Cosmogenic Nuclide Burial Dating Of Early Pleistocene Hominin Sites In Southern China

The establishment of a robust chronological framework for Early Pleistocene hominin sites in East Asia is very important in the study of early human evolution and migration.However,there is a numerical age‘blank period'from the lower boundary of Quaternary??2.6 Ma?to the upper dating limit of uranium series dating method??600 ka?in China's Quaternary researches due to inactivity of contemporary volcanoes,severely hindering the development of related disciplines.The age of most early Pleistocene hominin sites can only be obtained by relative dating methods such as magnetostratigraphy and biostratigraphy.In northern China,widely distributed loess provides abundant materials for paleomagnetic dating,and the chronological sequence of loess-paleosol has been fully studied,and the age of most early hominin sites has been well defined.However,in southern China,many sites were discovered in caves or fluvial sediment,where there are no suitable materials for magnetostratigraphy.Due to the long-term hot/wet climate and intense chemical weathering,the sites in red earth generally lack materials for radioactive dating and fossils for biostratigraphy.In some reticulated red clay,the natural remanent magnetization is masked by the chemical remanent magnetization,leading to inaccurate results of magnetostratigraphic study.Many early Pleistocene human sites in southern China still lack reliable chronological support.²⁶Al/¹⁰Be burial dating is a relatively new dating technique.By analyzing the ratio of the two nuclides in quartz material,this method can provide age constraint for burial events in the past 0.3–5.0 Ma.For simple burial dating,its reliability is controlled by the validity of several prerequisites.This method is limited to fluvial,cave deposits with a thickness of overburden no less than 10 m.The development of an isochron method for²⁶Al/¹⁰Be burial dating greatly expanded the range of sites suitable for dating and improved the age reliability.This improvement makes isochron burial dating a valuable method to construct the chronology of various sedimentary deposits.This method fills up the blind spots of the previous dating methods,thus can be used to solve the chronology of the Early Pleistocene hominin sites in China.In this study,three typical Early Pleistocene hominin sites in southern red earth were chosen to study by ²⁶Al/¹⁰Be burial dating.The chronological framework of early human migration and evolution,as well as the time and paleoclimatic significance of the widespread accumulation of red clay in southern China are further clarified.The Chenshan?CS?Paleolithic Site in Anhui Province and the Gaolingpo?GLP?Site in Bose Basin are located on the river terraces underlying the reticulated red clay.They are two typical sites discovered in the red clay in southern China.In CS site,there are cultural sequences from Paleolithic to Neolithic discovered in the reticulated red clay.So far,only the paleomagnetic age was extrapolated to get the bottom age of the site,lacking the support of radioisotope age.In this study,the simple burial dating of three sand samples at the bottom of this site was applied.The result shows an age of 1.17±0.16 Ma.Our age is consistent with the previous paleomagnetic results.Since our age of this site only represents the minimum age at which the red soil begins to accumulate,it's possible that the beginning of the cultural sequence of the site may be earlier.The GLP site is an important archaeological site in the fourth terrace of the Youjiang River in Bose Basin.A sequence of cultures in different period from the bottom to the top was discovered during the latest excavation.Meanwhile,the bifacial handaxe found in the reticulated red clay in this area changed our understanding of the Acheulian technology in East Asia.The simple burial dating result of the gravel layer at the bottom of the GLP site indicates that the minimum deposition age of the reticulated red clay is1.37±0.12 Ma.This age also represents the beginning of the Paleolithic culture in this site,which is earlier than the bifacial handaxe culture in Bose Basin.The red clay accumulation age of this two sites?CS and GLP?shows that the reticulated red clay in southern China began to accumulate at least at 1.4–1.2 Ma,which is older than previous views based on magnetostratigraphy.The Yuanmou Homo erectus site is generally considered to be one of the oldest hominin sites in southern China.The chronology of this site has been repeatedly investigated using magnetostratigraphy since its first discovery in the 1960s.However,there are multiple interpretations of the magnetostratigraphy due to the complexity of the sedimentary environment,resulting in a one-million-year age discrepancy by different studies.Because Yuanmou's age has yet to be verified radio-isotopically,we apply isochron ²⁶Al/¹⁰Be burial dating to constrain the existing magnetostratigraphy.Six samples from a gravel bed 38 m above the fossil layer were collected,yielding an age of1.54±0.06?0.11?Ma.Based on the estimated sedimentation rate,we interpolate an age of 1.72±0.03 Ma for the fossil layer.Although the exact layer in which the incisors were found at Yuanmou is unclear,its age can be confined to between 1.78–1.59 My by stratigraphy.This result is consistent with the most recent paleomagnetic stratigraphy of1.7 Ma for the Yuanmou H.erectus fossils.Combined with other recent chronological studies of paleoanthropological sites across Asia,this study supports a model for earlier hominin dispersals out of Africa.Over the past decades,²⁶Al/¹⁰Be burial dating has produced exciting achievements in archaeology,anthropology and geomorphology.With the major advancements in methodology,burial dating is expected to make more important contributions to these fields.