The lake sediments represent a real archive of what happens in the lake and its catchment area. External contributions made up of fluvial, atmospheric and polluting origin materials contribute to their formation. The sediment often has a laminar structure, with laminae made of allochthonous mineral material (clastic laminae, formed from detrital ore, or from volcanic ash and pyroclastic material) and organic material (biochemical laminae), both allochthonous and autochthonous. The original deposition of the sediment can be modified due to phenomena such as underwater landslides, resuspension of materials by currents, and bioturbation by benthic animals. Furthermore, chemical phenomena such as redissolution can modify the original composition of the sediment.