic measurements with results of paleoclimatic reconstructions. Proving relative movements of continents on the basis of paleomagnetic data is impossible, as the accuracy of paleomagnetic measurements is very low, and permits determination of migrations of 2,000 km or more. To interpret the results of paleomagnetic measurements statistically, sufficient data is available only for North America, Western Europe, and the European portion of the U.S.S.R. A systematic error, proportional to time, has introduced an appreciable discrepancy between the European and North American data. The error is caused, in part, by the instability of specimens (due, among other factors, to magnetization introduced by succeeding magnetic fields). As a consequence, the resultant magnetization vector indicates a 10° to 15° shift toward the present magnetic field. There is insufficient data for all continents to use statistical methods, thereby introducing the possibilities of considerable accidental errors. Effects of pressure and chemical changes on the magnetization vector shift are not studied in detail. According to available geological data, no continental drift occurred in the case of India and China. The author also notes the discrepancies of paleomagnetic reconstruction.—Auth. English summ. 相似文献
10.
华北与扬子块体在中元古代拼合成中国古大陆，但自晚震旦世又分离成两大板块，各自有其发展历史，其间以商丹断裂为界，至晚三叠世完成最终对接、拼合、寒武纪时期华北南部陆缘区为活动大陆边缘，扬子北部陆缘区为被动大陆边缘，各自又分成若干隆凹相间的次级构造岩相带，晚寒武世从扬子北部陆缘区分离出中秦岭微板块，据岩相，古生物地理，并参考古地磁资料，再造了寒武纪古大陆及秦岭古海洋面貌。 相似文献
11.
寒武纪三叶虫生物地理区的一些问题 总被引：1，自引：0，他引：1
文内叙述寒武纪三叶虫分类、分布和分区。世界上有两个寒武纪生物地理区,一个是北区,另一个是南区。斜坡带的球接子类及少数多节类是世界性分布的,仅能视作任何一区内的生态小区。两区的分界在北非的北部、土耳其的南部,再向东连接天山的北部边缘及蒙古的南部边缘。从南欧寒武纪三叶虫的情况看,是海水深度频繁变化的结果。中国任何一个地区,既不属东冈瓦纳,也不属西冈瓦纳。 相似文献
12.
迄今为止,位于扬子地块的西北缘,夹持于扬子、华北、塔里木和羌塘—昌都地块之间呈倒三角形构造区块的巴颜喀拉褶皱带尚未有构造古地磁研究成果报导。为配合该区油气勘查与油气资源评价,并对构造区块定位提供定量数据,开展了松潘—阿坝地块的古地磁研究。采样区集中在西秦岭构造区南亚带(摩天岭和若尔盖)、中亚带(洮河)和巴颜喀拉构造区的马尔康复向斜带(巴颜喀拉褶皱区)4个微地块。采样地层单元主要为三叠系。共采集57个采点,376块岩心标本。通过对岩石样品测试数据的分析和计算,获得洮河、巴颜喀拉、摩天岭和若尔盖(后两者夹于前两者之间)4个微地块古地磁极极点位置:经度为191.4°E~202.9°E,纬度为49.5°N~58.5°N。洮河和巴颜喀拉两微地块在晚三叠世的古纬度同为26.2°N,表明晚三叠世这4个被断裂相隔的微地块已构成一个统一的较大的地块。洮河和巴颜喀拉地块在三叠纪时的古纬度变化分别从早三叠世的13.4°N和11.3°N向北移动到晚三叠世的26.2°N,同时在北向移动过程中从早三叠世至晚三叠世分别发生了约40°和16°的逆时针旋转。 相似文献
13.
A Review on the Taxonomic, Evolutionary and Phytogeographic Studies of the Lotus Plant (Nelumbonaceae: Nelumbo) 总被引：1，自引：0，他引：1
Nelumbo Adans. （Nelumbonaceae） is an important member of the early-diverging eudicots. It contains two extant species： N. nucifera Gaertn. （the Sacred lotus）, distributed in Asia and Australia and N. lutea Willd. （the American lotus）, occurring in North America. This paper reviews the taxonomic, evolutionary and phytogeographic studies of the genus Nelumbo, and also raises scientific questions about it in further paleobotanic research. There are about 30 fossil species of Nelumbo established since the Early Cretaceous. Based on fossil studies, the ancestors of the extant N. nucifera and N. lutea are respectively considered to be N. protospeciosa from the Eocene to Miocene of Eurasia, and N. protolutea from the Eocene of North American. However, molecular systematic studies indicate that N. nucifera and N. lutea are probably split from a common ancestor during the Late Miocene to Early Pliocene, or even the Pleistocene, rather than separate relicts from extinct species on different continents. The characters of lotus stomatal development, seedling morphology as well as its flowering, pollination and fertilization in air reveal that it evolves from the land plants. Fossil data of Nelumbo indicates that the genus first occurs in mid-latitude area of Laurasia in the Early Cretaceous, then becomes widespread in North America and Eurasia and expands into Africa and South America during the Late Cretaceous; the genus probably colonizes the Indian Subcontinent from Asia during the Early Eocene after the collision of India and the Asian plates; the genus becomes extinct in Europe, but survives in Asia and North America during the Quaternary Ice Age, and later forms the present East Asia and North Australia-North America disjunctive distribution. 相似文献
14.
A new reassembly of the continents around the North Atlantic Ocean is presented. The first criterion used for this reassembly is the identification of the structural framework related to the opening which consists of marginal fracture zones generated by offsets of the Rift. The Africa—North America, Eurasia—Greenland, Greenland—North America and Eurasia—North America adjustments are successively discussed. It is argued that the adjustments are best made at the 3000-meters isobath between Africa and North America and at the 2000-meters isobath for the younger rifts. The difference is attributed to subsidence and modification of continental margins with time. The importance of the Late Paleozoic tectonic phase in determining the subsequent pattern of Mesozoic rifting is emphasized. 相似文献
15.
Tectonic rotations in the Deseado Massif, southern Patagonia, during the breakup of Western Gondwana
Paleomagnetic investigation in the Deseado Massif, southern Patagonia, suggests that Triassic sedimentary rocks carry a latest Triassic to Jurassic remagnetization and that earliest Jurassic plutonic complexes carry a reversed polarity magnetization of thermoremanent origin. Despite uncertainties in the timing of the observed remanence in the Triassic rocks and the lack of paleohorizontal control on the plutonic complexes, comparison of the derived pole positions with the most reliable Late Triassic–Jurassic apparent polar wander paths indicates that the study areas underwent significant clockwise vertical-axis rotation. In contrast, paleomagnetic results from mid-Cretaceous rocks in the region indicate no rotation. The observed crustal rotations in the Deseado Massif are thus bracketed to have occurred between Jurassic and Early Cretaceous times, documenting southern Patagonian deformation during the breakup of Western Gondwana and then enlarging the regional record of clockwise rotations associated with this event. These results suggest a more complex than previously supposed tectonic evolution of this part of South America. 相似文献
16.
P. V. Crowhurst R. Maas K. C. Hill D. A. Foster C. M. Fanning 《Australian Journal of Earth Sciences》2013,60(1):107-122
New U–Pb zircon ages and Sr–Nd isotopic data for Triassic igneous and metamorphic rocks from northern New Guinea help constrain models of the evolution of Australia's northern and eastern margin. These data provide further evidence for an Early to Late Triassic volcanic arc in northern New Guinea, interpreted to have been part of a continuous magmatic belt along the Gondwana margin, through South America, Antarctica, New Zealand, the New England Fold Belt, New Guinea and into southeast Asia. The Early to Late Triassic volcanic arc in northern New Guinea intrudes high‐grade metamorphic rocks probably resulting from Late Permian to Early Triassic (ca 260–240 Ma) orogenesis, as recorded in the New England Fold Belt. Late Triassic magmatism in New Guinea (ca 220 Ma) is related to coeval extension and rifting as a precursor to Jurassic breakup of the Gondwana margin. In general, mantle‐like Sr–Nd isotopic compositions of mafic Palaeozoic to Tertiary granitoids appear to rule out the presence of a North Australian‐type Proterozoic basement under the New Guinea Mobile Belt. Parts of northern New Guinea may have a continental or transitional basement whereas adjacent areas are underlain by oceanic crust. It is proposed that the post‐breakup margin comprised promontories of extended Proterozoic‐Palaeozoic continental crust separated by embayments of oceanic crust, analogous to Australia's North West Shelf. Inferred movement to the south of an accretionary prism through the Triassic is consistent with subduction to the south‐southwest beneath northeast Australia generating arc‐related magmatism in New Guinea and the New England Fold Belt. 相似文献
17.
Gondwanaland origin, dispersion, and accretion of East and Southeast Asian continental terranes 总被引：3，自引：0，他引：3
East and Southeast Asia is a complex assembly of allochthonous continental terranes, island arcs, accretionary complexes and small ocean basins. The boundaries between continental terranes are marked by major fault zones or by sutures recognized by the presence of ophiolites, mélanges and accretionary complexes. Stratigraphical, sedimentological, paleobiogeographical and paleomagnetic data suggest that all of the East and Southeast Asian continental terranes were derived directly or indirectly from the Iran-Himalaya-Australia margin of Gondwanaland. The evolution of the terranes is one of rifting from Gondwanaland, northwards drift and amalgamation/accretion to form present day East Asia. Three continental silvers were rifted from the northeast margin of Gondwanaland in the Silurian-Early Devonian (North China, South China, Indochina/East Malaya, Qamdo-Simao and Tarim terranes), Early-Middle Permian (Sibumasu, Lhasa and Qiangtang terranes) and Late Jurassic (West Burma terrane, Woyla terranes). The northwards drift of these terranes was effected by the opening and closing of three successive Tethys oceans, the Paleo-Tethys, Meso-Tethys and Ceno-Tethys. Terrane assembly took place between the Late Paleozoic and Cenozoic, but the precise timings of amalgamation and accretion are still contentious. Amalgamation of South China and Indochina/East Malaya occurred during the Early Carboniferous along the Song Ma Suture to form “Cathaysialand”. Cathaysialand, together with North China, formed a large continental region within the Paleotethys during the Late Carboniferous and Permian. Paleomagnetic data indicate that this continental region was in equatorial to low northern paleolatitudes which is consistent with the tropical Cathaysian flora developed on these terranes. The Tarim terrane (together with the Kunlun, Qaidam and Ala Shan terranes) accreted to Kazakhstan/Siberia in the Permian. This was followed by the suturing of Sibumasu and Qiangtang to Cathaysialand in the Late Permian-Early Triassic, largely closing the Paleo-Tethys. North and South China were amalgamated in the Late Triassic-Early Jurassic and finally welded to Laurasia around the same time. The Lhasa terrane accreted to the Sibumasu-Qiangtang terrane in the Late Jurassic and the Kurosegawa terrane of Japan, interpreted to be derived from Australian Gondwanaland, accreted to Japanese Eurasia, also in the Late Jurassic. The West Burma and Woyla terranes drifted northwards during the Late Jurassic and Early Cretaceous as the Ceno-Tethys opened and the Meso-Tethys was destroyed by subduction beneath Eurasia and were accreted to proto-Southeast Asia in the Early to Late Cretaceous. The Southwest Borneo and Semitau terranes amalgamated to each other and accreted to Indochina/East Malaya in the Late Cretaceous and the Hainanese terranes probably accreted to South China sometime in the Cretaceous. 相似文献
18.
New and published paleomagnetic measurements from Trans Altai and South Gobi zones in south Mongolia document large tectonic motions in between Late Carboniferous and Triassic. Magnetic inclinations confirm equatorial position of south Mongolian terranes in Late Carboniferous–Permian times. The evolution of magnetic declinations indicates 90° anticlockwise rotation in between latest Carboniferous and Early Triassic of all studied tectonic units around the Eulerian pole located close to axis of Mongolian orocline. The anticlockwise rotation continues in Triassic being accompanied by a major drift to the north. The structural and published geochronological data suggest Carboniferous E–W shortening of the whole region resulting in N–S trend of all continental and oceanic geological units followed by orthogonal N–S shortening during Late Permian to Early Jurassic. Both paleomagnetic and geological data converge in a tectonic model of oroclinal bending of Mongolian ribbon continent, westerly back arc oceanic domain and Mongol–Okhotsk subduction zone to the east. The oroclinal bending model is consistent with the coincidence of the Eulerian pole of rotation with the structural axis of Mongolian orocline. In addition, the Mesozoic collisional tectonics is reflected by late remagnetizations due to formation of wide deformation fronts and hydrothermal activity. 相似文献
19.
中国冈瓦纳研究的兴起及与板块构造有关的几个关键古生物地理问题 总被引：4，自引：0，他引：4
<正> 几年前,多数中国地质学家还认为对冈瓦纳研究与中国地质关系不大。虽然新疆早有冈瓦纳型二、三叠纪二齿兽类的发现,人们也只在寻找南、北大陆间的“陆桥”上思考。七十年代中期,北喜马拉雅发现了晚古生代冰海沉积和Stepanoviella冷水生物群以及舌羊齿植物群,这就成了中国冈瓦纳研究的真正开端。但此后许多人仍然认为,在中国只有藏南一隅属于冈瓦纳大陆,雅鲁藏布江—印度河则是南、北大陆的分界。通过近几年中国地质学家以及与法国地质学家的合作研究,发现青藏高原中、北部(拉萨、羌塘地区)与东部(滇西),仍有同时代冰 相似文献
20.
The Mesozoic evolution of the Mongol-Okhotsk Ocean (MOO) has significantly affected the configuration of the modern Asian continent. Although a scissor-like closure of the MOO has long been proposed, when and how the MOO closed are still hotly debated, especially the timing of initial closure of the MOO in its western segment, hindering our understanding of both the evolution of the MOO and tectonics of the northern Asian continent. In order to uncover the timing of initial closure of the MOO, we performed a multidisciplinary study in sedimentology, detrital zircon U-Pb dating and paleomagnetic on the Late Triassic clastic strata from the Tarvagatay Block and the Amuria Block (AMB) on the both sides of the Mongol-Okhotsk Suture. The upper Triassic strata on both sides of the suture were dominated by plant fossil-bearing alluvial-fluvial facies sediments, which unconformably overlain pre-Triassic geological units, indicating a terrestrial setting after the closure of the MOO. Detrital zircon U-Pb dating results revealed consistent age distribution patterns for samples from both sides of the suture with a predominant peak at ∼253–251 Ma and a secondary peak at ∼359–357 Ma, representing two main arc magmatic events during the bidirectional subduction of the MOO in the Late Devonian-Early Carboniferous and Late Permian-Early Triassic. Coeval Late Triassic paleomagnetic poles were obtained from the northern AMB and Tarvagatay Block, revealing a comparable paleolatitude of the AMB (∼31–33°) and Tarvagatay Block (∼32–34°) in the Late Triassic, arguing for that the western segment of the MOO should have closed at the Late Triassic. The compilation of sedimentology, detrital zircon U-Pb dating, magmatic and paleomagnetic evidence provides integrated constraints on the Late Triassic initial closure of the MOO in its western segment. 相似文献