Journal of Earth Science最新文献

This paper coupled a water-air two-phase hydrodynamic (WATPH) model with the Iverson’s method to analyze the influence of the Lisse effect on the fast groundwater pressure (P_w) response and the slope stability. Furthermore, the sensitivities of the driving force and loess soil parameters were investigated. Results showed that the WATPH model simulated the height and rise of the depth to the water table reasonably well. The depth to water table before rainfall (H₀) had a significant impact on the Lisse effect and the slope stability. When the H₀ was less than approximately 1 m, the rainfall triggered a significant Lisse effect and decreased the slope factor of safety (F_s). When the rainfall intensity (R_i) was higher than the saturated hydraulic conductivity (K_s), the Lisse effect and the Fs slightly changed with the increase of the R_i, and the slope tended to be unstable with continuous rainfall. With increasing K_s, the Lisse effect noticeably increased, and the minimum F_s quickly decreases. The analysis of the normalized sensitivity coefficient revealed that H₀ had a dramatic impact on the Lisse effect and loess slope stability. The different R_i and K_s values had prominent influences on the Lisse effect and slight impacts on F_s.

Conodonts, as a biotic group, next to ammonoids, pollen and spores, crustaceans and vertebrates, provide proxy clues for environment and age assessments of the rocks in which they occur. Conodonts are widely used for Triassic marine biostratigraphy. However, there are various discussions about their multielement taxonomy and evolutionary lineages (e.g., generation, speciation). Although first studies reported that most Triassic conodont species were unimembrate, studies carried out in the following years maintained that all Triassic conodonts were multimembrate. Although statistical reconstructions of a number of Triassic apparatuses were attempted, the discovery of fused clusters and natural assemblages has subsequently demonstrated that Triassic conodonts are indeed multimembrate, and all of the elements exist together in the same apparatus. The present paper aims to clarify the evolutionary relationship and array of some Lower Triassic conodonts. Columbitella dagisi n. sp. is described.

If progress is to be made toward improving geohazard management and emergency decision-making, then lessons need to be learned from past geohazard information. A geologic hazard report provides a useful and reliable source of information about the occurrence of an event, along with detailed information about the condition or factors of the geohazard. Analyzing such reports, however, can be a challenging process because these texts are often presented in unstructured long text formats, and contain rich specialized and detailed information. Automatically text classification is commonly used to mine disaster text data in open domains (e.g., news and microblogs). But it has limitations to performing contextual long-distance dependencies and is insensitive to discourse order. These deficiencies are most obviously exposed in long text fields. Therefore, this paper uses the bidirectional encoder representations from Transformers (BERT), to model long text. Then, utilizing a softmax layer to automatically extract text features and classify geohazards without manual features. The latent Dirichlet allocation (LDA) model is used to examine the interdependencies that exist between causal variables to visualize geohazards. The proposed method is useful in enabling the machine-assisted interpretation of text-based geohazards. Moreover, it can help users visualize causes, processes, and other geohazards and assist decision-makers in emergency responses.

The podiform chromitites in the Luobusha ophiolite have been thought to experience a very deep formation, but the maximum depth is still an open issue. Here, we have investigated the structural stability of natural magnesiochromite using the synchrotron-based powder X-ray diffraction and diamond anvil cells up to 48.6 GPa and 2 450 K. The results have shown that spinel-type magnesiochromite first decomposes into corundum-type ‘Cr₂O₃’ + B1-type ‘MgO’ at 11–14 GPa and 1 250–1 450 K, then modified ludwigite (mLd)-type ‘Mg₂Cr₂O₅’ + corundum-type ‘Cr₂O₃’ at 14.3–20.5 GPa and 1 300–2 000 K, and finally CaTi₂O₄-type phase at 24.5 GPa. During the quenching procession from high-temperature-pressure conditions, the mLd-type phase appeared again and was kept at ambient conditions. We also obtained the isothermal equation states of spinel-type and CaTi₂O₄-type phases, revealing the composition effect on their elasticities. Based on the updated results, we propose chromitites could not experience pressure exceeding ∼14.3 GPa (approximate maximum depth ∼400 km) in the subduction-recycling genesis model.

Detrital U-bearing minerals (e.g., zircon, apatite) U-Pb ages with specific trace-element geochemistry, are frequently used in provenance analyses. In this study, we focus on the Yarlung River drainage in South Tibet, characterized by two distinct lithologic units: The Gangdese batholith to the north (mainly granitoids) and the Tethyan Himalaya (mainly sedimentary rocks) to the south, which plays a crucial role in the erosion of the Tibetan Plateau. To constrain the provenance of the Yarlung River Basin, we performed trace-element and U-Pb age analyses of detrital apatite from the river sands of the Yarlung River and its tributaries. Our findings indicate that the detrital apatite U-Pb age patterns of the north tributaries exhibit main peaks at approximately 40 and 60 Ma, consistent with the corresponding U-Pb age patterns of detrital zircon published. Further, their trace element casts fall mainly in the Type I granite region, also indicating the Gangdese arc-dominated source. However, those of the south tributaries (∼60–20 Ma) exhibit a different age distribution from the detrital zircon U-Pb groups (∼110–150, ∼500, and 1 100 Ma), suggesting that the detailed apatite U-Pb signals can provide excellent constraints on the provenance of igneous and metamorphic rock sources but less so for sedimentary rock sources. Combined with previous detrital zircon data in the study area, our detrital apatite information can highlight young metamorphic events from a complex background (i.e., Niyang and Nianchu rivers), which offers additional constraints on the provenance of the Yarlung River Basin. Generally, a combination of geochemistry and geochronology of multi-detrital heavy minerals, such as zircon and apatite, can provide powerful tools for provenance analysis.

Abundant mafic-felsic intrusions distributed in the Altyn Orogen record orogenic histories related to Proto-Tethys and Paleo-Tethys evolution. Zircon U-Pb dating of the intrusive rocks in the eastern Altyn Orogen identifies at least three major tectono-magmatic episodes, yielding ages of ∼426, ∼376–373 and ∼269–254 Ma. The first two emplacement episodes correspond to the post-collisional magmatism in the Altyn Orogen. The ∼426 Ma granitoids possess adakitic characteristics coupled with enriched isotopes, suggesting that they originated from partial melting of thickened lower continental crust induced by upwelling asthenospheric mantle after slab break-off of the South Altyn Ocean Plate. Next, the ∼376–373 Ma mafic-intermediate rocks and coeval granitoids represent a large thermal event that involved mantle melting with induced new juvenile lower continental crust melting in a post-collisional extensional setting. Finally, the ∼254 Ma diabase dykes intruded into the ∼269 Ma granitoids, which were related to the widespread Late Paleozoic magmatism resulting from Paleo-Tethys Ocean subduction. Post-collisional magmatism in the Altyn Orogen significantly enhances understanding of the tectono-magmatic evolution in the northern Tibetan Plateau. The penetrative influence of Paleo-Tethys Ocean subduction was more extensive than previously thought.

The curve of landslide thrust plays a key role in landslide design. The commonly used transfer coefficient method (TCM) and Morgenstern-Price method (MPM) are analyzed. TCM does not take into account the moment balance between slices. Although MPM considers the moment balance, the calculation is complex, and it does not consider that the force between slices may be less than zero at the back edge of the landslide. The rationality and feasibility of the improved MPM are verified by calculating the landslide stability coefficient and landslide thrust at different reservoir water levels. This paper studies the law of landslide thrust when the reservoir water level changes, and discusses the determination of design thrust, to provide a certain theoretical basis for the design of reservoir landslides.

Seismic anisotropy originating within the continental crust is commonly used to determine the deformation and kinematic flow within active orogens and is attributed to regionally oriented mica or hornblende grains. However, naturally deformed rocks usually contain compositional layers (e. g., parallel compositional banding). It is necessary to understand how both varying mineral contents and differing intensities of compositional layering influence the seismic properties of the deep crust. In this study, we analyzed the seismic response of migmatitic amphibolite with compositional banding structures. We present the microstructures, fabrics, calculated seismic velocities, and seismic anisotropies of mylonitic amphibolite from a horizontal shear layer preserved within the Ailao Shan-Red River shear zone, southwestern Yunnan, China. The investigated sample is characterized by pronounced centimeter-scale compositional banding. The microstructures and fabrics suggest that migmatitic amphibolite rocks within deep crust may delineate regions of deformation-assisted, channelized, reactive, porous melt flow. The origin of compositional banding in the studied migmatitic amphibolite is attributed primarily to partial melting together with some horizontal shearing deformation. The microfabrics and structures investigated in this study are considered to be typical for the base of active horizontal shear layers in the deep crust of southeastern Tibet. Seismic responses are modeled by using crystal preferred orientations for minerals of the migmatitic amphibolite by applying the Voigt-Reuss-Hill homogenization method. Calculated P-wave and S-wave velocities are largely consistent in the various layers of the migmatite. However, seismic anisotropies of P-wave (AV_p) and S-wave (AV_s) are higher in the melanosomes (AV_p = 5.6%, AV_s = 6.83%) than those in the leucosomes and the whole rock (AV_p = 4.2%–4.6%, AV_s = 3.1%–3.2%). In addition, there is pronounced, S-wave splitting oblique to the foliation plane in the migmatitic amphibolite. The multiple parallel compositional layers generate marked variation in the geometry of the seismic anisotropy (V_s1 polarization) in the whole rock. Combined with the macroscale geographical orientation of fabrics in the Ailao Shan-Red River shear zone, these compositional banding effects are inferred to generate significant variations in the magnitude and orientation of seismic anisotropy, especially for shear-wave anisotropy (AV_s) in the deep crust. Hence, our data suggest that layering of various origins (e.g., shear layers, partial-melting layers, and compositional layers) represents a new potential source of anisotropy within the deep crust.

The three-dimensional (3D) morphology, anatomy, and in-situ chemical composition analysis of fossils are crucial for systematic paleontology and determining their phylogenetic positions. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), offers valuable structural and chemical information for the analysis of fossils. However, its primary limitation is the restriction to two-dimensional surface data, which limits the exploration of fossils’ 3D complexities. Conversely, 3D X-ray microscopy (3D-XRM), also known as a novel form of micro-computed tomography (micro-CT) facilitates the non-destructive 3D reconstruction of fossil specimens. Nevertheless, it lacks the capability to provide in-situ compositional data. Acknowledging the constraints inherent in these individual techniques, and in response to the evolving requirements of paleontological research, this study introduces an integrated approach that combines 3D-XRM with EDS-coupled focused ion beam scanning electron microscopy (FIB-SEM). This innovative strategy is designed to synergize the advantages of both techniques, thereby addressing challenges that conventional methods cannot. It enables the rapid identification of regions of interest (ROI) within fossil specimens at micrometer resolution. Subsequently, this method collects detailed data on both 3D structures and chemical compositions at the nanometer scale for the identified ROI. This integrated approach represents a significant advancement in paleontological and geological research methodologies, promising to meet the increasing demands of these fields.

Anchor reinforced vegetation system (ARVS) comprises high performance turf reinforcement mats (HPTRM), vegetation and anchors. It is a new attempt to apply the system in expansive soil slope protection. The goal of this paper was to evaluate the effectiveness of ARVS in protecting newly excavated expansive soil slopes. The field tests on the bare slope, grassed slope and ARVS protective slope were carried out, including natural and artificial rainfall. During the test, the soil water content, soil deformation, and anchor axial force were monitored, and then the slope protection mechanism of ARVS was analyzed. It was found that ARVS can effectively protect expansive soil slopes compared with bare slopes and grassed slopes. The vegetation and HPTRM form a reinforced turf, and the anchors fix it to the slope surface, thus restraining the expansion deformation. The axial force on the anchor of ARVS includes frictional resistance and tensile force transmitted by HPTRM, which is maximum at the early stage of support. The neutral point of the anchor of ARVS moves deeper under atmospheric action, but the vegetation and HPTRM on the slope surface can limit this movement.