Conference Agenda

Calcareous nannoplankton are among the most effective tools for paleoenvironmental reconstructions, thanks to their wide geographic distribution and high sensitivity to environmental changes. Parameters such as coccolith size, relative abundance, and assemblage diversity provide key insights into past ocean conditions, including surface-water temperature and fertility, and ocean chemistry.

Beyond local paleoecological reconstructions, calcareous nannoplankton have been widely used to investigate ocean-atmosphere dynamics at both regional and global scales, and across a range of temporal resolutions, from short-term events to long-term trends. The Cretaceous period, marked by major climatic and oceanographic changes, offers numerous examples of large-scale environmental perturbations, many of which are associated with intense Large Igneous Province activity. In particular, Oceanic Anoxic Events (OAEs), often linked to episodes of massive volcanism, represent key case studies for understanding plankton community responses during times of environmental stress.

This presentation will provide an overview of the paleoecological responses of calcareous nannoplankton to environmental perturbations during the Cretaceous, considering both specific OAEs and long-term background intervals (non-OAE periods). The aim is to assess how calcareous nannoplankton responded to environmental stress, whether and under what conditions they were resilient, and which thresholds may have triggered disruptions in ecological equilibrium. Potential recurring patterns among similar events, the timing and pathways of recovery following peak perturbation phases, and the factors that influenced calcification in the past will be explored keeping an eye on what is observed in modern plankton systems, offering insights into the links between past crises and ongoing environmental change.

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.