Soils on Basaltic Terrain

Flat to gently undulating basaltic plains with poorly drained sodic duplex soils predominating. This extensive plain occurs in the north around Meredith and with a total area of 48 km², represents 6.8% of the Shire.

Qbg is similar to Qbgd but the climate is wetter. (The land is used mainly for grazing, with some cropping). Extensive flat or low lying areas are particularly poorly drained and are subject to seasonally high watertables and some surface ponding.

SOILS
The most common soil occurs in Component 1. The heavy clay subsoil is slowly permeable, highly expansive and may be 1 to 4 m thick. While the Factual Key classifies the soil on the relatively thin B1 horizon which is dark, the overall impression from a deep excavation is of a yellowish grey duplex soil.

Mottled, Dark Grey Sodic Duplex Soils - Coarse Structure

Factual Key: Dd 2.43/CL, 10-60 cm/basalt, 30-400 cm

Horizon	Depth (cm)	Description
A1	0-20	Brownish black (10YR 3/2) when moist; clay loam; weak subangular blocky 7 mm; consistence when slightly moist is firm; pH 5.4; sharp boundary.
A2	20-50	Greyish yellow brown (10YR 5/2) when moist; clay loam; apedal and massive; consistence when slightly moist is firm; some buckshot gravel increasing to 60-80% at the A2/B21 interface - average size 4 mm; pH 6.0; sharp boundary.
B21	50-100	Brownish black (10YR 3/3) when moist; heavy clay with yellow mottling with a moderate sub-angular blocky 50 mm breaking down to a strong angular blocky 2 mm; consistence when slightly moist is extremely firm; pH 7.5; diffuse boundary.
B22	100-200+	Greyish yellow brown (10YR 4/2) when moist; heavy clay; strong subangular blocky 80 mm breaking down to a strong angular blocky 2 mm; consistence when slightly moist is extremely firm; may contain basalt floaters; pH 8.0.

COMPONENT Proportion %	1 95	2 3	3 2
COMPONENT Proportion %	1 95	2 3	3 2
CLIMATE
Rainfall(av.) mm	Annual 610 - 660
Temperature(av.) °C	Annual 12
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Extensive, slightly dissected plains in the north of the Shire
Elevation (range) m	240 - 365
Local relief (av.) m	2
Drainage pattern	Dendritic
Drainage density km/km²	0.5
Land form	Plain
Position on land form	Long gentle upper slopes	Depression	Stony rise
Slope (range) %, slope shape	1-3 ; Straight	1-2 ; Straight	2-5 ; Convex
NATIVE VEGETATION
Structure	Woodland (?)
Dominant species	E. ovata, E. viminalis, E, rubida, E. obliqua		E. viminalis, E. rubida, E. obliqua, E. ovata
SOIL
Parent material	In-situ weathered rock	Alluvium	In-situ weathered rock
Description	Mottled dark-grey sodic duplex soils coarse structure	Black clay soils, uniform texture, coarse structure	Red shallow stony gradational soils
Factual key	Dd 2.43	Ug 5.1	Gn 3.11
Surface texture	Clay loam	Clay	Clay loam
Permeability	Low	Low	High
Depth (range) m	1.0	4.0	0.2 - 0.5
LAND USE
	Grazing, occasional cropping (cereal)		Grazing
SOIL DETERIORATION
Critical land features	Hard setting surfaces, slowly .permeable subsoils	Clay soils in drainage lines Seasonal high watertables	Slopes
Processes	Overland flow, periodic waterlogging	Overland flow, periodic waterlogging	Overland flow, leaching
Forms	Surface compaction, minor sheet erosion	Surface compaction, minor rill erosion	Sheet erosion, nutrient decline

Qbgd - Plains with Duplex Soil on Quaternary Basalt. Drier than Qbg

Flat to gently undulating basalt plains scattered throughout the southern two-thirds of the Shire. Total area is 29 km², representing 4.1% of the Shire.

Qbgd is similar to Qbg except that the climate is drier and River red gum (E. camaldulensis) is more common.

The land is particularly poorly drained in the flatter areas, having seasonally high watertables and areas of surface ponding. It is used for grazing and cereal cropping.

SOILS
The major soil is that of Component 1. The heavy clay of the subsoil is impermeable, highly expansive and may be 0.5 to 3 m thick. While the Factual Key classifies the soil on the relatively thin B1 horizon which is dark, the overall impression from observation of a deep excavation is of the yellowish-grey clay of the duplex soil.

Mottled Dark Grey Sodic Duplex Soils - Coarse Structure

Factual Key: Dd 2.43/CL, 10-60 cm/basalt, 30-400 cm

Horizon	Depth (cm)	Description
A1	0-20	Brownish black (10YR 3/2) when moist; clay loam; weak sub-angular blocky 7 mm; consistence when slightly moist is firm; pH 5.4; sharp boundary.
A2	20-50	Greyish yellow brown (10YR 4/2) when moist; clay loam; apedal and massive; consistence when slightly moist is firm; some buckshot gravel throughout the A2 increasing to 50-70% buckshot average size 4 mm at the A2/B1 interface; pH 6.0; sharp boundary.
B21	50-80	Brownish black (10YR 3/1) when moist; heavy clay with yellow mottling with a moderate subangular blocky 50 mm breaking to a strong blocky 2 mm; consistence when slightly moist is extremely firm; pH 7.5; diffuse boundary.
B22	80-150+	Greyish yellow brown (10YR 4/2) when moist; heavy clay; strong sub-angular blocky 80 mm breaking down to a strong angular blocky 2 mm; consistence when slightly moist is' extremely firm; may contain basalt floaters; pH 8.0.

COMPONENT Proportion %	1 95	2 3	3 2
COMPONENT Proportion %	1 95	2 3	3 2
CLIMATE
Rainfall(av.) mm	Annual 530 - 610
Temperature(av.) °C	Annual 12 - 13
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Extensive, slightly dissected plains
Elevation (range) m	61 - 265
Local relief (av.) m	8
Drainage pattern	Dendritic
Drainage density km/km²	0.7
Land form	-
Position on land form	Long gentle upper slopes	Depression	Stony rise
Slope (range) %, slope shape	1-3 ; Straight	1-2 ; Straight	2-5 ; Convex
NATIVE VEGETATION
Structure	Woodland ?
Dominant species	E. camaldulensis, E. leucoxylon, E. melliodora	E. camaldulensis
SOIL
Parent material	In-situ weathered rock	Alluvium	In-situ weathered rock
Description	Mottled dark grey sodic duplex soils coarse structure	Black clay soils, uniform texture coarse structure	Red shallow stony gradational soils
Factual key	Bd 2.43	Ug 5.1	Gn 3
Surface texture	Clay loam	Clay	Clay loam
Permeability	Low	Low	High
Depth (range) m	1.0 - 3.0		0.2 - 0.5
LAND USE
	Grazing, cropping (cereal)		Grazing
SOIL DETERIORATION
Critical land features	Hard setting surfaces, slowly permeable subsoils	Seasonal high watertables, low lying areas	Gradient
Processes	Overland flow, periodic waterlogging	Overland flow, periodic waterlogging	Overland flow
Forms	Minor sheet erosion, surface compaction	Billing, minor gully erosion in disturbed soil. Salting	Minor sheet erosion

Qbgw - Stony Plains with Duplex Soils on Quaternary Basalt

Flat to gently undulating basalt plains similar to Qbgd but with sandy topsoils. Several large areas occur in the southern half of the Shire. The total area is 27.0 km², representing 3.9% of the study area.

The sand in the topsoil does not originate from the basalt parent material, but is a wash and, in some cases a wind-blown addition. The subsoil is a heavy, sodic clay of low permeability and high shrink-swell potential (cracks on drying), often containing basalt floaters. It can be a problem for building foundations. The land has seasonally poor drainage - especially on the flatter areas.

The main land use is grazing, with some cereal cropping.

SOILS
The most common soil type occurs on Component 1. The amount of sand in the A1 and A2 horizons vary.

Mottled Dark-grey Sodic Duplex Soils - Coarse Structure

Factual Key: Db 2.43 (Some Dd 2.43)/LS-SCL, 20-50 cm/basalt 100-200 cm

Horizon	Depth (cm)	Description
A1	0-15	Greyish brown (7.5YR 4/2) when moist, loamy sand; apedal and massive; consistence when moist is friable; pH 4.5; clear boundary.
A2	15-40	Greyish yellow brown (101R 5/2) when moist, with brown rootline mottles; loamy sand; apedal single-grained; consistence when moist is loose; pH 4.0; abrupt boundary.
B1	40-60	Dark brown (10YR 3/3) when moist, with orange mottles; medium clay; moderate sub-angular blocky 30 mm; consistence when wet is plastic; pH (.0; gradual boundary.
B2	40-100+	Dark brown (10YR 3/3) when moist; with yellow mottles; heavy clay; moderate angular blocky 80 mm; consistence when moist - very plastic; when dry - very hard; may contain basalt floaters; pH 9.0.

COMPONENT Proportion %	1 95	2 3	3 2
COMPONENT Proportion %	1 95	2 3	3 2
CLIMATE
Rainfall(av.) mm	Annual 500 - 580
Temperature(av.) °C	Annual 13
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Slightly dissected plains throughout the southern part of the Shire
Elevation (range) m	61 - 249
Local relief (av.) m	14
Drainage pattern	Dendritic
Drainage density km/km²	0.6
Land form	Long gentle slopes	Drainage line	Stony rise
Position on land form	Slopes	Depression	-
Slope (range) %, slope shape	1-3 ; Straight	1-2 ; Straight	2-5 ; Convex
NATIVE VEGETATION
Structure	Woodland (?)
Dominant species	E. leucoxylon
SOIL
Parent material	In-situ weathered rock	Alluvium	In-situ weathered rock
Description	Mottled dark grey sodic duplex soils, coarse structure	Black clay soils, uniform texture, coarse structure	Red shallow stony gradational soils
Factual key	Db 2.33 and Db 2.43	Ug 5.1	Gn 3
Surface texture	Sandy loam	Clay	Clay loam
Permeability	Moderate-low	Low	High
Depth (range) m	1.0 - 3.0		0.2 - 0.5
LAND USE
	Grazing, occasional cropping (cereal)		Grazing
SOIL DETERIORATION
Critical land features	Hard setting surfaces, slowly permeable subsoils	Clay soils in drainage line	Slopes
Processes	Overland flow, periodic waterlogging	Overland flow, periodic waterlogging	Overland flow, leaching
Forms	Surface compaction, sheet erosion	Surface compaction, minor rill erosion	Sheet erosion, nutrient decline

Qbb - Steep-sided Valley with Duplex Soil on Quaternary Basalt

Scarps and alluvial flats in the north of the Shire associated with creeks that have out into the basalt plain. The unit totals 7.7 km², representing 1.1% of the Shire.

The size of the alluvial flats is variable throughout the unit; where they are large enough, they have been mapped as a separate unit, Qya. The slopes of the scarps vary in steepness, but are generally rocky and have shallow stony soils: There may be some risk of landslips when unconsolidated sediments below the basalt are exposed by the scarp. Also, where the dark clayey soils are deep, slumping may occur particularly in batters. The main land use is grazing.

This unit is similar to Qbbd but the climate here is wetter.

SOILS
The most common soil, an example. of which is described below, occurs on the slopes (Component 1). It is usually a brown duplex but there may be areas of a red gradational soils or black clays where the soil is deeper.

Shallow Brown Duplex Soils

Factual Key: Db 1.11/CL, 20-40 cm/basalt, 10-45 cm

Horizon	Depth (cm)	Description
A	0-20	Brownish black (7.5YR 3/2) when moist; clay loam; weak subangular blocky 5 mm; consistence when dry is slightly hard; 20% stones of parent material (4-30 cm average diameter); pH 6.0; abrupt boundary.
B	20-30	Dark brown (10YR 3/3) when moist; medium clay; moderate to strong angular blocky 4 mm; consistence when dry is hard; 00% stones of parent material (10-50 cm average diameter) and 5% of buckshot; pH 6.0; abrupt boundary.
R	30+	Weathering basalt.

COMPONENT Proportion %	1 60	2 40
COMPONENT Proportion %	1 60	2 40
CLIMATE
Rainfall(av.) mm		Annual 610 - 660
Temperature(av.) °C		Annual 12
GEOLOGY
Age, rock		Pleistocene basalt
TOPOGRAPHY
Landscape		Scarps beside main creeks in the north of the Shire usually including the creek alluvium
Elevation (range) m		200 - 350
Local relief (av.) m		15
Drainage pattern	-	-
Drainage density km/km²	-	-
Land form	Steep valley side with local rock outcrop	Creek bed and flood plain
Position on land form	-	-
Slope (range) %, slope shape	10-35 ; Convex	1-5 ; Straight
NATIVE VEGETATION
Structure		Open forest
Dominant species		E. viminalis, E. ovata
SOIL
Parent material	In-situ weathered rock	Unconsolidated sedimentary and in-situ weathered rock
Description	Shallow brown duplex or gradational soils	Black clay soils, uniform texture, coarse structure
Factual key	Db 1.11	Ug 5.1
Surface texture	Clay loam	Clay
Permeability	Moderate	Low
Depth (range) m	0.3 - 1.2	1.0 - 2.0
LAND USE
		Grazing
SOIL DETERIORATION
Critical land features	Slope, hard setting surfaces	Seasonal high watertables Poorly drained site, low permeability
Processes	Overland flow	Overland flow, periodic waterlogging
Forms	Minor sheet and rill erosion, low landslip hazard	Streambank erosion, surface compaction

Qbsd - Stony Rises with Gradational Soils on Quaternary Basalt drier than Qbs

Low stony rises on basalt. There are several small patches in the south of the Shire but only one extensive area, which is to the west of Lethbridge. The total area of 7.3 km² represents 1.0% of the Shire.

The small areas of Qbsd occur as stony rises on the basalt plains or as isolated remnants of basalt in other units. The large area west of Lethbridge has a slightly higher elevation than the surrounding basalt and Tga units. The degree of surface stoniness varies considerably and many areas have been cleared to allow for grazing and some cropping. Rock piles and stone fences are common around these areas.

Irrespective of surface stoniness, all areas have shallow black uniform soils, usually with large quantities of rock, overlying hard bedrock. The soils are not very permeable but drainage is better than in other gently sloping basalt units because there is surface runoff to surrounding lower land.

SOILS
The most common soil is found on both Components 1 and 2, and is usually a Ug 5.12, although others occasionally do occur.

Stony Black, Clay Soils, Uniform Texture, Coarse Structure

Factual Key: Ug 5.12/LC-MC; 10-20 cm/basalt, 50-100 cm

Horizon	Depth (cm)	Description
A1	0-10	Black (10YR 2/1) when moist; light medium clay; strong angular blocky 10 mm; consistence when moist is firm; 5-70% surface stones; pH 7.0; clear boundary.
B	10-60	Brown black (10YR 3/1) when moist; heavy clay; strong angular blocky 3 mm: consistence when wet, very plastic; 10-50% basalt stones and boulders; pH 8.5.
R	60+	Basalt rock.

COMPONENT Proportion %	1 90	2 10

CLIMATE
Rainfall(av.) mm	Annual 500 - 600
Temperature(av.) °C	Annual 12
GEOLOGY
Age, rock	Pleistocene basalt
TOPOGRAPHY
Landscape	Stony rise area west of Lethbridge
Elevation (range) m	110 - 235
Local relief (av.) m	10
Drainage pattern	Dendritic
Drainage density km/km²	0.2
Land form	Stony rise	Drainage line
Position on land form	Slopes	Depression
Slope (range) %, slope shape	1-5 ; Convex	1-2 ; Straight
NATIVE VEGETATION
Structure	Woodland ?
Dominant species	E. camaldulensis
SOIL
Parent material	In-situ weathered rock	In-situ weathered rock with some alluvium
Description	Stony black clay soil, uniform texture, coarse structure	Black clay soil, uniform texture, coarse structure
Factual key	Ug 5.12 or Ug 5.14	Ug 5.1
Surface texture	Clay	Clay
Permeability	Low	Low Low
Depth (range) m	0.5 -.1.0	1.0 - 2.0
LAND USE
	Grazing
SOIL DETERIORATION
Critical land features	Slope gradient	Slope gradient
Processes	Overland flow	Overland flow
Forms	Minor sheet erosion, nutrient decline	Minor rill erosion

Qbc - Plains with Clay Soils on Quaternary Basalt

Small areas of black, cracking, clay soils on gently undulating basalt plains in the northern section of the Shire. The unit covers only 0.3 km² or 0.04% of the survey area - one of the smallest units.

It is similar to Qbcd, but the climate is wetter. The land-use is mainly cereal cropping and grazing. The heavy clay soil retains moisture well but is difficult to work into a fine seedbed except at optimum moisture content.

The unit generally has a low erosion hazard, and could be used more intensively. The clay, however, is highly expansive and has a high plasticity index - special foundations for constructions are required.

SOILS
The soil is fairly homogeneous throughout this unit.

Black Clay Soils, Uniform Texture - Self Mulching

Factual Key: Ug 5.14/LC-MC, 10-30 cm/basalt, 80-160 cm

Horizon	Depth (cm)	Description
A	0-20	Black (10YR 2/1) when moist; medium clay; strong angular blocky 15 mm; consistence when moist is very firm; pH 7.0; clear boundary.
B	20-80	Brownish black (10YR 3/1) when moist; heavy clay; strong angular blocky 2 mm; consistence when wet, very plastic; occasional basalt stones and boulders; pH 8.5; diffuse boundary.
C	80-120	Grey (2.5YR 4/0) when moist; heavy clay; strong angular blocky 1 mm; consistence when wet is very plastic; occasional basalt stones and boulders; pH 8.0.
R	120+	Basalt rock at variable depth

COMPONENT Proportion %	1 100
COMPONENT Proportion %	1 100
CLIMATE
Rainfall(av.) mm	Annual 650 - 685
Temperature(av.) °C	Annual 12
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Slightly dissected plains in the north of the Shire
Elevation (range) m	228 - 267
Local relief (av.) m	5
Drainage pattern	Dendritic
Drainage density km/km²	1.7
Land form	Plain
Position on land form	-
Slope (range) %, slope shape	2-10 ; Convex
NATIVE VEGETATION
Structure	(?)
Dominant species
SOIL
Parent material	In-situ weathered rock
Description	Black clay soils. uniform texture, coarse structure - self mulching
Factual key	Ug 5.14
Surface texture	Heavy clay
Permeability	Moderate
Depth (range) m	0.8 - 1.6
LAND USE
	Cropping (cereal), occasional grazing
SOIL DETERIORATION
Critical land features	Slope
Processes	Overland flow
Forms	Minor sheet erosion

Qbbd - Steep-sided Valleys with Duplex Soil on Quaternary Basalt. Drier than Qbb

Moderate to very steep scarps caused by creeks cutting into the basalt plain. Includes the alluvium of the creek unless these areas are sufficiently large to be mapped as a separate unit. There are about a dozen occurrences of the unit throughout the southern half of the Shire, including some sections along the stony lip of the Moorabool River near She Oaks. The total of 8.2 km², represents 1.2% of the Shire. It is similar to Qbb in the north but the climate of Qbbd is drier.

The slopes are usually stony. There is generally not much erosion evident despite the steep slopes because a protective grassland cover develops readily on the fertile, moderately permeable soils. Gullying will occur rapidly if the soil is exposed to concentrated runoff.

Where the soils are deeper or the basalt overlies unconsolidated material, landslips may occur. Grazing and recreation are the main land uses.

SOILS
The soil description below is representative of Component 1.

Shallow Brown Duplex Soils

Factual Key: Db 1.11/CL, 20-40 cm/basalt, 10-45 cm

Horizon	Depth (cm)	Description
A	0-20	Brownish black (7.5YR 3/2) when moist; clay loam; weak subangular blocky 5 mm; consistence when dry is slightly hard; 20% stones of parent material (8 cm average size); pH 6.0; abrupt boundary.
B	20-30	Dark brown (10YR 3/3) when moist; medium clay; moderate to strong angular blocky 4 mm; consistence when dry is hard; 80% stones of parent material (30 cm average size) and 5% of buckshot; pH 6.0; abrupt boundary.
R	30+	Weathering basalt.

COMPONENT Proportion %	1 70	2 30

CLIMATE
Rainfall(av.) mm	Annual 510 - 580
Temperature(av.) °C	Annual 13
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Scarp beside main creek including the river channel in places
Elevation (range) m	30 - 198
Local relief (av.) m	38
Drainage pattern	Dendritic
Drainage density km/km²	1.2
Land form	Scarp with local rock outcrop	Creek bed
Position on land form	Slope	Flood plain
Slope (range) %, slope shape	10-30 ; Convex	1-3 ; Straight
NATIVE VEGETATION
Structure	Woodland (?)
Dominant species	E. camaldulensis
SOIL
Parent material	In-situ weathered rock	Unconsolidated sedimentary and in-situ weathered rock
Description	Shallow brown duplex or gradational soils	Black clay soils, uniform texture, coarse structure
Factual key
Surface texture	Clay loam	Clay
Permeability	High	Low
Depth (range) m	0.5 - 1.5	1.0 - 2.5
LAND USE
	Grazing
SOIL DETERIORATION
Critical land features	Steep slope, hard setting surfaces	Poorly drained site, low permeability
Processes	Overland flow, sub surface flow	Overland flow, periodic waterlogging
Forms	Minor sheet and rill erosion, low landslip hazard	Streambank erosion, surface compaction

Tbd - Slopes with Clay Soils on Tertiary Basalt

Isolated crests and slopes near Maude, with moderate to gentle gradients, on Tertiary basalt (older, well weathered basalt). The total area of 1.3 km², amounts to (only) 0.2% of the Shire.

The black clayey soils, being fertile and having good water holding capacity, are suited to the common uses of cropping and market gardening. However, they do require optimum moisture for seedbed preparation and, once cultivated, deep rilling can occur very rapidly. Under grazing, those soils grow good pasture and, being well protected, are quite stable.

SOILS
The most common soil type (described below) is a uniform, black, cracking clay. There are, however, odd areas of chocolate or red-brown gradational soils.

Dark Uniform Clay Soils

Factual Key: Ug 5.1 / LC-MC, 10-70 cm/older basalt, 10-80 cm.

Horizon	Depth (cm)	Description
A11	0-20	Brownish black (7.5YR 3/2) when moist; light medium clay; moderate subangular blocky, 5mm; consistence when moist is friable; pH 8.0.
A12	20-50	Brownish black (7.5YR 3/2) when moist; light medium clay; strong subangular blocky; consistence when moist is friable1 pH 8.5.
C	50+	Rotting basalt (greenish grey) with lime.

COMPONENT Proportion %	1 50	2 45	3 5
COMPONENT Proportion %	1 50	2 45	3 5
CLIMATE
Rainfall(av.) mm	Annual 560 - 600
Temperature(av.) °C	Annual 12
GEOLOGY
Age, rock	Tertiary basalt
TOPOGRAPHY
Landscape	Isolated occurrences of gentle to moderate slopes near Maude
Elevation (range) m	170 - 190
Local relief (av.) m	15
Drainage pattern	Dendritic
Drainage density km/km²	1
Land form	Crest	Slopes	Drainage line
Position on land form	Highest	Medium	Lowest
Slope (range) %, slope shape	1-5 ; Convex	5-15 ; Convex-Straight	1-3 ; Concave
NATIVE VEGETATION
Structure	Woodland ?
Dominant species	E. leucoxylon
SOIL
Parent material	In-situ weathered rock
Description	Dark uniform clays and sodic chocolate gradational soils	Dark uniform clays and sodic chocolate gradational soils	Yellow mottled dark sodic duplex soils, coarse structure
Factual key	Ug 5.1 - Gn 3.12	Ug 5.1 - Gn 3.12	Dd 2.43
Surface texture	Clay - clay loam	Clay - clay loam	Clay loam
Permeability	Moderate	Moderate	Low
Depth (range) m	0.5 - 1.0	0.3 - 0.8	1 - 1.5
LAND USE
	Cropping - grazing		Grazing
SOIL DETERIORATION
Critical land features	Slope gradient, soil permeability	Slope gradient, soil permeability	Seasonal high watertable Soil permeability, sodic soil, position on landscape
Processes	Overland flow	Overland flow	Overland flow, period waterlogging
Forms	Moderate sheet erosion when fallowed	Moderate sheet erosion	Surface compaction

Qbf - Plain with Clay Soil and duplex Soils and Quaternary Basalt

Extensive flat to gently undulating plains located in the centre of the Shire, along the Midland Highway. Having a total area of 46 km², it occupies 6.6% of the Shire. Black cracking clays, although sporadic in occurrence, are more common than in Qbgd.

Their occurrence may be related to the depth of bedrock. Cropping and grazing are the main uses, with the black cracking clays favoured for cropping.

SOILS
The soil description for Component 2 (the black uniform clay) is the same as for Map Unit Qbcd. The soil description below refers to Component 1.

Mottled, Dark Sodic Duplex Soils - Coarse Structure

Factual Key: Dd 2.43/CL, 10-60 cm/basalt, 30-400 cm

Horizon	Depth (cm)	Description
A1	0-20	Brownish black (10YR 3/2) when moist; clay loam; weak subangular blocky 7 mm; consistence when slightly moist is firm; pH 6.0; sharp boundary.
A2	20-50	Greyish yellow brown (10YR 5/2) when moist; clay loam; apedal and massive; consistence when slightly moist is firm; buckshot gravel increases to 40-70% at the A2/B21 interface; pH 6.0; sharp boundary.
B21	50-110	Brownish black (10YR 3/1) when moist; heavy clay with yellow mottling with a moderate subangular blocky 50 mm breaking down to a strong angular blocky 2 mm; consistence when slightly moist is extremely firm; pH 7.5; diffuse boundary.
B22	110+	Greyish yellow brown (10YR 4/2) when moist; heavy clay; strong subangular blocky 80 mm breaking down to a strong angular blocky 2 mm; consistence when slightly moist is extremely firm; pH 8.0

COMPONENT Proportion %	1 50	2 40	3 10

CLIMATE
Rainfall(av.) mm	Annual 510 - 630
Temperature(av.) °C	Annual 13
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Plain in the centre of Survey Area along the Midland Highway
Elevation (range) m	60 - 260
Local relief (av.) m	2
Drainage pattern	Dendritic
Drainage density km/km²	0.4
Land form	Plain
Position on land form	Plain		Depression lines
Slope (range) %, slope shape	1-3 ; Straight		1-2 ; Concave
NATIVE VEGETATION
Structure	Woodland (?)
Dominant species	E. camaldulensis, E. leucoxylon, E. melliodora
SOIL
Parent material	In-situ weathered rock		Alluvium mainly from basalt
Description	Mottled dark sodic duplex soils, coarse structure	Black clay soils, uniform texture, coarse structure	Black cracking clays, coarse structure
Factual key	Dd 2.43	Ug 5.1	Ug 5.1
Surface texture	Clay loam	Light to medium clay	Medium clay
Permeability	Very low	Very low	Very low
Depth (range) m	1.0 - 2.0	0.5 - 1.0	1.5 - 2.5
LAND USE
	Cropping and grazing		Grazing
SOIL DETERIORATION
Critical land features	Hard setting surfaces
Processes	Overland flow
Forms	Minor sheet erosion

Qbs - Stony Rises with Gradational Soils on Quaternary Basalt

Stony rises on the basalt plains in the north of the Shire. There are only a few localities large enough to be mapped separately at this scale; smaller stony areas elsewhere have been identified by using the symbol “st”.

The total area of 0.3 km² represents only 0.04% of the total study area. The soil is relatively fertile but the surface basalt stones and boulders generally limit its use to grazing.

SOILS
The soils of this unit are generally very shallow (Um). When soil fills deep crevices in the rock, a Gn (as described) or a Db soil may develop. In extreme cases, a grey heavy clay (in the B22 horizon) may be found.

Red Shallow Stony Gradational Soils

Factual Key: Gn 3.11/L-LC, 5-40 cm/basalt, 5-70 cm.

Horizon	Depth (cm)	Description
A	0-15	Brownish black (5YR 3/2); when moist; gravelly loam; weak subangular blocky 5 mm; consistence when moist is friable; 5% small stones (basalt); pH 5.5; diffuse boundary.
B	15+	Dark reddish brown (5YR 3/4) when moist; clay loam to light clay; strong angular blocky 1 mm; consistence when moist is friable; 40-60% stones (basalt); pH 6.0.
In many instances the B horizon is only present where the soil is deep in crevices in the basalt.

COMPONENT Proportion %	1 100
COMPONENT Proportion %	1 100
CLIMATE
Rainfall(av.) mm	Annual 610 - 660
Temperature(av.) °C	Annual 12
GEOLOGY
Age, rock	Pleistocene basalt
TOPOGRAPHY
Landscape	Scattered stony areas in the north of the Shire
Elevation (range) m	270 - 340
Local relief (av.) m	1
Drainage pattern	-
Drainage density km/km²	-
Land form	Stony areas
Position on land form	-
Slope (range) %, slope shape	1-4 ; concave scarps, straight tops
NATIVE VEGETATION
Structure	Woodland ?
Dominant species	E. viminalis
SOIL
Parent material	In-situ weathered rock
Description	Red shallow stony gradational soils
Factual key	Gn 3.12
Surface texture	Clay loam
Permeability	High
Depth (range) m	0.1 - 1
LAND USE
	Grazing
SOIL DETERIORATION
Critical land features	Slope, shallow permeable soil
Processes	Overland flow; leaching
Forms	Low sheet erosion, nutrient decline

Qbcd - Plains with Clay Soils on Quaternary Basalt. Drier than Qbc

Gently sloping areas of black uniform, self-mulching clays on basalt. There are four areas (near She Oaks) totalling 1.1 km² and comprising 0.1% of the Shire. This unit supports similar land uses to Qbc; however, the climate here is drier. The black soils are quite fertile and are often used for onion growing and other cropping.
Sheet erosion of fallow land can occur. During the summer, deep cracks appear as the clay dries out and shrinks; the magnitude of this shrink-swell property can be a problem for foundation construction.

SOILS
As there is only one component, the soil description below represents the whole unit.

Black Clay Soils, Uniform Texture - Self-Mulching

Factual Key: Ug 5.14/LC-MC, 10-30 cm/basalt, 80-160 cm

Horizon	Depth (cm)	Description
A	0-20	Black (10YR 2/1) when moist; medium clay; strong angular blocky 15 mm; consistence when moist is firm; pH 7.0; clear boundary.
B	20-80	Brownish black (10YR 3/1) when moist; heavy clay; strong angular blocky 2 mm; consistence when wet, very plastic; occasional basalt stones and boulders; pH 8.5; diffuse boundary.
C	80-120	Grey (2.5YR 4/0) when moist; heavy clay; strong angular blocky 1 mm; consistence when wet is very plastic; occasional basalt stones and boulders; pH 8.0.
R	120+	Basalt rock.

COMPONENT Proportion %	1 100
COMPONENT Proportion %	1 100
CLIMATE
Rainfall(av.) mm	Annual 610 - 630
Temperature(av.) °C	Annual 2
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Slightly dissected plains
Elevation (range) m	185 - 251
Local relief (av.) m	3
Drainage pattern	Dendritic
Drainage density km/km²	1.7
Land form	Plain
Position on land form	-
Slope (range) %, slope shape	1-4; Convex
NATIVE VEGETATION
Structure	(?)
Dominant species
SOIL
Parent material	In-situ weathered rook
Description	Black clay soils, uniform texture, coarse structure - self mulching
Factual key	Ug 5.14
Surface texture	Heavy clay
Permeability	Moderate
Depth (range) m	0.8 - 1.5
LAND USE
	Market garden (onions), cropping (cereal), occasional grazing
SOIL DETERIORATION
Critical land features	Slope
Processes	Overland flow
Forms	Minor sheet erosion

Qbbd - Steep-sided valley with Duplex Soils on Quaternary Basalt

Moderate to very steep scarps caused by creeks cutting into the basalt plain. Includes the alluvium of the creek unless these areas are sufficiently large to be mapped as a separate unit. There are about a dozen occurrences of the unit throughout the southern half of the Shire, including some sections along the stony lip of the Moorabool River near She Oaks.

The total of 8.2 km², represents 1.2% of the Shire. It is similar to Qbb in the north but the climate of Qbbd is drier.

The slopes are usually stony. There is generally not much erosion evident despite the steep slopes because a protective grassland cover develops readily on the fertile, moderately permeable soils. Gullying will occur rapidly if the soil is exposed to concentrated runoff. Where the soils are deeper or the basalt overlies unconsolidated material, landslips may occur. Grazing and recreation are the main land uses.

SOILS
The soil description below is representative of Component 1.

Shallow Brown Duplex Soils

Factual Key: Db 1.11/CL, 20-40 cm/basalt, 10-45 cm

Horizon	Depth (cm)	Description
A	0-20	Brownish black (7.5YR 3/2) when moist; clay loam; weak subangular blocky 5 mm; consistence when dry is slightly hard; 20% stones of parent material (8 cm average size); pH 6.0; abrupt boundary.
B	20-30	Dark brown (10YR 3/3) when moist; medium clay; moderate to strong angular blocky 4 mm; consistence when dry is hard; 80% stones of parent material (30 cm average size) and 5% of buckshot; pH 6.0; abrupt boundary.
R	30+	Weathering basalt.

COMPONENT Proportion %	1 70	2 30

CLIMATE
Rainfall(av.) mm	Annual 510 - 580
Temperature(av.) °C	Annual 13
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Scarp beside main creek including the river channel in places
Elevation (range) m	30 - 198
Local relief (av.) m	38
Drainage pattern	Dendritic
Drainage density km/km²	1.2
Land form	Scarp with local rock outcrop	Creek bed
Position on land form	Slope	Flood plain
Slope (range) %, slope shape	10-30 ; Convex	1-3 ; Straight
NATIVE VEGETATION
Structure	Woodland (?)
Dominant species	E. camaldulensis
SOIL
Parent material	In-situ weathered rock	Unconsolidated sedimentary and in-situ weathered rock
Description	Shallow brown duplex or gradational soils	Black clay soils, uniform texture, coarse structure
Factual key
Surface texture	Clay loam	Clay
Permeability	High	Low
Depth (range) m	0.5 - 1.5	1.0 - 2.5
LAND USE
	Grazing
SOIL DETERIORATION
Critical land features	Steep slope, hard setting surfaces	Poorly drained site, low permeability
Processes	Overland flow, sub surface flow	Overland flow, periodic waterlogging
Forms	Minor sheet and rill erosion, low landslip hazard	Streambank erosion, surface compaction

Qbgs - Stony Plains with Duplex Soil on Quaternary Basalt

Flat to gently undulating, stony, basalt plains, mainly in the south-east corner. The 62 km² total area represents 8.9% of the Shire; the third-largest unit.

The most striking feature is the quantity of surface stones. In less extreme cases, these have often been picked up to allow for agriculture and grazing and put in piles or used for stone fences. Apart from the black clayey soils which may occur where the surface is particularly rocky, the soil is similar to, but stonier than in Qbgd. In both cases, however, the clay has low permeability, high plasticity and high shrink-swell potential.

The most common land use is grazing.

SOILS
The most common soil occurs on Component 1.

Stony Mottled Dark Grey Duplex Soils - Coarse Structure

Factual Key: Dd 2.43/CL-LC, 10-30 cm/basalt, 50-100 cm

Horizon	Depth (cm)	Description
A1	0-10	Brownish black (10YR 3/2) when moist; clay loam; weak subangular blocky 5 mm; consistence when dry is hard; surface stones 1 to 30%; pH 6.0; abrupt boundary.
A2	10-15	Greyish yellow brown (10YR 5/3) when moist; clay loam; apedal and massive; consistence when dry is hard; 1-25% basalt stones; pH 6.0; abrupt boundary.
B21	15-35	Brownish black (10YR 3/1) when moist; heavy clay; moderate subangular blocky 40 mm; consistence when slightly moist is very firm; 1-25% basalt stones; pH 7.5; diffuse bGreyish yellow-brown (10YR 4/2) when moist; heavy clay; moderate subangular blocky 60 mm; consistence when slightly moist is very firm; 1-60% basalt atones; pH 8.5.oundary.
B22	35-60+

COMPONENT Proportion %	1 75	2 30	3 5
COMPONENT Proportion %	1 75	2 30	3 5
CLIMATE
Rainfall(av.) mm	Annual 500 - 560
Temperature(av.) °C	Annual 13
GEOLOGY
Age, rock	Pleistocene, basalt
TOPOGRAPHY
Landscape	Stony plains south of Shire
Elevation (range) m	30 - 85
Local relief (av.) m	7
Drainage pattern	Dendritic
Drainage density km/km²	0.4
Land form	Stony plain	Plain	Drainage line
Position on land form	Upper slope (?)	Lower slope (?)	Depression
Slope (range) %, slope shape	1-4 ; Convex	1-3 ; Straight	1-2 ; Straight
NATIVE VEGETATION
Structure	Woodland ?
Dominant species	E. camaldulensis
SOIL
Parent material	In-situ weathered rock	In-situ weathered rook	Alluvium
Description	Stony, mottled dark grey sodic duplex soils, coarse structure	Mottled dark grey sodic duplex soils, coarse structure	Black clay soil; uniform textures coarse structure
Factual key	Dd 2.43	Dd 2.43	Ug 5.1
Surface texture	Clay loam	Clay loam	Clay
Permeability	Low	Low	Low
Depth (range) m	0.5-1.0	1.0-2.0	1.5
LAND USE
	Grazing
SOIL DETERIORATION
Critical land features	Hard Betting surfaces, slowly permeable subsoils	Hard setting surfaces, slowly permeable subsoils	Clay soils in drainage lines
Processes	Overland flow	Overland flow, periodic waterlogging	Overland flow
Forms	Minor sheet erosion, surface compaction	Minor sheet erosion, surface compaction	Minor sheet erosion, surface compaction

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