A succession that includes the Permian–Triassic transition was penetrated in the David 1 Borehole (Israel), located on the Levant margin sector of the northwestern Gondwanan plate. This is a fully marine section with a complex depositional interplay of distal siliciclastic and ramp carbonate sediment. Foraminifera distribution, sedimentary microfacies, δ¹³C excursions and e-log (gamma-ray; resistivity) data were analyzed. The local P-T boundary is placed at the first appearance of Triassic taxa, but there is a 90 m interval of overlapping faunas where the Permian taxa are small species atypical of the underlying Permian strata, and some specimens are clearly reworked. Carbonate strata were deposited in mid- to outer-ramp environments under varying conditions of sea level, storm regime, and siliciclastic (mostly silty) influx. Sea level, tracked by facies shifts, follows a low-order cyclic pattern. Two higher orders of cyclicity are also present: a short-term oscillation in storm frequency in the local depositional basin and a high-order mode in which clastic supply alternates with clastic-free carbonates, interpreted as reflecting humid-arid climate shifts of a remote, continental source region. The last mode lies within the Milankovich band of frequencies. Negative δ¹³C excursions, glauconite, and pyrite-rich horizons indicate hypoxic or anoxic conditions and reflect perturbations of the global carbon system in the oceans during this time. Although lithification of the latest Permian carbonates in the transitional interval was suppressed, the state of preservation of the carbonate components is not indicative of deposition under conditions of oceanic acidification.

A new conodont biostratigraphic study is presented from a key section on the flanks of the Permian-Triassic Great Bank of Guizhou, an isolated carbonate platform from South China, that has recently provided much key data for understanding the nature of this mass extinction interval. Detailed investigation at Bianyang (Guizhou Province) has revealed ten conodont zones, in ascending order: Clarkina yini Zone; Hindeodus changxingensis Zone; Hindeodus parvus Zone; Sweetospathodus kummeli Zone; Neospathodus dieneri Zone; Neospathodus cristagalli Zone; Discretella discreta Zone; Pachycladina-Parachirognathus assemblage zone; Icriospathodus collinsoni Zone; Triassospathodus homeri Zone. This allowed the Permian-Triassic boundary (PTB) to be defined in the section based on the first occurrence of Hindeodus parvus. Furthermore, it is proposed that the first occurrence of Discretella discreta can be used as an auxiliary reference for defining the Induan-Olenekian boundary when Novispathodus waageni is absent both at Bianyang and elsewhere.

A complete marine uppermost Permian to Lower Triassic succession is well exposed at the Daxiakou section of the Three Gorges area, western Hubei Province, South China. A total of 12 conodont zones are recognized from the uppermost Changhsingian (upper Permian) to Olenekian (Lower Triassic). Of these, the Clarkina yini, Clarkina meishanensis, and Clarkina taylorae Zones characterize the uppermost Changhsingian, whereas the Hindeodus parvus, Isarcicella staeschei, Isarcicella isarcica, Neoclarkina krystyni, Neoclarkina discreta, Sweetospathodus kummeli, and Neospathodus dieneri Zones define the Induan. Early Olenekian conodonts are assignable to the Novispathodus waageni and Nv. pingdingshanensis Zones. Conodont zones across the Permian-Triassic boundary (PTB) beds at Daxiakou correlate well with those established from the Meishan section, the Global Stratotype Section and Point (GSSP) for the PTB. The PTB is placed at the base of Bed 11c at Daxiakou. The Ns. dieneri M1, Ns. dieneri M2, and Ns. dieneri M3 subzones are distinguished from the Ns. dieneri Zone. Both Nv. waageni eowaageni and Nv. waageni waageni subzones are also recognized within the Nv. waageni Zone. The first occurrence of Nv. waageni eowaageni is an ideal marker defining the Induan–Olenekian boundary (IOB), which is calibrated to the base of Bed 86a at Daxiakou and is clearly beneath the ammonoid Flemingites-Euflemingites Zone.

Exceptionally preserved carbonate reticulated ridge structures are documented from the lower Middle Triassic Guanling Formation of the Luoping area, eastern Yunnan Province, southwestern China. Macrostructures suggest these reticulated ridge structures are morphologically similar to the growth-related structures in ancient and modern microbial mats. Other such features as minute load structures and pyrite crystals beneath the reticulated layers on bedding surfaces are overlain by a black carbonaceous shale layer. Clay minerals in the reticulated layers are oriented parallel to bedding at the top, and they usually form wavy laminae. These characteristics indicate that these carbonate reticulated ridge structures share a similar microstructure to their siliciclastic analogs, and are also comparable with that of wrinkle structures. SEM imaging shows that many tiny objects—coccoid spheres, rod-like structures and filamentous fibrils—are distinct within those ultra-thin, wavy laminae, suggesting similar accretion and growth models to modern microbial mats. Accordingly, the Luoping reticulated ridge structures are of biogenic origin. These microbial mats are associated with the early Middle Triassic Luoping Biota and they are thought to have played a crucial role in the preservation of the fossils through sealing and microbial coats. An SEM-EDS analysis on fossil fragments and their surrounding matrix reveals that microbial mats also played an important role in the phosphatization of Luoping fossils.

The end-Permian mass extinction, the most severe biocrisis in Earth history, has been attributed to major flood basalt volcanism, but direct evidence of volcanic effects on contemporaneous marine biotas is scarce. In this study, we examined the relationship of two components of the microplankton community (acritarchs and radiolarians) to volcanic ash deposits in two deepwater sections from South China (Shangsi and Xinmin). In these sections, each eruptive event was recorded as a volcanic couplet consisting of a pale, 0.1 to 3.0-cm-thick bentonite (altered volcanic ash) overlain by a dark, 0.1- to 1.0-cm-thick, organic-rich mudstone layer. Acritarchs were found in peak abundance in the mudstone overlying each ash layer but were otherwise present only in low concentrations in the background sediment. In contrast, radiolarians were rare in the volcanic couplets but frequently abundant in the background intervals. The thickest volcanic ash layers in both sections are found immediately below and above the latest Permian mass extinction (LPME) horizon. At this level, radiolarians underwent a major regional extinction but acritarchs reached their peak abundance, confirming their role as a disaster taxon. Above the LPME, long-spined and small spherical acritarchs declined more rapidly than short-spined forms. The preference of the short-spined acritarchs for neritic inner-shelf facies may indicate that such areas served as biotic refugia during intervals of extreme environmental stress. We infer that volcanic eruptions during the Permian–Triassic transition had both positive effects (e.g., increased nutrient supply) and negative effects (e.g., metal toxicity, lowered seawater pH, increased turbidity) on marine microplankton communities, the importance of which varied both spatially and temporally.

The famous Permian-Triassic boundary section at Guryul Ravine in Kashmir shows repeated strong disturbances in the uppermost 3 m of the section below the main end-Permian mass extinction horizon. Two one-meter-thick disturbed beds, with convoluted bedding and fluid escape structures, are interpreted as seismites. Immediately above, three lenticular, fining-upward, bioclastic grainstone beds, interbedded with argillites, are interpreted as tsunamites. In these beds, hummocky cross-stratification and grading indicate deposition by waning irregular waves at a minimum water depth of 100 m based on physical processes and faunas. Bed grain sizes indicate that the waves needed to move even the coarse sand of the matrix, let alone associated large pebbles up to 20 cm in diameter, range from amplitudes of ∼40 m for wave periods of 10 s (the upper limit for storm waves) to amplitudes of ∼3 m for wave periods of 50 to 1000 s (typical of large open-ocean tsunamis). Fossil and sedimentary evidence suggests lengthy intervals between successive tsunami events, which, together with a lack of geochemical evidence for impact, favors terrestrial causes. Geochemical proxies show that the Guryul Ravine environment remained oxic or suboxic throughout the P–Tr transition, but that anoxia developed regionally at the time of the boundary crisis. This paper is the first to propose seismites and tsunamites at the P-Tr boundary, so the geographic extent of these deposits is unknown, although analogous deposits occur in many sections worldwide from published reports.

Variations in sponge form diversity, abundance, and spicule size provide a potential record of paleoenvironmental changes associated with the end-Permian biotic crisis. Changes in three common spicule forms (Oxea A, Oxea B, and Orthopentactines) were analyzed in uppermost Permian (Changhsingian) and lowermost Triassic (Induan) strata at two localities in South China. The deeper-water Dongpan section exhibits decreasing spicule size as well as a strong decline in spicule-form diversity prior to the end-Permian crisis. In contrast, the shallower-water Maanying section exhibits an increase in spicule size and a more limited loss of form diversity over the same interval. In both study sections, the end-Permian crisis was accompanied by a miniaturization stage marked by a rapid decline in average spicule sizes (by >50% for Oxea A and Oxea B). Paleoproductivity proxies suggest that the decline of sponges was related to a general collapse of marine productivity. The timing and intensity of the sponge biocrisis varied between the two sections, however, with an earlier onset of miniaturization and a complete disappearance of sponges prior to the Early Triassic at Dongpan, versus a later onset of miniaturization and survival of several sponge forms into the Early Triassic at Maanying. These differences are attributed to relatively less hostile conditions (e.g., less frequently or less intensely reducing) in shallower-water environments during the end-Permian crisis.