Hallett Cove Conservation Park

From 85,000 to around 15,000 years ago, the present Gulf St Vincent was a deep river valley to the west while the nearest site of exposed quartzite was likely near the coast, which during that time lay some 350 kilometres (220 mi) to the south.It has been suggested that a debris slope may have stretched far into the gulf, covering the local quartzite which had likely eroded out only after the present coastline was established around 6,000 years ago.[5] More recently, the Kaurna people lived on two campsites dating back 2,000 years,[4] and their middens contain shellfish remains and the otoliths (earstones) of Mulloway.The Tjilbruke Dreaming story refers to seven freshwater springs south of Adelaide and down the Fleurieu Peninsula, with one most likely one that is located near the mouth of Waterfall Creek.[6] There are commemorative plaques marking a significant point of the Dreaming track at the reserve on Keerab Way, and at the site of the first spring said to be created by Tjilbruke's tears, on the foreshore at Heron Way.[5] Professor Ralph Tate realised that South Australia had been subjected to an ice age when in 1877 he discovered the area's smoothed and striated glacial pavement.In 1893, "the largest scientific excursion ever held in the Southern Hemisphere" explored the area with Prof. Walter Howchin later demonstrating that the deposits were of Permian age and that Australia was closer to the south pole than today while part of the Gondwanan supercontinent.Alderman from the University of Adelaide wrote to the National Trust of South Australia recommending that the glacial pavements along the coastal cliff tops of Hallett Cove be preserved.The plain was part of a shallow sea that bordered an ancient stable landmass[9] to the west while to the east lay ocean as the eastern half of Australia had yet to form.The beds began to buckle, fold, uplift and block fault, creating a range of mountains called the Delamerian Highlands, possibly up to 8 kilometres (5.0 mi) in height.The Precambrian rock of Black Cliff and the wave cut platform at Hallett Cove are all that remains of the base of the mountain range in this area and clearly shows complicated folding with several small faults visible.One erratic currently eroding out at the top of Black Cliff is dated 400 Million years older than the oldest Hallett Cove rocks.Overlaying the sandstone is a considerable thickness of mottled clays with patches of sand and gravel, the sediments washed down from the slopes of the Mt Lofty Ranges from 3Ma to 1Ma when the area was a river flood plain.The Gulf St Vincent was an alluvial plain drained by an ancient river when Aboriginals first settled on the Hallett Cove clifftops and their tools have been found in the sand that lies above the calcrete.