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GL162

Site: GL162Land Unit: Dundas Trachyte
Aust. Soil Class.: Melanic, Mottled-Subnatric, Brown SODOSOL (confidence level 1)

Soil pit GL162 landscapeGeneral 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 located on the edge of a small band of Trachyte, below granite (GL161). Rock outcrop is evident. A Trachyte hill is opposite this site. This site is an example of the common soil type that occurs to the north of the study area. The soils on the low hills and rises that have outcropping bedrock tend to be similar to this soil type although they are often shallower.

Site Description:

Slope: 8%Geology: Jurassic tracyte
Landform pattern: Undulating risesPosition in landscape: Upper slope
Internal drainage: Imperfectly drained

Soil Profile Morphology

A110-10 cmVery dark grey (10YR3/2) clay loam, weak to medium subangular blocky structure (5-50 mm), firm consistence when dry, very few small subangular to angular trachyte pebbles (2-6 mm), pH 5.6; diffuse transition to:Soil pit GL162 profile
A1210-40 cmBlack (5YR2.5/1) clay loam, weak subangular blocky structure (5-20 mm), firm consistence when moist, very few small subangular to angular trachyte pebbles (2-6 mm), pH 6.0; clear but wavy transition to:
A1340-65 cmDark reddish brown (10YR3/2) light clay, weak subangular blocky structure (20-50mm) to strong granular structure (<2 mm), weak consistence when wet, very plastic when wet, very few large subangular blocky trachyte pebbles (20-60 mm), pH 6.3; clear and wavy transition to:
Subsoil
B265-110 cmOlive brown (2.5Y4/4) heavy clay, many distinct medium yellowish brown (10YR5/6) mottles, medium polyhedral structure (5-20 mm), very plastic consistence when wet, very few large subangular blocky trachyte pebbles, pH 6.3; clear to abrupt and wavy transition to:
C110-150 cmWeathered Trachyte

Key profile features:

  • Deep organic topsoil
  • Strong texture contrast between topsoil and subsoil
  • Mottled subsoil
  • Marginally sodic subsoil
  • Deeper topsoil dispersive when worked when wet
Soil pit GL162 graphs
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