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冰川冻土 ›› 1989, Vol. 11 ›› Issue (3): 269-278.doi: 10.7522/j.issn.1000-0240.1989.0038

• 研究论文 • 上一篇    下一篇


沈永平, 焦克勤   

  1. 中国科学院兰州冰川冻土研究所
  • 收稿日期:1987-09-01 修回日期:1988-03-18 出版日期:1989-08-25 发布日期:2012-04-26

Discussion on the Pedogenesis and Environment of Paleosols on the Moraine Plateform in Nyalam, Xizang

Shen Yongping, Jiao Keqin   

  1. Lanzhou Institute of Glaciology and Geocryology, Chinese Academy of Sciences
  • Received:1987-09-01 Revised:1988-03-18 Online:1989-08-25 Published:2012-04-26

摘要: 中更新世大间冰期的湿热阶段,聂拉木冰碛平台发育了红壤土。随着喜马拉雅山的强烈抬升,晚更新世间冰期冰碛平台为黄棕壤,全新世及现代为亚高山灌丛草甸土壤。聂拉木地区自中更新世间冰期以后至今抬升量在2000m以上。

关键词: 古土壤, 土壤发生学, 成土环境, 环境变迁

Abstract: The moraine plateform in Nyalam, Xizarig, about 4000 m a.s.l., is located on the southern slope of the Himalaya. The weathering crusts and soils have developed on the moraine plateform since the interglacial period after the Nyalam (the Nynyxunglha) glaciation of the middle Pleistocene. Three soil-forming processes, indicating the change of natural environment during the uplift of the Himalaya of Quaternary, can be distinguished from the section of paleosols developed since then.From the paleosols profile, the paleosol of the middle Pleistocene is a soil with dark red coloure and the ferric oxide impregnation matrix, and being the ferric oxide nodules in the bottom horizone. The chemical analysis results show that intensity of the soil leaching was very strong in the paleosol, and some elements were concentrated or displaced in the soils, and the phenomena of weathering differenization appeared. The Fe2O3 was intensively concentrated in the soil. The X-ray diffraction patterns of clay fraction from the paleosol indicate the Chlorite-Kaolinite-Hydromica assemblage, and reflect the wet and warm climate, extensive leaching, acidic milieu and high precipitation. Through the grain-size analysis and observation of surface textures of Quartz sand in 0.355-0.50 mm size by microcopy,we found that soil-forming process is very actived to weathering of parent material.The grain-size of sediments became finer upward the section with silt content of 9.8% to 19.0% from unweathering till to the paleosol. The edges of Quartz grains were rounded and solution features on the surfaces.From what described above, the paleosol of the middle Pleistocene has the characteristics of red earth. The Pollen-Spore analysis result shows also that vegetation has the both features of evergreen broad leaf forest and tropical monsoonal rainforest with Enterolobium cyclocarpum and Quercus sp. and so on. The elevation of Nyalam did not excess 1800 m a.s.l. in that time if we consider the annual mean global temperature was 2 -4℃ higher than that at present.The yellow brown soils developed during the interglacial period of the late Pleistocene because of the uplifting of the Himalaya. The vegetation was the needle and broad leaf mixed forest with Pinus sp. and Quercus sp., the elevation might be at 2500-3100 m a.s.l. in Nyalam. The subalpine shrubby meadow soil is the moderm soil-forming process since Holocene.The evolution of soil-forming processes from the red earth to subalpine shrubby meadow soil reflects that the environment change and trend to cold and dry due to the upheave of the Himalaya. Soil-forming processes were adapted to the change of nature system, the old soil would be retreated. In the profiles of modern soil can be found the relic features of old soils, and have the recent features of soils comprising the characteristic of paleosols.

Key words: palesols, pedogenesis, soil-forming conditions, environmental change