STUDY ON THE MIDDLE JURASSIC FLORA IN SOUTHERN TUQUAN BASIN, INNER MONGOLIA

A total of 26 species of 15 genera plant fossils have been discovered in Mangniuhai area, southern Tuquan Basin, mainly including Annelids (Noecalamites sp. and Equisetites sp.), Filicopsida (Todites goeppertianus, T. williamsoni, Cladophlebis argutula, C. hsiehiana and C. shansiensis), Coniferales (Pityospermum staratschini, P. nordenskioldi, Podozamites schenki and P. lanceolotus), Ginkgoales (Czekanowskia rigida, Ginkgo huttoni, Ginkgoites cf. sibiricus, G. sibiricus, G. cf. marginatus, G. lepidus, Vittifoliolum paucinerve, Phoenicopsis speciosa and Sphenobailra sp.), Cycadales (Nilssonia sinensis) and Gymnosperms seed (Carpolithus sp.). Among them the Filicopsida (26.9%) and Ginkgoales (38.5%) are dominant, with Coniferales accounting for 19.2%, a small number of Equisetales (7.7%), Cycadales (3.8%) and Gymnosperms (3.8%) as well. Combined with the previous discovery of Raphaelia diamensis in the area, it is revealed that the minable seam-bearing fine clastic rock assemblages have the characteristics of early Middle Jurassic, belonging to Wanbao Formation. Based on the fact that the plant assemblages mainly consist of Cladophlebis, Ginkgoales like Ginkgo, Ginkgoites and Sphenobailra, and Cycads Podozamites, together with the flora appearance in the entire Wanbao Formation at that time, as well as the features of coal seam and developed sedimentary iron, it is inferred that the study area was in a warm and humid paleoclimate environment then.