Site location mapLOCATION: 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 m 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 gravels 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.


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.


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

Location of Siluran/Basalt Unconformity at Sumner Park Brunswick

Photograph 12. Location of Site 8.

Basalt/Silurian unconformity at Sumner Park Brunswick

Photograph 13. Basalt/Silurian contact at site 8.