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

Abstract

In central Australia, the most easterly extent of the MacDonnell Ranges border the Simpson Desert dunefield where widely spaced strike ridges intercept and isolate pockets of broad-crested linear dunes that reflect regional changes in Late Quaternary climate, flow regime and channel avulsion. An energetic Todd River reworked the eastern part of Camel Flat basin from 75-65 ka until the Last Glacial Maximum (LGM) when it shifted eastwards, but with some flows persisting through the basin until about 10 ka. Resulting desert surfaces of different age facilitate temporal comparisons of linear dune formation. Fine-grained red dunes, 75-65 ka in age occur on the western floor of the basin and are ramped against the foot-slopes of the range. After the LGM, and especially during the Holocene, the river's departure enabled small, pale-coloured, closely spaced, coarser-textured linear dunes to form on the abandoned floodplain in the eastern basin, their orientation 20ࠦarther west than the larger and older red dunes. This realignment indicates that the Australian wind-whorl shifted southwards some 160 km or 1.5ࠡfter the LGM. Linear dunes in the northwestern Simpson Desert were formed by wind rifting involving vertical accretion of sand from a proximal source, not by long-distance sand transport with linear extension. The blocking ranges have caused negligible downwind sediment accumulation over the past 75 ka.