Jun Shen

The Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) represents one of the significant rapid and severe global warming events of the Cenozoic and is marked by a major extinction of deep-sea benthic foraminifera. In contrast, the ecological response of shallow marine benthic communities remains poorly constrained, despite extensive documentation from pelagic records. Here, we present a high-resolution quantitative foraminiferal dataset from two adjacent outcrops beside the Global Stratotype Section and Point at El Dababiya area, Egypt, providing one of the most detailed reconstructions of continental-shelf ecosystem disruption across the PETM. A total of 86 foraminiferal were identified, comprising 53 benthic and 33 planktonic taxa. Integrated species-level abundance data, cluster analysis, and redox-sensitive indices document the rapid loss of 13 specialized benthic taxa, corresponding to ~24.5% of the assemblage. In contrast, planktonic foraminifera show limited collapse saddle the PETM boundary, with all recorded taxa persisting across the event. The benthic extinction coincides with a pronounced shift from stable, well-oxygenated bottom waters to reduced oxygen conditions. Anoxic episodes are first detected within the E1 biozone, followed by persistent dysoxic conditions throughout the E1 and E2 biozones. The magnitude and selectivity of benthic extinctions indicate that widespread seafloor deoxygenation, driven by expansion and shoaling of oxygen minimum zones, exceeded the ecological tolerance of benthic specialists. These results establish a coherent extinction signal linking shallow- and deep-marine environments at the PETM and reinforce the El Dababiya area as a critical analogue for assessing the vulnerability of benthic ecosystems to ongoing and future ocean deoxygenation.

The late Paleozoic ice age (LPIA) was the longest-lived glaciation of the Phanerozoic, and its demise marks Earth’s only recorded transition from an icehouse to a greenhouse state since the occurrence of vascular plants and complex terrestrial ecosystem. While global volcanism has been widely considered a key driver of carbon cycle during this period, limited high-resolution records have constrained our understanding. Here, we use high-resolution carbon isotope and mercury records from the North China Craton, spanning the late Gzhelian to early Kungurian stages, to evaluate the relationship between carbon cycle perturbation and volcanism. We identify two negative carbon isotope excursions during the late Gzhelian and early Asselian, both coinciding with climate warming. Our data reveal a variable relationship between carbon cycle disturbances and mercury records, suggesting volcanism was not the only trigger. Instead, they may result from the superimposition of multiple mechanisms, including tundra conditions, methane release, or orbitally-paced climate changes.

The Permian–Triassic Mass Extinction (PTME), the most severe crisis of the Phanerozoic, has been attributed to intense global warming triggered by Siberian Traps volcanism. However, it remains unclear why super-greenhouse conditions persisted for around five million years after the volcanic episode, with one possibility being that the slow recovery of plants limited carbon sequestration. Here we use fossil occurrences and lithological indicators of climate to reconstruct spatio-temporal maps of plant productivity changes through the PTME and employ climate-biogeochemical modelling to investigate the Early Triassic super-greenhouse. Our reconstructions show that terrestrial vegetation loss during the PTME, especially in tropical regions, resulted in an Earth system with low levels of organic carbon sequestration and restricted chemical weathering, resulting in prolonged high CO ₂ levels. These results support the idea that thresholds exist in the climate-carbon system whereby warming can be amplified by vegetation collapse.

The Permian-Triassic transition was marked by severe climatic and environmental disturbances, culminating in the largest mass extinction event since the Phanerozoic era. Volcanic activity, particularly the eruptions associated with the Siberian Traps Large Igneous Province (STLIP), is widely regarded as the primary driver of this ecological crisis. However, it is still unclear about the ecosystem effects by the weathering of the basalt, although the volatile effects by volcanic releasing had been well explored. This study focuses on the Suol section in the Siberian Basin to explore the causal relationship between basalt weathering and climatic-environmental evolution during this critical period, by metal geochemistry, sedimentology, and mineralogical analyses.Results show that the concentrations of nickel, copper, vanadium, scandium, cobalt, and other metals in sediments near the Permian-Triassic boundary align with the elemental composition of Siberian basalts, confirming that the primary source material originated from basaltic eruptions. Following the volcanic events, the weathering of exposed Siberian basalts continued to influence the metal cycling in the Suol section into the Early Triassic, which yielding higher temperature. Notably, mercury and carbon isotope records recovered swiftly to pre-eruption background levels during the Early Triassic, indicating that volatile components such as mercury and carbon had a short-term impact on the climate and environment. In contrast, the weathering of non-volatile components persisted, resulting in prolonged effects on the regional climate and ecosystem.These findings highlight a temporal disparity in the release and impact of volatile versus non-volatile components during Siberian volcanic activity. Volatile emissions significantly influenced short-term climatic and environmental conditions, whereas basalt weathering under extremely higher temperature conditions exerted a long-term influence on geochemical cycles and ecosystem dynamics.

The spatial-temporal climate and environmental effects triggered by the weathering of basaltic magmas after a large igneous province (LIP) eruption are not well known. Here, we present geochemical data from numerous sedimentary sites with a near-global distribution to explore the effects of juvenile basalt weathering of the low-latitude Emeishan large igneous province (E-LIP, ~260 Ma). These data show the weathering of basalt dominantly contributed to siliciclastic materials in proximal basins (> 6 × 106 km2) at a timescale of up to ten million years. Our data thus provide evidence that, besides the gases released during the eruption, release of (metal) elements via weathering of basalt at low latitudes plays a significant role in surface geochemical cycling. The release of these elements likely facilitated the flourishing of tropical wetland flora in southwestern China during the Late Permian, resulting in the widespread formation of coal seams. Moreover, increased erosion rates, sharply reduced Chemical Index of Alteration (CIA), and exponentially increased bulk accumulation rates suggest a shift in the weathering regime of basaltic landscapes under the extreme climate conditions of the Early Triassic. This shift, characterized by intensified physical weathering, enhanced erosion in source areas but limited sediment transport, potentially resulting in the rapid disappearance of basalt weathering records in southwestern China.

The Early Jurassic represents a critical interval in Earth’s history, characterized by significant ecosystem perturbations both on land and in oceans. Huge releases of greenhouse gas (e.g., CO2, CH4) by large scale of volcanic eruptions are generally assumed to cause significant increases in temperature during the Triassic-Jurassic transition (TJT) and Toarcian Oceanic Anoxic Event (T-OAE). However, terrestrial environmental responses to the climate perturbations on land, e.g., type and intensity of continental weathering, during these two hyperthermal events are still unclear. Here, we present a continuous lacustrine succession from the Chuxiong Basin in Yunnan Province, China, through the analysis of an approximately 1800 meter core. By integration of sedimentological, paleontological, geochemical, and astronomical data, we have established a chronology spanning about 21 million years from the Rhaetian (Late Triassic) to the Aalenian (late Early Jurassic), calibrated by the long eccentricity cycles. Distinct negative carbon isotope excursions and peaks in sedimentary Hg abundance, confirm significant volcanism during both the TJT and T-OAE. However, the Chemical Index of Alteration (CIA) and clay mineral data show opposing responses for the two events, indicating increasing and decreasing (or constant) chemical weathering intensity during TJT and T-OAE, respectively. Therefore, we proposed that these event-specific chemical weathering variations imply responses of volcanism-induced hydrological changes at different latitudes during these events.

The surface productivity variations are still unclear through the Ordovician-Silurian crisis, which is belong to one of the “Big Five” extinction. Here, we present barium (Ba) concentration and isotope data from organic matter-enriched anoxic siliceous sediments of various facies (X sites from proximal to distal regions) during the OST from South China. Our data show that both raw Ba and ratios of Ba to aluminum (Ba/Al) are higher than that in numerous ancient black shales and modern high productivity area, document elevated Ba accumulations during this interval. Besides, a larger gradient (~ 1 ‰) of Ba isotope (138Ba) gradient between the shallow-water to deep-water sites, additional support higher marine productivity was the reason of the higher Ba burial in these sediments. These data provide evidence that elevated organic carbon fluxes from the surface ocean (other than redox conditions) was likely the main control on accumulation of these organic matter-enriched sediments, and thus provide the sources of “shale gas” during this interval.

The South China Craton experienced large changes in climate, eustasy and environmental conditions during the Late Ordovician Hirnantian Ice Age, but their impact on the watermass architecture of the Yangtze Sea has not yet been thoroughly evaluated. Here, we reconstruct the salinity-redox structure of the Yangtze Sea based on five Upper Ordovician-Lower Silurian shale successions representing a lateral transect from a deep-water area of the Inner Yangtze Sea (IYS; Shuanghe section) across the shallow Hunan-Hubei Arch (Pengye, Jiaoye and Qiliao sections) to the relatively deep-water Outer Yangtze Sea (OYS; Wangjiawan Section). Carbon isotope (13Corg) profiles show that the Guanyinqiao Bed (recording the peak Hirnantian glaciation) thins and is less completely preserved at sites on the flanks of the Hunan-Hubei Arch than in deeper water areas to the SW and NE, reflecting bathymetric influences. Watermass salinities were mainly marine at Shuanghe and brackish at the other four study sites, with little variation among Interval I (pre-glaciation), Interval II (Hirnantian glaciation) and Interval III (post-glaciation). Redox proxies document mainly euxinia at Shuanghe and Wangjiawan and suboxia at the other sites during Interval I, with shifts towards more reducing (mostly euxinic) conditions at most sites during Intervals II and III, which shows that all the study sections were deep enough to remain below the redoxcline during the glacio-eustatic lowstand. Two features of the Shuanghe section mark it as being unusual: it alone exhibits fully marine salinities implying greater proximity to the open ocean than the other four sites, and it exhibits an especially large shift towards more reducing conditions during Interval III (i.e. the post-Hirnantian transgression), implying greater water depths. These features are difficult to reconcile with the standard palaeogeographical model for the Ordovician-Silurian South China Craton, which is characterized by a geographically enclosed and restricted IYS and a more open OYS, arguing instead for the SW end of the IYS to have been connected to the global ocean and the OYS to have been a restricted oceanic cul-de-sac. A review of sedimentological and facies data for the IYS region suggests that our re-interpretation of the Ordovician-Silurian palaeogeography of the South China Craton is viable, although further vetting of this hypothesis is needed.