Table of Content

20 April 2026, Volume 32 Issue 02

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Comparative Analysis and Mechanistic Insights into Marine Productivity in the South China Sea during the Last Glacial Maximum and the Holocene

HUANG Feiyu, ZHANG Chengjun, ZHU Huaxi, XU Xudong, HU Rong

2026, 32(02):  129-142.  DOI: 10.16108/j.issn1006-7493.2025030

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Marine biological productivity is a key factor regulating the export and burial of organic carbon, and its long-term
evolutionary patterns are of great significance for understanding the interaction between the carbon cycle and climate change. The South China Sea (SCS), as the largest marginal sea in the western Pacific, exerts profound impacts on regional carbon budgets and ecosystem structures through its productivity variations. Although productivity evolution in the SCS since the Last Glacial Maximum (LGM) has been extensively studied, results from different subregions exhibit remarkable spatial heterogeneity. These discrepancies may arise from the heterogeneous response of different regions to climate change, and/or inherent ambiguity of productivity proxies coupled with their susceptibility to potential post-depositional diagenetic alterations. In this study, we systematically reviewed the applicability and implication of commonly used productivity proxies in the SCS, including fluxes of total organic carbon, C37 alkenones and opal, as well as benthic foraminiferal assemblages. Based on a comprehensive evaluation of these proxies, we compared and analyzed the productivity evolution patterns of the SCS during the LGM and the Holocene. The results show that the gross productivity in the northern, southeastern part of the SCS and areas surrounding the Sunda Slope was generally higher during the LGM and lower in the Holocene. In contrast, the southwestern to central-southern parts of the SCS exhibited lower productivity during the LGM compared to the Holocene. The pattern of productivity evolution is likely primarily influenced by local hydrological processes regulated by the combined effects of monsoon dynamics and sea level changes. This study not only offers crucial insights into the coupling mechanisms between monsoon and productivity on glacial-interglacial timescales, but also provides a scientific basis for predicting responses of marginal sea carbon cycle under future global warming scenarios. 

Last Deglaciation Stalagmite δ¹⁸O_c and Regional Precipitation Change in Southern China：Climate Model-Reconstrution Data Comparisons

JIA Ruiyun, SHAO Xiaohua, ZHANG Xiao

2026, 32(02):  143-151.  DOI: 10.16108/j.issn1006-7493.2025026

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The stalagmite δ¹⁸O_c records from southern China serve as a crucial paleoclimate archive for reconstructing orbitaland millennial-scale variations of the Asian monsoon system. Nevertheless, the precise linkage between these δ¹⁸O_c signals and regional precipitation remains debated, posing challenges for both the climatic interpretation of δ¹⁸O_c variations and investigations of driving mechanisms of monsoon variations. This study synthesizes published stalagmite δ¹⁸O_c records (21-11 ka B.P.) from southern China with HadCM3B model simulations to examine the δ¹⁸O_c -precipitation relationship during the last deglaciation. Our analysis reveals distinct scale-dependent relationships: on orbital timescales, the δ¹⁸O_c variations reliably track long-term changes in summer precipitation, while millennial-scale δ¹⁸O_c fluctuations primarily reflect variations in annual precipitation. The transition from glacial to interglacial conditions is marked by progressively depleted δ¹⁸O_c values, corresponding to increasing summer rainfall. In contrast, during abrupt climate events such as YD and HS-1, enriched δ¹⁸O_c values coincide with enhanced annual precipitation. Through comparative analysis of δ¹⁸O_p anomalies with the precipitation-weight and stalagmite δ¹⁸O_c anomalies, we demonstrate that while the aforementioned relationships exist across different timescales, stalagmite δ¹⁸O_c cannot be unambiguously interpreted as a direct proxy for either summer or annual precipitation amounts. 

Investigation of Refined Monitoring Methods for Tunnel Convergence Deformation under Complex Geological Conditions

TANG Zian, ZHANG Chengcheng, GUO Junyi, JIA Lixiang, SHI Bin

2026, 32(02):  152-159.  DOI: 10.16108/j.issn1006-7493.2025033

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Tunnel convergence deformation is the key points of monitoring，serves as a critical indicator of the interaction
between surrounding rock and supporting structures, directly reflecting rock mass stability and the mechanical performance of the support system. Accurate and real-time monitoring of this deformation is essential, especially under the complex geological conditions. However, conventional monitoring techniques, which primarily rely on manual measurements and simple instruments, often fall short in precision and continuity. Distributed optical fiber sensing technology, with its advantages such as long distance, good durability, strong anti-interference ability and the ability to achieve real-time monitoring, provides a new technical means for the precise monitoring of tunnel convergence deformation. This study presents a novel method for distributed fiber optic sensingbased monitoring of tunnel circumferential convergence, incorporating an optimized cable deployment strategy and a strain-todisplacement inversion algorithm. Laboratory model tests were conducted to validate the feasibility and accuracy of the proposed approach. The results demonstrate that the method can effectively identify deformation zones and assess the overall stress distribution based on strain profile analysis. The use of a dual-cable layout minimizes computational assumptions and enables direct conversion of strain data into point displacements, offering high efficiency and reliable accuracy. The monitoring accuracy is primarily influenced by the design and installation quality of the sensing setup. Enhancements in device stability, reduction of optical loss, and improved fixation techniques are shown to further increase measurement precision. The findings provide a novel approach for refined monitoring of tunnel deformation under complex geological conditions. 

Numerical Simulation of Pumping-induced Land Subsidence with the Consideration of the Role of Diaphragm Wall

XU Shengjie, ZHANG Yun, MIAO Chenyang

2026, 32(02):  160-169.  DOI: 10.16108/j.issn1006-7493.2025028

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Underground structures affect the land subsidence by changing the groundwater seepage and soil deformation. Based on the direct shear test of the soil-concrete interface, this study analyzes the influence of soil composition and moisture content on the interface friction angle and cohesion. Combined with the constitutive model of the interface between the soil and the concrete, the hydraulic and mechanical coupled model was employed to simulate the land subsidence. The results show that the shear stressdisplacement curve of the interface exhibits strain hardening characteristics and conforms to a hyperbolic curve. The clay particle contents and moisture contents have clear effects on the interface shear strength parameters. With the width and insertion depth of the baffle increasing，the water-blocking effect enhances, inducing an increase in the maximum subsidence. Baffles in soils can block water flow and hinder the soil displacement at the same time, thus the maximum subsidence first increases and then
decreases with the increasing distance between the baffle and the pumping well. 


Shear Strength Properties of Polymer Fiber-Modified Cement Loess

MA Chen, XIE Wanli, HUO Kaizhi, YUAN Kangze, LIU Qiqi, DI Shengjie, ZHANG Ying

2026, 32(02):  170-178.  DOI: 10.16108/j.issn1006-7493.2025025

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As a typical poor foundation soil, the collapsibility and structural fragility of loess significantly restrict the safety of
the project, although the traditional cement curing effectively improves the mechanical properties, it is accompanied by high carbon emissions, and the green improvement technology needs to be improved urgently. In this paper, the direct shear test and scanning electron microscopy (SEM) analysis were carried out to systematically explore the effects of fiber content on their strength deformation characteristics and microstructure, and to evaluate their carbon emission reduction potential. The test results show that the fiber significantly enhances the shear performance of loess, and the cohesion is mainly improved. The cohesion showed a trend of “first increasing and then decreasing” with the increase of the content, and the optimal content was 0.5% for polypropylene fiber and 0.4% for polyester fiber, respectively. The microscopic analysis reveals that the fiber can fill the pores and enhance the structural compactness, and the friction effect and network restraint mechanism at the interface between the fiber and the soil can effectively impede deformation and inhibit crack propagation. In addition, introduction of fiber can replace part of cement consumption, and the carbon emission is reduced by about 50% compared with traditional curing solutions. This study provides a theoretical basis and engineering support for the low-carbon improvement of loess.

Intelligent Identification of Mid-Holocene Ancient Dams Based on Deep Learning: A Case Study of Liangzhu Ancient City and Its Surrounding Areas

WANG Yiran, DONG Shaochun, WANG Xiaoqi, YIN Hongwei, ZHANG Yixin, ZHANG Tao

2026, 32(02):  179-191.  DOI: 10.16108/j.issn1006-7493.2025029

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Since the Middle Holocene, multiple ancient civilizations in the middle and lower reaches of the Yangtze River have constructed ancient dams for flood control and irrigation as a response to environmental changes. However, due to erosion, sedimentation and human activities, it is difficult for traditional archaeological methods to quickly identify and discover these ancient dams, which restricts the development of hydraulic archaeology. This paper proposes an efficient method for large-scale identification of ancient dams based on historical remote sensing images and deep learning technology, and evaluates the method by taking the ancient dams in Liangzhu Ancient City and its surrounding areas as research cases. This method collects aerial and satellite images from the 1940s to 1970s, labels 132 confirmed ancient dams in the study area, selects the YOLOv5 as the basic architecture, and optimizes the model by introducing the Generalized Intersection over Union (GIoU) loss function, coordinate attention mechanism and supplementary detection layer. The results show that the optimized model achieves a recall rate of 70% and a precision of 68% for ancient dams in the study area, which is significantly higher in efficiency and accuracy than traditional visual interpretation and field archaeological methods. This method provides an automatic tool for large-scale census of ancient water conservancy facilities, and is of great significance for revealing the spatio-temporal evolution characteristics of ancient water conservancy facilities, clarifying the human-land relationship model in which ancient people actively responded to environmental changes by constructing water conservancy projects under the background of climate change, and understanding the development process of ancient civilizations. 

Vanadium Isotope Fractionation in Igneous Rocks: Controls of Mineral Crystallization and Oxygen Fugacity

YAN Jinyi, DING Xin, LIU Chengyihong, CHEN Zhenwu, HUANG Fang

2026, 32(02):  192-206.  DOI: 10.16108/j.issn1006-7493.2025036

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Vanadium (V) is a redox-sensitive element, and its valence is controlled by the environmental redox conditions. In
recent years, the advancement in MC-ICP-MS analytical techniques has enabled the precise identification of subtle V isotope fractionation in igneous systems. As a result, V isotopes have shown great potential in the study of high-temperature geological processes. Understanding the mechanism of V isotope fractionation during igneous evolution is fundamental to their application in high-temperature geochemical research. This paper reviews the research findings on V isotopes in igneous rocks and points out that mineral crystallization and oxygen fugacity are the main factors controlling V isotope fractionation. Studies have shown that the separation crystallization of silicate minerals can alter V isotope composition of the melt. Moreover, Fe-Ti oxides are key factors controlling V isotope fractionation, and their separation crystallization can lead to an increase in the δ51V value of the residual melt. Additionally, while previous studies suggested that the V isotopes of primitive basalts are not sensitive to changes in oxygen fugacity, recent views indicate that there is recognizable V isotope fractionation at lower degrees of partial melting and higher oxygen fugacity. Based on this, this paper summarizes the applications of V isotopes as follows: in tracing crustal evolution, V isotopes have allowed to establish a close link between felsic continental crust and plate tectonics; in constraining the formation of layered intrusions, V isotopes reveal an evolutionary path from primitive magmas to highly differentiated products; and in tracing mantle-derived magma sources, V isotopes suggest that partial melting and fractional crystallization jointly dominate the transformation of carbonate melts into alkaline basalts. These studies fully demonstrate the great potential of V isotopes in the study of high-temperature geological processes.

Mineralogical and Chemical Characteristics and Tectonic Significance of Gabbro from the Dachadaban Area, North Qilian, China

ZHANG Zhiguo, LIU Xijun , Gong Xiaohan, TANG Guoqiang, WANG Jiating, TIAN Hao, CAO Yuzhao, DUN Hailong

2026, 32(02):  207-224.  DOI: 10.16108/j.issn1006-7493.2025035

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Gabbro is a major component of oceanic crust and is of great significance for understanding the magma processes beneath different types of spreading ridges and their corresponding relationships with tectonic settings. This study systematically investigates the petrology, mineralogical and geochemistry of the gabbro bodies in the Dachadaban ophiolite in the North Qilian Orogen. Petrographic results show that these medium-fine-grained gabbros are mainly composed of plagioclase (around 60 vol.%), clinopyroxene (around 35 vol.%) and orthopyroxene (around 5 vol.%). Geochemical characteristics inidcate that the gabbros exhibit high-Mg features (MgO=8.90%-11.33 wt.%, Mg^#=76-80), with low-Ti (TiO₂=0.36%-0.49 wt.%) and low- Si (SiO₂=47.10%-47.94 wt.%) contents, while their CaO content is comparable to that of mid-ocean ridge basalt (MORB). Furthermore, these gabbros display extremely low rare earth element (REE) abundance with pronounced light REE (LREE) depletion, along with depletion in high field strength elements (HFSEs; e.g., Zr, Hf, Ti) and enrichment in large ion lithophile elements (LILEs). The overall composition of these entire rocks is similar to that of the back-arc basins. In terms of mineral composition, clinopyroxenes belong to diopside (Mg^#=78-80) with a distribution pattern of light rare earth element depletion, indicative of the differentiation products of MORB-type magma. The calculation of mineral equilibrium temperature and pressure yields that the crystallization temperature of gabbro is 1200-1246℃ , the pressure is 5.6-8.9 kbar, and the corresponding depth is 15-29 km, indicating characteristics of a deep magma chamber. Together with the previous results, the study suggests that the Dachadaban gabbro was formed in a back-arc basin setting.

Application of Ecological Modeling in Deep-time Paleophytogeography Reconstruction

LI Tairan

2026, 32(02):  225-243.  DOI: 10.16108/j.issn1006-7493.2025031

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As crucial components of terrestrial ecosystems, plants provide a critical window for revealing the evolutionary patterns of terrestrial ecosystems through studies of their spatiotemporal distribution on deep-time Earth’s surfaces. By analyzing the response of paleoflora to ecological environmental changes, we can not only elucidate the dynamic evolutionary patterns of regional plant communities but also reconstruct the structure and evolutionary mechanisms of entire terrestrial ecosystems during geological history. The construction of ecological models, based on analyzing how plant traits, habits, and distributions are influenced by ecological factors, demonstrates advantages of high research precision, effective visualization, and user-friendliness, playing a significant role in deep-time paleophytogeographic reconstruction. This study focuses on three representative ecological models: the Biome model, the SEG model, and the Eco-Plant model. By employing plant macrofossils and microfossils from the Changhsingian-Induan interval as case studies, we systematically elucidate the relationship between vegetation ecology and climate evolution through the application of the Eco-Plant model. Finally, addressing current challenges in deep-time paleophytogeographic reconstruction, we propose a multi-source data integration strategy to further advance the application of ecological models in reconstructing ancient plant geographic distributions across geological timescales. 


Evaluation of Karst Development Degree in Engineering Construction Area Based on Comprehensive Exploration and Combined Weighting Method

LUO Zhenjiang, ZHAO Zhenhua, HAN Lin, LI Yueheng, SUN Hongjie, LIN Guangqi, BAI Sichu, JI Mengqi

2026, 32(02):  244-255.  DOI: 10.16108/j.issn1006-7493.2025032

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The evaluation of regional karst development degree can provide a reference basis for the prevention and control of
geological disasters and the planning of construction in karst areas. However, conventional single-method drilling and geophysical exploration techniques have limitations and cannot fully reveal the spatial characteristics and distribution patterns of karst development from a holistic perspective. This can lead to significant safety risks in engineering construction within such regions. Taking a residential construction area in Niuquan Town, Laiwu District, Jinan City as an example, high-density resistivity, microdynamic spectrum ratio and electromagnetic wave CT were used to perform a comprehensive and detailed geophysical exploration analysis of karst features. Based on the geological drilling data, a three-dimensional geological structure visualization model of the study area was established. Through the comprehensive interpretation of geophysical exploration and the three-dimensional geological structure model, the karst development characteristics and distribution patterns of the study area were fully revealed. Meanwhile, the improved CRITIC subjective-objective combined weighting method was adopted to conduct a comprehensive evaluation of the karst development degree in the study area. The results show that the integrated exploration methods and the three-dimensional geological structure model established based on borehole data mutually complement and verify each other, robustly revealing the developmental characteristics and patterns of underground karst in the study areaincluding its formation locations, overall scale, distribution morphology, spatial extent, and connectivity. The combined weight of the evaluation indicators influencing the degree of karst development, from the largest to the smallest, are as follows: the distribution density of karst caves, the distribution of soluble rocks, the type of soil layer structure, the thickness of the Quaternary strata, and the thickness of the Paleogene non-soluble rocks. The study area is categorized into three types: highly developed karst zones, moderately developed karst zones, and underdeveloped karst zones with areas of 7,939.325 m², 17,737.1347 m², and 36,169.07 m², respectively. The highly developed karst zones are predominantly located in the southeastern part of the study area. The research methods and conclusions provides a reference for site selections of engineering projects in karst areas.