page_title: Hallett Cove Conservation Park
section_title: Permian
hierarchical_section_title: Hallett Cove Conservation Park / Geology of the park / Permian
caption_attribution_description: English: A panorama image taken from the northern part of the park.
context_page_description: Hallett Cove Conservation Park is a protected area in the Australian state of South Australia located in the suburb of Hallett Cove on the coast of Gulf St Vincent about 22 kilometres south of the centre of the state capital of Adelaide.
  Hallett Cove is one of the best known geological sites in Australia and is known for its international significance. The area has been declared a Geological Monument by the Geological Society of Australia and placed on the South Australian Heritage Register for its educational and scientific significance.
context_section_description: The 600 Ma Precambrian rocks at Hallet cove are separated from the 270 Ma Permian deposits by an unconformity. If there were periods of deposition between the two periods, erosion has removed all trace.
  The formation of Pangaea resulted in extensive glaciation over much of Australia during the Carboniferous and Permian. It is believed that by 270 Ma Australia was part of a supercontinent called Gondwanaland. Crescent shaped cracks in the glaciated pavements at Hallett Cove show that the ice flowed N/NW towards what is now the center of Australia. The ice thus originated in the uplands of land to the south. If current theories of continental drift are correct, this land was Antarctica. The Permian record at Hallett Cove not only records the passage of glaciers but their retreat.
  Hallett Cove at this time was part of a river valley orientated with the mountain range to the NE. Ice had scoured a basin and meltwater from the retreating glacier formed a lake which deposited the sediments that can be seen today along the clifftops. Although no fossils have been found in these sediments, arthropod trails have been found in similar sediments further south.  Dropstones and erratics, rocks carried by glaciers which drop when they melt, litter the beach where the Permian sediments that once held them have long since been eroded away. Smaller ones can be found still embedded in the sediments. Most of the dropstones, some bigger than cars, originated from sites hundreds of km to the south, however, several consist of rock not found in South Australia and their origin has yet to be determined. One erratic currently eroding out at the top of Black Cliff is dated 400 Million years older than the oldest Hallett Cove rocks. Made of Tillite, it is the earliest evidence of glaciation ever recorded.
caption: Black Cliff viewed from the north
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