大九湖泥炭磁化率及腐殖化度记录的18.7 Ka BP气候变化

神农架大九湖泥炭沼泽是中纬度亚热带地区的高山泥炭沼泽，其连续沉积的泥炭剖面蕴含了丰富的气候变化信息，对揭示我国中纬度地区不同时间尺度的气候环境变化有着重要意义。使用碱提取溶液吸光度法对大九湖泥炭吸光度进行测定，以E4/E6比值表征腐殖化度，同时测定了泥炭的磁化率，通过AMS14C测年技术建立了神农架大九湖泥炭地的年代序列，结合区域的其他气候代用指标，分析大九湖泥炭磁化率与腐殖化度E4/E6的古气候意义：大九湖泥炭频率磁化率值高指示气候冷干，降水量小；磁化率值偏低指示气候暖湿，降水量大。E4/E6值高，腐殖化度低，指示气候冷干；值低，腐殖化度高，指示气候暖湿。探讨大九湖地区末次冰消期以来的气候变化，重建该区18.7 Ka BP 的气候演化过程：末次冰期结束期（18.7~11.7 Ka BP）气候比较冷干，期间存在气候冷暖干湿交替波动；全新世（11.7~0 Ka BP）以来，气温开始回升，气候比较暖湿，期间也存在突发性降温事件，其中，全新世早期（11.7~9.3 Ka BP）气候冷暖干湿交替波动，总体冷湿；全新世中期（9.3~3.5 Ka BP）气候暖湿；全新世晚期（3.5~0 Ka BP）气候温干。 关键词： 泥炭；磁化率；E4/E6；大九湖；气候变化

#br# Climate Changes Indicated by the Magnetic Susceptibility and the Humification Degree of the Dajiuhu Basin Peat Since 18.7 Ka BP

Located in the mid latitude subtropical region, the mountain peat bog in the Dajiuhu Basin of the Shennongjia area, Hubei abounds with climate change information. This information indicated by the profile of continuous peat deposition in the Dajuhu Basin is of great significance to reveal the climate change pattern in mid latitude China at different time scales. In this study, the Dajiuhu Basin peat was characterized with respect to its absorbance using the alkali extraction method, humification degree represented by E4/E6, and magnetic susceptibility. Combined with climatic proxies including E4/E6 and magnetic susceptibility, the chronosequence of the Dajiuhu Basin peat determined by the AMS14C dating technique was used to analyze the paleoclimate near the Dajiuhu Basin. The paleoclimate and precipitation are related to the magnetic susceptibility and E4/E6 in the same region. A higher magnetic susceptibility or a larger E4/E6 value (i.e., a lower humification degree) suggests a cold and dry climate and little precipitation. Upon the results, the climate evolution of the Dajiuhu Basin since the last deglaciation (18.7 ka BP) was reconstructed. A predominant cold and dry climate intercalated by warm and humid period was observed during 18.7-11.7 Ka BP, followed by a warm and humid climate and raised temperature in general during the Holocene (11.7-0 Ka BP). Specifically, the Early Holocene (11.7-9.3 Ka BP) was featured by a cold and dry climate (with occasional warm and humid periods), the Middle Holocene (9.3-3.5 Ka BP) warm and humid, and the Late Holocene (3.5-0 Ka BP) warm and dry. Key words：peat; magnetic susceptibility;E4/E6; Dajiuhu basin; climate change