Aeolian-fluvial interaction: evidence for Late Quaternary channel change and wind-rift linear dune formation in the northwestern Simpson Desert, Australia

In central Australia the most easterly extent of the MacDonnell Ranges borders the northwestern Simpson Desert where widely spaced strike ridges intercept the regional linear dunefield. Topographic basins have disrupted regional drainage lines and isolated dune sets from the main dunefield. In the western part of Camel Flat basin large, red coloured linear dunes of fine sand, ~ 74 ka and older, are oriented almost due north. Through gaps in the ranges the Todd River traversed the eastern part of the basin until ~25 ka when it apparently avulsed ~25 km eastwards to its present position. Subsequently, linear dunes, smaller, lighter in colour and coarser-textured, prograded onto the abandoned floodplain in the basin at rates of about 0.25-0.35 m a-1 and with orientations 20o further to the west than the older dunes. This new alignment suggests a latitudinal wind-whorl shift of some 160 km or 1.5o since the Last Glacial Maximum. Where dunes free of fluvial interference ramp onto the southern footslopes of the bedrock ridges they yield ages of at least ~65 ka, similar to the red dunes in the western part of the basin. These results highlight the difficulty of separating or interrelating the impacts of climate change, catastrophic flooding and aeolian damming as possible causes of Quaternary landscape change in the MacDonnell Ranges.