西安地区全新世古土壤的研究

HOLOCENE PALEOSOL IN THE REGION OF XI'AN

本文根据磁化率、粒度、 Ｃａ Ｃ Ｏ３ 、 Ｆｅ２ Ｏ３ 和 Ａｌ２ Ｏ３ 含量以及土壤微结构等方面的资料对西安地区的全新世古土壤的性质和类型及环境的特点进行了较为全面的论述。各项资料显示，该地区全新世大暖期的古土壤为温湿气候条件下发育的淋溶褐土，而并非过去所称的半干旱条件下发育的“黑垆土”；该层古土壤发育时的年均降水量应不小于７５０ｍ ｍ 。全新世古土壤底部之下分布深度达 ２ｍ 多的密集根充填充物，指示当时存在森林植被。

Holocene paleosol has been called as loessial soil since its existence was determined. Recently, some researchers determined Holocene paleosol around Xi'an as luvic phaeozem or brown earth. However, these opinions about the paleosol are not uniform. In this paper, the characteristics, the types and the forming environment of the Holocene paleosol are discussed by applying the materials of magnetic susceptibility, grain size, contents of CaCO 3, Fe 2O 3 and Al 2O 3, soil micromorphology. These materials reveal that the Holocene paleosol around Xi'an is luvic cinnamon soil developing in warm and humid climate, but not developing in subarid climate. During the forming period of Holocene paleosol, the meean annual rainfall in Xi'an would be 750 mm or more, and the mean annual temperature would be about 15℃. There are deense root infilling with more than 2 m deep, under the bottom of Holocene paleosol, which suggests the existence of the forest at that time.