Hua Zhang

The Permian-Triassic transition (∼252 million years ago) marks the most severe mass extinction in Earth’s history, followed by a protracted interval of environmental instability and delayed biological recovery. Although elevated atmospheric carbon dioxide (CO ₂ ) from extensive volcanism is widely invoked, the role of continental weathering feedbacks in regulating global climate has not been effectively constrained. Here, we present high-resolution lithium isotope records from marine carbonates and terrestrial deposits through the Permian-Triassic transition. Combined with an Earth-system model, our data reveal notable decreases in global continental weatherability following the end-Permian mass extinction, inferred to associations with widespread deforestation (extinction of deep-rooted plants) and the collapse of terrestrial ecosystem. This diminished weathering response to volcanic carbon emissions likely contributed to prolonged high atmospheric CO ₂ and global temperature during the Early Triassic. The sustained greenhouse conditions, in turn, inhibited contemporaneous marine and terrestrial ecosystem recoveries. Our findings highlight the importance of terrestrial ecosystem in modulating global carbon cycle stability, and its effects on Earth’s habitability.

The Permian–Triassic transition (P–Tr, ca. 251.9 Ma) witnessed the most severe mass extinction of the Phanerozoic, triggered by intense volcanic activity and associated environmental catastrophes. Continental silicate weathering is central to understanding both the mechanisms of the extinction and the prolonged Early Triassic warmth, yet changes in its intensity and flux remain controversial. Lithium (Li) isotopes (δ7Li), a promising tracer of silicate weathering, have increasingly been applied to the P–Tr transition. However, δ7Li records from different sedimentary archives (marine carbonates, shales, cherts, and terrestrial clastic rocks) show stark discrepancies: some indicate rapid enhancement of chemical weathering, others invoke marine reverse weathering as the dominant control, and terrestrial evidence points to intensified physical erosion but suppressed chemical weathering. These contradictions arise because the marine δ7Li signal integrates multiple processes—continental weathering input, reverse weathering, and changes in the size of the oceanic Li reservoir—that cannot be disentangled by a single proxy. This review synthesises δ7Li records with the Chemical Index of Alteration (CIA), strontium (Sr) isotopes, osmium (Os) isotopes, and magnesium (Mg) isotopes across the P–Tr transition. We demonstrate a pronounced “intensity‑flux decoupling” in continental weathering, where traditional weathering indices (CIA) and terrestrial δ7Li indicate that chemical weathering intensity (measured as the chemical depletion fraction, W/D) did not increase globally and may have even decreased, while radiogenic Sr and Os isotopes record a sharp rise in the total terrigenous material flux. This paradox is reconciled with a regime of rapid physical erosion with limited chemical leaching, driven by vegetation collapse and a shortened hydrological cycle. Meanwhile, extreme Early Triassic marine δ7Li anomalies are largely controlled by enhanced reverse weathering and a likely reduced marine Li reservoir. A multi-proxy deconvolution framework thus allows a three-dimensional separation of weathering intensity, flux, and internal oceanic processes, offering a unified way to resolve current controversies. Future priorities include quantitative calibration of archive effects, systematic mapping of spatial heterogeneity, and numerical modelling of the marine Li cycle to advance quantitative understanding of Earth system crises in deep time.

The moderate impact of rapid global warming on oceanic redox and biodiversity during the Paleocene-Eocene thermal maximum (PETM; ~55.9 Ma) contrasts with other hyperthermal events in Earth’s history, and remains mostly unexplained. Here, we use lithium isotope (δ⁷Li) proxy and Earth system model simulations to reconstruct continental weathering regimes during the PETM. Negative δ⁷Li excursions of 3–4‰ in shallow-marine carbonates suggests globally increased erosion rates and decreased weathering intensities. Further, large negative δ⁷Li excursions of 4–5‰ in siliciclastic successions reflect enhanced accumulation of detrital clays exhumed from previous clay-rich sedimentary rocks, rather than those from weathering of igneous rocks. Changes in continental weathering regimes and associated flux of nutrients to oceans provide an explanation to the muted increase in oceanic anoxia and overall biodiversity loss during the PETM. The concomitant increases in physical erosion and clay delivery also enhanced organic carbon burial efficiency, permitting rapid return of global climate to pre-perturbation state.

Carbonate rocks are widely used for paleomagnetic reconstructions of continental block rifting and geodynamic evolution. However, the detection of remagnetization in carbonate rocks is challenging. Uncertainty of remagnetization timing hinders our ability to understand the geomagnetic behavior during critical Phanerozoic transitions, such as the period across the Middle‐Permian Guadalupian to Late‐Permian Lopingian boundary (GLB). To test whether primary magnetization is preserved, we conducted paleomagnetic, calcite U‐Pb geochronological and mineralogical studies at the Penglaitan section in southern China. The rock‐magnetic results indicate that magnetite, maghemite and rare hematite are dominant remanence carriers. Calcite U‐Pb ages of approximately 126 Ma, 223 Ma and 251 Ma, respectively, are consistent with the timing of three remanent magnetizations (RM1, RM2, RM3). This indicates that calcite U‐Pb dating can provide robust support to constrain the age magnetizations. The consistency indicates that RM3 was acquired during the limestone deposition, whereas component RM1 and RM2 were due to early Cretaceous and late‐Triassic remagnetization, respectively. In addition, the primary component RM3 was isolated from tuffaceous limestone and yielded a mean direction of D _s /I _s = 195.3°/+5.6° (α _95s = 5.3°, k _s = 22.8, n = 34) after tilt‐correction. It defined a reversed magnetozone from the top of conodont Jinogondolella granti Zone to the lower part of the Clarkina dukouensis Zone, straddling the GLB. The calcite U‐Pb dating and paleomagnetic results provide new insights into Mesozoic multi‐remagnetization in the South China Block and refine the GLB positioned in a reversed magnetozone.

The end-Permian mass extinction was the most severe ecological event during the Phanerozoic and has long been presumed contemporaneous across terrestrial and marine realms with global environmental deterioration triggered by the Siberian Traps Large Igneous Province. We present high-precision zircon U-Pb geochronology by the chemical abrasion–isotope dilution–thermal ionization mass spectrometry technique on tuffs from terrestrial to transitional coastal settings in Southwest China, which reveals a protracted collapse of the Cathaysian rainforest beginning after the onset of the end-Permian marine extinction. Integrated with high-resolution geochronology from coeval successions, our results suggest that the terrestrial extinction occurred diachronously with latitude, beginning at high latitudes during the late Changhsingian and progressing to the tropics by the early Induan, spanning a duration of nearly 1 million years. This latitudinal age gradient may have been related to variations in surface warming with more degraded environmental conditions at higher latitudes contributing to higher extinction rates.