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TOPIC: The 'Great Dying'


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Rare geological formation hints at cause of mass extinction 250 million years ago

Recently, a scientific discovery in Qingchuan County, Sichuan province provided a possible clue about what precipitated the largest mass extinction in the earth's history, which happened 250 million years ago, Chengdu Business Daily reported.
Zheng Quanfeng, an associate researcher at the Nanjing Institute of Geology and Paleontology under the Chinese Academy of Sciences, found the rare geological site, a 50,000-square-meter bed of rocks and fossils. The site was once a deep sea, though it developed into sedimentary stratum from the late Permian period to the early Triassic. Given its record of the mass extinction during the late Permian period, the site has extraordinary scientific value, Zheng said.

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Findings Rock Long-Held Assumptions about Ancient Mass Extinction

New evidence gathered from the Karoo Basin in South Africa sheds light on a catastrophic extinction event that occurred more than 250 million years ago and wiped out more than 90 percent of life in Earth's oceans and about 70 percent of animal species on land. The new evidence derives from a key volcanic ash deposit that the team discovered in rock layers, or strata, that were reported to chronicle the mass extinction. By dating the volcanic ash-bearing deposit, researchers concluded that two phases of this extinction - one on land, the other in the oceans - occurred at least 1 million years apart, as opposed to roughly at the same time, as the geoscience community has assumed for decades.
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Permian extinction
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Amphibians and dinosaurs were the new large predators after the mass extinction

Immediately after the biggest extinction event of all time there were once again functioning and complete food webs in the oceans of the Early Triassic. Contrary to previous assumptions there were large predators, too. Large predatory fish and amphibians, and later dinosaurs too, were the last link in the food chain. This is demonstrated in new studies by palaeontologists at the Universities of Zurich and Utah, USA.
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MIT researchers find that the end-Permian extinction happened in 60,000 years - much faster than earlier estimates.

Multiple theories have aimed to explain the cause of what's now known as the end-Permian extinction, including an asteroid impact, massive volcanic eruptions, or a cataclysmic cascade of environmental events. But pinpointing the cause of the extinction requires better measurements of how long the extinction period lasted.
Now researchers at MIT have determined that the end-Permian extinction occurred over 60,000 years, give or take 48,000 years - practically instantaneous, from a geologic perspective. The new timescale is based on more precise dating techniques, and indicates that the most severe extinction in history may have happened more than 10 times faster than scientists had previously thought.

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Permian mass extinction
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Not the end of the world: why Earth's greatest mass extinction was the making of modern mammals

The ancient closest relatives of mammals - the cynodont therapsids - not only survived the greatest mass extinction of all time, 252 million years ago, but thrived in the aftermath, according to new research published today (28th August).
The first mammals arose in the Triassic period, more than 225 million years ago. These early fur balls include small shrew-like animals such as Morganucodon from England, Megazostrodon from South Africa and Bienotherium from China.
They had differentiated teeth (incisors, canines, molars) and large brains and were probably warm-blooded and covered in fur - all characteristics that stand them apart from their reptile ancestors, and which contribute to their huge success today.

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Oddest couple share 250mil year old burrow

Scientists from South Africa, Australia and France have discovered a world first association while scanning a 250 million year old fossilised burrow from the Karoo Basin of South Africa.
The burrow revealed two unrelated vertebrate animals nestled together and fossilised after being trapped by a flash flood event. Facing harsh climatic conditions subsequent to the Permo-Triassic (P-T) mass extinction, the amphibian Broomistega and the mammal forerunner Thrinaxodon cohabited in a burrow.
Scanning shows that the amphibian, which was suffering from broken ribs, crawled into a sleeping mammals shelter for protection. This research suggests that short periods of dormancy, called aestivation, in addition to burrowing behaviour, may have been a crucial adaptation that allowed mammal ancestors to survive the P-T extinction.

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Permian Triassic Boundary

Thu, 28 Jun 07

Duration: 43 mins

Melvyn Bragg discusses the Permian-Triassic boundary in evolutionary history. With guests Richard Corfield, Mike Benton and Jane Francis.

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Permian-Triassic mass extinction
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China Deposits Point To Cause Of Earth's Deadliest Extinction

University of Cincinnati professor Thomas J. Algeo, working with a team of Chinese scientists, has established a tight link between repeated episodes of volcanic activity and environmental degradation leading up to the deadliest extinction in Earth's history.
In a paper published in the November 2012 issue of the journal Geology, Algeo and colleagues from the China University of Geosciences track patterns of carbon isotope ratios associated with volcanic ash layers preserved in southern China rock layers. In particular, the team looked at two rock successions preserving finely layered marine deposits that record volcanic activity from before the end of the Permian period (252 million years ago) through the early part of the next geologic period, the Triassic. These successions contain layers recording events during the crisis that resulted in the extinction of some 90 percent of marine species on Earth.

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Permian-Triassic boundary
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Title: Negative C-isotope excursions at the Permian-Triassic boundary linked to volcanism
Authors: Jun Shen, Thomas J Algeo, Qing Hu, Ning Zhang, Lian Zhou, Wenchen Xia, Shucheng Xie and Qinglai Feng

Two Permian-Triassic boundary (PTB) sections from south China provide insights regarding the origin of negative excursions in carbonate and organic carbon isotope records associated with the largest mass extinction in Earth history. Xiakou, a carbonate ramp section, exhibits Delta13C_carb excursions of up to -2%, and Xinmin, a deep-shelf section, exhibits Delta13C_org excursions of up to -6%. In both sections, these excursions are associated with volcanic ash layers, and excursion size scales with ash layer thickness. These relationships document the direct influence of volcanism on the Earth-surface carbon cycle during the PTB crisis.

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 10 million years to recover from mass extinction

Life was nearly wiped out 250 million years ago, with only 10 per cent of plants and animals surviving. It is currently much debated how life recovered from this cataclysm, whether quickly or slowly.
Recent evidence for a rapid bounce-back is evaluated in a new review article by Dr Zhong-Qiang Chen, from the China University of Geosciences in Wuhan, and Professor Michael Benton from the University of Bristol. They find that recovery from the crisis lasted some 10 million years, as explained today [27 May] in Nature Geoscience.

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