What Lies Beneath – Unconformity

‘Unconformity’ is a geological term that describes a point when two rock masses from different time periods meet. For geologist, Dr Wolf Mayer, the discovery that an example of such a rock formation had survived after the construction of new Parliament House and was safely preserved underneath Capital Hill was very exciting.

New Parliament House sits atop a geological puzzle known as an unconformity.

Dr Mayer runs guided tours through the tunnels beneath Parliament House to give visitors the chance to see a puzzling piece of Canberra’s ancient history. What he points out initially goes unnoticed if you are not a rock expert on the tour, but he explains to us that the rocks underneath Parliament represent something rare and curious; a gap in geological records of about 10 million years.

On the tour Dr Mayer tells us a story from what he sees in the rocks. The story is of a clash of tectonic plates some 430 million years ago that forced the land up and above the surface of the ocean. But the next thing Dr Mayer can read from the rocks is harder to explain. It appears the rocks were submerged again after existing for millions of years above sea level. It would seem that the ocean flooded back in, covering the rock formations but there is no clue in the rocks as to how or why this may have happened. This gap in what we can deduce from the rocks is known as the ‘unconformity’.

Prior to the development of new Parliament House, geologists were easily able to access the point at which the ‘unconformity’ occurred to study it. However, there were concerns that once the land had been developed nothing would be left of the phenomenon. The serendipitous fact that we can still access this mysterious piece of the distant past has been inspiring for Dr Mayer and his tours are aimed at sharing his passion.

Dr Mayer takes The Unconformity Tour beneath the political centre of the country where he contextualises Canberra and brings some of its ancient history to life.

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