摘要
根据对大九湖297cm厚的泥炭地层10个AMS^(14)C年龄的测定以及148块孢粉样品的分析,发现每块样品的孢粉(浓度)含量都很高,植物种类繁多,分属于137(科)属,可划分为6个孢粉组合带,植被类型演替大体为含少量常绿树种的针阔叶混交林—含常绿阔叶树种的落叶阔叶林—常绿落叶阔叶林—含常绿阔叶树种的落叶阔叶林—含少量常绿树种的针阔叶混交林。孢粉带Ⅰ(15.753~11.280kaB.P.)记录了该区域晚冰期及其向全新世过渡时期冷暖波动频繁的气候条件,其中亚带Ⅰ-1(15.753~15.549kaB.P.),Ⅰ-3(14.936~14.505kaB.P.)和Ⅰ-5(12.655~11.280kaB.P.)可能分别对应最老仙女木期、老仙女木和新仙女木冷期,而亚带Ⅰ-2(15.549~14.936kaB.P.)和Ⅰ-4(14.505~12.655kaB.P.)分别对应博令和阿勒罗德暖期。孢粉带Ⅱ(11.280~9.218kaB.P.)代表了由晚冰期冷湿气候向全新世温暖气候转换的早全新世缓慢升温的过渡时期。孢粉带Ⅲ(9.218~7.530kaB.P.)代表中全新世前期的气温波动上升期,7.7kaB.P.前后达到最高温。孢粉带Ⅳ(7.530~4.051kaB.P.)代表中全新世适宜期,水热配置条件最佳。孢粉带Ⅴ(4.051~0.911kaB.P.)体现晚全新世温干的气候。孢粉带Ⅵ(0.911~0kaB.P)反映了大九湖温凉稍湿的气候。
A peat core with a depths of 297cm was obtained from the Dajiuhu Basin (31°29′27″N, 109°59′45″E, 1760m) of Shennongjia, Hubei Province, China. 10 dating data by AMS ^14C method provide a high-resolution time scale and indicate that the core was deposited during the past 15753 years (calendar year). 137 pollen types were identified from 148 samples taken at 2cm intervals, among which trees and shrubs are dominant. 6 pollen zones were derived from bottom to top. In Zone Ⅰ, from 297cm to 203cm ( 15. 753 - 11. 280kaB. P. ) , pollen concentration is low but fluctuant on the one hand, on the other hand, percentages of conifers and aquatics are the highest in the profile, showings a frequent climate fluctuation during late-glacial period. According to the pollen percentage spectrum and concentration spectrum, it seems that the sub zone Ⅰ-1 (15. 753 -15. 549kaB. P. ) , sub zone Ⅰ-3 ( 14. 936 - 14. 505kaB. P. ) and sub zone Ⅰ-5 ( 12. 655 - 11. 280kaB. P. ) correspond respectively the Oldest Dryas, the Older Dryas, and the Younger Dryas, while Ⅰ- 3 ( 14. 936 - 14. 505kaB. P. ) and Ⅰ- 4 (14.505 - 12. 655kaB. P. ) the Boiling and the Allerod respectively. In Zone Ⅱ , from 203cm to 179cm (11. 280 -9. 218kaB. P. ) , pollen concentration and tree types increase, tree percentages increase, showing slow temperature rises. In Zone Ⅲ , from 179 - 143cm (9. 218 -7. 530kaB. P. ) , pollen concentration decreases as a whole but the changes of different taxa vary heavily, i. e., those of conifers and deciduous trees decrease, while that of evergreen trees increases gradually. The climate is warm and dry. Zone Ⅳ, from 143 -113cm (7. 530 4. 051kaB. P. ) , represents the Holocene Optimum during which pollen concentration is the highest in the profile. Percentages of evergreen trees and deciduous trees are both high. Sub zone Ⅳ-1 shows fluctuated climate and sub zone Ⅳ-2 shows the best condition of water and heat during the Holocene. In Zone Ⅴ , from 113 -33cm (4. 051 0.911kaB. P. ), pollen concentration decreases but the changes of different taxa vary acutely, among which percentage of evergreen trees decreases and that of deciduous trees increases. This zone implies a warm and dry climate during Late Holocene. In Zone Ⅵ, from 33 -0cm (0. 911 -0kaB. P. ) , percentage of broadleaf trees, most of which are deciduous trees, is high; conifers increase obviously. It indicates that the climate during this period is cool and wet. Palynological data from the Dajiuhu Basin gives new evidence for paleoenvironmental reconstruction of the upper and middle reaches of the Changjiang River during the past 15753 years. The current primary research results show that the climate changes of this region not only are synchronous in a certain extent with other places, but also show local and regional characteristics.
出处
《第四纪研究》
CAS
CSCD
北大核心
2006年第5期814-826,共13页
Quaternary Sciences
基金
国家自然科学基金重大研究计划项目(批准号:90411015)
教育部高等学校博士点基金项目(批准号:20050284011)
中国科学院地球环境研究所黄土与第四纪地质国家重点实验室开放基金项目(批准号:SKLLQG0503)
南京大学"985"自然地理学科建设与南京大学现代分析中心测试基金项目资助