Tilba Cemetery Headland Intrusions

Latitude -36.342977, Longitude 150.099034

Located in the Eurobodalla Region of NSW, nearest town Central Tilba

Source: A journey through the earth history of Australia's Coastal Wilderness Courtesy of Sapphire Coast Tourism.

Link to Detailed Map

Heading south along the Princes Highway, instead of turning right to Central Tilba, turn left at the turnoff. Follow the road signs to the cemetery located at the end of the road next to the beach known as Wallaga Beach. There is a car park and access to the beach just below the second grave enclosure. The geological site is the headland south of the cemetery and is best visited at low tide.

Approach the headland, and the distinctive features of almost-vertical beds of brownish Ordovician sedimentary rocks stand out. These very old rocks are located at many other places along the coast. Here, look at the igneous dykes and quartz veins intruding the Ordovician beds. The first clue is the white slash in the centre of the photo.

The white dykes are chemically similar to the nearby Dromedary intrusion, and were intruded at the same time as the Dromedary mass (Mount Dromedary, is now called Gulaga).

Close up view of the white dykes. On the same headland there is another network of dykes of granite composition, quite unlike the chemistry of Dromedary, and a granite outcrop in the sand. The granite is intruding into, breaking up and assimilating the Ordovician beds.

In the photos below the dark grey rock is turbitite, an Ordovician sedimentary rock, and the fawn coloured rock is the invading granite. The white rock cutting across the centre of the turbidite is not another dyke but a vein composed of quartz, common in these highly deformed old rocks. The turbidites were deposited on the deep ocean floor from very fluid sand and mud-laden avalanches cascading down continental slopes. Sand and mud gradually settled out of suspension.

Successive avalanches are often separated in time, but can build up thick piles of sediment. The same processes occur today down the continental slope off eastern Australia.

Study of this complex geological site has identified the granites as part of the Bega Batholith. The nearest granite outcrop, the Cobargo Pluton, is 14km away. The two sets of dykes on this headland are separated by some 323 million years.

Instead of returning to the cemetery, walk to the headland at the northern end of the beach. This headland is entirely made up of the Cretaceous lavas of the Dromedary province encountered at 1080 Beach (the next headland north).

Getting There

From the lower cemetery enclosure to the southern headland and back allow around 1hour 15 minutes, considerably longer if you are walking to the northern headland. Make sure it is low tide.