The Discovery Of Jehol Biota And Fossil Plants From Southeastern Jilin, China

Baishan Basin(Hunjiang Basin) is a small-scale NE continental sedimentary basin, which is located in Baishan City, southeastern Jilin Province. The strata are divided into three formations in ascending order: the Upper Jurassic Yingzuilazi Formation, the Upper Jurassic Linzitou Formation and the Upper Jurassic-Lower Cretaceous Shiren Formation. There still has not been systematic research on paleontology in this basin, except for some previous fossil lists.This paper is focused on the paleontological research of Yingzuilazi Formation. It indicates that abundant fossil animals and fossil plants are yielded in this formation. The fauna mainly includes Conchostraca, Ostracoda, Bivalve, Snails, Insects, Fish and Amphibians, etc. Eosestheria-Ephemeropsis trisetalis-Lycoptera(EEL), as the representative biological assemblage of Yingzuilazi Formation, is in accordance with the Jehol Biota from the Yixian Formation in northern Hebei and western Liaoning. The age of the Yingzuilazi Formation should be Early Cretaceous, rather than Late Jurassic. It is believed that Baishan City is easternmost distribution area of Jehol Biota in China, and the stratum bearing fossils is the Yingzuilazi Formation.In the Jehol Biota from Baishan Basin, fossil plants are also abundant, and most of them are compressions. In this thesis, detailed taxonomic studies have been finished based upon the morphology and epidermal structure. The flora is composed of 46 species of 27 genera, including Sphenopsida, Filicopsida, Cycadopsida, Ginkgopsida, Czekanowskiales, Coniferopsida, Gentopsida and fructus et semina. Filicopsida and Gymnosperms play the most important part in Yingzuilazi Flora. Analysis of the plant community shows that the flora should be consistent with that from the Early Cretaceous Yixian Formation in Beipiao, western Liaoning in time and space.Viewing from the perspective of palaeoecology, the biota from Baishan Basin represents an Early Cretaceous terrestrial ecosystem that includes five types of palaeolandscape. They are freshwater(Bivalve, Snails, Ostracoda, Insects, Amphibians and Fish), shoreside-wetland(Sphenopsida), lowland(Filicopsida and Cycadopsida), sloping-land(Ginkgopsida and Czekanowskiales) and upland(Coniferopsida). There occurred seasonal precipitation variations in Early Cretaceous Baishan Basin. It was warm and humid in rainy season, when vegetation, insects and other animals flourished. While, in dry season, only a small amount of xerophilous plants could survive. Based on the plant assemblage, this flora corresponds to that of the Early Cretaceous SiberianCanadian Region or Northern Floristic Province of China, representing an important part of floras in warm temperate-temperate zones.This is the first time to confirm that the Early Cretaceous Jehol Biota existed in the Yingzuilazi Formation, Baishan City, SE Jilin. It is the easternmost distribution of Jehol Biota in China. The research on Baishan Basin, the second locality of Jehol Biota, provides valuable information for reconstructing the terrestrial ecosystem and discussing the palaeoclimate, palaeogeography in Early Cretaceous Baishan Basin. It also contributes to understanding the living environment of the Jehol Biota, studying the topographical features, and analyzing the succession of biological communities.