Combining magnetic and seismic reflection data for characterization of
inner shelf sand nourishment areas
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.