LSWW23

Site: LSWW23	Land Unit: Dundas Trachyte
*Aust. Soil Class.:* Melanic, Black FERROSOL / DERMOSOL (confidence level 4).

General Land Unit Description:
There are a few isolated outcrops of Jurassic trachyte in the north-western portion of the study area, with the largest outcrop being north east of Coleraine. There are also some colluvial slopes on the edge of trachyte outcrops around the Dundas and Merino Tablelands.

The trachyte hills often have rock outcrop and reasonably shallow soils on the crests and upper slopes. The main soil type on the upper slopes is a Brown Sodosol although Chromosols also occur and they are commonly sodic at depth. The soils on the colluvial slopes tend to be black cracking clays (Vertosols) or Black Vertic Sodosols. These soils are similar to the black soils of the dissected Merino Tablelands land unit. The soils on these slopes are a complex mix of different soil forming processes.

This site is on the steeply dissected hills and rises leading to the Glenelg River and it’s tributaries. Trachyte is often found outcropping through the Tertiary sediments and in association with older sediments and granite. Due to the steep slopes the lower slopes often have an accumulation of colluvial material deposited on top.

Site Description:

Geology: Jurassic basalt	Landform pattern: Hill
Position in landscape: Lower slope	Internal drainage: Moderately well drained

Soil Profile Morphology

A1	0-10 cm	Very dark grey (2.5Y3/1) light clay; strong polyhedral structure, (peds 10-20 mm), breaking to strong blocky structure, (peds 5-10 mm), strong consistence when dry. pH 6.5.
	Subsoil
B21	10-40 cm	Very dark grey (10YR3/1) light clay; strong polyhedral structure, (peds 10-20 mm), breaking to strong blocky structure (peds 5-10 mm), very strong consistence when dry. pH 6.9
B22	40-70 cm	Very dark grey (10YR3/1) heavy clay; strong angular blocky structure, (peds 20-50 mm), breaking to strong polyhedral structure, (peds 5-10 mm), very strong consistence when dry. pH 7.3.
B23	70-120 cm	Light olive brown (2.5Y5/3) heavy clay; many dark grey and yellow brown mottles, structure and consistence similar to horizon above. pH 7.9.
B24	120+ cm	Light olive brown (2.5Y5/3) heavy clay; many mottles, structure and consistence similar to above, a few ferruginised iron nodules.

Key Profile Features

Strong structure throughout
Uniform clay soil
Mottling in the deeper subsoil

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