Earthcache II - the geology of WoolShed Creek, ACT EarthCache

In the 1840's a famous visiting geologist, Rev Clarke, travelling to the local Duntroon Homestead, stopped and looked at the outcrop of rocks in this small creek. He was astounded to find 'lamp shell' fossils (brachipods) and trilobites that he knew from back in his native Britian. There they had been identified as Silurian fossils - some 420 million years old. And on that day, these became the oldest recognised fossils in Australia (since them fossils have been found way older.....)

Back in the Silurian, Canberra was a shallow sea surrounded by active volcanoes. The muds in these shallow seas were the home to these brachiopods, as well as bryozoans and trilobites. When they died, they sank into the sea floor muds and became preserved as fossils.

Since the time the sea was filled in, mainly by volcanic eruptions, and the rocks uplifted and folded into broad folds. This folding has shattered the rocks, making them crumble easily, and some people in the past have come here to collect the fossils - now banned.

Fortunately a concerned group has had the area signposted...and this sign contains a lot more interesting geological information.

But heres a few more tid bits.....

The sandstone on the corners of the bridge pylons was once used to build a former bridge before this 1950s model. The sandstone has been transported from Sydney and is way out of place of the local rocks making up the rest of the bridge. No photos of the old bridge seem to exist, but who ever built it, probably the owners of Duntroon, spent a vast sum on bringing stone from so far away.

The iron pins that stick out of the rocks here are a dilema. Maybe they were part of the old bridge structure...or part of a film set for the Land of the Giants...who knows?

To log your visit to this site you need to measure the size of the lamp shell fossils you have seen (in mm. Send me by email your answer to geoaware (through profile above)