14 of the 50 samples used in silica quantification were used for size analysis, wherein 12-13 Coscinodiscus spp. frustules per sample were observed under a scanning electron microscope and their valve areas, valve diameters, valve face porosities, and mantle thicknesses were measured. In this dataset, 'depth' is the midpoint distance each sediment sample was taken from the top of the core in m, 'age' is the calibrated age in both years before present and in common era calendar years, 'specimen' is the arbitrary number of frustule within each sample, 'valve area' is the total area of the valve face and mantle per specimen in µg², 'mantle thickness' is the average thickness of the mantle across four points per specimen in µm, 'max/min feret's diameter' is the maximum or minimum diameter across the valve per specimen in µm.