Mesozoic

Lithium isotope constraints on Permian–Triassic continental weathering and multi-proxy comparison

2026-06-04T10:54:03+12:00

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 beetle fauna of mid-Cretaceous Kachin amber: a systematic synthesis

2026-06-23T13:27:49+12:00

Kachin amber from northern Myanmar, dated to the mid-Cretaceous (ca. 99 Ma), is an exceptional fossil Lagerstätte that preserves ancient terrestrial ecosystems in vivid, three-dimensional detail. Over the past decade, numerous beetle taxa representing a wide range of extant and extinct lineages have been described from this deposit, substantially expanding our knowledge of Cretaceous coleopteran diversity. Despite these discoveries, a comprehensive synthesis of the beetle fauna from Kachin amber remains unavailable. Here, we review the current record of beetles from Kachin amber and summarize the taxonomic composition of the fauna across major coleopteran groups. Particular attention is paid to fossils of evolutionary or ecological significance. This synthesis provides an updated overview of the diversity and systematic composition of the Kachin amber beetle fauna and highlights the importance of the deposit for future studies of beetle evolution and Cretaceous terrestrial ecosystems.

Early Cretaceous amber from the Heibaoshan-Handaqi Basin, Heilongjiang Province, Northeast China

2026-06-23T13:28:38+12:00

Cretaceous amber plays a crucial role in understanding the evolution of Late Mesozoic biotas and changes in palaeoclimates and palaeoenvironments. This paper reports amber, insects and plant fossils from the Lower Cretaceous Jiufengshan Formation in Heihe City, Heilongjiang Province, Northeast China, and presents the Fourier-transform infrared (FT-IR) spectroscopic characteristics of the amber. The Heihe amber occurs predominantly as irregular blocky pieces and layered forms, and is mainly preserved in coal seams. In addition, insect fossils belonging to multiple groups, including Coleoptera, Orthoptera, Hemiptera, Blattodea and Trichoptera (caddis cases), have been found in black shales near the amber-bearing horizons, further enriching the palaeobiological assemblage of the region. This discovery provides important empirical evidence for investigating the biotic characteristics and stratigraphic correlation of northern China during the late Mesozoic.

**A new species of Proptychopterina (Diptera: Nematocera: Ptychopteridae) from the Middle Jurassic of the Jiyuan Basin, China**

2026-06-23T13:29:44+12:00

A new species of the dipteran family Ptychopteridae, Proptychopterina jiyuanensis sp. nov., is described based on a nearly complete forewing from the Middle Jurassic Yangshuzhuang Formation in the Jiyuan Basin of central China. This new discovery represents the second fossil record of Ptychopteridae from China. We also revise the morphological features of Proptychopterina opinata Lin & Lukashevich, 2006, a species previously documented from the Middle Jurassic Daohugou Beds of Inner Mongolia, north-eastern China. The present discovery further supports biostratigraphic correlation between the Daohugou and Jiyuan fossil localities.