Discovery of Sporopollen Fossils of Jurassic Hongqi Formation in Xilinhot,Inner Mongolia,and Its Paleoclimate Significance

Abundant sporopollen fossils,including 26 genera and 39 species are found for the first time in the lower part of Jurassic Hongqi Formation in Xilinhot Coal field,Inner Mongolia.According to the characteristics and stratigraphic distribution of the sporopollen fossils,the age of Dictyophyllidites-Cyathidites-Classopollis assemblage belongs to the late of Early Jurassic.The palynological assemblage is correspondent to that of some regions in North China,Northeast China and Northwest China.Furthermore,based on the analysis of composition of sporopollen,it is suggested that the ancient plants are mainly cheirolepidiaceae,conifers,cycad,cyatheaceae,dipteridaceae during Early Jurassic.Paleovegetation types are coniferous-leaved and broad-leaved mixed forests,indicating that the paleoclimate was from being semi-dry to semi-humid subtropical environment during this period.