Thermoluminescence properties of quartz grains, particularly in relation to growth of the TL peak at 325°C as function of radiation dose, have been investigated for samples extracted from sediments collected at Cananéia Island, State of São Paulo, Brazil. The behavior of TL vs dose in quartz comprises three regions: up to about 100 Gy, the TL increases rapidly; between 100 and 400 Gy it grows very slowly; and beyond 400 Gy, the growth rate becomes rapid. Data above 800 Gy are not included. A model similar to that for the F centers in alkali halides is proposed for the growth of this TL peak as function of dose. Based on this model, the equivalent dose values for dating are obtained. © 1997 Elsevier Science Ltd.