The rocks in front of you are Ordovician in age (about 475 million years old) and belong to layers known by geologists as the Pittman Formation.
These rocks were formed at the bottom of a deep sea (up to 100m deep) and sand and mud was moved into the area by huge underwater landslides called turbidity flows. The muds eventually turned into shale and the sands turned into sandstones.
Since then these rocks have been metamorphosed and folded. The shales became very fractured because they contained platey minerals. The sandstones became much harder.
The steep wall of this quarry is made up of the harder sandstone. The more sloping area is made up of the shale. However, most of the shale was removed and ground up into clay to make bricks.
Walk up the hill towards S 35 17.898 E 149 06.844. At this point you will find some great examples of the hard sandstone on the ground. This sandstone has many small white veins of the mineral quartz running through it.
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