洪积扇上全新世古土壤的特点及环境意义--以临汾盆地东坡沟剖面为例

通过对山西襄汾东坡沟全新世黄土剖面地层学和土壤学的研究,以及碳酸钙、铁和粒度的测定,发现全新世古土壤中碳酸钙经历了明显的淋溶与淀积,古土壤上部CaCO₃平均含量10.58%,下部为18.47%,CaCO₃结核的淀积深度约为1.1m,铁在古土壤顶部有微弱的淋移和富集,粘化作用不明显。成壤作用始于全新世大暖期之初,较为强烈的成壤作用发生于大暖期的晚期(4100aB.P～3100aB.P),这一阶段土壤湿度大,气候波动小,CaCO₃淋溶较强。大暖期结束后,冬季风在黄土高原占主导地位,土壤的淋溶作用和粘土作用均有一定程度减弱,显示气候干旱的趋势。该剖面位于古山前洪积扇前端,地形较高,降水易分散,淋溶作用总的说来不强烈,土壤上部CaCO₃残留较多,CaCO₃淀积深度较浅,土壤类型接近黑垆土。

Characteristic of Paleosol on the Paleo-alluvial-pluvial Fans and Its Environmental Significance

Pedological and stratigraphic observations indicate that there is one paleosol layer on the Holocene loess profile in DPG site,Co. Xiangfen of Shanxi province. CaCO₃ , TFe and clay analysis prove that pedological process started at the beginning of the Holocene Magathermal. The major pedological process developed between 4450～3100aB.P, when climate was humid and stable, ancient people cultivated here and created the splendid culture of Taosi . The leaching of CaCO₃ existed during the pedological process . The illuvial depth of CaCO₃ is about 1.1m . The pedogenesis is not intense overall due to deep slope on palaeo-alluvial-pluvial fans. The type of paleosol here can be regarded as the one of Heilutu soil.