青藏高原东北边缘临夏盆地近30MaB.P.以来古气候环境演变特征——沉积物地球化学元素记录  

FEATURES OF PALEOCLIMATIC CHANGES SINCE ABOUT 30 MaB P IN LINXIA BASIN——GEOCHEMICAL RECORDS IN CENOZOIC SEDIMENT

作　　者：钟巍[1] 李吉均[2] 方小敏[2] 朱俊杰[2] 曹继秀[2] 

机构地区：[1]新疆大学地理系 [2]兰州大学地理科学系

出　　处：《地理研究》1998年第3期258-264,共7页Geographical Research

基　　金：国家"八五"攀登计划

摘　　要：由地化元素所揭示的近３０ＭａＢ．Ｐ．以来气候演变的序列及特征，即在第三纪大部分时间中，虽有冷干与暖湿的交替变化，但气候状况相对稳定；进入上新世后，气候不稳定性显著增加，表现为冷干与暖湿大幅度、频繁地交替，至第四纪早期，才又表现出相对冷湿的环境特征。这一变化特征一定程度上反映了东亚季风由上新世前不显著至上新世中逐步建立，直至第四纪早期稳定建立的动态过程。由地化元素揭示的近３０ＭａＢ．Ｐ．以来的气候演变过程与孢粉分析结果基本一致，其变化很可能同青藏高原的阶段性隆升有密切关系。The Cenozoic sediment in Linxia Basin, which locates at the northeastern fringe of Tibet plateau bears abundant informations on the plateau's uplift and paleoclimate. The paleoclimatic sequence revealed by geochemical elements (oxides) since about 30MaB.P. basically coincides with that revealed by spore pollen combinations, i.e., during most of the Teritary, although climate alternated by warm moist and cold dry, it generally represented a relative stable regiem. After stepping into the Pliocene, climatic unstablity increased clearly, alternated drastically and frequently by the periodes of cold dry and warm moist. Untill in the early Quaternary, a cold wet regiem appeared. This process perhaps reflects to a certain degree a dynamic process which the Asia monsoon displayed unobviously before the pliocene, began to establish in Pliocene, and established in the early Quaternary. Fluctuatins of geochemical contents are of profound tectonic climatic background, the periods in which geochemical contents fluctuated violently correspond to the active tectonic periods, and the climate turned to be cold. Spectrum analyses of the high resolution CaCO 3 curve show that during 30 Ma￣1 67 Ma, climate was mainly controlled by 21ka and 41ka cycles; but during 1 67 Ma￣0 73 Ma, the quasi￣100 ka cycle appeared, and got more and more obvious; till after 0 73MaB P , the 100 ka cycle became predominant. The loess record in our country has also revealed the similar result, and showed that the climate was modified greatly since the Tertiary, which maybe closely related to the pulsating uplifts of the Tibet plateau.

关 键 词：青藏高原 临夏盆地 古气候演变 地球化学 沉积物 

分 类 号：P532[天文地球—古生物学与地层学]