permian power tong free sample

The end-Permian extinction (EPE) has been considered to be contemporaneous on land and in the oceans. However, re-examined floristic records and new radiometric ages from Gondwana indicate a nuanced terrestrial ecosystem response to EPE global change. Paleosol geochemistry and climate simulations indicate paleoclimate change likely caused the demise of the widespread glossopterid ecosystems in Gondwana. Here, we evaluate the climate response of plants to the EPE via dendrochronology snapshots to produce annual-resolution records of tree-ring growth for a succession of late Permian and early Middle Triassic fossil forests from Antarctica. Paleosol geochemistry indicates a shift in paleoclimate towards more humid conditions in the Early and early Middle Triassic relative to the late Permian. Paleosol morphology, however, supports inferences of a lack of forested ecosystems in the Early Triassic. The plant responses to this paleoclimate change were accompanied by enhanced stress during the latest Permian as determined by high-resolution paleoclimate analysis of wood growth intervals. These results suggest that paleoclimate change during the late Permian exerted significant stress on high-latitude forests, consistent with the hypothesis that climate change was likely the primary driver of the extinction of the glossopterid ecosystems.

The end-Permian extinction (EPE) was one of the most severe mass extinctions in the history of metazoan life. The effects of the EPE were pronounced for marine organisms, including a nearly instantaneous (~ 30 kyr) record of extinction in paleotropical seaways

During the late Permian, glossopterids occurred on every continental landmass of Gondwana, and were the predominant arborescent taxa of terrestrial ecosystems at paleopolar latitudes

What were the factors that led to the demise of the glossopterid ecosystems? Recent paleoclimate simulations and sediment geochemistry from eastern Australia postulate a climate-forced stress on plant growth via paleoclimate simulations for the Bowen and Sydney basins1). Both regions preserve paleopolar forested ecosystems in the late Permian and early Middle Triassic. It is demonstrated here that just prior to the demise of the glossopterid floral province, a distinct change in decadal-scale paleoclimate oscillations had occurred, which resulted in greater stress on arborescent taxa. Long-term analysis of paleoprecipitation and evapotranspiration from paleosols in the study region contextualize these stresses as being primarily related to increasing ratios of precipitation to evapotranspiration, concurrent with climate warming. While the paleoclimate in the early Middle Triassic was similar to the latest Permian, the plant responses to this climate were markedly more amenable in the Triassic than in the latest Permian. This result stands in stark contrast to the earlier late Permian record of plant-climate response, suggesting that by the latest Permian the polar forested ecosystems were in a state of disequilibrium, with plants failing to adapt to a sharply-changing climate.

Map and paleogeography of the study area. (a) Map of the study locations, CTAM and SVL, on Antarctica. Exposures of major geologic units are shown, ice/snow where not shaded. (b) Paleogeographic reconstruction of the late Permian for Gondwana. Permian–Triassic depositional basins are shaded, study locations indicated by stars. The boxed region of eastern Australia highlights the correlative stratigraphy discussed in the text

Antarctica hosted several depositional basins that were actively subsiding during the late Paleozoic and early Mesozoic, of these the Transantarctic Basin was the largest (Fig. 1a). During the Permian–Triassic the Transantarctic Basin was situated close to the paleo south pole (Fig. 1b). The foreland-style basin preserves predominantly terrestrial strata with abundant plant fossils (Fig. 2). Stratigraphic names and correlations are broadly subdivided by their occurrence in the central Transantarctic Mountains (CTAM) area and southern Victoria Land (SVL, Fig. 2a,b). In the CTAM succession, Permian strata include the Buckley Formation and part of the lower Fremouw Formation in the vicinity of the Shackleton Glacier area

Stratigraphy of the study area. (a) Permian and Triassic stratigraphy of the central Transantarctic Mountains (CTAM). Measured sections from Collinson Ridge, McIntyre Promontory, and Graphite Peak are displayed in two configurations. The lithostratigraphy configuration places a datum at the contact between the Buckley and Fremouw formations. The available maximum depositional agesb) Permian and Triassic stratigraphy for southern Victoria Land (SVL), Allan Hills (after

In the CTAM area, palynology, vertebrate biostratigraphy, and maximum depositional ages based on U–Pb analyses on zircon crystals constrains the age information for these successions. Protohaploxypinus microcorpus has been recovered from the upper Buckley Formation at Graphite Peak below the first occurrence of Lystrosaurus (Fig. 2a)P. microcorpus Zone in eastern Australian. In the Shackleton Glacier area (Layman Peak), a maximum depositional age of 253.5 ± 2.0 Ma from U–Pb analyses on zircon confirms a late Permian age of the Buckley Formation However, at Collinson Ridge, the contact of the Buckley and Fremouw formations has yielded a maximum depositional age of 250.3 ± 2.2 Ma (Fig. 2a)P. microcorpus occurs in the upper Buckley Formation at Graphite Peak in association with Vertebraria. Thus, there are two significantly different paleobiologic scenarios in these strata that depend on how the available chronologic data are organized (Fig. 2a). If it is assumed that the lithostratigraphic separation of the Buckley and Fremouw formations is not diachronous, then the choice of the Buckley and Fremouw contact as a datum result in: (1) an older age for P. microcorpus in Antarctica relative to the Induan age of P. microcorpus Zone in eastern AustraliaP. microcorpus is often in the Lopingian; and (2) possible extension of glossopterid ecosystems in the Transantarctic Basin in the vicinity of Collinson Ridge to much younger time intervals in the late Permian or possibly the Early Triassic. Conversely, if the last appearance of coal and/or glossopterid megafossils is used as a datum in the CTAM area, the implications are: (1) synchronous disappearance of glossopterid megafossils over a time range that is consistent with eastern Australia but with the possibility of a much younger time for the demise of glossopterids in Antarctica; and (2) a more consistent timing of the first occurrence of P. microcorpus in Antarctica with the P. microcorpus Zone eastern Australia. However, the potential for floral provincialism across GondwanaP. microcorpus in Antarctica is evidence of range expansion of the plants that produced this pollen. In both cases, however, the demise of glossopterids on Antarctica is either consistent with or younger than the high-precision calibration of glossopterid extinction in eastern Australia

Late Permian fossil wood was collected from the upper Buckley Formation at McIntyre Promontory from a dense interval of allochthonous fossil wood ~ 15 m from the uppermost carbonaceous shale in the succession (Fig. 2a). Fossil wood with glossopterid affinities and co-occurring with Vertebraria at Shenk Peak and Collinson Ridge were collected in the lower Fremouw Formation at 10–30 m, respectively, below the first occurrence of Lystrosaurus remains (Fig. 2a). The Shenk Peak fossil wood occurs as sub horizontal to horizontal wood fragments in the upper horizon of a densely Vertebraria-rooted paleosol. The Collinson Ridge material occurs as predominantly in situ fossil stumps, with a few samples of allochthonous fossil wood. The middle Fremouw Formation, and lower Fremouw Formation in the Beardmore Glacier area, contain the palynomorph Aratisporites parvispinosus, which corresponds to the late Early Triassic Protohaploxypinus samoilovichii and Aratisporites tenuispinosus biozones of eastern AustraliaAngonisaurus, which has been correlated to the Cynognathus Assemblage Zone, Criodon-Ufudocyclops subzone of the Karoo Basin

Cross-matched tree-ring widths (TRW) are converted to an index called the Ring Width Index (RWI), which evaluates the measured TRW in the sample against the expected TRW produced from a spline fitted to the data (Fig. ​(Fig.3a–f).3a–f). Climate, being one of the state factors for tree growth, is anticipated to be a maximum signal in these RWI values due to the principle of ecologic amplitude​(Figs.3g,3g, ​g,44 and ​and5),5), which is a visualization of the Fourier period on the ordinate axis and the time dimension on the abscissa. The color map in the scalogram refers to the power (square of the wavelet coefficient) of the wavelet against the time series. The null hypothesis for this analysis is of a red noise spectrum, and regions at 0.05 significance level against the null hypothesis are illustrated by bold dark lines. The conical feature, determined by the e-folding time of the wavelet, in each scalogram reflects the region where edge-effects create spurious correlations. Replication of these dendrochronologic results is assessed by statistical comparison of two nearly identical TRW chronologies from the Lower Triassic Lashly Formation using a cross-wavelet analysis (Figs. ​(Figs.3g,h).3g,h). Statistics of inter-tree cross-matches are provided in Supplementary file

Wavelet scalograms of the RWI data and land surface temperature (LST). (a–f) The color spectrum indicates wavelet power (square of wavelet coefficient), higher power indicating a stronger signal in the data. The shaded envelope is the cone of influence reflecting wavelet coefficients that are erroneous near the edge of each time series. The dark lines indicate the wavelet power domains that are significant as compared to red noise at the 0.05 level. The abscissa represents the time represented in each chronology and is directly related to the RWI data. The ordinate axis represents the Fourier period and is scaled with 16 voices per octave. (g) Land surface temperature (LST) through time in Antarctica (dashed line and dashed circles)Glossopteris fossils are shown for Antarctica

Tree growth patterns and paleoclimate. (a,b) RWI and CWT analysis with the derivative of a gaussian (DOG, 2nd derivative) wavelet for the Late Permian Collinson Ridge chronology. (c,d) RWI and CWT analysis via the DOG wavelet for the Triassic Allan Hills chronology. Intervals of reduced/enhanced growth as determined by RWI that correlate with significant wavelet coefficients are illustrated by the shaded vertical bars. (e) Paleoclimate model results from paleosol geochemistry at each area in the study region from the Permian–Triassic, ET = evapotranspiration, Eppt = energy from precipitation, where these parameters are calculated from the equations for paleosol-based paleoclimate proxies

The stratigraphically lowest samples reported here are from the upper Buckley Formation, McIntyre Promontory (see supplementary file 2 units less than the other data sets reported here, which indicates it has a shorter range of scales than the other chronologies (Fig. 3a). Thus, the decreased sample length inhibits comparisons of the longer periodicities extracted from the other chronologies reported here. However, the chronology is robust with a mean overlap of individual TRW records of 20 years. The mean correlation between radii of individual trees (intra-tree correlation) is better than 0.7, with percent parallel covariation better than 80%. For paleoclimate inference, we use the subsample signal strength (SSS), which is a measure of the depth of information contained in a chronology based on the number of overlapping measured transects, the number of trees represented, and the interseries correlation between trees. An arbitrary cutoff of 0.5 is used by convention to assess chronology lengths that are suitable for paleoclimate analysis (SSS > 0.5). The SSS cutoff of 0.5 is reached by year 22 of the 42 years chronology. By comparison, the TRW chronology from the Weller Coal Measures, Allan Hills, exceeded the SSS cutoff by year 26 of the 86 years chronology (Fig. 3b). For the McIntyre Promontory chronology and the Weller Coal Measures, very narrow rings are well-correlated throughout the chronology, whereas anomalously wide rings correlate well, but are not well-expressed in every sample. Although not precisely correlated across the Transantarctic Basin, these fossil wood chronologies are both approximately 15 m below the top of the respective lithostratigraphic unit contacts between upper Permian and lower Triassic strata.

Individual fossil trees from Shenk Peak are associated with an intensely root-turbated paleosol preserving vertical to subvertical Vertebraria fossils. Fossil wood from Shenk Peak is stratigraphically higher than the samples from McIntyre Promontory, occurring within the lithostratigraphic division of the lower Fremouw Formation2 dimensions of the: Allan Hills (late Permian), Collinson Ridge (latest Permian), and Triassic chronologies; thus, producing meaningful comparisons of periodicity of RWI variation of these four TRW records (Fig. 3c). The mean correlation between radii of individual trees (intra-tree correlation) is better than 0.8, with percent parallel covariation better than 85%. The SSS cutoff of 0.5 is reached by year 35 of the 113 years chronology. Very narrow rings that occur are exceptionally well-correlated with the exception of sample five at year 27 of the chronology. Unlike the stratigraphically lower chronologies, wide rings are well-correlated and expressed well in each sample.

The cross-wavelet power spectrum​Fig.3e,f)3e,f) produces significant power (0.05 significance level) for Fourier periods ranging from 14–16 years and 20–64 years, with negative correlations existing for Fourier periods 14–16 years and positive correlations for Fourier periods 16 years and 32 years (Fig. 3g). Wavelet coherence, analogous to a correlation coefficient ranging from 0 to 1, is significant at the 0.05 level for Fourier periods 3–4 years, 10 years, and 32 years (Fig. 3h). Average coherence values are better than 0.85 for the higher frequency signals, and better than 0.95 for the lower frequency signals. The phase is complex for higher frequencies, displaying both lag/lead patterns and positive/negative correlations with respect to time. However, the phase is more organized at lower frequencies with either the ELG chronology lagging behind the VC chronology, or positive correlation between the two chronologies. The range of Fourier periods with significant cross-wavelet power and wavelet coherence are identical to the significant Fourier periods identified in each chronology individually using CWT analysis (Fig. 4e,f), with 0.95 average wavelet coherence for the prominent lower frequency signals in both TRW chronologies.

CWT results for the lowest stratigraphic position of late Permian fossil wood (upper Buckley Formation, McIntyre Promontory; Weller Coal Measures, Allan Hills) indicate a lack of Fourier periods > 20 years, with significant signals at the 2 years, 3–5 years, and 9–15 years (Fig. ​(Fig.4a,b).4a,b). The higher frequency signals are not consistent over the length of the chronology, however, the shorter frequency signals are more consistent. For the stratigraphically highest late Permian fossil wood samples (lower Fremouw Formation, Shenk Peak; Collinson Ridge) there is a similar range of high frequency signals as for the stratigraphically lower samples, however, there is an emergence of prominent Fourier periods in the 20–30 years range that are continuous or more frequently occurring throughout a chronology (Fig. ​(Fig.4c,d).4c,d). The Collinson Ridge chronology displays a marked lack of significant high frequency signals for nearly a century, with high frequency signals occurring over ~ 50 years durations on either end of the chronology. The Triassic chronologies (Allan Hills) display intermittent high frequency signals and more persistent periodicities in the 15–30 years range, with potentially minor contributions of periods in the ~ 50 years range (Fig. ​(Fig.44e,f).

Long-term paleoclimate averages from the sedimentary record are developed here through upper Permian to lower and middle Triassic strata. Comparisons of reconstructed paleoclimates are made between the well-studied Sydney and Bowen basins4g). Paleosol geochemistry from Graphite Peak, Transantarctic Basin4g). The two stratigraphic records of LSTs produce differing magnitudes of variation over time, with the Sydney and Bowen basins preserving a more gradual change per unit time, but with clear oscillations (Fig. 4g). In contrast, the paleosol results from Graphite Peak display large variations in LST estimates. However, both study areas produce similar long-term trends in paleo-LST, with: (1) a > 10 °C warming during the late Permian; and (2) identical temperatures that remain constant across the Permian–Triassic boundary. The Early–Middle Triassic results, however, indicate remarkable differences between each area in paleo-LST variance through time (Fig. 4g).

Paleosols of likely Induan age from Graphite Peak and the Allan Hills display an overwhelming decrease in organic carbon content and a more limited variation in the types of soil horizons as compared to the late Permian paleosols in the same areas

The data presented here provides direct evidence of the response of plants to climate in the late Permian and early Middle Triassic through high-resolution analysis of paleoclimate data at discrete time intervals within the stratigraphic successions studied herein. For context, the late Permian ecosystems of Antarctica were low-diversity forests with arborescent taxa dominated by the glossopterids. Despite low generic diversity, however, isotopic data indicate varied functional diversity of glossopterids in the form of leaf habitDicroidium and associated corystosperm wood morphogenera

What were the specific changes to paleoclimate? Changes in atmospheric circulation and an increase in humidity likely explain the long-term paleoclimate averages of sediment geochemistry data5e) presented herein confirms that assessment, for long-term averaging of paleoclimate information. However, the dendrochronology data herein is presented at annual resolution, which has the potential to highlight specific climate change mechanisms. These results indicate a shift in internal climate oscillations from decadal to sub-decadal in the early late Permian to multidecadal oscillations in the latest Permian and early Middle Triassic. Without suitable comparison to annually resolved paleoclimate simulations, it is speculated that oscillatory phenomena, akin to the extant Arctic annular oscillation (AO) is a plausible atmospheric–surface ocean modern analogue that may explain some of the oscillatory behavior observed in the deep-time tree-ring chronologies. Given that AO, like our CWT results, is non-stationary and does not occur at a fixed periodicity and occurs at high latitudes. Furthermore, it is expected that because of declining hemispheric temperature gradients (Fig. 4f), the oscillatory climate behavior similar to AO may have weakened substantially by the latest Permian given the increase in multidecadal climate oscillations in tree-ring records at this time. The lengthening of the period of the internal oscillations of climate indicates that the impact of changes in rainfall or snow accumulation on this more expanded climate oscillatory framework negatively impacted tree growth of the glossopterids at these paleolatitudes (Fig. 5c).

Alternatively, the northward drift of Gondwana has been invoked to explain the observed changes in climate and flora through the late Permian–Triassic

The CWT analysis presented here uses the Morlet wavelet (Fig. 4a–f), which is useful for detecting oscillatory signals and their stationarity in a time series. However, because the Morlet wavelet uses real and imaginary numbers, the wavelet power includes information about amplitude and phase, hence resolution at fine-time scales is sacrificed for accuracy of the frequency domain5a–d). Of the growth years that correlate to significant wavelet coefficients in the latest Permian chronologies, 60–62% correspond to years of suppressed growth, mostly around the 30 years periodicity. In contrast, only 40% of the growth years in the early Middle Triassic correspond to suppressed growth, also mostly around the 30 years periodicity. Thus, despite similar patterns of oscillatory paleoclimate in the latest Permian and early Middle Triassic, the plant communities responded in vastly different ways to this climate state, with the latest Permian glossopterid forests being indicative of a highly stressed ecosystem.

Longer-term averages of paleoclimate information are derived from the morphologic and geochemical analysis of paleosols and sedimentary rocks (Figs. ​(Figs.4g4g and ​and55e)4g). A brief time interval across the Permian–Triassic boundary, however, was markedly devoid of LST variation in all areas. The Induan paleosol record from Antarctica indicates that during this timeframe of invariant LST, the soil-forming environment produced morphologically immature soil profiles with minimal organic carbon content. The greater range of temperature increase in the paleopolar regions of Gondwana may indicate that wildfires

Paleosol geochemistry from previous studies5e). These results stand in stark contrast to the overwhelming evidence for aridification in the paleotropical latitudes during the Late Permian

The Sydney and Bowen basins were adjacent to the study area during the late Permian–Middle Triassic. Recently, it has been hypothesized that terrestrial ecosystems underwent an ecologic collapse prior to the marine-defined EPE

This study documents the history of tree-ring growth at paleopolar latitudes from the late Permian–early Middle Triassic in order to evaluate the hypothesis that paleoclimate change was a principal cause of the demise of glossopterid ecosystems. Dendrochronologic results are statistically robust and highlight a change in the period and stationarity of oscillatory climate effects on tree-ring growth in the study area. Geospatial comparisons of dendrochronologic results indicate a subtle gradient existed between the two study regions, with the gradient decreasing into the early Middle Triassic, consistent with long-term averages of paleoclimate derived from paleosol climate proxies. Latest Permian tree-ring chronologies are markedly similar to the early Middle Triassic chronologies, with a key difference being the correlation of a 30 years signal with years of reduced growth for Permian trees and a correlation of a 30 years signal with years of enhanced growth for Triassic trees. These results add support to the hypothesis that paleoclimate exerted significant stress to terrestrial ecosystems during the late Permian and that these stressors occurred in advance of the marine record of the end-Permian extinction.

The fossil wood used in this study was collected from Permian and Triassic strata of the Transantarctic Basin in the CTAM and SVL regions of Antarctica. Each sample reflects fossil wood material collected directly from a sedimentary bed, preserved either in life position (in situ) or as an allochthonous fragment of woody debris. For each sample set, fossil wood was collected and processed for dendrochronology from the same sedimentary bed in order to minimize erroneous cross-matches of fossil wood from older/younger sedimentary deposits. Late Permian fossil wood was collected from the upper Buckley Formation at McIntyre Promontory (CTAM, S84°55.168′, E179°43.182′). Fossil wood stratigraphically close to the Permian–Triassic transition was collected from the lower Fremouw Formation at Shenk Peak and at Collinson Ridge (CTAM, S85°13.275′, W173°57.704′; S85°20.051′, W175°28.218′, respectively). Of these samples, only fossil wood at Collinson Ridge is preserved as in situ fragments. The remaining wood samples are preserved as horizontal to subhorizontal wood fragments in sandstone/siltstone strata. Fossil wood material was collected from specimens where > 20 tree-rings can be identified (~ 10 cm, or greater, diameter), a minimum number of rings for replicable cross-dating. Comparisons are made to previous dendrochronologic results from the Permian Weller Coal Measures (S76°42.577′, E159°42.826′) and Triassic Lashly Formation (S76°40.524′, E159°52.203′), Allan Hills (SVL

Tree rings identified in hand sample are cross-referenced to thin-sections of the transverse and radial planes of fossil wood. The taxa studied include glossopterid wood from upper Permian successions in CTAM and SVL, which are dominated by woody axes with affinity to the glossopterids, and are associated with megafloral remains of Glossopteris leaves, Vertebraria roots, and reproductive organs related to the glossopteridsAustraloxylon. The early Middle Triassic, however, contains a more diverse megafloral community of arborescent plants. Distinguishing wood morphogenera between conifers and corystosperms is challenging due to the conservative nature and few unique properties to distinguish these taxaDicroidium leaf compressions and the woody axes display the prominent lobed property associated with corystosperm fossil wood.

CWT results from two independently measured (by authors ELG and VC) TRW chronologies from the Triassic Lashly B member, Allan Hills (SVL) are compared via the technique of cross-wavelet transform to produce the cross-wavelet power spectrum and wavelet coherence

Paleosol morphology and major element geochemistry are used to provide an independent assessment of paleoclimate in the study region from the Permian and Triassic. Paleo-rainfall estimates are derived from the CIA-K proxy

E.L.G., P.E.R., B.A.A., and G.C. performed field investigations of Upper Permian and Lower Triassic strata in the field area, including sample collections and descriptions. E.L.G., M.M.M., V.C., and A.D. contributed to the dendrochronology; E.L.G. and V.C. performed the reproducibility test; E.L.G. and M.M.M. performed the geochemical measurement and analysis; and E.L.G. performed the CWT analysis and cross-wavelet transform. E.L.G. assembled the manuscript and all authors contributed to the manuscript revision.

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The Permian–Triassic (P–T, P–Tr)extinction event,End-Permian extinction eventGreat Dying,Permian and Triassic geologic periods, and with them the Paleozoic and Mesozoic eras respectively, approximately 251.9 million years ago.Earth"s most severe known extinction event,extinction of 57% of biological families, 83% of genera, 81% of marine speciesterrestrial vertebrate species.insects.

The speed of recovery from the extinction is disputed. Some scientists estimate that it took 10 million years (until the Middle Triassic), due both to the severity of the extinction and because grim conditions returned periodically over the course of the Early Triassic,Smithian-Spathian boundary extinction.Bear Lake County, near Paris, Idaho,Early Triassic marine ecosystem, taking around 3 million years to recover, while an unusually diverse and complex ichnobiota is known from Italy less than a million years after the end-Permian extinction.

Previously, it was thought that rock sequences spanning the Permian–Triassic boundary were too few and contained too many gaps for scientists to reliably determine its details.U–Pb zircon dates from five volcanic ash beds from the Global Stratotype Section and Point for the Permian–Triassic boundary at Meishan, China, establish a high-resolution age model for the extinction – allowing exploration of the links between global environmental perturbation, carbon cycle disruption, mass extinction, and recovery at millennial timescales.

It has been suggested that the Permian–Triassic boundary is associated with a sharp increase in the abundance of marine and terrestrial fungi, caused by the sharp increase in the amount of dead plants and animals fed upon by the fungi.paleontologists to identify the Permian–Triassic boundary in rocks that are unsuitable for radiometric dating or have a lack of suitable index fossils, but even the proposers of the fungal spike hypothesis pointed out that "fungal spikes" may have been a repeating phenomenon created by the post-extinction ecosystem during the earliest Triassic.alga;Reduviasporonites may even represent a transition to a lake-dominated Triassic world rather than an earliest Triassic zone of death and decay in some terrestrial fossil beds.Reduviasporonites, diluting these critiques.

Uncertainty exists regarding the duration of the overall extinction and about the timing and duration of various groups" extinctions within the greater process. Some evidence suggests that there were multiple extinction pulsesstrata in Meishan, Zhejiang Province in southeastern China, suggest that the main extinction was clustered around one peak.ostracod and brachiopod extinctions were separated by around 670,000 to 1.17 million years.Greenland, the decline of animal life is concentrated in a period approximately 10,000 to 60,000 years long, with plants taking an additional several hundred thousand years to show the full impact of the event.Lopingian strata in the Bowen Basin of Queensland indicates numerous intermittent periods of marine environmental stress from the middle to late Lopingian leading up to the end-Permian extinction proper.

An older theory, still supported in some recent papers,Guadalupian epoch of the Permian.dinocephalian genera died out at the end of the Guadalupian,Verbeekinidae, a family of large-size fusuline foraminifera.end-Guadalupian extinction on marine organisms appears to have varied between locations and between taxonomic groups – brachiopods and corals had severe losses.

Studies of the timing and causes of the Permian-Triassic extinction are complicated by the often-overlooked Capitanian extinction (also called the Guadalupian extinction), just one of perhaps two mass extinctions in the late Permian that closely preceded the Permian-Triassic event. In short, when the Permian-Triassic starts it is difficult to know whether the end-Capitanian had finished, depending on the factor considered.Capitanian. Further, it is unclear whether some species who survived the prior extinction(s) had recovered well enough for their final demise in the Permian-Triassic event to be considered separate from Capitanian event. A minority point of view considers the sequence of environmental disasters to have effectively constituted a single, prolonged extinction event, perhaps depending on which species is considered.

Marine invertebrates suffered the greatest losses during the P–Tr extinction. Evidence of this was found in samples from south China sections at the P–Tr boundary. Here, 286 out of 329 marine invertebrate genera disappear within the final two sedimentary zones containing conodonts from the Permian.diversity was probably caused by a sharp increase in extinctions, rather than a decrease in speciation.

The ammonoids, which had been in a long-term decline for the 30 million years since the Roadian (middle Permian), suffered a selective extinction pulse 10 million years before the main event, at the end of the Capitanian stage. In this preliminary extinction, which greatly reduced disparity, or the range of different ecological guilds, environmental factors were apparently responsible. Diversity and disparity fell further until the P–Tr boundary; the extinction here (P–Tr) was non-selective, consistent with a catastrophic initiator. During the Triassic, diversity rose rapidly, but disparity remained low.clades.

The Lilliput effect, a term used to describe the phenomenon of dwarfing of species during and immediately following a mass extinction event, has been observed across the Permian-Triassic boundary,

The Permian had great diversity in insect and other invertebrate species, including the largest insects ever to have existed. The end-Permian is the largest known mass extinction of insects;only mass extinction to significantly affect insect diversity.orders became extinct and ten more were greatly reduced in diversity. Palaeodictyopteroids (insects with piercing and sucking mouthparts) began to decline during the mid-Permian; these extinctions have been linked to a change in flora. The greatest decline occurred in the Late Permian and was probably not directly caused by weather-related floral transitions.

The Glossopteris-dominated flora that characterised high-latitude Gondwana collapsed in Australia around 370,000 years before the Permian-Triassic boundary, with this flora"s collapse being less constrained in western Gondwana but still likely occurring a few hundred thousand years before the boundary.

The Cordaites flora, which dominated the Angaran floristic realm corresponding to Siberia, collapsed over the course of the extinction.Kuznetsk Basin, the aridity-induced extinction of the regions"s humid-adapted forest flora dominated by cordaitaleans occurred approximately 252.76 Ma, around 820,000 years before the end-Permian extinction in South China, suggesting that the end-Permian biotic catastrophe may have started earlier on land and that the ecological crisis may have been more gradual and asynchronous on land compared to its more abrupt onset in the marine realm.

All Permian anapsid reptiles died out except the procolophonids (although testudines have morphologically-anapsid skulls, they are now thought to have separately evolved from diapsid ancestors). Pelycosaurs died out before the end of the Permian. Too few Permian diapsid fossils have been found to support any conclusion about the effect of the Permian extinction on diapsids (the "reptile" group from which lizards, snakes, crocodilians, and dinosaurs (including birds) evolved).

The groups that survived suffered extremely heavy losses of species and some terrestrial vertebrate groups very nearly became extinct at the end of the Permian. Some of the surviving groups did not persist for long past this period, but others that barely survived went on to produce diverse and long-lasting lineages. However, it took 30million years for the terrestrial vertebrate fauna to fully recover both numerically and ecologically.

It is difficult to analyze extinction and survival rates of land organisms in detail because few terrestrial fossil beds span the Permian–Triassic boundary. The best-known record of vertebrate changes across the Permian–Triassic boundary occurs in the Karoo Supergroup of South Africa, but statistical analyses have so far not produced clear conclusions.

Before the Permian mass extinction event, both complex and simple marine ecosystems were equally common. After the recovery from the mass extinction, the complex communities outnumbered the simple communities by nearly three to one,Mesozoic Marine Revolution.

Bivalves were fairly rare before the P–Tr extinction but became numerous and diverse in the Triassic, taking over niches that were filled primarily by brachiopods before the mass extinction event,rudist clams, became the Mesozoic"s main reef-builders. Some researchers think the change was attributable not only to the end-Permian extinction but also the ecological restructuring that began as a result of the Capitanian extinction.

The proto-recovery of terrestrial floras took place from a few tens of thousands of years after the end-Permian extinction to around 350,000 years after it, with the exact timeline varying by region.gymnosperm genera were replaced post-boundary by lycophytes – extant lycophytes are recolonizers of disturbed areas.

Most fossil insect groups found after the Permian–Triassic boundary differ significantly from those before: Of Paleozoic insect groups, only the Glosselytrodea, Miomoptera, and Protorthoptera have been discovered in deposits from after the extinction. The caloneurodeans, monurans, paleodictyopteroids, protelytropterans, and protodonates became extinct by the end of the Permian. Though Triassic insects are very different from those of the Permian, a gap in the insect fossil record spans approximately 15 million years from the late Permian to early Triassic. In well-documented Late Triassic deposits, fossils overwhelmingly consist of modern fossil insect groups.

Pinpointing the exact causes of the Permian–Triassic extinction event is difficult, mostly because it occurred over 250 million years ago, and since then much of the evidence that would have pointed to the cause has been destroyed or is concealed deep within the Earth under many layers of rock. The sea floor is completely recycled over around 200 million years by the ongoing process of plate tectonics and seafloor spreading, leaving no useful indications beneath the ocean.

The final stages of the Permian had two flood basalt events. A smaller one, the Emeishan Traps in China, occurred at the same time as the end-Guadalupian extinction pulse, in an area close to the equator at the time.Siberian Traps constituted one of the largest known volcanic events on Earth and covered over 2,000,000 square kilometres (770,000 sq mi) with lava.large igneous province of the Siberian Traps.PPM prior to the extinction event to around 8,000 PPM after the extinction.biogeochemical model, showed the consequences of the greenhouse effect on the marine environment, and concluded that the mass extinction can be traced back to volcanic CO2 emissions.coronene-mercury spikes – for a volcanic combustion cause of the mass extinction was published in 2020.

The Siberian Traps are underlain by thick sequences of Early-Mid Paleozoic aged carbonate and evaporite deposits, as well as Carboniferous-Permian aged coal bearing clastic rocks. When heated, such as by igneous intrusions, these rocks are capable of emitting large amounts of greenhouse and toxic gases. The unique setting of the Siberian Traps over these deposits is likely the reason for the severity of the extinction.carbonate rocks and into sediments that were in the process of forming large coal beds, both of which would have emitted large amounts of carbon dioxide, leading to stronger global warming after the dust and aerosols settled.δ13C excursion.Buchanan Lake Formation. According to their article, "coal ash dispersed by the explosive Siberian Trap eruption would be expected to have an associated release of toxic elements in impacted water bodies where fly ash slurries developed. ... Mafic megascale eruptions are long-lived events that would allow significant build-up of global ash clouds."7 Tg CO2, 4.4 × 106 Tg CO, 7.0 × 106 Tg H2S, and 6.8 × 107 Tg SO2. The data support a popular notion that the end-Permian mass extinction on the Earth was caused by the emission of enormous amounts of volatiles from the Siberian Traps into the atmosphere.

The release of methane from the clathrates has been considered as a cause because scientists have found worldwide evidence of a swift decrease of about 1% in the carbonate rocks from the end-Permian.13C ⁄ 12C ratio) that continues until the isotope ratio abruptly stabilised in the middle Triassic, followed soon afterwards by the recovery of calcifying life forms (organisms that use calcium carbonate to build hard parts such as shells).13C ⁄ 12C ratio, a 2002 review found most of them to be insufficient to account fully for the observed amount:

Marine organisms are more sensitive to changes in CO2 (carbon dioxide) levels than terrestrial organisms for a variety of reasons. CO2 is 28 times more soluble in water than is oxygen. Marine animals normally function with lower concentrations of CO2 in their bodies than land animals, as the removal of CO2 in air-breathing animals is impeded by the need for the gas to pass through the respiratory system"s membranes (lungs" alveolus, tracheae, and the like), even when CO2 diffuses more easily than oxygen. In marine organisms, relatively modest but sustained increases in CO2 concentrations hamper the synthesis of proteins, reduce fertilization rates, and produce deformities in calcareous hard parts. An analysis of marine fossils from the Permian"s final Changhsingian stage found that marine organisms with a low tolerance for hypercapnia (high concentration of carbon dioxide) had high extinction rates, and the most tolerant organisms had very slight losses. The most vulnerable marine organisms were those that produced calcareous hard parts (from calcium carbonate) and had low metabolic rates and weak respiratory systems, notably calcareous sponges, rugose and tabulate corals, calcite-depositing brachiopods, bryozoans, and echinoderms; about 81% of such genera became extinct. Close relatives without calcareous hard parts suffered only minor losses, such as sea anemones, from which modern corals evolved. Animals with high metabolic rates, well-developed respiratory systems, and non-calcareous hard parts had negligible losses except for conodonts, in which 33% of genera died out. This pattern is also consistent with what is known about the effects of hypoxia, a shortage but not total absence of oxygen. However, hypoxia cannot have been the only killing mechanism for marine organisms. Nearly all of the continental shelf waters would have had to become severely hypoxic to account for the magnitude of the extinction, but such a catastrophe would make it difficult to explain the very selective pattern of the extinction. Mathematical models of the Late Permian and Early Triassic atmospheres show a significant but protracted decline in atmospheric oxygen levels, with no acceleration near the P–Tr boundary. Minimum atmospheric oxygen levels in the Early Triassic are never less than present-day levels and so the decline in oxygen levels does not match the temporal pattern of the extinction.

On land, the increasing acidification of rainwater caused increased soil erosion as a result of the increased acidity of forest soils, evidenced by the increased influx of terrestrially derived organic sediments found in marine sedimentary deposits during the end-Permian extinction.soil acidification may have resulted from the decline of infaunal invertebrates like tubificids and chironomids, which remove acid metabolites from the soil.

Evidence for widespread ocean anoxia (severe deficiency of oxygen) and euxinia (presence of hydrogen sulfide) is found from the Late Permian to the Early Triassic.Tethys and Panthalassic Oceans, evidence for anoxia, including fine laminations in sediments, small pyrite framboids, high uranium/thorium ratios, and biomarkers for green sulfur bacteria, appear at the extinction event.Spiti, India,Meishan, China,Alberta,diagenetic product of isorenieratene, are widely used as indicators of photic zone euxinia because green sulfur bacteria require both sunlight and hydrogen sulfide to survive. Their abundance in sediments from the P–T boundary indicates euxinic conditions were present even in the shallow waters of the photic zone.

A severe anoxic event at the end of the Permian would have allowed sulfate-reducing bacteria to thrive, causing the production of large amounts of hydrogen sulfide in the anoxic ocean, turning it euxinic. Upwelling of this water may have released massive hydrogen sulfide emissions into the atmosphere and would poison terrestrial plants and animals and severely weaken the ozone layer, exposing much of the life that remained to fatal levels of UV radiation.biomarker evidence for anaerobic photosynthesis by Chlorobiaceae (green sulfur bacteria) from the Late-Permian into the Early Triassic indicates that hydrogen sulfide did upwell into shallow waters because these bacteria are restricted to the photic zone and use sulfide as an electron donor. The hypothesis has the advantage of explaining the mass extinction of plants, which would have added to the methane levels and should otherwise have thrived in an atmosphere with a high level of carbon dioxide. Fossil spores from the end-Permian further support the theory; many spores show deformities that could have been caused by ultraviolet radiation, which would have been more intense after hydrogen sulfide emissions weakened the ozone layer.

Some scientists have challenged the anoxia hypothesis on the grounds that long-lasting anoxic conditions could not have been supported if Late Permian thermohaline ocean circulation conformed to the "thermal mode" characterised by cooling at high latitudes. Anoxia may have persisted under a "haline mode" in which circulation was driven by subtropical evaporation, although the "haline mode" is highly unstable and was unlikely to have represented Late Permian oceanic circulation.

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 peatlands, there was little evidence of significant sedimentological changes in depositional style across the Permian-Triassic boundary.

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. This 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.

A large impact might have triggered other mechanisms of extinction described above,Siberian Traps eruptions at either an impact siteantipode of an impact site.rapidly evolve to survive, as would be expected if the Permian–Triassic event had been slower and less global than a meteorite impact.

Another impact hypothesis postulates that the impact event which formed the Araguainha crater, whose formation has been dated to 254.7 ± 2.5 million, a possible temporal range overlapping with the end-Permian extinction,5 to 106 of TNT, around two orders of magnitude lower than the impact energy believed to be required to induce mass extinctions) released by the impact.

In the mid-Permian (during the Kungurian age of the Permian"s Cisuralian epoch), Earth"s major continental plates joined, forming a supercontinent called Pangaea, which was surrounded by the superocean, Panthalassa.

Oceanic circulation and atmospheric weather patterns during the mid-Permian produced seasonal monsoons near the coasts and an arid climate in the vast continental interior.

Pangaea"s formation depleted marine life at near catastrophic rates. However, Pangaea"s effect on land extinctions is thought to have been smaller. In fact, the advance of the therapsids and increase in their diversity is attributed to the late Permian, when Pangaea"s global effect was thought to have peaked.

While Pangaea"s formation certainly initiated a long period of marine extinction, its impact on the "Great Dying" and the end of the Permian is uncertain.

However, there may be some weak links in this chain of events: the changes in the 13C/12C ratio expected to result from a massive release of methane do not match the patterns seen throughout the early Triassic;thermohaline circulation that may have existed at the end of the Permian are not likely to have supported deep-sea anoxia.

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