14 million years ago many large freshwater lakes covered this area. Due to volcanic activity, the water was warm which encouraged a prolific growth of algae. These tiny creatures have a skeleton of silica which, after their death, form a deposit on the bottom of the lake. This deposit of diatomaceous earth was mined at Chalk Mountain near Bugaldie. The picture of the open cut mine clearly shows the different layers. The bottom 3 meters is top quality material, whereas the layers above are alternating between volcanic ash and diatomaceous earth. It is the bottom layer that contains most of the fish fossils, while the plant fossils are mostly found in the top layers. The lot is covered by a layer of basalt, which was the end of the lake.

Leaf fossils of nothofagus (Antarctic beech) indicate that the climate at that time was very wet.

The surrounding area is covered by a massive layer of jurassic sandstone, the “Pilliga Beds”. Fossils from this time include species of Pentoxylon australica, Agathis jurassica and others.