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Progress in dating modern Homo sapiens sites in China
A580
Goldschmidt Conference Abstracts 2006
Progress in dating modern Homo sapiens sites in China
Quantification of silicate weathering in Chinese Loess Plateau
GUANJUN SHEN1, BIN GAO1, JIANXIN ZHAO2
XUEFEN SHENG1, WENBO RAO2
1
College of Geographical Sciences, Nanjing Normal University, Nanjing, Jiangsu 210097, PR China ([email protected]; [email protected]) 2 Radiogenic Isotope Laboratory, Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, QLD 4072, Australia ([email protected]) The origin of modern Homo sapiens has been the subject of an intensive debate between exponents of two competing hypotheses: ‘‘recent out of Africa’’ and multiregional origins. It is generally accepted that the hominid fossil and archaeological evidences from Africa, Europe and Mid-East support the former model, whilst those from East Asia are in line with the latter. The accurate dating of relevant finds is fundamental to addressing the above controversies. The reliability of U-series dates on pure and dense cave calcites has been well demonstrated.Mainly using this dating method, the chronologies of relevant hominid localities in southern China were reexamined in the past more than ten years. They include the sites of Liujiang, Laibin, Bailiandong and Tubo in Guangxi, Zhangkou and Xianren caves in Yunnan and Lianhua cave in Jiangsu. The results show that modern humans were present in China at least 100 ka ago, much earlier than previously estimated, and that the so-called ‘‘temporal gap’’ of human presence in China between 40 and 100 ka is most probably merely an artifact caused by systematic errors of previous dating methods. In an attempt to search for earliest representatives of modern hominid and to better understand the model of recent human evolution in China, further chronological studies are currently under way. Southern China provides a promising ground for research works in this direction, as the region hosts numerous Late Pleistocene hominid sites in limestone caves, where cultural or fossiliferous deposits are often intercalated with speleothem formations. With robust temporal constraints, the hominid finds there may contribute significantly to elucidating the much-debated issues concerning the origin, dispersal and evolution of modern H. sapiens.
1
State Key Laboratory of Hydrology—Water Resources and Hydraulic Engineering, Hohai University, China 2 Research Academy of Hohai University, China Most authors considered that chemical weathering only resulted in carbonate dissolution but did not alter silicate minerals evidently in Chinese Loess Plateau (Chen et al., 1998; Liu et al., 2002). However, silicate weathering intensity in Chinese Loess Plateau is not quantified yet. In this study, 87Sr/86Sr ratios of acid-soluble and acid-insoluble fractions (0.5 M HOAc solution leaching) of eolian dust in the Lingtai section during the last 7 Ma are determined to quantify chemical weathering intensity. Results display that 87Sr/86Sr ratios range between 0.7104 and 0.7116 for acid-soluble fractions, and vary from 0.7182 to 0.7234 for acid-insoluble fractions. 87 Sr/86Sr ratios of acid-soluble fractions in the Lingtai section are originally controlled by marine carbonate widely spreading over North China and eolian silicate weathering. So, the relative contribution of Sr released from silicate fractions due to chemical weathering in the Lingtai section can be calculated with a twocomponent mixing equation. One endmember is the silicate fraction and the other is marine carbonate. Acid-soluble fractions are assumed to represent silicate fractions with variable 87Sr/86Sr ratios in the past 7 Ma. The mean Sr isotope ratio of marine carbonate is considered to be 0.708 during the Phanerozoic. The mixing equation is given as 87Sr/86SrAS = X 87Sr/86SrAI + (1 X) 87 Sr/86SrMC, where AS is the acid-soluble fraction, AI represents the silicate fraction, MC is marine carbonate, X is the relative contribution of silicate fractions, and (1 X) denotes the relative contribution of MC. Results show that whether the Quaternary loess or the Tertiary red clays, their acid-soluble fractions contain less than 30% Sr derived from chemical weathering of silicate fractions in the Lingtai section during the last 7 Ma, and reveal weak chemical weathering in Chinese Loess Plateau.
References Chen, J., Ji, J.F., Qiu, G., et al., 1998. Sci.China Ser. D) 41 (3), 235–241. Liu, L.W., Chen, J., Chen, Y., et al., 2002. Acta Pedol. Sin. 39 (1), 65–70.
References Shen, G.J., Wang, W., Wang, Q., Zhao, J.X., Collerson, K., Zhou, C.L., Tobias, P.V., 2002. U-series dating of Liujiang hominid site in Guangxi, southern China. J. Hum. Evol. 43, 817–829. Shen, G.J., Li, J.K., Ji, X.P., 2005. U-series dating of Zhangkou Cave in Yiliang, Yunnan Province: Evidence for human activities in China during 40 and 100 ka. Chin. Sci. Bull. 50, 355–359. doi:10.1016/j.gca.2006.06.1074
doi:10.1016/j.gca.2006.06.1075
Goldschmidt Conference Abstracts 2006
Progress in dating modern Homo sapiens sites in China
Quantification of silicate weathering in Chinese Loess Plateau
GUANJUN SHEN1, BIN GAO1, JIANXIN ZHAO2
XUEFEN SHENG1, WENBO RAO2
1
College of Geographical Sciences, Nanjing Normal University, Nanjing, Jiangsu 210097, PR China ([email protected]; [email protected]) 2 Radiogenic Isotope Laboratory, Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, QLD 4072, Australia ([email protected]) The origin of modern Homo sapiens has been the subject of an intensive debate between exponents of two competing hypotheses: ‘‘recent out of Africa’’ and multiregional origins. It is generally accepted that the hominid fossil and archaeological evidences from Africa, Europe and Mid-East support the former model, whilst those from East Asia are in line with the latter. The accurate dating of relevant finds is fundamental to addressing the above controversies. The reliability of U-series dates on pure and dense cave calcites has been well demonstrated.Mainly using this dating method, the chronologies of relevant hominid localities in southern China were reexamined in the past more than ten years. They include the sites of Liujiang, Laibin, Bailiandong and Tubo in Guangxi, Zhangkou and Xianren caves in Yunnan and Lianhua cave in Jiangsu. The results show that modern humans were present in China at least 100 ka ago, much earlier than previously estimated, and that the so-called ‘‘temporal gap’’ of human presence in China between 40 and 100 ka is most probably merely an artifact caused by systematic errors of previous dating methods. In an attempt to search for earliest representatives of modern hominid and to better understand the model of recent human evolution in China, further chronological studies are currently under way. Southern China provides a promising ground for research works in this direction, as the region hosts numerous Late Pleistocene hominid sites in limestone caves, where cultural or fossiliferous deposits are often intercalated with speleothem formations. With robust temporal constraints, the hominid finds there may contribute significantly to elucidating the much-debated issues concerning the origin, dispersal and evolution of modern H. sapiens.
1
State Key Laboratory of Hydrology—Water Resources and Hydraulic Engineering, Hohai University, China 2 Research Academy of Hohai University, China Most authors considered that chemical weathering only resulted in carbonate dissolution but did not alter silicate minerals evidently in Chinese Loess Plateau (Chen et al., 1998; Liu et al., 2002). However, silicate weathering intensity in Chinese Loess Plateau is not quantified yet. In this study, 87Sr/86Sr ratios of acid-soluble and acid-insoluble fractions (0.5 M HOAc solution leaching) of eolian dust in the Lingtai section during the last 7 Ma are determined to quantify chemical weathering intensity. Results display that 87Sr/86Sr ratios range between 0.7104 and 0.7116 for acid-soluble fractions, and vary from 0.7182 to 0.7234 for acid-insoluble fractions. 87 Sr/86Sr ratios of acid-soluble fractions in the Lingtai section are originally controlled by marine carbonate widely spreading over North China and eolian silicate weathering. So, the relative contribution of Sr released from silicate fractions due to chemical weathering in the Lingtai section can be calculated with a twocomponent mixing equation. One endmember is the silicate fraction and the other is marine carbonate. Acid-soluble fractions are assumed to represent silicate fractions with variable 87Sr/86Sr ratios in the past 7 Ma. The mean Sr isotope ratio of marine carbonate is considered to be 0.708 during the Phanerozoic. The mixing equation is given as 87Sr/86SrAS = X 87Sr/86SrAI + (1 X) 87 Sr/86SrMC, where AS is the acid-soluble fraction, AI represents the silicate fraction, MC is marine carbonate, X is the relative contribution of silicate fractions, and (1 X) denotes the relative contribution of MC. Results show that whether the Quaternary loess or the Tertiary red clays, their acid-soluble fractions contain less than 30% Sr derived from chemical weathering of silicate fractions in the Lingtai section during the last 7 Ma, and reveal weak chemical weathering in Chinese Loess Plateau.
References Chen, J., Ji, J.F., Qiu, G., et al., 1998. Sci.China Ser. D) 41 (3), 235–241. Liu, L.W., Chen, J., Chen, Y., et al., 2002. Acta Pedol. Sin. 39 (1), 65–70.
References Shen, G.J., Wang, W., Wang, Q., Zhao, J.X., Collerson, K., Zhou, C.L., Tobias, P.V., 2002. U-series dating of Liujiang hominid site in Guangxi, southern China. J. Hum. Evol. 43, 817–829. Shen, G.J., Li, J.K., Ji, X.P., 2005. U-series dating of Zhangkou Cave in Yiliang, Yunnan Province: Evidence for human activities in China during 40 and 100 ka. Chin. Sci. Bull. 50, 355–359. doi:10.1016/j.gca.2006.06.1074
doi:10.1016/j.gca.2006.06.1075