Jinnan Tong

Two pulses of extinction during the Permian–Triassic crisis

Over 90% of marine species were lost during the end-Permian extinction. Fossil data show that the crisis in China was marked by two distinct phases of marine extinction separated by a 180,000-year recovery period. The Permian–Triassic mass extinction is the most severe biotic crisis identified in Earth history. Over 90% of marine species were eliminated1,2, causing the destruction of the marine ecosystem structure3. This biotic crisis is generally interpreted as a single extinction event around 252.3 million years ago2,4,5,6, and has been variously attributed to the eruption of the Siberian Traps or possibly a bolide impact7,8,9,10. Here we demonstrate that the marine extinction consisted of two pulses, separated by a 180,000-year recovery phase. We evaluated the range of 537 species representing 17 marine groups in seven Chinese sections from a 450,000-year interval spanning the Permian–Triassic boundary. The first stage of extinction occurred during the latest Permian, and was marked by the extinction of 57% of species, namely all plankton and some benthic groups, including algae, rugose corals, and fusulinids. The second phase occurred in the earliest Triassic, and resulted in the extinction of 71% of the remaining species. This second extinction phase fundamentally altered the marine ecosystem structure that had existed for the previous 200 million years. Because the two pulses showed different extinction selectivity, we conclude that they may have had different environmental causes.

Recovery tempo and pattern of marine ecosystems after the end-Permian mass extinction

High-resolution sampling of more than 10,000 microfossils from seven Late Permian−Middle Triassic paleoequatorial sections in south China refutes claims for a 5 m.y. recovery delay after the end-Permian mass extinction. We show that level-bottom seafloor diversity began to recover in the early Smithian, little more than 1 m.y. after the mass extinction, while recovery of reef-building metazoans began 4 m.y. later, in the Anisian. A further mass extinction in the late Smithian, identified in the pelagic fossil record, is weakly manifest as a temporary pause in diversification among benthic communities. In the Early Triassic of south China, the offshore diversity increase began before then, in shallower settings. The recovery from the end-Permian mass extinction in south China was therefore significantly more rapid and environmentally more complex than hitherto known.

Anoxia/high temperature double whammy during the Permian-Triassic marine crisis and its aftermath

The Permian-Triassic mass extinction was the most severe biotic crisis in the past 500 million years. Many hypotheses have been proposed to explain the crisis, but few account for the spectrum of extinction selectivity and subsequent recovery. Here we show that selective losses are best accounted for by a combination of lethally warm, shallow waters and anoxic deep waters that acted to severely restrict the habitable area to a narrow mid-water refuge zone. The relative tolerance of groups to this double whammy provides the first clear explanation for the selective extinction losses during this double-pulsed crisis and also the fitful recovery. Thus, high temperature intolerant shallow-water dwellers, such as corals, large foraminifers and radiolarians were eliminated first whilst high temperature tolerant ostracods thrived except in anoxic deeper-waters. In contrast, hypoxia tolerant but temperature intolerant small foraminifers were driven from shallow-waters but thrived on dysoxic slopes margins. Only those mollusc groups, which are tolerant of both hypoxia and high temperatures, were able to thrive in the immediate aftermath of the extinction. Limited Early Triassic benthic recovery was restricted to mid-water depths and coincided with intervals of cooling and deepening of water column anoxia that expanded the habitable mid-water refuge zone.

Environmental and biotic turnover across the Permian-Triassic boundary on a shallow carbonate platform in western Zhejiang, South China

The Huangzhishan section, 40 km from the well-known Meishan section, Zhejiang Province, South China, records a carbonate–siliciclastic Permian/Triassic (P/Tr) boundary succession. The P/Tr boundary sequences in both sections correlate well with one another, although the succession is much thicker at Huangzhishan than its equivalent at Meishan. The P/Tr transition is constrained by the Neogondolella yini, N. meishanensis and Hindeodus parvus conodont zones. Of these, the boundary between the first two zones marks the end-Permian mass extinction horizon. The base of H. parvus Zone defines the P/Tr boundary. The P/Tr mass extinction event is also indicated by a dramatic negative shift of the δ13Ccarb profile. This ecological crisis was facilitated by an abrupt environmental devastation indicated by an anoxic event. At Huangzhishan benthic habitats varied from open, oxygenated, to anoxic, to dysoxic-oxygenated and to dysoxic-anoxic conditions throughout the latest Changhsingian to early Griesbachian. Biotic turnover across the P/Tr boundary suggests the P/Tr mass extinction may have included two episodes in Huangzhishan. The first, perhaps major, episode occurs at the base of N. meishanensis Zone, corresponding to the event recorded at the base of Bed 25 in Meishan. The second coincides with the boundary between the H. parvus Zone and overlying Claraia–Ophiceras Assemblage zone, equivalent to the event recorded at the base of Bed 28 in Meishan. The first event did not see a significant decline in biodiversity, but is marked by an apparent loss of high-classification groups such as corals, sponges, macroalgae and most foraminifers. The Huangzhishan section records the most abundant and diverse surviving faunas among the P/Tr boundary sections around the world, with 54 species in 36 genera. However, they are severely affected by the Lilliput effect over the P/Tr extinction. Several fossil groups (bryozoans, blastoids and crinoids) temporarily survived the first episode of the P/Tr extinction and persisted into the earliest Triassic in Huangzhishan. Most survivors became extinct in the second episode of the P/Tr crisis. The Eumorphotis–Towapteria–Pteria bivalve fauna, widespread in shallow-water facies conodont-free P/Tr boundary sections in South China, occurs within the H. parvus Zone in Huangzhishan. This bivalve fauna therefore marks the P/Tr boundary in the conodont-barren P/Tr boundary sections. The top of this bivalve assemblage zone marks the second episode of the P/Tr crisis. Another slightly older bivalve fauna dominated by primitive forms of Claraia (e.g. C. bioni) marks the first/or main episode of the P/Tr extinction in the conodont-barren P/Tr boundary sections.

End-Permian Mass Extinction of Foraminifers in the Nanpanjiang Basin, South China

Abstract Newly obtained foraminifer faunas from the Permian-Triassic (P-Tr) transition at the Dajiang and Bianyang sections in the Nanpanjiang Basin, South China, comprise 61 species in 40 genera. They belong to the Palaeofusulina sinensis Zone, the youngest Permian foraminifer zone in South China. Quantitative analysis reveals that the last occurrences of more than a half of species (28/54) fall into a 60-cm-interval at the uppermost Changhsingian skeletal packstone unit and thus calibrate the end-Permian extinction to the skeletal packstone-calcimicrobial framestone boundary. About 93% (54/58) of species of the latest Permian assemblage became extinct in the P-Tr crisis. Four major foraminiferal groups, the Miliolida, Fusulinida, Lagenida, and Textulariina, have extinction rates up to 100%, 96%, 92%, and 50%, respectively, and thus experienced selective extinctions. Both Hemigordius longus and ?Globivalvulina bulloides temporarily survived the end-Permian extinction event and extended into the earliest Triassic but became extinct soon after. The post-extinction foraminifer assemblage is characterized by the presence of both disaster taxa and Lazarus taxa. Foraminifer distribution near the P-Tr boundary also reveals that the irregular contact surface at the uppermost Permian may be created by a massive submarine dissolution event, which may be coeval with the end-Permian mass extinction. A new species, Rectostipulina hexamerata, is described here.

Two episodes of foraminiferal extinction near the Permian–Triassic boundary at the Meishan section, South China

Stratigraphic distributions of foraminifer species from the Permian–Triassic (P/Tr) transition of the Meishan section, South China demonstrate two episodes of biotic mass extinction near the P/Tr boundary. The first episode is calibrated to the top of Bed 24 and is indicated by a loss of 49 out of 64 Changhsingian species (77%). The second phase is expressed by the disappearance of 32 out of 34 species (94%) recorded in Beds 25–27 and corresponds to the base of Bed 28. Only Nodosinelloides aequiampla survived into the early Griesbachian and another species, Glomospira regularis, rebounded in the late Griesbachian. The Lagenida and Textulariida lost 71% and 50% of species, respectively, in the first episode of the P/Tr extinction. In the Lagenida, only one taxon temporarily survived over the second crisis but became extinct soon after in Bed 29, while one newcomer occurred in the late Griesbachian. In the Textulariida, one Lazarus species rebounded in the late Griesbachian when two new forms rose. Both the Fusulinida and Miliolida suffered a great loss in the first extinction event, losing about 85% and 89% of the species, respectively. Their temporary survivors were wiped out in the second episode of the P/Tr crisis. The large, architecturally complex taxa suffered the first crisis much more severely than the small, simple tests. Selective extinction and rebound among the forms bearing various test walls probably indicate the different physiological reactions of various foraminifer groups to the defaunation events such as biocalcification crisis, hypercapnia, elevated CO2 content and global warming that prevailed in the aftermath of the P/Tr mass extinction.

Survival brachiopod faunas of the end-Permian mass extinction from the southern Alps (Italy) and South China

Eight brachiopod species in seven genera are described from the Permian–Triassic boundary beds of South China and northern Italy. The brachiopods from northern Italy are described for the first time and include two new species: Orbicoelia dolomitensis Chen and Spirigerella ? teseroi Chen. The Permian affinity of these brachiopods and their stratigraphical position above the extinction horizon demonstrate that they are survivors from the end-Permian mass extinction. The surviving brachiopods from South China, which was located at the eastern margin of the Palaeo-Tethys Ocean, are considerably abundant and diverse and are dominated by geographically widespread generalist elements adapted to a wide variety of environments. They were mostly limited to the Upper Permian to lowest Griesbachian. In contrast, the survivors in northern Italy, which was situated at the western margin of the Palaeo-Tethys, comprise elements ranging from the Carboniferous to Permian or widespread Tethyan genera. These survivors did not occur in the pre-extinction western Tethyan oceans but migrated into this region after the end-Permian extinction event. Disaster taxon Lingula proliferated slightly earlier in western Tethyan oceans than in eastern Tethyan regions following the event. Survival brachiopods from both regions appear to have a generic affinity, although they do not share any species. Both South Chinese and Italian survival faunas support the view that the survival interval is the duration when survivors are dominated by geographically widespread generalist organisms adapted to a wide variety of ecological conditions.

Multidisciplinary high-resolution correlation of the Permian–Triassic boundary

Abstract Biostratigraphic correlation of the ten most important Permian–Triassic boundary sections throughout Tethys enables establishment of four conodont and ammonoid subdivisions within a stratigraphic interval, one to a few metres thick, representing less than 1 Ma. In ascending order, they are conodonts (Clarkina changxingensis–C. deflecta Zone; Hindeodus typicalis Interval; Isarcicella parva Zone and I. isarcica Zone) and ammonoids (Pseudotirolites–Pleuronodoceras Zone, lower Otoceras Zone, upper Otoceras Zone and Ophiceras Zone). Most of them can be traced to North America and the Arctic region. Carbon isotope investigations of 24 sections along Tethys and in Greenland and Spitzbergen confirm the consistency of δ13C negative excursions at the Permian–Triassic boundary, together with an inconsistent Ir anomaly. Eight sections show that in most cases there is a succession of: Ir anomaly (denoting the end-Permian catastrophic environment); δ13C excursion (biomass loss, extinction); P/T boundary (origination of newcomers; potentially capable of intercontinental correlation within that short time interval). There is an intercontinental sequence boundary at the top of the Permian, and a transgressive surface at the P/T boundary followed shortly by a maximum flooding surface. An intercontinental anoxia event accompanied the transgression. Three delineations of the mass extinction phases and three population explosions have been recognized and can be more or less correlated in South China and the Southern Alps. Radiometric dating of the volcanogenic boundary clays of Meishan, Shangsi and the main-stage Siberian Tunguss Traps give an almost identical age of 250 Ma, thus implying a synchronous interregional volcanic event. There are a few palaeomagnetic transforms within the PTB strata. Thus, multidisciplinary research of the P/T boundary strata allows subdivision of this short interval into more than ten intercontinentally correlatable parts. Each subdivision averages less than 100 ka in duration. This may be the highest resolution obtained so far in pre-Cretaceous rocks. High-frequency, Milankovitch-type cyclic deposits within the P/T boundary beds enable correlation of even higher resolution in the Lower Yangtze area. This high resolution is made possible because the P/T transition is a time of saltation and catastrophy in geological history. Causality of the aggregation of events merits further investigation.

Did the great dying of life take 700 k.y.? Evidence from global astronomical correlation of the Permian-Triassic boundary interval

The cause of the great Permian-Triassic (P-T) boundary mass extinctions remains unknown. A crucial step in identifying the cause involves a precise timing of the mass extinction interval (MEI) in order to reconstruct the pattern of biotic evolution and the chronologic record of potential triggers. Here we present an estimate of the P-T boundary MEI duration based on astronomical tuning of multiple cyclic sedimentary records. Magnetic susceptibility data from Shangsi, southern China, provide evidence for strong 405 k.y. orbital eccentricity forcing throughout the P-T boundary interval. Radioisotope dating combined with 405 k.y. tuning provides an absolute time scale through the P-T boundary interval at unprecedented high resolution. An estimated ∼700 k.y. duration for the MEI at Shangsi is supported by eccentricity tuned estimates of four other sections in China and Austria. In addition, at Shangsi, the onset of mass extinction occurred shortly following a coincidence of minima in the observed ∼1.5 m.y., 405 k.y., and ∼100 k.y. cycles. A change in the magnetic susceptibility response to astronomical forcing occurred just prior to the onset of extinction, with reduced 100-k.y.-scale cyclicity continuing into the Early Triassic for more than 2 m.y.

An ecologically mixed brachiopod fauna from Changhsingian deep‐water basin of South China: consequence of end‐Permian global warming

The Late Permian Shaiwa Group of the Ziyun area of Guizhou, South China is a deep-water facies succession characterized by deep-water assemblages of pelagic radiolarians, foraminifers, bivalves, ammonoids and brachiopods. Here we report 20 brachiopod species in 18 genera from the uppermost Shaiwa Group. This brachiopod fauna is latest Changhsingian in age and dominated by productides. The palaeoecologic and taphonomic analysis reveals that the brachiopod fauna is preserved in situ. The attachment modes and substratum preference demonstrate that the Shaiwa brachiopod fauna comprises admixed elements of deep-water and shallow-water assemblages. The presence of the shallow-water brachiopods in the Shaiwa faunas indicates the involuntary settlement of shallow-water brachiopods. The stressed ecologic pressure, triggered by warming surface waters, restricted ecospace and short food sources, may have forced some shallow-water elements to move to hospitable deep-water settings and others to modify their habiting behaviours and exploit new ecospace in deep-water environments. We infer that the end-Permian global warming and subsequent transgression event may have accounted for the stressed environmental pressure in the shallow-water communities prior to the end-Permian mass extinction.