| 论文摘要 |
The Linxia Basin along the northeastern margin of the Tibetan Plateau has drawn enormous attention due to its rich mammalian fossils and great potential for exploring regional tectonics, paleoenvironmental history, and bio-evolution. However, the geochronology of the sedimentary sequences is in great dispute owing to uncertain lithostratigraphic correlation and poorly calibrated magnetostratigraphy. From 2017 to 2021, we carried out lithostratigraphic correlation of the strata from the southern part of the basin, which is rich in fossils, to the Maogou section in the central basin, and established a solid intra-basinal lithostratigraphic framework with accurate fossil locations. Then, high-resolution magnetostratigraphic investigations were performed on the Maogou section, which comprises, from oldest to youngest, the Jiaozigou, Shangzhuang, Dongxiang, Liushu/Hujialiang, and “Liushu” formations. Magnetostratigraphic results show that the Maogou sedimentary sequence (from Jiaozigou to Liushu/Hujialiang formations) spans from chron C10r to chron C5r.2n, yielding an age of 29–11.6 Ma, with constraints from four mammalian assemblage levels. The revised magnetostratigraphy indicates that the Jiaozigou Formation corresponds to chrons C6Cn.3n–C10r (～23–29 Ma), with Paraceratherium fauna from the lower Jiaozigou Formation being determined as ～29 Ma, and that the Hujialiang Formation, containing Platybelodon fauna, corresponds to chrons C5r.2n–C5Ar.2r (～11.6–12.8 Ma). The revised magnetostratigraphy of the Maogou section has significantly refined the chronology of the Linxia Basin sedimentary sequences and its associated mammalian evolution, tectonism, and climate change in Central Asia. |
