Holocene coastal dune formation in southern Australia: A case study

Abstract

The 14,500 km long southern Australian coast is exposed to high-energy wave and wind regimes which have mobilized shelf-derived sediments to produce extensive Holocene shoreface deposits. The 8000 km of sandy coast are backed by over 2000 km 2 of Holocene dunes of varying degrees of stability. In places dune deposition above present sea level accompanied the post-glacial marine transgression commencing as early as 10 ka B.P., and has continued episodically to the present day. The dunes are widespread in extent but vary in type, size and evolution. The oldest and often most extensive (primary) dune fields accompanied the post-glacial marine transgression. They occurred, and in some places continue to form, in areas of high wave and wind energy and abundant sand supply. Many of these systems exhausted their sediment supply by mid-Holocene and remain as stranded clifftop dunes where sand ramps were eroded, or as eroding barriers. Secondary phases of dune activity occurred on moderate-to high-energy coasts following an initial period of post-stillstand barrier progradation. Diminished sediment supply resulted in shoreline erosion and (secondary) dune formation. The location, size and evolution both of dunes types is largely controlled by the breaker wave regime which in turn influences the rate and volume of sediment supply, beach morphodynamics and resulting aerodynamic boundary conditions, and foredune erosion. A study of dune formation along the 3700 km long South Australian coast provides a basis for an overview of dune formation throughout southern Australia.