Editing Permian–Triassic extinction event (section)

=== Aridification ===
Increasing continental aridity, a trend well underway even before the PTME as a result of the coalescence of the supercontinent Pangaea, was drastically exacerbated by terminal Permian volcanism and global warming.<ref name="SmithBothaViglietti2022">{{cite journal |last1=Smith |first1=Roger M. H. |last2=Botha |first2=Jennifer |last3=Viglietti |first3=Pia A. |date=15 October 2022 |title=Taphonomy of drought afflicted tetrapods in the Early Triassic Karoo Basin, South Africa |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018222003777 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=604 |page=111207 |doi=10.1016/j.palaeo.2022.111207 |bibcode=2022PPP...60411207S |s2cid=251781291 |access-date=23 May 2023|url-access=subscription }}</ref> The combination of global warming and drying generated an increased incidence of wildfires.<ref>{{cite journal |last1=Song |first1=Yi |last2=Tian |first2=Yuan |last3=Yu |first3=Jianxin |last4=Algeo |first4=Thomas J. |last5=Luo |first5=Genming |last6=Chu |first6=Daoliang |last7=Xie |first7=Shucheng |date=August 2022 |title=Wildfire response to rapid climate change during the Permian-Triassic biotic crisis |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818122001394 |journal=[[Global and Planetary Change]] |volume=215 |page=103872 |doi=10.1016/j.gloplacha.2022.103872 |bibcode=2022GPC...21503872S |s2cid=249857664 |access-date=23 May 2023|url-access=subscription }}</ref> Tropical coastal swamp floras such as those in South China may have been very detrimentally impacted by the increase in wildfires,<ref name="EcologicalDisturbanceTropicalPeatlands">{{cite journal |last1=Chu |first1=Daoliang |last2=Grasby |first2=Stephen E. |last3=Song |first3=Haijun |last4=Dal Corso |first4=Jacopo |last5=Wang |first5=Yao |last6=Mather |first6=Tamsin A. |last7=Wu |first7=Yuyang |last8=Song |first8=Huyue |last9=Shu |first9=Wenchao |last10=Tong |first10=Jinnan |last11=Wignall |first11=Paul Barry |date=3 January 2020 |title=Ecological disturbance in tropical peatlands prior to marine Permian-Triassic mass extinction |journal=[[Geology (journal)|Geology]] |volume=48 |issue=3 |pages=288–292 |doi=10.1130/G46631.1 |bibcode=2020Geo....48..288C |s2cid=214468383 |doi-access=free }}</ref> though it is ultimately unclear if an increase in wildfires played a role in driving taxa to extinction.<ref>{{cite journal |last1=Benton |first1=Michael James |last2=Newell |first2=Andrew J. |date=May 2014 |title=Impacts of global warming on Permo-Triassic terrestrial ecosystems |url=https://www.sciencedirect.com/science/article/abs/pii/S1342937X12004169 |journal=[[Gondwana Research]] |volume=25 |issue=4 |pages=1308–1337 |doi=10.1016/j.gr.2012.12.010 |bibcode=2014GondR..25.1308B |access-date=26 May 2023|url-access=subscription }}</ref>

Aridification trends varied widely in their tempo and regional impact. Analysis of the fossil river deposits of the floodplains of the Karoo Basin indicate a shift from [[meander]]ing to [[braided river]] patterns, indicating a very abrupt drying of the climate.<ref>{{cite journal |last=Smith |first=R.M.H. |date=16 November 1999 |title=Changing fluvial environments across the Permian–Triassic boundary in the Karoo Basin, South Africa and possible causes of tetrapod extinctions |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=117 |issue=1–2 |pages=81–104 |bibcode=1995PPP...117...81S |doi=10.1016/0031-0182(94)00119-S}}</ref> The climate change may have taken as little as 100,000 years, prompting the extinction of the unique ''Glossopteris'' flora and its associated herbivores, followed by the carnivorous guild.<ref>{{cite book |last=Chinsamy-Turan |title=Forerunners of mammals : radiation, histology, biology |publisher=[[Indiana University Press]] |year=2012 |isbn=978-0-253-35697-0 |editor=Anusuya |location=Bloomington}}</ref> A pattern of aridity-induced extinctions that progressively ascended up the food chain has been deduced from Karoo Basin biostratigraphy.<ref name="SmithBotha2014" /> Evidence for aridification in the Karoo across the Permian-Triassic boundary is not, however, universal, as some palaeosol evidence indicates a wettening of the local climate during the transition between the two geologic periods.<ref>{{cite journal |last1=Gastaldo |first1=Robert A. |last2=Kus |first2=Kaci |last3=Tabor |first3=Neil |last4=Neveling |first4=Johann |date=26 June 2020 |title=Calcic Vertisols in the upper Daptocephalus Assemblage Zone, Balfour Formation, Karoo Basin, South Africa: Implications for Late Permian Climate |url=https://pubs.geoscienceworld.org/sepm/jsedres/article-abstract/90/6/609/587564/Calcic-Vertisols-in-the-upper-Daptocephalus |journal=[[Journal of Sedimentary Research]] |volume=90 |issue=6 |pages=609–628 |doi=10.2110/jsr.2020.32 |bibcode=2020JSedR..90..609G |s2cid=221865490 |access-date=31 May 2023|url-access=subscription }}</ref> Evidence from the [[Sydney Basin]] of eastern Australia, on the other hand, suggests that the expansion of semi-arid and arid climatic belts across Pangaea was not immediate but was instead a gradual, prolonged process. Apart from the disappearance of [[peatland]]s, there was little evidence of significant sedimentological changes in depositional style across the Permian-Triassic boundary.<ref name="Fielding2020">{{cite journal |last1=Fielding |first1=Christopher R. |last2=Frank |first2=Tracy D. |last3=Tevyaw |first3=Allen P. |last4=Savatic |first4=Katarina |last5=Vajda |first5=Vivi |last6=McLoughlin |first6=Stephen |last7=Mays |first7=Chris |last8=Nicoll |first8=Robert S. |last9=Bocking |first9=Malcolm |last10=Crowley |first10=James L. |date=19 July 2020 |title=Sedimentology of the continental end-Permian extinction event in the Sydney Basin, eastern Australia |url=https://onlinelibrary.wiley.com/doi/10.1111/sed.12782 |journal=Sedimentology |volume=68 |issue=1 |pages=30–62 |doi=10.1111/sed.12782 |s2cid=225605914 |access-date=30 October 2022}}</ref> Instead, a modest shift to amplified seasonality and hotter summers is suggested by palaeoclimatological models based on weathering proxies from the region's Late Permian and Early Triassic deposits.<ref name="Fielding2019">{{cite journal |last1=Fielding |first1=Christopher R. |last2=Frank |first2=Tracy D. |last3=McLoughlin |first3=Stephen |last4=Vajda |first4=Vivi |last5=Mays |first5=Chris |last6=Tevyaw |first6=Allen P. |last7=Winguth |first7=Arne |last8=Winguth |first8=Cornelia |last9=Nicoll |first9=Robert S. |last10=Bocking |first10=Malcolm |last11=Crowley |first11=James L. |date=23 January 2019 |title=Age and pattern of the southern high-latitude continental end-Permian extinction constrained by multiproxy analysis |journal=[[Nature Communications]] |volume=10 |issue=385 |page=385 |doi=10.1038/s41467-018-07934-z |pmid=30674880 |pmc=6344581 |bibcode=2019NatCo..10..385F }}</ref> In the Kuznetsk Basin of southwestern Siberia, an increase in aridity led to the demise of the humid-adapted ''Cordaites'' forests in the region a few hundred thousand years before the Permian-Triassic boundary. Drying of this basin has been attributed to a broader poleward shift of drier, more arid climates during the late Changhsingian before the more abrupt main phase of the extinction at the Permian-Triassic boundary that disproportionately affected tropical and subtropical species.<ref name="DavydovEtAl2021PPP" />

The persistence of hyperaridity varied regionally as well. In the North China Basin, highly arid climatic conditions are recorded during the latest Permian, near the Permian-Triassic boundary, with a swing towards increased precipitation during the Early Triassic, the latter likely assisting biotic recovery following the mass extinction.<ref name="YuEtAl2022">{{cite journal |last1=Yu |first1=Yingyue |last2=Tian |first2=Li |last3=Chu |first3=Daoliang |last4=Song |first4=Huyue |last5=Guo |first5=Wenwei |last6=Tong |first6=Jinnan |date=1 January 2022 |title=Latest Permian–Early Triassic paleoclimatic reconstruction by sedimentary and isotopic analyses of paleosols from the Shichuanhe section in central North China Basin |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018221005113 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=585 |page=110726 |doi=10.1016/j.palaeo.2021.110726 |bibcode=2022PPP...58510726Y |s2cid=239498183 |access-date=6 November 2022|url-access=subscription }}</ref><ref name="ZhuEtAl2022">{{cite journal |last1=Zhu |first1=Zhicai |last2=Liu |first2=Yongqing |last3=Kuang |first3=Hongwei |last4=Newell |first4=Andrew J. |last5=Peng |first5=Nan |last6=Cui |first6=Mingming |last7=Benton |first7=Michael J. |date=September 2022 |title=Improving paleoenvironment in North China aided Triassic biotic recovery on land following the end-Permian mass extinction |doi-access=free |journal=[[Global and Planetary Change]] |volume=216 |page=103914 |doi=10.1016/j.gloplacha.2022.103914 |bibcode=2022GPC...21603914Z }}</ref> Elsewhere, such as in the Karoo Basin, episodes of dry climate recurred regularly in the Early Triassic, with profound effects on terrestrial tetrapods.<ref name="SmithBothaViglietti2022" />

The types and diversity of ichnofossils in a locality has been used as an indicator measuring aridity. Nurra, an ichnofossil site on the island of [[Sardinia]], shows evidence of major drought-related stress among crustaceans. Whereas the Permian subnetwork at Nurra displays extensive horizontal backfilled traces and high ichnodiversity, the Early Triassic subnetwork is characterised by an absence of backfilled traces, an ichnological sign of aridification.<ref>{{cite journal |last1=Baucon |first1=Andrea |last2=Ronchi |first2=Ausonio |last3=Felletti |first3=Fabrizio |last4=Neto de Carvalho |first4=Carlos |date=15 September 2014 |title=Evolution of Crustaceans at the edge of the end-Permian crisis: Ichnonetwork analysis of the fluvial succession of Nurra (Permian–Triassic, Sardinia, Italy) |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018214002909 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=410 |pages=74–103 |doi=10.1016/j.palaeo.2014.05.034 |bibcode=2014PPP...410...74B |access-date=8 April 2023|url-access=subscription }}</ref>