LOCATION: YARRA 50MV0112 E21400 N28150 to E21180 N28510 Merri Creek valley extending for approximately 1 km south of Barry Road.
ACCESS: Barry Road, Ari Drive, Malcolm Place.
OWNERSHIP & MUNICIPALITY: Public Land owned by Melbourne Water, in City of Humeand City of Whittlesea.
SITE DESCRIPTION: The site includes cliffs, alluvial and bedrock terraces and minor floodplains. The major geomorphological and geological feature is a 15 metre high cliff on the right bank of the Merri Creek. This cliff exposes an unconformity between the bedrock of Silurian sedimentary rocks and the Newer Volcanics basalts. The Silurian rocks outcrop in the channel of the creek and along with large fallen basalt blocks, form rapids and small cascades when the rivers is in high flow. A number of small potholes are eroded into the sandstone beds, some with basalt grinding pebbles still in place. In the cliff face can be seen the fossil soil developed on the Silurian rocks and now buried and baked by the lava flow. A calcareous precipitate forming a massive deposit on parts of the lower cliff is a result of carbonate rich waters issuing as springs at the base of the basalt. Different flow structures and joint patterns in the lava indicate more than one flow unit to be present in the cliff face.
The northern parts of the site also provide very clear exposures of massive, jointed, vesicular and ropy lava. Zeolites up to 10 mm in diameter are infilling many cavities in the basalt rock.
The slopes of the valley upstream of the steepest part of the gorge have 3 distinct terrace levels, the lower terrace being a bedrock terrace with an alluvial veneer.
SIGNIFICANCE RATING: STATE
This gorge is one of the most distinctive topographic features of the Merri Creek catchment and a major element of the landscape of the northern region of Melbourne. It is an outstanding example of an unconformity between basalt and the Silurian bedrock - a very common geological feature but one which may be seen in only a few localities. Both rock types and the contact in the cliff face on the right bank of the Merri Creek are well displayed and a number of related features (buried soil, ground water leakage and carbonate deposition) are also evident. The site is the best example of this geological feature in the Melbourne region and is a superior display than the better-known similar feature at Organ Pipes National Park.
When viewed in conjunction with the retarding basin and adjacent geological sites, it provides a complex of major geological and geomorphological significance. The site has the potential for an interpretation centres for the landscape of the Merri Creek along the lines of that at Organ Pipes National Park.
SITE SENSITIVITY, THREATS, POTENTIAL UTILISATION
CLASS 2. Broadly this is a robust site but positive action is needed to maintain diversity and enhance the considerable educational potential of the area. Apart from a massive weed control problem and clearing of rubbish and dumped vehicle debris, there is a need for roads and parking areas, footpaths, viewing platforms and footbridges across the Merri Creek to give formalised and controlled access. There is a vandalism and security issue to be addressed. However, Organ Pipes National Park has demonstrated that reserves adjacent to urban areas can be rehabilitated. "Friend" groups along with naturalist and other organisations could be involved in this programme.
REFERENCES: None known
Photograph 37. Unconformity at Barry Road gorge (photo Neville Rosengren approx 1993).
Photograph 38. Terraces north of Barry road gorge (photo Neville Rosengren approx 1992).
Photograph 39. Basalt north of Barry Road gorge