Amino acid ratios of gastropods provide a useful basis for correlation and approximate dating of middle to late Quaternary fluvial deposits from the northern Española basin, New Mexico. Sparsely fossiliferous slackwater deposits in the Rio Chama-Rio Grande floodplain were buried episodically by piedmont alluvium during periods of climatic change as the axial river system cut down 120 m during the past 620,000 yr. Alloisoleucine/isoleucine (alle/Ile) ratios in the total hydrolysate and free fraction of amino acids in Succinea and Vallonia are strongly correlated with elevation. Ratios in Succinea range from 0.01 to 0.79 in the total hydrolysate and from 0.00 to 1.15 in the free fraction for deposits that range in age from modern to ⩾620,000 yr old. Amino acid ratios are tightly clustered for deposits that contain the 620,000-yr-old Lava Creek B tephra layer, demonstrating their utility for correlation and providing a calibration point for a local dating curve. Two 14C ages from younger deposits and limiting ages for erosion surfaces that lie above gastropod-bearing units tend to support the validity of much of the curve. Combining the dating curve with the geologic constraints suggests that aggradation events, separated by episodes of net incision, occurred at about 620,000, 310,000 ± 70,000, 170,000 ± 40,000, 95,000 ± 15,000 yr ago, after 19,000 yr ago, and during two minor periods between 80,000 and 25,000 yr ago.