Microtectonic and geochemical characterization of thrusting in a foreland basin: Example of the South-Pyrenean orogenic wedge (Spain)

In orogenic systems, thrust faults play a major role in stacking different tectonic units and may act as conduits for the expulsion of large amounts of fluid of different origins (metamorphic, diagenetic, meteoric). This study focuses on the Monte Perdido thrust unit emplaced in the Paleogene Jaca thrust-sheet-top basin, in the SW-central Pyrenees. We aim to decipher the mechanisms and P-T conditions of deformation in fault zones and characterize the related fluid involvement, through combined microstructural, geochemical and microthermometry analyses. Two thrust faults cutting platform limestones, marls and siliciclastic turbidites of the lower part of the basin-fill (Paleocene–lower Eocene) have been studied. The fault zones are characterized by metre-thick shear zones with highly deformed, foliated clay-rich sediments. Foliation is underlined by preferentially oriented phyllosilicates. Several generations of shear and extension calcite, quartz and chlorite-bearing veins attest to fluid-rock interactions during a multi-stage deformation. Microstructural observations and stable isotope analyses on calcite from veins and host sediments suggest that deformation was aseismic and dominated by diffusive mass transfer from pressure solution sites along cleavage and stylolites to the precipitation sites in veins, with mineralizing fluids in equilibrium with the host sediments. Our results suggest an essentially closed hydrologic system, and imply the absence of significant fluid flow along the studied fault zones. Microthermometric study on fluid inclusions present in calcite and quartz veins, and calcite-quartz oxygen isotopic fractionation determined for the first generation shear veins, allow a geothermal gradient of 34 °C/km to be estimated. Analytical results demonstrate an evolution of the fault zones in three stages. The first stage was related to the emplacement of the Monte Perdido thrust unit during the middle Eocene at a temperature of ～208 °C and a burial depth of ～5.7 km. The second stage corresponds to a fault reactivation at a temperature of ～240 °C and a burial depth of ～6.5 km. The latter deformation may have been related to folding of the Monte Perdido thrust unit during the emplacement of the underlying Gavarnie thrust unit during the late Eocene–early Oligocene, with deeper burial resulting from aggradation of the thrust-sheet-top basin-fill. The last event corresponds to the formation of a dilatant vein system likely related to the exhumation of the massif.     

从弧后盆地到前陆盆地——北祁连造山带奥陶纪—泥盆纪的沉积盆地与构造演化

北祁连加里东期造山带是在新元古代Rodinia联合大陆(Pangea-850)基础上裂解,经由寒武纪裂谷盆地、奥陶纪初期成熟洋盆、奥陶纪中晚期北祁连活动大陆边缘、志留纪—早、中泥盆世碰撞造山而形成的。奥陶纪中、晚期,北祁连、走廊地区中、上奥陶统发育洋壳-岛弧-弧后火山岩,形成典型的沟-弧-盆体系的沉积。志留纪—早、中泥盆世是北祁连-走廊沉积盆地的转换时期。除天祝、古浪、景泰及肃南等局部地区发育下志留统钙碱性系列火山岩以外,全区志留系均以碎屑岩沉积为主。志留系底部多见一套砾岩层。下—中志留统为典型复理石相的浊流沉积。上志留统变为滨浅海相磨拉石沉积。早、中泥盆世雪山群为典型的陆相粗碎屑磨拉石沉积。从空间分布上看,志留系—泥盆系在走廊—北祁连地区也有自北向南厚度加大、粒度变粗的特征,古流以由南向北、来自造山带的古流为特征。北祁连-河西走廊奥陶纪弧后盆地火山岩—志留系复理石-海相磨拉石—中、下泥盆统陆相磨拉石的充填序列以及空间分布特点,反映为典型的弧后盆地向前陆盆地转化的沉积序列。     

从弧后盆地到前陆盆地--北祁连造山带奥陶纪-泥盆纪的沉积盆地与构造演化

北祁连加里东期造山带是在新元古代Rodinia联合大陆(Pangea-850)基础上裂解,经由寒武纪裂谷盆地、奥陶纪初期成熟洋盆、奥陶纪中晚期北祁连活动大陆边缘、志留纪-早、中泥盆世碰撞造山而形成的.奥陶纪中、晚期,北祁连、走廊地区中、上奥陶统发育洋壳-岛弧-弧后火山岩,形成典型的沟-弧-盆体系的沉积.志留纪-早、中泥盆世是北祁连-走廊沉积盆地的转换时期.除天祝、古浪、景泰及肃南等局部地区发育下志留统钙碱性系列火山岩以外,全区志留系均以碎屑岩沉积为主.志留系底部多见一套砾岩层.下-中志留统为典型复理石相的浊流沉积.上志留统变为滨浅海相磨拉石沉积.早、中泥盆世雪山群为典型的陆相粗碎屑磨拉石沉积.从空间分布上看,志留系-泥盆系在走廊-北祁连地区也有自北向南厚度加大、粒度变粗的特征,古流以由南向北、来自造山带的古流为特征.北祁连-河西走廊奥陶纪弧后盆地火山岩-志留系复理石-海相磨拉石-中、下泥盆统陆相磨拉石的充填序列以及空间分布特点,反映为典型的弧后盆地向前陆盆地转化的沉积序列.     

印支期龙门山造山楔推进作用与前陆型礁滩迁移过程研究

马鞍塘期龙门山前陆盆地是印支期造山楔加载于扬子地台西缘而形成的挠曲前陆盆地。根据地表露头、钻孔剖面和地震反射剖面资料,本文通过分析前陆盆地早期前陆缓坡型鲕粒滩-硅质海绵礁组合在时间和空间上的迁移规律,标定了卡尼期龙门山造山楔的推进速率。结果表明:卡尼期马鞍塘组是分布于底部不整合面之上的第一套地层单元,在垂向上前陆型鲕粒滩-硅质海绵礁组合显示为鲕粒灰岩滩-生物碎屑滩-硅质海绵礁灰岩-泥页岩的向上变细的沉积序列,记录了前缘隆起边缘碳酸盐缓坡和海绵礁的构建和淹没过程,反映了在相对海平面的持续上升中鲕粒滩-硅质海绵礁被淹没致死的过程。在横向上,盆地结构显示为西厚东薄,并向西倾斜的不对称盆地,由西向东依次分布了深水盆地、碳酸盐缓坡和海绵礁和浅水滨岸带等沉积物类型,显示了从龙门山造山楔向前陆一侧具有泥页岩向鲕粒滩-硅质海绵礁的变化特征。其中鲕粒滩-硅质海绵礁丘组合发育于15～30m深度的前陆同斜缓坡上,呈面向西的条带状展布,其走向线与龙门山冲断带的走向大致平行。并可将其划分为7个鲕粒滩-硅质海绵礁相带,表明卡尼期硅质海绵礁丘和滩沿底部不整合面向南东方向的前陆缓坡超覆,其超覆线和相带的走向与龙门山冲断带的走向平行,显示了7条硅质海绵礁丘和滩是随着相对海平上升过程而向南东方向的前陆缓坡超覆过程中逐次形成的。卡尼期硅质海绵礁迁移速率为18mm·yr-1,其与龙门山造山楔推进速率(15mm·yr-1)基本一致,表明印支期龙门山逆冲楔推进速率与前陆鲕粒滩-硅质海绵礁丘迁移速率具有明显的耦合关系。据此,本次提出了龙门山前陆盆地早期前陆型碳酸盐缓坡和硅质海绵礁的迁移模式,其形成的过程为:龙门山造山楔于卡尼期初始构造负载于扬子板块西缘,导致了前陆地区的挠曲沉降,形成了前陆盆地,驱动了相对海平面的持续上升,前陆盆地处于欠补偿状态,当相对海平面上升速率与硅质海绵礁生长速率相同时,在15～30m深度的前陆同斜缓坡上发育了鲕粒滩-硅质海绵礁丘组合,随着龙门山造山楔不断地的向前陆地区推进,前陆盆地内相对海平面持续上升,逐次在前陆缓坡上15～30m深度的的位置开启了新的硅质海绵礁群的生长窗,形成了本区卡尼期7条带状展布的鲕粒滩-硅质海绵礁丘组合。因此,硅质海绵礁的淹没过程和迁移过程是龙门山造山楔向扬子克拉通推进过程的沉积响应,显示了在卡尼期-诺利期松潘-甘孜残留洋盆的迅速闭合和逆冲楔构造负载向扬子板块推进的动力学过程。     

岩石圈中热压系数的计算

中国中西部地区发育众多前陆冲断带,它们具有构造变形复杂、油气潜力大和有别于经典前陆盆地的沉积和油气地质特征,但其成因过程和动力学并不清楚。文中利用中西部盆地区的地温、岩石热物性参数和地热学模拟技术,分析该区岩石圈热状态和流变学特征,进一步结合其他地质、地球物理资料,揭示盆地区的深部构造特征和岩石圈性质。研究表明,中西部各主要盆地的岩石圈具有厚度大、强度高、地温低等热-流变学特征,表现为刚硬块体;而其周缘和造山带区却表现为温度高、强度低和厚度小等特征,是构造变形的易发区。在此基础上讨论了岩石圈性质和变形过程等深部构造对前陆盆地成因演化的控制作用,进而初步归纳这类陆内再生前陆盆地的成因演化机制:发育于小型克拉通块体的边缘,其就位受控于岩石圈热-流变学非均质性和构造继承性,其动力来源是新生代印度-欧亚大陆碰撞及其持续的挤压作用。上述研究为探讨中国中西部地区的前陆盆地成因机制提供了深部资料和岩石圈热-流变学约束。     

薄弱的造山带岩石圈地幔影响地幔柱触发的超大陆裂解模式

超大陆的裂解是全球构造演化的基本过程,同时也是超大陆旋回的重要组成部分。目前对于超大陆裂解的研究主要集中在是否是由于俯冲或是地幔柱作用而导致超大陆的裂解,但对于其他关键因素,如对控制大陆裂解轨迹的非刚性特性并没有得到充分研究。最近,北京大学的Zhang Z及其合作者基于具有完整重建历史的潘吉亚超大陆的裂解,根据全球的造山带位置和几何特征,通过三维地球动力学模拟以及地质记录对比解译了超大陆裂解的控制因素和过程。     

龙门山前陆盆地底部不整合面: 被动大陆边缘到前陆盆地的转换

晚三叠世龙门山前陆盆地是在扬子板块西缘被动大陆边缘的基础上由印支造山运动而形成的,盆地中地层充填厚度巨大,包括晚三叠世卡尼期至瑞提期的马鞍塘组、小塘子组和须家河组,持续时间达20Myr,显示为1个以不整合面为界的构造层序。位于晚三叠世龙门山前陆盆地构造层序与下伏古生代-中三叠世被动大陆边缘构造层序之间的不整合面属于龙门山前陆盆地的底部不整合面,标志了扬子板块西缘从被动大陆边缘盆地到前陆盆地的转换。该底部不整合面位于晚三叠世马鞍塘组与中三叠世雷口坡组之间,显示为平行不整合面或角度不整合面,在接触面上发育冲蚀坑、古喀斯特溶沟、溶洞、溶岩角砾、古风化壳的褐铁矿、黏土层及石英、燧石细砾岩等底砾岩。该不整合面向南东方向不断地切削下伏地层,且均发育岩溶风化面,上覆的晚三叠世地层沿不整合面向南东超覆,显示了从整合面到不整合面的变化过程,并随着逆冲楔的推进向南东方向迁移,其超覆线、侵蚀带和相带的走向线与龙门山冲断带的走向大致平行。底部不整合面显示为典型的前陆挠曲不整合面,标志着龙门山前陆盆地的形成和扬子板块西缘挠曲下降和淹没过程,底部为古喀斯特作用面,下部为碳酸盐缓坡和海绵礁建造,上部为进积过程中形成的三角洲沉积物,具有向上变粗的垂向结构,表明底部不整合面和前缘隆起的抬升是扬子板块西缘构造负载的挠曲变形的产物,显示了在卡尼期松潘-甘孜残留洋盆的迅速闭合和逆冲构造负载向扬子板块的推进过程。本次在对晚三叠世龙门山前陆盆地底部不整合面的风化壳、残留厚度、地层缺失、剥蚀厚度、地层超覆等研究的基础上,计算了底部不整合面迁移速率、前缘隆起迁移速率、地层上超速率和前缘隆起的剥蚀速率,并与逆冲楔推进速率进行了对比,结果表明,底部不整合面迁移速率、前缘隆起的迁移速率、地层上超速率均介于3~18mm·a^-1之间,其与逆冲楔推进速率(5~15mm·a^-1)相似,因此,可用底部不整合面迁移速率、前缘隆起的迁移速率和地层上超速率代表逆冲楔推进速率。但是前缘隆起的剥蚀速率很小,介于0.02~0.08mm·a^-1之间,仅为逆冲楔推进速率的1/100。     

前陆盆地构造-热演化:以龙门山前陆盆地为例

前陆盆地油气资源丰富但构造变形十分复杂,使得前陆盆地构造-热演化模拟面临挑战。前陆盆地演化过程中构造与热的耦合体现在多个层面:岩石圈热演化对岩石圈强度时空分布及其挠曲的影响;逆冲推覆作用的浅部温度效应;快速沉积作用对盆地温度场的影响等。首先,前陆盆地形成时的岩石圈热背景及其造成的岩石圈强度空间变化对盆地后期的演化具有重要影响。同时早期热事件的热扰动也会叠加在前陆盆地的构造-热演化过程中,并不断衰减,影响岩石圈的流变结构,从而带来一系列的影响。热与构造演化相耦合在前陆盆地定量模拟中非常重要。其次,还需特别关注岩石圈深部过程与近地表构造过程的耦合。造山带逆冲推覆、抬升和剥蚀是与前陆盆地形成相关的重要构造活动,这种运动引起的热对流对造山带的热结构、前陆逆冲带以及前渊地区的温度场的分布有着重要影响。最后,前陆盆地形成演化过程中的快速沉积作用对盆地温度场和地表热流产生强烈的压制作用,对前陆盆地浅部热演化的影响不容忽视。因此,在浅部热演化(包括造山带逆冲推覆、快速沉积压实等)与盆地下伏岩石圈挠曲、深部热演化的联合作用下,使得前陆盆地构造-热演化颇为复杂,二者的耦合使得前陆盆地构造-热演化模拟颇具挑战。     

若尔盖-松潘前陆盆地的沉积与构造特点

若尔盖-松潘盆地中、上三叠统沉积剖面研究表明以陆相沉积为主,只在东北部青山峪有浅海相碳酸盐岩沉积.盆地北部出现河流、浅湖相沉积,中部以浅湖相沉积为主,局部出现深湖相沉积,南部主要为深湖相沉积.中、上三叠统地层的变形构造以冲褶席（duplex）构造为特点,表现出从北向南应变强度减弱.深部构造反映了盆地位于扬子板块大陆壳基底之上,叠覆在扬子板块北缘的前陆褶皱冲断带上.大地构造位置、沉积相与构造特点,共同说明若尔盖-松潘盆地是三叠纪碰撞造山作用时期扬子板块北部北缘的前陆盆地.     

雅鲁藏布江周缘前陆盆地物源分析及构造演化

本文通过雅鲁藏布江缝合带南侧江孜和岗巴地区晚白垩世-古近纪沉积地层的碎屑岩岩石学、地球化学和铬尖晶石电子探针分析,揭示了碰撞前后沉积盆地的物源区变化,提供了盆地和造山带早期的演化历史.江孜地区上白垩统宗卓组属于弧-陆或陆-陆碰撞背景下的海沟沉积.日朗砾岩中的岩屑质长石砂岩地球化学特征反映有大洋岛弧物质的注入,物源区为大洋岛弧或增生楔.上古新统-下始新统甲查拉组长石质岩屑砂岩反映了冈底斯岛弧和再循环造山带物源区特征,是陆-陆碰撞背景下形成的周缘前陆盆地的前渊沉积.岗巴地区古新统基堵拉组石英砂岩表现为印度大陆内部物源区特征,而始新统遮普惹组岩屑砂岩为再循环造山带和冈底斯岛弧物源区.沉积特征和物源区综合研究表明,雅鲁藏布江周缘前陆盆地在古新世期间开始发育,它指示了印度与欧亚板块的初始碰撞时间.     

A metamorphic perspective on foreland flexure during intraplate orogeny: evidence for the involvement of weak lithosphere

Constraining depth–temperature conditions of syn‐orogenic burial metamorphism of syn‐orogenic sediments in a foreland basin provides an innovative way to investigate the thermomechanical state of the lithosphere. In central Australia, major intraplate deformation resulted in 10 km of syn‐orogenic sedimentation in a basin approximately 70 km wide. The deep level of burial in the foreland of the intraplate orogen requires the involvement of weak lithosphere with an elastic thickness of ≤20 km. The profound flexural response of the foreland region indicates that major intraplate deformation in central Australia was localised into a region of dramatically weakened lithosphere.     

Uplift and late orogenic deformation of the Central European Variscan belt as revealed by sediment provenance and structural record in the Carboniferous foreland basin of western Poland

The Carboniferous foreland basin of western Poland contains a coherent succession of late Viséan through Westphalian turbidites derived from a uniform group of sources located within a continental magmatic arc. Detrital zircon geochronology indicates that two main crustal components were present in the source area of Namurian A sediments. They represent Late Devonian and Early Carboniferous ages, respectively. The detritus from Westphalian D beds is much more diversified and contains admixture of Late Carboniferous zircons suggesting rapid unroofing of Variscan igneous intrusions in the hinterland between Namurian A and Westphalian D times. Tectonic repetitions of tens of metres thick fault-bounded stratigraphic intervals, recorded in several wells, provide evidence for compressional regime that occurred in the SW part of the Carboniferous basin not earlier than during the Westphalian C and produced NW–SE trending folds, concordant with the structural grain of the adjacent, NE part of the Bohemian Massif.     

The elastic properties of the lithosphere beneath Scotian basin

To assess the possibility that the North Atlantic Ocean may subduct at Scotian basin east of Canada, we investigate the present compensation state of this deep basin. A Fourier domain analysis of the bathymetry, depth to basement and observed gravity anomalies over the oceanic area east of Nova Scotia indicates that the basin is not isostatically compensated. Moreover, the analysis emphasizes that in addition to the sediments, density perturbations exist beneath the basin. The load produced by the sediments and these density perturbations must have been supported by the lithosphere. We simulate the flexure of the lithosphere under this load by that of a thin elastic plate overlying an inviscid interior. It is shown that a plate with a uniform rigidity does not adequately represent the lithosphere beneath the basin as well as the oceanic lithosphere far from the basin, rather the rigidity of the lithosphere directly beneath the basin is about one to two orders of magnitude smaller than elsewhere. We relate this weakening to the thermal blanketing effects of the thick sediments and the fact that the lithosphere has a temperature-dependent rheology. We suggest that this weak zone would have a controlling effect on the reactivation of normal faults at the hinge zone of the basin, that were formed during the break-up of Africa and North America and were locked in the early stages after the break-up. The weak zone would facilitate reactivation of the faults if tensional stresses were produced by possible reorientation of the spreading direction of the North Atlantic Ocean in the future. The reactivation of the faults would create a free boundary condition at the hinge zone, allowing further bending of the lithosphere beneath the basin and juxtaposition of this lithosphere to the mantle beneath the continent. This may provide a favorable situation for initiation of slow subduction due to subsequent compressional forces.     

前陆盆地挠曲沉降和沉积过程3D模型研究

前陆盆地是在造山带负荷作用下岩石圈发生挠曲沉降而形成的,并且被主要从造山带搬运的沉积物所充填。为了更好地理解和认识前陆盆地的形成演化机制,特别是受控于周缘多个造山带活动所形成的前陆盆地的演化机制,本文通过建立前陆盆地挠曲沉降与沉积过程的3-D模型,模拟展示了造山带逆冲推覆作用、岩石圈挠曲沉降响应及在山盆体系中由于动力地形变化而导致的河流体系的发育变化及其产生的剥蚀和沉积过程。模型的建立和实验完整体现了逆冲推覆、弹性挠曲沉降和沉积物搬运这三者之间的耦合机制,为全面深入研究前陆盆地动力学提供了理论依据和方法。     

The trinity of depositional phase of foreland basins: An examplefrom the western Taiwan foreland basin

Due to oblique arc-continent collision, the west-ern Taiwan foreland basin has evolved into three dis-tinct subbasins: an over-filled basin proximal to the Taiwan orogen, mainly distributed in the Western Foothhils and Coastal Plain provinces, a filled basin occupying the shallow Taiwan Strait continental shelf west of the Taiwan orogen and an under-filled basin distal to the Taiwan orogen in the deep marine Kaop-ing Slope offshore southwest Taiwan, respectively. The over-filled depositional phase is dominated by fluvial environments across the structurally controlled piggy-back basins. The filled depositional phase in the Taiwan Strait is characterized by shallow marine en-vironments and is filled by Pliocene-Quaternary sedi-ments up to 4,000 m thick derived from the Taiwan orogen with an asymmetrical and wedge-shaped cross section. The under-filled depositional phase is charac-teristic of deep marine environments in the wedge-top basins accompanied by active structures of thrust faults and mud diapers.     

Paleozoic orogenic gold deposits in the eastern Central Andes and its foreland,South America

In the eastern Central Andes and its foreland (6°–34°S), abundant quartz veins emplaced along brittle–ductile deformation zones in Ordovician to Carboniferous granites and gneisses and in saddle-reefs in lower Paleozoic turbidites represent a coherent group of middle to late Paleozoic structurally hosted gold deposits that are part of three major Au (±Sb±W) metallogenic belts. These belts, extending from northern Peru to central Argentina along the Eastern Andean Cordillera and further south in the Sierras Pampeanas, include historical districts and mines such as Pataz–Parcoy, Ananea, Santo Domingo, Yani–Aucapata, Amayapampa, Sierra de la Rinconada and Sierras de Córdoba. On the basis of the available isotopic ages, two broad mineralization epochs have been identified, with Devonian ages in the Sierras Pampeanas Au belt (26° to 33°30′S), and Carboniferous ages for the Pataz–Marañón Valley Au-belt in northern Peru (6°50′ to 8°50′S). The absolute timing of the southeastern Peruvian, Bolivian and northwestern Argentinian turbidite-hosted lodes, which form the Au–Sb belt of the southern Eastern Andean Cordillera (12° to 26°S), is poorly constrained. Field relationships suggest overlap of gold veining with Carboniferous deformation events. The northernmost belt, which includes the Pataz province, is over 160-km-long and consists of sulfide-rich quartz veins hosted by brittle–ductile shear zones that have affected Carboniferous granitic intrusions. Gold mineralization, at least in the Pataz province, occurred a few million years after the emplacement of the 329 Ma host pluton and an episode of molassic basin formation, during a period of rapid uplift of the host units. The two southern belts are associated with syn- to post-collisional settings, resulting from the accretion of terranes on the proto-Andean margin of South America. The Au–Sb belt of the southern Eastern Andean Cordillera presumably formed in the final stages of the collision of the Arequipa–Antofalla terrane and the Sierras Pampeanas Au belt is considered concurrent with the late transpressional tectonics associated with the accretion of the Chilenia terrane.The three Devono–Carboniferous Andean belts are the South American segments of the trans-global orogenic gold provinces that were formed from Late Ordovician to Middle Permian in accretionary or collisional belts that circumscribed the Gondwana craton and the paleo-Tethys continental masses. A paleogeographic map of the Gondwana supercontinent in its Middle Cambrian configuration appears as a powerful tool for predicting the location of the majority of the Paleozoic orogenic gold provinces in the world, as they develop within mobile belts along its border. The three South American belts are sited in the metallogenic continuation of the Paleozoic terranes that host the giant eastern Australian goldfields, such as Bendigo–Ballarat and Charters Towers, with which they share many features. When compared to deposits in the French Massif Central, direct counterparts of the Andean deposits such as Pataz and Ananea–Yani are respectively the Saint Yrieix district and the Salsigne deposit. Considering the ubiquity of the Au (±Sb±W) vein-type deposits in the Eastern Cordillera and Sierras Pampeanas, and the relatively little attention devoted to them, the Devonian and Carboniferous orogenic gold deposits in the eastern section of the Central Andes constitute an attractive target for mineral exploration.     

楚雄中生代前陆盆地的构造沉降史研究

云南楚雄盆地位于扬子陆块的西南边缘,为一典型的中生代周缘前陆盆地。盆地演化阶段明显,晚三叠世为前陆早期复理石沉积,侏罗纪则为前陆晚期磨拉石沉积。对盆地构造沉降史研究后笔者认为:①晚三叠世复理石沉积盆地构造沉降幅度巨大,沉降与沉积中心位于盆地最西部,紧邻古哀牢山造山带,沉积体呈楔形展布;②侏罗纪磨拉石沉积盆地构造沉降和沉积中心以及前缘隆起向内陆方向迁移明显;③中生代构造快速沉降的沉积体的楔形展布表明盆地具有前陆岩石圈挠曲成因特征;④盆地的高沉积速率受构造和超补偿沉积作用的共同控制。     

Sedimentology and foreland basin paleogeography during Taiwan arc continent collision

The Western foreland basin in Taiwan originated through the oblique collision between the Luzon volcanic arc and the Asian passive margin. Crustal flexure adjacent to the growing orogenic load created a subsiding foreland basin. The sedimentary record reveals progressively changing sedimentary environments influenced by the orogen approaching from the East. Based on sedimentary facies distribution at five key stratigraphic horizons, paleogeographic maps were constructed. The maps highlight the complicated basin-wide dynamics of sediment dispersal within an evolving foreland basin.The basin physiography changed very little from the middle Miocene (∼12.5 Ma) to the late Pliocene (∼3 Ma). The transition from a passive margin to foreland basin setting in the late Pliocene (∼3 Ma), during deposition of the mud-dominated Chinshui Shale, is dominantly marked by a deepening and widening of the main depositional basin. These finer grained Taiwan derived sediments clearly indicate increased subsidence, though water depths remain relatively shallow, and sedimentation associated with the approach of the growing orogen to the East.In the late Pleistocene as the shallow marine wedge ahead of the growing orogen propagated southward, the proximal parts of the basin evolved into a wedge-top setting introducing deformation and sedimentation in the distal basin. Despite high Pleistocene to modern erosion/sedimentation rates, shallow marine facies persist, as the basin remains open to the South and longitudinal transport is sufficient to prevent it from becoming overfilled or even fully terrestrial.Our paleoenvironmental and paleogeographical reconstructions constrain southward propagation rates in the range of 5–20 km/Myr from 2 Ma to 0.5 Ma, and 106–120 km/Myr between late Pleistocene and present (0.5–0 Ma). The initial rates are not synchronous with the migration of the sediment depocenters highlighting the complexity of sediment distribution and accumulation in evolving foreland basins.     

英吉苏凹陷中—新生代构造特征及成因机制

英吉苏中新生代凹陷是在古生代斜冲推覆构造背景之上发育起来的背驮式前陆盆地。盆地的沉积作用和变形作用严格受基底参与的斜冲断层的控制。中新生代构造由北向南可划分7个带：北部斜坡带;群克一新开屏背斜带;英北向斜带;阿拉于背斜带;英南向斜带;古城墟斜坡带和罗布庄断凸带。叠瓦式逆冲断层、花状构造、构造三角带、断展裙皱和披覆构造是英吉苏凹陷的主要变形样式。自三叠纪以来,不同时期的沉积中心自造山带向前陆方向迁移。中新生界变形的动力学和运动学是与塔里木板块南缘活动大陆边缘的板块拼贴事件和壳内拆离缩短作用有关。