Site 15 Edgars Creek, Coburg - Waterfall and Geological Structure

This information has been developed from one or more of these publications:

Sites of Environmental Significance in the Flood Plain of the Upper Yarra Valley Region (1983) by Neville Rosengren, Douglas Frood and Kim Lowe (as part of a study of Sites of Environmental Significance by the University of Melbourne for the then Upper Yarra Valley and Dandenong Ranges Authority).

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 for details of geological heritage reports, and a bibliography.

Location:	YARRA 5000/04.09 E21480 N22000
	Channel of Edgars Creek 50 m south of the footbridge and 75 m west of Ronald Street.
Access:	Ronald Street and Boyne Street.
Ownership & Municipality:	Public Land, City of Coburg.
Site Description:	The site is an outcrop of Silurian (Melbourne Formation) sandstone and mudstone overlain by alluvial deposits of Edgars Creek. The surface sandstone stratum is crossed by a dense network of tectonic joints. There are three persistent joint directions and several subordinate ones. The intersection of these joints is responsible for the irregular edge to the Silurian beds. Most joints are filled with red-brown iron oxide (limonite) which form thin, linear projections above the sandstone surface. The Silurian rocks dip gently to the north west, so stream flow is deflected down the dip slope and lies against the western bank of the channel. The channel is gradually migrating westward by undercutting the soft alluvial deposits that overly the Silurian rocks. There is a small waterfall where Edgars Creek flows across the truncated edge of the dipping beds. Beside this is a naturally eroding section of the Edgars Creek terrace deposits.
Significance Rating:	Regional.
	This is a small site but it presents an excellent and safely accessible exposure of the Melbourne Formation. It illustrates the dip of bedding surfaces, a joint system and secondary infill of fractures by limonite. It nicely illustrates a process of waterfall formation across a resistant bed and shows how this system gradually retreats upstream. There are few comparable sites in the Melbourne Metropolitan area.
Site Sensitivity:	Class 1.
	The site is being damaged by management vehicles using it as a ford across Edgars Creek. This use should be discontinued. The site should be left as an exposed and active stream channel as it forms a very clear illustration of the ancient and modern geology of Edgars Creek. It has potential as an interpretive and educational feature and provides a welcome natural element in an otherwise intensively managed landscape. No filling or channel works should be carried out. The minor erosion of the banks is a natural process and should be allowed to continue as it exposes the alluvium of the Edgars Creek terrace and floodplain.
References:	None known.

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