共查询到20条相似文献，搜索用时 562 毫秒
1.
内蒙古东部及邻区石炭纪—二叠纪构造地层
格架与形成环境 总被引：1，自引：0，他引：1
构造带内的地层建造和区域展布主要受大地构造背景和古地理环境的双重控制。突出构造地层学方法,进行综合地层学研究,重点地层剖面实测与修订前人资料相结合,在恢复大地构造演化和沉积相分析的基础上,重新划分内蒙古东部及邻区石炭纪—二叠纪地层分区,并建立构造地层格架。2条构造线将研究区分隔成3个地层分区。西拉木伦河断裂南侧（华北地层分区）出露大陆边缘坳陷沉积和陆内裂陷槽充填,称为康保-赤峰地层小区。查干敖包-阿荣旗断裂至黑河一线北侧（兴安地层分区）属西伯利亚板块,呈现边缘坳陷沉积和裂陷槽充填的陆块南缘称东乌-龙江地层小区;而陆内坳陷沉积的北部范围称额尔古纳地层小区。2条构造线之间为板块增生带（内蒙草原地层分区）,自然分隔成锡林郭勒地层小区、科尔沁地层小区和松-辽地层小区,发育多岛洋-海槽-残余海槽的复杂环境。通过论述各岩组划分、对比和沉积相归属,构造地层格架尽可能反映当时的大地构造格局和沉积环境演变。 相似文献
2.
构造带内的地层建造和区域展布主要受大地构造背景和古地理环境的双重控制。突出构造地层学方法,进行综合地层学研究,重点地层剖面实测与修订前人资料相结合,在恢复大地构造演化和沉积相分析的基础上,重新划分内蒙古东部及邻区石炭纪—二叠纪地层分区,并建立构造地层格架。2条构造线将研究区分隔成3个地层分区。西拉木伦河断裂南侧（华北地层分区）出露大陆边缘坳陷沉积和陆内裂陷槽充填,称为康保-赤峰地层小区。查干敖包-阿荣旗断裂至黑河一线北侧（兴安地层分区）属西伯利亚板块,呈现边缘坳陷沉积和裂陷槽充填的陆块南缘称东乌-龙江地层小区;而陆内坳陷沉积的北部范围称额尔古纳地层小区。2条构造线之间为板块增生带（内蒙草原地层分区）,自然分隔成锡林郭勒地层小区、科尔沁地层小区和松-辽地层小区,发育多岛洋-海槽-残余海槽的复杂环境。通过论述各岩组划分、对比和沉积相归属,构造地层格架尽可能反映当时的大地构造格局和沉积环境演变。 相似文献
3.
Rocks of the Ventersdorp Supergroup were deposited in a system of northeast trending grabens on the Kaapvaal Craton approximately 2.64 Ga ago contemporary with a continental collision between the Kaapvaal and Zimbabwe Cratons. We suggest that it was this collision that initiated the Ventersdorp rifting. Individual grabens strike at high angles toward the continental collision zone now exposed in the Limpopo Province where late orogenic left-lateral strike-slip faulting and anatectic granites are recognized. We relate the Ventersdorp rift province to extension in the Kaapvaal Craton associated with the collision, and see some analogy with such rifts as the Shansi and Baikal Systems associated with the current India-Asia continental collision. 相似文献
4.
O. Dauteuil J. Bouffette F. Tournat B. Van Vliet-Lanoë J.C. Embry Y. Qut 《Tectonophysics》2005,404(3-4):203-216
In Iceland, the main deformation activity occurs not only in the active rift zone where volcanism and seismicity coexist in fissure swarms but also in the transfer zones (north and south) where the main part of the seismic activity is located. Many studies described extension and vertical displacement associated with rifting and magmatism inside this rift zone. They have classically assumed that no deformation occurs outside the rift zone. However, few studies have already been conducted outside the rift zone. This work focuses on an area west of the rift zone in the Akureyri area, which displays an anomalous topography. We illustrate an ENE tilting of 0.23° since approximately 17,000 years ago using ancient lacustrine shorelines mapped in detail with a differential GPS survey and analysis of SPOT images. This degree of tilting corresponds to a vertical displacement of 160 m, i.e., a deformation rate of 1 cm/year, which is close to values measured in the active zone. This long wavelength deformation is compatible both with (i) the topographic anomaly of the Akureyri area, and with (ii) the very diffuse microseismicity that affects northern Iceland. The origin of this tilting is discussed and the different hypotheses (glacial loading response, rift uplift, transform zone effect, thermal doming, local magmatic intrusion) are reviewed. Our results, structural data and the topography are more consistent with a local magmatic intrusion inducing local doming. This work is the first attempt at quantifying long-term deformation outside the rift zone in Iceland. 相似文献
5.
6.
喜马拉雅造山带由印度与欧亚大陆板块的陆陆碰撞而形成。为何在挤压造山的碰撞前缘形成代表垮塌的藏南裂谷系存在巨大的争议。回答这个问题需要对裂谷的地壳结构有一个全面的认识。各裂谷带的起始活动年代自西向东逐渐年轻。本研究选取喜马拉雅东部较为年轻的错那裂谷,利用密集台阵接收的远震数据,通过P波接收函数方法,揭示错那裂谷的精细地壳结构,进而通过地壳结构分析裂谷的形成。结果显示错那裂谷为全地壳尺度结构,裂谷下方莫霍面发生明显错断,且壳内结构侧向不连续发育显著。本研究表明裂谷的形成可能关联更大尺度的区域构造运动,单一的重力垮塌是否能形成地壳尺度的裂谷需要进一步研究。综合前人对藏南裂谷系区域的超钾岩和埃达克岩研究以及深部地球物理观测结果,推断因俯冲的印度板片撕裂导致软流圈物质上涌弱化了错那裂谷区域下地壳,并且结合研究区内喜马拉雅淡色花岗岩研究显示中上地壳也存在弱化现象。因此,结合本研究结果推测全地壳尺度裂谷的形成需要不同深度的地壳弱化。 相似文献
7.
Zorin Turutanov V. V. Mordvinova V. M. Kozhevnikov T. B. Yanovskaya A. V. Treussov 《Tectonophysics》2003,371(1-4):153-173
The main chain of SW–NE-striking Cenozoic half-grabens of the Baikal rift zone (BRZ) follows the frontal parts of Early Paleozoic thrusts, which have northwestern and northern vergency. Most of the large rift half-grabens are bounded by normal faults at the northwestern and northern sides. We suggest that the rift basins were formed as a result of transformation of ancient thrusts into normal listric faults during Cenozoic extension.Seismic velocities in the uppermost mantle beneath the whole rift zone are less than those in the mantle beneath the platform. This suggests thinning of the lithosphere under the rift zone by asthenosphere upwarp. The geometry of this upwarp and the southeastward spread of its material control the crustal extension in the rift zone. This NW–SE extension cannot be blocked by SW–NE compression generated by pressure from the Indian lithospheric block against Central Asia.The geochemical and isotopic data from Late Cenozoic volcanics suggest that the hot material in the asthenospheric upwarp is probably provided by mantle plumes. To distinguish and locate these plumes, we use regional isostatic gravity anomalies, calculated under the assumption that topography is only partially compensated by Moho depth variations. Variations of the lithosphere–asthenosphere discontinuity depth play a significant role in isostatic compensation. We construct three-dimensional gravity models of the plume tails. The results of this analysis of the gravity field are in agreement with the seismic data: the group velocities of long-period Rayleigh waves are reduced in the areas where most of the recognized plumes are located, and azimuthal seismic anisotropy shows that these plumes influence the flow directions in the mantle above their tails.The Baikal rift formation, like the Kenya, Rio Grande, and Rhine continental rifts [Achauer, U., Granet, M., 1997. Complexity of continental rifts as revealed by seismic tomography and gravity modeling. In: Jacob, A.W.B., Delvaux, D., Khan, M.A. (Eds.), Lithosphere Structure, Evolution and Sedimentation in Continental Rifts. Proceedings of the IGCP 400 Meeting, Dublin, March 20–22, 1997. Institute of Advanced Studies, Dublin, pp. 161–171], is controlled by the three following factors: (i) mantle plumes, (ii) older (prerift) linear lithosphere structures favorably positioned relative to the plumes, and (iii) favorable orientation of the far-field forces. 相似文献
8.
Dimensions of the Late Cretaceous-Paleocene Northeast Atlantic rift derived from Cenozoic subsidence
Jakob Skogseid 《Tectonophysics》1994,240(1-4):225-247
The distribution of Cenozoic subsidence across Northeast Atlantic volcanic margins have been evaluated to define the width of the rift zone and magnitude of extensional deformation. The subsidence profiles are corrected for the effects of lower-crustal magmatic bodies emplaced during continental break-up. The dimensions of the bodies have been derived from the crustal velocity structure. The width of the Late Cretaceous-Paleocene Northeast Atlantic rift zone was more than 300 km, and the lithospheric extension factor increases gradually towards the line of continental separation. A large number of high-quality seismic reflection data tied to scientific and commercial wells reveals that the initiation of extensional deformation preceded continental separation by ˜ 18 m.y. on the Vøring margin, off Norway. These results show that the Northeast Atlantic volcanic margins, commonly considered as typical volcanic margins indeed, have similar dimensions as non-volcanic margins, and as continental rifts. Thus, these margins contrast significantly with previously suggested evolutionary models based on narrow rift zones and formation during rapid lithospheric failure. The wide rift is compatible with volume of igneous rocks observed along these margins, and with a thermal anomaly similar to that associated with production of Northeast Atlantic oceanic lithosphere. 相似文献
9.
With oblique rifting, both extension perpendicular to the rift trend and shear parallel to the rift trend contribute to rift formation. The relative amounts of extension and shear depend on α, the acute angle between the rift trend and the relative displacement direction between opposite sides of the rift. Analytical and experimental (clay) models of combined extension and left-lateral shear suggest the fault patterns produced by oblique rifting. If α is less than 30°, conjugate sets of steeply dipping strike-slip faults form in rifts. Sinistral and dextral strike-slip faults trend subparallel and at large angles to the rift trend, respectively. If α is about 30°, strike-slip, oblique-slip and/or normal faults form in rifts. Faults with sinistral and dextral strike slip trend subparallel and at large angles to the rift trend, respectively. Normal faults strike about 30° counterclockwise from the rift trend. If α exceeds 30°, normal faults form in rifts. They have moderate dips and generally strike obliquely to the rift trend and to the relative displacement direction between opposite sides of the rift. If α equals 90°, the normal faults strike parallel to the rift trend and perpendicularly to the displacement direction.The modeling results apply to the Gulf of California and Gulf of Aden, two Tertiary continental rift systems produced by combined extension and shear. Our results explain the presence and trends of oblique-slip and strike-slip faults along the margins of the Gulf of California and the oblique trend (relative to the rift trend) of many normal faults along the margins of both the Gulf of California and the Gulf of Aden. 相似文献
10.
长期以来,学者们普遍认为垂直于喜马拉雅造山带的南北向裂谷是东西向伸展的构造形迹。现代GPS观测数据却显示,喜马拉雅造山带东西位移(分)量很小,甚至为零。综合前人资料,喜马拉雅造山过程可划分为热造山(25~13Ma)及造山后(13Ma)冷却两个时期,热造山期具有受热膨胀,物质向外运移的特点,高喜马拉雅热隆挤出并触发各主要断裂(MCT、STD、GCT)活动,印度板块向北汇聚速率下降。造山后则表现为冷却收缩,前期构造-热活动停止或减弱,印度板块向北汇聚加速。研究认为,南北向裂谷与高喜马拉雅等冷却过程的东西向收缩。且被局限于东、西两个构造结之间有关。并据此建立了裂谷的冷缩成因模型,模型估值与地质事实很吻合。 相似文献
11.
The study of Precambrian rifts, such as those found in the Tarim craton, is of great interest in the field of deep petroleum exploration as the source rocks of the rifts are depositional deep lacustrine facies. In this study, two buried rifts (Manjiaer and Wushi rifts) that may exist in the Tarim craton are identified based on the seismic profiles. Through the analysis of the outcrops and stratigraphic columns of the identified rifts, two types of rifts are classified and their evolution is divided into different stages. The evolution of the Manjiaer rift, which experiences frequent volcanic activity, can be roughly divided into three rift periods. Meanwhile, the evolution of the Wushi rift can be simply divided into two rift periods during the Nanhuan–Sinian period. A noticeably stronger activity of the Manjiaer rift in comparison with that of the Wushi rift was noted. The paleogeography of the Proterozoic Tarim craton was also reconstructed, and the prospect for deep petroleum exploration in the Tarim craton is proposed. 相似文献
12.
The geological and geophysical data primarily on the structure of the upper sedimentary sequence of the northern Knipovich Ridge (Norwegian-Greenland Basin) that were obtained during Cruise 24 of the R/V Akademik Nikolai Strakhov are considered. These data indicate that the recent kinematics of the northern Knipovich Ridge is determined by dextral strike-slip displacements along the Molloy Fracture Zone (315° NW). This stress field is superimposed by a system related to rifting and latitudinal opening of rifts belonging to the ridge proper. Thus, the structural elements formed under the effect of two stress fields are combined in this district. Several stages of tectonic movements are definable. The first stage (prior to 500 ka ago) is marked by the dominant normal faults, which are overlain by the lower and upper sedimentary sequences. The second stage (prior to 120–100 ka ago) is characterized by development of normal and reverse faults, which displace the lower sequence and are overlain by the upper sequence. Both younger and older structural features reveal peaks of tectonic activity separated by intermediate quiet periods 50–60 ka long. The stress field of the regional strike-slip faulting is realized in numerous oblique NE-trending normal and normal-strike-slip faults that divide the rift valley and its walls into the segments of different sizes. Their strike (20°–30° NE) is consistent with a system of secondary antithetic sinistral strike-slip faults. The system of depressions located 40 km west of the rift valley axis may be considered a paleorift zone that is conjugated at 78°07′ N and 5°20′ W with the NW-trending fault marked by the main dextral offset. The stress field that existed at this stage was identical to the recent one. The rift valley axis migrated eastward to its present-day position approximately 2 Ma ago (if the spreading rate of ～0.7 cm/yr is accepted). The obtained data substantially refine the understanding of the initial breakup of continents with the formation of oceanic structural elements. The neotectonic stage is characterized by combination of different stress fields that resulted in the formation of a complex system of tectonic structural units, including those located beyond the recent extension zone along the rift axis of the Knipovich Ridge. The tectonic deformations occurred throughout the neotectonic stage as discrete recurrent events. 相似文献
13.
M.R. Novoselova 《Tectonophysics》1978,45(1):95-100
The magnetic field of the Baikal rift zone differs both from that of adjacent territories and from oceanic rifts in its character and intensity. There is no strip-like structure of the field in Baikal. It is assumed that the thickness of the magnetic anomaly-generating layer in this region is small, due to a high thermal gradient in the crust. Basic intrusions are predicted at depths up to 18 km. There is evidence of instability in the geothermal field. 相似文献
14.
Pietro Passerini Marta Marcucci Giovanni Sguazzoni Leonardo Zan Abdourahman Omar Haga 《地学学报》1991,3(6):607-618
Slickenside studies in regions of crustal spreading such as Iceland and the Afar Depression, East Africa, reveal that a significant number of faults parallel and close to rift axes are strike-slip rather than normal. Therefore, the pattern of brittle deformation in these regions does not conform to the classic two-dimensional schemes of oceanic tectonics and pre-oceanic rifting. Dip-slip and strike-slip faulting presumably alternated along or in the vicinity of spreading axes, indicate a varying stress field and a combination of transverse and longitudinal movements. In Iceland, strike-slip faults parallel to rifts are observed both west and east of the rift system as well as in a median area between overlapping rifts; the mechanisms proposed for their origin include accommodation of oblique convergence or divergence of crustal sections due to variations of spreading directions along axis and the interaction of overlapping rifts. In the Afar Depression this kind of fault is recorded west of the rift of Asal and can be imputed to reflect an interaction among rifts in the vicinity of the Afar triple junction. Rift-parallel strike-slip faults cannot however be assumed to be a feature of all crustal spreading axes due to the peculiarity of the examined regions: both of them are hot-spot areas and the Afar Depression lies at a triple junction. 相似文献
15.
Devana Chasma is a rift system on Venus formed in association with the Beta Regio and Phoebe Regio volcanic highlands, which are interpreted as mantle plumes. We present a new analysis of a 2500-km-long segment of Devana. Based on the rift topography, the horizontal extension across the rift boundary faults is 3–9 km. This is a lower bound on the total rift extension because the altimetry does not resolve the topographic relief across the numerous faults that are visible in radar images of the rift floor. The total extension across Devana is approximately 20 km, similar in magnitude to continental rift systems on Earth. Rift flank elevations are up to 3.1 km in the regions nearest the mantle plumes and decay strongly with increasing distance from the plumes, indicating a strong thermal component to the rift flank topography, unlike the situation usually reported for terrestrial rifts. As on Earth, there is also a flexural uplift component to the flank topography. Rift depths are up to 2.5 km below the surrounding plains, with considerable along-strike variability. There is a 600 km lateral offset along Devana Chasma near the mid-point between the two mantle plumes. Devana most likely formed as two distinct rifts due to the horizontal stresses created by outflow from the upwelling plumes. The offset zone formed as a result of the interaction between the two rift tips, which requires that upwelling at the two mantle plumes overlapped in time. 相似文献
16.
Yu. G. Tsekhovskii O. V. Yapaskurt I. E. Stukalova 《Moscow University Geology Bulletin》2014,69(5):347-355
An analysis of continental sedimentogenesis in Mesozoic rifts of the Transbaikal region and Mongolia, as well as in the Cenozoic Baikal rift zone, revealed a succession of volcanic-sedimentary formations, which constitute the sedimentary cover. The peculiar sedimentation features reflect exogenic processes that are characteristic of rift structures and the influence of deep-seated (exogenic and catagenic) sources. It is proposed to define a specific, rift, type of sedimentogenesis. 相似文献
17.
M.E.M. De Smet 《Tectonophysics》1984,107(1-2)
Regional structural trends in the Caravaca-Huescar area, forming the central part of the External Zone in the Betic Cordilleras, indicate that deformation of the area results from right lateral wrenching, subparallel to the paleogeographic zonation. The structural trends do not fit the nappe interpretation generally used elsewhere in the External Zone.Arguments for wrenching in the area are: the structural inverse symmetry with respect to a central transcurrent fault zone (the Crevillente Fault Zone), the distributional pattern of stratigraphic anomalies and types of deformation, and the outcrop pattern of the paleogeographic zones.It is argued that certain tectonic units in the area, formerly interpreted as klippes in a nappe configuration, form centers of “flower structures” and are vertically squeezed out blocks.A theoretical model is sketched, illustrating the evolution of a wrench zone under the stratigraphic conditions of the studied area and resulting in its present characteristics.Many of the features of the Caravaca-Huescar area are also present elsewhere in the External Zone and support the idea that wrenching was a major deformational mechanism. It is therefore suggested that the External Zone should in general not be described in terms of a nappe structure, as has been done so far, but in terms of a strike-slip orogen or a wrenched continental margin. 相似文献
18.
大陆裂谷研究中的几个前沿课题 总被引：6，自引：1，他引：6
本文强调研究大陆裂谷具有重要的理论和实践意义，重点评述了当前大陆裂谷研究中的几个前沿课题：（１）建立大陆裂谷深部结构模式，介绍了张性破裂模式和地幔柱模式；（２）研究大陆裂谷与板块构造关系，认为大陆裂谷的发育与变化的板块运动密切相关；（３）探讨大陆裂谷的热流作用，证实了裂谷深部存在高温驱动的流体和热循环，推测这里可能就是幼年大洋产生的地带；（４）总结大陆裂谷成因类型，根据地球动力学状态划分了五种类型；（５）完善大陆裂谷研究思路与方法，提出多数大陆裂谷为一复杂的动力体系，系统论是全面研究这一复杂动力体系的有效方法。 相似文献
19.
The cartographic, sedimentologic and stratigraphic studies carried out on the Mesozoic deposits in the border zone between the Middle and the High Moroccan Atlas (regions of Naour and Aghbala) led us to specify the lithology of formations, the significant differences of thickness and the angular unconformities as well as stratigraphic hiatuses. All of this indicates a tectonic regime of transcurrent faults from the Bajocian–Bathonian period along the major fault zone “Aghbala–Afourer” in a N70° direction. A sinistral strike-slip movement along this major fault zone induced the development of folded and fractured zones in a N120° direction, which limited a small trough filled by the red continental formations. The whole system is covered thereafter by lower Cretaceous deposits. 相似文献
20.
On the north coast of Iceland, the rift zone in North Iceland is shifted about 120 km to the west where it meets with, and joins, the mid-ocean Kolbeinsey ridge. This shift occurs along the Tjörnes fracture zone, an 80-km-wide zone of high seismicity, which is an oblique (non-perpendicular) transform fault. There are two main seismic lineaments within the Tjörnes fracture zone, one of which continues on land as a 25-km-long WNW-trending strike-slip fault. This fault, referred to as the Husavik fault, meets with, and joins, north-trending normal faults of the Theistareykir fissure swarm in the axial rift zone. The most clear-cut of these junctions occurs in a basaltic pahoehoe lava flow, of Holocene age, where the Husavik fault joins a large normal fault called Gudfinnugja. At this junction, the Husavik fault strikes N55°W, whereas Gudfinnugja strikes N5°E, so that they meet at an angle of 60°. The direction of the spreading vector in North Iceland is about N73°W, which is neither parallel with the strike of the Husavik fault nor perpendicular to the strike of the Gudfinnugja fault. During rifting episodes there is thus a slight opening on the Husavik fault as well as a considerable dextral strike-slip movement along the Gudfinnugja fault. Consequently, in the Holocene lava flow, there are tension fractures, collapse structures and pressure ridges along the Husavik fault, and pressure ridges and dextral pull-apart structures subparallel with the Gudfinnugja fault. The 60° angle between the Husavik strike-slip fault and the Gudfinnugja normal fault is the same as the angle between the Tjörnes fracture zone transform fault and the adjacent axial rift zones of North Iceland and the Kolbeinsey ridge. The junction between the faults of Husavik and Gudfinnugja may thus be viewed as a smaller-scale analogy to the junction between this transform fault and the nearby ridge segments. Using the results of photoelastic and finite-element studies, a model is provided for the tectonic development of these junctions. The model is based on an analogy between two offset cuts (mode I fractures) loaded in tension and segments of the axial rift zones (or parts thereof in the case of the Husavik fault). The results indicate that the Tjörnes fracture zone in general and the Husavik fault in particular, developed along zones of maximum shear stress. Furthermore, the model suggests that, as the ridge-segments propagate towards a zero-underlapping configuration, the angle between them and the associated major strike-slip faults gradually increases. This conclusion is supported by the trends of the main seismic lineaments of the Tjörnes fracture zone. 相似文献