Conference Agenda

Compared to fossil plant organs such as leaves, petrified wood constitutes 80% of the total biomass of plant remains and serves as a crucial resource for investigating flora characteristics and vegetation evolutionary history. The Mesozoic era is considered as a significant period for the diversification and radiation evolution of fossil wood in China. Early Cretaceous fossil woods demonstrate remarkable diversity across both northern and southern flora regions. Recent studies on permineralized plants in the North China Block have enhanced our understanding of Early Cretaceous plant community evolution. However, Cretaceous fossil wood occurrences remain exceptionally scarce in Shandong Province compared to other regions. This study documents the first occurrence of Pinuxylon and Xenoxylon fossil woods from the Early Cretaceous Yangjiazhuang Formation (Laiyang Group) in Shichang area, Rizhao City, Jiaolai Basin of Shandong Province. The Jiaolai Basin of China is the southernmost edge of the distribution of the northern Jehol Biota and an important area which bears both the northern and southern palaeogeographical fauna representative species. Our study of these specimens has enriched our understanding of the floral landscape in the transitional region between the north and south flora.

Coal seams deposited in the Hailar Basin in Inner Mongolia, China act as valuable archive of past floras, climates and environments of the Early Cretaceous. A total of 19 samples were collected from the #14 and #15 coal seams, including the interburden, of the Albian-aged Yimin Formation. The aim of the study was to develop a high-resolution reconstruction of floral changes within the 9.5 m thick #15 seam using palynology.

Osmundacean fern spores (Osmundacidites) are the most abundant components of the assemblage. The fern spores Cyathidites and Deltoidospora show a upseam decrease whereas bryophyte spores (Sphagnumsporites) increase. Gleicheniacean (Gleicheniidites) and anemiacean (Cicatricosisporites) fern spores are higher in abundance in the mudstone floor and seam partings, indicating an apparent low tolerance for the harsh acidic and anoxic conditions of the mire. Pollen derived from cupressacean conifers (Perinopollenites) increase in abundance upseam whereas pinacean pollen (Pinuspollenites) decreases. Araucarian pollen is only present in the lower part of the seam. Other conifer pollen that appears consistently include Podocarpidites and Sciatopityspollenites. No angiosperm pollen was observed. Freshwater algae are present in the mudstone and sandstone partings and interburden.

The changes in flora across the seam reflect changes in water availability. The basal part of the seam is affected by periodic flooding, whereas the conditions in the middle of the seam are more stable allowing the establishment of the woody vegetation. The uppermost part of the seam is a mixed flora of ferns, bryophytes, lycophytes and conifers preceding the termination of peat deposition by flooding.

Water is the foundation of life, with its dynamic process profoundly impacting topographic development, habitat types and species richness; while few studies have shown convincing correlations between hydrological features and biological evolution in deep time due to the lack of quantitative proxies. This study. Here, we use triple oxygen and clumped isotope measurements of lacustrine carbonate to provide first insights into the environmental relative humidity (RH) for the Early Cretaceous Jehol Biota, known for the earliest flowering plants, feathered dinosaurs, and early birds, yet reasons for its astonishing richness are unclear. The isotopic results suggest that the Jehol Biota flourished in a humid climate with an RH value of 0.82 (±0.03, 1σ), consistent with humidity-sensitive fossil evidence (RH > 0.65). Combined with carbonate formation temperatures of 6.5 to 13.9 ℃, which indicate elevations of 2.1 to 3.1 km, and regional stratigraphy suggesting the lakes occupied areas over 85,000 km², the habitat of the Jehol Biota is analogous toanalogous to that of modern biodiversity hotspots such as Shangri-La in the Hengduan Mountains or Páramos in the tropical Andes. In the Early Cretaceous, the destruction of North China Craton facilitated Pacific-derived moisture influx into inland regions, which shape the diverse habitat environment and provide abundant moisture for the flourishing of the Jehol biota.