Characteristics and Significance of the Micromorphology of Neogene Red Clay of Xunyi,Shaanxi Province
-
摘要: 研究证实,新近系红土的土壤微形态特征也是判断古气候,划分对比地层的可信指标之一。用此方法研究陕西旬邑下墙晚新生代剖面的新近系及第四系最底部的岩石微形态特征及古气候,可将其分为 4个大段,自下而上第1大段,约相当于 6.8～ 5.3Ma,成壤作用以弱为主,气候是在新近纪总体暖湿背景下的凉干阶段;第 2大段,相当于5.3～ 4.2Ma,成壤作用以强为主,是新近纪最为暖湿的阶段;第 3大段,约相当于 4.2～ 2.6Ma,成壤作用较弱,气候由本阶段前半期较凉干变为后半期的较暖湿;第 4大段为进入 2.6Ma的第四纪初期,成壤作用极弱,气候由新近纪的总体暖湿突然变得冷干,在四大段的基础上还可看出次一级的微形态及气候变化与波动。此外还可根据土壤微形态特征划分中、上新统及上新统、更新统的界线。Abstract: This study has certified that investigating the characteristics of mic romorphology of Neogene red clay is also one of the effective methods to analyze the paleoclimate, and correlate and subdivide the strata. According to the ch aracteristics of micromorphology of Neogene red clay developed at Xiaqiang Villa ge, Xunyi County, Shaanxi Province, the Neogene paleoclimate of that area could be subdivided into four stages ranging from the bottom to the top, The first sta ge is around 6.8～5.3 Ma B. P. In this stage, the pedogenesis is generally weak; most of the grains are without directional arrangement; and the clay film is not cle ar. From these facts, we imagine the climate of that time was in a situation of cool-dry under the background of Neogene general climate of warm-humid. The s eco nd one is around 5.3～4.2 Ma B. P., with strong pedogenesis, directional arrange me nt of grains and well-developed drape-type clay film. The climate of t his stage might be the warmest and the most humid in all four stages. The third on e is almost in 4.2～2.6 Ma B.P.,and the pedogenesis in this stage is generally w eak, wi th only a little strong one appeared in this late period.We consider that the m ain climate condition of this stage was firsthg semiarid, then changed to semi- hum id. The fourth one is after 2.6 Ma B.P.,which had entered the Quaternary. In t his stage, the pedogenesis is extremely weak,with very few remained optical cla y film. These characteristics reflect the climate of this stage was very cold an d dry quite different from its previous Neogene general Climate. Within each of these four Paleoclimatic stages, the micromorphology also clearly shows the clim atic sub-changes and sub-fluctuations. Moreover, the boundary between the Mio cen e and the Pliocene, and also that between the Pliocene and the Quaternary could be determined at the beginning (or bottom)of the second stage (or part),and begi nning (or bottom)of the fourth stage (or part),respectively.
-
[1] 郭正堂, Fedoroff N, 刘东生. 130 Ma来黄土-古土壤序列的典型微型特征与古气候事件[J]. 中国科学(D辑),1996,26(5):392～398 [Guo Z T, Fedoroff N, Liu D S. Typical micromorphology and paleoclimatic events in loess-paleosol sequences since 130Ma[J]. Sciences in China (series D),1996,26(5):392～398 ] [2] 赵景波. 陕西黄土高原500kaBP前后的古土壤与气候带迁移[J]. 地理学报,2001,56(3):323～331 [Zhao J B. The paleosol and migration of climate zone about 500 ka BP in the Loess Plateau, Shaanxi[J]. Acta Geographica Sinica,2001,56(3):323～331] [3] 丁仲礼,孙继敏,朱日祥等. 黄土高原红粘土成因及上新世北方干旱化问题[J]. 第四纪研究, 1997,17(2):147～156[ Li D L, Sun J M, Zhu R X, et al. Origin of red clay in the Loess Plateau and drying of north China[J]. Quaternary Sciences, 1997,17(2):147～156] [4] 薛祥煦,张云翔,岳乐平. 黄土高原一个连续的晚新生代剖面及其划分与对比[J]. 地层学杂志,2001,25(2):81～86 [Xue X X,Zhang Y X,Yue L P. A continuous profile of Late Cenozoic era and it's division and correlation in the Loess Plateau [J].Journal of Stratigraphy,2001,25(2):81～86] [5] 薛祥煦,岳乐平,张云翔,王建其等.陕西旬邑新近系化学地层及环境[J]. 地层学杂志,2002,26 (2):81～86 [Xue X X, Yue L P, Zhang Y X,Wang J Q, et al. Chemical strata and environment of Neogene in Xunyi of Shaanxi [J].Journal of Stratigraphy,2002,26(2): 81～86] [6] 丁仲礼,孙继敏,杨石岭等,灵台黄土-红粘土序列的磁性地层及粒度记录[J]. 第四纪研究,1998,18(1):86～94 [Z.L. Ding, J. M. Sun, S. L. Yang, et al.A record of magnetostratigraphy and particle size in loess-red clay in Lingtai[J].Quaternary Sciences,1998,18(1):86～94] [7] 薛祥煦,岳乐平,王建其.从陕西旬邑上新生界剖面看黄土高原新近系/第四系界线[J]. 地层学杂志,2001,25(3):161～165[Xue X X., Yue L P, Wang J Q. Boundary between Neogene and Quaternary from a profile upper Cenozoic group in Xunyi of Shaanxi [J]. Journal of Stratigraphy, 2001,25(3): 161～165] [8] 杨石岭,侯圣山,陈明杨等. 中国黄土高原红粘土的磁性地层及其与灵台剖面的对比[J]. 第四纪研究,2000,20(5):423～434 [Yang S L, Hou S S, Chen M Y, et al. Magnetostratigraphy of red clay of Late Tertiary and correlation between it and Lingtai profile [J]. Quaternary Sciences, 2000, 20(5):423～434] [9] 孙东怀,刘东生,陈明杨等. 泾川晚第三纪红粘土序列的磁性地层与气候变化[J]. 中国科学(D辑),1997,27(3):265～270 [Sun D H, Liu D S, Chen M Y, et al. Magnetic stratigraphy and climatic change of red clay in the Loess Plateau of China[J].Science in China (series D),1997,27(3):265～271] [10] 薛祥煦,张云翔,岳乐平.陕西府谷老高川三趾马动物群的发现及时代分期[J]. 科学通报,1995,40(5):447～449[Xue X X, Zhang Y X, Yue L P. Discovery of Hipparion fauna and its division of time in the Laogaochuan in Fugu of Shaanxi [J]. Chinese Science Bulletin,1995,40(5):447～449] [11] Qing X K, Li Z X, McA Powell C, Zheng H B. Magnetostratigraphic record of the Late Miocene onset of monsoon,and Pliocene uplift of northern Tibet[J]. Earth and Planetary Science Letters, 2001,187: 83～97 -
点击查看大图
计量
- 文章访问数: 389
- HTML全文浏览量: 1
- PDF下载量: 432
- 被引次数: 0
下载:
