Two-dimensional chronostratigraphic modelling of OSL ages from recent beach-ridge deposits, SE Australia

Optically-stimulated luminesecne (OSL) dating, in concert with two-dimensional ground-penetrating radar (GPR) profiling, has contributed to significant advances in our understanding of beach-ridge systems and other sedimentary landforms in various settings. For recent beach-ridges, the good OSL properties of coastal quartz permit a high sample throughput thanks to shorter measurement times and simpler sample preparation prompting the collection of more samples at higher sampling resolution. However, sampling at high resolution increases the chance of age inversions because random errors between samples may be larger than the difference in sample ages. Age inversions can be avoided, however, if the stratigraphic constraints are included in the age estimation process. Here, we create a custom Bayesian chronological model for a recent (< 500 yr) beach-ridge sequence in Moruya, southeast Australia, for direct comparison with a GPR profile. The model includes a full ‘burial-dose model’ for each sample and a dose rate term with the modelled ages constrained by the vertical and shore-normal sample order. The modelled ages are visualized by plotting isochrones on the beach-ridge cross section, and validated against a beach monitoring dataset. The modelling approach allows a more detailed interpretation of the Moruya beach-ridge system; when combined with higher-resolution sampling, the approach will increase the precision of beach-ridge chronologies and provide further insights into their formative processes.