Carbon dioxide (CO₂) storage in underwater reservoirs is a valuable method of reducing carbon emissions. Saline aquifers such as those in the South Yellow Sea Basin (SYSB), China, have great potential for geological CO₂ storage. Thus, we use the recommended calculation method of USDOE and a formation volume model to determine the geological conditions for CO₂ storage and estimate the CO₂ storage capacity of the Cenozoic saline aquifers in the SYSB (depth: 800–3200 m). Overall, the SYSB exhibits weak fault activity and seismicity, medium and low geothermal fields, four types of source sandstone reservoir, and four sets of carbon reservoir–caprock assemblages developed from the Cenozoic strata, providing relatively good geological conditions for CO₂ storage. The estimated capacity of the Cenozoic strata ranges from 39.59 Gt to 426.94 Gt (average: 155.25 Gt), indicating an extensive storage capacity that can meet the carbon sequestration needs of Shandong and Jiangsu Provinces for approximately 89 years. The Yantai Depression has a lower geothermal gradient and terrestrial heat, weaker seismic activity, and double the storage capacity of the Qingdao Depression, indicating that it is the most suitable area for Cenozoic CO₂ storage in the SYSB, whereas the Laoshan Uplift is not suitable for storage. This study provides a scientific basis for the selection of offshore CO₂ storage sites.

The southern continental margin-slope area of the South China Sea is a complex passive continental margin with diverse tectonic structures and movements. This area is rich in gas hydrate resources and is also an area with a high incidence of potential geological hazards. Identifying and understanding the potential submarine geological hazards in this area is very important for disaster prevention and management during the future exploration and development of marine resources. In this paper, five types of potentially hazardous geological bodies are identified in the research area through high-precision two-dimensional seismic processing and interpretation, including submarine mounds, pockmarks, mass transport deposits, submarine collapses and faults. At the same time, the seismic reflection characteristics and the changes in its morphology and surrounding strata are described. In addition to the causes of geological hazards in this region and their influence on exploration and development, the research prospects of geological hazards in this region are also suggested. Special tectonic and sedimentary conditions, fluid activities and hydrate decomposition may be the conditions for geological hazards in this region, which pose a significant threat to the exploration and development of seabed resources and marine engineering construction in this region. Not only does our conclusion provide useful data for the development and utilization of gas hydrate, but it also presents theoretical suggestions for reducing geological hazards in the development process.

Deep sea water (DSW) is a globally utilized source of renewable energy and other resources. To understand the characteristics of DSW resources in the South China Sea, in July 2022, the Guangzhou Marine Geological Survey (GMGS) investigated temperature, salinity, pH, dissolved oxygen (DO), inorganic salts (DIN, PO₄³⁻-P, and SiO3-Si), heavy metals (Hg, Pb, As, and Cd), trace elements (Cu, Zn, Fe, Mn, Ni, Se, and Mo), and other related indicators. The results of this investigation elucidate the horizontal and vertical changes in the physical and chemical properties of deep sea water in the Xisha Sea. The surface seawater quality in Xisha was found to be excellent and to meet first-class seawater survey standards. However, the concentrations of various nutrient salts in the surface layer were relatively low. As the seawater depth increased, different trace elements and heavy metals exhibited variations, and the concentrations of various nutrients also gradually increased.

As a core component of carbon capture, utilization and storage (CCUS), CO₂ geological storage is critical to China’s carbon neutrality strategy. However, current assessments of China’s CO₂ geological storage potential suffer from substantial numerical discrepancies, and single evaluation methods lack sufficient reliability, constraining the scientific formulation of national CCUS planning. Addressing these deficiencies, this study proposes a comprehensive evaluation framework to integrate multi-source results and derive a robust quantitative range of national CO₂ storage potential. A weighted calculation method covering four criterion layers and 15 evaluation factors is developed in this work. From four perspectives of data authority, temporal validity, methodological reliability and regional comprehensiveness, nine representative evaluation datasets are systematically scored to determine their respective comprehensive weights. Combined with the weighted average model, China’s national CO₂ geological storage potential is quantified at 1786–2669 Gt. This multi-source fusion result avoids the inherent limitations of single-method evaluation. This study achieves the effective integration of heterogeneous multi-source evaluation data, resolving the inconsistency in existing national potential assessments. The estimate, while robust under the present validation, remains subject to inherent uncertainties and should therefore be interpreted with due caution in supporting CCUS decision-making.

The northwestern slope of the Dongdao Platform in the Xisha Sea exhibits a complex geomorphological structure. Utilizing high-resolution multibeam bathymetric data and 2D seismic profiles, this study systematically reconstructs the slope morphology and its evolutionary processes. The study area displays a distinct threefold zonation: the upper slope (160–700 m water depth) has a steep gradient of 15°–25°, characterized by deeply incised V-shaped channels and slump deposits, primarily shaped by gravity-driven erosion; the middle slope (700–1200 m water depth) features a gentler gradient of 10°–15°, where channels stabilize, adopting U-shaped cross-sections with the development of lateral accretion deposits; the lower slope (1200–1500 m water depth) exhibits a milder gradient of 5°–10°, dominated by a mixture of fine-grained carbonate sediments and hemipelagic mud–marine sediments originating partly from the open ocean and partly from the nearby continental margin. The slope extends from 160 m to 1500 m water depth, hosting the C1–C4 channel system. Seismic facies analysis reveals mass-transport deposits, channel-fill facies, and facies modified by bottom currents—currents near the seafloor that redistribute sediments laterally—highlighting the interplay between fluid activity and gravity-driven processes. The slope evolution follows a four-stage model: (1) the pockmark formation stage, where overpressured gas migrates vertically through chimneys, inducing localized sediment instability and forming discrete pockmarks; (2) the initial channel development stage, during which gravity flows exploit the pockmark chains as preferential erosional pathways, establishing nascent incised channels; (3) the channel expansion and maturation stage, marked by intensified erosion from high-density debris flows, resulting in a stepped longitudinal profile, while bottom-current reworking enhances lateral sediment differentiation; (4) the stable transport stage, wherein the channels fully integrate with the Sansha Canyon, forming a well-connected “platform-to-canyon” sediment transport system.