Journal of Structural Geology最新文献

The Changdi fault, also known as the Changdi fault zone, is commonly proposed to be a branch of the Tan-Lu fault zone in the Tanhai region of the Bohai Bay Basin. Using three-dimensional seismic data, borehole data, isopach maps, and RMS maps, we attempted to provide a comprehensive understanding of the structural properties and sediment dispersal patterns occurring within the Changdi area from a source-to-sink perspective. Two distinct geomorphological factors were identified in the Changdi area and four types of strike-slip fault-controlled alluvial channels were proposed for the first time. Additionally, three types of sediment dispersal systems, characterized by various sediment infillings, source inputs, and source areas, were reported. The spatial and temporal variations in the geometry and kinematics of the Changdi fault zone were observed to regulate sediment dispersal within the subsag. Sediment dispersal systems in the Changdi area were regulated by sediment dispersal associated with faults resulting from strike-slip movement. The movement of the input port in the provenance area was controlled by strike-slip movements. The movement of the sedimentary center indicated that there was a dextral strike-slip distance of 3.24 km during the E₂s₃^L period. This study suggests that dextral strike-slip movements occurred in the Changdi fault zone, forming a strike-slip fault-controlled basin. The findings of this study may prove useful in developing models to predict the patterns of sediment dispersal controlled by strike-slip faults as well as the location of areas rich in sand.

We use a two-dimensional finite-element modeling approach to investigate the structural evolution of strike-slip faults under five different confining pressures and determine how their damage zone widths vary depending on the kinematic. Three representative fault segments are modeled, accounting for movement obliquity forming in pure strike-slip, oblique convergence and oblique divergence scenarios. The elastoplastic constitutive model (Drucker-Prager) was employed to couple an associated flow rule into the initial stress state of a geostatic stage. We applied two empirical methods for determining the width of the damage zone from progressive model response. The first method involves using the plastic strain distribution curve's inflection points, to mathematically fixate the width. The second method uses the standard deviation obtained from a trend Gaussian/Normal probability distribution, with over 98% fit to the plastic strain curve data, simplifying the inference of the strain propagation along the model. The simulation results indicate inverse proportional relationships between confining pressure and both porosity and plastic strain intensity, while showing a direct proportional relationship with the damage zone width. For fault zone width quantification, results show convergence between the methods, revealing widths of 2.46–2.65 m for oblique divergence (displacement of 0.20 m), 2.65–3.55 m for pure strike-slip (displacement of 0.20 m), and 4.36–4.46 m for oblique convergence zones (displacement of 0.70 m). The pure strike-slip and the oblique convergence damage zone width results align well with outcrop observations of faults with similar kinematics from the literature, underscoring the significance of numerical modeling as a valuable tool for measure and study the mechanics of characterizing the nucleation of fault zones and quantifying the width of the damage zone.

The evolution of normal fault arrays during rift extension reflects paleo-plate boundary conditions and lithospheric rheology, while controlling seismic hazard and the distribution of basin-hosted resources. Yet, constraining their spatiotemporal development is challenging, particularly where geophysical and subsurface data are absent. Here, we test footwall exhumation modelling using thermochronology as a means of elucidating 4D normal fault array evolution, using the Miocene Central Basin of the Malawi Rift as a natural laboratory. Along-strike trends in exhumational cooling recorded by vertical transects of apatite fission-track and (U–Th)/He data from the basin-bounding Usisya fault scarp reveal a diachronous footwall uplift history that closely reflects 4D trends in hangingwall subsidence recorded by previously published seismic and well data. Initially, pronounced footwall exhumation is restricted to the centres of a series of four isolated normal faults, mirroring the distribution of early syn-rift depocentres. The later onset of footwall exhumation in the intervening areas marks subsequent fault segment propagation and linkage as they formed the through-going Usisya fault system. Elsewhere, cumulative exhumation recorded in the Usisya footwall remains low, coinciding with more significant intra-basinal faulting. This study shows that footwall exhumation modelling constrained by thermochronologic data can reveal the spatiotemporal evolution and strain partitioning within normal fault arrays.

The Central High Atlas is distinguished by map-scale, sigmoid, and narrow magmatic-cored ridges, which separate wide and open synclines. The origin of these structures has been debated for years. This study addresses this issue from a paleostress perspective, using mesostructural analysis in the Imilchil region and incorporating insights from previous research.

Our analysis reveals that the Central High Atlas ridges developed through two main structural stages from the Jurassic to the Cenozoic. The first stage involved an extensional event characterized by NW-SE-oriented σ3, coeval with the Early Jurassic Tethyan extension. This was followed by wrench tectonics driven by oblique left-lateral motion of Africa with respect to Europe. This events is marked within the Central High Atlas by ENE-WSW-oriented σ1 and NNW-SSE-oriented σ3. The basin-scale left-lateral motion likely drove the formation of sigmoid stepovers, facilitating the emplacement of magmatic bodies from the Middle Jurassic to the Early Cretaceous. The second deformation stage is likely associated with the convergence between Africa and Europe and the consecutive Alpine orogeny. In the study area, this stage consists of three events: a pre-folding strike-slip event with NNE-SSW to N–S-oriented σ1, and a pre-folding strike-slip event with NW-SE-oriented σ1. Near the diapirs, the analyzed mesostructures display syn-to post-folding patterns in some locations, indicating pre-Alpine layer tilting driven by salt tectonics. The final event is marked by significant post-folding NW-SE compression, associated with the Central High Atlas basin inversion and the compaction of pre-existing magmatic-cored salt diapirs.

This study highlights the complex deformation history that has influenced the evolution of the Central High Atlas ridges and provides evidence of the significant role of strike-slip tectonics during the post-rift period and magmatic emplacement, as well as in the early phases of basin inversion.

Fold-and-thrust belts and accretionary prisms exhibit considerable variability in slip behaviors along active faults. While numerous studies have investigated fault mechanics and slip behaviors in carbonate-, shale-, and sandstone-hosted faults as well as clay-rich portions of shallow accretionary prisms, the deformation mechanisms and slip behaviors of deformed, thrust-top molasse-type conglomerates remain poorly understood. To fill this knowledge gap, we conducted structural and microstructural analyses on exhumed and deformed conglomerates in the footwall of an out-of-sequence thrust from the Central Apennines fold-and-thrust belt (Italy). Our findings aim to constrain conglomerate deformation mechanisms and infer possible slip behaviors. We observed flattened pebbles and an intense foliation comprising densely spaced, thrust-parallel, clay-rich stylolites that indicate slow deformation attributed to carbonate dissolution during aseismic creep. In contrast, quartz clasts with calcite micro veins and micrometer-thick slip increments in slickenfibers suggest fast brittle failure and fluid overpressure in competent pebbles, while the matrix continues to deform aseismically through pressure solution. The general structure is similar to block-in-matrix textures observed in tectonic mélanges from exhumed subduction zones and accretionary prisms. Our results provide new insights into the slip behaviors of shallow (<∼1 km) portions of fold-and-thrust belts, complementing existing understandings of deformation mechanisms and slip behaviors across different depth ranges in fold-and-thrust belts and accretionary prisms.

The transpressive deformation in the eastern Jiangnan Orogen during the Early Paleozoic is the structural response to the oblique convergence of the Yangtze-Cathaysia blocks, and this relationship is critical for understanding the tectonics of South China. The Jiangwan–Huangshan shear zone (JHSZ) and Baiji–Sanyang shear zone (BSSZ) exhibit NEE–SSW-trending oblique dextral and sinistral shearing, respectively, and their evolution resulted in local E–W dextral strike-slip shearing. Most kinematic vorticity values range from 0.4 to 0.81, which implies that the JHSZ and BSSZ deformed under the contribution of both pure-shear and simple-shear components, suggesting complicated deformation histories for those orogenic shear zones. The quartz and feldspar deformation mechanisms, opening angles and lattice preferred orientation (LPO) patterns of the quartz c-axis fabrics suggest shear deformation temperatures between 400 and 550 °C in the eastern Jiangnan Orogen. Locally deformation occurred under high-temperature (>600 °C) conditions. Combined with previous data and regional geology, these findings indicate that the shearing deformation in the eastern Jiangnan Orogen accommodated the oblique convergence between the Yangtze and Cathaysia blocks during the Early Paleozoic, which was possibly caused by the final assembly of Gondwana.

It is crucial to determine the sequence of deformation and the interaction between shallow and deep structures within the multiple detachment systems to comprehend geological processes fully in fold-and-thrust belts (FTBs). Here, we implement forward modeling to investigate the geometric, kinematic, and syntectonic sedimentary characteristics of shallow and deep structural interactions. We design four combinative patterns of geometric structures, three kinematic sequence scenarios, and two settings with different ratios of the sedimentation rate to the uplift rate to examine the influence of such settings on growth strata geometry. The most effective results of 24 groups of shallow and deep structural interactions were obtained for various combinations of fault-bend fold, detachment fold, and tectonic wedge. This study provides a sequential kinematic image of FTBs, illustrating the interaction of two sets of detachments and demonstrating how different styles of pre- and growth strata can be utilized to identify shallow and deep structure deformation processes. The geometry of pre- and growth strata observed in the models is similar to that observed in natural structures. These forward models facilitate a better understanding of the complex geometry and kinematics of the interaction between shallow and deep fault-related folds.

Fractures in organic-rich shale affect the evolution of permeability and control shale gas preservation. We characterize fracture attributes in the Qiyue-Huaying Fold-Thrust belt in the southeastern Sichuan Basin, revealing the distribution, origin and factors controlling fracture localization through investigation of cores, image logs, and thin section petrography. We found that the deformation intensity, organic matter content and lithology are the major factors for controlling fracture occurrence and location in the Wufeng-Longmaxi deep shale. The major fracture pattern in the Fuling Block is characterized by abundant inclined shear fractures, bed-parallel shear fractures, and bed-normal extension fractures, while bed-parallel veins prevail in the Luzhou Block. In general, fracture density and size in the Fuling Block are larger than those in the Luzhou Block. The competent layers (siliceous shale with high TOC) have the highest fracture density, and noticeably, organic matter content controls bed-parallel vein localization. Based on the distribution of fractures in two blocks, we suggest that the dominant origin of fractures in organic-rich shale gradually changes from tectonic events to fluid pressure changes due to organic maturation (organic events), from the Fuling Block to the Luzhou Block.

Reactivation of the Qinling Orogen since the Late Jurassic has been controlled by the combined effects of the convergence between the South and North China blocks, the subduction of the Pacific Plate, and the northeastward expansion of the Tibetan Plateau. In this study, we present new apatite (U–Th)/He ages from a vertical transect in the Fenghuang Shan located in the North Daba Mountains, where rapid cooling at ∼95-90 Ma is identified. Inverse thermal history modeling results reveal another pulse of accelerated exhumation at ∼50 Ma. In addition, we analyzed longitudinal profiles of rivers draining the northern flank of the Fenghuang Shan and identified knickpoints that break channels into gentle upstream and steep downstream segments. We deduce that these knickpoints were initiated by an increase in the mountain-bounding fault throw, based on nearly constant chi values (an integral to the upstream drainage area distribution) and a reliance of knickpoints’ retreat distances on catchment areas. Assuming a linear slope exponent and erodibility of 10⁻⁶ m^0.1/a, we estimated knickpoint ages to be ∼5.7 ± 1.7 Ma. We interpret the Late Cretaceous cooling as a result of lithospheric extensional collapse following the Late Jurassic intra-continental compression between the North and South China blocks. The early Cenozoic exhumation might relate to the active normal faulting, as a far-field response to the west Pacific back-arc extension. The expansion of the NE Tibetan Plateau may have triggered the late Miocene uplift of the mountain range. The multiple episodes of tectonic events in the Fenghuang Shan might correspond to various geodynamic regimes on the tectonic evolution in the Qinling Orogen.