St Michaels Cave is situated in the Sydney suburb of Avalon Beach. This sea-side cave is around 110 metres long, 15 metres high and 10 metres wide. The original colonial owner was a Reverend John Therry, who planned to deliver lectures within the cave and build a church above it. The cave was formed by the erosion of a jurassic dyke through triassic sedimentary rocks. The cave is known to be a breeding site for Common bent-wing bats and Large-eared pied bats.NSW Government Geological Series Sheet 9130 Edition 1, 1983
See also Sydney Basin Newport Formation (NSW) Bald Hill Claystone Narrabeen group
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