Supplemental material Annex 1: Diatoms quantification For quantitative analysis, 2 cc. of fresh sediment were taken from each sample, weighed, dried, weighed again and cleaned according to the method of Fenner [1982]. Slides were prepared using the evaporation tray method of Battarbee [1973], and mounted with Permount medium. Diatom quantification was done under a Nikon Labophot 2A microscope equipped with Differential Interference Contrast, using 10 x eyepieces and 100 x oil objectives. Diatom quantification was conducted following the counting procedures of Schrader and Schuette [1968]. Diatom frustules were counted in 100 randomly selected fields of view for one slide prepared from each sample. Diatom counts were then converted to valves/g of sediment according to the following expression: Number of valves/g= [(Vn_ (At/As)) _ (V/v)] / W, where Vn is the number of valves counted, At is the area of the evaporation tray, As is the area of the slide counted, V is the volume of solution in the beaker, v is the volume of solution splitted into the evaporation tray, and W is the weight of raw sample. Diatom flux, expressed as valves/cm2/ka, was finally calculated by multiplying the sediment flux (230Th Ðnormalized flux) by the diatom content (valves/g) at each level, according to the following equation: Total Diatom Flux = Total Diatoms (valves/g) x 230Th normalized flux at the same level References Battarbee, R. W. (1973), A new method for the estimation of absolute microfossil numbers, with reference especially to diatoms, Limnology and Oceanography, 18, 647-653. Fenner, J. (1982), Diatoms in the Eocene and Oligocene sediments off NW Africa, their stratigraphic and paleogeographic occurrences, University of Kiel, Kiel. Schrader, H.-J. and G. Schuette (1968) Marine Diatoms. In The Sea, edited by Emiliani, C., pp. 1179-1231, John Wiley & Sons, New York.