Primeval 12 – Permian Period

 

The climate in the Permian Period was quite varied. At the start of the Permian, the Earth was still in an Ice Age, which began in the late Carboniferous Period. Glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continent’s interiors. In the late Permian period, the drying continued although the temperature fluctuated between warm and cool cycles. The Permian period lasted from 299 to 252 million years ago, and was the last period of the Paleozoic Era, to be followed by the Triassic Period of the Mesozoic Era.

Earth 260 Million Years Ago

Earth 260 Million Years Ago

The Permian Period began with the Carboniferous plants still flourishing. Around the middle of the Permian a major transition in vegetation began. The swamp-loving lycopod trees of the Carboniferous, such as Lepidodendron and Sigillaria, were progressively replaced in the continental interior by the more advanced seed ferns and early conifers. At the close of the Permian, lycopod and equicete swamps reminiscent of Carboniferous flora were relegated to a series of equatorial islands in the Paleotethys Sea that later would become South China.(1)Ren Xu and Xiuqin Wang (1982) 地质时期中国各主要地区植物 景观 (Reconstructions of Landscapes in Principal Regions of China). 地质时期中国各主要地区植物 景观 / 徐仁编著 ; 王秀琴绘

The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs. The world at the time was dominated by a single supercontinent known as Pangaea, surrounded by a global ocean called Panthalassa. The extensive rainforests of the Carboniferous disappeared, first transitioning to fern and conifer forests, and then leaving behind vast regions of arid desert within the continental interior.(2)Sarda Sahney et al. (2010) “Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica” Geology Volume 38 Number 12 Pages 1079–1082 Amniotes, who could better cope with these drier conditions, rose to dominance in lieu of their amphibian cousins. Reptiles grew to dominance, because their special adaptations enabled them to flourish in the drier climate.(3)Adam K. Huttenlocker and Elizabeth Rega (2012) “The Paleobiology and Bone Microstructure of Pelycosaurian-grade Synapsids.” in Anusuya Chinsamy-Turan, Editor Forerunners of Mammals: Radiation, Histology, Biology. Pages 90–119. Indiana University Press

Niassodon Mfumukasi in Late Permian Forest

Niassodon Mfumukasi in Late Permian Forest

The Permian ended with the most extensive extinction event recorded in paleontology: the Permian-Triassic extinction event also called the Great Dying. Up to 96% of marine species became extinct,(4)Michael Benton (2005) When life nearly died: the greatest mass extinction of all time as well as least 70% of all land organisms.(5)Sarda Sahney and Michael Benton (2008) “Recovery from the most profound mass extinction of all time.” Proceedings of the Royal Society B, Volume 275, Number 1636, Pages 759–765 It was also the only known mass extinction of insects, which is unusual as insects tend to survive environmental changes.(6)Douglas H. Erwin (July 1996) “The Mother of Mass Extinctions” Scientific American, Pages 72-78 Trilobites, which had thrived since Cambrian times became extinct before the end of the Permian. Approximately 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event, estimated at more than 100 million years.(7)Edward Osborne Wilson (1992) The Diversity of Life, Page 31

The cause of this mass extinction is unclear. One theory is that there was a massive significant flood of basalt eruptions of magma output lasting thousands of years in what is now the Siberian Traps. This would have contributed to environmental stress, and based on the amount of lava estimated to have been produced during this period, the worst-case scenario is an expulsion of enough carbon-dioxide from the eruptions to raise world temperatures five degrees Celsius. This is not enough to explain even a small extinction event, let alone the world’s biggest, and could not have caused an extinction event of plants that thrived in the carbon-dioxide rich atmosphere and the warmer temperatures of earlier periods. Another theory is that there was a massive meteor impact, however levels of iridium and quartz fracturing in the Permian-Triassic layer do not approach those of the Cretaceous–Paleogene boundary layer, casting doubt on the idea. Further doubt has been cast on this theory based on fossils in Greenland showing the extinction to have been gradual, lasting about 60,000 years,(8)Becky Oskin (Feb 11, 2014) “Worst Mass Extinction Ever Took Only 60,000 Years.” Scientific American with three distinct phases.(9)Shu-zhong Shen et al. (2011) “Calibrating the End-Permian Mass Extinction” Science, Volume 334, Number 6061, Pages 1367-1372

Lystrosaurus Herd in Late Permian Forest

Lystrosaurus Herd in Late Permian Forest

Evidence for widespread ocean anoxia, a severe deficiency of oxygen, and euxinia, the presence of hydrogen sulfide, is found from the Late Permian to the Early Triassic Periods. Throughout most of the Tethys and Panthalassic Oceans, evidence for anoxia, including small pyrite framboids, high uranium/thorium ratios, and biomarkers for green sulphur bacteria, appear at the extinction event.(10)Paul B. Wignall and Richard J. Twitchett (2002) “Extent, duration, and nature of the Permian-Triassic superanoxic event” Geological Society of America Special Papers, Volume 356, Pages 395–413 However, in some sites, including Meishan in China,(11)Changqun Caoet al. (2009) “Biogeochemical evidence for euxinic oceans and ecological disturbance presaging the end-Permian mass extinction event.” Earth and Planetary Science Letters, Volume 281, Pages 188–201 and eastern Greenland,(12)Lindsay Hays et al. (2012) “Biomarker and isotopic trends in a Permian–Triassic sedimentary section at Kap Stosch, Greenland.” Organic Geochemistry, Volume 43, Number 67–82 evidence for anoxia precedes the extinction.

This spread of toxic, oxygen-depleted water would have been devastating for marine life, producing widespread extinction. Models of ocean chemistry show that anoxia and euxinia would have been closely associated with high levels of carbon-dioxide.(13)Katja Meyers (September 2008) “Biogeochemical controls on photic-zone euxinia during the end-Permian mass extinction”. Geology, Volume 36, Number 9, Pages 747–750 This suggests that poisoning from hydrogen sulfide, anoxia, and hypercapnia, which is too much carbon-dioxide in the blood, acted together as a killing mechanism. The persistence of anoxia through the Early Triassic may explain the slow recovery of marine life after the extinction. Models also show that anoxic events can cause catastrophic hydrogen sulfide emissions into the atmosphere. This would poison terrestrial plants and animals, as well as severely weaken the ozone layer, exposing much of the life that remained to fatal levels of UV radiation.(14)Lee Kump et al. (2005) “Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia.” Geology, Volume 33, Pages 397–400

Sail-backed Dimetrodons.

Sail-backed Dimetrodons.

Nevertheless the cause of this mass extinction is unclear. The evidence for the collapse of the oceanic ecosystem followed by the toxification of the atmosphere does seem clear enough, however, what caused the oceanic collapse is unknown. The situation is currently being repeated on the Earth today, where the oceans are being over-fished and nitrogen-rich fertilizer run-off is running into the oceans from our rivers causing anoxic dead-zones where fish cannot survive. Currently the dead-zones are worst along the Atlantic Seaboard and Gulf Coast of North America, the Baltic and North Seas in Northern Europe, and the Korea Strait in Eastern Asia. Current policies geared to increasing ethanol in the United States will drastically increase the dead-zone in the Gulf of Mexico by 2022.(15)Carol Potera (June 2008) “Corn Ethanol Goal Revives Dead Zone Concerns.” Environmental Health Prospectives. The rapid rise of dead-zones is perhaps the greatest threat to humanity’s survival today. In March 2004, when the UN Environment Programme published its first Global Environment Outlook Year Book (GEO Year Book 2003), it reported 146 dead zones in the world’s oceans where marine life could not be supported due to depleted oxygen levels. Some of these were as small as a square kilometre (0.4 mi²), but the largest dead zone covered 70,000 square kilometres (27,000 mi²). By 2008 the number had climbed to 405 dead zones worldwide.(16)Robert J. Diaz and Rutger Rosenberg (2008) “Spreading Dead Zones and Consequences for Marine Ecosystems” Science, Volume 321, Number 5891, Pages 926–929

It is possible to reverse these dead-zones. The Black Sea dead zone, previously the largest in the world, largely disappeared between 1991 and 2001 after fertilizers became too costly to use following the collapse of the Soviet Union and the demise of centrally planned economies in Eastern and Central Europe. Subsequently fishing has again become a major economic activity in the region.(17)Laurence Mee (November 2006) “Reviving Dead Zones” Scientific American Between 1985 and 2000, the North Sea dead zone had nitrogen reduced by 37% when policy efforts by countries on the Rhine River reduced sewage and industrial emissions of nitrogen into the water. Other cleanups have taken place along the Hudson River(18)John Nielsen (2008-08-15) “‘Dead Zones’ Multiplying In World’s Oceans.” Morning Edition, NPR News. and San Francisco Bay.(19)David Perlman (July 15, 2008) “Scientists alarmed by ocean dead-zone growth” San Francisco Chronicle Perhaps an alien agricultural colony was responsible for the Permian-Triassic extinction event. If the aliens only expected the Solar System to be in the vicinity of their star system for 60,000 years, it wouldn’t have mattered if the native ecosystem collapsed.

References   [ + ]

1. Ren Xu and Xiuqin Wang (1982) 地质时期中国各主要地区植物 景观 (Reconstructions of Landscapes in Principal Regions of China). 地质时期中国各主要地区植物 景观 / 徐仁编著 ; 王秀琴绘
2. Sarda Sahney et al. (2010) “Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica” Geology Volume 38 Number 12 Pages 1079–1082
3. Adam K. Huttenlocker and Elizabeth Rega (2012) “The Paleobiology and Bone Microstructure of Pelycosaurian-grade Synapsids.” in Anusuya Chinsamy-Turan, Editor Forerunners of Mammals: Radiation, Histology, Biology. Pages 90–119. Indiana University Press
4. Michael Benton (2005) When life nearly died: the greatest mass extinction of all time
5. Sarda Sahney and Michael Benton (2008) “Recovery from the most profound mass extinction of all time.” Proceedings of the Royal Society B, Volume 275, Number 1636, Pages 759–765
6. Douglas H. Erwin (July 1996) “The Mother of Mass Extinctions” Scientific American, Pages 72-78
7. Edward Osborne Wilson (1992) The Diversity of Life, Page 31
8. Becky Oskin (Feb 11, 2014) “Worst Mass Extinction Ever Took Only 60,000 Years.” Scientific American
9. Shu-zhong Shen et al. (2011) “Calibrating the End-Permian Mass Extinction” Science, Volume 334, Number 6061, Pages 1367-1372
10. Paul B. Wignall and Richard J. Twitchett (2002) “Extent, duration, and nature of the Permian-Triassic superanoxic event” Geological Society of America Special Papers, Volume 356, Pages 395–413
11. Changqun Caoet al. (2009) “Biogeochemical evidence for euxinic oceans and ecological disturbance presaging the end-Permian mass extinction event.” Earth and Planetary Science Letters, Volume 281, Pages 188–201
12. Lindsay Hays et al. (2012) “Biomarker and isotopic trends in a Permian–Triassic sedimentary section at Kap Stosch, Greenland.” Organic Geochemistry, Volume 43, Number 67–82
13. Katja Meyers (September 2008) “Biogeochemical controls on photic-zone euxinia during the end-Permian mass extinction”. Geology, Volume 36, Number 9, Pages 747–750
14. Lee Kump et al. (2005) “Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia.” Geology, Volume 33, Pages 397–400
15. Carol Potera (June 2008) “Corn Ethanol Goal Revives Dead Zone Concerns.” Environmental Health Prospectives.
16. Robert J. Diaz and Rutger Rosenberg (2008) “Spreading Dead Zones and Consequences for Marine Ecosystems” Science, Volume 321, Number 5891, Pages 926–929
17. Laurence Mee (November 2006) “Reviving Dead Zones” Scientific American
18. John Nielsen (2008-08-15) “‘Dead Zones’ Multiplying In World’s Oceans.” Morning Edition, NPR News.
19. David Perlman (July 15, 2008) “Scientists alarmed by ocean dead-zone growth” San Francisco Chronicle