A feature of Trigg Bushland is the parabolic dune, sand dune blow-outs that have been stabilised by a long process of revegetation. Few examples of this type of landform remain within the metropolitan area. The northern rim of the major Trigg parabolic dune borders Karrinyup Road and reaches its eastern extremity just short of the corner with Jeanes Road. The southern rim borders Jeanes Road.

The dunes are composed of white Quindalup sands formed within the last 6,000 years, during a period of rising and falling sea levels. A close examination will reveal shell fragments typical of beach sands.

As these dunes advanced they buried the limestone and yellow sands of the 100,000 years old Spearwood dune system. In some parts of the reserve, north of Karrinyup Road for example, Spearwood sands still occur at the surface.

For further information on Quindalup and Spearwood soils, refer to Soils of the Swan Coastal Plain (WA Dept of Agriculture & Food website).

 

Website development funded by a Department of Environment and Conservation Community Grant for Tuart Conservation and Management. Text and images copyright Friends of Trigg Bushland Inc except as otherwise noted. Website design by Nina McLaren and Peter Peacock 2008