AEOLIAN, FLUVIAL, AND LACUSTRINE INFLUENCES ON LINEAR DUNE SEDIMENT SUPPLY AT LAKE CAROLINE IN THE SIMPSON DESERT OF AUSTRALIA

Abstract

The mechanisms responsible for the formation, maintenance, and sediment supply of Australia's extensive linear dune system in the Simpson Desert are highly debated. This study examined the interaction between aeolian, fluvial, and lacustrine processes at Lake Caroline in the arid, southeastern corner of the Northern Territory of the Simpson Desert in Australia: a region encompassing a linear dune field, ephemeral river, and series of playa lakes. We integrated mineralogical and grain analyses, optically stimulated luminescence (OSL) dating, wind direction analysis, precipitation frequency analysis, and remotely-sensed historical flood observations to examine the modern relationship between fluvial and lacustrine processes on linear dune evolution. We find that (1) the local sediments are a combination of eroded dunes, local weathered basement rock, clay, and evaporite minerals, (2) the playa flooded at least 58 times over 19 years, and (3) based on available weather data over six years, wind speeds at Lake Caroline surpassed the threshold for transporting fine sand more than 20% of the time. Our observation that linear dunes surrounded by Lake Caroline erode into the playa lake argues that present-day linear dune maintenance and stability depend on a local sediment supply. Results provide a sedimentological fingerprint along with the verification of specific climatic conditions that reveal the relatively recent (< 60 ka) erosion of local sediment not only degrades and starves the linear dunes from sediment supply in close proximity to fluvial landforms, but may also supply sediment for present-day, downwind linear dune formation. The dynamic role of fluvial and lacustrine processes on linear dune activity, including dune formation, maintenance, and degradation is important for understanding ancient and modern dune systems in semi-arid and arid environments.