Site 8 Sumner Park, Brunswick - Silurian/Basalt Unconformity

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 5000/04.07 E22470 N17310.
	Right bank just above mean water level 50 metres north of the arched footbridge across Merri Creek. Near the SEC Brunswick Terminal Station and 150 metres south of Albert Street.
Access:	Albert Street and Merri Path.
Ownership & Municipality:	Public Land, City of Brunswick.
Site Description:	The site is along an artificial channel sector where a formerly meandering course of the Merri Creek has been straightened at Sumner Park. The deep, narrow cut exposes Silurian sandstones and mudstones which on the right bank are overlain by weathered basalts. The contact between Silurian and basalt is an inclined plane representing one side of an ancestral (pre-basaltic) Merri Creek valley. In places, ancient stream gavels in the form of rounded pebbles of quartz and Silurian sandstone lie between the basalt and the Silurian rocks. At higher levels, the weathered Silurian strata is crushed and contorted where it has been overridden by the lava flow. Basalt structures just above the level of the ancient river bed resemble pillow lavas (elongate rounded rock masses 40 to 60 cm long that form when basalt flows into water). Whether these are pillows, pahoehoe lava toes or weathering structures has not been investigated.
Significance Rating:	Regional.
	Geological unconformities are significant sites as they are definitive bench marks separating geological events. This site is one of very few in the Melbourne area where the base of the Newer Volcanics basalts are exposed. It marks the western edge of an ancestral Merri Creek and is an important site to display the complex features associated with burial of a former land surface by a lava flow.
Site Sensitivity:	Class 2.
	The area of the site is small and the weathered nature of the contacting formations makes them vulnerable to damage or removal. The contact is partly obscured by channel lining and vegetation growth. There is little risk of damaging erosion of the left bank at this site by floods of the Merri Creek (in contrast to the opposite bank where there is fill material) so the contact could be left exposed. Vegetation growth would need to be removed and periodically pruned to maximise the values of the site.
References:	None Known.

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