Growth Of Normal Faults Research Articles

Architectural rift geometry of the Rio do Peixe Basin (Brazil): Implications for its tectonic evolution and Precambrian heritage

Preexisting shear zones in the basement may influence the formation of normal faults in rift environments. However, the specific role and interaction between these preexisting shear zones and younger rift faults in controlling the growth of normal faults remain an area of limited understanding. The Rio do Peixe Basin (RPB), located in Brazil, was the subject of a comprehensive study using integrated airborne magnetic analysis, 2D and 3D seismic interpretation, and 3D gravity modeling. This study investigated tectonic evolution and Precambrian heritage by examining the role of basement structures in controlling the internal geometry of the RPB. The integration of geophysical data supported by field data showed that the underlying basement structures significantly influence the geometry of the basin sedimentary fill. E–W-striking structures controlled the opening of the RPB and the development of the depocenters of the basin. NE–SW-striking structures influenced the segmentation of the depocenters and, consequently, the internal geometry of the basin. Furthermore, the study revealed the migration of depocenters toward the NE associated with developing the NE–SW-striking segment of the Portalegre Fault attributed to the basin-opening process. By investigating the underlying crustal architecture, this comprehensive geophysical study sheds light on the architectural rift geometry of the RPB. The findings underscore the influence of basement structures on the internal basin architecture and provide valuable insights into its tectonic evolution and Precambrian heritage.

3D Evolution of Detachment Fault Systems in Necking Domains: Insights From the Klakk Fault Complex and the Frøya High, Mid‐Norwegian Rifted Margin

AbstractDetachment fault systems typically record displacements in the order of 10s of kilometers. The principles that control the growth of smaller magnitude normal faults are not fully applicable to the evolution of detachment fault systems. We use interpretation of 2D and 3D seismic reflection data from the mid‐Norwegian rifted margin to investigate how the structural evolution of a detachment fault interacted with the effects of isostatic footwall rollback to produce complex 3D geometries and control the configuration of associated supradetachment basins. We further investigate the effects of lateral interaction and linkage of extensional detachment faults on the necking domain configuration. In our study area, the domain‐bounding Klakk Fault Complex demonstrates how successive incision may induce a complex structural relief in response to faulting and fault plane folding. We interpret the previously proposed metamorphic core complex within its footwall as an extension‐parallel turtleback‐structure. The now eroded turtleback is flanked by a major supradetachment basin, connecting two main basin segments. We attribute footwall‐ and turtleback exhumation to Middle Jurassic‐Early Cretaceous rifting. The study area further demonstrates how detachment fault geometries can change during rifting and lead to the formation of younger, successively incising fault splays. Lateral linkage between the original detachment fault plane and these fault splays enables displacement along a detachment fault system consisting of fault segments generated at different stages in time. Implicitly, detachment faults are complex 3D systems that change configuration during their evolution, perpetually controlling associated basin formation, footwall configuration, subsidence and uplift patterns.

Lateral and vertical growth and linkage of normal faults in Bozhong8-4 structure of Western Bozhong Sag, Bohai Bay Basin, China

Many previous studies have shown that normal faults are formed by growth and linkage of shorter fault segments through time and have suggested various fault growth models. Although these models have yielded useful information on the evolution of normal fault systems in map view, the three-dimensional (3D) evolution of normal faults is poorly understood. Here, we employ an integrated 3D seismic reflection and well dataset to investigate the 3D growth process of fault zone F1 in the Bozhong 8–4 (BZ8-4) structure of the Western Bozhong Sag (WBS). We i) constructed 3D structural models of individual fault surfaces, ii) calculated the dip angles and dip azimuth distributions on fault surfaces, iii) produced D-d profiles and throw contour maps of fault surfaces, and iv) investigated the 2D/3D segmentation characteristics of geometry and displacement distribution. We found that Fault F1 exhibits segmentation characteristics of geometry and displacement distribution both along strike and dip oriented directions. Vertically, fault surfaces can be divided into three areas (lower, middle and upper parts) that correspond to three stages of regional tectonic evolution (intense faulting, relatively quiescent faulting and post-rifting). The coalescence zone of the upper and lower fault surfaces shows as a sub-horizontal anomaly of geometry and displacement distribution that is sub-parallel to the traces of the horizons. The lower and upper parts of fault surfaces also show segmentation characteristics along strike, which are identified by vertically anomalous zones of geometry and displacement distribution. However, the origins of the segmentation in this case are different. The segmentation of the lower part of the fault developed during the rifting stage is caused by the intersection of faults with different strikes, whereas the upper part of the fault is the result of the lateral growth and linkage of overlapping fault segments. Therefore, not all fault segmentation characteristics along strike can be attributed to fault growth and linkage. Based on 3D fault segment identification, we therefore establish a 3D evolution model of fault zone F1. During the deposition of the Shahejie Fm up to the member (Mbr) 3 of the Dongying Fm in the Paleogene, the faults in this area were highly active, with the development of the NE-trending Fault F1, the NEE-trending Fault Fa and the NW-trending Fault F2. The intersection of Faults Fa and F2 with Fault F1 results in Fault F1 exhibiting segmentation in geometry and displacement distribution. From the deposition of the Mbr 2 of the Dongying Fm, these faults ceased to be active. Since the Pliocene (5.2 Ma), under the influence of transtensional stress field, an en-echelon fault zone was developed in the Neogene strata above fault zone F1 active in the rifting stage. While these faults grow and link laterally, their tip-lines propagate along dip-oriented directions and activate the lower faults and link vertically with them to form the present fault zone F1.

Growth and linkage of normal faults experiencing multiple non‐coaxial extension: A case from the Qikou Sag, Bohai Bay Basin, East China

AbstractOblique‐slip faults, which are essentially reactivated pre‐existing fault caused by non‐coaxial stress, are common in rift basins. Large faults with lengths exceeding thousands of kilometres are mostly rooted faults and would have experienced numerous reactivations. Using 3D seismic and drilling data, we investigated the geometry, kinematic features, growth and linkage, and three‐dimensional evolution of the Nandagang fault system (NDGFS) on the Qinan Slope in the Qikou Sag, Bohai Bay Basin. A hybrid fault model incorporating a lengthening stage and a displacement accrual stage was used to analyse the growth and linkage of NDGFS. By using the throw/displacement backstripping approach, ratios of maximum displacement to fault length (Dmax/L) of the evolving NDGFS were also obtained to delineate faulting stages of the hybrid fault model. From the pre‐Cenozoic basement to the Quaternary strata, NDGFS comprises three fault systems separated vertically by two unconformities, namely the lower, the middle and the upper systems. On planar view, NDGFS encompasses three structural trending zones with variable vertical growth styles. The E–W and NEE–SWW trending zones are mainly dominated by growth faults, while the NE–SW zones are characterised by dip‐linkage faults. For NDGFS, both the middle and deeper fault segments experienced a two‐stage hybrid faulting and reached their final lengths in ca. 20%–30% less time than the usual faulting lifetime proposed by previous researchers. In contrast, the upper faults, especially the segments within the Neogene Guantao (Ng) and Minghuazhen (Nm) formations, only experienced a lengthening stage. The slip rates and the pre‐existing faults have strong influences on the duration that faults accomplished their lengthening stages. A Dmax/L ratio of 0.015 obtained from the evolving NDGFS is determined to be effective in delineating between the lengthening stage and the displacement accrual stage, which may have a broad application for normal faults in similar geological settings.

A new model for the growth of normal faults developed above pre-existing structures: COMMENT

A new model for the growth of normal faults developed above pre-existing structures: COMMENT

A new model for the growth of normal faults developed above pre-existing structures

AbstractConstraining the mechanisms of normal fault growth is essential for understanding extensional tectonics. Fault growth kinematics remain debated, mainly because the very earliest phase of deformation through recent syn-kinematic deposits is rarely documented. To understand how underlying structures influence surface faulting, we examined fault growth in a 10 ka magmatically resurfaced region of the Krafla fissure swarm, Iceland. We used a high-resolution (0.5 m) digital elevation model derived from airborne lidar to measure 775 fault profiles with lengths ranging from 0.015 to 2 km. For each fault, we measured the ratio of maximum vertical displacement to length (Dmax/L) and any nondisplaced portions of the fault. We observe that many shorter faults (<200 m) retain fissure-like features, with no vertical displacement for substantial parts of their displacement profiles. Typically, longer faults (>200 m) are vertically displaced along most of their surface length and have Dmax/L at the upper end of the global population for comparable lengths. We hypothesize that faults initiate at the surface as fissure-like fractures in resurfaced material as a result of flexural stresses caused by displacements on underlying faults. Faults then accrue vertical displacement following a constant-length model, and grow by dip and strike linkage or lengthening when they reach a bell-shaped displacement-length profile. This hybrid growth mechanism is repeated with deposition of each subsequent syn-kinematic layer, resulting in a remarkably wide distribution of Dmax/L. Our results capture a specific early period in the fault slip-deposition cycle in a volcanic setting that may be applicable to fault growth in sedimentary basins.

Formation of listric normal faults by extensional duplexing: A case study from the active Langshan piedmont fault, NW China

The development of normal faults is controlled by many factors, among which mechanical layers or pre-existing fabrics play an important role in the growth of normal faults. It is widely accepted that normal faults are rarely continuous surfaces but are zones composed of fault segments, heterogeneously distributed fault rocks of various compositions, slip bands, blocks and other deformation elements. Listric normal faults, particularly those developed in metamorphic crystalline rocks or preexisting fabric-developed basements, may be composed of subparallel faults in cross-sections, linked by extensional duplex structures. Here, we choose a listric rift-bounding fault rooted in foliation developed basements, the Langshan normal fault in the northwest corner of the Ordos Block, to conduct an outcrop analysis of fault geometry and linkage behavior from cross-sectional views. The Langshan normal fault zone is composed of mixed regions of high- and low-angle segments linked by duplex structures at various scales. Mylonitic foliations play a significant role in the formation of fault segments and the evolution of the listric fault zones. Lines of evidence show that small en echelon faults initiated from preexisting foliations. Local stress perturbation between overstepping faults results in the formation of duplex structures and displays a high fracture density, which serve to the coalesce of fault segments. Consequently, the progressive localization of strain onto a large listric fault is achieved by progressive development of extensional duplexing among fault segments in cross-sections. These extensional duplexes imply a scale-invariant property, based on which we can extrapolate this pattern occurs on larger scales and is verified by seismic data. The case of Langshan piedmont fault demonstrates the possibility of a listric fault being formed by subparallel planner faults and highlights the effects of preexisting fabrics on the evolution of listric faults, especially in basement fabrics developed regions along the fault.

Using polygonal layer-bound faults as tools to delimit clastic reservoirs in the Levant Basin offshore Lebanon

The Levant Basin offshore Lebanon contains an array of layer-bound normal faults in the Oligocene–Miocene units. The faults are believed to have nucleated in fine-grained sedimentary rocks similar to polygonal fault systems worldwide, and as a result, they may be influenced by lithological heterogeneities in the host-rock unit. Three-dimensional seismic data and amplitude extraction from offshore Lebanon were used to map deep-water channels and fan lobes, demonstrating that the distribution, geometry, and growth of the layer-bound normal faults are affected by these sedimentary bodies, which are impacting fault propagation. Three fault types are identified, differentiated by their growth models and overall geometry. Type I faults in the deep basin indicate that a competent unit is present in the lower Miocene and is affecting their growth. Type II and III faults in the Latakia ridge and the margin, respectively, are smaller because of restriction by upper Miocene and lower Oligocene basin-floor fans. Based on their seismic expression and on analogy with other basins containing similar faults, it is very likely that the overlying and underlying units causing restriction consist of coarse-grained clastic intervals. Therefore, reservoirs offshore Lebanon are probably lower Miocene in the deep basin, whereas in the Latakia ridge and the Levant margin, reservoirs are in upper Miocene and in lower Oligocene units. This study provides an additional evidence that layer-bound, or polygonal faults, can have practical industrial application during exploration of hydrocarbons, even in the absence of well data.

Throw-rate variations within linkage zones during the growth of normal faults: Case studies from the Western Volcanic Zone, Iceland

This work investigates how throw-rates vary within fault bends and sites of fault linkage during the process of normal fault growth. In the Western Volcanic Zone, Iceland, through detailed field mapping and field measurements of fault throws, normal faults are mapped and along-strike throw profiles are constructed in order to understand how the throw-rates relate with the local fault geometry along faults at different stages of linkage. The results show that throw-rates increase within linkage zones and propagating fault bends independently from the stage of maturity of the fault bend. This implies that 1) the relationship between the local fault geometry and the along-strike distribution of throw-rate is driven by the deeper part of the fault, where established fault bends start propagating to the surface; 2) faults grow first by linkage and coalescence of separate faults, and then by accumulation of slip on the resultant fault, in agreement with models of fault growth by linkage and coalescence; 3) incipient fault bends can produce uncertainty associated with palaeoseismological results, if fault bends remain unrecognised. Moreover, this work demonstrates that existing models showing increased co-seismic and throw-rates within fault bends and sites of fault linkage found in continental extensional settings are valid in a geodynamic context of a mid-oceanic rifts.

Pre-existing intra-basement shear zones influence growth and geometry of non-colinear normal faults, western Utsira High–Heimdal Terrace, North Sea

Pre-existing intra-basement shear zones can induce mechanical and rheological heterogeneities that may influence rifting and the overall geometry of rift-related normal faults. However, the extent to which physical and kinematic interaction between pre-existing shear zones and younger rift faults control the growth of normal faults is less-well understood. Using 3D reflection seismic data from the northern North Sea and quantitative fault analysis, we constrain the 3D relationship between pre-existing basement shear zones, and the geometry, evolution, and synrift depositional architecture of subsequent rift-related normal faults. We identify NE-SW- and N-S-striking rift faults that define a coeval Middle Jurassic – Early Cretaceous, non-colinear fault network. NE-SW-striking faults are parallel to underlying intra-basement shear zone. The faults either tip-out above or physically merge with the underlying shear zone. For faults that merges with the basement shear zone, a change from tabular to wedge-shaped geometry of the hangingwall synrift strata records a transition from non-rotational to rotational extension faulting, which we attribute to the time of rift fault's linkage with the shear zone, following downward propagation of its lower tip. N-S-striking faults are oblique to, and offset (rather than link with) intra-basement shear zones. These observations highlight the selective influence pre-existing intra-basement shear zones may (or may not) have on evolving rift-related normal faults.

Impacts of data sampling on the interpretation of normal fault propagation and segment linkage

Throw-distance (T-D) and throw-depth (T-Z) plots are widely used by researchers and industry to examine the growth of normal faults. This study uses high-quality three-dimensional (3D) seismic and outcrop information to review the effect of data sampling on the interpretation of normal fault growth. The results show that the accuracy of T-D and T-Z data, and of resulting fault slip tendency and leakage factor analyses, are dependent on the sampling strategy followed by interpreters and field geologists, i.e. on a Sampling Interval/Fault Length Ratio (δ) for discrete structures. In particular, this work demonstrates that significant geometric changes in T-D plots occur when a Module Error (εi) for the ratio δ is larger than 6%–9% for faults of all scales and growth histories. This implies that a minimum number of measurements should be gathered on discrete faults to produce accurate T-D and T-Z plots, and that the number of measurements is dependent on fault length. With no prior knowledge of fault segmentation, a δ value of 0.05 should be applied when interpreting faults to fulfil the pre-requisite of a ɛi < 6–9%. In all faults analysed, slip tendency and leakage factors were systematically misrepresented with increasing δ values. To disregard the limits proposed in this work results in: 1) a systematic underrepresentation of the isolated fault growth model, 2) a systematic misrepresentation of fault geometries and related damage zones, 3) the collation of erroneous fault scaling relationships, and 4) ultimately, unreliable interpretations of fault sealing properties. Hence, this work presents a new tool for interpreters and structural geologists to understand the sampling strategies necessary to obtain accurate fault throw and displacement data at different scales of analysis.

Tectono‐sedimentary evolution of the Plio‐Pleistocene Corinth rift, Greece

AbstractThe onshore central Corinth rift contains a syn‐rift succession &gt;3 km thick deposited in 5–15 km‐wide tilt blocks, all now inactive, uplifted and deeply incised. This part of the rift records upward deepening from fluviatile to lake‐margin conditions and finally to sub‐lacustrine turbidite channel and lobe complexes, and deep‐water lacustrine conditions (Lake Corinth) were established over most of the rift by 3.6 Ma. This succession represents the first of two phases of rift development – Rift 1 from 5.0–3.6 to 2.2–1.8 Ma and Rift 2 from 2.2–1.8 Ma to present. Rift 1 developed as a 30 km‐wide zone of distributed normal faulting. The lake was fed by four major N‐ to NE‐flowing antecedent drainages along the southern rift flank. These sourced an axial fluvial system, Gilbert fan deltas and deep lacustrine turbidite channel and lobe complexes. The onset of Rift 2 and abandonment of Rift 1 involved a 30 km northward shift in the locus of rifting. In the west, giant Gilbert deltas built into a deepening lake depocentre in the hanging wall of the newly developing southern border fault system. Footwall and regional uplift progressively destroyed Lake Corinth in the central and eastern parts of the rift, producing a staircase of deltaic and, following drainage reversal, shallow marine terraces descending from &gt;1000 m to present‐day sea level. The growth, linkage and death of normal faults during the two phases of rifting are interpreted to reflect self‐organization and strain localization along co‐linear border faults. In the west, interaction with the Patras rift occurred along the major Patras dextral strike‐slip fault. This led to enhanced migration of fault activity, uplift and incision of some early Rift 2 fan deltas, and opening of the Rion Straits at ca. 400–600 ka. The landscape and stratigraphic evolution of the rift was strongly influenced by regional palaeotopographic variations and local antecedent drainage, both inherited from the Hellenide fold and thrust belt.

The kinematics of normal faults in the Ceduna Subbasin, offshore southern Australia: Implications for hydrocarbon trapping in a frontier basin

The geometry and growth of normal faults are fundamental to the evolution and petroleum prospectivity of sedimentary basins, controlling trap development; source, reservoir, and seal rock distribution; and fluid flow. The poorly studied, petroliferous Ceduna Subbasin located offshore southern Australia contains an east–southeast-striking, gravity-driven fault array, which soles out onto a southwest-dipping detachment horizon. These gravity-driven faults displace the White Pointer delta and overlying Hammerhead delta. Within the subbasin, structural closures bound by these gravity-driven faults represent the main exploration targets. Determining when these faults and associated traps formed relative to petroleum generation and migration and, more specifically, if the faults reactivated is thus critical to understanding the prospectivity of the Ceduna Subbasin. In this study, we use a time-migrated two-dimensional (2-D) seismic reflection survey covering the central Ceduna Subbasin to constrain the geometry and kinematics of the fault array. Throw patterns reveal that most faults nucleated in the Cenomanian. Although some faults display evidence for continuous growth by upper tip propagation throughout the Cenomanian to Maastrichtian, it is apparent that other faults were inactive during the Turonian–Santonian, before reactivating and propagating upward or dip-linking with overlying, newly formed faults during the Campanian and/or Maastrichtian. Faults that grew continuously during the Cenomanian to Maastrichtian primarily formed in the center of the study area, whereas reactivated faults developed in landward positions. Faults that formed because of dip linkage developed in seaward positions. We suggest that this spatial variation in fault growth style was controlled by compositional and mechanical heterogeneities in the Tiger and lower Hammerhead supersequences, which mark the boundary between the two delta systems. In addition to providing insights into the petroleum prospectivity of the Ceduna Subbasin, this study shows how 2-D seismic reflection data can be used to probe the kinematics of normal faults.

About this title ‐ The Geometry and Growth of Normal Faults

Normal faults are the primary structures that accommodate extension of the brittle crust. This volume provides an up-to-date overview of current research into the geometry and growth of normal faults. The 23 research papers present the findings of outcrop and subsurface studies of the geometrical evolution of faults from a number of basins worldwide, complemented by analogue and numerical modelling studies of fundamental aspects of fault kinematics. The topics addressed include how fault length changes with displacement, how faults interact with one another, the controls of previous structure on fault evolution and the nature and origin of fault-related folding. This volume will be of interest to those wishing to develop a better understanding of the structural geological aspects of faulting, from postgraduate students to those working in industry.

Introduction to the geometry and growth of normal faults

Introduction to the geometry and growth of normal faults

Growth and interaction of normal faults and fault network evolution in rifts: insights from three-dimensional discrete element modelling

Abstract The initiation, growth and interaction of faults within an extensional rift is an inherently four-dimensional process where connectivity with time and depth are difficult to constrain. A 3D discrete element model is employed that represents the crust as a two-layered brittle–ductile system in which faults nucleate, propagate and interact in response to local heterogeneities and resulting stresses. Faults nucleate in conjugate sets throughout the model brittle crust; they grow through a combination of tip propagation and interaction of co-linear segments to form larger normal faults. Segment linkage occurs by merging of adjacent fault segments located along strike, downdip or oblique to one another. Finally, deformation localizes onto the largest faults. Displacement distribution on faults is highly variable with marked along-strike and temporal variations in displacement rates. Displacement maxima continuously migrate as smaller fault segments interact and link to form the final fault plane. As a result, displacement maxima associated with fault nucleation sites are not coincident with the location of the maximum finite displacement on a fault where segment linkage overprints the record. The observed style of fault growth is consistent with the isolated growth model in the earliest stages which then gives way to a coherent (constant-length) fault growth model at greater strains.

Analysis of gravity-driven normal faults using a 3D seismic reflection dataset from the present-day shelf-edge break of the Otway Basin, Australia

The growth, interaction and controls of gravity-driven normal faults is somewhat understudied. Using three-dimensional (3D) and two-dimensional (2D) seismic reflection data, located at the present-day shelf-edge break and into the deepwater province of the Otway Basin, southern Australia, we aim to temporally and spatially constrain the development of a normal fault system and determine the controls on growth. The Otway Basin is a Late Jurassic to Cenozoic age, rift-to-passive margin basin. The seismic reflection data images a gravity-driven fault array, consisting of ten fault segments, striking NW-SE (128-308), located within Upper Cretaceous clastic sedimentary rock. We analyse the growth of a gravity-driven hard-linked fault assemblage interacting with basement normal faults. Our analysis shows that the fault assemblage is linked to major basement faults and displays Turonian-Santonian nucleation, continued growth until the latest-Maastrichtian and a maximum throw of 1.74 km. High variability of throw along-strike and down-dip of the fault assemblage indicates growth via lateral and vertical segment linkage. We interpret that the spatial and temporal evolution of the fault assemblage is the result of rifting basement fault control during Upper Cretaceous resumed crustal extension in the Otway Basin. The control of the rifting basement faults on these gravity-driven normal faults has implications towards the growth and petroleum prospectivity of gravity-driven normal faults on passive margins such as the Niger Delta and Gulf of Mexico, but also towards gravity-driven normal faults developed in supra-salt sedimentary rock in rift basins, such as the North Sea and Suez Rift.

Impact of normal faulting and pre‐rift salt tectonics on the structural style of salt‐influenced rifts: the Late Jurassic Norwegian Central Graben, North Sea

AbstractStudies 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.

Three-dimensional Distinct Element Method modelling of the growth of normal faults in layered sequences

Abstract The growth of normal faults in mechanically layered sequences is numerically modelled using three-dimensional Distinct Element Method (DEM) models, in which rock comprises an assemblage of bonded spherical particles. Faulting is induced by movement on a pre-defined normal fault at the model base whilst a constant confining pressure is maintained by applying forces to particles lying at the model top. The structure of the modelled fault zones and its dependency on confining pressure, sequence (net:gross) and fault obliquity are assessed using various new techniques that allow (a) visualization of faulted horizons, (b) quantification of throw partitioning and (c) determination of the fault zone throw beyond which theoretical juxtaposition sealing occurs along the entire zone length. The results indicate that fault zones become better localized with increasing throw and confinement. The mechanical stratigraphy has a profound impact on fault zone structure and localization: both low and high net:gross sequences lead to wide and relatively poorly localized faults. Fault strands developing above oblique-slip normal faults form, on average, normal to the greatest infinitesimal stretching direction in transtensional zones. The model results are consistent with field observations and results from physical experiments.

Growth of layer-bound normal faults under a regional anisotropic stress field

Abstract Layer-bound normal faults commonly form polygonal faults with fine-grained sediments early in their burial history. When subject to anisotropic stress conditions, these faults will be preferentially oriented. In this study we investigate how faults grow, evolve and interact within regional-scale layer-bound fault systems characterized by parallel faults. The intention is to understand the geometry and growth of faults by applying qualitative and quantitative fault analysis techniques to a 3D seismic reflection dataset from the Levant Basin, an area containing a unique layer-bound normal fault array. This analysis indicates that the faults were affected by mechanical stratigraphy, causing preferential nucleation sites of fault segments, which were later linked. Our interpretation suggests that growth of layer-bound faults at a basin scale generally follows the isolated model, accumulating length proportional to displacement and, when subject to an anisotropic regional stress field, resembling to a great extent classical tectonic normal faults.