Sb8 Sunbury Municipal Tip - Volcanic/Sedimentary Contact

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

Location	Sunbury - 953413. Shire of Bulla. Entrance to Sunbury Tip 5 km northwest of Sunbury.	Sb8 - The contact (arrowed) between an intruding volcanic pipe (V) and the enclosing Palaeozoic sediments (S), Sunbury tip.
Access	Off Sunbury to Gisborne road.
Ownership	Crown land
Site Description	Excavation at the entrance to the pit now used for the Sunbury Tip reveals a contact between lava and the underlying Ordovician shales. The contact is a very sharp boundary where the sediments have been truncated by the moving lava, the contact dipping steeply towards the north. The lowermost lava is a thin layer of volcanic agglomerate changing abruptly into hard dense basalt. The contact may be a minor eruption pipe or a dyke rather than a lava flow.
Significance	Regional. The contact is unusual in that there is no baked soil on the Ordovician rocks beneath the lava. The exposure is very clear and not obscured by slope wash or soil as is generally the case in natural exposures.
Management	Dumped materials should be cleared away from the base of the section and the site should be kept clear in future. The managing authority should be notified of the significance of the site and requested to refrain from filling this section of the tip. As it forms part of the entrance to the tip, this could be done without reducing the capacity of the tip or requiring any major change in tip management.

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