In situ (splash-form) tektites from the Middle Pleistocene laterite deposits in Bose Basin, south China

The Australasian tektite strewn field (ATSF) is the most recent and largest confirmed tektite strewn field to date, representing a major extraterrestrial impact event (Australasian Tektite Event, AATE) around 0.8 Ma. Despite the fact that a considerable number of tektite locations have been discovered in this region, the majority lack a clear stratigraphic origin. Whether these tektites can serve as event-stratigraphic markers near the Early-Middle Pleistocene boundary has long been a topic of debate. The Bose (or Baise) Basin in Guangxi, southern China, is located at the northernmost edge of the ATSF and has perhaps received the greatest attention due to its association with the Paleolithic artifacts. In Bose, splash-form tektites are commonly preserved in the reticular mottled red clay layers of the fourth terrace (T4) of the Youjiang River, alongside Acheulean-like Paleolithic stone tools. Based on the age of these tektites, researchers have suggested that the earliest handaxe-making in eastern Asia could date back to 0.8 Ma. Most of the tektites found in Southeast Asia, the area of the ATSF with the highest rate of tektite distribution, are found in association with Neolithic or even more recent artifact deposits. For this reason, scholars have vigorously debated whether the age of the Bose tektite is representative of the actual age of the Acheulean stone tools from there. Here, we report on 155 splash-form tektites, unearthed during archaeological excavations at the Nanbanshan locality of the Damei site in the Bose Basin. Incidentally, this is the first time that such a dense layer of in situ tektites have been discovered in Quaternary sediments. Our study indicates that this tektite layer occurs primarily below the Brunhes/Matuyama boundary in the flood-plain sediments, showing clear stratigraphic significance. The surface morphology of these tektites, the particle-size analysis and the soil micromorphological analysis of the associated sediments together indicate that these tektites from T4 of the Bose Basin are from clear in situ provenance. Our analyses reveal a range of morphological types of tektites in the northernmost margin of the ATSF. This study further strengthens the view that the production of the Acheulean-like stone artifacts, likely made by Homo erectus in Southeast Asia including southern China, occurred simultaneously with the most recent tektite falling event.