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1.
The Helvetic nappes in the Swiss Alps form a classic fold-and-thrust belt related to overall NNW-directed transport. In western
Switzerland, the plunge of nappe fold axes and the regional distribution of units define a broad depression, the Rawil depression,
between the culminations of Aiguilles Rouge massif to the SW and Aar massif to the NE. A compilation of data from the literature
shows that, in addition to thrusts related to nappe stacking, the Rawil depression is cross-cut by four sets of brittle faults:
(1) NE-SW striking normal faults, (2) NW-SE striking normal faults and joints, (3) ENE-WSW striking and (4) WNW-ESE striking
normal plus dextral oblique-slip faults. Fault set 1 was probably initiated during sedimentation and reactivated during nappe
stacking, whereas the other fault sets formed after emplacement of the Helvetic nappes. We studied in detail two well-exposed
parallel fault zones from set 4, the Rezli fault zones (RFZ) in the Wildhorn Nappe. They are SW-dipping oblique-slip faults
with a total displacement across the two fault zones of ~200 m vertically and ~680 m horizontally. The fault zones crosscut
four different lithologies: limestone, intercalated marl and limestone, marl and sandstone. The internal architecture of the
RFZ strongly depends on the lithology in which they developed. In the limestones, they consist of extension veins, stylolites,
cataclasites and cemented gouge, in the intercalated marls and limestones of shear zones, brittle fractures and chaotic folds,
in the marls of anastomosing shear zones, pressure solution seams and veins and in the sandstones of coarse breccia, brittle
faults and extension veins. Sharp, discrete fault planes within the broader fault zones cross-cut all lithologies. Fossil
fault zones in the Rezli area can act as a model for studying processes still occurring at deeper levels in this seismically
active region. 相似文献
2.
Nappe displacement in the Scandinavian Caledonides 总被引：1，自引：0，他引：1
David G. Gee 《Tectonophysics》1978,47(3-4)
Large areas of the Scandinavian Caledonides are eroded to the level of the basement/cover contact. Relationships between the Precambrian crystalline basement (largely Svecofennian-Dalslandian, 1800-1000 m.y.) and cover sequences are exposed both in transverse profiles through the mountain belt and along the belt in the various windows. These relationships provide an unique opportunity for studying the basement configuration, character of basement involvement and general nappe geometry. Major allochthonous units of the central part of the Scandinavian Caledonides — the Offerdal, Särv and Seve-Köli Nappe Complex — have been shown to wedge out westwards, having been displaced eastwards from environments along and west of the present Norwegian coast. Recent investigations have shown that these units (the Offerdal, Särv and Seve) reappear in western Norway as major pinch-and-swell structures, the lenses reaching thicknesses in the order of 2 km and with long axes of several tens of kilometres. Within the western parts of the Swedish Caledonides the thicker parts of the lenses approximately coincide with the axes of the late synforms which fold basement and cover together. Further west, in Norway, the tensing appears to be unrelated to the geometry of these major folds.This evidence increases estimates of nappe displacement distance (now thought to be in the order of at least 1000 km). At the same time it emphasizes that translation may account for only about half of this amount, the rest being achieved by stretching of the nappes. Apparently, a nappe sequence built up in the west which subsequently collapsed, leading to continued displacement eastwards on to the Baltoscandian Platform. Whereas basement shortening is of the order of several tens to perhaps hundreds of kilometres in the western part of the central Scandes, it is of lesser importance from central Trøndelag eastwards, a distance of about two hundred kilometres, to the Caledonian Front.Biostratigraphic evidence from the late-orogenic intramontane basins, taken in relation to the youngest units involved in the nappes, requires nappe translation into western Norway to have occurred after the Llandoverian (Köli Supergroup) and prior to the (Ludlovian?) Downtonian (Hitra Formation) deposition in the intramontane basins. The nappes contain sequences derived from a variety of probable oceanic and continental margin environments, and this translation may greatly exceed the minimum estimate of five hundred kilometres. Further displacement eastwards occurred during uplift of seaboard Norway and accompanied sedimentation both in the intra- and extramontane basins. The latter were not finally influenced by the décollement tectonics until after the Early Devonian.This evidence suggests that a compressive regime dominated the early phases of orogenesis during basement shortening, build up of the nappe pile and translation of these denser units on to the western margin of the Baltoscandian Platform. This compression subsequently gave way to a gravity regime, collapse and stretching of the nappes dominating the late phases of displacement on to the Baltoscandian Platform. 相似文献
3.
The restoration of thrust systems and displacement continuity around the Mont Blanc massif,NW external Alpine thrust belt 总被引：1，自引：0，他引：1
Robert W.H. Butler 《Journal of Structural Geology》1985,7(5):569-582
Foreland-propagating external thrust belts may be considered as essentially plane strain phenomena so that displacements can be correlated throughout their linked, three-dimensional fault geometry. This approach has been applied to part of the northwest external French-Swiss Alps, around the Mont Blanc basement massif. Imbricates of basement and cover sequences on the SW margin of this massif restore to a width in excess of 77 km with an implicit shortening of at least 67 km. These displacements can be correlated with those in the neighbouring Helvetic nappes by transferring movements, via lateral branch lines, onto the Mont Blanc thrust. By reappraising thrust geometries, the Helvetic/Ultrahelvetic nappe complex has been restored to a width of 114 km to the ESE of the Aiguilles Rouges basement massif. Displacements on the internal (SE) margin of the Mont Blanc massif, estimated by balanced sections and a restoration of the Ultrahelvetic klippen in the sub-alps, exceed 59 km. Thrust continuity, incorporating the restorations of nappes and imbricate geometries around the Mont Blanc massif, is illustrated on a crude, restored branch-line map which also serves as a preliminary palaeogeographic reconstruction. External thrust systems, to the east of the external Belledonne/Aiguilles Rouges massif, restore to a width of at least 140 km in the footwall to the Frontal Pennine thrust. 相似文献
4.
The classical concept of the nappe structure of the central Northern Calcareous Alps (NCA) is in contradiction with modern stratigraphic, structural, metamorphic and geochronological data. We first perform a palinspastic restoration for the time before Miocene lateral tectonic extrusion, which shows good continuity of structures, facies and diagenetic/metamorphic zones. We present a new nappe concept, in which the Tirolic unit practically takes the whole area of the central NCA and is divided into three subunits (nappes): Lower and Upper Tirolic subunit, separated by the Upper Jurassic Trattberg Thrust, and the metamorphic Ultra-Tirolic unit. The Hallstatt (Iuvavic) nappe(s) formed the highest unit, but were completely destroyed by erosion after nappe stacking. Remnants of the Hallstatt nappes are only represented by components of up to 1 km in size in Middle/Upper Jurassic radiolaritic wildflysch sediments ("Hallstatt Mélange" belonging to the Tirolic unit). Destruction of the continental margin started in Middle to Upper Jurassic time and prograded from the oceanic side towards the shelf. The original substratum of the external nappes (Bavaric units) of the NCA was largely the Austroalpine crystalline basement, of the internal nappes (Tirolic units) the weakly metamorphosed Palaeozoic sequences (Greywacke Zone and equivalents). Eocene movements caused limited internal deformation in the Tirolic unit. 相似文献
5.
造山带逆冲推覆构造研究的主要新进展 总被引：9，自引：0，他引：9
造山带逆冲推覆构造研究是造山带研究中最为重要的课题之一。造山带外带即前陆褶皱冲断带(主要发育盖层冲断推覆体,一般遵循薄皮构造变形规则)与造山带内带(主要是基底褶皱推覆体,呈现厚皮构造变形规律)结晶逆冲推覆构造的几何学、运动学特征存在较大差异,二者形成机制也不相同,但其间仍有紧密的联系。近20年来造山带逆冲推覆构造研究的主要新进展为:①前陆褶皱冲断带逆冲断层及其相关褶皱的几何学特征分析已趋定量化,对其组合类型与演化时序有了更全面的认识,且对前陆褶皱冲断带的发展演化模式取得了新的共识,即遵循临界库仑楔模式;②平衡剖面技术在前陆褶皱冲断带的应用已从二维平衡与复原演进到三维平衡与复原,且日渐计算机化;③对造山带内带结晶基底逆冲推覆构造的主要类型(C型与F型逆冲岩席)及其特征已有较深的理解;④对前陆褶皱冲断带与结晶基底逆冲构造的相互关系及其形成演化模式有了新认识。目前造山带逆冲推覆构造研究过程中存在的主要问题为:①造山带内带结晶逆冲推覆构造的研究比较薄弱;②造山带晚期走滑构造及伸展构造的叠加与改造使得造山带内结晶逆冲推覆构造更为复杂化,致使其研究难度加大;③全面、精细的造山带深部地球物理资料较缺乏;④造山带内结晶逆冲岩席变形变质历史与超高压变质岩的形成机制及折返过程之间的关系尚未揭示清楚。在今后研究过程中应加强对上述问题的深入研究。 相似文献
6.
The main aims of this study are to show (i) that non-cylindrical three-dimensional (3D) fold shapes and patterns can form during a single, unidirectional shortening event and (ii) that numerical reverse modeling of 3D folding is a feasible method to reconstruct the formation of 3D buckle-folds. 3D viscous (Newtonian) single-layer folding is numerically simulated with the finite element method to investigate the formation of fold shapes during one shortening event. An initially flat layer rests on a matrix with smaller viscosity and is shortened in one direction parallel to the layering. Forward modeling with different initial geometrical perturbations on the flat layer and different lateral boundary conditions generates non-cylindrical 3D fold shapes and patterns. The simulations show that, in reality, the initial layer geometry and the boundary conditions strongly control the final fold geometry. Fold geometries produced from the forward folding models are used as initial setting in numerical reverse folding models with parameters identical to those of forward models. These reverse models accurately reconstruct the initial geometry of forward models with also only one extension event parallel to the previous shortening direction. The starting geometry of the forward models is inaccurately reconstructed by the reverse models if a significantly different viscosity ratio than in the forward models is used. This work demonstrates that reverse modeling has a high potential for reconstructing the deformation history of folded regions and rheological constraints such as viscosity ratio. Reverse models may be applied to natural 3D fold shapes and patterns in order to determine if they formed (i) during a single or multiple deformation events and (ii) as active buckle-folds with a viscosity ratio 1 or as passive, kinematic folds without buckling. This approach may find much application to fold interference patterns, in particular. 相似文献
7.
The Helvetic nappes in Switzerland consist of sediments, which have been sheared off and thrust over the crystalline basement of the European passive continental margin during Alpine orogeny. Their basal shear zones usually root above the external crystalline massifs. However, the mechanisms that initiated the shear zones and the associated nappe formation are still debated. We perform two-dimensional numerical simulations of the shearing of linear viscous fluids above a linear viscous fluid with considerably higher viscosity (quasi-undeformable). The boundary between the fluid, mimicking the sediments, and the quasi-undeformable fluid, mimicking the basement, exhibits geometrical perturbations, mimicking half-grabens. These geometrical perturbations can trigger significant strain localization and the formation of shear zones within the linear viscous fluid although no rheological softening mechanism is active. This kinematic, ductile strain localization is caused by the half-grabens and the viscosity ratio between basement and sediments. The viscosity ratio has a strong control on the kinematics of strain localization, whereas the depth of the half-grabens has a weak control. For sediment viscosities in the order of 1021 Pas and typical half-graben geometries of 5 km depth and 25 km width the localization generates (a) low-angle shear zones at the basement-sediment interface, but also entirely within the sediments, (b) horizontal transport >10 km associated with the shear zones, (c) shear zones with thickness in the order of 100 m, (d) an ordered stacking of model nappes and (e) shear zones that root above the basement. The results suggest that tectonic inheritance in the form of half-grabens and associated kinematic strain localization could have been the triggering mechanism for Helvetic nappe formation, and not rheological softening mechanisms, which might, however, have subsequently further intensified shear localization significantly. 相似文献
8.
Fold-and-thrust belts are prominent structures that occur at the front of compressional orogens. To unravel the tectonic and metamorphic evolution of such complexes, kinematic investigations, quantitative microstructural analysis and geothermometry (calcite–graphite, calcite–dolomite) were performed on carbonate mylonites from thrust faults of the Helvetic nappe stack in Central Switzerland. Paleo-isotherms of peak temperature conditions and cooling stages (fission track) of the nappe pile were reconstructed in a vertical section and linked with the microstructural and kinematic evolution. Mylonitic microstructures suggest that under metamorphic conditions close to peak temperature, strain was highly localized within thrust faults where deformation temperatures spatially continuously increased in both directions, from N to S within each nappe and from top–down in the nappe stack, covering a temperature range of 180–380 °C. Due to the higher metamorphic conditions, thrusting of the lowermost nappe, the Doldenhorn nappe, was accompanied by a much more pronounced nappe internal ductile deformation of carbonaceous rock types than was the case for the overlying Wildhorn- and Gellihorn nappes. Ongoing thrusting brought the Doldenhorn nappe closer to the surface. The associated cooling resulted in a freezing in of the paleo-isotherms of peak metamorphic conditions. Contemporaneous shearing localized in the basal thrust, initially still in the ductile deformation regime and finally as brittle faulting and cataclasis inducing ultimately an inverse metamorphic zonation. With ongoing exhumation and the formation of the Helvetic antiformal nappe stack, a bending of large-scale tectonic structures (thrusts, folds), peak temperature isotherms and cooling isotherms occurred. While this local bending can directly be attributed to active deformation underneath the section investigated up to times of 2–3 ma, a more homogeneous uplift of the entire region is suggested for the very late and still active exhumation stage. 相似文献
9.
Alpine polyphase tectono-metamorphic evolution of the South Carpathians: A new overview 总被引：2，自引：0，他引：2
Viorica Iancu Tudor Berza Antoneta Seghedi Ion Gheuca Horst-Peter Hann 《Tectonophysics》2005,410(1-4):337-365
The main terrains involved in the Cretaceous–Tertiary tectonism in the South Carpathians segment of the European Alpine orogen are the Getic–Supragetic and Danubian continental crust fragments separated by the Severin oceanic crust-floored basin. During the Early–Middle Cretaceous times the Danubian microplate acted initially as a foreland unit strongly involved in the South Carpathians nappe stacking. Multistage folding/thrusting events, uplift/erosion and extensional stages and the development of associated sedimentary basins characterize the South Carpathians during Cretaceous to Tertiary convergence and collision events. The main Cretaceous tectogenetic events responsible for contraction and crustal thickening processes in the South Carpathians are Mid-Cretaceous (“Austrian phase”) and Latest Cretaceous (“Laramide” or “Getic phase”) in age. The architecture of the South Carpathians suggests polyphase tectonic evolution and mountain building and includes from top to bottom: the Getic–Supragetic basement/cover nappes, the Severin and Arjana cover nappes, and Danubian basement/cover nappes, all tectonically overriding the Moesian Platform. The Severin nappe complex (including Obarsia and Severin nappes) with Late Jurassic–Early Cretaceous ophiolites and turbidites is squeezed between the Danubian and Getic–Supragetic basement nappes as a result of successive thrusting of dismembered units during the inferred Mid- to Late Cretaceous subduction/collision followed by tectonic inversion processes.
Early Cretaceous thick-skinned tectonics was replaced by thin-skinned tectonics in Late Cretaceous. Thus, the former Middle Cretaceous “Austrian” nappe stack and its Albian–Lower Senonian cover got incorporated in the intra-Senonian “Laramide/Getic” stacking of the Getic–Supragetic/Severin/Arjana nappes onto the Danubian nappe duplex. The two contraction events are separated by an extensional tectonic phase in the upper plate recorded by the intrusion of the “Banatitic” magmas (84–73 Ma). The overthrusting of the entire South Carpathian Cretaceous nappe stack onto the fold/thrust foredeep units and to the Moesian Platform took place in the Late Miocene (intra-Sarmatian) times and was followed by extensional events and sedimentary basin formation. 相似文献
10.
福建省天湖山煤矿区F31推覆断层及找煤方向探讨 总被引：1，自引：0，他引：1
福建省天湖山煤矿区处于闽西南坳陷东条带,推覆构造极其发育,以F31和F1两条推覆断层表现最为突出。据矿区开采资料证实,F31断层下盘童子岩组为—总体向西倾斜向南倾伏、轴向NNE的紧密线状褶皱,断层较稀少;上盘构造复杂,断层发育,由F31所派生的低序次断层往往为逆掩或逆冲断层,与主断层面组成“入”字型构造,造成童子岩组地层多次重复,同时派生了更低序次的断层组成羽毛状构造。通过对F31推覆断层特征以及应力场分析研究,认为其演进过程为：童子岩期前后的成岩沉积—印支期侧向挤压形成褶皱—印支运动及其后由于侧向挤压形成软弱滑动面及断裂—燕山早期侧向挤压造成低角度推覆断层。根据该矿区构造研究成果,提出了矿区外围及深部的5个找煤方向。 相似文献
11.
Antonio Funedda 《International Journal of Earth Sciences》2009,98(7):1625-1642
In the Variscan foreland of SW-Sardinia (Western Mediterranean sea), close to the leading edge of the nappe zone, nappe emplacement
caused folding and repetition of stratigraphic successions, km-scale offset of stratigraphic boundaries and an extensive brittle-ductile
shear zone. Thrusts assumed a significant role, accommodating a progressive change of shortening direction and forming complicated
thrust triangle zones. During thrust emplacement of the nappes, strong penetrative deformation affected rocks beneath the
basal thrust of the nappe stack and produced coeval structures with both foreland-directed and hinterland-directed (backthrusting)
shear sense. Cross-cutting and overprinting relationships clearly show that the shortening direction changed progressively
from N–S to E–W, producing in sequence: (1) E–W trending open folds contemporaneous with early nappe emplacement in the nearby
nappe zone; (2) recumbent, quasi-isoclinal folds with axial plane foliation and widespread, “top-towards-the-SW”, penetrative
shearing; (3) N–S trending folds with axial plane foliation, contemporaneous with late nappe emplacement; (4) backthrusts
and related asymmetrical folds developed during the final stages of shortening, postdating foreland-verging structures. Structures
at (3) and (4) occurred during the same tectonic transport “top-towards-the-E” of the nappe zone over the foreland. The several
generations of folds, thrusts, and foliations with different orientations developed, result in a complex finite structural
architecture, not completely explicable by the theoretical model proposed up to date. 相似文献
12.
13.
Fault-propagation folding associated with an upward propagating fault in the Gilbertown graben system is revealed by well-based 3-D subsurface mapping and dipmeter analysis. The fold is developed in the Selma chalk, which is an oil reservoir along the southern margin of the graben. Area-depth-strain analysis suggests that the Cretaceous strata were growth units, the Jurassic strata were pregrowth units, and the graben system is detached in the Louann Salt.The growth trishear model has been applied in this paper to study the evolution and kinematics of extensional fault-propagation folding. Models indicate that the propagation to slip (p/s) ratio of the underlying fault plays an important role in governing the geometry of the resulting extensional fault-propagation fold. With a greater p/s ratio, the fold is more localized in the vicinity of the propagating fault. The extensional fault-propagation fold in the Gilbertown graben is modeled by both a compactional and a non-compactional growth trishear model. Both models predict a similar geometry of the extensional fault-propagation fold. The trishear model with compaction best predicts the fold geometry. 相似文献
14.
柯坪塔格推覆构造几何学、运动学及其构造演化 总被引：29，自引：1，他引：29
大量野外构造地质调查和深部构造解释表明柯坪塔格推覆构造由多组倒转复式背斜、复式箱状背斜构成的推覆体及其前缘逆冲断裂组成 ,由寒武系—第四系组成的推覆体由北向南逆—斜冲 ,平面上构成向南凸出的弧形推覆构造 ;普昌断裂由各不相连的逆冲斜冲断裂段组成 ,而不是完整的一条走滑断层 ,各推覆体前缘逆冲断裂与各推覆体的普昌断裂段共同构成统一的前缘逆冲斜冲逆冲断裂和推覆构造系统 ;普昌断裂段以西的推覆体具有向东抬升、向西倾覆的鼻状构造特征 ,普昌断裂段以东的推覆体具有向西抬升、向东倾覆的鼻状构造特征 ,普昌基底隆起带是巴楚隆起隐伏在柯坪塔格推覆构造之下的部分。各推覆体前缘断裂在深部均归并于统一的寒武系底部的滑脱面 ,其南浅北深 ,东浅西深 (普昌隆起带以西 )或西浅东深 (普昌隆起带以东 ) (6 10km ) ,埋深较大区发育多组滑脱面。柯坪塔格推覆构造的形成时期为晚第四纪 ,为现今活动的推覆构造系统。文中认为各推覆体向南西的倾覆端基底滑脱面和中新生界内部的滑脱面没有贯通 ,是未来 6级以上地震的发震构造部位。 相似文献
15.
JIA Qiupeng JIA Dong LUO Liang CHEN Zhuxin LI Yiquan DENG Fei SUN Shengsi LI Haibin 《《地质学报》英文版》2009,83(2)
Fold terminations are key features in the study of compressional fault-related folds. Such terminations could be due to loss of displacement on the thrust fault or/and forming a lateral or oblique ramp. Thus, high-quality seismic data would help unambiguously define which mechanism should be responsible for the termination of a given fault-related fold. The Qiongxi and Qiongxinan structures in the Sichuan Basin, China are examples of natural fault-propagation folds that possess a northern termination and a structural saddle between them. The folds/fault geometry and along-strike displacement variations are constrained by the industry 3-D seismic volume. We interpret that the plunge of the fold near the northern termination and the structural saddle are due to the loss of displacement along strike. The fault geometry associated with the northern termination changes from a flat-ramp at the crest of the Qiongxinan structure, where displacement is the greatest, to simply a ramp near the northern tip of the Qiongxi structure, without forming a lateral or oblique ramp. In this study, we also use the drainage pattern, embryonic structure preserved in the crest of the Qiongxinan structure and the assumption that displacement along a fault is proportional to the duration of thrusting to propose a model for the lateral propagation of the Qiongxinan and Qiongxi structures. Specifically, we suggest that the structure first initiated as an isolated fault ramp within brittle units. With increased shortening, the fault grows to link with lower detachments in weaker shale units to create a hybridized fault-propagation fold. Our model suggests a possible explanation for the lateral propagation history of the Qiongxinan and Qiongxi structures, and also provides an alternative approach to confirming the activity of the previous Pingluoba structure in the southwestern Sichuan Basin in the late Cenozoic. 相似文献
16.
17.
P. D. CROWLEY 《Journal of Metamorphic Geology》1990,8(6):615-628
Within the Çokkul synform, Caledonian metamorphic rocks of the Middle Köli Nappe Complex (MKNC) are in low-angle fault contact with the basement mylonites derived from the Precambrian Tysfjord granite-gneiss. In the synform, the MKNC is composed of four fault-bounded nappes each of which has a distinct tectonic stratigraphy composed of amphibolite-facies metamorphosed pelitic and psammitic schists with minor lensoidal bodies of mafic and ultramafic rocks. Pelitic rocks from the three structurally lowest nappes contain the low-variance AFM mineral assemblages gar + bio + staur and staur + ky + bio with mu + qtz + ilm, whereas staur and ky are absent from the highest nappe, the Kallakvare nappe. AFM mineral assemblages in the three lowest nappes indicate peak metamorphic temperatures of 610–660°C and peak pressures in excess of 600 MPa. Mineral assemblages from the Kallakvare nappe are not as diagnostic of metamorphic grade. However, rocks from that nappe contain coexisting plagioclases from both sides of the peristerite gap, suggesting lower-grade peak P–T conditions than those of the structurally lower nappes. In addition, biotite from the lower nappes is more Ti-rich than biotite from the Kallakvare nappe. However, gar–bio–mu–plag and gar–bio–ky–plag–qtz thermobarometry suggests that all four nappes equilibrated at approximately 525 ± 25°C and 700 ± 100 MPa. Gibbs method thermodynamic modelling of garnet zoning profiles suggests that the lower three nappes followed clockwise P–T paths that involved heating and compression to a metamorphic peak of approximately 575–625°C, 800 MPa followed by cooling and decompression to 525°C, 700 MPa. P–T paths calculated for the Kallakvare nappe show decompression and minor heating to a peak T of 500–525°C. In the lower nappes, staur and ky grew during the heating phase not seen by the highest nappe. The outer parts of the paths from all four nappes are approximately parallel, possibly recording the emplacement of the Kallakvare nappe onto the already stacked lower three nappes at some time following the metamorphic peak. These P–T paths suggest that the sole fault of the Kallakvare nappe is a normal fault. Garnet zonation thus appears to record a previously unrecognized phase of uplift and tectonic thinning of the MKNC. This event appears to be restricted to the MKNC and to have occurred prior to the emplacement of the MKNC onto the Tysfjord granite-gneiss basement of Baltoscandia under greenschist-facies conditions. It may have been responsible for the uplift and cooling of the MKNC from 25–30 km amphibolite-facies conditions prior to its emplacement onto Baltoscandia under 15–20 km greenschist-facies conditions. The deformation zone associated with this normal fault is relatively narrow, generally less than 1 m thick. If this is typical of other detachment faults in the metamorphic infrastructure of the Scandinavian Caledonides, they may be relatively common, but not often recognized due to the detailed study needed to document them. 相似文献
18.
TANG Liangjie JIN Zhijun JIA Chengzao PI Xuejun CHEN Shaping XIE Huiwen WANG Ziyu Key Laboratory for Hydrocarbon Accumulation Ministry of Education Beijing Basin Reservoir Research Center University of Petroleum Beijing Institute of Petroleum Exploration Development SINOPEC Beijing PetroChina Company Limite Beijing Tarim Oilfield Company PetroChina Company Ltd. Kurle Xinjiang 《《地质学报》英文版》2004,78(3):691-700
The tectono-stratigraphic sequences of the Kuqa foreland fold-thrust belt in the northern Tarim basin, northwest China, can be divided into the Mesozoic sub-salt sequence, the Paleocene-Eocene salt sequence and the Oligocene-Quaternary supra-salt sequence. The salt sequence is composed mainly of light grey halite, gypsum, marl and brown elastics. A variety of salt-related structures have developed in the Kuqa foreland fold belt, in which the most fascinating structures are salt nappe complex. Based on field observation, seismic interpretation and drilling data, a large-scale salt nappe complex has been identified. It trends approximately east-west for over 200 km and occurs along the west Qiulitag Mountains. Its thrusting displacement is over 30 km. The salt nappe complex appears as an arcuate zone projecting southwestwards along the leading edge of the Kuqa foreland fold belt. The major thrust fault is developed along the Paleocene-Eocene salt beds. The allochthonous nappes comprise large north-dipping 相似文献
19.
Albrecht Steck Franco Della Torre Franz Keller Hans-Rudolf Pfeifer Johannes Hunziker Henri Masson 《Swiss Journal of Geoscience》2013,106(3):427-450
The Lepontine dome represents a unique region in the arc of the Central and Western Alps, where complex fold structures of upper amphibolite facies grade of the deepest stage of the orogenic belt are exposed in a tectonic half-window. The NW-verging Mont Blanc, Aar und Gotthard basement folds and the Lower Penninic gneiss nappes of the Central Alps were formed by ductile detachment of the upper European crust during its Late Eocene–Early Oligocene SE-directed underthrust below the upper Penninic and Austroalpine thrusts and the Adriatic plate. Four underthrust zones are distinguished in the NW-verging stack of Alpine fold nappes and thrusts: the Canavese, Piemont, Valais and Adula zones. Up to three schistosities S1–S3, folds F1–F3 and a stretching lineation XI with top-to-NW shear indicators were developed in the F1–F3 fold nappes. Spectacular F4 transverse folds, the SW-verging Verzasca, Maggia, Ziccher, Alpe Bosa and Wandfluhhorn anticlines and synclines overprint the Alpine nappe stack. Their formation under amphibolite facies grade was related to late ductile folding of the southern nappe roots during dextral displacement of the Adriatic indenter. The transverse folding F4 was followed since 30 Ma by the pull-apart exhumation and erosion of the Lepontine dome. This occurred coevally with the formation of the dextral ductile Simplon shear zone, the S-verging backfolding F5 and the formation of the southern steep belt. Exhumation continued after 18 Ma with movement on the brittle Rhone-Simplon detachment, accompanied by the N-, NW- and W-directed Helvetic and Dauphiné thrusts. The dextral shear is dated by the 29–25 Ma crustal-derived aplite and pegmatite intrusions in the southern steep belt. The cooling by uplift and erosion of the Tertiary migmatites of the Bellinzona region occurred between 22 and 18 Ma followed by the exhumation of the Toce dome on the brittle Rhone–Simplon fault since 18 Ma. 相似文献
20.
On the basis of detailed geological mapping in the Talea Ori of Crete, metamorphic rocks previously interpreted as basement to the Plattenkalk Series are re-interpreted as down-faulted parts of the overlying Phyllite-Quartzite Series nappe. A supposed unconformity separating these two units is shown to be a high-angle fault. The Phyllite-Quartzite Series and overlying nappes were affected by two major deformational phases, whereas the Plattenkalk Series has a simpler structural history and was folded and imbricated by southwards-directed overthrusting which emplaced the Phyllite-Quartzite Series nappe and other overlying nappes in the Oligocene. We reject previous models of a huge inversion of the Plattenkalk Series and we also consider that considerable local inversion by tight to isoclinal folding and thrusting means that the stratigraphic thickness is much less than previously appreciated. The differences between the structural and sedimentological histories of the Plattenkalk Series and the overlying nappes implies that they were separated by a major crustal discontinuity, such as a transform or transcurrent fault, before the Oligocene overthrusting. 相似文献