AUSTRALIA’S LARGEST OPEN RANGE WILDLIFE SANCTUARY is the vision behind a 23-kilometre 1.8 metre high fence to be built in 2019 across the foot of South Australia’s Yorke Peninsula.
The project, called the Great Southern Ark: The Rewilding of Southern Yorke Peninsula — aims to bring back many native species into their former range and restore natural ecology by shutting out feral predators.
The end goal is to provide positive agricultural, biodiversity and economic benefits for the Yorke Peninsula. Endangered species such as the southern brown bandicoots and western quolls would be reintroduced to the ark area. Bringing back the quolls and brown owls aim to reduce agricultural pests such as mice and rabbits and brush-tailed bettons improve soil quality.
The state government’s Northern and Yorke Natural Resources Board is managing the predator management fence for rewilding that received high community support from residents and landowners for its benefits in biodiversity, production, economic and social benefits.
A wide consortium of groups involved in the project include WWF Australia, Zoos SA, FAUNA Research Alliance, Conservation Volunteers Australia, Yorke Peninsula Tourism, Regional Development Australia, Yorke Peninsula Council, Nature Conservation Society of SA, Greening Australia, Trees for Life, Ag Excellence Alliance, and Legatus.
SOUTH AUSTRALIA'S SIGNIFICANT MOMENTS IN PREHISTORY OF THE PLANET
The part of the Earth we now call South Australia has produced significant moments in the planet's deep history. South Australia was once part of Gondwana, the supercontinent that broke up about 180 million years ago into landmasses of today’s Africa, South America, Australia, Antarctica, Indian subcontinent and Arabian Peninsula. South Australia’s significant moments in Earth life happened before Gondwana broke up and when South Australia was at the Equator and mostly under the Adelaidean Sea. Those significant moments are the four-kilometre wide meteorite hitting at what is now Lake Acraman; the Ediacaran start of multi-cellular life on Earth, found in the Ediacaran Hills of the Flinders Range; and the Cambrian period when the first predators appeared, with their fossils found around Emu Bay on Kangaroo Island. In the Gondwana supercontinent, South Australia adjoined what is now Antarctica. The Flinders Ranges today are miniscule compared to their ancient versions shaped by the collisions of the continental plates. South Australia – and Australia – was worn down by catastrophic events such as ice ages that froze oceans, including the Adelaidean Sea covering the southern half of South Australia, including the Flinders Ranges. The Lake Acraman meteor that hit South Australia plunged into the Adelaidean Sea and, besides its global effect, the debris from the impact is all around the Flinders Ranges where the first evidence of multi-celled life on Earth, from 600-570 million years ago, was found.
The remnants of a supervolcano found in the Gawler Ranges of South Australia drawfs the Yellowstone Caldera, the largest active supervolcano today on Earth. Gawler Ranges, stoney hills to the north of Eyre Peninsula, were formed by the supervolcano nearly 1.6 billion years ago. It spread a lava field 500 kilometres in diameter and up to 300 metres thick. The total lava was as high as 500,000 cubic kilometres – enough to fill Sydney Harbour a million times over. The lava reached temperatures above 1,000 degrees Celsius and erupted from the volcano almost instantaneously. The phenomenon left the world's largest hydrothermal deposit: a spectacular ore system with huge reserves of copper, uranium, silver and gold. Olympic Dam mine area, with about nine billion tonnes of ore, and OZ Minerals’ Carrapateena project are extracting the bounty of these hugely enriched ore-forming volcanic fluids. Bornhardts – dome-shaped steep bald rock outcrops – dominate the landscape of Gawler Ranges, traditional home of Gugada Aboriginal people. The ranges were given their European name by Edward John Eyre in honour of the South Australia's second governor George Gawler in 1839. On this expedition, Eyre made the first recorded sighting of South Australia's floral emblem: the Sturt desert pea. The 100-metre-wide sloping granite Coralbignie (Houlderoo) Rocks are another of the Gawler Ranges' features on the South Australian heritage register.
The Earth’s biggest gravity warp exerts itself in an area just north of the South Australian outback town of Marla, 1,100 kilometres northwest of Adelaide. This phenomenon is an upshot of complex geological movements half a billion years in the region of what is now the junction of the South Australian, Northern Territory and Western Australian borders. For the Marla area, the effect was on the layer – called the mantle – underneath the Earth’s crust. In the Marla area, the mantle rises 30 kilometres closer to the Earth’s surface than elsewhere. The direct cause of this is the Woodroffe Thrust Fault from the north confronting the Mann Fault from the south. This combined east-west fault zone has created a subterranean mountain out of the Earth’s mantle that’s so large it actually warps the Earth's gravity field. Dr Tom Raimondo, a geoscientist and program director for environmental and geospatial science at the University of South Australia, describes the actual effect of the fault zone: “Gravitational acceleration is faster in the red areas at the core of the fault zone compared to the blue areas either side. The difference in gravity along the fault zone is so dramatic that it has been recognised as the largest continental gravity gradient anywhere in the world. So if you were to drop a rock on your foot on the journey from Adelaide to Darwin, better to do it at a fuel stop in Marla than while sightseeing at the border of South Australia and the Northern Territory — the lower gravity at Marla means the rock will be slightly lighter so it might hurt a little less”.
Douglas Mawson’s legendary expeditions to the Antarctic (1907 and 1911) were inspired by his interest in the glacial geology he found in South Australia. Mawson’s idea for going to the Antarctic was to see an existing continental icecap and to become acquainted with glaciation and its geological consequences. This interested him because, in his South Australian studies, he was “face-to-face with a great accumulation of glacial sediments of Precambrian age, the greatest thing of the kind recorded anywhere in the world”. (Mawson’s expeditions preceded knowledge of South Australia’s geological link to Antarctica as part of the Gondwana supercontinent.) Mawson came to Adelaide in 1905 as lecturer in mineralogy and petrology at the university in 1905. A pioneer in the chemical aspects of geology and geochemistry, Mawson's immediate interest in South Australia’s glacial geology led to him identifying the mineral davidite, containing titanium and uranium, from the region now known as Radium Hill. He investigated the highly mineralised Precambrian rocks of the Barrier Range, from the northern Flinders Ranges to Broken Hill. Mawson's Antarctic expeditions, especially in 1911, collected huge scientific data. Mawson returned to Adelaide University in 1919 and his main interest during the next 30 years remained the “Adelaide System” of Precambrian rocks, especially in the Flinders Ranges. He concentrated on Proterozoic stratigraphy and Precambrian glaciation, showing glacial beds extended for 1,497 km and glacial conditions existed intermittently over much of Proterozoic time.
The Acraman eroded crater, from the impact of a meteor hit about 580 million years ago, is marked by the dry Lake Acraman, 20 kilometres in diameter, in South Australia’s Gawler Ranges on Eyre Peninsula. The meteor's size has been estimated as four kilometres, having a global cataclysmic effect, with an energy release equal to 5.2 × 106 megatons of TNT, from its hit, estimated at 90 kilometres wide. A layer of ejecta (debris) from the Acraman crater is found within Ediacaran rocks of the Flinders Ranges 300 kilometres east of the crater and in drill holes from the Officer Basin to the north. The impact would have happened when these areas were under the shallow Adelaidean Sea and the ejecta settled into mud on the sea floor. The ejecta is associated with an iridium anomaly, suggesting contamination with extraterrestrial material. The nearness of the crater to the Flinders Ranges and its Ediacara early-life organisms has been noted. The effect of the Lake Acraman impact also has been linked to evidence of ice glaciers, going back hundreds of million of years, in South Australian locations such as Chambers Bluff in the far north Indulkana Range, the Tillite Gorge near Arkaroola, the northern end of Flinders Ranges and Mount Gunson north of Port Augusta. (Lake Acraman impact structure, listed on the South Australian heritage register, is named, along with the lake and a creek, after 19th Century Adelaide businessman John Acraman, also credited as father of Australian football in the South Australian colony.)
Reg Sprigg, who discovered the 570-540-million-years-old Ediacaran fossil imprints in the Flinders Ranges in 1946, set off a long fight by the Adelaide school of thought to have the Flinders species recognised for their part in the story of evolution of life on Earth, Sprigg’s argument that the fossil imprints found in Ediacaran Hills of the Flinders Ranges were from before the Cambrian geological age (540 to 490 million years ago) was rejected by the journal Nature and the 1948 International Geological Congress. It took until 2004 for the Ediacaran Period, the first new geological era in more than 100 years, to be recognised. The Ediacaran fossil find was only part of Reg Sprigg’s contribution to South Australian prehistory. Fascinated by geology from childhood, Sprigg began studying at Adelaide University in 1937 under renowned geologists and Antarctic explorers Douglas Mawson and Cecil Madigan. Sprigg was among the first to theorise about climate change. In 1948, he formed a theory – also rejected by the International Geological Congress – that sand dunes at Beachport and Robe in South Australia's south-east resulted from sea level changes and glacial melting. He was the first to propose a theory about the geological formation of Adelaide's landscape due to the Earth's crust movement (before plate tectonics was known). He discovered some of the deepest undersea canyons, south of Kangaroo Island, about the size of the American Grand Canyon. To confirm his discoveries, he took up scuba diving, and built his own boat and his own diving chamber.
Spectacular under-sea canyons, south of Kangaroo Island, are the products of South Australia's most recent ice age of much lower sea levels when the River Murray mouth was 200 kilometres further south. The erosive power of a much more turbulent Murray is seen in the spectacular underwater canyons it left. These incredible features near Kangaroo Island reach lengths of 80 kilometres and depths of more than 5,000 metres — more than twice the height of Mount Kosciusko. One of the largest of the under-sea canyons south of Kangaroo Island is named after the geologist Reg Sprigg, who discovered them with Royal Australian Navy help in 1947. Going back about two million years, a rise in sea level flooded the South Australian River Murray valley and it became an estuary that extended north of North West Bend. The evidence for this is the thick beds of oyster shells in the lower Marne Valley, at Morgan and elsewhere. The River Murray has remained an elongated oasis in South Australia with its water, fish and shellfish – plus natural shelters in the base of its cliffs. The excavation of one of these shelters in 1929 at Devin Downs (Ngautngaut), near Nildottie, by Herbet Hale and Norman Tindale of the South Australian Museum was an Australian landmark in discovering the Aboriginal past. After digging through six metres of rock-shelter deposit and layers of faunal remains, stone and bone tools, their detailed memoir remained obscure until after World War II when radiocarbon 14 dating of the charcoal and shell samples proved the site’s occupation by Aboriginal people through 5000 years.
DESERTS, LAKE EYRE, NULLABOR, FLINDERS, RIVER MURRAY BIG ANCIENT GEOLOGICAL FEATURES
The vast arid Nullarbor Plain spectacularly and suddenly meets the Southern Ocean at the Bunda Cliffs in South Australia. The plain covers 200,000 square kilometres between the Great Australian Bight and the Great Victoria Desert. It goes for 1,256 kilometres from South Australia’s Eyre Peninsula to the Western Australian goldfields. The plain is a former shallow seabed, with bryozoans, foraminifera, echinoids and red algae skeletons making up its limestones formed in five stages. The area possibly was lifted by Earth’s crust movements in Miocene (23 million to five million years ago) era. An already flat area would have been further eroded by wind and rain. With its topography of karst – soluble rocks such as limestone, dolomite and gypsum – the Southern Ocean blows through its through many subterranean caves, resulting in blowholes up to several hundred metres from the coast. It has created large caves such as the Murrawijinie in South Australia. The Nullarbor is known for extensive meteorite deposits that have been extremely well preserved in the arid climate. Nullarbor is Latin for “no trees” but the plan is covered with bluebush and mulga scrub – and wildflowers after rain.
The Blue Lake is one of four shallow volcanic crater lakes near Mount Gambier (named after the extinct volcano) on south-east South Australia’s Limestone Coast. Only two of the lakes remain; Leg of Mutton and Brown dried up over 30 to 40 years as the water table dropped. Dates for the volcano’s eruption vary from 28,000 years to 6,000 years ago – which would make it the most recent on the Australian mainland. Blue Lake’s average depth is 72 metres but a natural cave section could take its deepest point to 204 metres. Early each November, the lake's sombre blue during winter changes to an intense deep turquoise blue almost overnight. This colouring remains until late February, when it gradually changes. From late March, it returns to a distinct sombre blue. Cause of this phenomenon is still up for conjecture but likely it involves the warming of the surface layers of the lake during the summer to around 20 °C causing calcium carbonate to precipitate out of the solution and enabling microcrystallites of calcium carbonate to form. This scatters the blue wavelengths of sunlight. An obelisk beside the lake marks poet Adam Lindsay Gordon’s daring feat in 1865 when he made his famed leap on horseback over an old post and rail guard fence onto a narrow ledge overlooking the Blue Lake and jumped back again onto the roadway. The 3.6 kilometre road and walking track around the Blue Lake gives access to many viewing points, the most popular being the underpass between the Blue Lake and the Leg of Mutton Lake.
The River Murray, Australia’s longest at 2,508 kilometres, rises in the Australian Alps and eventually as it flows to the northwest into South Australia where it turns south at Morgan for its final 315 kilometres, reaching the Southern Ocean at Lake Alexandrina and the Coorong. The Murray River is part of the 3,750-km Murray-Darling system that’s the catchment for one seventh of Australia’s land mass. Between 2.5 and 0.5 million years ago, the Murray ended in the vast freshwater Lake Bungunnia, formed by earth movements blocking the river near Swan Reach in South Australia. Deep clays from the lake are revealed in cliffs around Chowilla. The lake drained away about 600,000 years ago. At 2010, the Murray system was receiving only 58% of its natural flow due to irrigation takes for crops. The river’s health has declined since being regulated by European settlement, threatening native fish such as the Murray cod, trout cod, golden/silver perch and eel-tailed catfish. Introduced fish species, especially carp, also have taken a big toll on native species and water quality. Other aquatic species like the Murray short-necked turtle, crayfish, broad-clawed yabbies and large-clawed Macrobrachium shrimp share the struggle with long-necked turtles, small clawless paratya shrimp, water rats and platypus. The Murray supports corridors and forests of river red gums put under stress by droughts on top of the Murray’s usual variable flow. Since the 2000s, dredging machines at the Murray Mouth move sand to maintain a minimal flow from the sea and into the Coorong’s lagoon system.