IT21

Site: IT21	Land Unit: Dundas Trachyte
*Aust. Soil Class.:* Sodic, ?, Brown CHROMOSOL (confidence level 3)

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.

Site Description:

Slope: 5.5%	Geology: Jurassic trachyte
Landform pattern: Undulating rises	Position in landscape: Upper slope
Internal drainage: Moderately well drained

Soil Profile Morphology

A11	0-25 cm	Dark brown (10YR3/3) sandy clay loam, medium subangular blocky structure (2-5 mm), very weak consistence when moderately moist, pH 6; gradual transition to:
A12	25-35 cm	Dark greyish brown (10YR4/2) clay loam, weak subangular blocky structure (2-5 mm), very weak consistence when moderately moist, pH 6; gradual transition to:
A13	35-55 cm	Dark greyish brown (10YR4/2) clay loam, weak subangular blocky structure (2-5 mm), very weak consistence when moderately moist, pH 6.5; diffuse transition to:
	Subsoil
B2	55-75+ cm	Brown (10YR5/3) medium clay loam, moderate subangular blocky structure (5-10 mm), weak consistence when moderately moist, pH 7.

Key profile features:

Strong texture contrast between topsoil and subsoil

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