Age model of sediment core MD95-2010

The AMS age from level 903-904 cm cannot directly be transelated into cal. yr as this age is beyond the valid range of the calibration equation of Bard et al. 1991. While using Laj et al. (1990) comparison of deviation of radiocarbon ages from cal. yr. ages based on reconstructions of Earth's magnetics field strength, it is suggested that 14C ages in the range of 45-50 kyr should be corrected by 0-1 kyr. We have not used this point in the age model due to the uncertainties in how to correct this age. By using a linear sedimentation rate between the last AMS 14C age and the isotope stage 4.0, this level came up with an age of 45 kyr. The age of ash layer II in MD95-2010 is in GISP2 ice core is about 53kyr. This is in close agreement with the age we get from linear interpolation (=52.9kyr). The last fix point used in our age model is corresponding to marine isotope event 4.0 = 59kyr in SPECMAP (Martinson et al. 1989).

AMS测年（Accelerator Mass Spectrometry）得到的903~904cm层位的年龄无法直接转换为校准年代（cal. yr），因该年龄超出了Bard等人1991年提出的校准方程的有效适用范围。尽管基于Laj等人1990年通过地球磁场强度重建得到的放射性碳年龄与校准年代偏差对比结果，有研究建议对45~50 kyr范围内的碳十四（14C）年龄进行0~1 kyr的校正，但由于该年龄校正方案存在不确定性，我们未将其纳入本次的年龄模型。通过采用末次AMS碳十四年龄与同位素阶段4.0之间的线性沉积速率进行推算，该层位的年龄被确定为45 kyr。MD95-2010钻孔中的II号火山灰层的年龄（见于GISP2冰芯记录）约为53 kyr，这与我们通过线性插值得到的结果（52.9 kyr）高度吻合。本研究年龄模型中使用的最后一个固定点，对应于Martinson等人1989年发表的SPECMAP序列中的海洋同位素事件4.0，即59 kyr。