The Tanami region is of mainly red Quaternary sandplains overlying Permian and Proterozoic strata which are exposed locally as hills and ranges. The sandplains support mixed shrub steppes of "Hakea suberea", desert bloodwoods, acacias and grevilleas over "Triodia pungens" hummock grasslands. Wattle scrub over "Triodia pungens" hummock grass communities occur on the ranges. Alluvial and lacustrine calcareous deposits occur throughout. In the north they are associated with Sturt Creek drainage, and support "Chrysopogon" and "Iseilema" short-grasslands often as savannas with River Gum.