The redefinition of Xinmin Formation in Zhamuqin area of Horqin Right Wing Middle Banner of Inner Mongolia and its geological significance

The Xinmin Formation in Zhamuqin area of Horqin Right Wing Middle Banner of Inner Mongolia were redefined by Inner Mongolia 1:50000 regional survey of four sheets such as Guonaotewula. According to lithologic combination, Xinmin Formation is divided into two lithogic sections:intermediate-acid pyroclastic rock is dominated by a small amount of pyroclastic rocks formed in lower segment overlying Linxi Formation with angular unconformity, whereas the upper part is a thick and thin clastic assemblage, which contains Pinuspollenites, Abiespollenites, Perinopollenites and some other Early-Middle Jurassic micropaleontologic fossils, with no top observed. LA-ICP-MS zircon U-Pb ages are 162.1±1.3Ma and 154.4±2.3Ma, suggesting Middle Jurassic.