The extent of racemization of glutamic acid in shells of the mollusk S. giganteus (Deshayes) was used to estimate the ages of estuarine shell deposits at Willapa Bay, Washington. By ap-plying first-order kinetics and making assumptions about diagenetic temperatures, two distinct ages of shell deposits, 110,000 and 190, 000 years old, can be identified. These ages correspond to interglacial periods having high stands of sea level. -- AATA