Somersby Falls: (33° 24′ 3″S, 151° 16′ 13″E) just a 3 km diversion off the Great North Walk proper takes you to this area. Observation platforms provide excellent views of the 8 metre falls and the rainforest. After a steep track with many steps, the Falls Walking Track descends to Floods Creek past two stages of waterfalls and ends at the base of the falls. There is also evidence of tool grinding grooves in the rocks.
The Great North Walk Companion extract- page 185
Both Wondabyne and Piles Creek have given their names to types of Australian sandstone: the Piles Creek range of Australian sandstone features stone density from 2.3 to 2.4 tonnes per cubic metre.
We are heading downhill through the bush to the creek and cross over at the mossy rocks. “Reservoir Road, which we just crossed, leads to a reservoir and dam,” I interrupt my own narrative, “on the Mooney Mooney Creek around 20 km from its junction with the Hawkesbury River. The catchment is around 40 square km and water is pumped to the Somersby Water Treatment Plant. I wonder if the dam wall is sandstone… there are so many quarries around here…perhaps not … now, where was I?”
“Something complicated about stone — sounded like geology to me,” says my companion with a grimace.
“Right — the Wondabyne sandstones have densities that make them attractive and widely sought after for building. As far as I can figure out, the Wondabyne quarry operated from around 1868 through to as recently as the 1980s. And then with a big fanfare it was reopened specially to acquire stone for St Mary’s Cathedral which, although started in 1868, only had its spires completed in time for the Sydney Olympics in 2000.”