The local quarry held 240 million years of history
Beacon Hill Oval and some nearby houses are located on part of what was a quarry, opened in 1910 primarily to provide raw material for brickmaking. The quarry worked a 7.5 metre thick shale lens within the Hawkesbury sandstone.
This shale had been laid down some 240 million years earlier in the Triassic period, as mud and sediment in a slow moving braided freshwater river system, when Australia was still part of the supercontinent Pangea. Fish who died in the river, and insects and plant leaves that fell into it, sank into the mud.
At the time that the quarry opened the shale was hewn by hand and the first fossil was found in 1912. Subsequently fossils were found to be numerous and incredibly well preserved. Two quarrymen in particular, Dan Scully and William Bass, worked closely with the Australian Museum and the University of Sydney, advising them of new finds. In appreciation, numerous species were named after them.
Reverend Robert Thompson Wade, a local science teacher, also collected. He then spent time in England on a research scholarship to work on ‘the fossil fishes of Brookvale,’ gaining a PhD from Cambridge University. His work was published in 1935 by the British Museum of Natural History as a monograph.
Fossil finds ended when the quarry was mechanised in 1950 and it closed in 1966.
Today the Beacon Hill shale deposit is recognised internationally for its diverse fossilised ancient life which includes fish, amphibians, molluscs, crustaceans, insects and plant fragments. An amazing 28 different genera of fish were found in what is a very small area. Many of them were new to science and among the names coined for new genera were Beaconia and Brookvalia. They both apply to species of now extinct freshwater ray- finned fish.
Richard Michell is the vice-president of the Manly, Warringah and Pittwater Historical Society and the secretary of Friends of Dee Why Lagoon. Visit mwphs.org.au and fodyl.au respectively.
