Nature conservation

Biodiversity Reform

Simpson-Strzelecki Dunefields - landform

Topography

The Simpson-Strzelecki Dunefields are part of the Australian continental dunefields, which consist of a huge anti-clockwise whorl of linear dunes in central Australia. Most of the dunefield lies in the Lake Eyre Basin and the edge of the region extends into the NSW corner country. The region is dominated by high linear dunes of red sand.

Geology and geomorphology

The dunes and sandplains of this bioregion developed on Tertiary and Quaternary alluvial sediments. Thinner sheets of wind-blown sand that blanket the landscape as sandplains do not have a marked dune structure. In NSW, the dunes are formed by a westerly wind that moves sand from distant lake shores and reworks sand from the alluvial systems.

Most dunes are stable, but higher dunes, and those subject to land degradation by grazing, have active crests. Dune spacing varies from 50 to 500m and the intervening swales may expose underlying stony plain, deep alluvial sands and clays, or calcareous sandy soils.

The original source of the dune sands is generally considered to be the Great Dividing Range, with the sand being delivered by rivers through the Cooper Creek and Bulloo systems. There are few rock outcrops in the sand dune country other than small flat-topped hills of Cretaceous or Tertiary sediments.

Both the dunefields and the sandplains contain clay pans and ephemeral lake beds. Stream channels from the Tibooburra and Barrier Ranges flow toward Lake Callabonna and Lake Frome in northeastern SA and flood local claypans, but runoff is now insufficient to reach the distant lakes. Sands in the eastern part of the region are derived from the Bulloo overflow where they are associated with larger lake basins that contain well-developed beaches and lunettes.

Over the past 30,000 years variable climates have allowed greater dune mobility, more active streams and periods with full lakes. Details of this chronology are not well known for this area.

Geodiversity

Arguably, the Simpson-Strzelecki Dunefields Bioregion is the largest example of a linear sand dune environment in the world.

Important features of this bioregion include the following:

  • Tertiary vertebrate fossils in river and lake sediments such as the well-known Diprotodon sites at Lake Callabonna (SA), and well-preserved flora in silcretes such as the Miocene eucalypts from Sturt Creek, south of Lake Eyre; no comparable sites have been documented in NSW, although silcretes in the corner country are known to contain Tertiary plant fossils;
  • the dune country of Sturt National Park contains stone quarry sites on patches of gibber as well as numerous open campsites in the dunefields and on ephemeral lakes, swamps and streams; even the most extreme climatic zones have been occupied by Aboriginal people who used shallow seepage wells in inter-dune corridors; archaeological dates can place some constraints on ages of dune activity, but few have been obtained from this environment in NSW; and
  • the mound springs that occur on the margins of the dunefields in other states and many of the salt lake basins are groundwater windows; little is known of groundwater systems in this part of NSW.

Soils

The dunes have only minimal soil profile development as red siliceous sands, although the dune cores contain more clay and soil carbonate. Soils are better developed in the swales, along the creek lines and in the lake beds where fine alluvial sediments accumulate to form cracking brown or grey clays, harsh texture contrast profiles, and sandy red earths.

None of the soils contains high quantities of plant nutrient although the clays are better than the sands. Soil moisture retention is also better in the clays, but some clays contain high levels of soluble minerals such as gypsum and common salt that limit plant growth.

Documents to download


Next page: Simpson-Strzelecki Dunefields - biodiversity
Previous page: Simpson-Strzelecki Dunefields - climate
Up to contents page: Simpson-Strzelecki Dunefields Bioregion
Page last updated: 26 April 2016