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Marong map unit Tfc2

Back to: A Land Capability Study of the Rural City of Marong

Map Unit:	Tertiary fan, moderate slope, 2	Map Unit Symbol:	Tfc2
		% of Study Area:	0.04

General Description:
Colluvial fans developed on the southern slopes of the metamorphic aureole ridge overlying granodiorite. The soils are dominantly yellow duplex with fine sandy loam topsoils, hardsetting, bleached A2 horizons and extremely mottled clay subsoils. Many quartz and metamorphosed sedimentary fragments occur on the soil surface and throughout the profile. In the subsoil, the combination of clay and gravel has produced a compacted layer. Variations include fewer coarse fragments within the profile, particularly on lower slopes. Drainage lines within this unit often expose granodiorite boulders and so have been classified as granitic.


Site characteristics:

Parent material age:	Tertiary	Depth seasonal watertable:	> 5 m
Lithology:	Sedimentary	Potential recharge to groundwater:	Moderate
Landform Pattern:	Undulating hills	Flooding risk:	Nil
Element:	Slope	Drainage:	Well drained
Slope common:	20%	Depth to hardrock:	> 1.5 m
Slope range:	10-32%
Rock outcrop:	0%

Major vegetation: Grey Box, Yellow Box, Red Stringybark, Golden Wattle, Lightwood, Hedge Wattle, Spreading Wattle

Present land use: Native pasture

Land degradation:	Water erosion		Wind erosion	Salting	Acidification
	Sheet/rill	Gully
Susceptibility	Very high	Moderate	High	Low	High
Incidence	High	Moderate	High	Low	Low

Soil profile characteristics:

Permeability (measured - average, range):	510, 330 - 650 mm/day
Permeability (estimated):	-
Available water capacity:	287 mm H2O
Linear shrinkage (B horizon):	12.4%

Soil profile description:

A1	0-14 cm	Brownish black (10YR3/2) fine sandy loam, weak structure, subangular blocky peds 5-10 mm, rough fabric, moderately weak consistence, many medium sized subangular metamorphic and quartz gravel fragments, moderate organic matter, pH 6.2. Clear transition to
A2	14-44 cm	Dull yellowish brown (10YR5/4) hardsetting fine sandy loam, bleached (10YR7/4) when dry, massive, earthy fabric, moderately weak consistence, a few medium sized subangular metamorphic and quartz gravel fragments, pH 5.4. Abrupt transition to
B	45-112 + cm	Dull yellow orange (10YR6/7) medium day, abundant medium sized distinct grey, orange, red and white mottles, moderate structure, subangular blocky peds 5-10 mm, rough fabric, moderately firm consistence, many coarse angular metamorphic and quartz fragments, pH 4.6.

Soil classification:

Factual Key (Northcote):	Dy 3.41
Australian Soil Classification:	Bleached-Mottled, Yellow, Kurosol; deep, thick, loamy, moderately gravelly
Unified Soil Group:	CL

Interpretation of soil analyses*

Horizon	pH	Gravel %	E.C. (salts)	Nutrient Status	P	K	Al	Organic Matter	Dispersibility
A1	6.2	44	VL	L	S	S	S	M	H
A2	5.3	19	VL	L	S	S	S	L	H
B	4.6	34	L	L	S	S	S	VL	L

VL : Very Low; L : Low; M : Moderate; H : High; VH : Very High; D : Deficient; S : Satisfactory; T : Toxic; **: Acid * See Appendix 4 for analytical results


Land capability assessment

Land Use	Class	Major limiting feature(s)/ landuse
Agriculture (CTS values)	C3T4S5	Very susceptible to sheet/rill erosion
Effluent disposal (septic tanks)	3	Moderate slope
Farm dams (earthen)	4	Moderately slope, low suitability of subsoils, lack of dispersion in subsoil, rapid permeability, high susceptibility to slope failure
Building foundations - slab	4	Moderate slope, high risk of slope failure
Building foundations - stumps/footings	4	High risk of slope failure
Secondary roads	4	Moderate slope, high risk of slope failure
Urban residential	4	Secondary roads, building foundations
Rural residential	4	Farm dams, secondary roads, building foundations

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