Palynological Assemblage In The Late Early Cretaceous From Sikouzi Section, Liupanshan Group, Central China And Its Implication To Paleoenvironment Change

The Cretaceous (ca. 145 Ma similar to 65 Ma) was characterized by remarkable greenhouse conditions which was more server than present greenhouse gas emissions. However, this special climate condition is mainly documented from marine records. The information derived from continental sediments including terrestrial vegetation is relatively scarce. Here, we report on a palynological study of 17 samples from the Lower Cretaceous Liupanshan Group of the Sikouzi Section (spanning 116 Ma similar to 103 Ma), Liupanshan Basin and analyzed for paleoclimate implications. The palynoflora is diverse, dominated by Classopollis (Cheirolepidiaceae), with abundant ferns and rare angiosperms. The dominant ferns are from Lygodiaceae and Schizaeaceae. The palynological data shows that the Early Cretaceous floras are derived from various settings, i.e., the Coniferales on high elevation mountains, Cheirolepidiaceae along low hills near lakes, ferns in marsh wetlands, and algae in fresh water lakes. The palynoflora indicates that the climate in the Liupanshan area is hot and dry, and the palaeogeography is characterized by complex and various outlook during the Early Cretaceous, furthermore, climate evolution revealed by the vegetation can be divided into two stages during this period. From 116 Ma to 112 Ma, the concentration of thermophilic and xerophilous species such as Cheirolepidiaceae and Schizaeaceae were relatively low, conifers increased significantly, and fern concentration remained steady. This ecosystem suggests a humid and cold climate during this period. From 112 Ma to 103 Ma, the concentration of Cheirolepidiaceae and Schizaeaceae was relatively high, and conifers decreased significantly. Compared to the upper stage, the total percentage of Lygodiaceae spores were relatively low. Vegetation change during this period may indicate an increased trend of a dry and hot environment in this region. The trend of climate change recorded by the pollen assemblages during this period coincide with global sea surface temperature fluctuation. Thus, climate change recorded by the palynological assemblage in the Sikouzi section correlates well with global climate change during the Early Cretaceous.