TV6 Toolern Creek - Silcrete

This information has been developed from the publications:

Sites of Geological and Geomorphological Significance in the Western Region of Melbourne (1986) by Neville Rosengren
Sites of Geological and Geomorphological Significance on the Coast of Port Phillip Bay (1988) by Neville Rosengren.
Sites of Geological and Geomorphological Significance in the Shire of Otway (1984) by Neville Rosengren.

Geological heritage sites, including sites of geomorphological interest and volcanic heritage sites, are under regular revision by the Geological Society of Australia, especially in the assessment of significance and values. Reference should be made to the most recent reports. See the Earth Science Heritage section of the Geological Society of Australia website (external link) for details of geological heritage reports, and a bibliography.

Location	Toolern Vale - 863378. Shire of Melton. Valley of Toolern Creek from Benson Road to McPhersons Road, 11 km north of Melton.	TV6 - Silcrete in Toolern Creek.
Access	Benson Road and McPhersons Road off Gisborne to Melton Road.
Ownership	Private land.
Site Description	Toolern Creek above Benson Road flows in a small gorge cut into Newer Volcanics basalt. The volcanics are strongly fractured with both vertical and horizontal joints and scree and gravel line the valley floor.
	At the mouth of the gorge (100 m upstream from the road bridge), a 1.5 m layer of silcrete is exposed beneath the basalt. The silcrete is a very tough but brittle indurated sandstone developed by weathering and silica enrichment of fine sandy sediments. Here the silcrete lies directly on Ordovician sediments with outcrop in the stream channel near the bridge.
	There are further silcrete outcrops along Toolern Creek south of Bensons Road including one massive outcrop at the McPhersons Road bridge. Road cuttings on Bensons Road 500 m northeast of the bridge also expose clear sections of basalt and silcrete overlying Ordovician sediments.
Significance	Regional. The site is an excellent example of silcrete development at the base of the Newer Volcanics and above the Ordovician sediments. It displays the influence of the hard silcrete outcrops on stream valley development.
Management	The stream frontage should not be subject to earthmoving or construction works that could conceal the outcrops described. In the event of rebuilding the bridges, the design of the bridge, approaches and roadways should be such to retain the clarity of the outcrops. Any upgrading or widening of Benson Road should be designed to maintain a clear vertical section of the 3 formations.

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