Chronology of the Haobiru Formation in the Haobiru area of northern Alxa, Inner Mongolia and its geological implications

Due to the low level of stratigraphic study of the Haobiru area in northern Alxa, Inner Mongolia, the age of the Haobiru Formation is controversial, and this limits the further discussion on the sequence stratigraphy, sedimentary construction and tectonic evolution.The authors revealed that the LA-ICP-MS zircon U-Pb age of the Early Carboniferous Haobiru Formation from the Haobiru area is 270.3±2.2Ma, and the youngest peak age of detrital zircons is 279Ma, and hence the age should be reassigned to Early Permian Kungurian-Middle Permian Roadian. According to the regional lithological characteristics, stratigraphic contrast and comparison of zircon age spectra, the Haobiru Formation should be reassigned to Lower-Middle Permian Maihanhada Formation(P_1-2m)-Middle Permian Aqide Formation(P₂a). The age revision of the Haobiru Formation provides new evidence for the discussion on the Late Paleozoic sequence stratigraphy, sedimentary construction and tectonic evolution.