1 Australian Plants Society NORTH SHORE GROUP Ku-ring-gai Wildflower Garden SYDNEY SANDSTONE FLORA Formation of Sydney Sandstone 300 million years ago the rocks of Antarctica were uplifted to form a massive mountain range. At this time Australia and Antarctica, as part of Gondwana, were adjacent and situated near the South Pole. 200 to 250 million years ago erosion of these mountains produced vast quantities of sand that was carried by a huge river system across southern Australia from Antarctica until it reached the present east coast. It deposited the sand into the Sydney Basin and over millions of years these sands were consolidated into sandstone up to 50 metres thick. Geology of the Sydney area There are 3 major groups with minor layers. 1. Wianamatta Shale 2. Hawkesbury Sandstone (HS) 3. Narrabeen Sandstone The Wianamatta Group is essentially shale, acidic and moderately fertile. In Ku-ring-gai it is on the higher areas. Typical vegetation is found on the higher slopes of Sheldon Forest and Dalrymple Nature Reserve. Beneath the shale lies Hawkesbury Sandstone which supports a sandy acidic soil, pH 5.5 to 4. Did you know that? Sydney sandstone was formed over 200 million years ago. In spite of being low in nutrients, it has great diversity. Its area extends roughly from the Hunter River to the Shoalhaven River and to the western edge of the Blue Mountains.
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Australian Plants Society NORTH SHORE GROUP
Ku-ring-gai Wildflower Garden
SYDNEY SANDSTONE FLORA
Formation of Sydney Sandstone 300 million years ago the rocks of Antarctica were uplifted to form a massive mountain
range. At this time Australia and Antarctica, as part of Gondwana, were adjacent and
situated near the South Pole.
200 to 250 million years ago erosion of these mountains produced vast quantities of
sand that was carried by a huge river system across southern Australia from Antarctica
until it reached the present east coast. It deposited the sand into the
Sydney Basin and over millions of years these sands were
consolidated into sandstone up to 50 metres thick.
Geology of the Sydney area There are 3 major groups with minor layers.
1. Wianamatta Shale
2. Hawkesbury Sandstone (HS)
3. Narrabeen Sandstone
The Wianamatta Group is essentially shale, acidic and moderately
fertile. In Ku-ring-gai it is on the higher areas. Typical vegetation is
found on the higher slopes of Sheldon Forest and Dalrymple Nature
Reserve.
Beneath the shale lies Hawkesbury Sandstone which supports a sandy
acidic soil, pH 5.5 to 4.
Did you know that?
Sydney sandstone was formed over 200 million years ago.
In spite of being low in nutrients, it has great diversity.
Its area extends roughly from the Hunter River to the Shoalhaven River and to
the western edge of the Blue Mountains.
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Narrabeen Sandstone located under the Hawkesbury, is from an earlier time and has a
somewhat larger component of shale.
Area The Sydney area is located roughly from Newcastle to the Shoalhaven and west to the
western edge of the Blue Mountains, an area of 23000 square kilometres. It contains the
catchment of the Nepean-Hawkesbury Rivers (excluding the upper Wollondilly River).
In the centre of the Sydney area is the Cumberland plain with its shale soil. To the north
is the Hornsby Plateau, generally 200-300m above sea level. Here the major outcropping
rock is Hawkesbury Sandstone.
Soils Sandstone generally weathers to form grey/yellow sandy soils which are acidic with low
fertility. These support a very high diversity of plant species.
Although the KWG vegetation is essentially Hawkesbury Sandstone flora, it could be
influenced by the presence of Shale in some of the higher areas. Features include-
Tessellated pavements - Caused by weathering and erosion
Laterites- from iron and aluminium oxides, are remnants of a previous extensive
shale plateau surface. Identified by large irregular, rounded orange-red ironstone
nuggets. They provide some nutrients to the yellow soils and are able to support
low open forests. They are found on higher sandstone soils and in Ku-ring-gai
there are examples in the vicinity of KWG and St Ives Showground.
Tessellated pavement Laterites
Vegetation types
A variety of vegetation types are found in Sydney Sandstone including heath, scrub,
woodlands and open forest which is the predominant type where trees are up to 30 m
high with a canopy cover of 30-70 %. It is in this vegetation type where many of the
beautiful sandstone wildflowers are found. In the deeper valleys tall open forest and
rainforest are present.
Sandstone communities
Endangered Ecological Communities There are several Endangered Ecological Communities including Sydney Turpentine
Ironbark Forest (STIF) and Duffys Forest Ecological Community (DFEC) which have
components of Sandstone.
Areas of DFEC are found in KWG.
Components include the dominant canopy trees
• Eucalyptus sieberi (Black Ash or Silver top Ash)
• Corymbia gummifera (Red Bloodwood)
• Angophora costata (Sydney Red Gum)
• E. capitellata or E. oblonga (Stringybarks).
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Eucalyptus sieberi
Two major communities, Sydney Sandstone Ridgetop Woodland (SSRW) and
Sydney Sandstone Gully Forest (SSGF) are found in Sydney Sandstone.
SSRW is found on the more exposed ridges and plateaux with shallower soils interrupted
by outcrops of rock. Features found include tessellated pavements and laterites.
Characteristic tree species of SSRW in KWG are Corymbia gummifera, Eucalyptus
oblonga, E. haemastoma and E. racemosa. Patches of Banksia ericifolia and Hakea
teretifolia occur in open-scrub sites with poorly drained soil.
SSGF is generally confined to gullies and sheltered hillsides, particularly on the Southern
and Eastern aspects. It may have 3 units;
Open-forest/woodland where the main trees are E. piperita and Angophora
costata. Corymbia gummifera and Allocasuarina littoralis are also present.
Tall open-forest where the trees are E. pilularis and Syncarpia glomulifera. (This
assembly is not at KWG).
Closed forest with Ceratopetalum apetalum
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Ceratopetalum apetalum Tristaniopsis laurina Sandstone Gully Forest with closed canopy
Special plants • Melaleuca deanei Rare 3RC-
• Angophora crassifolia Restricted to the Ku-ring-gai plateau • Genoplesium baueri Rare 3RC- • Eucalyptus luehmanniana Rare 2RCa • Darwinia procera Rare 2RCa • Leucopogon amplexicaulis Restricted to the coastal districts of Sydney • Tetratheca glandulosa Vulnerable 2VC-
• Haloragodendron lucasii Endangered 2ECi •
(Key 2: Geographic range < 100km 3: Geographic range > 100km E: Endangered species in serious risk of disappearing within 1 or 2 decades . R: Rare in Australia but not currently considered endangered or vulnerable. V: Vulnerable not presently endangered – risk of disappearing over a longer period C: Population reserved – Ca : Adequately - C-: Adequacy unknown -Ci-: Inadequately reserved )