轨道调谐建立洛川黄土地层的时间标尺

对黄土高原中部洛川厚140m黄土剖面进行了黄土层间隔5cm、古土壤层间隔3cm的采样，在室内测量了全部样品的磁化率．以磁化率变化作为东亚夏季风气候变化的替代性指标，利用轨道调谐方法建立了黄土－古土壤序列的时间标尺．结果表明，B／M界线处的年龄是772KaB．P，午城黄土与离石黄土分界线的年龄为1348KaB．P，黄土堆积底界的年龄为2471KaB．P．．通过和古地磁场倒转点绝对年龄对比以及与太阳辐射量变化时间序列进行交叉谱分析，证明了新时间标尺的可信性．

ORBITAL TUNED TIME SCALE FOR LOESS DEPOSIT IN LUOCHUAN OF CENTRAL CHINESE LOESS PLATEAU

The loess-paleosol profile in Luochuan of central Chinese Loess Plateau was sampled every 5cm in loess layers and 3cm in palaeosol layers, all samples were measured for magnetic suscephbility which is regarded as an excellent proxy index of East Asian summer monsoon variations during the Quaternary. On the basis of astronomical theory of Pleistocene climatic changes, we calibrated thes loess palaeosol sequence by tUned to the orbital records calculated by Berger and Loutre (1991) under the control of major magnetic reversals. The results show that the age of Brunes/ Matuyama boundary is 772ha B.P.; The age of boundary betWeen Lishi and Wucheng loess deposit is 1 348 Ka B. P. and loess has deposited since 2 471ka B. P.This new bine scale is tested by comparing the ages of magnetic reversals estimated from our bine scale with the ages determined by Cande and Kent (1992) and the cross spectral analysis of two bine series. The results show that the new bine scale is reliable.