The Acton Peninsula Limestone Outrops are a significant group which extends 80-100m along the eastern shore of Acton Peninsula. The age of the limestone is Late Silurian (approximately 425 million years) and contains sparsely distributed fragmentary macro fossils of corals and shells. Very little limestone is now exposed in the area which makes this outcrop a special place to visit. These outcrops are the most accessible and continuous exposure of the limestone which induced Europeans to settle the area and name it the Limestone Plains.
Associated with the Acton Peninsula Limestone Outcrops are quartz rich gravels from the Tertiary (between 5 and 65 million years old). These gravels sit directly on top of the limestone and in some places have formed potholes that indicate that the Molonglo River once flowed over this site. The ancient water level is about 25m above the height that the river was before the formation of Lake Burley Griffin.
These rocks tell a fascinating tale about our heritage. The presence of limestone here was one of the determining factors in the settling of the area we now call Canberra. Allen Mawer in his recently published book, Canberry Tales: An Informal History (Arcadia, 2012) explains that this limestone is literally older than the hills, having been laid down as deep sea sediment some 420 million years ago. The outcrops position en route to many of the cultural attractions in Acton, and their scenic bush setting (with views towards the lake and Commonwealth Bridge), should allow the limestone outcrop and the trail leading to it to become a significant feature of the landscape for residents and tourists alike.
Source: Australian Heritage Database. Read more about the Limestone Outcrops on the Australian Heritage Database.
To log your visit to this site, please email me information about the outcrop you can see looking west at GZ:
1. Describe the colours you can see in this outcrop of limestone.
2. Estimate the height of the rock outcrop in front of GZ, looking west.
I love to see photos of cachers exploring this area. If possible, post a photo of yourself or your group, at the limestone outcrop. Please make sure your photo does not provide answers for the above questions.