While working with the revision of the Swedish Time Scale, based on clay‐varve chronology, mollusc shells ofPortlandia (Yoldia) arcticawere found in the clay at Ekensberg, Stockholm, Sweden, deposited at the beginning of the Finiglacial epoch. The clay‐varves have been connected with the revised Swedish Time Scale and the time for deposition is 10,370 clay‐varve years cal BP. Shells of bivalves, shell fragments and periostracum have been AMS radiocarbon‐dated at the The Svedberg Laboratory in Uppsala. The 11 radiometric datings are grouped in two assemblages, one between 10,500 and 11,600 BP (shell carbonate) and one between 8200 and 9100 BP (periostracum). These results are compared with the radiocarbon age obtained for a fish skeleton (Salmo alpinus) found in varved clay close to Ekensberg during the geological mapping of the area. The age of the fish is 8600 BP, which is in agreement with the periostracum datings. Reservoir effects and calibration of the radiocarbon ages (BP) to sidereal years (cal BP) are di