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Causes and Events of Capitanian Extinction

The Capitanian age is period of mass extinction as it exhibits 3 necessary qualities:

1. it was global
2. it happen over a short period of time and
3. it affected many species

Global impact

The Capitanian extinction, initially thought to be an extinction event only based in South China, is now recognized as a global event. Two or more extinctions are known to have occurred within the Capitanian. This includes an initial major extinction, a recovery period and followed by other smaller extinctions prior to and linked with the End-Permian mass extinction. It is now known to be based not only in South China and parts of the US but also Japan, Western Tethys (present day Hungary and Hydra, Greece), Spitsbergen (Norway), East Greenland and Canada. Each location has several different causes for extinction. These different causes include regression, volcanism, anoxia, acidification, δ¹³C cooling and methane outburst.

South and North China (Emeishan Traps)

Volcanism is considered a major causes of the Capitanian extinction. In South China the Emishan Large Igneous Province (LIP), as a result of the volcanic eruptions caused the Flood Basalt Povince (FBP). The extinction occurred in the end of the conodont zone J. Altudaensis. The volcanic eruption released large amounts of CO₂ which lead to ocean acidification, various poisonous gases including trace metals such as mercury and caused cooling due to volcanic gases. Some workers feels that the Traps should not have caused cooling but rather global warming. Recent dating however places the Emeishan Traps between 256-259 mya (Lopingian Age) which falls after the Capitanian extinction. Other state that there is in fact a link between the Emeishan Traps and the End-Guadalupian extinction which occurred at the border of G-L. Due to the volcanism shallow water organisms such as foraminifera, corals, brachiopods, invertebrates and calcerous algae died significantly. In addition many terrestrial plant species, 56% in North China and 24% in South China were wiped out due to the Emeishan volcanism. The extinction of floral species in North China was more significant than in South China even though South China was in closer proximity to the volcano.

Modern Day Comparison

A good example of the effects of a volcanic emission is the Laki Fissure (1783-84) in Iceland. It affected 50% of livestock and stunted plant growth due to soil acidification. It caused cooling, acid rain and cessation of photosynthesis. Laki Fissure was much smaller in scale (18-20 Km³) compared to the Emeishan traps (~0.5 M Km³). A small volcano like Laki Fissure in Iceland caused massive destruction of life and the large scale Emeishan traps would have caused extensive global loss of flora and fauna.

Japan (Isozaki Kamura Cooling Event)

The Kamura cooling event is considered to be another cause of the Capitanian extinction. In a mid-Panthalassan paleo-atoll limestone, in modern day Kamura in Kyushu, Japan, high levels of δ¹³C were found. But the exact reason for the high levels of δ¹³C is unknown. This presence of this isotope indicates cooling. The levels of δ¹³C ranged from + 4.5% to a maximum of + 7 %. In the warmer latitudes some shallow dwelling species died due to the cooling and the Kamura event caused significant loss of foraminifera and brachiopods. (Land and sea bond). The cooling killed the photosymbiosis mechanism of the warm-water adapted marine species leading to extinction. There was an overall productivity in other marine organisms due to the increase δ¹³C. The Capitanian stage lasted for 5.4 mya and the Kamura cooling occupied a major period of 3-4 mya. The Capitanian extinction event occurred in the middle of the Kamura cooling event.

Western Tethys – Modern Day Hungary and Hydra, Greece (Eustatic Regression & Hiatus Period)

The timing of the extinction in China are the same as in Western Tethys (Hungary and Greece). There was an extinction in the mid-Capitanina and a recovery in the late Capitanian. The three locations were studied: the lower Episkopi formation in Hydra (Greece), limestone formation in Mihalovits (Hungary) and Marmari Episkopi (Greece). There was a long term diversity decline in these areas, especially Brachipods and an increase in Mollusks. Eustatic sea levels were at an all-time low during the G-L boundary in the Phanerozoic eon. In Western Tethys due to eustatic changes a regression was caused and reversed over a short period of time during the Capitanian. During this hiatus there was a major extinction event and new fauna came into existence after. There is a strong link between the time of extinction loses and the marine regression in Hydra. Regression is considered the cause of heavy marine extinction because the habitat of shallow marine organisms was lost. Species such as foraminifera were lost around the top of J. Altudaensis conodont zone, which coincides with the Emeishan LIP in South China. Recent studies done in South China show that regression was after the mass extinction event, that it, happened in the J. Xuanhanensis conodont zone.

Spitsbergen, Norway and East Greenland and Canada

So far the Capitanian extinction was only considered to be an event in South China but after the Spitsbergen analysis it is agreed now that the extinction event happened in higher (boreal) latitudes. There was an 87% loss in Brachiopods species similar to the loss in South China. There was also a loss of Bryozoans and Rugose Corals. Similar evidence was found in marine fossil records in East Greenland and Sverdrup Basin, Canada.

Kapp Starostin Formation, Central Spitsbergen (Anoxia)

3YLB (Yellow Limestone Bed) levels, rich in Brachiopods and bivalves, was studied at the Kapp Starostin Formation in Central Spitsbergen, Norway. At the end of that level there was an extinction in which 87% of the Brachiopods and 50% of the bivalves disappeared within a 30 cm section. After the extinction at the end of the 3YLB there was a recovery period, where a few Brachiopods and many bivalves, Bryozoans and Rugose corals reappeared. There was an increased production of Mollusks. After this there was another extinction where most of these species were lost. In addition, during this second extinction, which lasted for only ~10 m of strata, there was no limestone but Black Shale and fossils of sponges survived. This loss of limestone indicates a loss in calcareous species. These extinctions happened due to anoxia or low oxygen in the sea floor. But it may not be the only reason for the large extinctions that took place.

East Greenland, Southern Spitsbergen and Sverdrup Basin, Canada (Acidification)

There is no evidence of anoxia or regression in Southern Spitsbergen. In Wegener Halvø Formation in East Greenland, Southern Spitsbergen and Sverdrup Basin, Canada there are no carbonates above the 3YLB in those latitudes. This could be due to ocean acidification in higher altitudes, since CO₂ dissolves better in cooler waters.

Understanding Zones and δ¹³C Impact

Conodont Zone

Conodont was a small marine invertebrate organism, with over a thousand species, that was abundant during the Paleozoic era and became extinct by the end of the Triassic period. Its size ranged from 2mm to 6mm and had various shapes including teeth like cones and blade. Due to their evolution in shape and size over geological time and due to their abundance in rock layers, they are used to set the different time zones in the evolution of the earth called Conodont Zones.

δ¹³C

δ¹³C is an isotope of the element carbon. When there are high amount of it in the atmosphere it causes cooling and increased productivity in certain species of marine animals. It also leads to loss of shallow water habitat for warm water marine animals leading to their extinction. When there are low amounts of it, the weather becomes hotter and oceans experience acidification.

External Links

• New mass extinction event identified by geologists