末次盛冰期以来兴凯湖的古环境演变——基于地磁场长期变化的年龄框架  

PALEOENVIRONMENT EVOLUTION OF THE LAKE KHANKA SINCE THE LAST GLACIAL MAXIMUM:AGE MODEL RECONSTRUCTED BY SECULAR VARIATION OF GEOMAGNETIC FIELD

作　　者：陈皎杰 刘焱光[1] 葛淑兰[1] 刘建兴[2,3] 李朝新[1] 石学法[1] 

机构地区：[1]海洋沉积与环境地质国家海洋局重点实验室,国家海洋局第一海洋研究所,青岛266061 [2]中国科学院地质与地球物理研究所古地磁与年代学实验室,北京100029 [3]中国科学院大学,北京100049

出　　处：《第四纪研究》2014年第3期528-539,共12页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41076038)资助

摘　　要：对小兴凯湖内一根长6m的钻孔（XKH1）进行了沉积物颜色、粒度、古地磁和总有机碳、总氮分析。通过与贝加尔湖和琵琶湖沉积岩芯磁倾角记录的对比，建立了该岩芯的时间序列；基于多指标综合分析，重建了24ka以来兴凯湖区域古环境和古气候演化历史，讨论了湖区环境对东亚季风和北半球温度变化的响应；通过粒级一标准偏差方法获得的环境敏感粒级组分9．29～63．00μm能作为降水量的指标。末次盛冰期时（24．0～19．5kaB．P．），东亚冬季风盛行，XKHl岩芯沉积物平均粒径相对较粗，亮度（r）和磁化率（x）值高，有机质含量低，反映湖区气候冷湿，湖泊缓慢扩张，湖面比现在低。19．5～18．4kaB．P．，东亚夏季风逐渐减弱，使流域降雨量减少，湖泊收缩，沉积物有机质含量显著增加，可能在湖滨区域发育了沼泽沉积。18．4～15．1kaB．P．沉积物中植物茎碎片含量高，砂含量波动频繁，指示了湖面进一步降低。冰消期（15．1～11．4kaB．P．），沉积物磁化率（x）升高，色度值（a‘）减小，反映东亚夏季风逐渐增强，湖区降雨量增加，湖泊扩张，为高湖面时期，沉积层底部和顶部砂含量增加明显，环境敏感粒级组分9．29～63．00μm的含量呈现减小一增大一减小的变化规律，可很好的对应于OD/B-A/YD气候波动事件。进入全新世，夏季风进一步增强，11．2～10．6kaB．P．时，XKHl沉积物平均粒径增加，指示降雨量的增加为湖区带来大量沉积物，开始在近岸发育砂坝，大、小兴凯湖被隔开；3．80～0．58kaB．P．时，色度值（a’）剧烈升高，发育虫穴构造并被黄褐色结核充填，指示湖面变浅，气候干旱。Khanka Lake （44°32＇- 45°24＇N, 131°59＇- 132°51＇E） crosses the Sino-Russia boundary, is located in Heilongjiang Province and three hundred kilometers away from the Sea of Japan. The climate is typical humid to semi-humid and temperate controlled mainly by East Asian monsoon. The level of Lake Khanka has fluctuated many times since Quaternary and the Small Lake Khanka was formed after the last regression. Besides four water channels between Small and Large Khanka Lake,there are many rivers flow into the Small Khanka Lake, such as Jinyinku River, Chengzi River, Kanzi River et al. We collected a 6m-long sediment core （XKH1,45°21. 493＇N, 132°25. 356＇E） from the Small Lake Khanka at 2.5m water depth. The sediments are mainly composed of sih with several sandy silt intercalations. The sediments color is olive gray and grayer black except for the sallow sediments from surface to ll5em, and black to gray black sediments at layers of 229 - 240cm and 463 - 492cm. 257 samples （2-cm intervals） and 54 samples （ 10-cm intervals） were collected for grain size and total organic carbon and nitrogen （TOC, TN） analysis, respectively. 231 samples were collected by cubic plastic boxes （2cm×2cm×2cm） at 2cm intervals for paleomagnetic analysis. The chronological frame of Core XKH1 is obtained by comparing the geomagnetic inclination lows recorded in XKH1 and Lake Biwa. Multi-proxies of grain size, total organic carbon and nitrogen （TOC, TN）, magnetic susceptibility （MS） , and color reflectance are used for paleoenvironmental reconstruction in Lake Khanka since the last glacial maximum （LGM）. From 24ka B.P. to 19.5ka B.P., Lake Khanka experienced low water-level and cooling-wet climate evidenced from the low mean grain-size, a＊（〈0）, TOC （0.3%-0.7%）and high sediment brightness （ca.41） and MS （ea.ll×10^-8m^3/kg） values. High TOC content （〉3%） and significant variation in others proxies suggested near shore swamp deposition environment during 19.5ka B.P. and

关 键 词：兴凯湖 地磁场长期变化 古气候 环境敏感粒级 末次盛冰期 

分 类 号：P534.63[天文地球—第四纪地质学] P318.41[天文地球—古生物学与地层学]