Freshwater Reservoir Effect in 14C Dates of Food Residue on Pottery

Abstract

Radiocarbon dates of food residue on pottery from northern European inland areas seem to be influenced significantly by the freshwater reservoir effect (“hardwater” effect) stemming from fish and mollusks cooked in the pots. Bones of freshwater fish from Stone Age åmose, Denmark, are demonstrated to be 100 to 500 14C yr older than their archaeological context. Likewise, food residues on cooking pots, seemingly used for the preparation of freshwater fish, are shown to have 14C age excesses of up to 300 yr. It is probable that age excesses of similar or even larger magnitude are involved in food residue dates from other periods and regions. Since this effect cannot, so far, be quantified and corrected for, 14C dating of food residue, which may potentially include material from freshwater ecosystems, should be treated with reserve.