Spatial patterning, sedimentology and chronological evolution of linear dunes, Strzelecki Desert
1, Paul Hesse2, Nick Lancaster3
1Plymouth University, Plymouth, UK, 2Macquarie University, Sydney, Australia, 3Desert Research Institute, Reno, USA
Linear dunes, when viewed from above, are one of the world’s most strikingly organised landscapes, yet the controls on patterning within linear dunefields remain poorly understood. The concept that linear dunes are self-organising phenomena, operating within the complex system formed by interactions within and between the turbulent atmospheric boundary layer and an erodible loose-sand substrate, suggests that different dunefield patterns may represent the outcomes (i.e. attractors) of different evolutionary trajectories, or different stages along a trajectory, through the phase-space of the complex aeolian system. Modelling suggests that pattern coarsening, whereby highly disorganised patterns become simpler over time, is likely to be a dominant control. However, there are no studies which have combined new dune pattern morphometric analysis with geochronological data, and where this has been attempted from published literature, there is evidence that pattern coarsening alone does not appear to explain the diversity of morphologies observed (Telfer and Hesse, 2013).
This study therefore aims to test the hypothesis that pattern development, as a function of time, exerts a first-order control on the age and nature of linear dune accumulation. Two nearby (~15 km) pairs of linear dunes from the Strzelecki desert, central Australia, each pair from an area with markedly different planform patterning, were therefore sampled for geochronological (using Optically Stimulated Luminescence, OSL) and sedimentological analysis. Sites were selected in close proximity to each other in order to minimize the possible effects of other controlling variables, such as past variations in climate; it can be assumed here that such changes are synchronous between the pairs of sites.
The results reveal a complex accumulation record dating back to 145 ± 20 ka, and some sites reveal periods of very rapid accumulation compared to existing Australian data. Despite their proximity, there exists considerable variability between profiles. However, this variability is neither accounted for, nor limited to, differences between the degree of pattern complexity of the less organized and more organized dunes. There is also considerable sedimentological variation between the cores, but again this is not apparently a function of the spatial complexity of the dune planform patterning.
We discuss the relative role of local vs large-scale controls on dune patterning, and the role of stochastic preservational effects on chronometric records of dunefield accumulation. The results suggest that pattern coarsening within linear dunefields is not straightforward, and requires further investigation.