Engineers Australia

Outline of the geology of the Perth region

Philip Commander

Abstract

Perth is located on a coastal plain consisting largely of unconsolidated sediments or dune limestone, with the eastern suburbs on weathered Precambrian crystalline rocks. The coastal plain is underlain by between 30 m and 70 m of Quaternary superficial sands, limestone and clay; and below this is some 10 km of sediments of the Perth Basin. Palaeocene sediments occupy a deep erosional channel below the city, cut into the Mesozoic sediments. The Darling Fault forms the eastern boundary of the basin with the Precambrian crystalline rocks of the Yilgarn Craton, which consist of granite, gneiss migmatite with minor schist, cut by dolerite dykes. The Precambrian rocks are deeply weathered with a lateritic profile. A variety of construction materials are readily available in the Perth Region and their sources are protected from sterilisation by planning controls.