摘要
洛川黄土—古土壤序列记录了最近 2 .5Ma黄土高原自然环境的演化和变迁。国内外研究人员运用地层学、古生物学、土壤学、磁学、沉积学、岩石学、矿物学、地球化学等多学科的研究方法 ,统一地层划分 ,明确成因机制 ,建立时间标尺 ,分析气候指标 ,提取环境信息 ,逐步揭示了自早更新世以来该区气候由暖湿而冷干、频繁剧烈波动的历史以及古生物的演替过程 ,为全球变化研究提供了重要资料。
Luochuan section is located in Shaanxi province, at the central of Chinese Loess Plateau. Sandy shale and sand stone at Triassic is the bottom of gully. Red clay of Late Pliocene about 15m thick overlies the bedrock. The loess layer is 130m thick, and overlies red clay. Some reliable polarity columns for the Luochuan section has been derived in order to determine the important polarity boundaries and the age of loess layer exactly. M/G boundary lies at the Wucheng Loess /Red Clay boundary, Olduvai subchron is recorded at the middle-upper portion of Wucheng, Jaramillo subchron and B/M boundary lies in Lower Lishi loess. Other methods such as 14C and thermoluminescent can date Malan and S 0, and time scales established respectively by Liu, Ding, Lu and Kukla have showed the age of each loess layer. Loess-paleosol sequences in Luochuan China provide a detailed record of environment changes during the last 2.5million years. The histories of flora, fauna and climate could be observed by means of some proxies such as susceptibility, granularity, snail species, sporopollen, phytolith, CaCO 3, stable isotope, trace element, amino acid, and so forth. Investigation of them display that the long-term changes represented by Luochuan Loess-paleosol sequences have borne a multi-cycled feature with repeated climatic fluctuations from warm-humid to dry-cold. Before Olduvai subchron, some kinds of large mammals included Eucienoceros?Ursus sp.?Lynxshansius inhabited Luochuan basin; but after this, most of them disappeared except lagomorph and rodent. In this sequence from the bottom upwards, the content of Ca?Sr and Fe 2+ tends to increase; on the contrary, Al?K?Ti?Mn and Fe 3+ decreases; acidic amino acids are present in relatively greater amounts than alkaline amino acids; and CaCO 3 becomes more and more abundant. All of the facts imply that the depositional environment of Luochuan section has a bias to an alkaline and reductive thing. On the whole, the climate of Luochuan is becoming drier and colder. Th
出处
《地球科学进展》
CAS
CSCD
2002年第1期118-125,共8页
Advances in Earth Science
基金
国家自然科学基金重大项目"中国古季风区古环境演变机制及其与全球变化的动力学联系"(编号:49894170 )资助
