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1.
Tectonic inversion models predict that stratigraphic thickening and local facies patterns adjacent to reactivated fault systems should record at least two phases of basin development: (1) initial extension‐related subsidence and (2) subsequent shortening‐induced uplift. In the central Peloncillo Mountains of southwestern New Mexico, thickness trends, distribution, and provenance of two major stratigraphic intervals on opposite sides of a northwest‐striking reverse fault preserve a record of Early Cretaceous normal displacement and latest Cretaceous–Paleogene reverse displacement along the fault. The Aptian–Albian Bisbee Group thickens by a factor of three from the footwall to the hanging‐wall block, and the Late Cretaceous?–Eocene Bobcat Hill Formation is preserved only in the footwall block. An initial episode of normal faulting resulted in thickening of upper Aptian–middle Albian, mixed siliciclastic and carbonate deposits and an up section change from coarse‐grained deltas to shallow‐marine depositional conditions. A second episode of normal faulting caused abrupt thickening of upper Albian, quartzose coastal‐plain deposits across the fault. These faulting episodes record two events of extension that affected the northern rift shoulder of the Bisbee basin. The third faulting episode was oblique‐slip, reverse reactivation of the fault and other related, former normal faults. Alluvial and pyroclastic deposits of the Bobcat Hill Formation record inversion of the Bisbee basin and development of an intermontane basin directly adjacent to the former rift basin. Inversion was coeval with latest Cretaceous–Paleogene shortening and magmatism. This offset history offers significant insight into extensional basin tectonics in the Early Cretaceous and permits rejection of models of long‐term Mesozoic shortening and orogen migration during the Cretaceous. This paper also illustrates how episodes of fault reactivation modify, in very short distances (<10 km), regional patterns of subsidence, the distribution of sediment‐source areas, and sedimentary depositional systems.  相似文献   

2.
《Basin Research》2018,30(4):587-612
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3.
Rift basin tectono‐stratigraphic models indicate that normal fault growth controls the sedimentology and stratigraphic architecture of syn‐rift deposits. However, such models have rarely been tested by observations from natural examples and thus remain largely conceptual. In this study we integrate 3D seismic reflection, and biostratigraphically constrained core and wireline log data from the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway to test rift basin tectono‐stratigraphic models. The geometry of the basin‐bounding fault and its hangingwall, and the syn‐rift stratal architecture, vary along strike. The fault is planar along a much of its length, bounding a half‐graben containing a faultward‐thickening syn‐rift wedge. Locally, however, the fault has a ramp‐flat‐ramp geometry, with the hangingwall defined by a fault‐parallel anticline‐syncline pair. Here, an unusual bipartite syn‐rift architecture is observed, comprising a lower faultward‐expanding and an upper faultward‐thinning wedge. Fine‐grained basinfloor deposits dominate the syn‐rift succession, although isolated coarse clastics occur. The spatial and temporal distribution of these coarse clastics is complex due to syn‐depositional movement on the Vingleia Fault Complex. High rates of accommodation generation in the fault hangingwall led to aggradational stacking of fan deltas that rapidly (<5 km) pinch out basinward into offshore mudstone. In the south of the basin, rapid strain localization meant that relay ramps were short‐lived and did not represent major, long‐lived sediment entry points. In contrast, in the north, strain localization occurred later in the rift event, thus progradational shorefaces developed and persisted for a relatively long time in relay ramps developed between unlinked fault segments. The footwall of the Vingleia Fault Complex was characterized by relatively low rates of accommodation generation, with relatively thin, progradational hangingwall shorelines developed downdip of the fault block apex, sometime after the onset of sediment supply to the hangingwall. We show that rift basin tectono‐stratigraphic models need modifying to take into account along‐strike variability in fault structure and basin physiography, and the timing and style of syn‐rift sediment dispersal and facies, in both hangingwall and footwall locations.  相似文献   

4.
This paper presents data on the sedimentation processes and basin-fill architecture in an incipient submarine intrabasinal graben, the Strava graben. The Strava graben is a relatively small intrabasinal structure about 15 km long and 3 km wide formed some time during the late Pleistocene. It connects the Alkyonidhes basin to the Corinth basin, in the Aegean back arc, which is characterized by fast rates of extension and intensive seismicity. Analysis and interpretation of high-resolution 3.5-kHz and sparker profiles together with sonar imagery have shown that gravity-driven sediment transport, triggered by earthquakes, is the dominant sedimentation process and that this sediment forms the vast bulk of the basin-fill. The sediment deposited in the Strava graben is derived from the uplifted footwall blocks bounding the graben and is transported to the basin initially as liquefied flows, some of which may progressively evolve to turbidity flows. The deposits of the liquefied flows have accumulated in the graben floor as aggradational stacks, consisting of sheet-like, low-relief lobes, forming base of slope aprons that are fed by multiple sediment sources along active faults. In addition to the lateral (footwall-derived) sediment transport there is also a gravity-controlled axial transport. The axial transport has formed a depositional system in the down-dip termination of the Strava graben, where it enters the Corinth basin. The axial depositional system grows outwards and upwards and consists of liquefied flow depositional lobes which are separated by turbidites. The sedimentation transport processes and basin infilling style described for the Strava graben can be used as a predictive model for the early synrift stage of ancient submarine intrabasinal structures, in which the major sediment source area is the bounding fault scarps and not drainage basins in the hinterland.  相似文献   

5.
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   

6.
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   

7.
The Barmer Basin is a poorly understood rift basin in Rajasthan, northwest India. Exposures in the Sarnoo Hills, situated along the central eastern rift margin of the Barmer Basin, reveal a sedimentary succession that accumulated prior to the main Barmer Basin rift event, and a rift‐oblique fault network that displays unusual geometries and characteristics. Here, we present a comprehensive study of Lower Cretaceous sedimentology on the basin margin, along with a detailed investigation of rift‐oblique faults that are exposed nowhere else in the region and provide critical insights into Barmer Basin evolution. Lower Cretaceous sediments were deposited within a rapidly subsiding alluvial plain fluvial system. Subsequent to deposition, the evolving Sarnoo Hills fault network was affected by structural inheritance during an early, previously unrecognised, rift‐oblique extensional event attributed to transtension between India and Madagascar, and formed a juvenile fault network within the immediate rift‐margin footwall. Ghaggar‐Hakra Formation deposition may have been triggered by early rifting which tectonically destabilised the Marwar Craton prior to the main northeast–southwest Barmer Basin rift event. The identification of early rifting in the Barmer Basin demonstrates that regional extension and the associated rift systems were established throughout northwest India prior to the main phase of Deccan eruptions. Inheritance of early oblique fault systems within the evolving Barmer Basin provides a robust explanation for poorly understood structural complications interpreted in the subsurface throughout the rift. Critically, the presence of syn‐rift sedimentary successions within older oblique rift systems obscured beneath the present‐day Barmer Basin has significant implications for hydrocarbon exploration.  相似文献   

8.
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   

9.
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   

10.
Quantifying the Cenozoic growth of high topography in the Indo‐Asian collision zone remains challenging, due in part to significant shortening that occurred within Eurasia before collision. A growing body of evidence suggests that regions far removed from the suture zone experienced deformation before and during the early phases of Himalayan orogenesis. In the present‐day north‐eastern Tibetan Plateau, widespread deposits of Cretaceous sediment attest to significant basin formation; however, the tectonic setting of these basins remains enigmatic. We present a study of a regionally extensive network of sedimentary basins that are spatially associated with a system of SE‐vergent thrust faults and are now exposed in the high ranges of the north‐eastern corner of the Tibetan Plateau. We focus on a particularly well‐exposed basin, located ～20 km north of the Kunlun fault in the Anyemaqen Shan. The basin is filled by ～900 m of alluvial sediments that become finer‐grained away from the basin‐bounding fault. Additionally, beds in the proximal footwall of the basin‐bounding fault exhibit progressive, up‐section shallowing and several intraformational unconformities which can be traced into correlative conformities in the distal part of the basin. The observations show sediment accumulated in the basin during fault motion. Regional constraints on the timing of sediment deposition are provided by both fossil assemblages from the Early Cretaceous, and by K–Ar dating of volcanic rocks that floor and cross‐cut sedimentary fill. We argue that during the Cretaceous, the interior NE Tibetan Plateau experienced NW–SE contractional deformation similar to that documented throughout the Qinling–Dabie orogen to the east. The Songpan‐Ganzi terrane apparently marked the southern limit of this deformation, such that it may have been a relatively rigid block in the Tibetan lithosphere, separating regions experiencing deformation north of the convergent Tethyan margin from regions deforming inboard of the east Asian margin.  相似文献   

11.
We describe the tectono‐sedimentary evolution of a Middle Jurassic, rift‐related supra‐detachment basin of the ancient Alpine Tethys margin exposed in the Central Alps (SE Switzerland). Based on pre‐Alpine restoration, we demonstrate that the rift basin developed over a detachment system that is traced over more than 40 km from thinned continental crust to exhumed mantle. The detachment faults are overlain by extensional allochthons consisting of upper crustal rocks and pre‐rift sediments up to several kilometres long and several hundreds of metres thick, compartmentalizing the distal margin into sub‐basins. We mapped and restored one of these sub‐basins, the Samedan Basin. It consists of a V‐shape geometry in map view, which is confined by extensional allochthons and floored by a detachment fault. It can be restored over a minimum distance of 11 km along and about 4 km perpendicular to the basin axis. Its sedimentary infill can be subdivided into basal (initial), intermediate (widening) and top (post‐tectonic) facies tracts. These tracts document (1) formation of the basin initially bounded by high‐angle faults and developing into low‐angle detachment faults, (2) widening of the basin and (3) migration of deformation further outboard. The basal facies tract is made of locally derived, poorly sorted gravity flow deposits that show a progressive change from hangingwall to footwall‐derived lithologies. Upsection the sediments develop into turbidity current deposits that show retrogradation (intermediate facies tract) and starvation of the sedimentary system (post‐tectonic facies tract). On the scale of the distal margin, the syn‐tectonic record documents a thinning‐ and fining‐upward sequence related to the back stepping of the tectonically derived sediment source, progressive starvation of the sedimentary system and migration of deformation resulting in exhumation and progressive delamination of the thinned crust during final rifting. This study provides valuable insights into the tectono‐sedimentary evolution and stratigraphic architecture of a supra‐detachment basin formed over hyper‐extended crust.  相似文献   

12.
Models to explain alluvial system development in rift settings commonly depict fans that are sourced directly from catchments formed in newly uplifted footwalls, which leads to the development of steep-sided talus-cone fans in the actively subsiding basin depocentre. The impact of basin evolution on antecedent drainage networks orientated close to perpendicular to a rift axis, and flowing over the developing hangingwall dip slope, remains relatively poorly understood. The aim of this study is to better understand the responses to rift margin uplift and subsequent intrabasinal fault development in determining sedimentation patterns in alluvial deposits of a major antecedent drainage system. Field-acquired data from a coarse-grained alluvial syn-rift succession in the western Gulf of Corinth, Greece (sedimentological logging and mapping) has allowed analysis of the spatial distribution of facies associations, stratigraphic architectural elements and patterns of palaeoflow. During the earliest rifting phase, newly uplifted footwalls redirected a previously established fluvial system with predominantly southward drainage. Footwall uplift on the southern basin margin at an initially relatively slow rate led to the development of an overfilled basin, within which an alluvial fan prograded to the south-west, south and south-east over a hangingwall dip slope. Deposition of the alluvial system sourced from the north coincided with the establishment of small-scale alluvial fans sourced from the newly uplifted footwall in the south. Deposits of non-cohesive debris flows close to the proposed hangingwall fan apex pass gradationally downstream into predominantly bedload conglomerate deposits indicative of sedimentation via hyperconcentrated flows laden with sand- and silt-grade sediment. Subsequent normal faulting in the hangingwall resulted in the establishment of further barriers to stream drainage, blocking flow routes to the south. This culminated in the termination of sediment supply to the basin depocentre from the north, and the onset of underfilled basin conditions as signified by an associated lacustrine transgression. The evolution of the fluvial system described in this study records transitions between three possible end-member types of interaction between active rifting and antecedent drainage systems: (a) erosion through an uplifted footwall, (b) drainage diversion away from an uplifted footwall and (c) deposition over the hangingwall dip slope. The orientation of antecedent drainage pathways at a high angle to the trend of a developing rift axis, replete with intrabasinal faulting, exerts a primary control on the timing and location of development of overfilled and underfilled basin states in evolving depocentres.  相似文献   

13.
A new subtype of Gilbert-type fan deltas, ‘the trapezoidal fan delta’, characterized by the absence of bottomset deposits, is recognized in the south-western active margins of the Corinth rift in central Greece. They are formed adjacent to master extensional listric faults and developed by progradation either onto a subaqueous basin escarpment or across a subaerial platform where alluvial fans have accumulated. Simultaneously with master fault activity, displacements on counter faults along intrabasinal basement highs produced fan delta foreset deposits. Furthermore, footwall imbrication and uplift along the listric faults, as well as transfer fault displacement, have strongly influenced the pattern of fan delta sedimentation.  相似文献   

14.
The Celtic Sea basins lie on the continental shelf between Ireland and northwest France and consist of a series of ENE–WSW trending elongate basins that extend from St George’s Channel Basin in the east to the Fastnet Basin in the west. The basins, which contain Triassic to Neogene stratigraphic sequences, evolved through a complex geological history that includes multiple Mesozoic rift stages and later Cenozoic inversion. The Mizen Basin represents the NW termination of the Celtic Sea basins and consists of two NE–SW-trending half-grabens developed as a result of the reactivation of Palaeozoic (Caledonian, Lower Carboniferous and Variscan) faults. The faults bounding the Mizen Basin were active as normal faults from Early Triassic to Late Cretaceous times. Most of the fault displacement took place during Berriasian to Hauterivian (Early Cretaceous) times, with a NW–SE direction of extension. A later phase of Aptian to Cenomanian (Early to Late Cretaceous) N–S-oriented extension gave rise to E–W-striking minor normal faults and reactivation of the pre-existing basin bounding faults that propagated upwards as left-stepping arrays of segmented normal faults. In common with most of the Celtic Sea basins, the Mizen Basin experienced a period of major erosion, attributed to tectonic uplift, during the Paleocene. Approximately N–S Alpine regional compression-causing basin inversion is dated as Middle Eocene to Miocene by a well-preserved syn-inversion stratigraphy. Reverse reactivation of the basin bounding faults was broadly synchronous with the formation of a set of near-orthogonal NW–SE dextral strike-slip faults so that compression was partitioned onto two fault sets, the geometrical configuration of which is partly inherited from Palaeozoic basement structure. The segmented character of the fault forming the southern boundary of the Mizen Basin was preserved during Alpine inversion so that Cenozoic reverse displacement distribution on syn-inversion horizons mirrors the earlier extensional displacements. Segmentation of normal faults therefore controls the geometry and location of inversion structures, including inversion anticlines and the back rotation of earlier relay ramps.  相似文献   

15.
We present a new tectonic map focused upon the extensional style accompanying the formation of the Tyrrhenian back‐arc basin. Our basin‐wide analysis synthetizes the interpretation of vintage multichannel and single‐channel seismic profiles, integrated with modern seismic images, P‐wave velocity models, and high‐resolution morpho‐bathymetric data. Four distinct evolutionary phases of the Tyrrhenian back‐arc basin opening are further constrained, redefining the initial opening to Langhian/Serravallian time. Listric and planar normal faults and their conjugates bound a series of horst and graben, half‐graben and triangular basins. Distribution of extensional faults, active throughout the basin since Middle Miocene, allows us to define an arrangement of faults in the northern/central Tyrrhenian mainly related to a pure shear which evolved to a simple shear opening. At depth, faults accommodate over a Ductile‐Brittle Transitional zone cut by a low‐angle detachment fault. In the southern Tyrrhenian, normal, inverse and transcurrent faults appear to be related to a large shear zone located along the continental margin of the northern Sicily. Extensional style variation throughout the back‐arc basin combined with wide‐angle seismic velocity models allows to explore the relationships between shallow deformation, faults distribution throughout the basin, and crustal‐scale processes as thinning and exhumation.  相似文献   

16.
The Central Graben in the Danish North Sea sector consists of a series of N–S to NW–SE trending, eastward‐tilted half‐grabens, bound to the east by the Coffee Soil Fault zone. This fault zone has a complex Jurassic history that encompasses at least two fault populations; N–S to NNW–SSE striking faults active in the Late Aalenian–Early Oxfordian, and NNW–SSE to WNW–ESE striking faults forming in Late Kimmeridgian time (sensu gallico), following a short period of tectonic quiescence. Sediment transport across the Coffee Soil Fault zone was controlled by fault array evolution, and in particular the development of relay ramps that formed potential entry points for antecedent drainage systems from the Ringkøbing–Fyn High east of the rift. Fault and isochore trends of the Upper Kimmeridgian–Lower Volgian succession in the northeast Danish Central Graben show that accommodation space was initially generated close to several minor, isolated or overlapping faults. Subsidence became focused along a few master faults in the Early Volgian through progressive linkage of selected faults. Seismic time isochore geometries, seismic facies, amplitude trends and well ties indicate the presence of coarse clastic lithologies locally along the fault zone. The deposits probably represent submarine mass flow deposits supplied from footwall degradation and possibly also from the graben hinterland via a relay ramp. The latter source appears to have been cut off as the relay ramp was breached and the footwall block are uplifted. Fault growth and linkage processes thus controlled the spatial and temporal trends of accommodation space generation and sediment supply to the rift basin.  相似文献   

17.
ABSTRACT This study addresses the complex relationship between an evolving fault population and patterns of synrift sedimentation during the earliest stages of extension. We have used 3D seismic and well data to examine the early synrift Tarbert Formation from the Middle–Late Jurassic northern North Sea rift basin. The Tarbert Formation is of variable thickness across the study area, and thickness variations define a number of 1- to 5-km-wide depocentres bounded by normal faults. Seismic reflections diverge towards the bounding faults indicating that the faults were active contemporaneous with the deposition of the formation. Many of these faults became inactive during later Heather Formation times. The preservation of the Tarbert Formation in both footwall and hangingwall locations demonstrates that, during the earliest synrift, the rate of deposition balanced the rate of tectonic subsidence. Local space generated by hangingwall subsidence was superimposed upon accommodation generated due to a regional rise in relative sea-level. In basal Tarbert Formation times, transgression across the prerift coastal plain produced lagoons and bays, which became increasingly marine. During continued transgression, barrier islands moved landward across the drowned bays. In the southern part of our study area, shallow marine sediments are erosionally truncated by fluvial deposition. These fluvial systems were constrained by fault growth monoclines, and flowed parallel to the main faults. We illustrate that stratal architecture and facies distribution of early sedimentation is strongly influenced by the active short-lived faults. Local depocentres adjacent to fault displacement maxima focused channel stacking and allowed the aggradation of thick shoreface successions. These depocentres formed early in the rift phase are not necessarily related to Late Jurassic – Early Cretaceous depocentres developed along the major linked normal fault systems.  相似文献   

18.
“Salt” giants are typically halite‐dominated, although they invariably contain other evaporite (e.g. anhydrite, bittern salts) and non‐evaporite (e.g. carbonate, clastic) rocks. Rheological differences between these rocks mean they impact or respond to rift‐related, upper crustal deformation in different ways. Our understanding of basin‐scale lithology variations in ancient salt giants, what controls this and how this impacts later rift‐related deformation, is poor, principally due to a lack of subsurface datasets of sufficiently regional extent. Here we use 2D seismic reflection and borehole data from offshore Norway to map compositional variations within the Zechstein Supergroup (ZSG) (Lopingian), relating this to the structural styles developed during Middle Jurassic‐to‐Early Cretaceous rifting. Based on the proportion of halite, we identify and map four intrasalt depositional zones (sensu Clark et al., Journal of the Geological Society, 1998, 155, 663) offshore Norway. We show that, at the basin margins, the ZSG is carbonate‐dominated, whereas towards the basin centre, it becomes increasingly halite‐dominated, a trend observed in the UK sector of the North Sea Basin and in other ancient salt giants. However, we also document abrupt, large magnitude compositional and thickness variations adjacent to large, intra‐basin normal faults; for example, thin, carbonate‐dominated successions occur on fault‐bounded footwall highs, whereas thick, halite‐dominated successions occur only a few kilometres away in adjacent depocentres. It is presently unclear if this variability reflects variations in syn‐depositional relief related to flooding of an underfilled presalt (Early Permian) rift or syn‐depositional (Lopingian) rift‐related faulting. Irrespective of the underlying controls, variations in salt composition and thickness influenced the Middle Jurassic‐to‐Early Cretaceous rift structural style, with diapirism characterising hangingwall basins where autochthonous salt was thick and halite‐rich and salt‐detached normal faulting occurring on the basin margins and on intra‐basin structural highs where the salt was too thin and/or halite‐poor to undergo diapirism. This variability is currently not captured by existing tectono‐stratigraphic models largely based on observations from salt‐free rifts and, we argue, mapping of suprasalt structural styles may provide insights into salt composition and thickness in areas where boreholes are lacking or seismic imaging is poor.  相似文献   

19.
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   

20.
The structural evolution of the Miocene to Recent Gediz Graben is intimately related to the evolution of its southern margin. This margin is shaped by a time‐transgressive, composite structure that possesses flat‐ramp geometry with three separate dip domains: a low‐angle shallow segment; a steeper middle segment; and a low‐angle deeper segment. This geometry was probably produced by one of two mechanisms, which operated perpendicular to the general trend of the graben, resulting in gradual back‐rotation followed by abandonment of the shallow segment as it was dissected by the high‐angle normal fault(s). The geometry of the southern margin structure is not simple along‐strike. It includes broad undulations and discrete fault segments, developed by large‐scale fault growth processes through segment linkage. The along‐strike growth of the southern margin‐bounding structure is responsible for the composite character of the Gediz Graben and controls the observed stratigraphic variability. Two sub‐basins aligned with the major segments of the southern graben margin structure have been investigated. The Salihli and Ala?ehir sub‐basins comprising 3000 m sedimentary thickness are separated by an intervening basement high, that is covered by a thin veneer of post‐Miocene sediments. The two sub‐basins, which evolved as isolated basins during most of the graben history, amalgamated during post‐Miocene time to form the composite configuration of the graben. There is a general east to west trend of growth for the Gediz Graben.  相似文献   

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