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1.
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2.
The complex development of the northern Crotone Basin, a forearc basin of the Calabrian Arc (Southern Italy), has been documented by sedimentological, stratigraphic and structural analyses. This Mediterranean‐type fault bounded basin consists of small depocentres commonly characterized by a mix of facies that grades from continental to shallow marine. The lower Pliocene infill of the Crotone Basin consists of offshore marls (Cavalieri Marl) that grade upwards into a shallow‐marine to continental succession up to 850 m thick (Zinga Formation). The succession is subdivided into three main stratal units: Zinga 1, Zinga 2, Zinga 3 bounded by major unconformities. The Zinga 1 stratal unit grades from the Cavalieri Marl to deltaic and shoreface deposits, the latter organized into several stacked progradational wedges that show spectacular thickness changes and progressive unconformities related to salt‐cored NE‐trending growth folds and listric normal faults. The Zinga 2 stratal unit records a progressive and moderate deepening of the area, marked by fluvial sedimentation at the base, followed by lagoonal deposits and by a stacking of mixed bioclastic and siliciclastic shoreface units, organized into metre‐scale high‐frequency cycles. Deposition was controlled by NE‐trending synsedimentary normal faults that dissected the basin into a series of half‐grabens. Hangingwall stratigraphic expansion was compensated by footwall condensed sedimentation. The extensional tectonic regime continued during sedimentation of the Zinga 3 stratal unit. Deposition confined within structural lows during a generalized transgressive phase led to local enhancement of tidal flows and development of sand‐wave trains. The tectonic setting testifies the generalized structural domain of a forearc region. The angular unconformity at the top of the Zinga 3 stratal unit is regional, and marks the activation of a large‐scale tectonic phase linked to strike‐slip movements.  相似文献   

3.
Extensional faults and folds exert a fundamental control on the location, thickness and partitioning of sedimentary deposits on rift basins. The connection between the mode of extensional fault reactivation, resulting fault shape and extensional fold growth is well‐established. The impact of folding on accommodation evolution and growth package architecture, however, has received little attention; particularly the role‐played by fault‐perpendicular (transverse) folding. We study a multiphase rift basin with km‐scale fault displacements using a large high‐quality 3D seismic data set from the Fingerdjupet Subbasin in the southwestern Barents Sea. We link growth package architecture to timing and mode of fault reactivation. Dip linkage of deep and shallow fault segments resulted in ramp‐flat‐ramp fault geometry, above which fault‐parallel fault‐bend folds developed. The folds limited the accommodation near their causal faults, leading to deposition within a fault‐bend synclinal growth basin further into the hangingwall. Continued fold growth led to truncation of strata near the crest of the fault‐bend anticline before shortcut faulting bypassed the ramp‐flat‐ramp structure and ended folding. Accommodation along the fault‐parallel axis is controlled by the transverse folds, the location and size of which depends on the degree of linkage in the fault network and the accumulated displacement on causal faults. We construct transverse fold trajectories by tracing transverse fold hinges through space and time to highlight the positions of maximum and minimum accommodation and potential sediment entry points to hangingwall growth basins. The length and shape of the constructed trajectories relate to the displacement on their parent faults, duration of fault activity, timing of transverse basin infill, fault linkage and strain localization. We emphasize that the considerable wavelength, amplitudes and potential periclinal geometry of extensional folds make them viable targets for CO2 storage or hydrocarbon exploration in rift basins.  相似文献   

4.
Established models indicate that, before being breached, relay zones along rift borders can evolve either by lengthening and rotating during progressive overlap of growing fault segments (isolated fault model), or, by simply rotating without lengthening before breaching (coherent fault model). The spatio‐temporal distribution of vertical motions in a relay zone can thus be used to distinguish fault growth mechanisms. Depositional relay zones that develop at sea level and accommodate both deposition on the ramp itself as well as transfer of sediments from the uplifting footwall into the hangingwall depocentres and provide the most complete record of vertical motions. We examine the development of a depositional relay ramp on the border of the active Corinth rift, Greece to reconstruct fault interaction in time and space using both onshore and offshore (2D seismic lines) data. The Akrata relay zone developed over a period of ca. 0.5 Myr since the Middle Pleistocene between the newly forming East Helike Fault (EHF) that propagated towards the older, more established Derveni Fault (DF). The relay zone captured the Krathis River, which deposited prograding Gilbert‐type deltas on the sub‐horizontal ramp. Successive oblique faults record progressive linkage and basinward migration of accommodation along the ramp axis, whereas marine terraces record diachronous uplift in their footwalls. Although early linkage of the relay zone occurs, continuous propagation and linkage of the EHF onto the static DF is recorded before final beaching. Rotation on forced folds above the upward and laterally propagating normal faults at the borders of the relay zone represents the ramp hinges. The Akrata relay zone cannot be compared directly to a simple fault growth model because (1) the relay zone connects two fault segments of different generations; (2) multiple linkages during propagation was facilitated by the presence of pre‐existing crustal structures, inherited from the Hellenide fold and thrust belt. The linkage of the EHF to the DF contributed to the westward and northward propagation of the southern rift border.  相似文献   

5.
Abstract Low‐angle detachment faults and thrust‐sheet top basins are common features in foreland basins. However, in stratigraphic analysis their influence on sequence architecture is commonly neglected. Usually, only eustatic sea level and changing flexural subsidence are accounted for, and when deformation is considered, the emphasis is on the generation of local thrust‐flank unconformities. This study analyses the effects of detachment angle and repetitive detachment activation on stratigraphic stacking patterns in a large thrust‐sheet top basin by applying a three‐dimensional numerical model. Model experiments show that displacement over low‐angle faults (2–6°) at moderate rates (～5.0 m kyr?1) results in a vertical uplift component sufficient to counteract the background flexural subsidence rate. Consequently, the basin‐wide accommodation space is reduced, fluvio‐deltaic systems carried by the thrust‐sheet prograde and part of the sediment supply is spilled over towards adjacent basins. The intensity of the forced regression and the interconnectedness of fluvial sheet sandstones increases with the dip angle of the detachment fault or rate of displacement. In addition, the delta plain is susceptible to the formation of incised valleys during eustatic falls because these events are less compensated by regional flexural subsidence, than they would be in the absence of fault displacement.  相似文献   

6.
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   

7.
The outer Adriatic zones of the central Apennines (Italy) provide good conditions for analysing geometry and kinematics of the earliest normal faults, superposed onto the thrust belt. During the latest stages of thrusting onto the Adriatic foreland (late Pliocene–early Pleistocene), the outermost imbricates of the thrust belt were subjected to normal faulting, coeval with differential uplift. Crosscutting normal faults get younger towards the foreland, thus the easternmost normal faults record the latest stages of fault propagation and growth. The Caramanico fault, on the western flank of Mt. Maiella, is the largest outcropping normal fault of the outer zones. This high‐angle fault (dip > 70°) has cumulative offsets ≤ €4.2 km, and propagated with slip rates of 2.6 mm/year in a short time interval (≤ 1.6 Ma), concomitant with intense uplift of Mt. Maiella. In contrast with normal faults in a more internal position, the Caramanico fault maintains a high‐angle planar geometry, and does not reach the major basal detachment of the thrust belt. Thus the fault did not cause large extensional displacements; its major role was rather to accommodate ongoing components of vertical uplift of the overthickened thrust wedge. Downfaulting of the thrust belt on the western flank of Mt. Maiella represents the youngest end member of the same processes that have operated since 11 Ma in the Tyrrhenian hinterland, where large extensional strains and crustal thinning of the orogenic belt were achieved by long‐lasting activity of listric normal faults detached at lower crustal depths.  相似文献   

8.
Three successive zones of fault‐related folds disrupt the proximal part of the northern Tian Shan foreland in NW China. A new magnetostratigraphy of the Taxi He section on the north limb of the Tugulu anticline in the middle deformed zone clarifies the chronology of both tectonic deformation and depositional evolution of this collisional mountain belt. Our ～1200‐m‐thick section encompasses the upper Cenozoic terrigenous sequence within which ～300 sampling horizons yield an age span of ～8–2 Ma. Although the basal age in the Taxi He section of the Xiyu conglomerate (often cited as an indicator of initial deformation) is ～2.1 Ma, much earlier growth of the Tugulu anticline is inferred from growth strata dated at ～6.0 Ma. Folding of Neogene strata and angular unconformities in anticlines in the more proximal and distal deformed zones indicate deformation during Miocene and Early Pleistocene times, respectively. In the Taxi He area, sediment‐accumulation rates significantly accelerate at ～4 Ma, apparently in response to encroaching thrust loads. Together, growth strata, angular unconformities, and sediment‐accumulation rates document the northward migration of tectonic deformation into the northern Tian Shan foreland basin during the late Cenozoic. A progradational alluvial–lacustrine system associated with this northward progression is subdivided into two facies associations at Tugulu: a shallow lacustrine environment before ～5.9 Ma and an alluvial fan environment subsequently. The lithofacies progradation encompasses the time‐transgressive Xiyu conglomerate deposits, which should only be recognized as a lithostratigraphic unit. Along the length of the foreland, the locus of maximum shortening shifts between the medial and proximal zones of folding, whereas the total shortening across the foreland remains quite homogeneous along strike, suggesting spatially steady tectonic forcing since late Miocene times.  相似文献   

9.
The active growth of a fault-and-thrust belt in frontal zones of Himalaya is a prominent topographical feature, extending 2500 km from Assam to Pakistan. In this paper, kinematical analysis of frontal anticlines and spatial mapping of active faults based on geomorphological features such as drainage pattern development, fault scarps and uplifted Quaternary alluvial fans are presented. We analyse the geomorphic and hydrographic expressions of the Chandigarh and the Janauri active anticlines in the NW India Siwaliks. To investigate the morphological scenario during the folding process, we used spatial imagery, geomorphometric parameters extracted from digital elevation models and fieldwork. Folding between the Beas and Sutlej Rivers gives clear geomorphological evidence of recent fold growth, presumably driven by movements of blind thrust faults. Structural style within the Janauri and Chandigarh anticlines is highly variable (fault-propagation folds, pop-up structures and transfer faults). The approach presented here involves analysis of topography and drainage incision of selected landforms to detect growth of active anticlines and transfer faults. Landforms that indicate active folding above a southwest-dipping frontal thrust and a northeast-dipping back-thrust are described. Along-strike differences in ridge morphology are measured to describe the interaction of river channel patterns with folds and thrust faults and to define history of anticline growth. The evolution of the apparently continuous Janauri ridge has occurred by the coalescence of independent segments growing towards each other. By contrast, systematic drainage basin asymmetry shows that the Chandigarh anticline ridge has propagated laterally from NW to SE.  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.
We report on new stratigraphic, palaeomagnetic and anisotropy of magnetic susceptibility (AMS) results from the Amantea basin, located on‐shore along the Tyrrhenian coast of the Calabrian Arc (Italy). The Miocene Amantea Basin formed on the top of a brittlely extended upper plate, separated from a blueschist lower plate by a low‐angle top‐to‐the‐west extensional detachment fault. The stratigraphic architecture of the basin is mainly controlled by the geometry of the detachment fault and is organized in several depositional sequences, separated by major unconformities. The first sequence (DS1) directly overlaps the basement units, and is constituted by Serravallian coarse‐grained conglomerates and sandstones. The upper boundary of this sequence is a major angular unconformity locally marked by a thick palaeosol (type 1 sequence boundary). The second depositional sequence DS2 (middle Tortonian‐early Messinian) is mainly formed by conglomerates, passing upwards to calcarenites, sandstones, claystones and diatomites. Finally, Messinian limestones and evaporites form the third depositional sequence (DS3). Our new biostratigraphic data on the Neogene deposits of the Amantea basin indicate a hiatus of 3 Ma separating sequences DS1 and DS2. The structural architecture of the basin is characterized by faulted homoclines, generally westward dipping, dissected by eastward dipping normal faults. Strike‐slip faults are also present along the margins of the intrabasinal structural highs. Several episodes of syn‐depositional tectonic activity are marked by well‐exposed progressive unconformities, folds and capped normal faults. Three main stages of extensional tectonics affected the area during Neogene‐Quaternary times: (1) Serravallian low‐angle normal faulting; (2) middle Tortonian high‐angle syn‐sedimentary normal faulting; (3) Messinian‐Quaternary high‐angle normal faulting. Extensional tectonics controlled the exhumation of high‐P/low‐T metamorphic rocks and later the foundering of the Amantea basin, with a constant WNW‐ESE stretching direction (present‐day coordinates), defined by means of structural analyses and by AMS data. Palaeomagnetic analyses performed mainly on the claystone deposits of DS1 show a post‐Serravallian clockwise rotation of the Amantea basin. The data presented in this paper constrain better the overall timing, structure and kinematics of the early stages of extensional tectonics of the southern Tyrrhenian Sea. In particular, extensional basins in the southern Tyrrhenian Sea opened during Serravallian and evolved during late Miocene. These data confirm that, at that time, the Amantea basin represented the conjugate extensional margin of the Sardinian border, and that it later drifted south‐eastward and rotated clockwise as a part of the Calabria‐Peloritani terrane.  相似文献   

12.
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   

13.
The Dzereg Basin is an actively evolving intracontinental basin in the Altai region of western Mongolia. The basin is sandwiched between two transpressional ranges, which occur at the termination zones of two regional‐scale dextral strike‐slip fault systems. The basin contains distinct Upper Mesozoic and Cenozoic stratigraphic sequences that are separated by an angular unconformity, which represents a regionally correlative peneplanation surface. Mesozoic strata are characterized by northwest and south–southeast‐derived thick clast‐supported conglomerates (Jurassic) overlain by fine‐grained lacustrine and alluvial deposits containing few fluvial channels (Cretaceous). Cenozoic deposits consist of dominantly alluvial fan and fluvial sediments shed from adjacent mountain ranges during the Oligocene–Holocene. The basin is still receiving sediment today, but is actively deforming and closing. Outwardly propagating thrust faults bound the ranges, whereas within the basin, active folding and thrusting occurs within two marginal deforming belts. Consequently, active fan deposition has shifted towards the basin centre with time, and previously deposited sediment has been uplifted, eroded and redeposited, leading to complex facies architecture. The geometry of folds and faults within the basin and the distribution of Mesozoic sediments suggest that the basin formed as a series of extensional half‐grabens in the Jurassic–Cretaceous which have been transpressionally reactivated by normal fault inversion in the Tertiary. Other clastic basins in the region may therefore also be inherited Mesozoic depocentres. The Dzereg Basin is a world class laboratory for studying competing processes of uplift, deformation, erosion, sedimentation and depocentre migration in an actively forming intracontinental transpressional basin.  相似文献   

14.
Extensional fault‐propagation folds are now recognised as being an important part of basin structure and development. They have a very distinctive expression, often presenting an upward‐widening monocline, which is subsequently breached by an underlying, propagating fault. Growth strata, if present, are thought to provide a crucial insight into the manner in which such structures grow in space and time. However, interpreting their stratigraphic signal is neither straightforward nor unique. Both analogue and numerical models can provide some insight into fold growth. In particular, the trishear kinematic model has been widely adopted to explain many aspects of the evolution and geometry of such fault‐propagation folds. However, in some cases the materials/rheologies used to represent the cover do not reproduce the key geometric/stratigraphic features of such folds seen in nature. This appears to arise from such studies not addressing adequately the very heterogenous mechanical stratigraphy seen in many sedimentary covers. In particular, flexural slip between beds/layers is often not explicitly modelled but, paradoxically, it appears to be an important deformation mechanism operative in such settings. Here, I present a 2D discrete element model of extensional fault‐propagation folding which explicitly includes flexural slip between predefined sedimentary units or layers in the cover. The model also includes growth strata and shows how they may reflect the various evolutionary stages of fold and fault growth. When flexural slip is included in the modelling scheme, the resultant breached monoclines and their growth strata are strikingly similar to some of those seen in nature. Results are also compared with those obtained using simple, homogeneous, frictional‐cohesive and elastic cover materials. Both un‐lithified and lithified growth strata are considered and clearly show that, rather than just being passive recorders of structural evolution, growth strata can themselves have an important effect on fault‐related fold growth. Implications for the evolution of and strain within, the resultant growth structures are discussed. A final focus of this study is the relationship that trishear might have with the upward‐widening zone of flexural slip activation away from a fault tip singularity.  相似文献   

15.
In submarine settings, the growth of structurally influenced topography can play a decisive role in controlling the routing of sediments from shelf-edge to deep water, and can determine depositional architectures and sediment characteristics. Here we use well-constrained examples from the deep water Niger Delta, where gravity-driven deformation has resulted in the development of a large fold and thrust belt, to illustrate how spatial and temporal variations in the rate of deformation have controlled the nature and locus of contrasting depositional styles. Published work in the study area using 3D seismic data has quantified the growth history of the thrust-related folds at multiple locations using line-length-balancing, enabling cumulative strain for individual structures over time and along-strike to be obtained. We integrate this information with seismic interpretation and facies analysis, focusing on the interval of maximum deformation (15 to 3.7 Ma), where maximum strain rates reached 7%/Ma. Within this interval, we observe a vertical change in depositional architecture where: (1) leveed-confined and linear channels pass upward in to (2) ponded lobes with erosionally confined channels and finally (3) channelised sheets. Our analysis demonstrate that this change is tectonically induced and diachronous across the fault array, and we characterise the extent to which structural growth controls both the distribution and the architecture of the turbidite deposits in such settings. In particular, we show that leveed-confined channels exist when they can exploit strain minima between growing faults or at their lateral tips. Conversely, as a result of fault linkage and increased strain rates submarine channels become erosional and may be forced to cross folds at their strain maxima (crests), where their pathways are influenced by across-strike variations in shortening for individual structures. Our results enable us to propose new conceptual models of submarine channel deposition in structurally complex margins, and provide new insights into the magnitude of fault interaction needed to alter depositional style from leveed to erosionally confined channels, or to deflect seabed systems around growing structures.  相似文献   

16.
The growth, interaction and controls on normal fault systems developed within stacked delta systems at extensional delta‐top settings have not been extensively examined. We aim to analyse the kinematic, spatial and temporal growth of a Cretaceous aged, thin‐skinned, listric fault system in order to further the understanding of how gravity‐driven fault segments and fault systems develop and interact at an extensional delta‐top setting. Furthermore, we aim to explore the influence of a pre‐existing structural framework on the development of gravity‐driven normal faults through the examination of two overlapping, spatially and temporally distinct delta systems. To do this, we use three‐dimensional (3D) seismic reflection data from the central Ceduna Sub‐basin, offshore southern Australia. The seismic reflection data images a Cenomanian‐Santonian fault system, and a post‐Santonian fault system, which are dip‐linked through an intervening Turonian‐early Campanian section. Both of these fault systems contain four hard‐linked strike assemblages oriented NW–SE (127–307), each composed of 13 major fault segments. The Cenomanian‐Santonian fault system detaches at the base of a shale interval of late Albian age, and is characterised by kilometre‐scale growth faults in the Cenomanian‐Sanontian interval. The post‐Santonian fault system nucleated in vertical isolation from the Cenomanian‐Santonian fault system. This is evident through displacement minima observed at Turonian‐early Campanian levels, which is indicative of vertical segmentation and eventual hard dip‐linkage. Our analysis constrains fault growth into four major evolutionary stages: (1) early Cenomanian nucleation and growth of fault segments, resulting from gravitational instability, and with faults detaching on the lower Albian interval; (2) Santonian cessation of growth for the majority of faults; (3) erosional truncation of fault upper tips coincident with the continental breakup of Australia and Antarctica (ca. 83 Ma); (4) Campanian‐Maastrichtian reactivation of the underlying Cenomanian‐Santonian fault system, inducing the nucleation, growth and consequential dip‐linkage of the post‐Santonian fault system with the underlying fault system. Our results highlight the along‐strike linkage of fault segments and the interaction through dip‐linkage and fault reactivation, between two overlapping, spatially and temporally independent delta systems of Cenomanian and late Santonian‐Maastrichtian age in the frontier Ceduna Sub‐Basin. This study has implications regarding the growth of normal fault assemblages, through vertical and lateral segment linkage, for other stacked delta systems (such as the Gulf of Mexico) where upper delta systems develop over a pre‐existing structural framework.  相似文献   

17.
Geologic evidence across orogenic plateau margins enables the discrimination of the relative contributions of orogenic, epeirogenic and/or climatic processes that lead to growth and maintenance of those plateaus and their margins. Here, we discuss the mode of formation of the southern margin of the Central Anatolian Plateau (SCAP) and evaluate its time of formation using fieldwork in the onshore and seismic reflection data in the offshore. In the onshore, uplifted Miocene rocks in a dip‐slope topography show monocline flexure over >100 km, km‐scale asymmetric folds verging south, and outcrop‐scale syn‐sedimentary reverse faults. On the Turkish shelf, vertical faults transect the basal latest Messinian of a 10 km fold where on‐structure syntectonic wedges and synsedimentary unconformities indicate pre‐Pliocene uplift and erosion, followed by Pliocene and younger deformation. Collectively, Miocene rocks delineate a flexural monocline at plateau margin scale that is expressed along our on‐offshore sections as a kink‐band fold with a steep flank 20–25 km long. In these reconstructed sections, we estimate a relative vertical displacement of 3.8 km at rates of ca. 0.5 mm/y, and horizontal shortening values <1 %. We use this evidence together with our observations of shortening at outcrop, basin, plateau‐margin and forearc‐system scales to infer that the SCAP forms as a monoclinal flexure to accommodate deep‐seated thickening and shortening since >5 Ma, and to contextualize the plateau margin as the forearc high of the Cyprus subduction system.  相似文献   

18.
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   

19.
Well-preserved, actively deforming folds in the Tien Shan of Kyrgyzstan provide a natural laboratory for the study of the evolution of thrust-related folds. The uplifted limbs of these folds comprise weakly indurated Cenozoic strata that mantle well-lithified Palaeozoic bedrock. Their contact is a regionally extensive unconformity that provides a persistent and readily traceable marker horizon. Based on the deformation of this marker, preserved fold geometries support simple geometric models for along-strike gradients in fold amplitude and displacement along the underlying faults, linkage among multiple structures, transfer of displacement among folds and evolution of the folds as geomorphic entities. Subsequent to initial uplift and warping of the unconformity surface, steeply dipping reverse faults cut the forelimbs of many of these folds. Wind gaps, water gaps, recent faulting and progressive stripping of the more readily eroded Cenozoic strata indicate the ongoing lateral propagation and vertical growth of fault-related folds. The defeat of formerly antecedent rivers coincides in several places with marked increases in erosional resistance where their incising channels first encountered Palaeozoic bedrock. Persistent dip angles on the backlimbs of folds indicate strikingly uniform geometries of the underlying faults as they propagate both laterally and vertically through the crust. Deformation switches irregularly forward and backward in both time and space among multiple active faults and folds with no systematic pattern to the migration of deformation. This distributed deformation appears characteristic of the entire Kyrgyz Tien Shan.  相似文献   

20.
Transtensional basins are sparsely described in the literature compared with other basin types. The oblique‐divergent plate boundary in the southern Gulf of California has many transtensional basins: we have studied those on San Jose island and two other transtensional basins in the region. One major type of transtensional basin common in the southern Gulf of California region is a fault‐termination basin formed where normal faults splay off of strike‐slip faults. These basins suggest a model for transtensional fault‐termination basins that includes traits that show a hybrid nature between classic rift and strike‐slip (pull‐apart) basins. The traits include combinations of oblique, strike‐slip and normal faults with common steps and bends, buttress unconformities between the fault steps and beyond the ends of faults, a common facies pattern of terrestrial strata changing upward and away from the faults into marine strata, small fault blocks within the basin that result in complex lateral facies relations, common Gilbert deltas, dramatic termination of the margin of the basin by means of fault reorganization and boundary faults dying and an overall short basin history (few million years). Similar transtensional fault‐termination basins are present in Death Valley and other parts of the Eastern California shear zone of the western United States, northern Aegean Sea and along ancient strike‐slip faults.  相似文献   

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