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Humbling hills

Arkaroola’s climate change story is etched in stone

21 December 2019

9:00 AM

21 December 2019

9:00 AM

Hidden in the spectacular rugged mountains of the far north Flinders Ranges at Arkaroola is a climate story written in stone.

What were muds, silts and sands were compressed, pushed down and became so hot that they melted 1600 million years ago. Uranium was concentrated in these melts which solidified into a radioactive granite. Further compression pushed the radioactive granite and cooked rocks up into a mountain range. A billion years later, the giant supercontinent Rodinia fragmented. Erosion flattened the mountains at Arkaroola and basalt lava spewed out from deep fractures. Stretching of the Earth led to the formation of a large basin called the Adelaide Rift Complex.

Sand, silt and mud were deposited in the shallow warm marine basin. Towards the base of this thick pile of sediments were bacterial colonies that extracted carbon dioxide from seawater to form stromatolite reefs. Dolomite is a very voluminous marine sediment in the Complex. Experiments show that dolomite can only form when the atmosphere has hundreds of times more carbon dioxide than today.

The Sturtian ice age occurred 700 million years ago. Ice covered the planet. An ice sheet at least 20 kilometres thick was at sea level at equatorial Arkaroola. This was the greatest ice age the Earth had ever experienced yet the atmosphere contained hundreds of times the current CO2 content. Using climate activist ideology, there should have been runaway global warming rather than an ice age.

Only continental glacial and deep-sea sediments formed during the Sturtian. Immediately after, the planet warmed. This was not due to human emissions of carbon dioxide. Dolomitic marine rocks on top of glacial debris confirm a sea level rise of at least 1,500 metres. Chemical fingerprints of these dolomites show that sea water was +40°C immediately after an ice age. That’s real global warming. Ice sheets contained boulders, sand, silt, mud and very fine-grained ground-up material called rock flour. Melt waters washed rock flour into the oceans providing nutrients for the bacterial life that survived the ice age. Warm times about 650 million years ago led to the emergence of animal life from nutrient-rich warm sea water. The Arkaroola Reef was a barrier reef. It contains fossils of the first multicellular life on Earth. Up until recently, it was thought that the Ediacaran fauna (580 to 542 million years old) was the first animal life on Earth. This is now wrong. Science advances by refutation.


Red rocks formed on tidal flats show that after the formation of the Arkaroola Reef, there was more oxygen in the carbon dioxide-rich atmosphere. They also show Arkaroola was still close to the equator, the moon was far closer to the Earth than now and an Earth year was 400 days long. Warm times came to a sudden end with the onset of the Marinoan glaciation 635 million years ago. It was less intense and shorter lived than the Sturtian glaciation and Earth was again a snowball. Sea level dropped, the surface of oceans froze and animals in the Arkaroola Reef became extinct. The geological record shows time and again that extinction and loss of reefs occurs during cooling and sea level fall and not due to global warming as climate activists try to tell us. The Marinoan started when atmospheric CO2 was hundreds of times the current level showing it cannot drive global warming.

Ice at Arkaroola was again at sea level at the equator and a seasonal freeze-thaw resulted in icebergs calving from glaciers. They floated out to sea, melted and dropped rocks onto the sea floor. When sea ice covered the oceans, iron dissolved from sea floor sediments back into seawater. When the sea ice broke up, currents circulated oxygenated seawater and dissolved iron precipitated onto the sea floor in a global event that formed iron ore. Debris left behind by retreating glaciers was covered by dolomitic rocks that again formed at +40°C.

Meltwaters washed nutritious rock flour into the oceans, single-celled bacteria evolved to give the second global evolution of animal life 580 million years ago. This time it stood the test of time. About 80 different sponge-like animals were present from 580 to 542 million years ago. These animals fed on sea floor bacterial mats and, in an explosion of predatory life 542 million years ago, they were dinner for organisms that used the abundant CO2 in seawater to make protective shells, skeletons and scales. Red marine muds formed as the sea rose to cover land. There was enough oxygen in the carbon dioxide-rich atmosphere to rust soils.

The Gawler Ranges was hit 580 million years ago by an asteroid 4 kms in diameter. The 90-km diameter impact crater is in a unique red volcanic rock that does not occur at Arkaroola. Melted, vapourised and shocked red volcanic debris went for a trip through space and landed back on Earth in mud hundreds of kilometres away from the impact crater. Ripple marks in the mud show that there were tsunamis travelling at 900 km/hr.

Meanwhile, underneath the Adelaide Rift Complex’s insulating sediment blanket, radioactive granite was undergoing a natural nuclear reaction and giving out heat. At Arkaroola, the older rocks were heated to 750°C and partially melted 440 million years ago to form a granite extraordinarily enriched in uranium. Arkaroola is the only place in the world where radioactive heat has melted rocks.

An inrush of water 360 million years ago into hot rocks led to massive explosions, geysers, hot springs, thermal pools and the formation of the Mount Painter gas volcano. Arkaroola is the longest-lived geothermal system in the world with hot springs active for the last 360 million years. Modern 57°C hot springs at Arkaroola are radioactive and contain algal mats and bacteria that like it hot and radioactive. These springs are a window into early life on Earth and Mars.

The area was covered by sediments of the Great Artesian Basin. Mountain glaciers dropped debris 130 million years ago into fissures. At that time Arkaroola was polar with a temperate climate and the atmosphere had a far higher CO2 content than today. There is no relationship between atmospheric CO2 and climate.

Over the last hundred million years, most of the Adelaide Rift Complex and Great Artesian Basin sediments were stripped off as the area has been rising due to the opening of the Tasman Sea. The area is still rising and has abundant earth tremors. Over the last few million years, Arkaroola has alternated between tropical and arid conditions and some hidden valleys in this arid mountainous terrain still have remnant tropical flora.

Evidence from the past is why geologists regard human-induced global warming as total nonsense. The story of the planet is far more evocative, exciting and complex than ideology demanding that a major planetary process is driven by the addition by humans of traces of the gas of life to the atmosphere.


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