Accurately delineating the spatial distribution and geometric scale of active faults is essential for understanding crustal deformation and assessing regional seismic hazards. While the Altyn Tagh Fault (ATF) has been extensively studied, its adjacent secondary structures—such as the Baiganhu Fault—remain poorly constrained regarding their geometry, slip history, and seismic potential. This study aims to systematically characterize the offset geomorphology of the Baiganhu Fault, establish its segmentation, and evaluate its potential for generating large earthquakes, including multi-fault cascading ruptures with the ATF.

Using multi-source high-resolution satellite imagery and digital topographic data, we conducted detailed geomorphic mapping of the Baiganhu Fault. Displaced landforms (e.g., offset gullies, alluvial fans, pressure ridges, and sag ponds) were measured. We constrained displacement variations at individual measurement points using Gaussian cumulative probability density (COPD) distributions to interpret the displacement accumulation pattern and evaluate coseismic slip.

The Baiganhu Fault extends for approximately 247 km along a general northeast–east (NEE) strike, displaying prominent left-lateral strike-slip geomorphic features. Based on fault geometry and deformation patterns, it is divided into western, central, and eastern segments. The central segment hosts a well-preserved ~50-km-long surface rupture zone with an average coseismic displacement of 4.8 m. Statistical analysis of 99 offset gullies yields an average horizontal offset of 4.3–4.8 m for the most recent event, corresponding to a moment magnitude of M_W 7.4±0.3. A full-segment rupture could generate an earthquake of M_W 7.8±0.3. Furthermore, the ~5-km-wide stepover separating the Baiganhu Fault from the main strand of the ATF is unlikely to act as a permanent barrier, making a cascading rupture mechanically plausible.

The Baiganhu Fault is a highly active left-lateral structure capable of generating M_W 7.4 events. Regional seismic hazard models must incorporate the scenario of cascading ruptures between the Baiganhu Fault and the Altyn Tagh Fault to avoid underestimating seismic risk to surrounding infrastructure.

This study provides critical quantitative constraints on the geometry, slip behavior, and seismic potential of a previously under-studied secondary structure within the ATF system. By highlighting the potential for multi-fault cascading ruptures, our findings underscore the need to update regional seismic hazard models, which is vital for risk mitigation and infrastructure safety in the region.

Seismically triggered soft-sediment deformation structures (SSDSs) in the lacustrine sediments serve as reliable stratigraphic records for studying paleoearthquake events in tectonically active regions. Load and ball-and-pillow structures, as common types of SSDSs, are generally attributed to gravitational instability caused by an inverse density gradient between adjacent sedimentary layers. However, their formation mechanisms and the quantitative relationship between their development and seismic intensity remain poorly constrained.

This study employs the multiphase-flow numerical simulation approach implemented in ANSYS Fluent to simulate the formation of load and ball-and-pillow structures in saturated sand–clay layers under different peak ground accelerations (PGAs; 0.125g, 0.25g, 0.5g, and 0.8g) and varying physical properties, including density, dynamic viscosity and layer thicknesses). The effects of sediment physical properties on the development of these deformation structures and their relationship with seismic intensity were investigated.

The results show that as the PGA increases, load and flame structures develop earlier at the sand–clay interface and progressively evolve from small load structures into larger-scale load and ball-and-pillow structures. Under the same PGA, a larger density contrast, a smaller dynamic viscosity contrast, and a thicker overlying sand layer result in greater deformation and larger-scale development of load and ball-and-pillow structures.

The morphologies of the load and ball-and-pillow structures produced by the numerical simulations are highly consistent with those observed in lacustrine sediments in the Tashkorgan area. This agreement supports the proposed mechanical mechanism of their formation and provides a quantitative basis for understanding the development of SSDSs under different seismic and sedimentary conditions.

This finding verifies the seismic trigger of SSDSs in this region and provides a new technological insight into the study of SSDSs and paleoearthquakes.

The Yangtze Block was a crucial component of the Gondwana supercontinent. During the Ediacaran–Early Cambrian, its western margin underwent a marked transition from carbonate- to siliciclastic-dominated depositional environments. However, the tectonic dynamics and geotectonic setting governing this pronounced sedimentary facies shift remain poorly constrained. Thick Lower Cambrian terrigenous clastic rocks widely exposed along the western margin of the Yangtze Block (Western Yangtze) serve as a key archive for tracing sediment provenance and deciphering Early Cambrian geotectonic evolution.

This study presents systematic detrital zircon U–Pb geochronological and whole-rock major- and trace-element geochemical analyses of the Lower Cambrian Qiongzhusi Formation in the Western Yangtze to constrain its provenance and tectonic background.

Whole-rock geochemical data indicate that high-field-strength elements (HFSEs) and large-ion lithophile elements (LILEs; e.g., Th, Zr, Hf, Ba, Pb) in the Qiongzhusi Formation clastic rocks align closely with upper continental crust (UCC) values. Conversely, elements such as Co, Ni, Y, Nb, Cs, Hf, and Ta are depleted relative to UCC, with Co, Cs, and Ta showing the most significant depletion. Characteristics of immobile elements (Th, Sc, Hf, Zr, Ho) and rare earth elements (REEs; e.g., La, Ce, Yb) consistently indicate a predominantly felsic igneous source. Detrital zircon U–Pb age spectra exhibit two primary population peaks at ca. 590–500 Ma and ca. 880–720 Ma, alongside two subordinate clusters at ca. 1900–1500 Ma and ca. 2500–2400 Ma.

Integrated with regional geological evidence, we propose that the Early Cambrian detritus was primarily derived from Ediacaran–Early Cambrian magmatic rocks within the Longmenshan tectonic belt, as well as weathering products of late Neoproterozoic felsic magmatic rocks from the Panxi–Hannan and Ailaoshan magmatic arcs. Subduction of the Proto-Tethys Ocean beneath the Western Yangtze during the latest Ediacaran–Early Cambrian established a Late Ediacaran–Early Cambrian magmatic arc. This tectonic event converted the Western Yangtze from a passive margin into an active continental margin, supplying voluminous Early Cambrian detritus that drove the major depositional transition from carbonates to siliciclastics. [Significance]These findings establish key provenance links between the Western Yangtze and surrounding orogenic belts, providing critical constraints for reconstructing the tectonic and paleogeographic evolution of the South China Block during the Ediacaran–Early Cambrian transition.

The dolomite in the Ordovician Kelimoli Formation of the complex tectonic zone along the western Ordos Basin margin is a high-quality reservoir for natural gas exploration. However, its genetic mechanism and the relationships among the sedimentary environment, multi-stage tectonic superimposition, and diagenetic alteration remain controversial, limiting effective guidance for oil and gas exploration.

To elucidate the genesis of this dolomite, a comprehensive analytical approach was applied, incorporating thin-section petrography, cathodoluminescence (CL), C–O isotopes, X-ray diffraction (XRD) ordering degrees, trace and rare earth element (REE) geochemistry, and Sr isotopes, integrated with regional tectonic evolution.

Under CL, the dolomites generally exhibit weak dark-brown luminescence with distinct zonation, alongside authigenic quartz and saddle dolomite, indicating hydrothermal involvement and multi-stage recrystallization during deep burial. Carbon and oxygen isotopic signatures further support a burial origin. XRD data reveal a relatively low ordering degree in dolomites, which decreases with increasing temperature, suggesting rapid crystallization under elevated temperatures. REE patterns display positive Ce and Eu anomalies, indicating that dolomitization occurred in a relatively closed, high-temperature, and high-pressure diagenetic system via internal fluid readjustment and material redistribution. Overall, the dolomite shows a relatively low degree of order, and the order decreases with higher temperatures, suggesting that the dolomite formed in an environment with relatively high temperature and rapid crystallization rate. Geochemically, lower Sr contents correlate with higher Fe and Mn concentrations, reflecting multi-stage superimposed alteration under deep burial conditions. Furthermore, strontium isotope values of medium-to coarse-grained dolomite closely approach average crustal values, likely influenced by crustal Sr transported along coeval tectonic conduits.

This research attributes the dolomite formation primarily to deep burial and the coeval superimposition of tectonic fluid modification. The origin and evolution of the Ordovician Kelimoli Formation dolomite were strongly controlled by deep fault systems. During the co-deposition period, this fault system controlled the development of high-energy terraces. In the subsequent tectonic activity phase, the deep fault system became a fluid migration channel, facilitating the superimposed modification of dolomite bodies.

The research results provide fundamental support for the efficient exploration of oil and gas resources.

Columnar joints in basalt are typical structures formed during magmatic cooling and contraction. However, their formation mechanisms, internal structural characteristics, and cooling histories remain debated. This study aims to constrain the internal structures and cooling histories of large-diameter basalt columns through integrated rock magnetic and paleomagnetic analyses.

Detailed rock magnetic and paleomagnetic analyses were conducted on 49 oriented samples collected from two Pliocene basalt columns, each reaching up to 1.5 m in diameter, in the Bo Phloi section, Kanchanaburi, Thailand. Rock magnetic experiments included hysteresis-loop measurements, isothermal remanent magnetization (IRM) acquisition, first-order reversal curve (FORC) analysis, anisotropy of magnetic susceptibility (AMS) measurements, and temperature-dependent magnetic susceptibility measurements. Stepwise thermal demagnetization was performed to isolate stable components of remanent magnetization.

Hysteresis loops and IRM acquisition curves indicate that the magnetic assemblage is dominated by pseudo-single-domain (PSD) titanomagnetite grains, with magnetic saturation reached at fields below approximately 300 mT. The two-stage increase in IRM acquisition with increasing field suggests contributions from magnetic components with different coercivities. FORC diagrams further support the predominance of PSD magnetic grains and reveal systematic differences between the margins and interiors of the basalt columns. For both basalt columns, AMS results show sub-vertical minimum susceptibility axes (K₃) and sub-horizontal maximum (K₁) and intermediate (K₂) axes, with generally low degrees of magnetic anisotropy (P_j < 1.05). These AMS fabrics indicate a primary near-horizontal magma-flow fabric during emplacement, but provide no evidence for vertical melt migration or internal convection. AMS parameters also reveal systematic spatial variations. Samples from the column margins exhibit lower magnetic susceptibilities (χ), lineation (L), and anisotropy degree (P_j) values and are predominantly characterized by oblate fabrics (T > 0), whereas interior samples show higher χ, L, and P_j values and predominantly prolate fabrics (T < 0). These differences reflect contrasting cooling conditions between the margins and interiors of the basalt columns. The margins cooled more rapidly, leaving less time for magnetic minerals to crystallize, grow, and develop preferred orientations. In contrast, the interiors cooled more slowly and likely remained at elevated temperatures in a plastic or partially molten state for longer periods, allowing magnetic minerals to crystallize, become concentrated, and develop preferred orientations under thermal contraction stresses. Paleomagnetic results indicate that stepwise thermal demagnetization isolates a stable, single-component remanent magnetization carried by PSD titanomagnetite. Six marginal samples from basalt column A exhibit relatively scattered virtual geomagnetic pole (VGP) distributions and anomalous directions, whereas the remaining 43 samples show relatively clustered VGPs after tilt correction. Systematic variations in remanent magnetization directions and VGPs indicate that cooling did not proceed symmetrically or uniformly from the column margins toward the cores. Instead, the columns appear to have undergone an asymmetric, unidirectional regional cooling process, possibly influenced by a localized heat source.

Integrated rock magnetic and paleomagnetic analyses lead to the following conclusions: (1) The basalt columns in Kanchanaburi are dominated by PSD titanomagnetite. Their AMS fabrics, characterized by subvertical K₃ axes and subhorizontal K₁ and K₂ axes, record a primary near-horizontal magma flow during emplacement. (2) The column margins cooled more rapidly, resulting in finer magnetic grains, lower magnetic anisotropy, and predominantly oblate fabrics, whereas the interiors cooled more slowly, allowing magnetic minerals to crystallize, grow, and develop stronger preferred orientations, resulting in higher anisotropy and predominantly prolate fabrics. (3) Systematic variations in paleomagnetic directions and VGPs among the 49 samples indicate that post-jointing cooling was neither uniform nor symmetric but instead proceeded asymmetrically and unidirectionally across the basalt columns.

These findings contribute to a better understanding of the cooling processes of basaltic lava and provide new insights into long-term variations in the geomagnetic field.