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1.
Well‐calibrated seismic interpretation in the Halten Terrace of Mid‐Norway demonstrates the important role that structural feedback between normal fault growth and evaporite mobility has for depocentre development during syn‐rift deposition of the Jurassic–Early Cretaceous Viking and Fangst Groups. While the main rift phase reactivated pre‐existing structural trends, and initiated new extensional structures, a Triassic evaporite interval decouples the supra‐salt cover strata from the underlying basement, causing the development of two separate fault populations, one in the cover and the other confined to the pre‐salt basement. Detailed displacement–length analyses of both cover and basement fault arrays, combined with mapping of the component parts of the syn‐rift interval, have been used to reveal the spatial and temporal evolution of normal fault segments and sediment depocentres within the Halten Terrace area. Significantly, the results highlight important differences with traditional models of normal fault‐controlled subsidence, including those from parts of the North Sea where salt is absent. It can now be shown that evaporite mobility is intimately linked to the along‐strike displacement variations of these cover and basement faults. The evaporites passively move beneath the cover in response to the extension, such that the evaporite thickness becomes greatest adjacent to regions of high fault displacement. The consequent evaporite swells can become large enough to have pronounced palaeobathymetric relief in hangingwall locations, associated with fault displacement maxima– the exact opposite situation to that predicted by traditional models of normal fault growth. Evaporite movement from previous extension also affects the displacement–length relationships of subsequently nucleated or reactivated faults. Evaporite withdrawal, on the other hand, tends to be a later‐stage feature associated with the high stress regions around the propagating tips of normal faults or their coeval hangingwall release faults. The results indicate the important effect of, and structural feedback caused by, syn‐rift evaporite mobility in heavily modifying subsidence patterns produced by normal fault array evolution. Despite their departure from published models, the results provide a new, generic framework within which to interpret extensional fault and depocentre development and evolution in areas in which mobile evaporites exist.  相似文献   

2.
The Alhama de Murcia and Crevillente faults in the Betic Cordillera of southeast Spain form part of a network of prominent faults, bounding several of the late Tertiary and Quaternary intermontane basins. Current tectonic interpretations of these basins vary from late‐orogenic extensional structures to a pull‐apart origin associated with strike–slip movements along these prominent faults. A strike–slip origin of the basins, however, seems at variance both with recent structural studies of the underlying Betic basement and with the overall basin and fault geometry. We studied the structure and kinematics of the Alhama de Murcia and Crevillente faults as well as the internal structure of the late Miocene basin sediments, to elucidate possible relationships between the prominent faults and the adjacent basins. The structural data lead to the inevitable conclusion that the late Miocene basins developed as genuinely extensional basins, presumably associated with the thinning and exhumation of the underlying basement at that time. During the late Miocene, neither the Crevillente fault nor the Alhama de Murcia fault acted as strike–slip faults controlling basin development. Instead, parts of the Alhama de Murcia fault initiated as extensional normal faults, and reactivated as contraction faults during the latest Miocene–early Pliocene in response to continued African–European plate convergence. Both prominent faults presently act as reverse faults with a movement sense towards the southeast, which is clearly at variance with the commonly inferred dextral or sinistral strike–slip motions on these faults. We argue that the prominent faults form part of a larger scale zone of post‐Messinian shortening made up of SSE‐ and NNW‐directed reverse faults and NE to ENE‐trending folds including thrust‐related fault‐bend folds and fault‐propagation folds, transected and displaced by, respectively, WNW‐ and NNE‐trending, dextral and sinistral strike–slip (tear or transfer) faults.  相似文献   

3.
The Plataforma Burgalesa is a partly exposed extensional forced fold system with an intermediate salt layer, which has developed along the southern portion of the Basque‐Cantabrian Basin from Malm to Early Cretaceous as part of the Bay of Biscay‐Pyrenean rift system. Relationships between syn‐ and pre‐rift strata of the supra‐salt cover sequence and distribution of intra‐cover second‐order faults are observed both along seismic sections and at the surface. These relationships indicate an along‐strike variability of the extensional structural style. After a short period of salt mobilization and forced folding, high slip rates in the central portion of the major basement faults have rapidly promoted brittle behaviour of the salt layer, preventing further salt mobilization and facilitating the propagation of the fault across the salt layer. In contrast, at the tip regions of basement faults, slower slip rates have facilitated ductile salt behaviour, ensuring its further evaporite evacuation, preventing fault propagation across the salt layer and, in essence, allowing for a long‐living forced folding process. Our results indicate the important effect of along‐strike variation in displacement and displacement rates in controlling evaporite behaviour in extensional basins. Amount of displacement and displacement rates are key factors controlling the propagation of basement faults across evaporite layers. In addition, growth strata patterns are recognized as a powerful tool for constraining the up‐dip propagation history of basement faults in extensional fault‐related fold systems with intermediate décollement levels.  相似文献   

4.
《Basin Research》2018,30(Z1):363-381
Inversion of pre‐existing extensional fault systems is common in rift systems, back‐arc basins and passive margins. It can significantly influence the development of structural traps in hydrocarbon basins. The analogue models of domino‐style basement fault systems shown in this paper produced, on extension, characteristic hangingwall growth stratal wedges that, when contracted and inverted, formed classic inversion harpoon geometries and asymmetric hangingwall contractional fault‐propagation folds. Segmented footwall shortcut faults formed as the basement faults were progressively back‐rotated and steepened. The pre‐existing extensional fault architectures, basement fault geometries and the relative hangingwall and footwall block rotations exerted fundamental controls on the inversion styles. Digital image correlation (DIC) strain monitoring illustrated complex vertical fault segmentation and linkage during inversion as the major faults were reactivated and strain was progressively transferred onto footwall shortcut faults. Hangingwall deformation during inversion was dominated by significant back‐rotation as the inversion progressed. The mechanical stratigraphy of the cover sequences strongly influenced the fold and fault evolution of the reactivated fault systems. The implications of the experimental results for the interpretation and analysis of inversion structures are discussed and are compared with natural examples of inverted basement‐involved extensional faults observed in seismic datasets.  相似文献   

5.
The Emme Delta is a small glacilacustrine delta, which developed on the southern flank of the Wesergebirge Mountains in NW Germany. Shallow shear‐wave seismic surveys allow a detailed assessment of the structural style of the delta body. Two different fault systems are developed within the delta, both showing syn‐sedimentary activity. The faults have planar to slightly listric geometries and show vertical offsets in a range of 2–15 m. They form small graben and half‐graben systems, which locally show roll‐over structures. The fill of the half‐grabens has a wedge‐shaped geometry, with the greatest sediment thickness close to the fault. The fault system in the upper portion of the Emme Delta is restricted to the delta body and probably gravity induced. In the lower portion of the delta, normal faults occur that originate in the underlying Jurassic basement rocks and penetrate into the delta deposits. The grid of seismic lines shows that the normal faults are trending E–W. This fits to a late Triassic–early Jurassic deformation phase in the Central European Basin System. We hypothese that these faults were reactivated during the Pleistocene by the advancing ice‐sheet, water and sediment loading. Based on the seismic data set, an overall model for the reactivation of the basement fault was developed. The advancing ice‐sheet caused far field extension, which might have reactivated pre‐existing normal faults. Later, the fault activity was enhanced due to sediment and water loading. In addition, high pore pressure due to lake formation might have supported the slip processes along the faults. After glacial unloading and lake drainage, the fault activity stopped.  相似文献   

6.
A series of analogue models are used to demonstrate how the multistage development of the Mid‐Polish Trough (MPT) could have been influenced by oblique basement strike–slip faults. Based on reinterpretation of palaeothickness, facies maps and published syntheses of the basin development, the following successive stages in the Mesozoic history of the south eastern part of the MPT were simulated in the models: (1) Oblique extension of the NW segment of the MPT connected with sinistral movement along the Holy Cross Fault (HCF, Early Triassic–latest Early Jurassic). (2) Oblique extension of both NW and SE segment of the MPT, parallel to the HCF (latest Early and Middle Jurassic). (3) Oblique extension of the SE segment of the MPT and much lesser extension of its NW segment connected with dextral movement along the HCF (Early Oxfordian–latest Early Kimmeridgian). (4) Oblique extension of the SE segment of the MPT and much lesser extension of its NW segment connected with dextral movement along the Zawiercie Fault (ZF, latest Early Kimmeridgian–Early Albian). (5) Oblique inversion of the NW segment of the MPT connected with dextral movement along the HCF (Early Albian–latest Cretaceous). (6) Oblique inversion of the SE segment of the MPT along the W–E direction (latest Cretaceous–Palaeogene). The different sense of movements of these two basement strike–slip faults (HCF and ZF) resulted in distinct segmentation of the basin and its SW margin by successive systems of extensional en‐echelon faults. The overall structure of this margin is controlled by the interference of the border normal faults with the en‐echelon fault systems related to successive stages of movement along the oblique strike–slip faults. This type of en‐echelon fault system is absent in the opposite NE‐margin of the basin, which was not affected by oblique strike–slip faults. The NE‐margin of the basin is outlined by a typical, steep and distinctly marked rift margin fault zone, dominated by normal and dip–slip/strike–slip faults parallel to its axis. Within the more extended segment of the basin, extensive intra‐rift faults and relay ramps develop, which produce topographic highs running across the basin. The change in the extension direction to less oblique relative to the basin axis resulted in restructuring of the fault systems. This change caused shifting of the basin depocentre to this margin. Diachronous inversion of the different segments of the basin in connection with movement along one of the oblique basement strike–slip faults resulted in formation of a pull‐apart sub‐basin in the uninverted SE‐segment of the basin. The results of the analogue models presented here inspire an overall kinematic model for the southeastern segment of the MPT as they provide a good explanation of the observed structures and the changes in the facies and palaeothickness patterns.  相似文献   

7.
Complex arrays of faults in extensional basins are potentially influenced by pre‐existing zones of weakness in the underlying basement, such as faults, shear zones, foliation, and terrane boundaries. Separating the influence of such basement heterogeneities from far‐field tectonics proves to be challenging, especially when the timing and character of deformation cannot be interpreted from seismic reflection data. Here we aim to determine the influence of basement heterogeneities on fault patterns in overlying cover rocks using interpretations of potential field geophysical data and outcrop‐scale observations. We mapped >1 km to meter scale fractures in the western onshore Gippsland Basin of southeast Australia and its underlying basement. Overprinting relationships between fractures and mafic intrusions are used to determine the sequence of faulting and reactivation, beginning with initial Early Cretaceous rifting. Our interpretations are constrained by a new Early Cretaceous U‐Pb zircon isotope dilution thermal ionization mass spectrometry age (116.04 ± 0.15 Ma) for an outcropping subvertical, NNW‐SSE striking dolerite dike hosted in Lower Cretaceous Strzelecki Group sandstone. NW‐SE to NNW‐SSE striking dikes may have signaled the onset of Early Cretaceous rifting along the East Gondwana margin at ca. 105–100 Ma. Our results show that rift faults can be oblique to their expected orientation when pre‐existing basement heterogeneities are present, and they are orthogonal to the extension direction where basement structures are less influential or absent. NE‐SW to ENE‐WSW trending Early Cretaceous rift‐related normal faults traced on unmanned aerial vehicle orthophotos and digital aerial images of outcrops are strongly oblique to the inferred Early Cretaceous N‐S to NNE‐SSW regional extension direction. However, previously mapped rift‐related faults in the offshore Gippsland Basin (to the east of the study area) trend E‐W to WNW‐ESE, consistent with the inferred regional extension direction. This discrepancy is attributed to the influence of NNE‐SSW trending basement faults underneath the onshore part of the basin, which caused local re‐orientation of the Early Cretaceous far‐field stress above the basement during rifting. Two possible mechanisms for inheritance are discussed—reactivation of pre‐existing basement faults or local re‐orientation of extension vectors. Multiple stages of extension with rotated extension vectors are not required to achieve non‐parallel fault sets observed at the rift basin scale. Our findings demonstrate the importance of (1) using integrated, multi‐scale datasets to map faults and (2) mapping basement geology when investigating the structural evolution of an overlying sedimentary basin.  相似文献   

8.
Studies of salt‐influenced rift basins have focused on individual or basin‐scale fault system and/or salt‐related structure. In contrast, the large‐scale rift structure, namely rift segments and rift accommodation zones and the role of pre‐rift tectonics in controlling structural style and syn‐rift basin evolution have received less attention. The Norwegian Central Graben, comprises a complex network of sub‐salt normal faults and pre‐rift salt‐related structures that together influenced the structural style and evolution of the Late Jurassic rift. Beneath the halite‐rich, Permian Zechstein Supergroup, the rift can be divided into two major rift segments, each comprising rift margin and rift axis domains, separated by a rift‐wide accommodation zone – the Steinbit Accommodation Zone. Sub‐salt normal faults in the rift segments are generally larger, in terms of fault throw, length and spacing, than those in the accommodation zone. The pre‐rift structure varies laterally from sheet‐like units, with limited salt tectonics, through domains characterised by isolated salt diapirs, to a network of elongate salt walls with intervening minibasins. Analysis of the interactions between the sub‐salt normal fault network and the pre‐rift salt‐related structures reveals six types of syn‐rift depocentres. Increasing the throw and spacing of sub‐salt normal faults from rift segment to rift accommodation zone generally leads to simpler half‐graben geometries and an increase in the size and thickness of syn‐rift depocentres. In contrast, more complex pre‐rift salt tectonics increases the mechanical heterogeneity of the pre‐rift, leading to increased complexity of structural style. Along the rift margin, syn‐rift depocentres occur as interpods above salt walls and are generally unrelated to the relatively minor sub‐salt normal faults in this structural domain. Along the rift axis, deformation associated with large sub‐salt normal faults created coupled and decoupled supra‐salt faults. Tilting of the hanging wall associated with growth of the large normal faults along the rift axis also promoted a thin‐skinned, gravity‐driven deformation leading to a range of extensional and compressional structures affecting the syn‐rift interval. The Steinbit Accommodation Zone contains rift‐related structural styles that encompass elements seen along both the rift margin and axis. The wide variability in structural style and evolution of syn‐rift depocentres recognised in this study has implications for the geomorphological evolution of rifts, sediment routing systems and stratigraphic evolution in rifts that contain pre‐rift salt units.  相似文献   

9.
The Kocaçay Basin (KÇB) is a key area in western Anatolia – a well‐known extended terrane where regional segmentation has received limited attention – for investigating strike‐slip faults kinematically linked to detachment faults. In this paper, we present results of an integrated sedimentologic, stratigraphic, and structural study of Miocene alluvial fan/fan‐delta/lacustrine deposits that accumulated in the KÇB, a NE‐trending basin with connections to the Menderes Metamorphic Core Complex (MCC). We mapped and evaluated most of the key faults in the KÇB, many for the first time, and recognised different deformation events in the study area near the E margin of the MCC. We also present field evidence for kinematic connections between low‐angle normal and strike‐slip faults which were developed in an intermittently active basement‐involved transfer zone in western Anatolia. We find that the KÇB contains a detailed record of Miocene transtensional sedimentation and volcanism that accompanied exhumation of the MCC. Structural data reveal that the basin was initially formed by transtension (D1 phase) and subsequently uplifted and deformed, probably as a result of early Pliocene wrench‐ to extension‐dominated deformation (D2 phase) overprinted by Plio‐Quaternary extensional tectonics (D3 phase). These results are consistent with progressive deformation wherein the axis of maximum extension remained in the horizontal plane but the intermediate and maximum shortening axes switched position in the vertical plane. Combining our results with published studies, we propose a new working hypothesis that the KÇB was a transtensional supradetachment basin during the Miocene. The hypothesis could provide new insights into intermittently active extension‐parallel zone of weakness in western Anatolia.These results also suggest that the termination of low‐angle normal fault systems within an extension parallel transfer zone may have resulted in a transtensional depressions which are different from classical supradetachment basins with respect to the sedimentation and deformational pattern of the basin infills.  相似文献   

10.
The thickness and distribution of early syn‐rift deposits record the evolution of structures accommodating the earliest phases of continental extension. However, our understanding of the detailed tectono‐sedimentary evolution of these deposits is poor, because in the subsurface, they are often deeply buried and below seismic resolution and sparsely sampled by borehole data. Furthermore, early syn‐rift deposits are typically poorly exposed in the field, being buried beneath thick, late syn‐rift and post‐rift deposits. To improve our understanding of the tectono‐sedimentary development of early syn‐rift strata during the initial stages of rifting, we examined quasi‐3D exposures in the Abura Graben, Suez Rift, Egypt. During the earliest stage of extension, forced folding above blind normal fault segments, rather than half‐graben formation adjacent to surface‐breaking faults, controlled rift physiography, accommodation development and the stratigraphic architecture of non‐marine, early syn‐rift deposits. Fluvial systems incised into underlying pre‐rift deposits and were structurally focused in the axis of the embryonic depocentre, which, at this time, was characterized by a fold‐bound syncline rather than a fault‐bound half graben. During this earliest phase of extension, sediment was sourced from the rift shoulder some 3 km to the NE of the depocentre, rather than from the crests of the flanking, intra‐basin extensional forced folds. Fault‐driven subsidence, perhaps augmented by a eustatic sea‐level rise, resulted in basin deepening and the deposition of a series of fluvial‐dominated mouth bars, which, like the preceding fluvial systems, were structurally pinned within the axis of the growing depocentre, which was still bound by extensional forced folds rather than faults. The extensional forced folds were eventually locally breached by surface‐breaking faults, resulting in the establishment of a half graben, basin deepening and the deposition of shallow marine sandstone and fan‐delta conglomerates. Because growth folding and faulting were coeval along‐strike, syn‐rift stratal units deposited at this time show a highly variable along‐strike stratigraphic architecture, locally thinning towards the growth fold but, only a few kilometres along‐strike, thickening towards the surface‐breaking fault. Despite displaying the classic early syn‐rift stratigraphic motif recording net upward‐deepening, extensional forced folding rather than surface faulting played a key role in controlling basin physiography, accommodation development, and syn‐rift stratal architecture and facies development during the early stages of extension. This structural and stratigraphic observations required to make this interpretation are relatively subtle and may go unrecognized in low‐resolution subsurface data sets.  相似文献   

11.
The Turkana rifted zone in northern Kenya is a long‐lived and polyphased rift system where the lack of well‐marked rift morphology makes it difficult to identify the zone of active deformation. A high‐density river network is exceptionally well developed over the study area and shows evidence of drainage anomalies that suggest recent fault‐induced movements at various scales. Correlation of surface drainage anomalies with Landsat remote sensing and deep seismic reflection data permits to characterize the deep geometry of the inferred fault structures. Seismic stratigraphy further allows distinction between the inherited (Oligocene–Pliocene) and the newly formed (<3.7 Ma) origin of the recent deformation. Evidence for neotectonics are observed (1) along a large‐scale transverse (EW) fault rooted at depth along a steep basement discontinuity (Turkwell), (2) along a rift‐parallel (NS) fault zone probably emplaced during the Pliocene–Pleistocene and currently bounding the Napedet volcanic plateau to the west and (3) over a round‐shaped uplifted zone caused by positive inversion tectonics (Kalabata). The major contribution of this work is the recognition of a broad (80 km wide) zone of recent/active extensional deformation in the Turkana Rift in contrast with the narrow (20 km wide) N10°E‐trending axial trough forming the Suguta valley to the south, and the Chew Bahir faulted basin to the north. These along‐strike variations in structural style are partly controlled by the occurrence of rejuvenated Oligocene–Miocene rift faults and long‐lived transverse discontinuities in the Turkana Rift area. More generally, this study has implications for the use of river drainage network about recent/active extensional domains with subdued topography and slow deformation rate.  相似文献   

12.
Lower Cretaceous early syn‐rift facies along the eastern flank of the Eastern Cordillera of Colombia, their provenance, and structural context, reveal the complex interactions between Cretaceous extension, spatio‐temporal trends in associated sedimentation, and subsequent inversion of the Cretaceous Guatiquía paleo‐rift. South of 4°30′N lat, early syn‐rift alluvial sequences in former extensional footwall areas were contemporaneous with fan‐delta deposits in shallow marine environments in adjacent hanging‐wall areas. In general, footwall erosion was more pronounced in the southern part of the paleorift. In contrast, early syn‐rift sequences in former footwall areas in the northern rift sectors mainly comprise shallow marine supratidal sabkha to intertidal strata, whereas hanging‐wall units display rapid transitions to open‐sea shales. In comparison with the southern paleo‐rift sector, fan‐delta deposits in the north are scarce, and provenance suggests negligible footwall erosion. The southern graben segment had longer, and less numerous normal faults, whereas the northern graben segment was characterized by shorter, rectilinear faults. To the east, the graben system was bounded by major basin‐margin faults with protracted activity and greater throw as compared with intrabasinal faults to the west. Intrabasinal structures grew through segment linkage and probably interacted kinematically with basin‐margin faults. Basin‐margin faults constitute a coherent fault system that was conditioned by pre‐existing basement fabrics. Structural mapping, analysis of present‐day topography, and balanced cross sections indicate that positive inversion of extensional structures was focused along basin‐bounding faults, whereas intrabasinal faults remained unaffected and were passively transported by motion along the basin‐bounding faults. Thus, zones of maximum subsidence in extension accommodated maximum elevation in contraction, and former topographic highs remained as elevated areas. This documents the role of basin‐bounding faults as multiphased, long‐lived features conditioned by basement discontinuities. Inversion of basin‐bounding faults was more efficient in the southern than in the northern graben segment, possibly documenting the inheritance and pivotal role of fault‐displacement gradients. Our observations highlight similarities between inversion features in orogenic belts and intra‐plate basins, emphasizing the importance of the observed phenomena as predictive tools in the spatiotemporal analysis of inversion histories in orogens, as well as in hydrocarbon and mineral deposits exploration.  相似文献   

13.
Common basin models assume that the post‐rift tectonic evolution of most basins is usually associated with tectonic quiescence. However, tectonic inversion during the post‐rift phase has been proposed for several sedimentary basins worldwide, but how and why it happens is still a matter of debate, especially in intracontinental settings where the lithosphere is old and thick. Here, we use geological and geophysical data from the Rio do Peixe Basin in NE Brazil to show evidence that intracontinental sedimentary basins can be tectonically inverted by far‐field compressive stresses acting on pre‐existing weakness zones of lithospheric‐scale where stresses can concentrate and inversion can occur. Geomorphological and field data combined with seismic reflection, gravimetric and borehole data show that: (a) inversion occurred along two main Precambrian lithospheric‐scale shear zones, the Patos (E‐W trending) and Portalegre (NE‐SW trending), which had already been reactivated as basin‐bounding faults during the earlier rift stage; (b) post‐rift reactivation affected (mostly) the original master normal faults with the largest rift displacements, and locally produced new reverse faults; (c) during contraction, deformation was partitioned between fault reactivation and buckling of the incompetent sediment pushed against the hard basement; (d) all these signs of inversion have been observed in the field and can be demonstrated on seismic reflection profiles; and (e) combined gravimetric and seismic data show that the main structures of the basin were followed by an inversion. These data are consistent with the operation of WSW‐ENE horizontal maximum compressive stress as a result of combined pushes of the Mid‐Atlantic Ridge (towards the W) and the Andes (towards the E), responsible for the post‐rift oblique inversion of normal faults inherited from the rift phase and formed with vertical maximum compressive stress.  相似文献   

14.
Subduction zones provide direct insight into plate boundary deformation and by studying these areas we better understand tectonic processes and variability over time. We studied the structure of the offshore subduction zone system of the Pampean flat‐slab segment (ca. 29–33°S) of the Chilean margin using seismic and bathymetric constraints. Here, we related and analysed the structural styles of the offshore and onshore western fore‐arc. Overlying the acoustic top of the continental basement, two syn‐extensional seismic sequences were recognised and correlated with onshore geological units and the Valparaíso Forearc Basin seismic sequences: (SII) Pliocene‐Pleistocene and (SI) Miocene‐Pliocene (Late Cretaceous (?) to Miocene‐Pliocene) syn‐extensional sequences. These sequences are separated by an unconformity (i.e. Valparaíso Unconformity). Seismic reflection data reveal that the eastward dipping extensional system (EI) recognised at the upper slope can be extended to the middle slope and controlled the accumulation of the older seismic package (SI). The westward dipping extensional system (EII) is essentially restricted to the middle slope. Here, EII cuts the eastward dipping extensional system (EI), preferentially parallel to the inclination of the older sequences (SI), and controlled a series of middle slope basins which are filled by the Pliocene‐Pleistocene seismic sequence (SII). At the upper slope and in the western Coastal Cordillera, the SII sequence is controlled by eastward dipping faults (EII) which are the local reactivation of older extensional faults (EI). The tectonic boundary between the middle (eastern outermost forearc block) and upper continental slope (western coastal block) is a prominent system of trenchward dipping normal fault scarps (ca. 1 km offset) that resemble a major trenchward dipping extensional fault system. This prominent structural feature can be readily detected along the Chilean erosive margin as well as the two extensional sets (EI and EII). Evidence of slumping, thrusting, reactivated faults and mass transport deposits, were recognised in the slope domain and locally restricted to some eastern dipping faults. These features could be related to gravitational effects or slope deformation due to coseismic deformation. The regional inclination of the pre‐Pliocene sequences favoured the gravitational collapse of the outermost forearc block. We propose that the structural configuration of the study area is dominantly controlled by tectonic erosion as well as the uplift of the Coastal Cordillera, which is partially controlled by pre‐Pliocene architecture.  相似文献   

15.
Fluid migration pathways in the subsurface are heavily influenced by pre‐existing faults. Although studies of active fluid‐escape structures can provide insights into the relationships between faults and fluid flow, they cannot fully constrain the geometry of and controls on the contemporaneous subsurface fluid flow pathways. We use 3D seismic reflection data from offshore NW Australia to map 121 ancient hydrothermal vents, likely related to magmatic activity, and a normal fault array considered to form fluid pathways. The buried vents consist of craters up to 264 m deep, which host a mound of disaggregated sedimentary material up to 518 m thick. There is a correlation between vent alignment and underlying fault traces. Seismic‐stratigraphic observations and fault kinematic analyses reveal that the vents were emplaced on an intra‐Tithonian seabed in response to the explosive release of fluids hosted within the fault array. We speculate that during the Late Jurassic the convex‐upwards morphology of the upper tip‐lines of individual faults acted to channelize ascending fluids and control where fluid expulsion and vent formation occurred. This contribution highlights the usefulness of 3D seismic reflection data to constraining normal fault‐controlled subsurface fluid flow.  相似文献   

16.
The impact of a pre‐existing rift fabric on normal fault array evolution during a subsequent phase of lithospheric extension is investigated using 2‐D and 3‐D seismic reflection, and borehole data from the northern Horda Platform, Norwegian North Sea. Two fault populations are developed: (i) a population comprising relatively tall (>2 km), N‐S‐striking faults, which have >1.5 km of throw. These faults are up to 60 km long, penetrate down into crystalline basement and bound the eastern margins of 6–15 km wide half‐graben, which contain >3 km of pre‐Jurassic, likely Permo–Triassic, but possibly Devonian syn‐rift strata; and (ii) a population comprising vertically restricted (<1 km), NW‐SE‐striking faults, which are more closely spaced (0.5–5 km), have lower displacements (30–100 m) and not as long (2–10 km) as those in the N–S‐striking population. The NW‐SE‐striking population typically occurs between the N‐S‐striking population, and may terminate against or cross‐cut the larger structures. NW–SE‐striking faults do not bound pre‐Jurassic half‐graben and are largely restricted to the Jurassic‐to‐Cretaceous succession. Seismic‐stratigraphic observations, and the stratigraphic position of the fault tips in both fault populations, allow us to reconstruct the Late Jurassic‐to‐Early Cretaceous growth history of the northern Horda Platform fault array. We suggest the large, N‐S‐striking population was active during the Permo–Triassic and possibly earlier (Devonian?), before becoming inactive and buried during the Early and Middle Jurassic. After a period of relative tectonic quiescence, the N‐S‐striking, pre‐Jurassic fault population propagated through the Early‐Middle Jurassic cover and individual fault systems rapidly (within <10 Ma) established their maximum length in response to Late Jurassic extension. These fault systems became the dominant structures in the newly formed fault array and defined the locations of the main, Late Jurassic‐to‐Early Cretaceous, syn‐rift depocentres. Late Jurassic extension was also accommodated by broadly synchronous growth of the NW‐SE‐striking fault population; the eventual death of this population occurred in response to the localization of strain onto the N–S‐striking fault population. Our study demonstrates that the inheritance of a pre‐existing rift fabric can influence the geometry and growth of individual fault systems and the fault array as a whole. On the basis of observations made in this study, we present a conceptual model that highlights the influence of a pre‐existing rift fabric on fault array evolution in polyphase rifts.  相似文献   

17.
Recent studies of natural, multiphase rifts suggest that the presence of pre‐existing faults may strongly influence fault growth during later rift phases. These findings compare well with predictions from recent scaled analogue experiments that simulate multiphase, non‐coaxial extension. However, in natural rifts we only get to see the final result of multiphase rifting. We therefore do not get the chance to compare the effects of the same rift phase with and without pre‐existing structural heterogeneity, as we may in the controlled environment of a laboratory experiment. Here, we present a case study from the Lofoten Margin that provides a unique opportunity to compare normal fault growth with and without pre‐existing structural heterogeneity. Using seismic reflection and wellbore data, we demonstrate that the Ribban Basin formed during Late Jurassic to Early Cretaceous rifting. We also show that the rift fault network of the Ribban Basin lacks a pre‐existing (Permian‐Triassic) structural grain that underlies the neighbouring North Træna Basin that also formed during the Late Jurassic to Early Cretaceous. Being able to compare adjacent basins with similar histories but contrasting underlying structure allows us to study how pre‐existing normal faults influence rift geometry. We demonstrate that in Lofoten, the absence of pre‐existing normal faults produced collinear fault zones. Conversely, where pre‐existing faults are present, normal fault zones develop strong “zigzag” plan‐view geometries.  相似文献   

18.
The Southern Tail‐End Graben, Danish Central Graben, is characterized by a lateral variation in the thickness and mobility of pre‐rift Zechstein Supergroup evaporites, allowing investigation of how supra‐basement evaporite variability influences rift structural style and tectono‐stratigraphy. The study area is divided into two structural domains based on interpretations of the depositional thickness and mobility of the Zechstein Supergroup. Within each domain, we examine the overall basin morphology and the structural styles in the pre‐Zechstein and supra‐Zechstein (cover) units. Furthermore, integration of two‐way travel‐time (TWT)‐structure and ‐thickness maps allows fault activity and evaporite migration maps to be generated for pre‐ and syn‐rift stratal units within the two domains, permitting constraints to be placed on: (i) the timing of activity on pre‐Zechstein and cover faults and (ii) the onset, duration and migration direction of mobile evaporites. The northern domain is interpreted to be free from evaporite‐influence, and has developed in a manner typical of brittle‐only, basement‐involved rifts. Syn‐rift basins display classical half‐graben geometries bounded by thick‐skinned faults. In contrast, the southern domain is interpreted to be evaporite‐influenced, and cover structure reflects a southward increase in the thickness and mobility of the Zechstein Supergroup evaporites. Fault‐related and evaporite‐related folding is prominent in the southern domain, together with variable degrees of decoupling of sub‐Zechstein and cover fault and fold systems. The addition of mobile evaporites to the rift results in: (i) complex and spatially variable modes of tectono‐stratigraphic evolution; (ii) syn‐rift stratal geometries which are condensed above evaporite swells and over‐thickened in areas of withdrawal; (iii) compartmentalized syn‐rift depocentres; and (iv) masking of rift‐related megasequence boundaries. Through demonstrating these deviations from the characteristics of rifts free from evaporite influence, we highlight the first order control evaporites may exert upon rift structural style and the distribution and thicknesses of syn‐rift units.  相似文献   

19.
《Basin Research》2018,30(3):373-394
Continental breakup between Greenland and North America produced the small oceanic basins of the Labrador Sea and Baffin Bay, which are connected via the Davis Strait, a region mostly comprised of continental crust. This study contributes to the debate regarding the role of pre‐existing structures on rift development in this region using seismic reflection data from the Davis Strait data to produce a series of seismic surfaces, isochrons and a new offshore fault map from which three normal fault sets were identified as (i) NE‐SW, (ii) NNW‐SSE and (iii) NW‐SE. These results were then integrated with plate reconstructions and onshore structural data allowing us to build a two‐stage conceptual model for the offshore fault evolution in which basin formation was primarily controlled by rejuvenation of various types of pre‐existing structures. During the first phase of rifting between at least Chron 27 (ca. 62 Ma; Palaeocene), but potentially earlier, and Chron 24 (ca. 54 Ma; Eocene) faulting was primarily controlled by pre‐existing structures with oblique normal reactivation of both the NE‐SW and NW‐SE structural sets in addition to possible normal reactivation of the NNW‐SSE structural set. In the second rifting stage between Chron 24 (ca. 54 Ma; Eocene) and Chron 13 (ca. 35 Ma; Oligocene), the sinistral Ungava transform fault system developed due to the lateral offset between the Labrador Sea and Baffin Bay. This lateral offset was established in the first rift stage possibly due to the presence of the Nagssugtoqidian and Torngat terranes being less susceptible to rift propagation. Without the influence of pre‐existing structures the manifestation of deformation cannot be easily explained during either of the rifting phases. Although basement control diminished into the post‐rift, the syn‐rift basins from both rift stages continued to influence the location of sedimentation possibly due to differential compaction effects. Variable lithospheric strength through the rifting cycle may provide an explanation for the observed diminishing role of basement structures through time.  相似文献   

20.
The lateral propagation of faults and folds is known to be an important process during the development of mountain belts, but little is known about the manner in which along‐strike fault–fold growth is expressed in pre‐ and syntectonic (growth) strata. We use a coupled tectonic and stratigraphic model to investigate the along‐strike stratigraphic expression of fault‐related folds/uplifts that grow in both the transport and strike directions. We consider faults that propagate following a quadratic (nonself‐similar evolution) or linear (self‐similar evolution) scaling law, using different slip distributions per episode of fault propagation, under general background sedimentation. We find that the long‐strike geometry of pre‐ and syntectonic strata and the geometry of growth axial surfaces reflect the mode of fault propagation. The geometry of strata observed in the model is similar to that observed in natural contractional structures when: (1) the evolution of the fault is nonself‐similar, or (2) the fault grows as a result of thrust faulting events with similar displacements along strike that are terminated abruptly at the fault tips.  相似文献   

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