Using calibrated surface roughness dating to estimate coastal dune ages at K'gari (Fraser Island) and the Cooloola Sand Mass, Australia

Abstract

Here we present a novel application of landscape smoothing with time to generate a detailed chronology of a large and complex dune field. K'gari (Fraser Island) and the Cooloola Sand Mass (CSM) dune fields host thousands of emplaced (relict) and active onlapping parabolic dunes that span 800 000 years in age. While the dune fields have a dating framework, their sheer size (~1930 km²) makes high-resolution dating of the entire system infeasible. Leveraging newly acquired (n = 8) and previously published (n = 20) optically stimulated luminescence (OSL) ages from K'gari and the CSM, we estimate the age of Holocene dunes by building a surface roughness (σC)–age relationship model. In this study, we define σC as the standard deviation of topographic curvature for a dune area and we demonstrate an exponential relationship (r² = 0.942, RMSE = 0.892 ka) between σC and timing of dune emplacement on the CSM. This relationship is validated using ages from K'gari. We calculate σC utilizing a 5 m digital elevation model and apply our model to predict the ages of 726 individually delineated Holocene dunes. The timing of dune emplacement events is assessed by plotting cumulative probability density functions derived from both measured and predicted dune ages. We demonstrate that both dune fields had four major phases of dune emplacement, peaking at <0.5, ~1.5, ~4, and ~8.5 ka. We observe that our predicted dune ages did not create or remove major events when compared to the OSL-dated sequence, but instead reinforced these patterns. Our study highlights that σC–age modelling can be an easily applied relative or absolute dating tool for dune fields globally. This systematic approach can fill in chronological gaps using only high-resolution elevation data (3–20 m resolution) and a limited set of dune ages.