The drainage response to the vertical uplift and lateral propagation of active folds has been comprehensively investigated. However, most natural folds have typically undergone more intricate evolution histories, for instance, those involving the linkage of several segments in an oblique pattern. During this process, the direction of regional stress may also vary over time. In this study, we select the Xiongpo anticline in the southwestern Sichuan Basin adjacent to the Longmen Shan thrust belt as a case to conduct morphotectonic analysis. Since its subsurface geometry and evolution history have been well-constrained previously, we explore how the fold landscape responds to multi-stage tectonic shortening with variable directions. Our results show an obvious decreasing trend in topographic factors and geomorphic parameters towards the east. The revealed segmentation of tectonic activity, specifically the highest degree in the southern segment, contrasts with the earliest formation of the central segment. We suggest that the preferred structural orientation during the latest stages has promoted the vigorous growth of the southern segment, resulting in the development of the highest peak and the largest knickpoint elevations and drop heights. The application of a novel method to extract hypsometric integral values has enabled the identification of active-hinge folding in the study area. Combining the estimated drainage erosion and channel incision, we show that active folding in the Xiongpo anticline mainly occurred in a hinge-migration mode. Considering the recent earthquake that occurred at the junction of the central and southern segments, it becomes vital and urgent to conduct further assessments of seismic potentials.

The quantitative analysis of drainage landscapes utilizing digital elevation models (DEMs) has been widely adopted to effectively investigate structural development and evolution. However, the orientation of tectonic forces often exhibits intricate patterns and undergoes dynamic changes, leading to the superimposition of tectonic deformation and the emergence of complex structural styles. The response of drainage networks to these complex processes has been rarely documented. The Weiyuan anticline in the SW Sichuan Basin, China, serves as a case study to evaluate its applicability. Derived topographic metrics and geomorphological features indicate that deep tectonic deformation with an asymmetric uplift pattern results in contrasting tectonic activity on its flanks. The currently observed triangular distribution of anomalously high geomorphological indices in the central and northern regions suggests the presence of superimposed deformation. It is probable that the Weiyuan anticline has experienced two stages of tectonic shortening: an initial SE-directed basinward propagation of deformation from the Longmen Shan, followed by an east-west-directed shortening owing to the eastward extrusion of the Tibetan Plateau. Observed drainage patterns reveal that the current landscapes are undergoing transient adjustments. Quantitative morphotectonic analysis is proposed as a reliable and effective method for unravelling the complex history of structural superimposition.

Although numerous studies have shown that deformation within contractional fold-and-thrust belts is significantly affected by the spatial variation of stratum properties, due to the limitations of the available subsurface data quality, more specific research on how stratigraphic sedimentary facies changes influence structural styles is still scarce. Benefiting from the newly-acquired 2D and 3D seismic reflection, well-logging and core data during the hydrocarbon exploration and development, we conducted an integrated study to comprehensively depict the structural geometry and kinematic evolution in the northwestern Qaidam Basin, northern Tibetan Plateau. The interpretations of seismic reflection data indicate that the Lulehe Formation exhibits different deformation behaviors from the margin to the interior of the Qaidam Basin. By integrating well-logging and core data, we propose a depositional model that attributes the sedimentary facies changes in the upper part of the Lulehe Formation to the main controlling factor of the variable structural styles observed in the study area. Moreover, a detailed analysis of growth strata suggests a southwestward propagation of compressional deformation during the Cenozoic. Notably, this finding offers new insights into the structural evolution in the northwestern Qaidam Basin.

The theory of thrust-related folding has significantly enhanced our comprehension of the kinematic evolution of folds, especially those associated with fault ramps. Despite extensive research into the deformation mechanisms of the fore-limb in the hanging wall folds, the factors influencing back-limb deformation remain relatively underexplored. This study employs a series of discrete-element simulations to investigate the evolution of ramprelated folding, particularly focusing on the factors governing the development of back-thrusts. Comparative analyses reveal diverse deformation styles within the hanging wall of a ramp fold. Notably, when the upper layer exhibits significantly greater strength relative to the lower layer, and an intermediate decollement exists between them, decoupled deformation occurs, characterized by back-thrusting predominantly in the lower layer. This phenomenon is analogous to the deep thrust belts beneath the Shizigou anticline in the western Qaidam Basin, northern Tibetan Plateau, where multiple hydrocarbon-bearing layers have been identified. The findings offer significant insights into the mechanisms of thrust-related folding, thereby improving efficient hydrocarbon exploration in relevant regions. Furthermore, unlike the commonly reported nucleation of a fault ramp from the basal decollement or at an intermediate level, our observations indicate initiation from the shallow section. The detailed mechanism underlying such differential deformation warrant further investigation.

IntroductionThe genesis mechanism of cratonic strike-slip faults in the Sichuan basin is not yet fully resolved, largely due to the lack of comprehensive characterization of fault distribution, which constrains the understanding of the relationship between fault development and tectonic events.MethodIn this study, we supplement extensive three-dimensional seismic data from areas beyond central Sichuan to delineate fault distribution across the entire basin. By integrating these findings with regional tectonic processes, the genesis mechanisms of these faults are proposed.ResultThe results reveal that cratonic strike-slip faults are exclusively concentrated in central Sichuan and the Weiyuan area, with no such faults observed elsewhere in the basin. This spatial restriction suggests that their formation was governed by the unique tectonic evolution of central Sichuan.DiscussionFurthermore, three lines of evidence prove that multi-stage uplifts played a pivotal role in fault development: (1) Faults of varying orientations exhibit distinct development periods, aligning with regional uplift phases; (2) Fault orientations correlate with the bending directions of strata induced by uplifts; and (3) Additional examples of analogous faults in Jurassic strata near the foreland front uplift further corroborate the link between fault orientation and strata bending caused by uplift processes. The central Sichuan region, characterized by superimposed multi-phase paleo-uplift evolution, thus serves as the focal zone for these faults. It is also inferred that the so-called “cratonic strike-slip” fault system in central Sichuan is not a genuine strike-slip system but rather a composite of normal faults with different directions and periods. The genesis of these normal faults is attributed to the tensile strain resulting from strata bending during uplift events. This study not only provides a more comprehensive characterization of fault distribution but also introduces a novel genetic model for these faults, which provides crucial data and new ideas for improving the theory of the fault system within the basins.

Investigating the multi-stage tectonic evolution of fold-and-thrust belts (FTBs) remains a significant challenge. In particular, the evolution of its internal structures and the mechanisms that govern deformation propagation require further research. This study focuses on the Ziliujing anticline located in the southwestern Sichuan Basin, China. It provides an in-depth analysis of the structural development and evolution of the frontal zone of the SW Sichuan FTB, which has propagated from the southeast to the northwest. Through detailed interpretation of seismic reflection profiles and quantitative area-depth-strain (ADS) analysis, we have identified three distinct stages of tectonic shortening corresponding to the Caledonian, Indosinian, and Yanshan-Himalayan orogenic periods. These findings are consistent with the established history of regional tectonic evolution. Furthermore, discrete-element numerical simulations demonstrate that the pinch-out of the basal decollement exerts a significant influence fault development and the formation of overlying fold patterns during multi-stage tectonic deformation. During the initial phase, deformation progressively propagates forward until it reaches the tip of the decollement, where subsequent deformation becomes predominantly localized. The decoupling effect induced by the intermediate decollement facilitates the continued forward propagation of underlying deformation. These insights contribute to a deeper understanding of the multi-stage compressional deformation of salt-bearing fold-thrust belts and the critical factors governing the propagation of deformation from mountain ranges to basins.

Foreland fold-and-thrust belts (FTBs) are shaped by the coupled influence of surface processes (e.g., erosion, sedimentation) and deep geological processes (e.g., plate rheology, flexure and kinematics) across various timescales. These processes record multiple phases of orogenic evolution and are crucial for understanding the interplay between mountain building and the sedimentary basin filling. In this paper, we conducted an integrated study including magnetostratigraphy of exposed strata, detailed field investigations and interpretations of subsurface seismic profiles in the northern Kuqa Depression. This study aims to elucidate the tectonic uplift of the Tian Shan by examining salt-related structures. The present findings reveal that diapirism in the study area commenced in the early Eocene and continued at least into the late Miocene. Notably, the Tuzimaza diapir has been significantly squeezed due to regional contraction since similar to 5.3 Ma. The exposed growth strata were primarily compressional, rather than halokinetic, suggesting the lateral expansion of the Tuzimaza anticline since the latest Miocene (similar to 5.3 Ma). This expansion was a response to the far-field effects of the Indian-Eurasian collision. We propose that the local activation of the Tian Shan likely initiated in the early Oligocene (similar to 34 Ma), with three subsequent episodes of deformation occurring similar to 24 Ma, similar to 10 Ma and similar to 5.3 Ma. The earlier episodes can be attributed to basement uplift in the northern Kuqa Depression, whereas the later episode starting at similar to 5.3 Ma reflects more intensive deformation across the entire foreland, indicative of the steady outward growth of the Tian Shan. Collectively, all these tectonic events have contributed to the formation of the modern Tian Shan.

Figure S1: Uninterpreted long regional seismic reflection images of sections I–V. Figure S2: Nine uninterpreted cross sections of the analog modeling. Figure S3: Uninterpreted seismic reflection section VI in Figure 13B.

Fold-and-thrust belts (FTBs) develop widely in and around active orogenic belts on Earth. With the accumulation of structural shortening, thrust-related folds can grow by increasing their amplitudes and lengths, providing insights into the structural evolution of FTBs. Investigations of fold growth patterns and landscape responses through time and space have important implications for hydrocarbon exploration and geo-hazard assessment. Evidence for lateral fold propagation (i.e., increase in length) usually comes from geochronological constraints based on differences in onset timings along strike. However, these traditional methods are time consuming and economically costly. Alternatively, previous studies have proposed the use of geomorphic features to investigate the lateral fold propagation, including spatial variations in the patterns and densities of river channels, the configuration of the topographic profile along the fold crest, and the occurrence of wind gaps. However, such analyses are based on morphological features of present-day landscapes, which still need process-based vali-dations. Here, we conduct a series of landscape evolution models to reproduce fold growth and their associated geomorphic adjustments. Our results show that deflected rivers and inflected fold-crest elevation profile with decreasing gradient are reliable evidence of lateral fold propagation. The location of propagation is in accordance with the distribution of crest-profile slope breaks and the position where river deflection began. Then, we apply these findings to two natural examples located at the deformation fronts of the Tian Shan (NW China). Results suggest that 1) the Kashi anticline has experienced lateral propagation both westwards and eastwards; and 2) that the Yaken anticline has experienced accelerated tectonic uplift as well as eastwards propagation. These findings are supported by the constraints from geochronological dating and quantitative structural analysis. Future work that integrates folding mechanisms may provide novel insights into landscape response to complex deformation in active FTBs.

利用露头、钻井、地震及大量实验分析资料,从现今地层结构、沉降-沉积速率、古水体盐度、岩石组合及沉积相展布、烃源岩有机质类型等方面,论证了柴达木盆地腹部一里坪坳陷与柴西坳陷之间发育大型水下古隆起,并通过构造解析和古地貌恢复,分析其演化过程,最后从油气成藏角度阐述了古隆起对下一步油气勘探的意义.研究表明:①古新世早期,受早喜马拉雅挤压造山运动影响,形成了古隆起雏形,平面上呈北西—南东向展布,分隔了其东、西两侧的一里坪坳陷与柴西坳陷;始新世至渐新世,古隆起具有很好的继承性,下干柴沟组沉积时期隆起区最大面积约为3 500 km2;至中新世晚期,受柴西沉积中心向东迁移及南北向物源补给的影响,古隆起演变为宽缓斜坡.②古隆起对油气成储、成烃、成藏具有控制作用:古隆起南北两端近物源区发育规模三角洲砂体,而中心主体区远离物源,处于欠补偿咸化水体环境,发育规模湖相碳酸盐岩储层;受古隆起的分隔影响,西侧柴西坳陷下干柴沟组上段—上干柴沟组已证实发育优质咸化湖相烃源岩,东侧一里坪坳陷可能发育有效烃源岩;古隆起是油气运移有利指向区,有利于油气聚集成藏,可作为下一步有利勘探区带.

A set of unique Paleogene-Neogene lacustrine carbonate rocks characterized by deep burial depth, fine grains, thin single layer thickness and high degree of mixing developed in the northwest Qaidam Basin, the main areas for oil and gas exploration. The formation environment and distribution of Paleogene-Neogene lacustrine carbonate rocks are key geological problems need to be solved in oil and gas exploration and development. The reservoir rock types and reservoir space of lacustrine carbonate rocks are studied by drilling core data, thin section and whole rock X-ray diffraction system; Combined with major and trace elements and carbon and oxygen isotopes, the formation environment of Paleogene-Neogene lacustrine carbonate rocks was analyzed; Through the study of sedimentary sequence and sedimentary model, combined with the well connected comparative analysis, the distribution pattern of Paleogene-Neogene lacustrine carbonate rocks is revealed. We identified four kinds of lacustrine carbonate rocks in Northwest Qaidam Basin, including algal dolomite, grain dolomite, sandy dolomite and laminar micritic dolomite, and recognized five types of reservoir space, including trellis pore, dissolution pore, intergranular pore, intercrystalline pore and laminar fracture. The Paleogene-Neogene lacustrine carbonate rocks in Northwest Qaidam Basin were formed in anoxic environment with high paleosalinity. Four typical sedimentary sequences were developed during the decline stage of lake level. The lacustrine carbonate rocks are vertically superimposed and migrated around the center of the lake basin, and horizontally distributed in continuous or intermittent order from the shoreline to the center of the lake. The research results promoted the development of lacustrine carbonate sedimentology, and provided guidance for oil and gas exploration and development, and created significant social and economic benefits.

为明确英雄岭构造带油气成藏条件、探究油气勘探领域及勘探方向,利用钻井油气显示、有机地球化学、铸体薄片鉴定、实验测试、地球物理、试油气等资料,开展英雄岭构造油气成藏条件分析与有利勘探区带预测.结果表明:油气成藏条件上,明确发育多套烃源岩,主要烃源岩分布在古近系下干柴沟组上段、新近系上干柴沟组;存在碎屑岩、湖相碳酸盐岩和混积岩3类油气储集体;形成源储一体型、上生下储型、下生上储型3种源-储组合关系;英雄岭构造带具有烃源岩条件优越、油气资源基础好,储层类型多样、储集性能优越,晚期构造活动与油气生排烃期匹配性好、油气持续充注条件优越等有利的油气成藏条件.有利勘探区带及领域上,提出古近系碎屑岩(三角洲前缘砂体)勘探方向在构造带的花土沟-红柳泉、油砂山-尕斯等地区,碳酸盐岩勘探方向在构造带的英西-游园沟和尕斯-跃进等地区;新近系碎屑岩(滨浅湖滩坝砂)勘探方向在构造带的狮子沟-花土沟-游园沟-油砂山-英东及其以西地区,碳酸盐岩(藻灰岩、混积岩及灰云岩)勘探方向在构造带东侧的油泉子-开特-黄瓜峁等地区.该研究成果表明英雄岭构造带具有多层系、多类型的立体勘探特征,是发现大型油气田的有利勘探区带.

东非陆缘深水盆地具有巨大油气资源潜力,但对陆坡峡谷沉积特征研究较少,制约有利储集层预测.本研究利用三维地震资料,对东非坦桑尼亚滨海盆地陆坡峡谷开展精细研究.结果表明: (1 )研究区陆坡发育多条大型海底峡谷;上陆坡处,坡度较陡,峡谷内以侵蚀作用为主,沉积物主要局限在褶皱推覆带的翼部;褶皱推覆带之外的下陆坡区,坡度变缓,峡谷末端发育席状砂质沉积及砂泥混杂的碎屑流沉积,同时在峡谷北侧发育向北延伸的泥质漂积体;在陆坡边缘,发育海底滑塌,形成块体搬运沉积. (2)峡谷沉积受陆源物质供给、褶皱推覆带、北大西洋底流以及陆坡边界断层等因素控制.受东非裂谷海域分支活动影响,研究区陆架窄、陆坡陡,陆源物质可迅速通过陆架,进入陆坡峡谷:与河流相连的峡谷,物源充足、规模较大,有沉积物发育而没有与河流直接相连的峡谷物源有限、规模较小,峡谷内无明显沉积;褶皱推覆带通过改变海底地形来控制峡谷内沉积分布,褶皱翼部发育沉积,核部则以侵蚀为主;褶皱推覆带外,北大西洋底流与峡谷末端重力流发生交互作用,细粒物质被搬运至峡谷北岸形成漂积体;陆坡边缘断层活跃,峡谷被断层切割,形成断崖,并引发海底滑塌,陆坡处不发育水道及朵体沉积,陆源物质通过峡谷被搬运至更深的深海盆地内.

A number of unidirectionally migrating channels have been interpreted as the result of the interaction between turbidity flows and bottom currents. Based on the analysis of the morphology and internal architecture of channels, different conceptual models of unidirectionally migrating channels were built to reveal the flow process of the interaction between turbidity flows and bottom currents. Most previous studies mainly focused on the straight section of channels, however, the relevant models did not elucidate the flow process in sinuous sections, limiting the knowledge on the formation mechanism and evolution of the whole unidirectionally migrating channels. By using 3D seismic data, the current study not only depicted the geomorphology and internal architecture of a sinuous unidirectionally migrating channels in the Rovuma Basin, offshore Mozambique, but also quantitatively analyzed the flow processes in the straight and bend sections of the channels. The results show that the interaction between turbidity flows and the northward-flowing Antarctic Bottom Water (AABW) led to the unidirectional migration of the turbidite channels. In the straight section of channels, fine-grained material from the upper parts of turbidity flows was deflected northward via flow stripping induced by the AABW, and this material was finally deposited as sandy lateral accretion packages and muddy drifts. The lateral deposits steepened northern channel banks and forced the southward migration of channel axes. However, in the bend section of channels, the upper parts of turbidity flows were forced towards the inner (southern) bank due to the helical flow induced by centrifugal forces, which probably offset the effect of the AABW, and therefore no lateral drifts developed. The effect of bottom currents on turbidity flows is related to the relative direction of turbidity flow and bottom currents. The lateral deposition and corresponding erosion induced by bottom currents influence the formation of the unidirectionally migrating channels, and the channels migrate towards the erosional side but away from the lateral deposition. Our results can help reveal the complete flow processes and sedimentation in the unidirectionally migrating channels in deep water basins around the world.

The Tian Shan is one of the largest and most active intracontinental orogenic belts in the world, which has experienced complex deformation, resulting in the formation of several fold-and-thrust belts (FTBs) in the piedmonts. Investigations on when and how the Cenozoic compressional deformation has reached the leading edge of the FTBs will improve our understanding of the characteristics and mechanism of deformation propagation in contractional orogenic wedges. In this study, we focus on the kinematic evolution of the Nanka (South Kalayuergun) and Yangtake anticlines at the southern limit of the western Kuqa FTB where the Paleocene–Eocene Kumugeliemu Formation (E1–2km) salt has been involved into deformation via the area-depth-strain (ADS) analysis of petroleum seismic reflection profiles. The results indicate that these two detachment folds have experienced two-stage tectonic shortening almost synchronously since the late Miocene, which are in contrast to the previously inferred progressive eastward elongation. The initial age of folding is temporally consistent with that of the Yaken anticline in the eastern sector where the detachment is the Miocene Jidike Formation (N1j) salt, suggesting that salt probably has facilitated the basinward propagation of structural deformation to reach its external pinch-out rapidly. Meanwhile, the salt-lubricated detachment has also promoted the lateral fold propagation, and hence the present length was quickly reached at a very early stage. The simultaneous, episodic deformation at the leading edge demonstrated by our analysis is consistent with the results of analog and numerical modeling, which would further our understanding of structural development and topographic expression in salt-bearing FTBs.

To examine the reservoir type and distribution regularity of high- and stable-yield lacustrine carbonates in the upper Member of Paleogene Xiaganchaigou Formation of Yingxi region and to determine the high-efficiency hydrocarbon exploration direction, the origin and significance of carbonate breccia in this area were investigated based on comprehensive analysis of a large number of well cores, thin sections, rock and mineral testing and log-seismic data. The study reveals that the carbonate breccia has three origins: (1) Sedimentary breccia, formed by the event-related collapse, fragmentation and re-deposition of the early weakly consolidated carbonate rock in the steep slope of underwater paleohighs due to short-term high-energy water body reformation and other geological processes. (2) Diagenetic breccia, with breccia-like structure, formed by deformation or breaking of host rock due to growth of idiomorphic and coarse crystalline gypsum-salt minerals in the weakly consolidated argillaceous carbonate rock of the penecontemporaneous period. (3) Tectonic breccia, can be further divided into fault breccia and interlayer slip breccia according to their occurrence characteristics, both of which are closely related to activity of the Shizigou thrust Fault. With a large number of partially filled pores, vugs and fractures between breccia, the two types of tectonic breccia are high- and stable-yield reservoirs in deep Yingxi region, and may occur extensively under gypsum-salt detachment layers of adjacent areas, so they are the exploration targets in the next step. Sedimentary breccia and diagenetic breccia are of great significance in searching for large-scale carbonate reservoirs.

利用研究区最新的地震和钻井等基础资料,对东非鲁伍马盆地已发现气藏的成藏条件及成藏控制因素进行了分析研究.结果表明,鲁伍马盆地具有良好的油气成藏条件,研究区内烃源岩为裂谷期发育的二叠系—三叠系、侏罗系和白垩系的泥页岩,储层为古近系浊积砂岩,盖层为古近系发育的几套分布广泛的海相泥岩.分析认为构造活动控制了研究区的油气成藏,良好的盖层条件是油气成藏和保存的关键因素.指出构造相对稳定区,特别是受晚期伸展构造影响较弱的陆坡区是优先勘探的方向,区块优选应尽量避开通天断裂发育的区域,同时需要重点对区域盖层条件进行评价.

In this study,we analyzed the variation of salt layer thickness in the leading edge of the western Kuqa fold and thrust belt and its effects on structural style,wavelength and fold lateral linkage of the anticlines using integrated seismic reflection profiles,drilling,remote sensing imagery and DEM data.The results indicate that the initial salt sediments of ～ 1.0 km together with allochthonous salt facilitated the formation of a ～300 km long anticline with wavelengths of ～ 22 km in the Qiulitage structural belt by lateral linkage of individual fold segments with a hinge distance as much as 10.3 km.However,the initial thickness of salt underlying the Kalayuergun structural belt is 0.1～0.9 km,and decreases from west to east.The difference in salt thickness resulted in contrasting fault patterns above the core of anticlines in this belt.As a result,the lateral linkage occurred between Nanka and Zhongka anticlines with a hinge distance of ～ 6.5 km,whereas the Beika anticline developed as an isolated fold even if a shorter hinge distance of ～6.1 km.Therefore,we suggest that the thickness of salt layers resulted in difference of fold wavelength and fault patterns,and further affect whether lateral linkage is able to occur between individual fold segments.Although the results of this study need to be validated by further investigations,we still believe they can help us in better understanding the deformation of compressional salt structures and their controls on fold development.

Based on the field observation and 2D seismic data interpretation, it is illustrated that the basal and intermediate detachment levels developed in NS-trending fold belt in the eastern part of Bengal Basin. The basal detachment level is developed below the whole fold belt, while the intermediate detachment level is only formed in the onshore and shelf area in the north-central segment of the fold belt. The analysis result shows that the intermediate detachment level is primarily controlled by the paleoslope, where mud-rich sediments were deposited, and detachment folds and faulted detachment folds are dominant in the north-central segment, while mud diapirs and mud volcanoes are dominant in the south segment. It is suggested that the differential décollement and structural style of the fold belt in eastern part of Bengal Basin is mainly controlled by the along-strike variations of tectonic shortening, sedimentary processes, and fluid overpressure.