Juxtaposed beach ridges and foredunes within a ridge plain — Wonga Beach, northeast Australia

Reports describing aeolian foredunes and wave-derived beach ridges juxtaposed within a single coastal barrier complex are rare, perhaps because morphological similarities make the two ridge types difficult to differentiate. This study of an approximately 4500year-old sand ridge plain in northeast Queensland, Australia using landform morphology, sedimentology and luminescence chronology suggests that ridge plain development here has been interrupted along part of the sequence by localised alterations in coastal sedimentation. A switch from coarse to fine-grained sand supply along one part of the beach has caused the development of prograding foredunes in the northeastern sector of the sequence over the past 700years. Contemporaneously, coarser textured beach ridges have continued to form behind the remainder of the beach. The result is a ‘complex barrier’ where a single ridge plain contains both foredunes developed through high frequency, low intensity events and beach ridges developed through high intensity, low frequency events associated with intense tropical cyclones.