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1.
《International Geology Review》2012,54(5):437-447
Subduction-zone magmatism became extensive along the west coast of South America during the Ordovician, soon after Gondwana was assembled. During the remainder of the Paleozoic and the early Mesozoic, eastward subduction of the Farallon plate led to emplacement of a succession of granitic and volcanic rocks. During the Cretaceous, when South America broke away from Africa and began moving independently toward the Pacific Basin, the resulting opposite motions of the South American and Farallon plates toward the subduction zone caused vigorous tectonic mountain building. But by the Oligocene, South America had advanced more than 2000 km beyond the position of the Cretaceous subduction zone's root in the lower mantle. The South American plate, moving westward over the subducting plate, pushed down and flattened the curved top of the subducting slab, as indicated by today's flattened earthquake zone under South America. I hypothesize that this flattening increased the subducting slab's resistance with the underlying lower mantle. Crustal deformation slowed, and the mountains built during the Cretaceous and later were eroded to a peneplane. During the Oligocene, about 25 Ma, the Farallon plate broke into the Cocos and Nazca plates, and I suggest that along the west coast of South America a shear at a slope of about 30° cut through the subducting slab. The oceanic (Nazca) part of the slab then entered the lower mantle below the Andes with a steeper dip than before. As the newly sheared obtuse upper corner of the Nazca plate pushed eastward and downward, it buckled the rigid edge of the continent and began the folding and thrusting of the Andean (Quechua) orogeny. The orogeny continues, but earthquake foci indicate that as South America continues to move westward, the subduction zone once again is flattening; in the future we can expect the Nazca slab to shear once more and its new wedge-shaped end to enter the lower mantle again. 相似文献
2.
Oceanic crust west of North America at the beginning of the Jurassic belonged to the Kula plate. The development of the western margin of North America since the Jurassic reflects interaction with the Kula plate, the Kula-Farallon spreading center and the Farallon plate. The Kula plate ceased to exist in the Paleocene and later developments were caused by interaction of the Farallon plate and, subsequently, collision with the East Pacific Rise.At the beginning of the Jurassic, when spreading between North and South America began, the Kula-Farallon-Pacific triple junction moved to the north relative to North America, and the eastern end of the Kula-Farallon spreading center swept northwards along the continental margin.During the Paleocene, Kula-Pacific spreading ceased and the Kula plate fused to the Pacific plate. Throughout the Mesozoic, subduction of the Kula plate took place along the Alaskan continental margin. When the Kula plate joined the Pacific plate a new subduction zone formed along the line of the present Aleutian chain.Wrangellia and Stikinia, anomalous terrains in Alaska and northwestern Canada respectively, were emplaced by transport on the Kula plate from lower latitudes. Hypotheses which require transport of these plates in the Mesozoic from the “far reaches of the Pacific” ignore the problem of transport across either the Kula-Pacific or Kula-Farallon spreading centers. The interaction of the Kula plate and western North America throughout the Jurassic and the Cretaceous should result in emplacement of these terrains by motion oblique to the continental margin. Tethyan faunas in Stikinia must come from the western end of Tethys between North and South America, not the Indonesian region at the eastern end of Tethys.As the northeastern end of the Kula-Farallon ridge moved northward, the sense of motion changed from right lateral shear between the Kula and North American plates to collision or left lateral shear between the Farallon and North American plates. Left lateral shear along zones analogous to the Mojave-Sonora megashear may have been the means by which anomalous terrains were transported to the southeast into the gap between North and South America forming present day Central America. Such a model overcomes the overlap difficulties suffered in previous attempts to reconstruct the Mesozoic paleogeography of Central America. 相似文献
3.
The spatial distribution of recent (under 2 Ma) volcanism has been studied in relation to mantle hotspots and the evolution of the present-day supercontinent which we named Northern Pangea. Recent volcanism is observed in Eurasia, North and South America, Africa, Greenland, the Arctic, and the Atlantic, Indian, and Pacific Oceans. Several types of volcanism are distinguished: mid-ocean ridge (MOR) volcanism; subduction volcanism of island arcs and active continental margins (IA + ACM); continental collision (CC) volcanism; intraplate (IP) volcanism related to mantle hotspots, continental rifts, and transcontinental belts. Continental volcanism is obviously related to the evolution of Northern Pangea, which comprises Eurasia, North and South America, India, Australia, and Africa. The supercontinent is large, with predominant continental crust. The geodynamic setting and recent volcanism of Northern Pangea are determined by two opposite processes. On one hand, subduction from the Pacific Ocean, India, the Arabian Peninsula, and Africa consolidates the supercontinent. On the other hand, the spreading of oceanic plates from the Atlantic splits Northern Pangea, changes its shape as compared with Wegener’s Pangea, and causes the Atlantic geodynamics to spread to the Arctic. The long-lasting steady subduction beneath Eurasia and North America favored intense IA + ACM volcanism. Also, it caused cold lithosphere to accumulate in the deep mantle in northern Northern Pangea and replace the hot deep mantle, which was pressed to the supercontinental margins. Later on, this mantle rose as plumes (IP mafic magma sources), which were the ascending currents of global mantle convection and minor convection systems at convergent plate boundaries. Wegener’s Pangea broke up because of the African superplume, which occupied consecutively the Central Atlantic, the South Atlantic, and the Indian Ocean and expanded toward the Arctic. Intraplate plume magmatism in Eurasia and North America was accompanied by surface collisional or subduction magmatism. In the Atlantic, Arctic, Indian, and Pacific Oceans, deep-level plume magmatism (high-alkali mafic rocks) was accompanied by surface spreading magmatism (tholeiitic basalts). 相似文献
4.
Throughout the Early Tertiary the area of the Farallon oceanic plate was episodically diminished by detachment of large and small northern regions, which became independently moving plates and microplates. The nature and history of Farallon plate fragmentation has been inferred mainly from structural patterns on the western, Pacific-plate flank of the East Pacific Rise, because the fragmented eastern flank has been subducted. The final episode of plate fragmentation occurred at the beginning of the Miocene, when the Cocos plate was split off, leaving the much reduced Farallon plate to be renamed the Nazca plate, and initiating Cocos–Nazca spreading. Some Oligocene Farallon plate with rifted margins that are a direct record of this plate-splitting event has survived in the eastern tropical Pacific, most extensively off northern Peru and Ecuador. Small remnants of the conjugate northern rifted margin are exposed off Costa Rica, and perhaps south of Panama. Marine geophysical profiles (bathymetric, magnetic and seismic reflection) and multibeam sonar swaths across these rifted oceanic margins, combined with surveys of 30–20 Ma crust on the western rise-flank, indicate that (i) Localized lithospheric rupture to create a new plate boundary was preceded by plate stretching and fracturing in a belt several hundred km wide. Fissural volcanism along some of these fractures built volcanic ridges (e.g., Alvarado and Sarmiento Ridges) that are 1–2 km high and parallel to “absolute” Farallon plate motion; they closely resemble fissural ridges described from the young western flank of the present Pacific–Nazca rise. (ii) For 1–2 m.y. prior to final rupture of the Farallon plate, perhaps coinciding with the period of lithospheric stretching, the entire plate changed direction to a more easterly (“Nazca-like”) course; after the split the northern (Cocos) part reverted to a northeasterly absolute motion. (iii) The plate-splitting fracture that became the site of initial Cocos–Nazca spreading was a linear feature that, at least through the 680 km of ruptured Oligocene lithosphere known to have avoided subduction, did not follow any pre-existing feature on the Farallon plate, e.g., a “fracture zone” trail of a transform fault. (iv) The margins of surviving parts of the plate-splitting fracture have narrow shoulders raised by uplift of unloaded footwalls, and partially buried by fissural volcanism. (v) Cocos–Nazca spreading began at 23 Ma; reports of older Cocos–Nazca crust in the eastern Panama Basin were based on misidentified magnetic anomalies.There is increased evidence that the driving force for the 23 Ma fission of the Farallon plate was the divergence of slab-pull stresses at the Middle America and South America subduction zones. The timing and location of the split may have been influenced by (i) the increasingly divergent northeast slab pull at the Middle America subduction zone, which lengthened and reoriented because of motion between the North America and Caribbean plates; (ii) the slightly earlier detachment of a northern part of the plate that had been entering the California subduction zone, contributing a less divergent plate-driving stress; and (iii) weakening of older parts of the plate by the Galapagos hotspot, which had come to underlie the equatorial region, midway between the risecrest and the two subduction zones, by the Late Oligocene. 相似文献
5.
6.
《Journal of Structural Geology》2001,23(2-3):431-453
The Tertiary Falcón Basin in northwestern Venezuela has a privileged position in the geodynamic puzzle of northwestern South America, occurring in a region where several major plates (Caribbean, South America and Nazca) and minor lithospheric blocks (Maracaibo, Bonaire and Western Colombia) are interacting. A combination of good exposures due to aridity and a near-continuous sedimentary record in a now inverted basin helps to unravel the Neogene and Quaternary geodynamic evolution of this region. A neotectonic and microtectonic investigation of the Plio-Quaternary sedimentary rocks of the northern Falcón Basin reveals that this region is subject to a compressive to transpressive regime at present. This regime is characterized by a NNW–SSE oriented maximum horizontal stress, and a ENE–WSW trending intermediate (or minimum) horizontal stress, as is confirmed by focal mechanism solutions. This stress field is in agreement both with the NNE-directed extrusion of the Maracaibo and Bonaire blocks in Western Venezuela, where the Falcón Basin is located, and present-day transpression along the Caribbean-South America plate boundary zone. 相似文献
7.
南海西缘新生代沉积盆地形成动力学探讨 总被引：8，自引：3，他引：5
通过对南海西缘新生代沉积盆地伸展作用、沉降、构造变形等特征分析,检查印支地块多条近北西向走滑断裂时间、幅度等特征以及与盆地之间联系,结果表明印度-欧亚碰撞引起的逃逸作用与南海西缘新生代盆地没有直接的成因联系;两个与俯冲有关的不同扩张机制与南海西缘新生代盆地有成因联系,即(1)太平洋板块在古新世到始新世的滚动后退,太平洋-欧亚板块汇聚速率的降低驱使这些盆地产生初始伸展作用;(2)渐新世到中中新世古南海南倾俯冲板块的拖曳力,进一步驱使这些盆地的伸展及接着的南海扩张. 相似文献
8.
A multiyear solution of the SIRGAS-CON network was used to estimate the strain rates of the earth surface from the changing directions of the velocity vectors of 140 geodetic points located in the South American plate. The strain rate was determined by the finite element method using Delaunay triangulation points that formed sub-networks; each sub-network was considered a solid and homogeneous body. The results showed that strain rates vary along the South American plate and are more significant on the western portion of the plate, as expected, since this region is close to the subduction zone of the Nazca plate beneath the South American plate. After using Euler vectors to infer Nazca plate movement and to orient the velocity vectors of the South American plate, it was possible to estimate the convergence and accommodation rates of the Nazca and South American plates, respectively. Strain rate estimates permitted determination of predominant contraction and/or extension regions and to establish that contraction regions coincide with locations with most of the high magnitude seismic events. Some areas with extension and contraction strains were found to the east within the stable South American plate, which may result from different stresses associated with different geological characteristics. These results suggest that major movements detected on the surface near the Nazca plate occur in regions with more heterogeneous geological structures and multiple rupture events. Most seismic events in the South American plate are concentrated in areas with predominant contraction strain rates oriented northeast-southwest; significant amounts of elastic strain can be accumulated on geological structures away from the plate boundary faults; and, behavior of contractions and extensions is similar to what has been found in seismological studies. 相似文献
9.
The presented scenario of free convection flows in a subduction zone is based on experimental and theoretical simulation. The experimental simulation of free convection flows is carried out under various conditions of heat transfer that occurs between the oceanic and continental limbs of the subduction zone. The experiments show that to provide insights into subduction zones, it is necessary to estimate the horizontal forces acting on the left and right sides of the plunging plate, as well as the resulting horizontal force and its direction. The vector sum of horizontal and gravity forces of the subducting plate determines the slope angle of this plate at different depths. Heat transfer in the subducting plate has been considered. The y min coordinate of the temperature minimum in a plate and the value of minimum temperature have been estimated. The forces that arise due to phase transition and owing to the horizontal temperature gradient along the thickness of the descending lithosphere in the transitional mantle layer C are estimated as well. These forces are directed in opposite direction from the y min coordinate and induce spreading of the subducting lithosphere along the boundary between the upper and lower mantle. Theoretical simulation of the hydrodynamics and heat transfer in combination with experimental simulation of convection flows in a subduction zone indicates that a significant part of the upper mantle material of the plunging plate circulates in the oceanic limb of the subduction zone owing to spreading from the region of minimum temperature along a 670 km boundary. 相似文献
10.
Based on electromagnetic measurements we determined the current stress directions in the uppermost continental crust of Patagonia
between the active plate margin of the Chilean Pacific coast and the Argentinean passive Atlantic margin. Regional variations
of the observed stress pattern are giving details onto the acting tectonic processes. We distinguish five regional stress
domains with different prevailing horizontal stress directions (SH): 1. Southern Coastal Cordillera and Longitudinal Valley (SH = SSW–NNE), 2. Chiloé Island (SH = SW–NE), 3. Northern Patagonian Andes (SH = WSW–ENE), 4. Argentinean Pampa and Atlantic margin (SH = WNW–ESE) and 5. Southern Patagonian Andes (SH = WNW–ESE). These stress regimes can be related to the geometry of the subducting Nazca- and Antarctic plates, to the transform
fault between the South America and Scotia plates and to passive margin processes along the Atlantic coast. Absolute plate
motion and rapid relative plate convergence control the subduction geometry and therefore the stress directions along the
convergent margin of the South America Plate and the structural style within and landward of the Magmatic Arc. The knowledge
of current local stress directions permits the characterisation of potential fault kinematics. By in situ measuring of electromagnetic
emissions from rocks we determined the maximum horizontal stress orientation in the uppermost crust using a new geophysical
tool. Our investigations on the orientation of the stress regimes also allow conclusions about the causative forces of either
tectonic or gravitational origin in this part of the South-America Plate. 相似文献
11.
在新生代澳大利亚板块和欧亚板块之间的大洋中，存在一些地块(微板块)；同时，澳大利亚板块北部边缘的一些地块先后和澳大利亚板块分离，向北运动，与一些和欧亚板块分离出来的地块先后发生碰撞缝合。在此期间，由于地块分离而发生海底扩张，产生许多小洋盆，如南海、苏录海、苏拉威西海、安达曼海等，最后形成了东南亚地区今日的构造景观。笔者从大南海地区新生代的构造演化史之框架来研究南海地区新生代的构造演化历史，认为南海地区新生代的构造活动既与印度板块和欧亚板块的碰撞有关，也与太平洋板块向欧亚板块的俯冲活动有联系；同时，还受到澳大利亚板块向北运动之影响。南海地区在新生代发生过两次海底扩张，第一次海底扩张发生在42～35Ma前．是受印度板块和欧亚板块碰撞而引起欧亚大陆之下向东南方向之地幔流的影响而发生的，其海底扩张方向为NWSE，产生了南海西南海盆；第二次海底扩张发生于32～17Ma前。由于太平洋板块向欧亚板块俯冲，俯冲的大洋岩石圈已达700km深处，阻挡了欧亚大陆的上地幔向东南方向之流动，从而转向南流动。引起南海地区南北向海底扩张，即新生代第二次海底扩张，产生了南海中央海盆。南海新生代洋盆诞生之后，由于大南海地区继续有地块碰撞和边缘海海底扩张，对南海南部地区产生挤压，从而使这里的沉积发生变形，这就引起万安运动(南海南部)。 相似文献
12.
《Gondwana Research》2014,25(3-4):984-998
In recent years several tectonic reconstructions have been presented for Australia–Antarctica break-up, with each putting the Australian plate in a different location with respect to Antarctica. These differences reflect the different datasets and techniques employed to create a particular reconstruction. Here we show that some of the more recent reconstructions proposed for Australia–Antarctica break-up are inconsistent with both our current knowledge of margin evolution as well as the inferred match in basement terranes on the two opposing conjugate margins. We also show how these incorrect reconstructions influence the fit of the Indian plate against Antarctica if its movement is tied to the Australian plate. Such errors can have a major influence on the tectonic models of other parts of the world. In this case, we show how the position of the Australia plate can predetermine the extent of Greater India, which is (rightly or wrongly) used by many as a constraint in determining the timing of India–Asia, or India–Island Arc collisions during the closure of Tethys. We also discuss the timing of Australia–Antarctica break-up, and which linear magnetic features are a product of symmetric sea-floor spreading versus those linear magnetic features that result from rifting of a margin. The 46 Ma to 84 Ma rotational poles previously proposed for Australia–Antarctica break-up, and confined to transitional crust and the continent–ocean transition zone, more likely formed during earlier stages of rifting rather than during symmetric sea-floor spreading of oceanic crust. So rotation poles that have been derived from magnetic anomalies in such regions cannot be used as input in a plate reconstruction. A new reconstruction of the Australia–Antarctica margin is therefore proposed that remains faithful to the best available geological and geophysical data. 相似文献
13.
《地学前缘(英文版)》2020,11(4):1219-1229
We investigate the effect of the westerly rotation of the lithosphere on the active margins that surround the Americas and find good correlations between the inferred easterly-directed mantle counterflow and the main structural grain and kinematics of the Andes and Sandwich arc slabs.In the Andes,the subduction zone is shallow and with low dip,because the mantle flow sustains the slab;the subduction hinge converges relative to the upper plate and generates an uplifting doubly verging orogen.The Sandwich Arc is generated by a westerly-directed SAM(South American) plate subduction where the eastward mantle flow is steepening and retreating the subduction zone.In this context,the slab hinge is retreating relative to the upper plate,generating the backarc basin and a low bathymetry single-verging accretionary prism.In Central America,the Caribbean plate presents a more complex scenario:(a) To the East,the Antilles Arc is generated by westerly directed subduction of the SAM plate,where the eastward mantle flow is steepening and retreating the subduction zone.(b) To the West,the Middle America Trench and Arc are generated by the easterly-directed subduction of the Cocos plate,where the shallow subduction caused by eastward mantle flow in its northern segment gradually steepens to the southern segment as it is infered by the preexisting westerly-directed subduction of the Caribbean Plateau.In the frame of the westerly lithospheric flow,the subduction of a divergent active ridge plays the role of introducing a change in the oceanic/continental plate's convergence angle,such as in NAM(North American)plate with the collision with the Pacific/Farallon active ridge in the Neogene(Cordilleran orogenic type scenario).The easterly mantle drift sustains strong plate coupling along NAM,showing at Juan de Fuca easterly subducting microplate that the subduction hinge advances relative to the upper plate.This lower/upper plate convergence coupling also applies along strike to the neighbor continental strike slip fault systems where subduction was terminated(San Andreas and Queen Charlotte).The lower/upper plate convergence coupling enables the capture of the continental plate ribbons of Baja California and Yakutat terrane by the Pacific oceanic plate,transporting them along the strike slip fault systems as para-autochthonous terranes.This Cordilleran orogenic type scenario,is also recorded in SAM following the collision with the Aluk/Farallon active ridge in the Paleogene,segmenting SAM margin into the eastwardly subducting Tupac Amaru microplate intercalated between the proto-LiquineOfqui and Atacama strike slip fault systems,where subduction was terminated and para-autochthonous terranes transported.In the Neogene,the convergence of Nazca plate with respect to SAM reinstalls subduction and the present Andean orogenic type scenario. 相似文献
14.
The `plate tectonic mirror image' to the region of the Cocos and Nazca plates, which are currently being subducted beneath Central America, is preserved in the Central Pacific around 120°W just south of the equator. Cruise SO‐180 investigated this remote area during project CENTRAL and acquired new magnetic and bathymetric data. A plate tectonic model for the ‘mirror image’ is presented based on the newly acquired as well as reprocessed existing data. Discordant magnetic anomaly patterns and bathymetric structures indicate at least two major reorganization events (19.5 and 14.7 Myr), which can be detected both in the Cocos‐Nazca spreading system and in the East Pacific Rise. Irregularities in the anomaly pattern and curvilinear structures on the sea floor of the survey area are interpreted in terms of a fossil overlapping spreading centre at the location where the Farallon break‐up originated. 相似文献
15.
An active oceanic spreading ridge is being subducted beneath the South American continent at the Chile Triple Junction. Mass balance estimations to characterize temporal and spatial variations in the frontal accretion, or underplating and subduction of sediments since the Late Miocene, were made using seismic and drill-hole data. At 200 km north of the triple junction, almost 80% of the sediment on the downgoing Nazca plate are subducted. Sediment subduction rate decreases towards the triple junction because of a low in sedimentation rates as the flank of the spreading ridge approaches the trench. At the triple junction, the forearc is almost completely destroyed by spreading ridge collision and subduction erosion. Less than 12% of the available sedimentary input is accreted. South of the triple junction, where the spreading ridge passed 6 Ma ago, a large fraction (>60%) of the sediment on the incoming Antarctic plate has been scraped off and was frontally accreted to the Chile forearc. Spreading ridge subduction leaves a distinctive geological fingerprint, and has a large impact on the mass balance of the subduction zone. However, the high rates of change in the process may make this fingerprint hard to detect in fossil convergent orogens. In the ridge collision zone the sediment supplied to the trench, and the amount of sediment subducted, show strong and distinctive variations on a 1- to 5-million-year time scale. On a 10-million-year time scale, sediment subduction to the Earth's mantle is reduced by spreading ridge collision, caused by the need of the overriding forearc to regain a low angle of taper by frontal accretion. 相似文献
16.
F. L. Sutherland I. T. Graham S. Meffre H. Zwingmann R. E. Pogson 《Australian Journal of Earth Sciences》2013,60(7):983-1005
Prolonged intraplate volcanism along the 4000 km-long East Australian margin for ca 100 Ma raises many genetic questions. Studies of the age-progressive pulses embedded in general basaltic activity have spawned a host of models. Zircon U–Pb dating of inland Queensland central volcanoes gives a stronger database to consider the structure and origin of Australian age-progressive volcanic chains. This assists appraisal of this volcanism in relation to plate motion and plate margin tectonic models. Inland Queensland central volcanoes progressed south-southeast from 34 to 31 Ma (～5.4 cm/yr) until a surge in activity led to irregular southerly progression 31 to 28 Ma. A new inland southeastern Queensland central volcano line (25 to 22 Ma), from Bunya Mountains to North Main Range, followed 3 Ma behind the adjacent coastal progression. The Australian and Tasman Sea age-progressive chains are compared against recent plate motion modelling (Indian Ocean hotspots). The chain lines differ from general vector traces owing to west-facing swells and cessations in activity. Tectonic processes on the eastern plate margin may regulate these irregularities. These include subduction, rapid roll-back and progressive detachment of the Loyalty slab (43 to 15 Ma). West-flowing Pacific-type asthenosphere, related to perturbed mantle convection, may explain the west-facing volcanic surges. Such westward Pacific flow for over 28 Ma is known at the Australian–Antarctic Discordance, southeast of the present Australian plume sites under Bass Strait–West Tasman Sea. Most basaltic activity along eastern Australia marks asthenospheric melt injections into Tasman rift zone mantle and not lithospheric plate speed. The young (post-10 Ma) fields (Queensland, Victoria–South Australia) reflect new plate couplings, which altered mantle convection and stress regimes. These areas receive asthenospheric inputs from deep thermal zones off northeast Queensland and under Bass Strait. 相似文献
17.
18.
西太平洋边缘海盆地的扩张过程和动力学背景 总被引：34，自引：0，他引：34
西太平洋集中发育了全球 75%的边缘海盆地 ,这些盆地形成于始新世、渐新世—中新世和晚中新世—第四纪 3个边缘海扩张幕。文中介绍了边缘海盆地的基本特征和发育模式 ,详细讨论了西北太平洋边缘海盆地周缘板块构造时空格架及其对边缘海盆地形成、演化和关闭过程的控制作用。太平洋板块的俯冲及俯冲带的后退 ,印度—亚洲大陆碰撞的远程效应以及澳洲与印度尼西亚的碰撞是边缘海盆地的 3个重要的区域性控制因素。印度—亚洲大陆的碰撞所形成的向东和东南的地幔流可能推动了东亚大陆东侧和南侧俯冲带的后退 ,并引发弧后扩张作用。同时 ,由这一碰撞引起的东亚大陆边缘NE或NNE向断裂的右旋走滑 ,进一步影响和控制了边缘海盆地的几何学特征及演化。澳大利亚和印度尼西亚的碰撞阻碍了俯冲带的后退 ,导致了南海、Sulu海和Celebes海盆地的扩张终止。同时这一碰撞推动菲律宾海板块向北运移 ,并使Bonin弧与中央日本碰撞 ,导致日本海关闭 相似文献
19.
塔里木陆块寒武纪——三叠纪主要经历了从东冈瓦纳大陆西北缘裂解、到向劳亚大陆聚合的演化过程,北部长期为被动大陆边缘环境,南部主要为裂谷、持续裂解以及漂移过程中陆块地体增生拼合,主要为弧后前陆盆地或隆起。塔里木盆地一级层序地层、区域不整合事件、次级构造单元的构造演化等,与板块边界上构造活动及其板块运动轨迹的变化具有明显的一致性,板块边界上的挤压造山活动,造成盆地隆升以及盆地岩相古地理格局的剧烈变化。引发塔里木盆地早二叠世大火成岩省的地幔柱活动,垂向上也造成石炭系穹隆状剥蚀抬升。塔里木叠合盆地的形成是小陆块上不同时期不同盆地类型复合的产物,而在世界其他大板块上,它们在横向上可能处于不同位置,不会发生垂向叠合,而以不同时代的不同盆地出现。塔里木陆块较全球典型克拉通盆地规模小,在与周边陆块碰撞汇聚时受改造强烈,构造变形程度大并由陆块边缘向陆块内扩展,南、北两侧陆块边界上的强烈构造作用易于对整个盆地产生强烈影响,发育挤压期盆地隆起和前陆盆地等。 相似文献
20.
Antonio Introcaso Myriam P. Martínez Mario E. Gimnez Francisco Ruiz 《Gondwana Research》2004,7(4):1117-1132
A gravimetric and magnetometric study was carried out in the north-eastern portion of the Cuyania terrane and adjacent Pampia terrane. Gravimetric models permitted to interpret the occurrence of dense materials at the suture zone between the latter terranes. Magnetometric models led to propose the existence of different susceptibilities on either side of the suture. The Curie temperature point depth, representing the lower boundary of the magnetised crust, was found to be located at 25 km, consistent with the lower limit of the brittle crust delineated by seismic data; this unusually thick portion of the crust is thought to release stress producing significant seismicity.
Moho depths determined from seismic studies near western Sierras Pampeanas are significantly greater than those obtained from gravimetric crustal models.
Considering mass and gravity changes originated by the flat-slab Nazca plate along Cuyania and western Pampia terranes, it is possible to reconcile Moho thickness obtained either by seismic or by gravity data. Thus, topography and crustal thickness are controlled not only by erosion and shortening but by upper mantle heterogeneities produced by: (a) the oceanic subducted Nazca plate with “normal slope” also including asthenospheric materials between both continental and oceanic lithospheres; (b) flat-slab subducted Nazca plate (as shown in this work) without significant asthenospheric materials between both lithospheres. These changes influence the relationship between topographic altitudes and crustal thickness in different ways, differing from the simple Airy system relationship and modifying the crustal scale shortening calculation. These changes are significantly enlarged in the study area. Future changes in Nazca Plate slope will produce changes in the isostatic balance. 相似文献