地球歷史上死傷最慘重的時期也是最難聞的

 原文網址：https://news.ucr.edu/articles/2021/12/20/deadliest-period-earths-history-was-also-stinkiest

微生物打嗝造成了大滅絕

By Jules Bernstein

一項新研究提出微生物打嗝產生的有毒氣體不但是地球歷史上最嚴重大滅絕事件的成因之一，也讓這段時期持續更久。

位在今日西伯利亞的火山造成了世界上最嚴重的大滅絕事件。

極端劇烈的火山活動並不是白堊紀末物種大量消失的原因

 原文網址：https://www.ub.edu/web/ub/en/menu_eines/noticies/2021/09/030.html

發表在期刊《地質》(Geology)的研究否決了在白堊紀末的物種大量滅絕事件中，極端劇烈的火山活動期具有任何一絲影響。這項結果也證實了6600萬年前一次巨大的隕石撞擊對生物造成了重大危機，最終消滅了非鳥類恐龍的血脈以及其他陸上與海中生物的假說。

蘇馬亞海岸的岩壁保存了相當完整的地層段落，從中可以得出地球1億1500萬年到5000萬年前的地質歷史

古代全球大滅絕事件發生的同時氧氣含量也出現高峰

 原文網址：https://news.fsu.edu/news/science-technology/2021/08/02/fsu-researchers-find-oxygen-spike-coincided-with-ancient-global-extinction/

By Bill Wellock

二億五千萬年前，地球上的大多數生物都滅亡了。

經過純化的岩石樣品會在國家強磁場實驗室中測量它們的鉈同位素。圖片來源：Stephen Bilenky/ National High Magnetic Field Laboratory

大型火山爆發造成了最嚴重的大滅絕

 原文網址：https://www.tohoku.ac.jp/en/press/volcanic_eruption_caused_largest_mass_extinction.html

大型火山爆發造成了最嚴重的大滅絕

日本、美國和中國的研究人員表示他們找到了更加確定的證據，顯示史上最嚴重的生物大滅絕是由火山造成。這項研究探討了兩次分開的噴發事件：其中一個對研究人員來說是從未聽聞的，另一個則造成了海洋和陸地許多地方的生物走向滅絕。

圖一. 團隊發現中國南部和義大利在2億5200萬年前形成的沉積岩中有高濃度的蒄―汞。成對的蒄―汞是形成大型火成岩區域的火山多次活動的產物。他們表示這些活動造成的環境變遷可能使得許多陸地和海洋的動物消失。來源：海保邦夫

科學家證實了地球歷史上規模最大的滅絕事件的元凶

 原文網址：https://www.geomar.de/en/news/article/ausloeser-fuer-groesstes-massenaussterben-der-erdgeschichte-identifiziert

科學家證實了地球歷史上規模最大的滅絕事件的元凶

最新研究完整重建了二疊紀和三疊紀之際的事件

2.52億年前，在二疊紀進入到三疊紀之際，當時地球上生存的大多數生命形式就此滅亡。最近德國基爾亥姆霍茲海洋研究中心(GEOMAR)、德國地質科學研究中心(GFZ)和不同國家的科學家互相合作，利用最新的分析技術並用電腦模型詳細的計算結果，首次明確地重建出是什麼樣的地球化學過程，造成了這次前所未見的生物危機。研究今日發表在期刊《自然―地球科學》(Nature Geoscience)。

這幅示意圖根據Jurikova等人在2020年的發現，描繪了二疊紀―三疊紀大滅絕開始時的狀況。畫家為羅馬大學PaleoFactory的Dawid Adam Iurino 。

地球最嚴重的大滅絕事件中，陸地生物開始相繼死亡的時間遠比海洋生物的更迭還早發生

原文網址：https://news.berkeley.edu/2020/03/25/in-earths-largest-extinction-land-die-offs-began-long-before-ocean-turnover/

地球最嚴重的大滅絕事件中，陸地生物開始相繼死亡的時間遠比海洋生物的更迭還早發生

By Robert Sanders

2億5200萬年前二疊紀結束時的大滅絕事件，是生物改朝換代的事件最劇烈的其中之一。最近重新定年南非和澳洲的化石地層之後，顯示這起事件的發生時間與過程在陸地和海洋有明顯的差異。

研究人員定年這座山丘(南非語稱作koppie)裡的火山灰沉積物。Loskop山丘的下部露出的地層為二疊紀末大滅絕事件前行成的(巴爾福層的Palingkloof段)，而上部的岩層則是在滅絕事件後沉積的(卡特堡層)。圖片來源：John Geissman

對二疊紀晚期主要的動物相消失不久之後便出現的脊椎動物重新定年之後，顯示出陸地生態系的變化比海洋還早數十萬年發生，最後導致將近70%的陸生脊椎動物死亡。稍後才發生的海洋滅絕事件則可能歷經了數萬年，造成幾乎95%的海洋生物消失。

雖然大多數科學家認為二疊紀結束時的大滅絕事件，主要原因是現為西伯利亞的區域在數百萬年當中接連發生大型火山爆發事件。但是南半球的陸地生物和北半球的海洋生物是在不同的時間滅亡，顯示出兩者的直接原因並不相同。

「大部分的人都以為陸地和海洋生態系是在同一時間崩潰，而且南北半球的發生時間也一樣。」加州大學柏克萊分校整合生物學系的副教授，古植物學家Cindy Looy表示。「南北半球並非同時發生巨變的這項事實，對於滅絕原因的假說具有重大影響。海洋生物的滅絕事件本身並沒有非得要和陸地生物的滅絕事件有同樣的機制或成因。」

滅絕事件是由臭氧層變薄導致？

Looy實驗室的成員之前以現生植物來進行實驗，探討保護地球的臭氧層大幅減薄是否會使植物暴露於輻射之下而滅絕。其他二疊紀結束至三疊紀開始之際全球發生的變化，像是氣候暖化、大氣裡的二氧化碳濃度上升、海洋酸化……等，也是可能的原因。

在陸上，最詳實紀錄二疊紀末脊椎動物滅絕的地點為盤古超大陸的南半部——岡瓦那大陸，我們現在所知的南極洲、澳洲、南美洲、澳洲都是由它分裂而成。南非的卡魯盆地位在岡瓦那大陸，此處顯示出當時大型草食動物族群的化石組合從二齒獸轉變成水龍獸(這些動物都已經滅絕)。

在海裡，最詳實記錄滅絕事件的地點位在北半球，尤其是中國的化石。或許最能代表二疊紀末滅絕事件的指標即為三葉蟲的全數消失。

為了更加精確地定出陸上滅絕事件發生的時間點，Looy參與的國際科學團隊從卡魯盆地保存良好的火山灰堆積物中取出鋯石晶體，然後用鈾鉛定年法得出它們的年代。Looy同時也是加州大學柏克萊分校古生物博物館的古植物研究員，以及該校大學與Jepson標本館的裸子植物研究員。她確認了用來定年的地層上方數公尺的沉積物中缺少了舌羊齒的花粉，證明二疊紀末岡瓦那大陸最主要的植物——種子蕨，在當時就已經滅絕了。

鋯石是一種微小的矽酸鹽類晶體，形成於火山內部上湧的岩漿當中，並隨著火山爆發而噴到大氣裡頭。他們的定年結果顯示這些鋯石的年代為2億5224萬年，比位於中國公認的二疊紀—三疊紀邊界的年代還早了三十萬年。代表南非這處被認為擁有二疊紀—三疊紀邊界的沉積岩，至少比公認的邊界還要早三十萬年形成。

內布拉斯加大學林肯分校的Christopher Fielding和同僚一月發表的研究中，他們在澳洲記錄植物開始滅絕的岩層上方不遠處採集了火山灰堆積物，經過定年之後也得到了類似的年代，比公認的還要早了將近四十萬年。

「卡魯盆地是二疊紀末脊椎動物更迭過程的代表地點，但一直以來都沒有對它進行良好的定年。」Looy表示。「我們最新的鋯石定年結果顯示水獸龍化石帶的下界比海洋滅絕事件還早了數十萬年，而澳洲的研究也得出了類似的模式。這代表岡瓦那大陸動植物的更迭和北半球海洋生物經歷的危機是不同步的。」

「我們這些年來已經知道跟發生在海裡的大滅絕事件不同，陸地生物一直到三疊紀開始很久之後還是有出現幾波劇烈的變動。但令人驚訝的是，陸地生物演替的開始時間竟然比海洋的滅絕事件還要提早許多。」

Looy和國際科學團隊在論文最後總結：「我們應該更加深入地探討長興期(二疊紀最後一個時期)，甚至是三疊紀早期陸地生態系發生了哪些漸進、複雜且細微的轉變。」

Looy和同僚的研究成果3月19日發表在開放取用期刊《自然通訊》(Nature Communications)。共同作者包括美國緬因州科爾比學院的Robert Gastaldo、加拿大安大略省多倫多大學的Sandra Kamo、南非普利托利亞地球科學理事會的Johann Neveling、美國德州大學達拉斯分校的John Geissman、美國麻州安默斯特學院的Anna Martini。研究經費來自美國國家科學基金會。

In Earth’s largest extinction, land die-offs began long before ocean turnover

The mass extinction at the end of the Permian Period 252 million years ago — one of the great turnovers of life on Earth — appears to have played out differently and at different times on land and in the sea, according to newly redated fossils beds from South Africa and Australia.

New ages for fossilized vertebrates that lived just after the demise of the fauna that dominated the late Permian show that the ecosystem changes began hundreds of thousands of years earlier on land than in the sea, eventually resulting in the demise of up to 70% of terrestrial vertebrate species. The later marine extinction, in which nearly 95% of ocean species disappeared, may have occurred over the time span of tens of thousands of years.

Though most scientists believe that a series of volcanic eruptions, occurring in large pulses over a period of a million years in what is now Siberia, were the primary cause of the end-Permian extinction, the lag between the land extinction in the Southern Hemisphere and the marine extinction in the Northern Hemisphere suggests different immediate causes.

“Most people thought that the terrestrial collapse started at the same time as the marine collapse, and that it happened at the same time in the Southern Hemisphere and in the Northern Hemisphere,” said paleobotanist Cindy Looy, University of California, Berkeley, associate professor of integrative biology. “The fact that the big changes were not synchronous in the Northern and Southern hemispheres has a big effect on hypotheses for what caused the extinction. An extinction in the ocean does not, per se, have to have the same cause or mechanism as an extinction that happened on land.”

Did loss of ozone layer contribute to extinction?

Members of Looy’s lab have conducted experiments on living plants to determine whether a collapse of Earth’s protective ozone layer may have irradiated and wiped out plant species. Other global changes — a warming climate, a rise in carbon dioxide in the atmosphere and an increase in ocean acidification — also occurred around the end of the Permian period and the beginning of the Triassic and likely contributed.

On land, the end-Permian extinction of vertebrates is best documented in Gondwana, the southern half of the supercontinent known as Pangea that eventually separated into the continents we know today as Antarctica, Africa, South America and Australia. There, in the South African Karoo Basin, populations of large herbivores, or plant eaters, shifted from the Daptocephalus assemblage to the Lystrosaurus assemblage. These groups are now extinct.

In the ocean, the extinction is best documented in the Northern Hemisphere, in particular by Chinese fossils. The end-Permian extinction is perhaps best associated with the demise of trilobites.

To improve on previous dates for the land extinction, an international team of scientists, including Looy, conducted uranium-lead dating of zircon crystals in a well-preserved volcanic ash deposit from the Karoo Basin. Looy, who is also a curator of paleobotany at the campus’s Museum of Paleontology and curator of gymnosperms at the University and Jepson Herbaria, confirmed that sediments from several meters above the dated layer were devoid of Glossopteris pollen, evidence that these seed ferns, which used to dominate late Permian Gondwanan floras, became extinct around that time.

At 252.24 million years old, the zircons — microscopic silicate crystals that form in rising magma inside volcanoes and are spewed into the atmosphere during eruptions — are 300,000 years older than dates obtained for the confirmed Permian-Triassic (P-T) boundary in China. This means that the sediment layer assumed to contain the P-T boundary in South Africa was actually at least 300,000 years too old.

Dates for an ash deposit in Australia, just above the layers that document the initial plant extinction, similarly came in almost 400,000 years older than thought. That work was published in January by Christopher Fielding and colleagues at the University of Nebraska in Lincoln.

“The Karoo Basin is the poster child for the end-Permian vertebrate turnover, but until recently, it was not well-dated,” Looy said. “Our new zircon date shows that the base of the Lystrosaurus zone predates the marine extinction with several hundred thousand years, similar to the pattern in Australia. This means that both the floral and faunal turnover in Gondwana is out of sync with the Northern Hemisphere marine biotic crisis.

“For some years now, we have known that — in contrast to the marine mass extinction — the pulses of disturbance of life on land continued deep into the Triassic Period. But that the start of the terrestrial turnover happened so long before the marine extinction was a surprise.”

In their paper, Looy and an international team of colleagues concluded “that greater consideration should be given to a more gradual, complex, and nuanced transition of terrestrial ecosystems during the Changhsingian (the last part of the Permian) and, possibly, the early Triassic.”

Looy and colleagues published their findings March 19 in the open access journal Nature Communications. Her co-authors are Robert Gastaldo of Colby College in Maine; Sandra Kamo of the University of Toronto in Ontario; Johann Neveling of the Council for Geosciences in Pretoria, South Africa; John Geissman of the University of Texas in Dallas and Anna Martini of Amherst College in Massachusetts. The research was funded by the National Science Foundation.

原始論文：Robert A. Gastaldo, Sandra L. Kamo, Johann Neveling, John W. Geissman, Cindy V. Looy, Anna M. Martini. The base of the Lystrosaurus Assemblage Zone, Karoo Basin, predates the end-Permian marine extinction. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-15243-7

引用自：University of California - Berkeley. "In Earth's largest extinction, land animal die-offs began long before marine extinction: New dates for fossils indicate land animal turnover extended for hundreds of thousands of years." 

新的證據顯示史上最嚴重的大滅絕是由火山造成

原文網址：https://www.uc.edu/news/articles/2019/04/n2081561.html

新的證據顯示史上最嚴重的大滅絕是由火山造成

在全球古代岩石中找到的汞，支持了2億5200萬年前的「大死亡」是由火山爆發造成的理論

研究人員表示埋藏在古代岩石中的汞是迄今最為強力的證據，顯示地球歷史上最嚴重的大滅絕是由火山造成。

全球暖化讓海洋動物難以呼吸，造成地球歷史上最慘重的滅絕事件

原文網址：http://www.washington.edu/news/2018/12/06/biggest-extinction-in-earths-history-caused-by-global-warming-leaving-ocean-animals-gasping-for-breath/

全球暖化讓海洋動物難以呼吸，造成地球歷史上最慘重的滅絕事件

Hannah Hickey

遠在恐龍出現之前，當時大部分居住在地球的動植物都在西伯利亞發生的一連串大規模火山爆發中消失了。這起地球歷史上最大的滅絕事件發生在2億5200萬年前左右，其標記了二疊紀的結束。

這塊來自於中國南部，大約1.5呎(約45 cm)厚的石板顯示出二疊紀―三疊紀的交界。下段是在滅絕之前形成的石灰岩，上段則是滅絕之後由細菌沉積成的石灰岩。圖片來源：Jonathan Payne/Stanford University

大滅絕之前的預警

原文網址：https://www.fau.eu/2018/03/14/news/research/mass-extinction-with-prior-warning/

大滅絕之前的預警

跟過往推測的相反，大滅絕之前確實會有警訊出現

在地球歷史上曾發生過的大滅絕事件都有被確實記錄下來，科學家相信它們的發生歷程從地質角度來看不過是短短一下子。但在一篇新發表的研究中，愛爾朗根―紐倫堡大學的古生物學家和他們合作的研究人員顯示，地球歷史上最劇烈的大滅絕事件逐漸變得清晰的時間比過往認為的還要早了許多，並指出相同的跡象也可以在今日觀察到。

在大滅絕造成浩劫之後生物仍持續使海洋生態系運作

原文網址：http://www.leeds.ac.uk/news/article/4121/life_goes_on_for_marine_ecosystems_after_cataclysmic_mass_extinction

在大滅絕造成浩劫之後生物仍持續使海洋生態系運作

科學家發現史上最重大的全球滅絕事件之一並未從基礎層面改變整個海洋生態系。

包括里茲大學的Alex Dunhill博士的國際科學家團隊，發現二疊紀末的大滅絕雖然殲滅了絕大部分的物種，但海洋生態系的運作方式似乎沒有太過劇烈的改變。

主要作者，里茲大學地球和環境學院的Dunhill博士表示：「雖然三疊紀末的大滅絕事件對海洋物種的整體數目有重大影響，但是倖存物種的多樣性仍足以讓海洋生態系的運作方式維持得跟之前一樣。」

「我們並非指說一切安好。」共同作者，德州大學奧斯汀分校地質科學院的古生物學家William Foster表示。「而是滅絕事件過後的全球海洋變得有點像是由骷顱船員掌舵的幽靈船――雖然所有的崗位都在運作，但是僅由少數物種來操縱。」

三疊紀末期的大滅絕事件發生在2億100萬年前。當時火山活動造成大氣的溫室氣體濃度飆升，導致相當迅速的全球暖化，地球將近50%的生物因而死亡。這場火山爆發事件也和盤古超大陸的分裂以及大西洋的形成有關。

團隊檢視了從三疊紀中期至侏儸紀中期7000萬年間的化石紀錄，以比較三疊紀末期滅絕事件發生前後海洋生態系的改變。他們將居住在海洋的動物依據其移動方式、棲息場所和飲食習慣來分類出不同的生活類型。

接著他們確定沒有一種生活類型因為滅絕事件而完全消失，代表海洋生態系完整地保存下來。

他們今日發表在《古生物學》(Palaeontology)的結果顯示雖然滅絕事件並未顛覆全球海洋生態，但它對個別區域和環境卻有深遠的影響，並對特定類型的海洋生態系造成重大衝擊。

Dunhill博士表示：「三疊紀末期死傷最慘重的海洋生物之一便是固定不動，居住在礁體的生物，像是珊瑚。當我們檢視化石紀錄，我們看到雖然海洋生態系整體來說仍然持續運作著，但熱帶珊瑚礁生態系卻耗費超過2000萬年的時間，才從這場環境浩劫中回復過來。」

「礁體生態系對迅速發生的環境變遷最為敏感。三疊紀末期溫室氣體對海洋生態系造成的影響，跟今日我們見到因為海洋溫度升高而死亡的珊瑚礁所經歷的情況並沒有多大差異。」

共同作者，倫敦自然史博物館的Richard Twitchett表示：「瞭解過去大滅絕事件中珊瑚礁的崩毀程度，或許有助於我們預測現在海洋生態系將會遭遇的情況。」

「過去每當溫室氣體迅速增加時，熱帶生態系就會有大範圍地區受到摧殘，儘管各次事件的溫室氣體變化速率和罹難物種不盡相同。雖然(造成二氧化碳增加的)起因有所差異，當看見過往事件一再造成類似的後果，便可以推論類似情形在未來也可能會再度重演。」

Life goes on for marine ecosystems after cataclysmic mass extinction

One of the largest global mass extinctions did not fundamentally change marine ecosystems, scientists have found.

An international team of scientists, including Dr Alex Dunhill from the University of Leeds, has found that although the mass extinction in the Late Triassic period wiped out the vast proportion of species, there appears to have been no drastic changes to the way marine ecosystems functioned.

Lead author Dr Dunhill, from the School of Earth and Environment, said: “While the Late Triassic mass extinction had a big impact on the overall number of marine species, there was still enough diversity among the remaining species that the marine ecosystem was able to function in the same way it had before.”

“We’re not saying nothing happened,” said co-author Dr William Foster, a palaeontologist from the Jackson School of Geosciences at the University of Texas at Austin. “Rather, global oceans in the extinction’s aftermath were a bit like a ship manned by a skeleton crew – all stations were operational, but manned by relatively few species.”

The Late Triassic mass extinction occurred 201 million years ago. Nearly 50 per cent of life on Earth died out as a result of huge volcanic eruptions. The volcanic activity created high levels of greenhouse gases in the atmosphere which led to rapid global warming. The eruptions are also associated with the break-up of the super-continent Pangaea and the opening of the Atlantic Ocean.

The team compared marine ecosystems across the late Triassic mass extinction event by examining fossils from the Middle Triassic to Middle Jurassic —a 70 million-year span. They classified the lifestyle of different ocean-dwelling animals by how they moved, where they lived and how they fed.

They were then able to determine that none of these lifestyles had completely disappeared due to the extinction event, which preserved the marine ecosystem.

Their results, published today in Palaeontology, showed that while the extinction did not result in a global marine ecological shift, it had profound regional and environmental effects and had an extreme impact on specific ocean ecosystems.

Dr Dunhill said: “One of the great marine casualties of the Late Triassic were stationary reef-dwelling animals, such as corals. When we examined the fossil record we saw that while the marine ecosystem continued to function as a whole, it took over 20 million years for tropical reef ecosystems to recover from this environmental cataclysm.

“Reef ecosystems are the most vulnerable to rapid environmental change. The effect of the Late Triassic greenhouse gases on marine ecosystems is not so different from what you see happening to coral reefs suffering from increasing ocean temperatures today.”

Co-author, Professor Richard Twitchett, from the Natural History Museum in London said: “Understanding the extent of reef collapse during past extinctions may help us predict what is in store for our modern marine ecosystems.

“Tropical ecosystems suffered widespread devastation each time that greenhouse gases rose rapidly in the past, despite differences in the rates of change and species involved. When you see similar responses occurring time and time again in the past, despite different starting conditions, it follows that similar responses will likely occur again in the future.”

原始論文：Dunhill, A; Foster, W; Sciberras, J; Twitchett, R. Impact of the Late Triassic mass extinction on functional diversity and composition of marine ecosystems. Palaeontology, 2017 DOI: 10.1111/pala/12332

引用自：University of Leeds. "Life goes on for marine ecosystems after cataclysmic mass extinction."