The "Cretaceous Greenhouse World" refers to an episode of Earth history that lasted from about 110 to 90 million years ago and characterized by high atmospheric CO2 levels (estimated to be 3-8 times pre-industrial CO2 concentrations), general absence of polar ice caps, reduced temperature gradients from the Equator to the poles, and much warmer oceans (5-9°C in tropical latitudes) than today. This CO2 buildup resulted from intensive submarine volcanic activity, related to the breakup and drifting apart of the Earth's continents. This period also coincides with the establishment of the Beringian land bridge between eastern Asia and western North America, resulting in major faunal interchanges between these areas through the arctic region. During the mid-Cretaceous, both climatic and palaeogeographic factors therefore led to a complete reorganisation of the terrestrial ecosystems in the northern Hemisphere.
The aim of this research project is to study the evolution of the climate during the Cretaceous in NE China and the impact of the mid-Cretaceous climatic ("Cretaceous Greenhouse world") and palaeogeographic (establishment of the Beringian land bridge between eastern Asia and western North-America) changes on the evolution of terrestrial ecosystems through the study of three formations: the Jehol Group in western Liaoning Province (~ - 140 to - 110 My), the Quantou Formation in Jilin Province (~ - 110 to 90 My), and the Yuliangze Formation in Heilongjiang Province (~ -70 to - 65 My). These three formations have already yielded exceptionally abundant and diversified palaeofloras and palaeofaunas. Moreover, they cover, from a stratigraphical point of view, an important part of the Cretaceous and are located not far from the Beringian land bridge that connected Asia with western North America. NE Asia is therefore the ideal place to study the impact of climatic and palaeogeographic changes on the biodiversity of terrestrial ecosystems during the Cretaceous in Eurasia.