Week 3 - Topic 5 - Geology of Sydney Basin

Question 1

What are the three main rock types?

Answer 1

1. Igneous Rocks
2. Sedimentary Rocks
3. Metamorphic Rocks

Igneous rocks are formed from the solidification of molten rock, sedimentary rocks from the lithification of fragments, and metamorphic rocks from altered minerals due to heat and pressure.

Question 2

What are the two categories of igneous rocks?

Answer 2

1. Volcanic rocks (extrusive)
2. Plutonic rocks (intrusive)

Examples include basalt for volcanic rocks and granite for plutonic rocks.

Question 3

How are sedimentary rocks formed?

Answer 3

By lithification of rock/organic fragments

Sedimentary rocks can be classified into clastic, biogenic, and chemical types.

Question 4

What are the three types of sedimentary rocks?

Answer 4

1. Clastic
2. Biogenic
3. Chemical

Examples include sandstones and shales for clastic, limestones and coal for biogenic, and rock salt and gypsum for chemical.

Question 5

What is physical weathering?

Answer 5

Breaks large rocks into smaller particles (gravel, sand, silt)

This process does not change the chemical composition of the rock.

Question 6

What is chemical weathering?

Answer 6

Changes rock’s chemical nature

It is the main source of clay fractions and is more active in tropical/temperate climates.

Question 7

What is the geographic extent of the Sydney Basin?

Answer 7

South to Batemans, North to Newcastle, West to Jenolan Caves, Northwest to Goulburn Valley

This defines the area where Sydney’s geological features can be studied.

Question 8

What is the most common rock type in the Sydney region?

Answer 8

Sandstone

Sandstone produces sandy soils, with light brown sandy loam topsoil and tan sandy clay subsoil.

Question 9

What is the second most common rock type in Sydney?

Answer 9

Shale

Shale is found in inner suburban areas and produces clay soils.

Question 10

What are the other rock types found in the Sydney region?

Answer 10

• Coal
• Conglomerate
• Basalt/Dolerite
• Limestone

Coal is found at basin edges, conglomerate at Lake Macquarie and Central Coast, basalt in small parts of Blue Mountains, and limestone in the Jenolan Caves area.

Question 11

List the layers of the Sydney Basin from oldest to youngest.

Answer 11

• Hunter Coal Measures/Illawarra Coal Measures (295-252 mya)
• Narrabeen Group (255-247 mya)
• Hawkesbury Sandstone (247-242 mya)
• Wianamatta Group (240-210 mya)

Each layer has distinct properties and compositions.

Question 12

What type of soil is derived from sandstone?

Answer 12

Topsoil: Loamy sand
Subsoil: Sandy loam

Sandstone-derived soils are generally nutrient poor.

Question 13

What type of soil is derived from shale?

Answer 13

Topsoil: Clay loam
Subsoil: Clay

Shale-derived soils have better fertility than sandstone soils.

Question 14

What type of soil is derived from basalt?

Answer 14

Topsoil: Loam/clay loam
Subsoil: Loamy clay

Basalt-derived soils are nutrient rich with good water holding capacity.

Question 15

Fill in the blank: The ESpade tool can be used to view soil landscapes and characteristics for specific locations in _______.

Answer 15

Sydney

The ESpade tool is available at environment.nsw.gov.au/eSpade2Webapp.