Ground penetrating radar and single-aliquot regenerative-dose optically stimulated luminescence were used to determine the depositional environments and age of unconsolidated siliciclastic sediments near Apalachicola, Florida. Five direct-push cores, five vibracores and 28 optically stimulated luminescence samples were collected, as well as 7 km of ground penetrating radar data. A new model of cosmic dose rate calculation, which removes the effect of a much younger aeolian cap, was utilized to calculate more representative optically stimulated luminescence ages. Five radar facies were identified based on reflector amplitude and orientation. The resulting data indicate that the Tertiary/Quaternary Shelly Sediments were deposited before marine isotope stage 6, the Quaternary Alluvium was deposited during marine isotope stage 6 and the Quaternary Beach Ridge and Dune was deposited during the marine isotope stage 5e sea-level highstand, which peaked at approximately 2·5 m above present sea-level in this area.