For my Ph.D. I studied the evolution of the sediments in the Spanish rķas of Vigo, Pontevedra and their adjoining continental shelf since the Last Glacial Maximum. The central enviromagnetic perspective also integrated sedimentological, geochemical and hydrodynamic data. This multidisciplinary approach resulted in a better understanding of the interplay between the detrital, diagenetic and anthropogenic processes occurring in the area, and allowed for a more accurate interpretation of their palaeoclimatic and environmental significance.
The sediments in the rķas were greatly affected by redoxomorphic processes driven by the remineralization of organic matter. This led to a significant alteration of their magnetomineralogical assemblages, and based on their distinct magnetic properties resulted in a marked three-layer diagenetic zonation of the sedimentary column. This was a characteristic feature of these rķa environments. Magnetite controlled its characteristics in the uppermost and more magnetic oxic zone, where live magnetotactic bacteria were detected and framboidal Fe sulphides occurred within organic-rich microenvironments. In the intermediate zone, the progressive dissolution with depth of Fe oxides caused a sharp decrease in magnetic concentration and coercivity of its constituents. Framboidal pyrites were ubiquitous, usually associated to ferrimagnetic greigite framboids. The lowermost zone was magnetically homogeneous, due to the almost complete dissolution of its magnetic minerals.
Water depth and wave-energy distributions were the main factors that controlled this zonation. Greater depths and wave-induced water agitation in the external zones resulted in a more effective oxidation of the organic matter within the water column and the seabed, which delayed the onset of reducing conditions in the sediments of these areas. This general diagenetic pattern was broken in areas of high anthropogenic impact due to re-oxygenation driven by enhanced turbulence and sediment remobilisation.
The sediments from the continental shelf showed a significant detrital control which was modulated by the evolution of the reducing conditions with depth during early diagenesis. The magnitude of these processes was estimated by fitting the concentration-dependent parameters to a steady-state diagenetic model. In this way, the palaeoclimatic significance of the data could be subsequently assessed with acceptable reliability, improved by a refined age model based on the inter-core correlation of magnetic concentration maxima. The results indicated that magnetic concentration maxima were related to warm events recorded during recent Holocene times. This was caused by enhanced continental detrital inputs to the continental shelf during these periods, probably resulting from increased humidity. Magnetic mineral depletion during cold periods was linked to reduced detrital input and enhanced diagenetic dissolution, suggesting increased productivity and organic matter export to the sediments.

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