西安地区全新世中期环境研究

Research of Mid Holocene environment in Xi′an region

根据CaCO3,Fe2 O3和Al2 O3含量、土壤微结构以及孢粉等方面的资料对西安地区的全新世古土壤和植被类型与气候特点进行了研究 .结果表明 ,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 ,并非过去所称的半干旱条件下发育的“黑垆土” .孢粉分析和古土壤底部之下分布深度达 2m多的密集根孔的存在表明该层古土壤发育时的植被类型是以栎为主的落叶阔叶林 .可推测当时年降水量应不小于 75 0mm ,年均气温不低于 1 4℃ .

Holocene paleosol have 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 opinion about the type of paleosol are not uniform. In this paper, the author discusses Holocene paleosol, vegetation type and climate by the materials of contents of CaCO 3, Fe 2O 3 and Al 2O 3, soil micro morphology and sporo pollen analysis. These materials reveal that Holocene paleosol around Xi′an formed during Megathermal is luvic cinnamon soil developing in warm and humid climate but not developing in subarid climate. During the forming time of Holocene paleosol, vegetation type of this area would be deciduous broad leaved forest which mainly consist of Quercus according to pollen analysis and the existence of dense root cavity at the bottom of Holocene paleosol of which depth of distribution is more than 2m. At that time mean annual rainfall in Xi′an would be 750 mm or more and mean annual temperature would be about 14℃.