Terrestrial paleoclimate changes recorded by Pleistocene red earth deposits at the Gaolingpo Paleolithic site, Bose Basin, South China

The Quaternary river sediments at Gaolingpo, Bose Basin, Guangxi Province contain stone hand adzes and microliths of Paleolithic and Neolithic ages, providing information about the effect of climatic and environmental changes on hominin and early modern human activities. Gaolingpo is a representative Paleolithic site in the Bose Basin, containing numerous stone artifacts of different ages in the red earth sediments. We examined the clay mineralogy and geochemistry of the Gaolingpo profile using X-ray diffractometry (XRD), diffuse reflectance spectroscopy (DRS), and X-ray fluorescence (XRF) spectroscopy with the goal of reconstructing paleoclimatic and environmental changes in the study area since the late Early Pleistocene. Within this soil profile, kaolinite and vermiculite increase and illite decreases gradually up section. The red earth sediments exhibit uniform chondrite-normalized rare earth element (REE) distribution patterns, which are similar to those of upper continental crust (UCC), post-Archean Australian shale (PAAS), loess and paleosol of the Chinese Loess Plateau (CLP), and Yangtze River deposits. These confirm that the Gaolingpo red earth sediments originated from fine materials of well-mixed weathered continental crust within the upper Pearl River drainage basin. The chemical index of alteration (CIA) of the Gaolingpo sediments is 86.4–92.1, indicating that the sediments have undergone intense chemical weathering. Based on changes in clay mineral contents and geochemical compositions through the profile, the paleoclimatic evolution of the Gaolingpo area since the late Early Pleistocene can be divided into two stages with four sub-stages: (1) a generally humid climate prevailed during stage I can be further divided in two sub-stages. Sub-stage Ia was temperate with an alternating dry and wet climate, while sub-stage Ib was a transition to a warmer temperate climate. (2) A subtropical humid climate prevailed during stage II and transitioned to a cooler climate in the later stage. In this episode, sub-stage IIa was the warmest and the most humid period since the late Early Pleistocene in Bose Basin, and Stage IIb was a transition to a relatively cooler subtropical climate. This climate pattern is compatible with the regional palynological record at Chongzuo, south Guangxi and is in general agreement with the δ18O records from cave stalagmites in southern China, but is inconsistent with the δ18O record at ODP Site 1148 in the northern part of the South China Sea, though the age constraints limit a precise correlation. This reflects the predominant influence of Qinghai-Tibetan Plateau uplift on East Asian climate since the late Early Pleistocene. The development of warm, humid, and only weakly fluctuating climate conditions in the Bose Basin was favorable for early hominin settlement.