Aplicación de técnicas magnéticas al estudio de alta resolución de sedimentos Cuaternarios de la plataforma continental adyacente a las Rías Baixas de Galicia

Resumo

The continental shelf off southern Galicia constitutes a complex sedimentary environment characterised by the seasonal influence of the coastal upwelling, the influence of the nearby, highly productive, Rías Baixas and the presence at the southernmost part of the Miño river. High-resolutionmagnetic characterisation has been carried out on vibrocore 7.V-27, recovered in the continentalshelf adjacent to the Ría de Vigo. Low-field magnetic susceptibility, IRM acquisition and ARM weremeasured on this core at 1 cm resolution. The results show higher values of all these parameters inthe upper 50 cm, below this interval, values decrease rapidly with depth. Coercitivity dependentparameters have proved useful in determining the origin of the measured signal. Large differencesin coercitivity spectra have been detected, suggesting a multimineralogical origin of the magneticbehaviour. Reductive dissolution of the magnetic minerals is considered as the driving engine ofthe processes leading to the change in the magnetic properties. This interpretation is supported bya relative coarsening of the soft magnetic minerals with depth, as a result of the faster dissolutionof the finer grain sizes during diagenesis.