Sticky dunes in a wet desert : formation, stabilisation and modification of the Australian desert dunefields

Independent dating evidence and dune morphology indicate great stability of the Australian dunefields. Most dunefields have seen only minor superficial modification since they were formed, up to 1 million years ago, despite quite large changes in climate conditions. This stability may be partly due to the relatively dense vegetation cover on Australian dunes under the marginally arid climate. But new studies, supported by many older observations, suggest that 'sticky' dunes (where sand grains are bonded or cemented) may form under a broader range of wind climates than widely thought and have greater resistance to reworking. New mapping of the Australian continental dunefields from satellite imagery shows a previously unrecognised diversity of dune morphologies. Dune orientation, continuity, connectedness, crest planform, crest sharpness, spacing and setting all show patterns of variation over the continent. These are consistent with the overall low sand supply and variable wind climate that contribute to the dominance of longitudinal dunes but also with only superficial modification of the dunes after their initial formation. The longevity of the dunes is likely also partly due to the stabilisation of dune sand by pedogenesis: the bonding of sand by pedogenic calcium carbonate, gypsum, silica and translocated clays. The extremely low mobility of the sand dunes has led to preservation of dunes of great age, with stacked accretionary units and multiple palaeosols.17 page(s