A set of 13 new unspiked K-Ar dates has been obtained for the Quaternary basaltic volcanism in the Kula area of western Turkey, providing improved age control for the fluvial deposits of the Gediz River that underlie these basalt flows. This dating is able, for the first time, to resolve different ages for the oldest basalts, assigned to category beta 2, that cap the earliest Gediz deposits recognised in this area, at altitudes of similar to 140 to similar to 210 m above present river level. In particular, the beta 2 basalt capping the Samig Plateau is dated to 1215 +/- 16 ka (+/- 2 sigma), suggesting that the youngest underlying fluvial deposits, similar to 185 m above present river level, are no younger than marine oxygen isotope stage (MIS) 38. In contrast, the beta 2 basalt capping the adjacent Burgaz Plateau is dated to 1014 +/- 23 ka, suggesting that the youngest underlying fluvial deposits, similar to 140 m above present river level, date from MIS 28. The staircase of 11 high Gediz terraces capping the latter plateau is thus dated to MIS 48-28, assuming they represent consecutive similar to 40 ka Milankovitch cycles, although it is possible that as many as two cycles are missing from this sequence such that the highest terrace is correspondingly older. Basalt flows assigned to the beta 3 category, capping Gediz terraces similar to 35 and similar to 25 m above the present river level, have been dated to 236 +/- 6 ka and 180 +/- 5 ka, indicating incision rates of similar to 0.15 mm a(-1), similar to the time-averaged rates since the eruptions of the beta 2 basalts. The youngest basalts, assigned to category beta 4, are Late Holocene; our K-Ar results for them range from zero age to a maximum of 7 2 ka.