Fernbank (Fe)

Geology

Alluvial sediments deposited in the Pleistocene period. Following the notation of Vandenberg and O’Shea (1981), these sediments are referred to as Qp2 (see Geology and Geomorphology). They often contain quartz gravels up to 100 mm in diameter.

Landform

Undulating plain. It is regarded as a dissected Pleistocene alluvial terrace.

Soils

Most of the soils on this map unit are texture contrast soils, which means that they have light textured surface soils (gravelly loamy sands to sandy loams, commonly stony) abruptly overlying clay. Stones throughout the profile, up to 100 mm in diameter, are a common feature of many of the soils, particularly on hill slopes and the flanks of drainage lines. In exposures, the soils are mottled red and grey and in some localities gravelly ironstone crops out on the sides of valleys (Ward, 1977).

There may be the occasional sand dune on this map unit. These dunes become a feature of this landscape further east and are mapped as the Perry Land System by Aldrick et al. (1992).

The surface soils are generally dark greyish brown hard-setting gravelly loamy sands to sandy loams. Stones, up to 100 mm diameter, are a common feature. A bleached sub-surface (typically pale brown to pale brownish grey) horizon of similarly textured material occurs abruptly, overlying mottled yellow and brown clays, at about 30 to 50 cm. Large columnar structure is common in the upper subsoil. Clays or sandy clays, generally mottled with red colours, normally continue to at least one metre depth, often accompanied by gravel and stones. The soils in this unit are most likely to be classified as Yellow or Brown Sodosols using the Australian Soil Classification. Soil Site GP83 is an example of a Brown Sodosol near Fernbank.