Discerning the major environmental processes that influence the magnetic properties in three northern Iberia mountain lakes

This work presents the paleoenvironmental reconstructions from three mountaineous lakes located in northern Iberia. The results from the three lakes are compared and completed with classical magnetic analyses in order to detect the influence of different processes on the record and preservation of magnetic properties. The lakes are located in the Cantabrian Mountains, Enol Lake, and in the Pyrenees, the Marboré Lake and Basa de la Mora Lake and share a similar composition of their catchment areas, dominated by limestones, although in Basa de la Mora ophites are also present. The organic matter content differs, being Enol the one with the highest organic carbon values. Redox indicator (Mn/Fe) is higher and more variable in Basa de la Mora Lake, whereas in Enol and Marboré Lakes steadily increases towards the top of the sequences. New and revisited results unravel the significance of the magnetic changes respect to the geochemical and sedimentological variations found in the geological record. Strong magnetic magnetite dominates the magnetic properties variations, with detrital and new grains formed due to diagenesis and changes in the redox conditions -more aerobic-, which alter the concentration of magnetic minerals during the Late Pleistocene and Holocene. The new and revisited data underlines their value as environmental and paleoclimate archives.