The Trans-Atlantic Geotraverse (TAG) hydrothermal field on the Mid-Atlantic Ridge is characterized by a pronounced magnetic low and hosts both active and inactive hydrothermal mounds. Hydrothermal alteration is commonly inferred to cause demagnetization, yet the three-dimensional geometry and the driving mechanisms of its circulation remain poorly constrained. Here, we apply three-dimensional focusing inversion to near-seafloor magnetic data, enabling improved imaging of subsurface susceptibility structures. The resulting model reveals two major low-magnetization alteration columns rooted in a deep, interconnected demagnetized zone ( 4,100 m below sea level), separated at shallow levels by discontinuous high-magnetization blocks. We interpret this architecture as evidence for a coherent hydrothermal circulation system associated with a broadly connected deep thermal regime and modulated by fault-controlled flow. Furthermore, the shallow magnetization patterns provide geophysical constraints on the shallow circulation component involving focused upflow, lateral diffusion, and seawater recharge.
Marine sediment magnetic susceptibility (MS) is widely used to correlate sedimentary sequences, reconstruct paleoceanographic and paleoclimatic conditions, constrain sediment provenance, and identify disturbed or missing sections. Despite its importance, global prediction of near-seafloor MS remains difficult because observations are sparse and unevenly distributed. To address this, we predict grid-cell-average near-seafloor MS and its associated uncertainty on a global 5 × 5 arc-minute grid. We propose a Spatial Neural–Tree Ensemble (SNTE) model that integrates sparse MS observations with gridded environmental, geological, and oceanographic predictors. The model is benchmarked against tree-based, boosting, and hybrid baselines using Random, Buffered 200 km, Spatial Block 200 km, and Spatial Block 422 km cross-validation schemes. Because near-seafloor MS is spatially autocorrelated, spatially explicit validation schemes provide a more realistic estimate of generalization performance: under the most stringent Spatial Block (422 km) validation, SNTE achieves R² = 0.425 (RMSE = 237.87 × 10⁻⁶ SI), which we report as the primary performance metric. Random cross-validation yields a higher R² = 0.580 but is inflated by spatial leakage. The 15.5
Seabed geoacoustic parameters are crucial for coupled geoacoustic and underwater acoustic. Although sediment grain-size and compositional data in the Qiongdongnan region are abundant, measurements of seabed geoacoustic parameters remain limited. Based on measured grain-size and compositional data from 221 sediment stations in the Qiongdongnan region, this study uses forward modelling with the Helgerud effective medium theory and fluid–solid Zoeppritz equations to estimate sediment density, wave velocities, attenuation, and reflection coefficients. The results show that sediment density ranges from 1.42 to 1.92 g/cm3, with higher values in reef-island domain and lower values in deep-water domain. P- and S-wave velocities range from 1520 to 1670 m/s and 90 to 180 m/s, respectively, and show spatial patterns consistent with sediment density. Attenuation ranges from 0.63 to 0.78 dB/λ, with higher values in deep-water domain and lower values in reef-island domain, while the normal-incidence reflection coefficients range from 0.17 to 0.37 and show opposite trend. As the incidence angle increases from 0° to 90°, the reflection coefficient shows three regimes: creeping at 0–40°, accelerated at 40–70°, and gradual increase at 70–85°. The analysis suggests that seafloor geoacoustic parameters are mainly controlled by hydrodynamics, geomorphology, and sediment supply. High-energy shelf environments promote sediment coarsening and compaction, leading to higher density and wave velocities but lower attenuation, whereas fine-grained deposition in weakly dynamic deep-sea domain results in the opposite trend. Seafloor reflection behaviour is controlled by sediment properties, with P-wave reflection coefficient showing segmented angle dependence, rapid change near the critical angle, and varying characteristics across domains.
The Brazilian Equatorial Margin (BEM) is an oblique-transform continental margin inherited from the Pangea breakup and the opening of the Equatorial Atlantic Ocean. Located in the central portion of the BEM, the Barreirinhas Basin is a frontier region with only three deep-water wells. Efforts have been made to understand its tectono-depositional evolution and potential for petroleum exploration. This study provides the first integrated characterization of fluid migration systems in the offshore Barreirinhas Basin, identifying and mapping seismic indicators, as well as connecting them with regional settings. We analyzed conventional 2D and 3D seismic reflection data, integrated with available well data. Additionally, seismic attributes (instantaneous amplitude, pseudo-relief, similarity, and chaos) were applied to enhance the interpretation of conventional seismic profiles. Our results show diverse fluid migration features, from deep strata to the seafloor, constrained in four main migration systems. Two systems are correlated to regional gravitational collapse. Fluid conduits, pockmarks, mounds, and faulted zones indicate focused fluid flow. A third system is developed in a region dominated by transform tectonics related to the Romanche Fracture Zone, in which dense fault networks are observed within a laterally extensive interval from the slope to the basin plain. The fourth system is located in a broad region of the basin plain, characterized by numerous seafloor mounds associated with fluid conduits and seismic indicators of hydrocarbon accumulation. These findings improve the knowledge about an underexplored basin and provide a foundation for the understanding of fluid migration systems and their implications, including marine processes and products, emplacement of igneous bodies, and hydrocarbon prospectivity.
Submarine pockmarks are among the most ubiquitous geomorphological expressions of seafloor fluid escape, commonly occurring in high-density fields that may include hundreds to tens of thousands of individual features. Under these conditions, traditional manual morphometric analyses become time-consuming and impractical, limiting the robustness and reproducibility of pockmark-based studies. In this work, we present an open-source Python-based semi-automated workflow designed to systematically analyse the morphometry of pockmark populations using Digital Elevation Models (DEMs) and polygonal vectors as primary inputs. The workflow enables extraction of a comprehensive set of planimetric, elevation-based, geometric, and volumetric measurements, thereby minimizing operator-dependent biases. The approach has been tested on two contrasting geological case studies: the tectonically and volcanically active Graham Bank region in the Sicily Channel, mapped using high-resolution multibeam bathymetry, and the passive north-western Sardinian continental margin, investigated using regional-scale bathymetric grids from EMODnet Bathymetry. These datasets allow evaluation of the workflow performance across different geological settings, spatial resolutions, and pockmark size classes. Results demonstrate that the workflow provides robust and internally consistent morphometric outputs, suitable for large-scale statistical analyses and comparative studies. Although developed and validated on submarine pockmarks, the method is inherently general and can be applied to any negative landform that can be represented as a closed polygon and for which a DEM is available, such as karstic sinkholes or other collapse-related depressions. The proposed workflow therefore represents a flexible and reproducible methodological framework with broad applicability across geomorphology, environmental sciences, and hazard-related studies.
