The CHIMERA project, contracted by the Portuguese Environment Agency (APA) and co-funded by the EuropeanUnion Cohesion Fund (Portugal 2020 | POSEUR) intended to characterize the sedimentary record of three 10km2 areas and one 5 km2 area in the Portuguese inner shelf. Multibeam bathymetry and backscatter, parametricecho-sounder, ultra-high resolution multichannel seismics and magnetic data were acquired along high resolutionorthogonal grids. The main aim of the project was to evaluate potential borrow areas for high-magnitude beachnourishments in long term eroding stretches of the Portuguese western coast. The diversity, the large density andthe high quality of geophysical data allow for a multidisciplinary geological interpretation of the datasets.In this presentation we focus on magnetic data and its interpretation combined with acoustic data. We applieda detailed processing scheme to acquired magnetic data, which allowed retrieving several components of themagnetic spectrum and estimating some source depths. We then analyzed the geological significance of theanomalies by studying their correspondence to seismostratigraphic units mapped from seismic data. Fit betweenmagnetic signature and geologic structure was found for most of the cases, although magnetic anomalies withinthe same wavenumber spectrum may express different geological units for each study area. A correspondence wastypically found for the basement, and for recent sedimentary structures such as paleo-channels and paleo-coastalbarriers. In other cases, low wavenumber anomalies may express intra-basement geology, too deep to be observedby our high-resolution seismics. For individual anomalies we check for a relation with shallow features, eventuallyarcheological artifacts.Publication supported by FCT- project UID/GEO/50019/2019 - Instituto Dom Luiz.

The SW Portuguese margin has been intensively studied, particularly for rifting, tectonic inversion and tectonic reactivation of the Atlantic passive margin. In this work we bring new data on the continental shelf, usually not acquired by the heavier geophysical methods (e.g. airborne or low resolution deep seismic-magnetic surveys). These new data allow casting a clear light bridging between the geological structures onshore and offshore. The geology of this margin went through the Variscan orogeny of Paleozoic age, the North Atlantic rifting, the Late Cretaceous alkaline magmatism (intrusive and extrusive), the Alpine tectonic inversion and the Quaternary reactivation of the passive margin. We present results from the compilation of a series of marine magnetic surveys conducted along the Portuguese nearshore from 2014 to 2019. Magnetic data were acquired with 1 nautic mile line separation, resulting in near full coverage of the nearshore along a 120 km long margin segment, from Sintra to Odeceixe. For a large part of the surveyed area, ultra-high resolution seismics and multibeam bathymetry were simultaneously acquired. Magnetic data were processed to produce high resolution mapping of magnetic anomalies, and also to enhance both shallow and deep structures, using several derivative and filtering techniques. We combine the interpretation of high-resolution magnetic mapping with the interpretation of ultra-high resolution and vintage deep penetration seismic data to infer the local and regional expression of tectonic structures and magmatic bodies. Our results allow: identifying the offshore extension of important faults, e.g. the Grândola, Pinhal Novo and Messejana faults; resolving previously blurry-imaged magmatic structures, e.g. Sines and Cabo Raso anomalies; identifying faults recycled from the Paleozoic through Present; constraining the relation between magmatic intrusions and faults; and bringing constraints to the discussion of magmatic emplacement.