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1.
南海南、北陆缘中生代构造层序及其沉积环境 总被引：1，自引：0，他引：1
新生代海底扩张,使南海陆缘分为南、北两部分。南部礼乐地块与南海北缘在扩张之前构成了统一的活动陆缘。通过对南、北陆缘的钻井研究和井旁地震剖面解释,发现二者的中生界均具有4 个地震层序及3 个构造层。南北陆缘构造层序及物源分析表明,早白垩世礼乐地块与南海北缘曾发生碰撞拼贴。早白垩世的南海北缘地区沉积环境由海陆过渡相向陆相演化,相应的礼乐地区是由浅海相向滨海相演化,二者反映出相同的向上变浅旋回,说明在南、北陆缘拼贴之后,两者具有了统一的构造沉积背景。到晚白垩世末,两区均隆升为陆,且遭受剥蚀; 南海北缘地区上白垩统部分被剥蚀,而距俯冲边界更近的礼乐地区上白垩统则被剥蚀殆尽。 相似文献
2.
《International Geology Review》2012,54(1):93-110
The origin and continuity of Phanerozoic lithostratigraphic terranes in southern and Baja California remain an unsolved issue in Cordilleran tectonics. We present data from eight detrital zircon samples collected across the southern extent of the Peninsular Ranges that help constrain the provenance of detritus and the depositional ages of these basement units. Detrital zircon signatures from units in the eastern Peninsular Ranges correlate with Palaeozoic passive margin assemblages in the southwestern North American Cordillera. Units in the central belt, which consists of Triassic–Jurassic metasedimentary turbidite assemblages that probably deformed in an accretionary prism setting, and Cretaceous metasedimentary and metavolcanic units that represent the remnants of a continental margin arc, were derived from both proximal and more distal sources. The westernmost units, which are locally structurally interleaved with the Triassic through Cretaceous units of the central belt, are Cretaceous deposits that represent a series of collapsed basin complexes located within and flanking the Cretaceous Alisitos volcanic island arc. Cretaceous intra-arc units show little influx of cratonal material until approximately 110 Ma, whereas coeval sediments on the northern and eastern flanks of the Alisitos arc contain abundant cratonal detritus. Intra-arc strata younger than approximately 110 Ma contain large amounts of Proterozoic and older detrital zircons. These data suggest that basins associated with the Alisitos arc were either too distant or somehow shielded from North American detritus before 110 Ma. In the case of the former, increased influx of continental detritus after 110 Ma would support a tectonic model in which the arc was separated from North America by an ocean basin and, as the arc approached the continent, associated depositional centres were close enough to receive input from continental sources. 相似文献
3.
The Upper Triassic Langjiexue Group, exposed south of the Yarlung-Zangbo suture zone in south Tibet, shows sedimentary features different from typical Tethyan Himalayan successions, and its origin is controversial. In this article we combine field observations with paleocurrent, petrologic, geochronological and isotopic data to determine the provenance of Langjiexue sandstones. These middle to distal deep-sea-fan turbidites are crosscut by Lower Cretaceous diabase sills and dikes generated during rifting of India from Gondwana, indicating that the Langjiexue Group was originally deposited along or adjacent to the northern passive continental margin of India. Flute casts at the base of turbidite beds indicate mostly WNW-ward paleocurrents, pointing to provenance from a source located east of the depositional area. Common volcanic fragments and plagioclase grains together with a cluster of 400–200-Ma-aged magmatic zircons with uniform εHf(t) values from − 5 to + 10 are incompatible with any nearby sources, including the Qiantang Block, the Lhasa Block or the India subcontinent, and indicate instead supply from a long-lived magmatic-arc terrane. Considering what is known about Late Triassic paleogeography, a plausible source for Langjiexue sediments is represented by the Gondwanide Orogen, generated during subduction of the pan-Pacific oceanic lithosphere beneath southeastern Gondwana. This scenario is supported by the age range and Hf isotopic signatures of Late Paleozoic–Early Mesozoic zircons contained in Langjiexue turbidites as in coeval turbidites exposed in western Myanmar. New data are needed to confirm/falsify the existence of a thousand-km-long sediment-routing system similar to the modern Amazon, which – sourced in a cordillera-type orogen rising along the southeastern margin of Gondwana – crossed an entire continent to feed turbiditic fans now exposed from western Myanmar to the northern Tethys Himalaya. 相似文献
4.
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
5.
A new large theropod, Orkoraptor burkei nov. gen. et nov. sp., from the Upper Cretaceous (Maastrichtian) Pari Aike Formation of southern Patagonia is based on a postorbital, quadratojugal, coronoid?, several teeth, an atlantal intercentrum and neurapophysis, two caudal vertebrae, and the proximal half of tibia. This new theropod exhibits characteristics of maniraptorans (i.e., coelurosaurians more derived than tyrannosaurids) including an upturned rostral process of the postorbital, the caudoventral corner of which is widely concave. Furthermore, teeth without denticles and carina in the mesial margin resemble the condition of the maniraptoran clades Compsognathidae and Deinonychosauria. The new Patagonian theropod differs from other coelurosaurians (Ornithomimosauria, Compsognathidae, Alvarezsauridae, Dromaeosauridae, Aves) in having caudal vertebrae with a single pair of small pleurocoels on each side, and in having a median depression flanked by two longitudinal and narrow furrows on each tooth. Orkoraptor represents one of the southernmost carnivorous dinosaurs yet found in South America and adds valuable information about the diversification of tetanuran theropods in Gondwana. 相似文献
6.
Previous authors have related the Late Cretaceous/early Tertiary subsidence of the Mississippi embayment to the opening of the Gulf of Mexico, but the Gulf opened earlier in Triassic/Jurassic time. We offer an alternative hypothesis that development of the embayment was coeval with the passage of the Mississippi Valley graben system over the Bermuda hotspot about 90 Ma. Several lines of evidence of significant uplift of the embayment axis accompanying mid-Cretaceous magmatism and prior to Late Cretaceous subsidence support this proposal.
First, reactivation of the Pascola arch in the northern embayment is recorded by flanking deposits of basal Upper Cretaceous gravel. Second, beneath a regional mid-Cretaceous unconformity, subcrops of Jurassic and Early Cretaceous strata define a pronounced southwest-plunging arch in the southern embayment. This arch is collinear with an arch revealed in Paleozoic rocks after restoration to mid-Cretaceous structural geometries. Third, a deep weathering profile on mid-Cretaceous alkalic plutons along the western embayment margin is nonconformably overlain by Paleocene sediments, and rapid mid-Cretaceous cooling of these intrusions has been interpreted from apatite fission tracks. Moreover, exploratory holes along the embayment axis encountered similar weathered alkalic intrusions nonconformably overlain by basal Upper Cretaceous strata. Fourth, there was an anomalous influx of clastic sediment into the northern Gulf of Mexico during mid-Cretaceous time, and subsequent clastic facies patterns suggest the Mississippi River drainage began to enter the Gulf in the Late Cretaceous.
Passage of the Mississippi Valley graben over the Bermuda hotspot during elevated hotspot activity of Cretaceous time may have significantly weakened the previously rifted lithosphere. Rifted continental margin at Charleston, South Carolina, also passed over this hotspot in latest Cretaceous time. Similarly, the St. Lawrence rift system passed over the Great Meteor hotspot during the Cretaceous. It is important to note that these rift systems are the principal loci of strong seismicity in eastern North America, and thus weakening by increased Cretaceous hotspot activity may be an important common factor for these seismic rift zones. 相似文献
7.
Upper Cretaceous deposits in Mongolia, Chinese Inner Mongolia, and, more recently, southern China, have yielded individually rich and taxonomically diverser lizard assemblages. Here we describe the remains of a new terrestrial lizard, Asprosaurus bibongriensis gen. et sp. nov., from the Upper Cretaceous of South Korea. It represents the first record of a Mesozoic lizard from the Korean Peninsula and, although incomplete, is exceptional in its very large size. Characters of the mandible support attribution to crown-group Anguimorpha, with the closest similarities being to monstersaurs, the group represented today by the venomous North American Beaded lizard and Gila monster, genus Heloderma. This group is well-represented in the Upper Cretaceous fossil record in of eastern Asia, and the remains of large monstersaurs have been recovered from several dinosaur egg localities, suggesting dietary preferences similar to those of the living genus. The new Korean lizard, recovered from the Boseong Bibong-ri Dinosaur Egg Site, fits the same pattern. 相似文献
8.
With the aim of constraining the influence of the surrounding plates on the Late Paleozoic–Mesozoic paleogeographic and tectonic evolution of the southern North China Craton (NCC), we undertook new U–Pb and Hf isotope data for detrital zircons obtained from ten samples of upper Paleozoic to Mesozoic sediments in the Luoyang Basin and Dengfeng area. Samples of upper Paleozoic to Mesozoic strata were obtained from the Taiyuan, Xiashihezi, Shangshihezi, Shiqianfeng, Ermaying, Shangyoufangzhuang, Upper Jurassic unnamed, and Lower Cretaceous unnamed formations (from oldest to youngest). On the basis of the youngest zircon ages, combined with the age-diagnostic fossils, and volcanic interlayer, we propose that the Taiyuan Formation (youngest zircon age of 439 Ma) formed during the Late Carboniferous and Early Permian, the Xiashihezi Formation (276 Ma) during the Early Permian, the Shangshihezi (376 Ma) and Shiqianfeng (279 Ma) formations during the Middle–Late Permian, the Ermaying Group (232 Ma) and Shangyoufangzhuang Formation (230 and 210 Ma) during the Late Triassic, the Jurassic unnamed formation (154 Ma) during the Late Jurassic, and the Cretaceous unnamed formation (158 Ma) during the Early Cretaceous. These results, together with previously published data, indicate that: (1) Upper Carboniferous–Lower Permian sandstones were sourced from the Northern Qinling Orogen (NQO); (2) Lower Permian sandstones were formed mainly from material derived from the Yinshan–Yanshan Orogenic Belt (YYOB) on the northern margin of the NCC with only minor material from the NQO; (3) Middle–Upper Permian sandstones were derived primarily from the NQO, with only a small contribution from the YYOB; (4) Upper Triassic sandstones were sourced mainly from the YYOB and contain only minor amounts of material from the NQO; (5) Upper Jurassic sandstones were derived from material sourced from the NQO; and (6) Lower Cretaceous conglomerate was formed mainly from recycled earlier detritus.The provenance shift in the Upper Carboniferous–Mesozoic sediments within the study area indicates that the YYOB was strongly uplifted twice, first in relation to subduction of the Paleo-Asian Ocean Plate beneath the northern margin of the NCC during the Early Permian, and subsequently in relation to collision between the southern Mongolian Plate and the northern margin of the NCC during the Late Triassic. The three episodes of tectonic uplift of the NQO were probably related to collision between the North and South Qinling terranes, northward subduction of the Mianlue Ocean Plate, and collision between the Yangtze Craton and the southern margin of the NCC during the Late Carboniferous–Early Permian, Middle–Late Permian, and Late Jurassic, respectively. The southern margin of the central NCC was rapidly uplifted and eroded during the Early Cretaceous. 相似文献
9.
Late Jurassic-Early Cretaceous Northern Qaidam Basin, NW China: Implications for the earliest Cretaceous intracontinental tectonism 总被引：4，自引：0，他引：4
Lei Wu Ancheng Xiao Liqun WangZhongyan Shen Suping ZhouYuanzhong Chen Liang Wang Dong LiuJunya Guan 《Cretaceous Research》2011,32(4):552-564
Formation of Mesozoic western China, which was dominated by tectonic amalgamation along its southern margin and associated intracontinental tectonisms, holds a key for interpreting the succedent Cenozoic evolution. This paper presents new data including lithology, sedimentary facies, stratigraphic contact, seismic interpretation and paleo-structures within the Upper Jurassic-Lower Cretaceous strata in the northern Qaidam Basin, NW China. These data all account for a contractional tectonic deformation in the earliest Cretaceous. The South Qilian Shan, according to the sedimentary features and provenance analysis, reactivated and exhumated during the deformation, controlling the deposition of the Lower Cretaceous sequences. A simplified model for the Late Jurassic-Early Cretaceous paleogeography and tectonics of the northern Qaidam Basin is accordingly proposed. The results also support a ∼25° clockwise rotation of the Qaidam Basin since the Early Cretaceous and a more accurate Mesozoic evolution process for the basin. This earliest Cretaceous deformation, associated with the reactivation of the South Qilian Shan at the time, are part of the intracontinental tectonisms in central Asia during the Mesozoic, and probably driven by both the closure of the Mongol-Okhostk Ocean to the north and the collision of the Lhasa and the Qiangtang blocks to the south. 相似文献
10.
《International Geology Review》2012,54(7):594-616
The Mesozoic rocks of Cuba are a key element in reconstructing the geological history of the Mesoamerican (Gulf of Mexico and the Caribbean) area. Four different Jurassic-Cretaceous sections are recorded in Cuba, including three from tectonostratigraphic terranes. From north to south they include the following: (1) a portion of the Mesozoic passive margin of North America, with outstanding zonality, especially in the Middle Cretaceous of central Cuba; (2) the Northern Ophiolitic Belt, also with Upper Jurassic-Lower Cretaceous rocks, which is a huge melange; all members of the ophiolitic suite are tectonically mingled along the northern part of Cuba; (3) the Volcanic Arc Terrane, mainly composed of Cretaceous volcanics, with older, primarily tholeiitic lavas (Aptian-Albian) and younger (Cenomanian-Campanian) calc-alkaline pyroclastics and lavas, with many sedimentary interbeds; Albian-Cenomanian deposits with a few volcanics separate both sequences, and an Upper Jurassic-Neocomian amphibolitic basement of the volcanic arc is present in some places; and (4) the Southern Metamorphic Terranes that contain rocks of a Mesozoic passive margin that experienced several metamorphic episodes during the Cretaceous. The welding of these terranes occurred during the Cretaceous, and ended in the late Campanian and Maastrichtian. In the south, the volcanic terrane was emplaced upon the Southern Metamorphic Terranes, while in the north the volcanics and ophiolites were thrust over the Mesozoic margin of North America. In western Cuba, the beds are strongly deformed and thrust to the north or northwest. Nappes also are present in north-central Cuba, but an essentially Bahamian platform stratigraphy is present. Although the passive paleomargin of North America was deformed in the latest Cretaceous, this event is masked by the early Tertiary Cuban orogeny. It is suggested that the Jurassic stratigraphy of the Southern Metamorphic Terranes shares features with the southern North American passive margin in western Cuba. The position of the Southern Metamorphic Terranes south of the ophiolite and arc terrane therefore does not support the idea of a Pacific origin for the Cretaceous island arcs of the Greater Antilles, but instead suggests that a proto-Caribbean genesis is more plausible. 相似文献
11.
地震资料显示南海北部中生界发育褶皱和逆冲断层等挤压构造, 但目前对其成因仍存在争议.通过对南海北部珠江口盆地东南部陆坡的二维地震剖面进行研究, 发现在云荔低隆起-兴荔凸起-兴宁凹陷一带存在2条近NW-SE走向并往NE方向逆冲的逆断层, 在东沙隆起南部有2条近南-北走向并具有压扭性质的走滑断层, 上述4条断层的平面延伸距离分别约为130、110、55和58 km.综合分析可知, 现今位于南海南部的礼乐-巴拉望地块经中侏罗世-早白垩世与华南陆缘发生软碰撞后, 在晚白垩世与华南陆缘在现今荔湾-兴宁凹陷一带进行最后的"焊接缝合", 而上述4条断层可作为该次"焊接缝合"的间接证据.由于太平洋向华南的俯冲板片在晚白垩世发生了后撤, 华南大陆边缘在晚白垩世末开始张裂之前可能整体为区域均衡抬升、局部陆-陆碰撞缝合的构造格局. 相似文献
12.
A total of 81 samples (244 specimens) from Upper Cretaceous Indus Molasse and Middle to Upper Cretaceous Dras Flyschoids of the Indus-Tsangpo suture zone in Ladakh (northwest Himalaya) has been studied by thermal demagnetization methods.Both formations showed a characteristic magnetization component indicative for equatorial to low northern palaeolatitudes of acquisition. Similar palaeolatitudes have been obtained before from secondary magnetization components of Early Tertiary age in the Ladakh Intrusives and in the Tibetan Sedimentary Series of central Nepal. The present characteristic components are interpreted likewise as secondary magnetizations which stabilized between 50 and 60 m.y. ago, during Greater India's collision with Asia's southern margin.The Dras Flyschoids show another magnetic component which, in case of primary origin, indicates acquisition at a low southern palaeolatitude. If correct, this interpretation supports recent suggestions for Late Cretaceous obduction of an island arc on Greater India's northern margin. 相似文献
13.
14.
Here we describe an isolated tooth of a metriorhynchid crocodylomorph from the Hybla Formation (Aptian, Lower Cretaceous) of Rocca Chi Parra quarry (Montagna Grande, Calatafimi, Trapani Province), Sicily, Italy. The specimen shares with the Upper Jurassic taxon Plesiosuchus manselii a mediolaterally compressed conical tooth crown, noticeable lingual curvature, mesial and distal carinae with microscopic, rectangular contiguous denticles, strong distal curvature of the mesial margin, and the presence of weak 'carinal flanges' on the labial and lingual surfaces (which are preeminent at the mid-crown). This suite of morphologies is also present in an unnamed Valanginian (Lower Cretaceous) plesiosuchinan from France. However, the Sicilian tooth differs from these taxa in having more pronounced carinae, and faint apicobasally aligned enamel ridges. It also differs from P. manselii in having more extensive 'carinal flanges' on the labial surface. The specimen extends the known geological range of Metriorhynchidae and Thalattosuchia by approximately 7–8 million years. This overturns previous hypotheses of Metriorhynchidae becoming extinct early in the Early Cretaceous. 相似文献
15.
The Western Cordillera of Colombia (WCC) is part of the Basic Igneous Complex (BIC), which is one of the world's largest ophiolitic complexes, extending from Costa Rica through Panama and Colombia to Ecuador. Major and trace element data on 32 volcanic rocks from the central and northern parts of the Western Cordillera are presented; no data have been available to date for volcanic rocks from the northern parts of the Western Cordillera. Petrographical and geochemical investigations show that the rocks are altered and have undergone low-grade metamorphism. The subalkaline rocks are represented by tholeiitic basalts, calc-alkaline basic andesites, andesites, and one dacite. It is concluded that a mature oceanic island arc existed in the Cretaceous, in what is now the northern part of the Western Cordillera. The tectonics of the region, particularly the intensive imbrication of the chain, indicates the presence of a paleo-subduction zone with an oceanic island arc that accreted on the old continental margin. These new data, combined with new and previous data from the central part of the BIC of Colombia, suggest that volcanic rocks of the Western Cordillera can be interpreted as allochthonous slabs. These slabs were imbricated with back-arc and fore-arc sediments and tonalitic bodies during the closing of a back-arc basin in northwestern South America and accretion of an oceanic island arc. Oblique subduction accreted these different areas to the continental margin during Late Cretaceous and early Tertiary times. Two plate-tectonic models are proposed: a) development of the calc-alkaline volcanic rocks in the northern parts of the Western Cordillera, separated by tholeiitic rocks, formed along a transform fault represented by the tholeiitic basalts of the central and southern parts of the Western Cordillera; or b) development of an oceanic island arc along the Cretaceous continental margin of northwestern South America. In the central and southern parts of this island arc, accretion took place early and therefore only an island-arc tholeiitic suite was formed. 相似文献
16.
V. S. Vishnevskaya 《Stratigraphy and Geological Correlation》2010,18(6):607-634
Radiolarian assemblages from the Upper Cretaceous carbonate-cherty deposits of the East European platform are analyzed. Biostratigraphic
subdivisions ranked as radiolarian beds are distinguished in sediments of the Moscow syneclise, Voronezh anteclise, and the
Ul’yanovsk-Saratov depression. The correlation between biostratigraphic beds established in three tectonic structures and
variants of their coordination with radiolarian subdivisions in southern and northern areas of Russia are considered. The
key importance of radiolarians for the subdivision and correlation of the Upper Cretaceous cherty deposits is demonstrated. 相似文献
17.
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
18.
北美东部被动大陆边缘是世界上最古老的完整被动大陆边缘之一,是研究被动大陆边缘发育演化的天然实验室。本文在大量国外研究成果的基础上,应用盆地构造解析方法,深入研究了北美东部被动大陆边缘盆地群的地质结构和构造演化特征,并揭示了盆地群的油气地质规律。研究认为,北美东部盆地群沉积充填和不整合面发育具有明显的分段性和差异性。以区域不整合面为界,不同段盆地可划分为不同的构造层:南段盆地可划分为两套构造层;中段南部盆地可划分为3套构造层;中段北部盆地可划分为4套构造层;而北段盆地可划分为5套构造层。盆地群整体经历了陆内裂谷—陆间裂谷—被动大陆边缘的演化过程,但不同段盆地的构造演化具有明显的分段性和迁移性:晚三叠世沉降中心位于南段盆地;早侏罗世初期迁移至中段盆地,南段大陆开始裂解;中侏罗世逐渐迁移至北段盆地,中段大陆开始裂解;早白垩世晚期,北段大陆开始裂解。受持续的抬升剥蚀及大西洋岩浆活动省的联合作用,南段盆地和中段大多数盆地缺乏油气保存条件;斯科舍盆地和大浅滩盆地是主要的含油气盆地,以上侏罗统烃源岩为主,主要发育断层—背斜圈闭和盐体刺穿圈闭,整体表现为“自生自储”和“下生上储”的特征。 相似文献
19.
During the Cambrian, two types of continental margins occurred around Gondwana. The eastern margin (Antarctica, Australia and southern South America) was characterized by a narrow continental shelf with a steep slope separating the shallow water environment from a deep-oceanic one accompanied by mafidultramafic volcanics. The western margin was characterized by a wider continental shelf, probably passing gradually to an unknown outer basin. This comprised three main domains: the Asiatic shelf, composed of distinct cratonic blocks, presumably separated from each other by deeper-water/ volcanic intracontinental basins; the European shelf, characterized by the development of shallow intracontinental siliciclastic basins; and the Americanc-African shelf, morphologically and depositionally uniform. The distinction of these two Gondwana continental margins expresses their different geodynamic behaviour during Cambrian extensional tectonics. In fact, the sedimentary/palaeogeographic evolution, suggests the establishment of an active Pacific-like margin in the eastern domain, and the tentative establishment of a divergent Atlantic-like margin, in the westem one. 相似文献
20.
In order to reconstruct tectonic evolution history of the southern margin of Asia (i.e., Lhasa terrane) before the India-Asia collision, here we present a comprehensive study on the clastic rocks in the southern Lhasa terrane with new perspectives from sedimentary geochemistry, detrital zircon geochronology and Hf isotope. Clasts from the Jurassic-Early Cretaceous sedimentary sequences (i.e., Yeba and Chumulong Formations) display high compositional maturity and experienced moderate to high degree of chemical weathering, whereas those from the late Early-Late Cretaceous sequences (Ngamring and Shexing Formations) are characterized by low compositional maturity with insignificant chemical weathering. Our results lead to a coherent scenario for the evolution history of the Lhasa terrane. During the Early-Middle Jurassic (∼192-168Ma), the Lhasa terrane was speculated to be an isolated geological block. The Yeba Formation is best understood as being deposited in a back-arc basin induced by northward subduction of the Neo-Tethys ocean with sediments coming from the interiors of the Lhasa terrane. The Middle Jurassic-Early Cretaceous Lhasa-Qiangtang collision resulted in the formation of a composite foreland basin with southward-flowing rivers carrying clastic materials from the uplifted northern Lhasa and/or Qiangtang terranes. During the late Early-Late Cretaceous (∼104-72Ma), the Gangdese magmatic arc was uplifted rapidly above the sea level, forming turbidites (Ngamring Formation) in the Xigaze forearc basin and fluvial red beds (Shexing Formation) on the retro-arc side. At the end of Late Cretaceous, the Lhasa terrane was likely to have been uplifted to high elevation forming an Andean-type margin resembling the modern South America before the India-Asia collision. 相似文献