首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 265 毫秒
1.
During the Mesozoic, the active southern margin of Eurasia was the site of several accretion and collision events that fit into a framework of convergence between Eurasia and advancing (peri-) Gondwanan units. Far-field effects of the Mesozoic Mongol–Okhotsk and Cimmerian orogenies have been recorded deep within the interior of Eurasia. Convergence finally culminated in the massive India–Eurasia continent–continent collision in the Early Cenozoic. This collision, continued convergence between both continents, and resulting ongoing indentation of India into Eurasia have dominated the geological, tectonic and geodynamic evolution of Eurasia. Amongst others, distant effects of these events have reactivated an array of mobile belts in Central Asia. Apatite fission-track dating and thermal history modeling performed on samples from the Kyrgyz Tien Shan and Siberian Altai Mountains record both Mesozoic deformation and Cenozoic reactivation of intracontinental Eurasia. The onset of the building and growth of the modern Tien Shan and Altai orogens is constrained to the Late Miocene and Pliocene, with a likely trend of activity younger towards the north. This would underscore the general model that deformation related to India–Eurasia convergence was progressively propagated northwards through Central Asia via the inherited structural fabric of the Eurasian crust.  相似文献   

2.
The complex crustal structure of the Tien Shan has a strong impact on the distribution of strain induced by the India–Eurasia collision, with intracontinental deformation in Eurasia’s interior as a distant effect. The northward propagation of the India–Eurasia deformation front is suggested by the rejuvenation of mountain ranges and intermittent intramontane basins. The Tien Shan basement is formed by the rigid, heterogeneous Precambrian blocks (microcontinents) of Tarim, Issyk-Kul (or Central Tien Shan) and Aktyuz-Boordin, surrounded by a ‘soft’ matrix of Paleozoic accretion–collision belts. The Kyrgyz Tien Shan Mountains are situated between the active structures of the Tarim Plate and the Pamir indenter (south), and the stable Kazakhstan Shield (north). Underplating by the Tarim Plate and thrusting by the Pamirs are responsible for the building of the Cenozoic Tien Shan, the reactivation of its inherited structural fabric and the tectonic layering of the upper lithosphere underlying the area. Large earthquakes (M > 6) delineate the northern and southern margins of the Issyk-Kul microcontinent, indicating that crustal heterogeneity influenced the location of active structures in the northern Kyrgyz Tien Shan.  相似文献   

3.
The Chinese Tien Shan range is a Palaeozoic orogenic belt which contains two collision zones. The older, southern collision accreted a north-facing passive continental margin on the north side of the Tarim Block to an active continental margin on the south side of an elongate continental tract, the Central Tien Shan. Collision occurred along the Qinbulak-Qawabulak Fault (Southern Tien Shan suture). The time of the collision is poorly constrained, but was probably in in the Late Devonian-Early Carboniferous. We propose this age because of a major disconformity at this time along the north side of the Tarim Block, and because the Youshugou ophiolite is imbricated with Middle Devonian sediments. A younger, probably Late Carboniferous-Early Permian collision along the North Tien Shan Fault (Northern Tien Shan suture) accreted the northern side of the Central Tien Shan to an island arc which lay to its north, the North Tien Shan arc. This collision is bracketed by the Middle Carboniferous termination of arc magmatism and the appearance of Late Carboniferous or Early Permian elastics in a foreland basin developed over the extinct arc. Thrust sheets generated by the collision are proposed as the tectonic load responsible for the subsidence of this basin. Post-collisional, but Palaeozoic, dextral shear occurred along the northern suture zone, this was accompanied by the intrusion of basic and acidic magmas in the Central Tien Shan. Late Palaeozoic basic igneous rocks from all three lithospheric blocks represented in the Tien Shan possess chemical characteristics associated with generation in supra-subduction zone environments, even though many post-date one or both collisions. Rocks from each block also possess distinctive trace element chemistries, which supports the three-fold structural division of the orogenic belt. It is unclear whether the chemical differences represent different source characteristics, or are due to different episodes of magmatism being juxtaposed by later dextral strike-slip fault motions. Because the southern collision zone in the Tien Shan is the older of the two, the Tarim Block sensu stricto collided not with the Eurasian landmass, but with a continental block which was itself separated from Eurasia by at least one ocean. The destruction of this ocean in Late Carboniferous-Early Permian times represented the final elimination of all oceanic basins from this part of central Asia.  相似文献   

4.
Lake Issyk-Kul occupies a large Late Mesozoic–Cenozoic intramontane basin between the mountain ranges of the Northern Kyrgyz Tien Shan. These ranges are often composed of granitoid basement that forms part of a complex mosaic assemblage of microcontinents and volcanic arcs. Several granites from the Terskey, Kungey, Trans-Ili and Zhetyzhol Ranges were dated with the zircon U/Pb method (SHRIMP, LA-ICP-MS) and yield concordant Late Ordovician–Silurian (~ 456–420 Ma) emplacement ages. These constrain the “Caledonian” accretion history of the Northern Kyrgyz Tien Shan in the amalgamated Palaeo-Kazakhstan continent. The ancestral Tien Shan orogen assembled in the Early Permian when final closure of the Turkestan Ocean ensued collision of Palaeo-Kazakhstan and Tarim. A Late Palaeozoic structural basement fabric formed and Middle–Late Permian post-collisional magmatism added to crustal growth of the Tien Shan. Permo‐Triassic cooling (~ 300–220 Ma) of the ancestral Tien Shan was unraveled using 40Ar/39Ar K-feldspar and titanite fission-track (FT) thermochronology on the Issyk-Kul granitoids. Apatite thermochronology (FT and U–Th–Sm/He) applied to the broader Issyk-Kul region elucidates the Meso-Cenozoic thermo-tectonic evolution and constrains several tectonic reactivation episodes in the Jurassic, Cretaceous and Cenozoic. Exhumation of the studied units occurred during a protracted period of intracontinental orogenesis, linked to far-field effects of Late Jurassic–Cretaceous accretion of peri-Gondwanan blocks from the Tethyan realm to Eurasian. Following a subsequent period of stability and peneplanation, incipient building of the modern Tien Shan orogen in Northern Kyrgyzstan started in the Oligocene according to our data. Intense basement cooling in distinct reactivated and fault-controlled sections of the Trans-Ili and Terskey Ranges finally pinpoint important Miocene–Pliocene (~ 22–5 Ma) exhumation of the Issyk-Kul basement. Late Cenozoic formation of the Tien Shan is associated with ongoing indentation of India into Eurasia and is a quintessential driving force for the reactivation of the entire Central Asian Orogenic Belt.  相似文献   

5.
Apatite fission-track (AFT) thermochronological modeling as a diagnostic tool for periods of stability (peneplanation) and tectonic activity (orogeny) has been broadly used in tectonic studies of Central Asia in recent years. We discuss more than 100 AFT ages of samples from the Kyrgyz Tien Shan and Altai and compare them with AFT data from northern Kazakhstan. Geological, geomorphological, and AFT data indicate intense activity in the Late Cenozoic Eurasian continental interior. The impact from the India-Eurasia collision on the northern Tien Shan, Altai, and northern Kazakhstan regions showed up at 11, 5, and 3 Ma, respectively, as a result of stress propagation into the continent, with the ensuing reactivation and mountain growth. We hypothesize that a distant effect of the Late Cenozoic India-Eurasia collision was to rejuvenate Paleozoic fault zones and to deform the Mesozoic sedimentary cover north of the collision front as far as the West Siberian Plate. The reactivation facilitated formation of tectonic oil and gas traps. The activity in northern Central Asia under the effect of the Indian indentation into Eurasia appears to continue and may evolve to include uplift of southern West Siberian plate with uplift.  相似文献   

6.
The tectonic and geodynamic consequences of the collision between Hindustan and Eurasia are considered in the paper. The tectonic evolution and deformation of Tibet and the Tien Shan in the Late Cenozoic is described on the basis of geological, geophysical, and geodetic data. The factual data and their interpretation, which shed light on the kinematics of the tectonic processes in the lithosphere and the geodynamics of the interaction between the Tien Shan, Tarim, and Tibet are discussed. A geodynamic model of their interaction is proposed.  相似文献   

7.
This study provides new low-temperature thermochronometric data, mainly apatite fission track data on the basement rocks in and adjacent to the Talas-Fergana Fault, in the Kyrgyz Tien Shan in the first place.In the second place, we also present new detrital apatite fission track data on the Meso-Cenozoic sediments from fault related basins and surrounding intramontane basins. Our results confirm multistaged Meso-Cenozoic tectonic activity, possibly induced by the accretion of the so-called Cimmerian blocks to the Eurasian margin. New evidence for this multi-staged thermo-tectonic activity is found in the data of both basement and Meso-Cenozoic sediment samples in or close to the Talas-Fergana Fault.Zircon(U-Th)/He and apatite fission track data constrain rapid Late TriassiceE arly Jurassic and Late JurassiceE arly Cretaceous basement cooling in the Kyrgyz Tien Shan around 200 Ma and 130 -100 Ma respectively. Detrital apatite fission track results indicate a different burial history on both sides of the Talas-Fergana Fault. The apatite fission track system of the Jurassic sediments in the Middle Tien Shan unit east of the Talas-Fergana Fault is not reset, while the Jurassic sediments in the Fergana Basin and Yarkand-Fergana Basin, west of the fault zone, are partially and in some cases even totally reset. The totally reset samples exhibit Oligocene and Miocene ages and evidence the Cenozoic reactivation of the western Kyrgyz Tien Shan as a consequence of the India-Eurasia convergence.  相似文献   

8.
This paper reviews and integrates new results on: (1) the Late Paleozoic and Mesozoic evolution of Central Asia; (2) Cenozoic mountain building and intramontane basin formation in the Altay-Sayan area; (3) comparison of the tectonic evolutionary paths of the Altay, Baikal, and Tien Shan regions; (4) Cenozoic tectonics and mantle-plume magmatic activity; and (5) the geodynamics and tectonic evolution of Central Asia as a function of the India-Himalaya collision. It provides a new and more complete scenario for the formation of the Central Asian intracontinental mountain belt, compared with the generally accepted model of the “indentation” of the Indian plate into the Eurasian plate. The new model is based on the hypothesis of a complex interaction of lithospheric plates and mantle-plume magmatism. Compilation and comparison of new and published structural, geomorphological, paleomagnetic, isotopic, fission-track, and plume magmatism data from the Baikal area, the Altay, Mongolia, Tien Shan, Pamir, and Tibet show that the main stages of their orogenic evolution and basin sedimentation are closely related in time and space. After a long period of tectonic quiescence and peneplanation, Central and Southeast Asia were strongly affected by India-Eurasia collisional tectonics. During the first collisional stage (60 to 35 Ma), a first series of high mountains formed in the Himalayas, southern Tibet, and, possibly, the southern Tien Shan. Eocene deposits, younging northward, formed coevally with the orogeny in the near-Himalaya trough, Tarim, Tajik depression, and Fergana Basin. During postcollisional convergence, new depressions formed over wide territories, from the Tarim to Baikal and Altay areas. However, intensification of the deformation and uplift later were propagated northward, with development of the Qinghai-Tibetan Plateau (20 to 12 Ma), Tien Shan mountains (18 to 11 Ma), Junggar mountains and depression (8 to 5 Ma), and Altay, Baikal, and Transbaikal depressions and mountains (3 Ma).

Northward propagation of the deformation front from the Himalayan collision zone is suggested by regular northward younging of mountains and intramontane basins. Evidence of this includes: (1) India thrusting under Tibet, resulting in the rotation of the latter (60 to 35 Ma); (2) subsidence of the Tarim ramp depression, the rise of the Tien Shan, and the migration of both the Tien Shan and Tarim to the northwest along the Junggar and Talas-Fergana strike-slip faults (35 to 8 Ma); (3) subsidence of the Junggar plate, counterclockwise rotation of the Mongolian and Amur plates (8 to 3 Ma); and (4) rise of the Altay, Hangai, and Transbaikal areas, clockwise rotation of the Amur plate, and rapid opening of the Baikal rift. There is a clear relation between tectonics (rotation of the Tibet and Amur microplates, displacement along plate boundaries) and plume magmatism. The effects of the latter on moving plates are deduced from migration of the Tien Shan volcanic area toward the Tibet area and of the South Mongolian volcanic migration toward the Hangai area. Magmatism and tectonic processes became synchronous just after India collided with the South Himalaya area (60 Ma) and the Pamirs (35 Ma). Plumes beneath the Asian plate are considered to be responsible for the rotation of the microplates and for the northward propagation of tectonic activity from the zone of collision. Mantle magmatism is lacking beneath the Altay. In this case, mountain-building processes and basin-formation mechanisms likely are related to external sources of deformation originating from the India-Pamir convergence. In addition, they also may be related to the general translation and rotation of microplates.  相似文献   

9.
The extended Saryarka and Shyngyz-North Tien Shan volcanic belts that underwent secondary deformation are traced in the Caledonides of Kazakhstan and the North Tien Shan. These belts are composed of igneous rocks pertaining to Early Paleozoic island-arc systems of various types and the conjugated basins with oceanic crust. The Saryarka volcanic belt has a complex fold-nappe structure formed in the middle Arenigian-middle Llanvirnian as a result of the tectonic juxtaposition of Early-Middle Cambrian and Late Cambrian-Early Ordovician complexes of ensimatic island arcs and basins with oceanic crust. The Shyngyz-North Tien Shan volcanic belt is characterized by a rather simple fold structure and consists of Middle-Late Ordovician volcanic and plutonic associations of ensialic island arcs developing on heterogeneous basement, which is composed of complexes belonging to the Saryarka belt and Precambrian sialic massifs. The structure and isotopic composition of the Paleozoic igneous complexes provide evidence for the heterogeneous structure of the continental crust in various segments of the Kazakh Caledonides. The upper crust of the Shyngyz segment consists of Early Paleozoic island-arc complexes and basins with oceanic crust related to the Saryarka and Shyngyz-North Tien Shan volcanic belts in combination with Middle and Late Paleozoic continental igneous rocks. The deep crustal units of this segment are dominated by mafic rocks of Early Paleozoic suprasubduction complexes. The upper continental crust of the Stepnyak segment is composed of Middle-Late Ordovician island-arc complexes of the Shyngyz-North Tien Shan volcanic belt and Early Ordovician rift-related volcanics. The middle crustal units are composed of Riphean, Paleoproterozoic, and probably Archean sialic rocks, whereas the lower crustal units are composed of Neoproterozoic mafic rocks.  相似文献   

10.
塔里木板块周缘晚古生代以来的构造演化   总被引：13，自引：0，他引：13       下载免费PDF全文
刘训 Graham  S 《地球科学》1994,19(6):715-725
塔里木板块在晚古生代以来,经历了一系列碰撞和拼合事件,受北侧哈萨克斯坦－准噶尔板块碰撞的影响,南天山石炭纪再生洋盆于早二叠世末隆起,并导致天山山前陆盆地形成。这一时期塔木西部强烈的热活动事件,反映了一次地壳开裂活动,并导致天山山前的前陆盆地形成,这一时期里木西部强烈的热活动事件,反映了一次地壳开裂活动,同时进一步推动了塔里木向天山下插的陆内俯冲活动及前陆盆地的形成,中生代时期,特提斯洋盆的活动及先  相似文献   

11.
In situ U‐Th/Pb (LA‐ICP‐MS) monazite ages from the Hindu Kush of NW Pakistan provide new petrochronologic constraints on the tectonic evolution of the Himalaya–Karakoram–Tibet orogen. Monazites from two adjacent garnet + staurolite schist specimens yield multiple age populations that record the major Mesozoic and Cenozoic deformational, magmatic and metamorphic events along the southern margin of Eurasia. These include the accretion of the Hindu Kush–SW Pamir to Eurasia during the Late Triassic, followed by the accretion of the Karakoram terrane in the Early Jurassic. Younger Jurassic and Cretaceous ages record the development of an Andean‐style volcanic arc along the southern Eurasian margin, which ended with the docking of the Kohistan island arc and the emplacement of the Kohistan–Ladakh batholith during the Late Cretaceous. The initial Eocene collision of India with Eurasia was followed by widespread high‐temperature metamorphism and anatexis associated with crustal thickening within the Himalaya system in the Late Oligocene and Early Miocene.  相似文献   

12.
Cenozoic deformation within the Tien Shan of central Asia has accommodated part of the post-collisional indentation of the Indian plate into Asia. Within the Urumgi—Korla region of the Chinese Tien Shan this occurred dominantly on thrusts, with secondary strike-slip faulting. The gross pattern of deformation is of moderate to steeply dipping thrusts that have overthrust foreland basins to the north and south of the range, the Junggar and Tarim basins, respectively. Smaller foreland basins lie within the margins of the range itself (Turfan, Chai Wo Pu, Korla and Qumishi basins); these lie in the footwalls of local thrust systems. Both the Turfan and the Korla basins contain major thrusts within them; they are complex foreland basins. Deformation has progressively affected regions further into the interior of the Junggar Basin, and propagated into the interiors of the intermontane basins. No unidirectional deformation front has passed across the Tien Shan in the Neogene and Quaternary. An Oligocene unconformity may indicate the time of the onset of the Cenozoic deformation, but most of the Cenozoic molasse has been deposited after the Palaeogene. The rate of deposition in basins next to the uplifted ranges has increased since the onset of deformation. There has been at least about 80 km of Cenozoic shortening across this part of the Tien Shan. Cenozoic shortening is greater in sections of the range further west; these are nearer to the northern margin of the Indian indenter. Cenozoic compression has reactivated structures created by the two late Palaeozoic collisions that created the ancestral Tien Shan. These Palaeozoic structures have exerted a strong control over the style and location of the Cenozoic deformation.  相似文献   

13.
The concepts of the role of catastrophic breakthroughs of ice- and rock-dammed and thermokarst lakes in West Siberia in the Late Neopleistocene–Holocene are systematized. The Late Neopleistocene glacial maximum in the mountains and on the plain was obviously at the same time, at 90–60 ka. It has been revealed that the basal part of the Late Quaternary cyclic three-stage upper Ob' River terrace is formed by catafluvial sediments including boulder-gravels, which descend from the valley edge beneath the water line. The Early Karginian (Kharsoimian) marine layers are spatially related to the valleys of the rushed waters of ice-dammed Lake Ermakovskoe. Substantiation is given to the concept of catastrophic flows that arrived at the plain from the Pamir and Tien Shan mountains in the Holocene Optimum and carried the Aral microfauna through the Turgai trough into the Lake Chany area. Floods resulted from the breakthrough of thermokarst lakes in the north of the West Siberian plain were typical in Karginian and Holocene time. The breakthroughs of moraine-dammed basins in the Altai Mountains took place mainly in Karginian time, whereas the breakthroughs of rock-dammed lakes, in the Sartan and Holocene epochs.  相似文献   

14.
亚洲东部存在一个巨大的三角形地震构造区域,大体上,喜马拉雅山脉、帕米尔—天山—阿尔泰山—贝加尔和东经105°线是它的3个边界,主要覆盖中国和蒙古国西部众多高原、山脉及山间盆地。三角区内现今构造活动和地震广泛强烈,地壳破碎,显示不均匀的块体边界和块内变形;区外基本上是稳定的刚性陆块,地震很少,变形较弱,处于整体缓慢运动之中。这个宽阔的板内变形区起源于印度、菲律宾海—西太平洋和欧亚三大板块之间的动力作用以及深部地幔流的影响。向北快速运动的印度次大陆已近水平地插入到西藏板块下,沿喜马拉雅弧产生多种运动和变形,并向亚洲内部远距离地扩散。沿东经95°～100°,向北的地壳运动向东和东南方向偏转,阻截了喜马拉雅弧东端的北向运动;而在喜马拉雅弧西端,帕米尔继续向北挤进中亚,受天山—阿尔泰山—贝加尔一线西北側稳定地壳的限制,扩散的变形被中国、蒙古、俄罗斯边境地区一系列EW向和NW向的老断层吸收并在它们的西端终止。菲律宾海—西太平洋向欧亚大陆的消减-俯冲导致沿海沟-岛弧的漫长而狭窄的地震带,但对亚洲大陆的水平挤压较小,未能阻挡亚洲大陆东部向东移动。其部分原因可能是俯冲板片受到来自欧亚大陆下的ES向地幔流的推挤,这个ES向地幔流与来自印度下面的N向地幔流在西藏中部汇合并向东偏转,在大尺度上与GPS观测到的地表移动图像一致。  相似文献   

15.
On the basis of stratigraphical and geological data, paleogeographical and palinspastic reconstructions of the Kazakhstan Paleozoides were done; their multistage geodynamic evolution was considered; their tectonic zoning was proposed. The main stages are described: the initiation of the Cambrian and Ordovician island arcs; the development of the Kazakhstan accretionary–collisional composite continent in the Late Ordovician as a result of continental subduction and the amalgamation of Gondwana blocks with the island arcs (a long granitoid collisional belt also formed in this period); the development of the Devonian and Carboniferous–Permian active margins of the composite continent and its tectonic destruction in the Late Paleozoic.In the Late Ordovician, compensated terrigenous and volcanosedimentary complexes formed within Kazakhstania and developed in the Silurian. The Sakmarian, Tagil, Eastern Urals, and Stepnyak volcanic arcs formed at the boundaries with the Ural, Turkestan, and Junggar–Balkhash Oceans. In the late Silurian, Kazakhstania collided with the island arcs of the Turkestan and Ob'–Zaisan Oceans, with the formation of molasse and granite belts in the northern Tien Shan and Chingiz. This was followed by the development of the Devonian and Carboniferous–Permian active margins of the composite continent and the inland formation of the Early Devonian rift-related volcanosedimentary rocks, Middle–Late Devonian volcanic molasse, Late Devonian–Early Carboniferous rift-related volcanosedimentary rocks, terrigenous–carbonate shelf sediments, and carbonaceous lake–bog sediments, and the Middle–Late Carboniferous clastic rocks of closed basins. In the Permian, plume magmatism took place on the southern margin of the Kazakhstan composite continent. It was simultaneous with the formation of red-colored molasse and the tectonic destruction of the Kazakhstan Paleozoides as a result of a collision between the East European and Kazakhstan–Baikal continents.  相似文献   

16.
The main differences and similarities between the tectonic features of the Urals and the Tien Shan are considered. In the Neoproterozoic and Early and Middle Paleozoic, the Ural and Turkestan oceanic basins were parts of one oceanic domain, with several distinct regions in which tectonic events took different courses. The Baltic continental margin of the Ural paleoocean was active, whereas the Tarim-Alay margin of the Turkestan ocean, similar in position, was passive. The opposite continental margin in the Urals is known beginning from the Devonian as the Kazakh-Kyrgyz paleocontinent. In the Tien Shan, a similar margin developed until the Late Ordovician as the Syr Darya block with the ancient continental crust. In the Silurian, this block became a part of the Kazakh-Kyrgyz paleocontinent. The internal structures of the Ural and Turkestan paleooceans were different. The East Ural microcontinent occurred in the Ural paleoocean during the Early and Middle Paleozoic. No microcontinents are established in the Turkestan oceanic basin. Volcanic arcs in the Ural paleoocean were formed in the Vendian (Ediacarian), at the Ordovician-Silurian boundary, and in the Devonian largely along the Baltic margin at different distances from its edge. In the Turkestan paleoocean, a volcanic arc probably existed in the Ordovician at its Syr Darya margin, i.e., on the other side of the ocean in comparison with the Urals. The subduction of the Turkestan oceanic crust developed with interruptions always in the same direction. The evolution of subduction in the Urals was more complicated. The island arc-continent collision occurred here in the Late Devonian-Early Carboniferous; the continent-continent collision took place in the Moscovian simultaneously with the same process in the Tien Shan. The deepwater flysch basins induced by collision appeared at the Baltic margin in the Famennian and Visean, whereas in the Bashkirian and Moscovian they appeared at the Alay-Tarim margin. In the Devonian and Early Carboniferous, the Ural and Turkestan paleooceans had a common active margin along the Kazakh-Kyrgyz paleocontinent. The sudduction of the oceanic crust beneath this paleocontinent in both the Urals and the Tien Shan started, recommenced after interruptions, and finally ceased synchronously. In the South Ural segment, the Early Carboniferous subduction developed beneath both Baltica and the Kazakh-Kyrgyz paleocontinent, whereas in the Tien Shan, it occurred only beneath the latter paleocontinent. A divergent nappe-fold orogen was formed in the Urals as a result of collision of the Kazakh-Kyrgyz paleocontinent with the Baltic and Alay-Tarim paleocontinents, whereas a unilateral nappe-fold orogen arose in the Tien Shan. The growth of the high divergent orogen brought about the appearance of the Ural Foredeep filled with molasse beginning from the Kungurian. In the Tien Shan, a similar foredeep was not developed; a granitic axis similar to the main granitic axis in the Urals was not formed in the Tien Shan either.  相似文献   

17.
The crustal orogeny which formed the present-day Tien Shan results from the complex interaction between two independent processes. The first is the lateral (horizontal) compression related to the collision between the Indian and Eurasian Plates. The second is the rearrangement and flow of crustal material at different levels of the lithosphere beneath the mountain belt. Two broad morphologic and genetic types of mountain basins (intramontane and intermontane/foreland) are proposed as indicators of specific geodynamic factors controlling the topographic relief of the orogenic belt. The first-type basins, having the upper crustal roots, reflect mainly the N–S crustal compression and correspond to simple (elementary) longitudinal folds with basement involvement. The second type basins developed mostly in response to deep processes in the upper mantle and lower crust.  相似文献   

18.
The intraplate Ancestral Rocky Mountains of western North America extend from British Columbia, Canada, to Chihuahua, Mexico, and formed during Early Carboniferous through Early Permian time in response to continent–continent collision of Laurentia with Gondwana—the conjoined masses of Africa and South America, including Yucatán and Florida. Uplifts and flanking basins also formed within the Laurentian Midcontinent. On the Gondwanan continent, well inboard from the marginal fold belts, a counterpart structural array developed during the same period. Intraplate deformation began when full collisional plate coupling had been achieved along the continental margin; the intervening ocean had been closed and subduction had ceased—that is, the distinction between upper versus lower plates became moot. Ancestral Rockies deformation was not accompanied by volcanism. Basement shear zones that formed during Mesoproterozoic rifting of Laurentia were reactivated and exerted significant control on the locations, orientations, and modes of displacement on late Paleozoic faults.Ancestral Rocky Mountain uplifts extend as far south as Chihuahua and west Texas (28° to 33°N, 102° to 109°W) and include the Florida-Moyotes, Placer de Guadalupe–Carrizalillo, Ojinaga–Tascotal and Hueco Mountain blocks, as well as the Diablo and Central Basin Platforms. All are cored with Laurentian Proterozoic crystalline basement rocks and host correlative Paleozoic stratigraphic successions. Pre-late Paleozoic deformational, thermal, and metamorphic histories are similar as well. Southern Ancestral Rocky Mountain structures terminate along a line that trends approximately N 40°E (present coordinates), a common orientation for Mesoproterozoic extensional structures throughout southern to central North America.Continuing Tien Shan intraplate deformation (Central Asia) has created an analogous array of uplifts and basins in response to the collision of India with Eurasia, beginning in late Miocene time when full coupling of the colliding plates had occurred. As in the Laurentia–Gondwana case, structures of similar magnitude and spacing to those in Eurasia have developed in the Indian plate. Within the present orogen two ancient suture zones have been reactivated—the early Paleozoic Terskey zone and the late Paleozoic Turkestan suture between the Siberian and East Gondwanan cratons. Inverted Proterozoic to early Paleozoic rift structures and passive-margin deposits are exposed north of the Terskey zone. In the Alay and Tarim complexes, Vendian to mid-Carboniferous passive-margin strata and the subjacent Proterozoic crystalline basement have been uplifted. Data on Tien Shan uplifts, basins, structural arrays, and deformation rates guide paleotectonic interpretations of ancient intraplate mountain belts. Similarly, exhumed deep crustal shear zones in the Ancestral Rockies offer insight into partitioning and reorientation of strain during contemporary intraplate deformation.  相似文献   

19.
王荃 《地球学报》1984,6(3):35-47
<正> 科学领域中的任何一门学科在其发展的历史中,往往存在着以具有重大突破为标志的迅速发展阶段。板块构造学说就是现代地球科学取得最新进展的代表。所以,有人将其称为地球科学的一场革命。板块构造理论创建于六十年代后期,但与其有关的一些思想、概念则源远流长。  相似文献   

20.
Surface exposure dating has become a helpful tool for establishing numeric glacial chronologies, particularly in arid high-mountain regions where radiocarbon dating is challenging due to limited availability of organic material. This study presents 13 new 10Be surface exposure ages from the Kitschi-Kurumdu Valley in the At Bashi Range, Tien Shan. Three moraines were dated to ~ 15, 21 and > 56 ka, respectively, and corroborate previous findings that glacial extents in the Tien Shan during Marine Oxygen Isotope Stage (MIS) 2 were limited compared to MIS 4. This likely documents increasingly arid conditions in Central Asia during the last glacial cycle. Morphological evidence in the Kitschi-Kurumdu Valley and a detailed review of existing numeric glacial chronologies from the Tien Shan indicate that remnants of the penultimate glaciation (MIS 6) are preserved, whereas evidence for MIS 5 glacier advances remains equivocal. Reviewed and recalculated exposure ages from the Pamir mountains, on the other hand, reveal extensive MIS 5 glacial extents that may indicate increased monsoonal precipitation. The preservation of MIS 3 moraines in the Tien Shan and the southern Pamir does not require any monsoonal influence and can be explained alternatively with increased precipitation via the westerlies.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号