根据碎屑白云母40Ar/39Ar年龄追索喜马拉雅造山带的剥落历史——对青藏高原隆升过程的启示   总被引：1，自引：1，他引：0  

段亮 《地质通报》2010,29(1):70-78

对喜马拉雅前陆盆地和孟加拉海扇中各地层的碎屑白云母40Ar/39Ar资料的系统分析揭示了喜马拉雅造山带自印度-欧亚板块碰撞开始造山以来的整个剥落历史: 剥落速率开始较为稳定,然后开始上升,在22Ma左右达到峰值,为4~5mm/a,随后急剧下降,最终以2mm/a的速率保持平稳。喜马拉雅造山带与青藏高原周缘剥落历史的对比约束了印度-欧亚板块碰撞造成青藏高原东缘和北缘的不同反应方式。即开始时的挤压主要被青藏高原北缘的大规模左旋走滑吸收, 到30Ma左右,喜马拉雅造山带冷却、剥落速率显著增强,北缘左旋走滑造成的柴达木地块的向东运动被华北板块阻挡而停滞,因此在北缘发生了一些重要的冷却和抬升剥落事件。至18Ma左右,喜马拉雅造山带的冷却、剥落速率继续增高并维持在较高水平,而该时间段内无论是北缘还是东缘,均未发生显著的抬升剥落事件,因此青藏高原的整体隆升和地壳增厚可能发生在此期间。中新世末—上新世初开始至今,青藏高原东缘龙门山地区发生了一些显著的抬升剥落事件,导致了大量的山崩和河流侵蚀,即此时来自喜马拉雅的挤压主要被青藏高原向东方向的地壳逃逸所吸收。  相似文献   

Morpho‐sedimentary records at the Brahmaputra River exit,NE Himalaya: climate–tectonic interplay during the Late Pleistocene–Holocene     

Pradeep Srivastava  Surendra S. Bhakuni  Khayingshing Luirei  Dileep K. Misra 《第四纪科学杂志》2009,24(2):175-188

Morphological and sedimentary records at the exit of Brahmaputra River at Pasighat in the NE Himalaya inform about the climate–tectonic interplay during the past ca. 15 ka. The geomorphology of the area comprises (1) fan terrace T₃, (2) a high‐angle fan (3) terrace T₂, (4) terrace T₁ and (5) a low‐angle fan. Geomorphic consideration suggests that the fan terrace T₃ and high‐angle fans are the oldest units and were coeval. The low‐angle fan is the youngest geomorphic unit. Sedimentological studies and optically stimulated luminescence chronology suggest that (i) fan terrace T₃ formed between 13 and 10.5 ka and comprised multiple events of debris flows separated by the aggradation as channel bars in a braided river environment; (ii) the high‐angle fan formed during 15–10 ka and comprises channel bar aggradation in braided river conditions; (iii) terrace T₂ formed during 10–8 ka due to aggradation in a braided channel environment with lesser events of debris flows; (iv) terrace T₁ formed during <7 and 3 ka took place as bars of the braided river. Sudden coarsening of the sediment indicated a tectonic rejuvenation in the provenance region between 7 and 3 ka; and (v) the low‐angle fans dated to <3 ka formed due to aggradation in a small tributary joining the Brahmaputra River. This implies a phase when the main channel of the Brahmaputra did not flood regularly and the tributaries were actively aggrading. The sedimentation style and incision of these geomorphic units responded to contemporary climatic changes and uplift in the Siwalik range along the Himalayan Frontal Fault. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

造山带挤出构造   总被引：14，自引：0，他引：14  

曾佐勋  杨巍然  刘立林  郭铁鹰  Franz Neubauer 《地质科技情报》2001,20(1):1-7

挤出构造模式已经从二维变形进入三维变形研究，在喜马拉雅造山带，高喜马拉雅结晶地体沿北倾的主中央逆冲断层和北倾 的绒布寺正断层，表现为相对刚性体之间的韧性体的楔状挤出。非连续介质大变形有限元数值模拟结果为这一模式提供了力学依据。在前人工作的基础上，提出了东阿尔卑斯三维管状挤出模式，将上部脆性层划分出北部左行平移带，南部右行平移带和中部挤出楔，中部韧性层在南阿尔卑斯和欧洲前陆碰撞过程中，既有垂向挤出，也有侧向挤出，在平行缩短方向的剖面上，由箱状背形隆起演化成逆－逆断层组合的楔状挤出，形成三角断面的管状，在垂直缩短方向的剖面上，中部韧性层呈不均匀流动，形成管状层流－韧性层中心为纯剪切，上部和侧部为简单剪切，在陕甘川邻接区，由于祁连山－北秦岭加里东喧向南的推挤和川西前陆的刚性阻挡，造成西秦岭和东松潘－甘孜复合造山体的三维滑脱挤出，以北西西向玛曲－略阳滑脱逆冲断裂和北东向青川一茂县滑脱逆冲断裂为界，将陕甘川邻接区的三维滑脱挤出复合造山体划分为西秦岭滑脱挤出带，摩天岭0若尔盖滑脱挤出楔和龙门山滑脱挤出逆冲椎覆带，以近南北向岷江滑脱逆冲断裂为界将滑脱挤出楔进一步划分成摩天岭滑脱挤出体和苦尔盖滑脱挤出体，除了不同构造单元的不均匀隆升外，摩天岭还表现出向西的侧向挤出。  相似文献   

Detailed analysis of successive pTRMs carried by pyrrhotite in Himalayan metacarbonates: an example from Hidden Valley, Central Nepal     

C. Crouzet  H. Stang  E. Appel  E. Schill  P. Gautam 《Geophysical Journal International》2001,146(3):607-618

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Gravity anomalies, crustal structure and thermo-mechanical support of the Himalaya of Central Nepal     

R. Cattin  G. Martelet  P. Henry  J. P. Avouac  M. Diament  T. R. Shakya 《Geophysical Journal International》2001,147(2):381-392

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On the aftershock sequence of a 4.6 mb earthquake of the Garhwal Himalaya     

Irene Sarkar  Ramesh Chander  Dalia Chatterjee 《Journal of Earth System Science》1995,104(4):683-691

Locally recorded data for eighteen aftershocks of a magnitude(m_b) 4.6 earthquake occurring near Ukhimath in the Garhwal Himalaya were analysed. A master event technique was adopted to locate seventeen individual aftershock hypocentres relative to the hypocentre of the eighteenth aftershock chosen as the master event. The aftershock epicentres define an approximately 30 km² rupture zone commensurate with the magnitude of the earthquake. The distribution of epicentres within this zone and the limited amount of first motion data support the view that a group of parallel, sub-vertical, sinistral strike-slip faults oriented N46°, transverse to the regional NW-SE trend of the Garhwal Himalaya, was involved in this seismic episode. Since the estimated focal depth range for aftershocks of this sequence is 3–14 km, we infer that this transverse fault zone extends through the upper crustal layer to a depth of 14 km at least.  相似文献   

The effects of deforestation on slope and channel evolution in the tectonically active Darjeeling Himalaya     

Wojciech Froehlich  Leszek Starkel 《地球表面变化过程与地形》1993,18(3):285-290

The main indicators of Quaternary tectonic uplift are the young mountain slopes of the Darjeeling Himalaya, rising straight above the Ganga–Brahmaputra foredeep, fragments of uplifted river terraces and fresh fault scarps. Evidence for the continuation of the uplift includes downcutting of the Tista and other straight rivers in the bedrock, continuing aggradation in the plains and overriding of the metamorphic rocks on the alluvia. Owing to deforestation and extensive land use, the earlier natural tendency of a dominance of channel incision over slope degradation has changed to prevailing aggradation, even in steep valley reaches, caused by intensive slope mass movements and the overloading of the mountain creeks. Aggradation progresses upstream along the rivers dissecting the mountain front.  相似文献   

The Triassic of the Thakkhola (Nepal). II: Paleolatitudes and comparison with other Eastern Tethyan Margins of Gondwana     

J. G. Ogg  U. von Rad 《International Journal of Earth Sciences》1994,83(1):107-129

During the Triassic, the Thakkhola region of the Nepal Himalaya was part of the broad continental shelf of Gondwana facing a wide Eastern Tethys ocean. This margin was continuous from Arabia to Northwest Australia and spanned tropical and temperate latitudes.A compilation of Permian, Triassic and early Jurassic paleomagnetic data from the reconstructed Gondwana blocks indicates that the margin was progressively shifting northward into more tropical latitudes. The Thakkhola region was approximately 55° S during Late Permian, 40° S during Early Triassic, 30° S during Middle Triassic and 25° S during Late Triassic. This paleolatitude change produced a general increase in the relative importance of carbonate deposition through the Triassic on the Himalaya and Australian margins. Regional tectonics were important in governing local subsidence rates and influx of terrigenous clastics to these Gondwana margins; but eustatic sea-level changes provide a regional and global correlation of major marine transgressions, prograding margin deposits and shallowing-upward successions. A general mega-cycle characterizes the Triassic beginning with a major transgression at the base of the Triassic, followed by a general shallowing-upward of facies during Middle and Late Triassic, and climaxing with a regression in the latest Triassic.  相似文献   

Evaluation of crystallization temperatures of mineral paragenesis in consolidated crust and uppermost mantle from explosion seismology data     

A. P. Tarkov 《Pure and Applied Geophysics》1980,119(4):854-864

In terms of the general endogeneous evolution of the lithosphere, the continental crystalline crust and the uppermost mantle, formed by regional metamorphic and magmatic processes, show mineral paragenesis stratification, expressed by a regular mineral sequence. The continuous macrolayering of mineral paragenesis through lithospheric depth profile is caused by phase transformations and variations in composition of complex natural systems, and affects the vertical distribution of seismic velocities,V _p,V _s, and other physical parameters.To evaluate palaeotemperatures (crystallization temperatures of mineral paragenesis), consistentV _pandV _s (Z) velocity models for the consolidated crust of two regionally separated areas of different geological structures — Precambrian shield (Voronezh Massif) and a young fold-mountain structure in the central part of the Transasian orogeneous belt (Himalaya) — are used as starting data.The velocity models are recalculated into (Z) and (Z) profiles (Z) being the seismic parameter. (Z) the Debye temperature). These, according to Debye theory, allow the determination of variations in entropy, thermodynamic and temperature gradients at the time of crustal generation.For the two regions chosen, palaeotemperature distributions are eventually calculated for the depth intervals given by velocity profiles. Crystallization temperatures calculated from seismic data show good agrrement with the values obtained from mineralogical thermobarometry.  相似文献   

藏南康马奥陶系及其底砾岩的发现并初论喜马拉雅沉积盖层与统一变质基底的关系   总被引：12，自引：9，他引：12  

周志广刘文灿  梁定益 《地质通报》2004,23(7):655-663

藏南北喜马拉雅拉轨岗日带康马岩体西南侧，奥陶系及其底砾岩覆盖于前奥陶系拉轨岗日群(POL)之上，后者被515～485Ma拉轨岗日构造穹隆带花岗岩侵入，沿不整合面又被泛非运动最晚期的基性脉岩侵入。奥陶系与前奥陶系的接触关系为伸展不整合，与喜马拉雅甚至冈底斯带有关剖面完全可以对比。这一不整合面即是冈瓦纳大陆北缘统一变质基底和沉积盖层的分界；冈瓦纳大陆统一变质基底的形成始于震旦纪末的“泛非运动”，其终止时间在喜屿拉雅及以北地区可以延续至寒武纪—奥陶纪之交。表现为区域上不断的伸展—拉张—裂解的构造环境。由此可以认为伸展构造亦是控制统一变质基底与沉积盖层的形成机制之一。  相似文献