Conference Agenda

The IGCP 679 project (Cretaceous Earth Dynamics and Climate in Asia) is based on the Earth system sciences to explore the processes and mechanisms of the rapid change in climate and environment under greenhouse conditions during the Cretaceous and the evolutionary responses of biodiversity on land and in the oceans of the Asian continent. The project has played an important role in promoting geoscience communication among Asian countries, including some countries outside Asia. In the last year, our project has made exciting research results on Cretaceous palaeontology, sedimentology, palaeoecology and palaeoclimate. Micro-CL scanning analysis confirms that the middle Jehol biota pterosaur Haopterus gracilis is a sister-taxon of the Lebanese istiodactyliform Mimodactylus libanensis. A new large-sized Early Cretaceous pterosaur footprint Pteraichnus junggarensis from the Junggar Basin, China was produced by the large pterosaur Dsungaripterus weii. The first pterosaur species Nipponopterus mifunensis from Japan is a sister taxon to the Mongolian unnamed azhdarchid. The Aptian-Albain tree fern Acanthopteris (Dicksoniaceae) from North China, Siberia, Russia and the Inner Zone of Japan indicates a warm and humid tropical to subtropical climate. New rainforest insects were recovered from the mid-Cretaceous Kachin amber. Terrestrial records of two hyperthermal events from a Cretaceous-Paleogene transition sequence in southeastern China suggest different forcing mechanisms. Late Early Cretaceous atmospheric CO₂ reached 2132 ppm based on stomatal and isotopic analysis of Pseudotorellia from Mongolia. The first terrestrial response to the Early Cretaceous Weissert Event indicates that the anoxia and/or high TOC deposition in inland lakes were not inherent features.

Reconstructing the Cretaceous climate is important for understanding the Earth system dynamics under greenhouse conditions. However, compared to marine archives, paleoclimate records from continental basins are still limited, including those across the Asian region. This study investigates terrestrial paleoclimate across east Asia during the Early Cretaceous by analyzing whole-rock geochemistry of fine-grained mudstones from the regions including Mongolia (Gobi), China (Junggar, Heilongjiang, Liaoning, Shandong, Sichuan), northern Japan (Iwate) and northeastern Vietnam (Banhang). In addition, numerical simulations were performed using an atmosphere-ocean-vegetation coupled model, the MIROC4m-LPJ model, which simulates Aptian (120 Ma) climates under two orbital scenarios: present-day parameters (PI orbit) and parameters maximising Northern Hemisphere seasonality (Hot orbit). The reconstructed chemical weathering intensity based on the RW index tended to increase from high-latitude to low-latitude areas and exhibited higher values along coastal regions compared to lower values in inland areas. The spatial distribution of the RW index is consistent with the simulated surface temperature and precipitation patterns. Notably, the Sichuan Basin, which showed the most significant variability in weathering intensity, also showed the greatest differences in precipitation between the PI and Hot orbit simulations. The agreement between geochemical proxies and model results underscores the reliability of the RW index and demonstrates the utility of climate models in interpreting geological records. A more comprehensive spatio-temporal reconstruction of the Cretaceous Asian paleoclimate will be possible with additional data from diverse localities, highlighting the need for further chronostratigraphic and geochemical investigations.

U-Pb ages of detrital zircons from the Goheung Basin were analyzed to determine depositional ages and provenance. This Cretaceous non-marine basin at the southern Korean Peninsula margin borders the Gyeongsang Basin, but its evolution remains poorly understood. We separated detrital zircons from 12 samples (six sandstones and six boulders) and analyzed U-Pb isotopic compositions of 1419 zircon grains.

Results reveal zircon ages spanning from 3650 Ma to 80 Ma (Archean to Cretaceous). Lower strata contain primarily Paleoproterozoic and Jurassic zircons with youngest Early Cretaceous ages (130-120 Ma), while upper strata show mainly Cretaceous and Jurassic ages with youngest Late Cretaceous ages (90-80 Ma). These depositional ages align with previous studies using plant fossils and detrital zircons. The zircon age spectra indicate a provenance shift from the adjacent Yeongnam Massif to the southwestern Korean Peninsula, which experienced intense Late Cretaceous volcanic activity. This shift provides insights into the tectonic and paleogeographic evolution of southern Korea during this period, potentially clarifying the relationship between the Goheung and Gyeongsang basins.

The mid-Cretaceous (Albian–Turonian) interval was marked by major environmental changes on a global scale. These are documented in the sedimentary record by significant floral and faunal shifts, black shales and by perturbations of the carbon cycle. The latter are commonly recognized as positive or negative carbon isotope excursions (CIEs), commonly associated with oceanic anoxic events (OAEs). High-resolution carbon isotope records spanning this time interval have been established in the western Tethys and other regions around the world. Here we present new bio- and chemostratigraphic data of an uppermost Albian to lowermost Turonian record from the eastern Tethys (Qiangdong section, southern Tibet). A biostratigraphic study, based on calcareous nannofossils, provided relatively abundant, and moderately preserved calcareous nannofossils from the Albian – Turonian interval. The first occurrence of the calcareous nannofossil zonal marker species Corollithion kennedyi (UC1a, 100.5Ma) and Quadrum intermedium (UC5c, 94.1Ma) constrain the Albian/Cenomanian and Cenomanian/Turonian boundary in the Qiangdong section, respectively. A continuous δ¹³C_carb record provides a detailed chemostratigraphic framework, with a positive CIE (~1.5‰) near the Albian/Cenomanian boundary correlating with the latest Albian OAE 1d. While the δ¹³C_carb record robustly captures the OAE 1d excursion, the characteristic CIE associated with OAE 2 is less prominent, likely due to diagenetic overprinting. Our work provides a good reference for local and global comparisons.

The mass extinction at the Cretaceous-Paleogene (K-Pg) boundary was coincided with the Chicxulub event and occurred concurrently with Deccan traps eruptions in India. However, whether this extinction resulted from a single cause or multiple factors, and which mechanism played the dominant role, remains controversial. Previous studies identified the K-Pg boundary in the LK-1 core from the Jiaolai Basin at the depth of ~523 m. Our integrated palynological and geochemical analysis of the same core reveals about 10 m upper than the previous supposed boundary. Notably, several K-taxa (species that became extinct after the K-Pg boundary) persist in the uppermost pollen-bearing sample at 515.4 m, confirming a latest Cretaceous age and suggesting the boundary lies immediately above. High field strength elements (e.g., Zr, Hf), which remain immobile during diagenesis, effectively trace volcanic inputs as crypto-tephra in sediments. Similarly, mercury (Hg) anomalies serve as reliable proxies for Large Igneous Province eruptions. Our data reveal two distinct pulses of volcanism in the Jiaolai Basin. Following the second volcanic pulse (516.1–514.8 m), climatic cooling culminated in the complete collapse of terrestrial vegetation by 515.4 m. While iridium (Ir) concentrations showed no significant anomaly, a pronounced Ir/Al₂O₃ peak at 513.55 m likely reflects extraterrestrial input from the Chicxulub impact. Consequently, we propose the K-Pg boundary lies between 514.8 m and 513.55 m, most probably near 513.55 m. This implies terrestrial flora experienced major extinctions prior to the impact event, supporting a primary role for Deccan Traps volcanism in driving the mass extinction.

The Mid Cretaceous represents a typical greenhouse world period, characterized by the Oceanic Anoxic Event 2 (OAE2) and early origin and radiation of angiosperms. However, the middle Cretaceous climate, biota and OAE2 records are mainly obtained from marine strata, while these information from terrestrial strata is very limited. The middle Cretaceous non-marine strata of the Songliao Basin is well developed, with relatively abundant spore and pollen, which is very important for understanding the non-marine climate change, vegetation evolution of angiosperms and OAE2 during the middle Cretaceous. The International Continental Scientific Drilling Program (ICDP) borehole SK-3 of the SongliaoBasin, provided unique materials for understanding the middle Cretaceous non-marine climate change, evolution of angiosperm and OAE2. Three palynomorph assemblages, Leiotriletes-Schizaeoisporites-Osmundacidites, Inaperturopollenites-Cyathidites-Retitricolpites and Schizaeosporites-Quantonpollenites-Tricolpopollenites, are identified from the upper Denglouku Formation (K₁d⁴), first and second member of the Quantou Formation (K₂q¹⁺²), and third member of the Quantou Formation (K₂q³), respectively, ranging from Cenomanian to early Turonian. A high-precision palynomorphs analysis of the K₂q³ is carried out in detail to reveal the terrestrial OAE2 records. It is suggested that a hot and arid terrestrial climate with cold snap during the OAE2 interval of east Asia. The climate was much arider during OAE2 than the lower and upper layers. What’s more, OAE2 may accelerate the evolution of angiosperms.

Keywords: Mid Cretaceous, Songliao Basin, Oceanic Anoxic Event 2, palynomorphs, angiosperm, paleoclimate