Combined U-series dating of cave pearls and mammal fossils: Constraint on the age of a late middle pleistocene Ailuropoda–Stegodon fauna from the Diaozhongyan Cave, Guangxi, South China

To extend the range of materials that can be used to provide chronological constraint in archaeological and palaeontological settings, we explore the use of cave pearls that form in shallow pools. Here, we present U-series dating results of cave pearls found in cave sediments with mammal fossils collected from systematic excavations at the Diaozhongyan Cave (“DZY”), located in Guangxi Zhuang Autonomous Region, southern China. Similar to soda straw stalactites, cave pearls can be transported after formation and subsequently incorporated into sediments. Thus, the U-series ages of the outermost layers of cave pearls are expected to be older than their host sediments and associated archaeological and paleontological materials. In conjunction with U-series dating of mammal teeth, which can provide a reliable minimum age, U-series ages of cave pearls can provide a maximum age limit of the deposits. Thus, dating of the mammal teeth and cave pearls from DZY reasonably constrains the first occurrence of the DZY Ailuropoda-Stegodon fauna to a period between 205.6 ± 1.4 ka and 231.0 ± 12.8 ka. These age constraints agree well with previous estimates for the time range of the late Middle Pleistocene Ailuropoda-Stegodon fauna in southern China. We propose that greater attention should be paid to cave pearls, which are commonly found in cave deposits that were laid down at least in part due to fluvial activity, and can be used for U-series dating to better constrain the age of the associated cave deposits.