宇生核素暴露测年影响因素误差分析Error Analysis of Influence Factors of In Situ Cosmogenic Exposure Dating Method

DOI: 10.12677/AG.2017.76082, PDF, HTML, XML, 下载: 1,031  浏览: 2,051  国家自然科学基金支持

Abstract: In situ cosmogenic exposure dating method was developed in the 1980s. At present, the method has been widely used in many fields of geological hazard research and long-time erosion rate. The quantitative study of the age error made by the error of different parameters in the calculation formula, will contribute to the further understanding and better utilization of the technology. Thus, this article is based on the dating data of rock samples in different regions around the world to analyze error of the concentration, generation rate, erosion rate about in situ terrestrial cosmogenic nuclides, attenuation path length of cosmic ray and the density of the sample in the calculation formula. The results show that: (1) Errors of the concentration and the generation rate about in situ terrestrial cosmogenic nuclides are proportional to the age error. (2) The maximum time error caused by sample density can be up to 16%. (3) The error of absorption mean free path is up to 31%. (4) The result of the erosion rate is related to the exposure time scale of the sample, which can be more than 100 %. This study can be used to provide reference data for the better application of in situ cosmogenic exposure dating method in geomorphology.

2. 数据和研究方法

2.1. 数据来源

2.2. 研究方法

2.2.1. 宇生核素暴露测年原理

$N\left(x,t\right)=N\left(x,0\right){\text{e}}^{-\lambda t}+\frac{p\left(0\right)}{\lambda +\mu \epsilon }{\text{e}}^{-\mu x}\left[1-{\text{e}}^{-\left(\lambda +\mu \epsilon \right)t}\right]$ (1)

$N=\frac{p}{\lambda +\mu \epsilon }\left[1-{\text{e}}^{-\left(\lambda +\mu \epsilon \right)t}\right]$ (2)

Table 1. Sources of cosmogenic nuclide 10Be datum [5]

$t=-\frac{1}{\lambda +\mu \epsilon }\mathrm{ln}\left[1-\frac{N\cdot \left(\lambda +\mu \epsilon \right)}{P}\right]$ (3)

$t=-\frac{1}{\lambda }\mathrm{ln}\left[1-\frac{N\cdot \lambda }{P}\right]$ (4)

2.2.2. 宇生核素浓度和生成速率所造成的年代误差计算方法

2.2.3. 样品密度和宇宙射线衰减路径长度所造成的年代误差计算方法

2.2.4. 侵蚀速率所造成的年代误差计算方法

3. 结果与讨论

3.1. 宇生核素10Be的生成速率和浓度所造成的年代误差分析

3.2. 样品密度ρ所造成的年代误差分析

3.3. 宇宙射线衰减路径长度Λ所造成的年代误差分析

3.4. 侵蚀速率对年代结果影响的误差分析

Figure 1. The influence of the sample density error for the age results (Unit：ρ (g/cm3)，ε (mm/ka))

Figure 2. The effect of the absorption mean free path for the age results (Unit：Λ (g/cm2)，ε (mm/ka))

Figure 3. Effects of different erosion rates on samples of different exposures

4. 结论

1) 假设地貌体侵蚀速率为0时，10Be的生成速率、10Be的浓度对年代结果的影响呈正相关关系。

2) 样本密度ρ、衰变系数Λ的误差对年代结果的影响较小。随侵蚀速率ε增大，影响率增大；随误差值增大，影响率增大。

3) 实际侵蚀速率越大，对年代结果影响越大；且相同的侵蚀速率，暴露时间越长，对年代结果的影响率越高。

NOTES



*通讯作者。

 [1] 张志刚, 徐孝彬, 王建, 等. 青藏高原地区宇生核素暴露年代数据存在问题探讨[J]. 地质论评, 2014, 60(6): 1359-1369. [2] Raisbeck, G.M., Yiou, F., Klein, J., et al. (1983) Accelerator Mass Spectrometer Measurement of Cosmogenic 26Al in Terrestrial and Extraterrestrial Matter. Nature, 301, 690-692. https://doi.org/10.1038/301690a0 [3] Elmore, D. and Phillips, F. (1987) Accelerator Mass Spectrometry for Measurement of Long-Lived Radioisotopes. Science, 236, 543-550. https://doi.org/10.1126/science.236.4801.543 [4] Balco, G., Stone, J.O., Lifton, N.A., et al. (2008) A Complete and Easily Accessible Means of Calculating Surface Exposure Ages or Erosion Rates from Be-10 and Al-26 Measurements. Quaternary Geochronology, 3, 174-195. https://doi.org/10.1016/j.quageo.2007.12.001 [5] 张志刚, 王建, 白世彪, 等. 地表岩石侵蚀速率对宇生核素暴露测年影响的研究[J]. 地理科学, 2014(1): 116-121. [6] Balco, G. (2011) Contributions and Unrealized Potential Contributions of Cosmo-genic-Nuclide Exposure Dating to Glacier Chronology, 1990-2010. Quaternary Science Reviews, 30, 3-27. https://doi.org/10.1016/j.quascirev.2010.11.003 [7] Gosse, J.C. and Phillips, F.M. (2001) Terrestrial In Situ Cosmogenic Nuc-lides: Theory and Application. Quaternary Science Reviews, 20, 1475-1560. https://doi.org/10.1016/S0277-3791(00)00171-2 [8] Ballantyne, C.K. (2010) Extent and Deglacial Chronology of the Last British-Irish Ice Sheet: Implications of Exposure Dating Using Cosmogenic Isotopes. Journal of Quaternary Science, 25, 515-534. https://doi.org/10.1002/jqs.1310 [9] Owen, L.A., Yi, C.L., Finkel, R.C., et al. (2010) Quaternary Glaciation of Gurla Mandhata (Naimon’anyi). Quaternary Science Reviews, 29, 1817-1830. https://doi.org/10.1016/j.quascirev.2010.03.017 [10] Arzhannikov, S.G., Braucher, R., Jolivet, M., et al. (2012) History of Late Pleistocene Glaciations in the Central Sayan-Tuva Upland (Southern Siberia). Quaternary Science Reviews, 49, 16-32. https://doi.org/10.1016/j.quascirev.2012.06.005 [11] Zhang, Z.G., Xu, X.B., Wang, J., Jian, et al. (2014) Last Deglaciation Climatic Fluctuation Record by the Palaeo-Daocheng Ice Cap, Southeastern Qinghai-Tibetan Plateau. Acta Geologica Sinica (English Edition), 88, 1863-1874. https://doi.org/10.1111/1755-6724.12352 [12] 王建, 张志刚, 徐孝彬, 等. 青藏高原东南部稻城古冰帽南缘第四纪冰川活动的宇生核素年代研究[J]. 第四纪研究, 2012, 32(3): 394-402. [13] Owen, L.A., Robinson, R., Benn, D.I., et al. (2009) Quaternary Glaciation of Mount Everest. Quaternary Science Reviews, 28, 1412-1433. https://doi.org/10.1016/j.quascirev.2009.02.010 [14] Seong, B.A., Owen, L.A., Yi, C.L., et al. (2009) Quaternary Glaciation of Muztag Ata and Kongur Shan: Evidence for Glacier Response to Rapid Climate Changes throughout the Late Glacial and Holocene in Westernmost Tibet. Geological Society of America Bulletin, 121, 348-365. https://doi.org/10.1130/B26339.1 [15] Zech, R., Zech, M., Kubik, P.W., et al. (2009) Deglaciation and Landscape History around Annapurna, Nepal, Based on 10Be Surface Exposure Dating. Quaternary Science Reviews, 28, 1106-1118. https://doi.org/10.1016/j.quascirev.2008.11.013 [16] Heyman, J., Stroeven, A.P., Caffee, M.W., et al. (2011) Palaeoglaciology of Bayan Har Shan, NE Tibetan Plateau: Exposure Ages Reveal a Missing LGM Expansion. Quaternary Science Reviews, 30, 1988-2001. https://doi.org/10.1016/j.quascirev.2011.05.002 [17] Zahno, C., Akcar, N., Yavuz, V., et al. (2010) Chronology of Late Pleis-tocene Glacier Variations at the Uludag Mountain, NW Turkey. Quaternary Science Reviews, 29, 1173-1187. https://doi.org/10.1016/j.quascirev.2010.01.012 [18] Darnault, R., Rolland, Y., Braucher, R., et al. (2012) Timing of the Last Deglaciation Revealed by Receding Glaciers at the Alpine-Scale: Impact on Mountain Geomorphology. Quaternary Science Reviews, 31, 127-142. https://doi.org/10.1016/j.quascirev.2011.10.019 [19] Larsen, N.K., Linge, H., Hakansson, L., et al. (2012) Investigating the Last Deglaciation of the Scandinavian Ice Sheet in Southwest Sweden with 10Be Exposure Dating. Journal of Quaternary Science, 27, 211-220. https://doi.org/10.1002/jqs.1536 [20] Rinterknecht, V., Braucher, R., Bose, M., et al. (2012) Late Quaternary Ice Sheet Extents in Northeastern Germany Inferred from Surface Exposure Dating. Quaternary Science Reviews, 44, 89-95. https://doi.org/10.1016/j.quascirev.2010.07.026 [21] Owen, L.A., Frankel, K.L., Knott, J.R., et al. (2011) Beryllium-10 Terrestrial Cosmogenic Nuclide Surface Exposure Dating of Quaternary Landforms in Death Valley. Geomorphology, 125, 541-577. https://doi.org/10.1016/j.geomorph.2010.10.024 [22] Roberts, D.H., Long, A.J., Schnabel, C., et al. (2009) Ice Sheet Extent and Early Deglacial History of the Southwestern Sector of the Greenland Ice Sheet. Quaternary Science Reviews, 28, 2760-2773. https://doi.org/10.1016/j.quascirev.2009.07.002 [23] Stroeven, A.P., Fabel, D., Codilean, A.T., et al. (2010) Investigating the Glacial History of the Northern Sector of the Cordilleran Ice Sheet with Cosmogenic 10Be Concentrations in Quartz. Quaternary Science Reviews, 29, 3630-3643. https://doi.org/10.1016/j.quascirev.2010.07.010 [24] Hein, A.S., Hulton, N.R.J., Dunai, T.J., et al. (2009) Middle Pleistocene Glaciation in Patagonia Dated by Cosmogenic-Nuclide Measurements on Outwash Gravels. Earth and Planetary Science Letters, 286, 184-197. https://doi.org/10.1016/j.epsl.2009.06.026 [25] Hein, A.S., Hulton, N.R.J., Dunai, T.J., et al. (2010) The Chronology of the Last Glacial Maximum and Deglacial Events in Central Argentine Patagonia. Quaternary Science Reviews, 29, 1212-1227. https://doi.org/10.1016/j.quascirev.2010.01.020 [26] Todd, C., Stone, J., Conway, H., et al. (2010) Late Quaternary Evolution of Reedy Glacier, Antarctica. Quaternary Science Reviews, 29, 1328-1341. https://doi.org/10.1016/j.quascirev.2010.02.001 [27] Altmaier, M., Herpers, U., Delisle, G., et al. (2010) Glaciation History of Queen Maud Land (Antarctica) Reconstructed from in Situ Produced Cosmogenic 10Be, 26Al and 21Ne. Polar Science, 4, 42-61. https://doi.org/10.1016/j.polar.2010.01.001 [28] Johnson, J.S., Bentley, M.J., Roberts, S.J., et al. (2011) Holocene Deglacial History of the Northeast Antarctic Peninsula—A Review and New Chronological Constraints. Quaternary Science Reviews, 30, 3791-3802. https://doi.org/10.1016/j.quascirev.2011.10.011 [29] Fogwill, C.J., Hein, A.S., Bentley, M.J., et al. (2012) Do Blue-Ice Moraines in the Heritage Range Show the West Antarctic Ice Sheet Survived the Last Interglacial? Palaeogeography, Palaeoclimatology, Palaeoecology, 335-336, 61-70. https://doi.org/10.1016/j.palaeo.2011.01.027 [30] Lal, D. (1991) Cosmicray Labeling of Erosion Surfaces: In Situ Nuclide Pro-duction Rates and Ersion Models. Earth and Planetary Science Letters, 104, 424-439. https://doi.org/10.1016/0012-821X(91)90220-C [31] Dong, G.C., Yi, C.L. and Marc, C. (2014) 10Be Dating of Boulders on Moraines from the Last Glacial Period in the Nyainqentanglha Mountains, Tibet. Science China: Earth Sciences, 57, 221-231. https://doi.org/10.1007/s11430-013-4794-z [32] Chen, Y.X., Li, Y.K., Wang, Y.Y., et al. (2015) Late Quaternary Glacial History of the Karlik Range, Easternmost Tian Shan, Derived from 10Be Surface Exposure and Optically Stimulated Luminescence Datings. Quaternary Science Reviews, 115, 17-27. https://doi.org/10.1016/j.quascirev.2015.02.010 [33] Balco, G. and Schaefer, J.M. (2016) Cosmogenic-Nuclide and Varve Chronologies for the Deglaciation of Southern New England. Quaternary Geochronology, 1, 15-28. https://doi.org/10.1016/j.quageo.2006.06.014 [34] Ballantyne, C.K., McCarroll, D. and Stone, J.O. (2011) Periglacial Trimlines and the Extent of the Kerry-Cork Ice Cap, SW Ireland. Quaternary Science Reviews, 30, 3834-3845. https://doi.org/10.1016/j.quascirev.2011.10.006 [35] Balco, G., Schaefer, J.M. and LARISSA Group (2013) Exposure-Age Record of Holocene Ice Sheet and Ice Shelf Change in the Northeast Antarctic Peninsula. Quaternary Science Reviews, 59, 101-111. https://doi.org/10.1016/j.quascirev.2012.10.022 [36] Fabel, D., Stroeven, A.P., Harbor, J., et al. (2002) Landscape Preservation under Fennoscandian Ice Sheets Determined from in Situ Produced 10Be and 26Al. Earth and Planetary Science Letters, 201, 397-406. https://doi.org/10.1016/S0012-821X(02)00714-8 [37] Barrows, T.T., Stone, J.O., Fifield, L.K., et al. (2002) The Timing of the Last Glacial Maximum in Australia. Quaternary Science Reviews, 21, 159-173. https://doi.org/10.1016/S0277-3791(01)00109-3 [38] Dunai, T.J. (2010) Cosmogenic Nuclides: Principles, Concepts, and Ap-plications in the Earth Surface Sciences. Cambridge University Press, Cambridge. https://doi.org/10.1017/CBO9780511804519 [39] Gillespie, A.R. and Bierman, P.R. (1995) Precision of Terrestrial Exposure Ages and Erosion Rates Estimated from Analysis of Cosmogenic Isotopes Produced in Situ. Journal of Geophysical Research-Solid Earth, 100, 24637-24649. https://doi.org/10.1029/95JB02911