Conference Agenda

The Cretaceous was a prolonged greenhouse period characterized by relatively cool early (Berriasian to Aptian) and late (Campanian to Maastrichtian) phases separated by the “Cretaceous super greenhouse” (Albian to Santonian). Extensive research has focused on the evolution of Cretaceous paleoclimate conditions; however, questions remain regarding the nature of extreme climate conditions during the Cretaceous (e.g., glacial and hyperthermal conditions). To address these questions, we employ updated, proxy-based global maps of mean annual temperature (MAT), warmest mean monthly temperature, and mean annual precipitation from nine Cretaceous time slices in order to 1) better constrain the occurrence of glacial conditions; 2) estimate maximum and minimum ice volumes and areas; and 3) describe the occurrence of excess mean annual and summer temperatures. Our preliminary analyses of proxy-based winter temperatures and three precipitation seasonality scenarios suggest that even during the coldest periods of the Cretaceous, high-latitude snowpack build-up was less than 1 meter water equivalent and no snow survived the melt season at elevations <2000 meters above sea level (masl). However, our results leave open the possibility that alpine glaciers could have accumulated at high latitudes on isolated peaks at minimum elevations ranging from 2000 masl during the Hauterivian-Barremian to 3500 masl during the Turonian. Additionally, our results suggest excess temperatures were commonplace during the summer months in the tropics during the middle Cretaceous supergreenhouse, and that MAT >35 °C may even have occurred in restricted areas. The strategies that plants employed to survive these high temperature conditions is a ripe field for future research.

The Tianjialou Formation of the Dasheng Group, situated within the Yishu Fault Zone in East China, exhibits the development of dolomite and gypsum, which serve as records of a notable warming event. The existing K-Ar isotope ages of the andesite in the Tianjialou Formation is 95 Ma, which constrain the depositional time of the Tianjialou Formation to the Cenomanian Stage during the Late Cretaceous, hinting that the warming event documented by the dolomite and gypsum may be associated with Oceanic Anoxic Event 2 (OAE2). Carbonate carbon-oxygen isotope and organic carbon isotope analyses were further conducted, revealing that, in contrast to carbonate carbon isotopes, organic carbon isotopes can be correlated with the carbon isotope curves related to OAE2, whereas the deviation in carbonate carbon isotopes is influenced by the degree of closure of inland salt lakes. Our research reveals that terrestrial geological events can be correlated with OAE2 through the perspective of concurrent significant warmth. The global warming associated with OAE2 exerts a more prominent impact on terrestrial systems, due to the lesser thermal buffering capacity of land in comparison to the ocean. Of course, organic carbon isotope comparison is essential.

The Oceanic Anoxic Event 2 (OAE 2) during the Cretaceous represents one of the most significant oceanic and climatic perturbations in the Phanerozoic. This event primarily manifested in deep marine environments, leaving distinct geochemical, isotopic, and biological signatures activity in surface-shallow marine systems. While increasing evidence has documented the terrestrial expression of OAE 2, including impacts on continental ecosystems, the critical zone, and sedimentary records, these terrestrial archives remain fragmentary and discontinuous.

A comprehensive study was conducted on the lower Maodian Formation within the Ganzhou Group, located in the Xingguo subbasin of the Ganzhou basin group in southern Jiangxi Province, South China. Approximately 200 samples were systematically collected from a 300-meter-thick interval for carbon isotope analysis.

Results show that δ¹³C values of pedogenic carbonates are -7.12‰ to -2.89‰, mainly -6‰to -3‰ (~95%). Those of organic matters from the same samples exhibit -27.48 ‰ to -18.67‰, mainly -25.0‰ to -20.0‰. Three carbon cycles of both inorganic and organic matters are recognized, in which Phase II has the high δ¹³C values of both organic and inorganic matters, probably representing the carbon cycle perturbation in the terrestrial ecosystem during the OAE 2.

Reconstructed pCO₂ range from 250–3,300 ppmV, with the majority 500–2,500 ppmV, 2–10 times pre-industrial level ~275 ppmV and exhibiting a three-phase pattern consistent with the observed carbon cycles. The elevated and stable pCO₂ during Phase II correlate with extreme climatic conditions associated with OAE 2, providing direct evidence for coupled pCO₂-climate dynamics during this event.

The Oceanic Anoxic Events (OAEs) caused by volcanic activity during the Cretaceous period, which was a super-greenhouse period, had a major impact on marine ecosystems. On the other hand, there has been limited research on the impact on terrestrial ecosystems (e.g. Heimhofer et al., 2018). In the present study, we analyzed biomarkers in the sediments deposited across the Cenomanian/Turonian boundary (CTB) from California, USA to reconstruct terrestrial ecosystem changes during environmental disturbance event.

We analyzed sedimentary rocks across the CTB in the Budden Canyon Formation, Great Valley Sequence (GVS), were collected from the North Fork Cottonwood Creek sections in northern California, USA. The OAE2 interval (1st build-up, Trough, 2nd build-up, Plateau, and Recovery phases) was determined by δ¹³C and osmium isotope stratigraphy (Vivier et al., 2015). For the biomarker analysis, the extractions of crashed sediments were fractionated using silica-gel column and analyzed by GC-MS.

The aromatic terpenoid-based angiosperm/gymnosperm index (ar-AGI) values fluctuated wildly in the early stages (1st build-up to 2nd build-up), and then stabilized in the middle stage (Plateau). The Higher Plant Parameter (HPP), which indicates the contribution of conifers, increased rapidly at the last stage (Recovery phase) and remained high after OAE2. These results suggest that the abrupt climate changes caused by OAE2 had a significant impact on the terrestrial ecosystem of the western North American continental margin at that time, and that it shifted to a different environment before and after the OAE2.

Palaeobotany has long provided estimates of terrestrial climate in deep time. Most quantitative estimates come from leaf physiognomy, with wood anatomy providing more qualitative data. An exceptional wood flora from the Upper Campanian Jose Creek Member, McRae Formation (76 to >72 ma), Western Interior of North America, provides both qualitative and quantitative evidence for megathermal (tropical) temperatures and minimal seasonality at ~40 degrees paleolatitude. The wood flora comprises abundant conifers, >38 species of dicots, and 5–8 types of palms. Over 90% of the dicot species and specimens representing three major groups of conifers, show the absence of growth rings, indicating low seasonality and above-freezing Cold Month Mean Temperature (CMMT). This is corroborated by diverse palms. For dicots, patterns of vessel diameter and density are most like those of modern tropical woods from moist to wet climates. Transfer functions based on a subset of 10 anatomical traits for dicots estimate Mean Annual Temperature (MAT) of 21–28°C, CMMT of 16–24°C, abundant precipitation, and no dry season. MAT estimates fall within the range of other palaeobotanical and geochemical proxies, while moisture estimates are compatible with Jose Creek paleosols. The Jose Creek climate is most comparable to that of moist to wet, submontane to lowland tropical forest using the Holdridge system of climate classification, comparable to Af, or perhaps warm Cfa climate, in the Koeppen system.

The Deccan Traps (DT) Large Igneous Province (LIP) erupted during the Cretaceous-Paleogene (K-Pg) boundary interval (67–65 Ma), fundamentally transforming the global terrestrial environment. However, mechanisms coupling volcanic gas emissions to hydroclimatic shifts remain poorly constrained. Here, we present the first continuous high-resolution terrestrial precipitation record from East Asia (Songliao Basin), reconstructed using paleosol organic carbon isotopes (δ¹³C_SOM) spanning the critical DT eruptive sequence. Our results reveal three hydrologic regimes: (1) an early humid phase (66.5–66.3 Ma) coinciding with CO₂-driven equatorial Pacific warming; (2) an abrupt arid shift (66.3–66.1 Ma) aligned with sulfur-rich eruptions and enhanced basalt weathering; and (3) a post-boundary return to humid conditions (65.9-65.7 Ma) linked to CO₂-induced amplification of land-sea thermal contrasts. Pre-boundary aridity—potentially driven by combined volcanic forcing (e.g., sulfur aerosols, weathering feedbacks)—may have exacerbated ecological pressures, while post-boundary warm-humid conditions provided a foothold for forest ecosystem recovery in mid-latitude regions, as evidenced from North America. This study establishes a terrestrial hydrological framework and advances our understanding of LIP-climate linkages during the biotic upheavals.