THE INFLUENCING FACTORS AND ENVIRONMENTAL SIGNIFICANCE OF MAGNETIC SUSCEPTIBILITY IN THE GLACIO LACUSTRINAL SEDIMENTS ON THE DIANCANG MOUNTAINS, YUNNAN PROVINCE
-
摘要: 文章通过对点苍山海拔3820m冰水沉积剖面的粒度参数、磁化率、氧化铁含量和有机质含量的综合实验分析,并讨论了这些指标的相互关系及其环境意义。实验结果表明,磁化率的强度与粗砂组分的含量成正相关,而与粘土等细粒组分含量成负相关;同时与有机质含量成负相关,与氧化铁含量成正相关。矿物组分分析实验表明,沉积物主要磁性来源于磁化铁。根据以上结果,结合冰川湖泊流域面积小、高寒环境的特点,其磁化率的影响因素与一般湖泊不同,认为冰川湖泊沉积中,因为物源较近导致外源磁性矿物主要赋存于粒度较粗的碎屑颗粒中,而高寒的环境条件使得有机质对沉积物的磁性矿物起到了稀释的作用,而很难有积极的贡献。根据磁化率的环境意义,恢复了全新世以来点苍山的古气候,从中可以划分6个不同的气候阶段:11.5～10.6kaB.P.,10.6～8.9kaB.P.,8.9～5.5kaB.P.,5.5～3.3kaB.P.,3.3～0.8kaB.P.和0.8kaB.P.至今,代表了末次冰期结束以后湖泊从产生至消亡的全过程。根据与其他相关地区的对比,分析了西南季风演变的一些规律。Abstract: The Diancang Mountains, reaching an attitude of 4 122m, is located at the south western margin of the Qinghai Xizang Plateau. Towards the south is the low relief area of southeast Asia. To the north the Indian Ocean monsoon prevails and vertical climatic zoning is clear here. The Diancang Mountains is climatically situated between south subtropics and mid subtropics and the climate changes on the mountain are affected by the combined effects of vertical and horizontal climatic zones. Continental glaciers and glaciations were well developed during the Quaternary period. The Diancang Mountains is a typical region for studies on a diversity of biological species, evolution of ecological conditions and vegetation migration due to its special physical characteristics. A continuous record of climatic changes is recovered from a glacio lacustrinal sedimentary profile. The age of the oldest sediments, 11.5kaB.P. recorded climatic changes during the Holocene period and indicats that the lake formed after the last glaciation. Studies of the sediments were carried out by analysing magnetic susceptibility, grain size, organic material content and the contents of Fe 2O 3 and FeO. The results show that the magnetic susceptibility is positive proportional to the content of coarse sand and Fe 2O 3 and FeO, and reversal proportional to the contents of fine sand and organic materials. X ray diffraction indicates that the most magnetic susceptibility should be attributed to magnetite. The late glacial environmental changes, particularly during the Holocene period, have been reconstructed based on the analysis of grain size, environmental susceptibility and geochemistry in the stratigraphical profile. According to the experimental data, a warm stage is established during 11.5～10.6kaB.P. after the late glaciation. It became humid from 10.6kaB.P., and dried up from 8.9kaB.P. to 5.5kaB.P. It became cold and humid again after 5.5kaB.P., and warm and dry again from 3.3 to 0.8 kaB.P. It was humid from 0.8 to the preent.
-
Key words:
- the Diancang Mountains /
- glacial lakes /
- megnetic susceptibility /
-
-
[1] Thompson R, Oldfield F. Environmental Magnetism. London: George Allen & Unwin, 1986. 1～83
[2] 旺罗, 刘东生, 韩家懋等. 中国第四纪黄土环境磁学研究进展. 地球科学进展, 2000, 15(3): 335～341 Wang Luo, Liu Tungsheng, Han Jiamao et al. Environmental magnetism of Chinese Quaternary loess: A brief rieview. Advance in Earth Sciences, 2000, 15(3): 335～341
[3] Heller F, Liu T S. Magnetostratigraphical dating of loess deposits in China. Nature,1982, 300: 431～433
[4] 胡守云, 王苏民, Appel E 等.呼伦湖湖泊沉积物磁化率变化的环境磁学机制. 中国科学(D辑), 1998, 28(4): 334～339Hu Shouyun, Wang Sumin, Appel E et al. Environmental mechanism of magnetic susceptibility changes of lacustrine sediments from Lake Hulun, China. Science in China(Series D), 2000, 43(5): 534～540
[5] Wissmann H V. The Pleistocene glaciation in China. Bulletin of the Geological Society of China, 1937,ⅩⅦ: 145～168
[6] 赵维城, 万晔. "云南大理冰期"之再研究的迫切性及必要性. 云南地理环境研究, 1993, 5(2): 84～85Zhao Weicheng, Wan Ye. The impendency and necessary of the study on Dali Glaciation in Yunnan Province. Yunnan Geographic Environment Research, 1993, 5(2): 84～85
[7] 段诚中. 苍山气候. 见: 段诚中主编. 苍山植物科学考察. 昆明:云南科技出版社, 1995.14～38Duan Chengzhong. The climate of Cangshan. In: Duan Chengzhong ed. Scientific Investigation of the Plant on Cangshan Mountain. Kunming: Yunnan Science & Technology Press, 1995. 14～38
[8] 王苏民, 王云飞, 吉磊等. 若尔盖盆地湖泊深钻岩心记录. 见: 施雅风, 李吉均, 李炳元主编. 青藏高原晚新生代隆升与环境变化. 广东: 广东科技出版社, 1998. 161～213Wang Sumin, Wang Yunfei, Ji Lei et al. Records of the drilling cores in the Zoige Basin Lakes. In: Shi Yafeng, Li Jijun, Li Bingyuan eds. Uplift and Environmental Changes of Qinghai-Xizang (Tibetan) Plateau in the Late Cenozoic. Guangdong: Guangdong Science & Technology Press, 1998. 161～213
[9] Ozdemir O, Banerjee S K. A preliminary magnetic study of soil samples from west-central Minnesota. Earth and Planetary Science Letters, 1982, 59(2): 393～403
[10] Mather B A. Magnetic properties of some synthetic sub-micromagnetites. Geophysical Journal, 1988, 94: 83～96
[11] Yu L Z, Oldfield F, Wu Y S et al. Paleoenvironmental implications of magnetic measurements on sediment core from Kunming Basin, Southwest China. Journal of Paleolimnology, 1990, 3: 95～11
[12] 王建, 刘泽纯,姜文英等.磁化率与粒度、矿物的关系及其古环境意义. 地理学报, 1996, 51(2): 155～163Wang Jian, Liu Zechun, Jiang Wenying et al. A relationship between susceptibility and grain-size and minerals, and their paleo-environmental implications. Acta Geographica Sinica, 1996, 51(2): 155～163
[13] 殷勇, 方念乔,王倩等. 云南中甸纳帕海湖泊沉积物的磁化率及环境意义. 地理科学, 2002, 22(4): 413～419Yin Yong, Fang Nianqiao, Wang Qian et al. Magnetic susceptibility of lacustrine sediments and its environmental significance: Evidence from Napahai lake, northwestern Yunnan, China. Scientia Geographica Sinica, 2002, 22(4): 413～419
[14] Hilton J A, Lishman J P. The effect of redox change on the magnetic susceptibility of sediments from a seasonally anoxic lake. Limnology and Oceanography, 1985, 30: 907～909
[15] Snowball I F, Thompson R. The occurrence of greigite in sediments from Loch lomond. Journal of Quaternary Science, 1988, 3: 121～125
[16] John Hilton. A simple model for the interpretation of magnetic records in lacustrine and ocean sediments. Quaternary Research, 1987, 27: 160～166
[17] Members C. Climatic changes of the last 18,000 years: Observations and model simulations. Science, 1998, 241: 1 043～1 052
[18] 于革. 全球晚第四纪湖泊数据库的研究. 湖泊科学, 1997, 9(3): 193～202Yu Ge. Studies on global Late Quaternary lake-level data bases. Journal of Lake Sciences, 1997, 9(3): 193～202
[19] Gasse F, Arnold M, Fonts J C et al. A 13,000-year climate record from western Tibet. Nature, 1991, 353: 742～745
[20] 王苏民,王富葆. 全新世气候变化的湖泊记录.见:施雅风, 孔昭宸编. 中国全新世大暖期气候与环境. 北京: 海洋出版社, 1992. 146～152Wang Sumin, Wang Fubao. The liminogic record of Holocene fluctuation. In:Shi Yafeng, Kong Zhaochen eds. The Climates and Environments of Holocene Megathermal in China. Beijing: China Ocean Press, 1992. 146～152
[21] Sirocko F, Sarnthein M, Erlenkeuser H et al. Century-scale events in monsoonal climate over the past 24,000 years. Nature, 1993, 364: 322～324
[22] 张振克, 吴瑞金, 王苏民等. 全新世大暖期云南洱海环境演化的湖泊沉积记录. 海洋与湖沼, 2000, 31(2): 210～214Zhang Zhenke, Wu Ruijin, Wang Sumin et al. Environmental evolution recorded by lake sediments from Erhai Lake, Yunnan Province in Holocene megathermal. Oceanologia et Limnologia Sinica, 2000, 31(2): 210～214
[23] 《大理市志》编委会. 大理市志. 北京: 中华书局, 1998. 102～103Committee of edition of "Annal of Dali Municipality". Annal of Dali Municipality. Beijing: Zhonghua Book Company,1998.102～103
-
计量
- 文章访问数:
- PDF下载数:
- 施引文献: 0
下载: