G22 - Healesville Gorge - Outcrop, Levees and Crevasse

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 (external link) section of the Geological Society of Australia website for details of geological heritage reports, and a bibliography.

Location:	AMG Ref: 655300. 500 metres south of the Healesville railway tunnel.	Humevale Formation outcrop at (A) in river bluff and porphyry dyke in river bank at (B). The small lake at (C) is in an old sand quarry.
Access:	From Yarra Glen - Healesville Road.
Geology:	Outcrops of quartz porphyry associated with the Tarrawarra ring dyke system occur on the south bank of the Yarra River. Siltstone of the Humevale Formation is seen in the high bluff at outcrop A.
Geomorphology:	The Yarra floodplain narrows at this site where it crosses the ridge extending north from the Warramate Hills. On leaving this narrow sector, the Yarra is flanked by natural sandy levee banks as it emerges onto the extensive Yarra flats. Remnants of an entire earlier channel can be traced on the northern margin of these flats but the river now occupies the southern side of the floodplain. A faint reticulate channel system can be seen on aerial photographs and is the only flood crevasse identified in this study.
	The small lake adjacent to the channel is in the base of an old sand quarry and is fed by groundwater.
Significance:	Local. The site marks the eastern edge of the Yarra flats and displays outcrop of the basement rocks that bound the floodplain. The levee bank sector is more distinctive than elsewhere in the study area and includes traces of the flood crevasses.
Management:	Class 2. The outcrops need no special protection but the levee banks and crevasse could be obscured by sand extraction which should not be permitted. The area from which sand is currently being taken could continue to provide this resource without detracting from the significance of the adjacent areas.

Image: Upper Yarra Sites of Significance

Old flood crevases (arrowed) from abandoned
channel at Site G22

Levee bank (L-L), and backswamp (B)
at G22.

Healesville Gorge - Outcrop, Levees and Crevasse.

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