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131.
前陆及前陆盆地的概念历来有多种定义,这些概念应用于中国中西部时有混乱,建议采用“复活前陆盆地”一词。前陆盆地内部结构单元包括活动翼、前渊(或称深坳陷)、稳定前陆斜坡和前隆,这四部分有成因联系,研究中应纳入一个前陆系统进行分析。以国外和中国中西部的多个盆地实例阐述了正确认识和鉴定前陆盆地的内部结构、前渊迁移、空间上沉积楔形态及含油气性等重要特征是对前陆盆地含油气评价和选区评价的重要前提。提出当今准噶尔盆地的地质构造格局是一个由活动翼(天山山前)、前渊(昌吉凹陷)和广大稳定前陆斜坡构成的复活前陆盆地。建议应编制两张准噶尔盆地中、新生代构造区划图。提出在盆地的油气勘探中不能唯“源控论”,勘探目标还应放在背斜以外的其它类型圈闭上。  相似文献   
132.
西藏晚三叠世北羌塘前陆盆地构造层序及充填样式   总被引:16,自引:2,他引:16  
晚三叠世北羌塘前陆盆地为处于金沙江缝合带南缘的周缘前陆盆地,其中充填了厚度大于2 500 m的晚三叠世肖茶卡群,自南向北可分出4个沉积相带,显示为北厚南薄的楔形沉积体,具双物源、双古流向以及沉降中心和沉积中心不一致性等特点,以不整合面为界可将其分为2个构造层序,下部构造层序以诺利期复理石建造为特征,上部构造层序以瑞替期磨拉石建造为特征.  相似文献   
133.
四川类前陆盆地须家河组层序—岩相古地理特征   总被引:20,自引:2,他引:18  
通过对四川盆地的构造格局和盆—山耦合关系分析,确定该盆地属于类前陆盆地,晚三叠世须家河期具备以川中古隆起为中心的,由川西坳陷、川东北坳陷、渝东—川东南坳陷三个盆—山耦合次系统组成的“三坳围一隆”构造—沉积格局。以盆缘地表及盆地内钻井剖面的须家河组和香溪群地层划分、沉积相和层序地层分析、基准面旋回划分及区域等时对比为依据,将须家河组划分为全盆地范围内可追踪对比的2个超长期(SLSC1—SLSC2)和5个长期(LSC1—LSC5)基准面旋回层序。以此为基础,选择各长期旋回层序上升和下降半旋回相域为等时地层单元编制四川盆地层序—岩相古地理图。编图结果表明须家河组各时期岩相古地理面貌、相带展布规律和沉降—沉积中心及其迁移方向,严格受龙门山和米仓山—大巴山两造山带非同步的、但交替发育的逆冲推覆作用与“三坳围一隆”构造—沉积格局控制,盆—山间的耦合关系具有造山带隆升蚀顶与盆地横向生长、沉降、充填的物质循环平衡过程。这一独具特色的构造—沉积格局始终控制着须家河组各超长期、长期旋回层序的沉积充填作用,古地理面貌、生储盖组合特征和围绕川中古隆起为中心的油气成藏规律。  相似文献   
134.
碰撞带前陆盆地的建立是大陆碰撞的直接标志和随后造山带构造变形的忠实记录。本文对欧亚板块与印度板块碰撞前后发育在拉萨地块上的冈底斯弧背前陆盆地,同碰撞产生的雅鲁藏布江周缘前陆盆地,以及碰撞后陆内变形产生的喜马拉雅前陆盆地的沉积地层演化以及碎屑锆石物源特征等进行了系统分析,结合前人及我们近些年的研究成果,认为冈底斯岛弧北侧发育一个典型的弧背前陆盆地系统而不是以前普遍接受的伸展盆地。除传统认为的喜马拉雅前陆盆地系统外,在碰撞造山带中还发育一个雅鲁藏布江前陆盆地系统,它是欧亚板块与印度板块碰撞以后,欧亚板块加载到印度被动大陆边缘产生的典型周缘前陆盆地。上述2个造山带前陆盆地系统的识别,大大提高了对新特提斯洋俯冲、碰撞过程的认识。造山带前陆盆地证据指示,新特提斯洋至少于140 Ma以前就已开始俯冲, 110 Ma俯冲速度开始提高,在65 Ma前后印度大陆与欧亚大陆发生碰撞,喜马拉雅山于40 Ma开始隆升,其剥蚀物质大量堆积在喜马拉雅前陆盆地中。  相似文献   
135.
The Oligocene to present evolution of the North Patagonian Andes is analyzed linking geological and geophysical data in order to decipher the deformational processes that acted through time and relate them to basin formation processes. Seismic reflection profiles reveal the shallow structure of the retroarc area where contractional structures, associated with Oligocene to early Miocene inverted extensional depocenters, are partially onlapped by early to late Miocene synorogenic deposits. From the construction of five structural cross sections along the retroarc area between 40° and 43°30′ S, constrained by surface, gravity and seismic data, a shortening gradient is observed along Andean strike. The highest shortening of 18.7 km (15.34%) is determined near 41°30′ S coincidentally with maximum mean topographic values on the eastern Andean slope, where basement blocks were uplifted in the orogenic front area, and the deepest and broadest synorogenic depocenters were formed towards the foreland. Additionally, eastward shifting of Miocene calc-alkaline rocks occurred at these latitudes, which is interpreted as indicative of a change in the subduction parameters at this time. Deep crustal retroarc structure is evaluated through inversion of gravity models that made possible to infer Moho attenuated zones. These coincide with the occurrence of younger than 5 Ma within-plate volcanics as well as with crustal thermal anomalies suggested by shallowing of the Curie isotherm calculated from magnetic data. Younger volcanism and thermal anomalies are explained by slab steepening since early Pliocene, after a mild-shallow subduction setting in the middle to late Miocene, age of the main compressive event.  相似文献   
136.
Werner Fielitz  Ioan Seghedi   《Tectonophysics》2005,410(1-4):111-136
Middle Miocene (Sarmatian) convergence created the fold and thrust belt of the Eastern Carpathians of Romania, which subsequently experienced post-collisional crustal deformation combined with calc-alkaline and alkalic-basaltic volcanism in late Miocene–Quaternary time. This deformation led to the rise of the Cǎlimani–Gurghiu–Harghita volcanic mountains and to the subsidence of the N–S-oriented intramontane Borsec/Bilbor–Gheorgheni–Ciuc and Braşov pull-apart basins, and the E-oriented monocline-related Fǎgǎraş basin. The regional drainage network is the composite of:
(1) Older E-, SE- and S-flowing rivers, which cross the Carpathians, radiate towards the foreland and were probably established during the Middle Miocene (Sarmatian) collision event.

(2) A more recent drainage system related to the contemporaneous development of the volcanoes and intramontaneous basins, which generally drains westward into the Transylvanian Basin since late Miocene time and has been capturing the older river system.

The older river drainage system has also been modified by Late Pliocene–Quaternary folding, thrusting and monoclinal tilting along the Pericarpathian orogenic front and by reactivated transverse high angle basement faults, which cross the Eastern Carpathian foreland.  相似文献   

137.
沉积基准面旋回对陆相盆地砂岩储层的物性特征具有重要的控制作用.本文以高分辨率层序地层学理论为指导,通过对露头、测井、岩心资料的分析,在库车前陆盆地克拉2气田白垩系中识别出3种不同级别的基准面旋回,分别是中期旋回、短期旋回及超短期旋回,并探讨了砂岩储层物性分布与不同级别基准面旋回的关系.研究发现,对于同种成因类型的砂体,随着基准面的上升,其孔隙度、渗透率有下降趋势.在基准面较低的情况下,易形成高孔、高渗的储层.在下降半旋回与上升半旋回的转换点附近,一般为一组或一段地层中最大的孔隙度和渗透率发育的层位.  相似文献   
138.
Lateral variations in lithospheric strength have been adopted often in flexural modeling (both 2D and 3D) to better fit the observed basement deflections, typically supported by gravity data. This approach provides essentially a “snap-shot” of the role of lithosphere strength in determining the present day geometry.In contrast, we investigate and quantify the effects of a lateral change in lithospheric strength on the evolution of the foredeep in front of an advancing orogen. Transitions in lithospheric strength are common in the foreland of orogens and show large variations in the width of the transition zone and the strength difference. Former passive margins, for instance, will display strength changes distributed over several tens to hundreds of kilometers. Other transitions may originate from juxtaposition or accretion of pieces of lithosphere with different properties and may be characterized by a much smaller width than former passive margins.In our modeling, a constant load, representing an advancing orogenic belt, is displaced towards and across a transition from a weak to a strong plate in a 2D elastic thin plate model. The effect of different transition widths and strength contrasts on foredeep geometry and bending stress is investigated. Interference of flexural wavelengths across the transition affects foredeep geometry by causing rapid basin widening, oscillation of the bulge and volume increase. The bending stresses are found to concentrate and amplify around the strength transition. Large transition gradients, i.e. large strength contrast or small transition width, cause the highest rates of change.Basin widening caused by the orogenic load advancing towards the transition between the East European Craton and the Moesian Platform, appears to control the Sarmatian transgression over the East Carpathian foreland in Romania.  相似文献   
139.
Economic concentrations of detrital gold are rare in young foreland basins due to paucity of significant gold sources, and a paucity of sediment recycling processes during filling of the foreland basin. Gold shed into the foreland basins is typically widely dispersed in an overwhelming volume of immature basin-fill detritus of no economic significance. In the actively forming Canterbury Basin of New Zealand, minor gold concentration occurs at the mountain front in the bed of the Rakaia River, and 60 km downstream on beaches and the crest of foredunes at the river mouth. The Cretaceous–Tertiary Denver and Western Canada Basins in North America also have minor gold concentrations at the mountain front, and minor gold dispersal into the basin. Tectonic quiescence in the middle Tertiary in the Denver Basin kept gold within 20 km of the mountain front, where renewed uplift in late Tertiary caused minor economic concentrations to form in modern streams. Gold has been transported ca. 200 km across the Western Canada basin by progressive recycling of gravel during slow (ca. 10 to 50 m/Ma) middle Tertiary–Recent regional uplift and tilting, but little concentration has occurred. Development of significant placers in a foreland basin, the generally accepted setting for the Witwatersrand Au-U palaeoplacers, appears to require specific tectonic conditions during and/or after basin evolution to drive the sedimentary recycling necessary for significant placer development. Such tectonic conditions have not occurred in an any of the three young foreland basins examined in this study.  相似文献   
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