On the Kurnell Peninsula, about 20,000 years ago at the height of the ice age, the Kurnell headland was a sandstone hill. The old dunes formed much of what is now Botany Bay and the Kurnell headland. Between 18,000 and 10,000 years ago, as the sea level rose, seagrass, salt marsh and mangroves developed and moved inland. The first evidence of Indigenous occupation of the area appears to be about 12,000 years ago. At this time the swales of the old dunes contained swamps.
