Natural Landscape

Sandstone escarpment Photo V. O’Brien Sydney Red Gum (Angophora costata) Photo J. Finlason Mangroves at low tide Photo V. O’Brien Heath vegetation on Eastern slope Vegetation of Nanny Goat Hill Photo D. Bassett The valley’s rugged sandstone cliffs were Natural landscape originally covered with just about every The Valley’s geological history dates back to type of general plant the Triassic period, some 237 million years ago community in the when Australia was part of the supercontinent Sydney region. Open Gondwana. A mighty river carrying large heath and Scribbly Gum forest covered the ridge amounts of sandy sediment flowed over much tops. The valley sides of the area that is now Sydney and its environs to were clothed in rich schlerophyll shrubland form what is known as Hawkesbury sandstone. scattered with Sydney Red Gums. Nearer the Within this sandstone is preserved evidence creek were dense woodlands of Blackbutt, of the massive flood waves, concentrated with Bloodwood, and Sydney Peppermint. Over sand and mud, forming sedimentary structures the creek flats were Swamp Mahoganies, such as trough and tabular crossbeds and She-oaks, Paperbarks, Lilly Pillies and recumbent cross bedding. Cabbage-tree Palms. Beside the lower salty reaches of the creek arose dense stands of Mangroves and extensive Reedlands and Saltmarshes. In the upper freshwater parts of the creek clustered a temperate rainforest of Coachwood At the western end of the valley, the landscape becomes and Water Gum. more gently undulating and the Hawkesbury Sandstone is overlain by shales and silts from the Wianamatta group. THE The Wolli Creek Valley formed through processes of erosion ST PETERS and weathering that commenced during the last ice age, LAB The recumbent crossYR beddingINTH at Undercliffe approximately 20,000 years ago. The Wolli Creek system ODO tells us a lot about the forces that created NT the has continued to erode and cut through the Hawkesberry Valley. But thanks to other discoveries, we also Sandstone creating the valley we see today. Wolli Creek is know something about the plants and animals found there in the distant past. The most spectacular now a small creek, described in the early 1800s as a ‘run of ponds of freshwater’, it becomes a raging torrent after happened not far from the Valley at St Peters heavy rains causing extensive flooding. where, in 1910, the fossilised skeleton of a rare giant salamander-like amphibian, about 2.7 metres long, known as a Labyrinthodont (now known as This 1833 description of the forests on the estate of Paracyclotosaurus davidi ‘Bexley’, on the high ridge above what is now Earlwood, speculate that it may have died after something fell on its head, such as a large) was tree found. branch. Scientists It has shows how Europeans were beginning to appreciate the area. been dated to the Middle Triassic, about 235 … numerous and valuable quantities of million years ago. Today it is in the Natural timber have been preserved on the estate … History Museum, London, leaving the stringy bark, iron bark, blackbutt, mahagony, Australian Museum holding only a cast shingle-oak, turpentine, red, blue and white of one of the state’s most important gum, honeysuckle for ship and boat builders, fossil discoveries. and white wood of a large size, so much used by coach builders and others. Paracyclotosaurus davidi Illustration courtesy of the Australian Museum Wolli Creek Preservation Society 2011 www.wollicreek.org.au .

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