Abstract
Linear dunes constitute more than 40% of dunes on Earth and occur on all planets with an atmosphere in our solar system. However, the processes controlling their formation and evolution remain debated. Recent observations of a playa lake surrounded by a linear dune field show the erosion or "cannibalization" of the dunes into the dry lake bed. These observations complicate the basic paradigm that linear dunes are stable during wetter climatic cycles, but may be subjected to erosion during more frequent and intense rain events. We investigated the sediment characteristics of the playa Lake Caroline and the adjacent linear dunes located in the northern Simpson Desert of Australia to (1) identify periods of lacustral flooding in Lake Caroline, and (2) estimate the contribution of linear dune sand within the Lake Caroline sediments. We collected three cores using a hand auger to a depth of 2.25 m along a 1.7 km transect, and grab samples from a linear dune adjacent to the playa. Grain characteristics, soil textures, and X-ray diffraction analyses were performed at selected depths from each core and from the dune sediments. Results suggest that intermittent floods were responsible for the deposition of poorly sorted, pebble sized, terrigenous sediments at depths >1.20 m. Evaporation in the playa resulted in the precipitation of gypsum and halite. Sediments with grain characteristics, soil texture, and mineralogy consistent with the sediment profile of the dune were identified up to a depth of 2 m on the north side of the transect suggesting a remnant dune beneath the playa surface. Vertical progressions in the sediment profile of the other two cores reflect an upward trend of fluvial to aeolian deposition indicating increasing aridity. Investigations into aeolian and fluvial landform interaction in the later Quaternary will help to understand the evolution of desert landforms, and serve as morphologic analogue sites for the planetary science field.