Geophysical transects of the Labrador Sea: Labrador to southwest Greenland

In 1977 the Federal Institute for Geosciences and Natural Resources, Hannover, carried out a large scale multichannel reflection seismic survey in the Labrador Sea. This survey provided an opportunity for the direct comparison of the geologic structure of the Labrador and Greenland margins. The seismic records across the Labrador Shelf show a thick, prograding sedimentary wedge consisting of several seismic sequences onlapping an acoustic basement that dips steeply seaward. The surface of the acoustic basement is irregular below the continental slope, indicating Late Cretaceous—Early Tertiary faulting. The thick sedimentary section below the slope is divided by an unconformity, tentatively identified as Late Tertiary in age, into two seismic megasequencies which can be subdivided. The acoustic basement on the Greenland side is also strongly faulted but is overlain, in the south, by a thin sedimentary section. The sediment cover thickens on the Greenland Shelf to the north as the shelf becomes wider.As with more southerly parts of the western Atlantic margin, a positive free-air anomaly (30–50 mgal) lies landward of the shelf break off Labrador and a smaller negative anomaly follows the base of the slope. Similar, but generally narrower features are observed along the Greenland margin. West of the negative anomaly off the Greenland slope a narrow band of lower amplitude positive anomalies tends to be associated with an acoustic basement high observed in the reflection profiles. A landward negative gradient in the simple Airy isostatic anomaly across this margin suggests that the ocean—continent boundary is related to this high.Detailed magnetic measurements across the northern Labrador margin show that well-developed oceanic anomalies trending north-northwest lie east of the large Labrador Shelf gravity high, beyond the 2000 m isobath. Landward of these magnetic anomalies is a quiet magnetic zone within which the linear gravity high is parallel to the shelf break and correlates with a deep, sediment-filled basin. It is inferred that oceanic-type crust or greatly-attenuated continental crust underlies this basin and that continental crust thickens markedly westward of the gravity high over a distance of about 50 km.     

Development of regional uplift and uplift-related strata in Gunsan Basin,Yellow Sea: implications for Cenozoic crustal extension

ABSTRACT

The Mesozoic–Cenozoic Gunsan Basin is the northeastern part of the Northern South Yellow Sea Basin between eastern China and the Korean Peninsula. On the basis of seismic interpretation, this study presents and interprets geologic features of regionally uplifted structures, the Haema Arch, located in the central western part of the basin. The Haema Arch is defined as dome-shaped uplift complexes, 95 km long and 60 km wide. It is characterized by prominent basement uplifts along its margin and plunging syncline inside the arch. The marginal large-scale uplifts are bounded by outward-dipping faults. The uplift-related strata are identified on the hanging wall block of the bounding faults and within the Haema Arch, which can be divided into pre-, syn-, and post-uplift units. The pre-uplift unit rests on the acoustic basement and shows an upturned stratal pattern near the marginal large-scale uplift. The syn-uplift unit locally occurs on the hanging wall block of the bounding faults along the northern and southern margins. The uplift of the Haema Arch and its coeval fault-controlled subsidence possibly occurred during the late Oligocene. The post-uplift unit initially formed on remnant topographic lows during the early Miocene and subsequently covered the overall area of the Haema Arch and the Gunsan Basin. The late Oligocene uplifting of the Haema Arch can be interpreted as an isostatic response to tectonic unloading by the arch-bounding faults that possibly extend to detachment faults. We suggest that the Gunsan Basin underwent crustal thinning and extensional deformation during the late Oligocene, which accounts for the coeval uplifting and fault-controlled subsidence in the study area.     

楚雄复式盆地演化及形成的动力学机制

楚雄盆地处于中国云南省中部，位于扬子板块西南缘，南西界以红河断裂为界与哀牢山造山带相连，北西界为程海断裂，东边为绿汁江断裂。盆地基底包括结晶基底和褶皱基底双重结构。盆地内发育了中三叠世以后的沉积盖层，西部中三叠世和晚三叠世早、中期为海相沉积，晚期为海陆交互相和陆相沉积；盆地东部为陆相沉积。侏罗—白垩纪整个盆地为巨厚的陆相沉积。楚雄盆地的构造格架分为４个带：（１）哀牢山造山带；（２）褶皱逆冲带；（３）中部沉降带；（４）东部隆起带。盆地形成与演化分为六个阶段：（１）被动大陆边缘沉降阶段；（２）拉张热隆起边缘——裂谷盆地阶段；（３）沟－弧－盆系阶段；（４）残洋－周缘前陆盆地阶段；（５）走滑－拉张盆地阶段；（６）走滑－挤压－改造阶段。楚雄盆地的形成与演化体现了盆地动力学性质转化和复合，在多种动力系统作用下或经过多旋回构造阶段产生了复式盆地     

南海北部新生代盆地断裂系统及构造动力学影响因素

利用地震资料、油气勘探资料分析了南海北部大陆边缘珠江口-琼东南新生代盆地断裂系统的时空差异及动力学成因机制.珠江口-琼东南盆地古近系裂陷构造层以NE向、近EW向基底正断层构成的伸展断裂系统的几何学、运动学沿着盆地走向有明显变化,盆地内部隐伏的区域性和局部的NW向断裂及相关构造变形带构成伸展断裂系统之间的构造变换带.在空间上,区域性的云开、松涛-松南等NW向构造变换带以西为NE-NEE向正断层构成的"非拆离"伸展断层系,以东为NE向正断层、近EW向正断层(走滑正断层)复合而成的拆离伸展断层系.在时间上,古近纪裂陷作用可划分为早(文昌组沉积期)、中(恩平组/崖城组沉积期)、晚(珠海组/陵水组沉积期)3个有明显差异的裂陷期.裂陷早期,盆地西部以平面式正断层控制的简单地堑、半地堑为主,伸展量相对较小,东部则以铲式正断层控制的复式地堑、半地堑为主,伸展量相对大,断层向深部收敛在中地壳韧性层构成拆离的伸展断层系统.裂陷中期,琼东南盆地、珠江口盆地西部断裂具有继承性活动特点,珠江口盆地东部发育NWW-EW向伸展断层,并向深层切割早期浅层拆离断层,形成深层拆离伸展断层系统,而沿着云开构造变换带发育反转构造.裂陷晚期,琼东南盆地、珠江口盆地西部断裂具有活动性减弱特点,琼东南盆地东部发育NWW-EW向伸展断层,形成深层拆离伸展断层系统,而沿着琼中央构造变换带发育反转、走滑构造.珠江口-琼东南盆地不同区段断裂系统及其构造演化的差异性受盆地基底先存构造、地壳及岩石圈结构及伸展量等多方面因素的影响,拆离伸展断层系统与发育NWW向"贯穿"断裂的基底构造薄弱带、现今地壳局部减薄带相关,南海扩展由东而西的迁移诱导北部大陆边缘块体沿着先存NW向深大断裂发生走滑旋转是导致变换构造带两侧差异伸展的动力学原因,应力场及岩石圈热结构变化是引起拆离断层深度变化的重要因素.     

鄂尔多斯盆地基底断裂及其现代活动性

对鄂尔多斯盆地基底断裂特征及其活动性作了总结、归纳与分析。结果表明,鄂尔多斯盆地不仅是一个四周被活动断裂或深大断裂围限的块体,其内部还存在大量规模不等的基底断裂,并具有明显的分区特征。盆地内基底断裂带可分成4组：几乎贯穿整个盆地的华池-米脂-大同北东向断裂带;盆地北部的多条东西向断裂带和中部的定边-绥德、南部的庆阳-富县-宜川等东西向断裂带;中部发育的定边-吴起、乌审旗-榆林北西向断裂带与盆地东西两侧的近南北向巨型断裂带。鄂尔多斯盆地内存在的现代构造地貌以及普遍发育的雁行状、X共轭状节理等现象,是新构造运动的直接表现;盆地内存在的深部流体活动信息、现代地球化学景观特征以及众多的小地震、微地震活动及其与基底构造的密切关系,反映了这些断裂的现代活动性。     

西藏班公湖—怒江构造带尼玛盆地构造性质

雅鲁藏布江洋俯冲及印度-欧亚陆陆碰撞导致了强烈的大陆岩石圈挤压变形与青藏高原的隆升。研究青藏高原内部破碎带构造-沉积演化,对理解相关变形如何向欧亚大陆腹地扩展传递至关重要。班公湖—怒江缝合带内发育一系列白垩纪—新生代陆相沉积盆地,保存了关于该时期高原内部构造-沉积演化的丰富信息。针对该类盆地的构造性质和形成机制有走滑拉分盆地、断陷盆地、前陆盆地3类不同观点。若要检定上述观点,需要开展如下工作:(1)查明盆地基底与充填建造变形特征;(2)结合构造背景探究其演化机制。鉴于此,本文对该带内尼玛盆地开展大比例尺地质填图与构造分析,结合前人成果,对盆地构造背景、构造性质和构造演化进行了探讨。主要取得了如下认识:(1)尼玛盆地基底为班公湖—怒江洋闭合形成的软碰撞缝合带内的变质岩与海相沉积岩。基底断裂为近东西走向,倾向或南或北的逆冲断裂。(2)盆地充填建造为上白垩统—新近系多旋回河湖相沉积。其变形样式主要为轴向近东西延伸的非对称褶皱,局部卷入基底断裂变形。多幕次变形自边缘向盆地中心前展式递进发展。(3)盆地可以划分为盆北掀斜隆起、南部推覆扇状隆起两处主要剥蚀物源区、中部基底断片掀斜隆起一处次要剥蚀物源区,以及北部叠瓦状压陷区与南部对冲压陷区两处主要构造沉积单元,其构造格架可以概括为“三隆夹两坳”。(4)尼玛盆地肇始于班公湖—怒江洋闭合导致的南北向地壳缩短。其后,雅鲁藏布江洋北向俯冲与印度-欧亚碰撞所致南北向挤压,导致盆地基底断裂发生周期性活动,伴有多旋回磨拉石建造与递进变形。简言之,尼玛盆地为软碰撞缝合带之上发育的山间压陷盆地。     

鄂尔多斯盆地中、新生代后期改造

鄂尔多斯盆地周缘和内部在中、新生代都受到后期改造作用,周缘存在挤压逆冲推覆和拉张断陷等不同性质的构造改造作用。在盆地内部,后期改造过程中发育在盖层中的断裂具有很强的规律性,受到了基底断裂的控制。盆地中部东西向断裂带对盆地的构造特征具有分区性,南北构造特征有别,北部地区北东、北西、近东西向断裂均有发育,正断裂、逆断裂和由断裂控制的挠曲构造等有规律发育,在不同方向基底断裂交汇部位的盖层内断裂最发育。南部则主要发育北东方向断层。     

Aspects of the structural evolution of the Lusitanian Basin in Portugal and the shelf and slope area offshore Portugal

The study provides a regional seismic interpretation and mapping of the Mesozoic and Cenozoic succession of the Lusitanian Basin and the shelf and slope area off Portugal. The seismic study is compared with previous studies of the Lusitanian Basin. From the Late Triassic to the Cretaceous the study area experienced four rift phases and intermittent periods of tectonic quiescence. The Triassic rifting was concentrated in the central part of the Lusitanian Basin and in the southernmost part of the study area, both as symmetrical grabens and half-grabens. The evolution of half-grabens was particularly prominent in the south. The Triassic fault-controlled subsidence ceased during the latest Late Triassic and was succeeded by regional subsidence during the early Early Jurassic (Hettangian) when deposition of evaporites took place. A second rift phase was initiated in the Early Jurassic, most likely during the Sinemurian–Pliensbachian. This resulted in minor salt movements along the most prominent faults. The second phase was concentrated to the area south of the Nazare Fault Zone and resulted here in the accumulation of a thick Sinemurian–Callovian succession. Following a major hiatus, probably as a result of the opening of the Central Atlantic, resumed deposition occurred during the Late Jurassic. Evidence for Late Jurassic fault-controlled subsidence is widespread over the whole basin. The pattern of Late Jurassic subsidence appears to change across the Nazare Fault Zone. North of the Nazare Fault, fault-controlled subsidence occurred mainly along NNW–SSE-trending faults and to the south of this fault zone a NNE–SSW fault pattern seems to dominate. The Oxfordian rift phase is testified in onlapping of the Oxfordian succession on salt pillows which formed in association with fault activity. The fourth and final rift phase was in the latest Late Jurassic or earliest Early Cretaceous. The Jurassic extensional tectonism resulted in triggering of salt movement and the development of salt structures along fault zones. However, only salt pillow development can be demonstrated. The extensional tectonics ceased during the Early Cretaceous. During most of the Cretaceous, regional subsidence occurred, resulting in the deposition of a uniform Lower and Upper Cretaceous succession. Marked inversion of former normal faults, particularly along NE–SW-trending faults, and development of salt diapirs occurred during the Middle Miocene, probably followed by tectonic pulses during the Late Miocene to present. The inversion was most prominent in the central and southern parts of the study area. In between these two areas affected by structural inversion, fault-controlled subsidence resulted in the formation of the Cenozoic Lower Tagus Basin. Northwest of the Nazare Fault Zone the effect of the compressional tectonic regime quickly dies out and extensional tectonic environment seems to have prevailed. The Miocene compressional stress was mainly oriented NW–SE shifting to more N–S in the southern part.     

Geodynamic evolution of the Vulcan Sub‐basin,Timor Sea,northwest Australia: A pre‐compression New Guinea analogue?

The Vulcan Sub‐basin lies immediately inboard of the incipient arc‐continent collision in the Timor Sea and comprises part of the Bonaparte Basin system, the northernmost basin on Australia's North West Shelf. Given the high level of preservation of its extensional fabric, the region can provide important analogues for the likely pre‐orogeny architecture of New Guinea, which enables a better understanding of the onset of, and response to, orogenesis. Structural restoration of regional, depth‐converted 2–D seismic lines shows that although the Late Jurassic Swan Graben is significant and contains a thick source‐rock section, the principal phase of crustal extension took place in the Triassic to Middle Jurassic. Within the Vulcan Sub‐basin, the southern Tilted Fault Block Domain records ～10% Triassic to Middle Jurassic extension, whereas <5% upper crustal extension has been measured in the northern Hourglass Domain. Similarly, while Jurassic extension in the Tilted Fault Block Domain is both deep and focused, the Hourglass Domain is expressed as a broad sag to the northeast, indicating a strong underlying basement influence on compartmentalisation. The Vulcan Sub‐basin shows four principal stages of evolution: (i) regional, evenly spaced crustal faulting and subsidence in the Triassic ‐ Middle Jurassic; (ii) focused faulting in the Late Jurassic that created grabens with uplift of the shoulders; (iii) regional subsidence from the Middle Valanginian; and (iv) minor extensional and contractional reactivation in the Mio‐Pliocene. The measured brittle extension is much less than that suggested by modelling of lithospheric subsidence, which suggests long wavelength distribution of strain in the ductile lower crust, with upper crustal extension mainly focused along the continent‐ocean boundary. Along the North West Shelf and on a smaller scale within the Vulcan Sub‐basin per se, the obvious, basement‐involved, rectilinear compartments defined by prominent offsetting of both extensional fault systems and abyssal plains have important implications for the development of the New Guinea orogen. Similar scale compartments are recognised in New Guinea and display different structural styles and hydrocarbon prospectivity. The transfer zones separating the compartments are the sites of the major copper‐gold deposits in New Guinea. Using the Vulcan Sub‐basin ‐ Timor area as an analogue, it can be seen that an arc could originally collide with a promontory, such as what is now Timor, and reactivate the lineaments allowing local extension and mineralisation. In addition, interpretation of the structure of the New Guinea Fold Belt may be aided by considering the effects of compression on the geometry of the Vulcan Sub‐basin and of the similar Carnarvon Basin and adjacent extended and broken Exmouth Plateau.     

渤海湾盆地基岩地质图及其所包含的构造运动信息

利用油气勘探资料编制的渤海湾盆地基岩地质图 ,分析了基岩露头分布及其反映的中、新生代构造运动特征。基岩地质图显示渤海湾盆地基底岩层受印支运动和燕山运动影响发育有一系列近EW向、NNE—NE向的褶皱和逆断层等挤压构造变形。基岩露头展布表明渤海湾盆地西部、北部在侏罗纪之前的剥蚀作用明显强于东部和南部地区。基岩地层形成的区域褶皱轴向及各亚构造层之间的不整合面接触关系反映出在下—中三叠统沉积之后至下—中侏罗统沉积之前的某个“关键时刻”渤海湾地区发生了一次重要的构造变革 ,导致早期的近EW向构造被NNE—NE向构造替代。而从区域应力体制来看 ,下—中侏罗统沉积之后渤海湾地区的区域构造环境发生了重要变化 ,从中生代早期的挤压构造环境变为以裂陷作用为主的构造演化时期     

Oblique convergence during the Cimmerian collision: Evidence from the Triassic Aghdarband Basin,NE Iran

The Lower-Middle Triassic Aghdarband Basin, NE Iran, consists of a strongly deformed arc-related marine succession deposited along the southern margin of Eurasia in a highly mobile tectonic context. This basin is a key-area for the study of the Cimmerian events, as the Triassic units show severe deformations, which occurred short time after the collision of Iran with Eurasia, and were sealed by the Middle Jurassic succession. In this work, we document the structural setting and evolution of this area, based on detailed mesoscopic structural analyses of faults and folds, paleostress reconstruction and revision of the Triassic stratigraphy. The Triassic sequences are deeply involved in a N-verging thrust stack interacting with an important left-lateral transpressional fault zone characterized by strike-slip faults, vertical folds and high angle reverse faults generating intricate positive flowers. Systematic folds asymmetry indicates that they developed in a left-lateral transpressional zone coeval to thrust imbrication to the south, due to a marked strain partitioning.The extent of the transpressional zone shows that important left-lateral movements developed parallel to the belt during the Cimmerian collision, in response to oblique convergence between Iran and Eurasia. Inversion of Triassic syn-sedimentary faults, possibly inherited from Palaeozoic structures of the Kopeh Dagh basement and favouring strain partitioning, is suggested by unconformities, significant differences in the sedimentary successions, repeated olistoliths, scarp-related coarse breccias and rapid tectonic drowning, occurring especially along the northern tectonic boundary of the basin. Paleostress analyses point to a complex stress pattern showing a 45° rotation of the stress field along the left-lateral fault system, related to a complete deformation partitioning in two domains respectively characterized by pure reverse dip-slip and strike-slip motions. The main direction of compression, possibly oriented NE–SW in present days coordinates, favoured the development of large shear zones disrupting the eastern portion of the Cimmerian orogen.     

Tectonics and sedimentation in the Curitiba Basin, south of Brazil

The Curitiba Basin, Paraná, lies parallel to the west side of the Serra do Mar range and is part of a continental rift near the Atlantic coast of southeastern Brazil. It bears unconsolidated and poorly consolidated sediments divided in two formations: the lower Guabirotuba Formation and the overlying Tinguis Formation, both developed over Precambrian basement. Field observations, water well drill cores, and interpretations of satellite images lead to the inference that regional tectonic processes were responsible for the origin of the Basin in the continental rift context and for morphotecatonic evolution through block tilting, dissection, and erosion. The structural framework of the sediments and the basement is characterized by NE–SW-trending normal faults (extensional tectonic D₁ event) reactivated by NE–SW-trending strike–slip and reverse oblique faults (younger transtensional tectonic D_2′ to transpressional tectonic D_2″ event). This tectonic event, which started in the Paleogene and controlled the basin geometry, began as a halfgraben and was later reactivated as a pull-apart basin. D₂ is a neotectonic event that controls the current morphostructures. The Basin is connected to the structural rearrangement of the South American platform, which underwent a generalized extensional or trantensional process and, in late Oligocene, changed to a compressional to transpressional regime.     

新疆西天山吐拉苏火山盆地金矿的构造控矿规律

新疆西天山吐拉苏火山盆地金矿在不同尺度上受不同级别的构造控制。在大地构造尺度上，Ⅰ级控矿构造为与博罗科努丰生代岛弧带平行的NWW向基底断裂带，该断裂带控制与石炭纪火山岩有关的金矿带的展布，在区域尺度上，Ⅱ级控矿构造为NW向走滑断裂和NE向张笥断裂，控制金矿床的分布。在矿床尺度上，Ⅲ级控矿构造为陡倾的近SN向张性断裂和与破火山口有关的环状断裂，控制金矿体的定位和产状。     

Jurassic extension and Cenozoic inversion tectonics in the Asturian Basin,NW Iberian Peninsula: 3D structural model and kinematic evolution

We constructed a geological map, a 3D model and cross-sections, carried out a structural analysis, determined the stress fields and tectonic transport vectors, restored a cross section and performed a subsidence analysis to unravel the kinematic evolution of the NE emerged portion of the Asturian Basin (NW Iberian Peninsula), where Jurassic rocks crop out. The major folds run NW-SE, normal faults exhibit three dominant orientations: NW-SE, NE-SW and E-W, and thrusts display E-W strikes. After Upper Triassic-Lower Jurassic thermal subsidence, Middle Jurassic doming occurred, accompanied by normal faulting, high heat flow and basin uplift, followed by Upper Jurassic high-rate basin subsidence. Another extensional event, possibly during Late Jurassic-Early Cretaceous, caused an increment in the normal faults displacement. A contractional event, probably of Cenozoic age, led to selective and irregularly distributed buttressing and fault reactivation as reverse or strike-slip faults, and folding and/or offset of some previous faults by new generation folds and thrusts. The Middle Jurassic event could be a precursor of the Bay of Biscay and North Atlantic opening that occurred from Late Jurassic to Early Cretaceous, whereas the Cenozoic event would be responsible for the Pyrenean and Cantabrian ranges and the partial closure of the Bay of Biscay.     

中阿拉伯盆地油气分布规律和主控因素研究

中阿拉伯盆地是中东油气区油气资源最为富集的盆地。本文以该盆地油气田的最新资料为基础,结合盆地构造-沉积演化过程,应用石油地质综合研究方法,探讨该盆地油气的时空分布特征及主控因素。中阿拉伯盆地内发育3个主要含油气系统:下志留统含油气系统、侏罗系复合含油气系统和白垩系复合含油气系统。中阿拉伯盆地油气的层系分布表现为"下气上油",上二叠统—下三叠统储集层富集了盆地内78.9%的天然气可采储量和83.7%的凝析油可采储量,而上侏罗统—下白垩统则富集了盆地内81.9%的石油可采储量。区域上,中阿拉伯盆地的石油储量主要聚集于西海湾坳陷、迪布蒂巴赫(Dibdibah)坳陷、盖瓦尔(Ghawar)凸起和安纳拉(An N`ala)凸起,天然气和凝析油则在卡塔尔凸起更为富集。中阿拉伯盆地的油气分布主要受3个因素控制:优质区域盖层控制了油气的层系分布,主力烃源岩展布和优势运移路径控制了油气的区域分布,基底断裂和盐运动构成的圈闭控制了油气藏的形成与富集。     

Numerical modeling of Late Miocene tectonic inversion in the Xihu Sag,East China Sea Shelf Basin,China

The East China Sea Shelf Basin is an important oil- and gas-bearing basin in the West Pacific continental margin. This region was affected by subduction of the Pacific Plate and the Philippine Plate in Cenozoic and experienced multi-stage tectonic inversions. This paper presents results from a numerical simulation by finite element method to the Xihu Sag in the East China Sea Shelf Basin and neighboring areas in an attempt to evaluate the WNW-directed compression on the sag during Late Miocene. Based on comprehensive structural analysis of a large number of seismic profiles, we determine the structural geometry of the sag, including the basement of the basin, the sedimentary cover, and 29 major faults in the Xihu Sag. Simulation results show that under continuous WNW-directed compression, tectonic inversion occurred firstly in the Longjing and Yuquan tectonic zones in the sag. Based on quantitative analysis of vertical displacement field of the Xihu Sag and peripheral areas and its stress intensity evolution, we identify a compressional regime in the Longjing Anticline Zone with a gradually propagated uplifting from south to north; whereas the propagation of uplifting in the Yuquan Anticline Zone is from north to south. The inversion intensity decreases from north to south. The formation of the tectonic inversion zone in the Xihu Sag is not only correlated to the direction of compression and fault patterns in the basin, but also closely related to the spatial configuration of fault surfaces of the Xihu–Jilong Fault in the Xihu Sag.     

鄂尔多斯盆地中生界油气成藏与构造运动的关系

鄂尔多斯盆地是中国著名的大型中生代含油气盆地,上三叠统延长组和侏罗系延安组为盆地主要含油层系,该含油层系经历了印支、燕山和喜山三期大的构造运动。通过中、新生代不同地质历史时期应力场分析以及构造热事件研究,结合裂缝性质、裂缝方位及裂缝中包裹体特征等,讨论了中生界油气成藏与构造运动的关系。研究认为盆地主要发育E—W向、NNE向和NE向三组区域性裂缝。其中,弱充填的NE向剪裂缝为印支期S—N向挤压环境下形成的剪裂缝,或基底断裂形成的诱导张裂缝;近E—W向展布的弱充填裂缝为燕山期NW—SE挤压环境下形成的剪切裂缝;强烈充填的NNE向张裂缝形成于喜山期NNW—SSE拉张环境。盆地中、新生代地层所经历的每一期构造运动都对盆内油气的运移和聚集起控制作用。印支运动使得盆地沉积了中生界最为重要的一套烃源岩;燕山运动产生的构造热事件使烃源岩达到了生排烃高峰期,使得油气成藏大多定型于燕山期;喜山运动使油气进行大规模的运移和调整,从而使中生界上部油气的分布与基底断裂带走向相吻合。中、新生代这三期构造运动对鄂尔多斯盆地发展和油气成藏产生了重要影响。     

卡拉库姆盆地晚二叠世-三叠纪的构造属性讨论

卡拉库姆盆地位于中亚地区图兰地台南部,北西走向,是中亚地区最重要的含油气盆地之一。对于盆地晚二叠世-三叠纪的构造属性一直都存在着很多争论,我们根据钻井、地球物理及露头资料,认为卡拉库姆盆地是以增生杂岩为基底形成的一个沉积盆地,晚二叠世-三叠纪具有弧后裂谷的性质。卡拉库姆盆地前侏罗纪的构造演化分为4个阶段:1)石炭纪之前古特提斯洋壳开始俯冲增生; 2)石炭纪-早二叠世形成丝路弧; 3)晚二叠世-三叠纪马什哈德-北帕米尔弧形成,卡拉库姆盆地处于弧后拉张的位置; 4)晚三叠世末伊朗等地块与欧亚大陆碰撞,卡拉库姆盆地进入短暂的周缘前陆盆地阶段。其晚二叠世-三叠纪的沉积中心在北阿姆河坳陷,木尔加布坳陷和科佩特山前坳陷,沉积环境主要为陆相,三叠纪发生海侵,部分地区接受海相沉积。岩石类型主要为陆源碎屑岩、火山岩及少量灰岩。     

Tectonic framework of Tiburon Basin,Gulf of California,from seismic reflection evidence

Tiburon Basin is characterized by a thick sedimentary fill that records the evolution of one of the rift segments of the East Pacific Rise. Its structure corresponds to an echelon pull-apart basin bounded by two dextral-oblique faults. Unlike basins in the southern Gulf of California that are underlain by oceanic crust, rift basins in the northern Gulf of California contain sedimentary thickness (up to 6 km) that masks the structure of the crust. To study the architecture of the Tiburon Basin, two-dimensional, multichannel seismic reflection data collected by Petróleos Mexicanos (PEMEX) in the early 1980s were used. The data base is a grid of lines, 5–20 km apart, with 6 s of record in 48 channels. Additional seismic data of the Ulloa 99 project were also interpreted. Our results indicate that the general structural pattern of the Tiburon Basin is controlled by two dextral-oblique faults: De Mar and Tiburon. De Mar lies to the east and ends in elevated basement transferring the stress to the Desemboque fault. The latter borders the incoming basement from the Sonora and Tiburon faults to the west, ending to the north in an antiform. Four structural domains are recognized: (1) the northern Tiburon domain is a high basement that divides the Delfin Basin to the northeast and exhibits extensional folds with their axes parallel to the basement and its flanks; (2) the Libertad domain is a sheared basement high along the margin of Sonora and forms the right step of the Tepoca Basin to the north; (3) the Tiburon central domain defines a broad sag cut by a dense NE-striking pattern of normal faults with opposed dips in the depocentre and abruptly ends to the west against the Tiburon fault; and (4) the southern Tiburon domain forms a basement ramp offshore Isla Tiburon and is controlled by a pattern of NNE-striking normal faults on the south that likely connect at an oblique angle (?60°) to the De Mar fault. We propose a rhombochasm basin model with more than 6 s of sedimentary record in the depocentre, in which the basement is not recorded. The NW-trending faults in the Libertad domain possibly continue towards the Sonora coastal plain. The principal NW-trending dextral faults and the secondary NNE-striking pattern of normal faults cut the shallow strata of this domain.     

银根-额济纳旗盆地西缘的中-新生代伸展构造

银根-额济纳旗盆地简称银额盆地,是中亚造山带南缘的一个中-新生代沉积盆地。最近的野外地质调查,在其西缘发现早侏罗世和第四纪晚期的伸展构造。早侏罗世的伸展构造为一系列走向NNW-SSE 的正断层,是下侏罗统的同沉积断层。这组正断层与银额盆地内NNE-SSW 走向的正断层组合成共轭断裂系统,指示古构造应力场的最大主拉张应力方向为近E-W。它们是中亚造山带（南缘）造山后应力伸展阶段的构造变形。第四纪晚期的伸展构造是由两条倾向相向的正断层组合成的地堑构造,走向进E-W,可能代表了喜马拉雅碰撞造山远程效应脉动式演化过程的一个构造间歇期。