Cristina Roque

Joint gravity–seismic inversion is a strong approach for imaging crustal and lithospheric structure, yet its success highly depends on the formulation of the gravimetric direct problem and the quality of input datasets. Here, we investigate how commonly used global and regional grids affect forward gravimetric modelling and the subsequent interpretation of crustal structure in complex tectonic environments.Following the methodology of Uieda et al. (2017), we construct forward gravimetric models for the Moho depth, based on multiple datasets: SGG-UGM2 gravity measurements, CRUST1.0 crustal thickness models, GlobSed sediment grids, and Gebco bathymetry. We explore the effects of grid resolution, interpolation strategies, and reference model choices on the gravity response, highlighting their influence on the information available to joint inversion schemes.Previous applications to passive margins provide an example for assessing robustness and sensitivity of the forward-modelling strategy. Extending the approach to a tectonically and magmatically complex region – Azores triple junction – demonstrates how variations in input datasets reveal lateral and vertical heterogeneities. Forward-model experiments indicate which features of the crust are robustly resolvable and how gravity inversion with a seismic constraint can illuminate the nature of the crust, including magmatic additions and crustal thickening.Our results emphasize that careful selection and treatment of gravity and auxiliary datasets is crucial to maximize geological information from inversions. Explicit consideration of forward-model assumptions, grid effects, and seismic constraints enhances confidence in inferred lithospheric structures, providing a practical framework for integrating multidisciplinary geophysical data in tectonically complex regions.In addition to regional-scale studies, this methodology can be applied in platform extension projects, providing a cost- and time-efficient preliminary assessment of extensive areas. By highlighting lateral and vertical heterogeneities and identifying zones where gravity responses are most sensitive to subsurface structure, forward-model experiments can guide the prioritization of future data acquisition. Such an approach allows for targeted deployment of more detailed seismic or geophysical surveys, reducing overall exploration effort while maximizing geological insight across large and complex tectonic domains.

The Azores-Gibraltar Plate Boundary (AGPB) materializes the present-day westernmost segment of the Africa (Nubia)-Eurasia plate boundary, and connects the Azores triple junction, at the west, to the Gibraltar orogenic arc, at the east. The Gloria Fault corresponds to its central and transform segment, trending E-W to WNW-ESE between 24° W and 14°30’W and showing dextral strike-slip motion. This feature corresponds to one of the rare examples of a ridge-transform fault-orogenic arc plate configuration worldwide. The Gloria Faults has also been the site of great-magnitude earthquakes, such as the 25 November 1941 (Mw8.4), the second-largest oceanic strike-slip event recorded worldwide. In spite of the studies carried out in this AGPB segment, the seismotectonics of the Gloria Fault is still poorly known. In this work we present a detailed morphostructural characterization of the Gloria Fault and discuss the relationship between the main morphostructures and seismicity, based on i) the geomorphological analysis of unpublished multibeam bathymetry collected in the scope of the Project of Extension of Continental Shelf; ii) correlation of the main morphostructures identified with instrumental seismicity and microseismicity records available from public catalogues (SHARE, USGS, IPMA) and published by several authors, and iii) profile gravity analysis based on SGG-UGM-2 satellite gravity data compilation.Based on the morphostructural, seismotectonic and gravimetric analysis we propose the existence of a Gloria Fault Transform System, which includes the several morphological features relate to its transcurrent motion (e.g., central valley, transverse ridges, restraining bend, Western Gap, Eastern Ridge), and the two main seismically active structures in the area, located at north and south of the Gloria Fault. This suggests that, at present, the stress due to the motion of the Africa-Eurasia plates is accommodated by seafloor deformation along a wide E-W stripe.This work is supported by FCT, I.P./MCTES through national funds (PIDDAC): LA/P/0068/2020 - https://doi.org/10.54499/LA/P/0068/2020 , UID/50019/2025, https://doi.org/10.54499/UID/PRR/50019/2025, UID/PRR2/50019/2025.

The Mediterranean-Atlantic water mass exchange provides the ideal setting for deciphering the role of gateway evolution in ocean circulation. However, the dynamics of Mediterranean Outflow Water (MOW) during the closure of the Late Miocene Mediterranean-Atlantic gateways are poorly understood. Here, we define the sedimentary evolution of Neogene basins from the Gulf of Cádiz to the West Iberian margin to investigate MOW circulation during the latest Miocene. Seismic interpretation highlights a middle to upper Messinian seismic unit of transparent facies, whose base predates the onset of the Messinian salinity crisis (MSC). Its facies and distribution imply a predominantly hemipelagic environment along the Atlantic margins, suggesting an absence or intermittence of MOW preceding evaporite precipitation in the Mediterranean, simultaneous to progressive gateway restriction. The removal of MOW from the Mediterranean-Atlantic water mass exchange reorganized the Atlantic water masses and is correlated to a severe weakening of the Atlantic Meridional Overturning Circulation (AMOC) and a period of further cooling in the North Atlantic during the latest Miocene.

This work uses seismic records to document and classify contourite features around the Iberian continental margin to determine their implications for depositional systems and petroleum exploration. Contourites include depositional features (separated, sheeted, plastered and confined drifts), erosional features (abraded surfaces, channels, furrows and moats) and mixed features (contourite terraces). Drifts generally show high- to moderate-amplitude reflectors, which are cyclically intercalated with transparent layers. Transparent layers may represent finer-grained deposits, which can serve as seal rocks. High-amplitude reflectors (HARs) are likely to represent sandier layers, which could form hydrocarbon reservoirs. HARs occur on erosive features (moats and channels), and are clearly developed on contourite terraces and overflow features. Most of the contourite features described here are influenced by Mediterranean water masses throughout their Pliocene and Quaternary history. They specifically record Mediterranean Outflow Water, following its exit through the Gibraltar Strait. This work gives a detailed report on the variation of modern contourite deposits, which can help inform ancient contourite reservoir interpretation. Further research correlating 2D and 3D seismic anomalies with core and well-logging data is needed to develop better diagnostic criteria for contourites. This can help to clarify the role of contourites in petroleum systems.

Seamounts are first-order morphological elements on continental margins and in oceanic domains, which have been extensively researched over recent decades in all branches of oceanography. These features favour the development of several geological processes, and their study gives us a better understanding of their geological and morphological domains. The seamounts around Iberia are numerous and provide excellent examples of the geodiversity of these morphological elements. Here we present a compilation of 15 seamounts around the Iberian Peninsula. These seamounts have different origins related to the geodynamic evolution (volcanism, extensional or compressive tectonics, and diapirism) of the domains where they are located. The current configuration of their relief has been influenced by Neogene-Quaternary tectonics. Their positioning controls the current morpho-sedimentary processes in the basins and on the margins, and highlights the fact that downslope processes on seamount flanks (mass flows, turbidite flows, and landslides) and processes parallel to seamounts (contouritic currents) correspond to the major geological features they are associated with them. Biogenic structures commonly develop on the tops of seamounts where occasionally isolated shelves form that have carbonate-dominated sedimentation.