The Alkimos area, like much of the coastal plain near Perth, contains two main soil types. The
majority of the land consists of the yellow sands and limestone protrusions of the Spearwood Dune
System. An iron oxide coating is responsible for the dark yellow colouration of these sands. This
dune system is thought to be around 40 000 years old. Sand dunes are always shifting, which has
resulted in some of the limestone rocks beneath the Spearwood Dune System becoming exposed, as
the sands above them are eroded.
If you venture to the west of Kells Road Reserve, towards the coast, you will notice that the sand is
mostly light grey or white, as this region is part of the Quindalup Dune system. The Quindalup dunes
are much younger, and are largely formed from grains of quartz and shell fragments. Over time, the
calcium carbonate contained in shell fragments is dissolved and deposited at the base of the dune,
eventually forming caves.
Beach to Bush Profile