Timbarra (Symbol: Ta)

Profile No. 45 (Aldrick, et al 1992)

Geology
Palaeozoic granites, granodiorites, gneissic metamorphics and related some coarse crystalline plutonic rocks.

Landform
In the context of this report, the Timbarra map unit encompasses rolling to steep hills with an elevation range of about 60 to 700 m and an elevation range of 90 to 300 m. The slope gradients exceed 15% but are generally much steeper, commonly 30 – 50%. This Map unit may be subdivided into three components: moderate to steep slopes are the most extensive component, crests and narrow open depressions.



Original vegetation
Grassy woodland.

Soils
Component 1: Soils on moderate to steep slopes
The soils on the slopes are mostly shallow brown texture contrast soils with slightly acid sandy loam surfaces and slightly alkaline sandy clay subsoils. Weathering rock occurs before 1.2 m.

Component 2: Crests
The crests have varying amounts of exposed rock. The soils are believed to be similar to those described above but the depth to rock is shallower.

Component 3: Narrow open drainage lines
Aldrick et al. (1992) describes the soils as being quite variable, mainly brown or reddish brown sandy loam to sandy clay loam over stratified alluvium.

Profile No. 45 (Aldrick et al, 1992)

Location: Ensay	Geo. Ref.: 577800E 5862200N
Australian Soil Classification: Haplic, Eutrophic, Red CHROMOSOL	Brown texture contrast soil
General landscape description: Steep low hills
Geology: Palaeozoic granite
Site description: Lower east facing slope (37% slope)
Land use: Grazing on annual pasture
Native vegetation: Open forest
Map unit: Timbarra (previously mapped as Dargo, Component 1, but too steep for new unit definition)

Surface soil			Typical shallow soil on granite south of Dargo
A11	0-27 cm	Dark brown (7.5YR3/2); sandy loam; apedal; hard consistence, dry; 5% granite fragments up to 8 mm; clear wavy change to:
A12	27-50 cm	Strong brown (7.5YR5/6); gritty sandy loam; apedal; hard consistence when dry; 15% granite fragments up to 8 mm; clear wavy change to:
Subsoil
B2	50 -80 cm	Yellowish red (5YR5/6); sandy clay; moderate coarse (25 mm) angular blocky structure; firm consistence moist; 25% quartz and weathering feldspar crystals up to 3 mm and dark mica grains;
C	80 – 90+ cm	Strong brown (7.5YR5/6); sandy clay loam; moderate medium (20 mm) angular blocky structure; friable consistence moist; passing to weathering granite;
Key profile features Bordering on a gradational soil but the slight texture contrast between the surface (A) horizons and the subsoil (B) horizons makes this a borderline texture contrast soil.

Horizon	Depth cm	Field texture	pH water	EC dS/m	Gravel %	Coarse sand %	Fine sand %	Silt %	Clay %	Field cap. % w/w	Wilt. point % w/w	PAW* water % w/w
A11	0-10	SL	5.9	<0.05	6	31	43	10	13
A11	10-20	SL		<0.05	12
A12	30-50	SL	6.7	<0.05	22	37	42	11	11
B2	60-80	SC	7.0	<0.05	18	30	25	15	31
C	80-90	SCL	7.1	<0.05	5	29	27	14	28

Depth	OrgC#	Total N	Exch. Al	Exchangeable cations cmol (+) /kg							Ca:Mg	ESP
cm	%	%	ppm	Ca	Mg	K	Na	Total	H	CEC
0-10	2.2	0.16		4.0	1.0	0.5	0.05	5.6	8.2	13.7	4
10-20
30-50				4.4	0.8	0.3	0.08	5.6	2.2	7.8	5.5
60-80				10.6	2.5	0.5	0.3	13.9	4.3	18.2	4.2	2
80-90				11.3	2.9	0.5	0.4	15.1	4.8	19.9	3.9	3

• As the soils are sandy, the plant available water capacity would be very low. However, plants would be able to utilise light rain after the soils are dry.
• Sheet and rill erosion would be high and common where the topsoil is exposed.
• Soil depth in the steep cleared drainage lines is likely to be very shallow with considerable exposed rock.