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Combining magnetic and seismic reflection data for characterization of inner shelf sand nourishment areas
  • +8
  • Marta Neres,
  • Pedro Brito,
  • Marcos Rosa,
  • Pedro Terrinha,
  • João Noiva,
  • Mariana Antunes Silva,
  • Eveline Almeida,
  • Celso Pinto,
  • Bruno Pires,
  • Nuno Penacho,
  • Tanya Mendes Silveira
Marta Neres
Portuguese Institute for the Sea and Atmosphere (IPMA)

Corresponding Author:[email protected]

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Pedro Brito
Portuguese Institute for the Sea and Atmosphere (IPMA)
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Marcos Rosa
Portuguese Institute for the Sea and Atmosphere (IPMA)
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Pedro Terrinha
Portuguese Institute for the Sea and Atmosphere (IPMA)
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João Noiva
Portuguese Institute for the Sea and Atmosphere (IPMA)
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Mariana Antunes Silva
Portuguese Institute for the Sea and Atmosphere (IPMA)
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Eveline Almeida
Faculdade de Ciências de Universidade de Lisboa
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Celso Pinto
Portuguese Environment Agency (APA)
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Bruno Pires
Portuguese Environment Agency (APA)
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Nuno Penacho
Portuguese Environment Agency (APA)
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Tanya Mendes Silveira
Portuguese Environment Agency (APA)
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Abstract

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.