The dataset derives from marine sediment core KC-13, recovered from the central Aegean Sea, Greece (38°14.6012′ N, 25°06.2470′ E; 652 m water depth), during the OTE-2019 expedition (HCMR, R/V Aegaeo). It comprises grain-size data including clay/silt ratios, silt% and mean sortable silt. Samples were treated with a 1 M hydrochloric acid solution to remove carbonates, followed by 10% hydrogen peroxide to oxidize organic matter, thereby isolating the siliciclastic fraction of the sediments. To disperse aggregates and prevent re-agglomeration, the samples were briefly boiled in a sodium pyrophosphate solution prior to grain-size analysis.