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Fluvial-Aeolian-Lacustrine Controls on Large Scale Facies Distributions in the Dryland Continental Lake Eyre Basin, Australia

Carmen Krapf1, Simon Lang1, and Tobias Payenberg2
1 University of Adelaide, Adelaide, Australia
2 Australian School of Petroleum, University of Adelaide, Adelaide, Australia

Dryland fluvial-aeolian-lacustrine, and terminal splay successions are important reservoir elements in many non-marine basins (eg. North Sea and North African Triassic, South Caspian Pliocene).

The Lake Eyre Basin, central Australia, has been used as an analogue for these basins, but a basin-scale facies model is yet to be established. The Lake Eyre Basin (>1 Million km2) is a vast, internally-draining, low accommodation dryland fluvial-lacustrine basin, containing the World's fifth largest playa lake system (Lake Eyre). The northeastern rivers are characterised by extensive catchments and receive the highest precipitation from tropical cyclones in far-northern Australia, whereas rivers in the western part have smaller catchments and comparatively little precipitation. These shorter western rivers terminate within Lake Eyre forming sandy terminal splay complexes. The larger northeastern rivers however dump most of the their coarse-grained sediment load in large floodouts 400 km inland from the playa margin, so mainly fine-grained sediment is transported to Lake Eyre. The floodouts are up to 300 km long and 100 km wide and comprise anabranching rivers separated by extensive floodplains. The floodplain and the lake plain is dominated by a broad Quaternary longitudinal and transverse, aeolian dune complex (Simpson, Strzelecki, Tirari deserts) that represents a significant sand storage area, ready to be reworked into fluvial systems in a future wet phase.

The high variability of depositional elements at various scales within the basin emphasizes the care that needs to be taken when using the Lake Eyre Basin as an analogue for both regional and field scale palaeogeographic reconstructions.