西安地区第5层古土壤中的铁质薄膜类型与水文特征

发布时间：2019-02-09 19:16

【摘要】：揭示西安地区第5层古土壤中还原层的类型和水分平衡,对认识西安地区S5古土壤发育时的气候和植被以及地下水补给来源具有重要科学意义。通过对西安地区第5层古土壤(S5)的调查和多个剖面的观察,在西安东郊任家坡剖面、南郊双竹村剖面和蓝田田家坡剖面首次发现该层古土壤黏化层中含有1~5mm大小的低价氧化铁的灰绿色斑点。低价铁的灰绿色斑点是在地势较高和地下水位较深的还原作用下形成的,属于高位还原层,不同于以往认识的潴育化类型。灰绿色斑点指示S5古土壤发育时土壤中上部出现了雨季积水并处于还原环境,当时雨季还原层含水量达到了饱和状态,土壤中上部含水量为42%左右,土壤水分非常充足。该层古土壤的红色铁质胶膜迁移到了上部古土壤黏化层顶界之下6.3 m深的黄土中,表明当时高含量重力水分布达到了6.3 m左右深度,至少出现过较长时期适于茂盛森林植被发育的气候。在西安地区S5古土壤发育时,土壤水分的收入量大于支出量,土壤水分为显著正平衡。当时大气降水在经过蒸发、蒸腾与地表径流损失之后,还有较多剩余的水分通过入渗补给深部土层水。S5古土壤发育时降水较丰富是导致该层古土壤出现高位还原层的主要因素。
[Abstract]:It is of great scientific significance to reveal the type and water balance of reducing layer in the 5th paleosol in Xi'an area, which is of great significance to understand the climate, vegetation and groundwater recharge source of S5 paleosol in Xi'an area. Based on the investigation of the 5th layer of paleosol (S5) and the observation of several sections in Xi'an, the Renjiapo section in the eastern suburb of Xi'an, In the southern suburb of Shuangzhucun and Lantianjiapo sections, it is the first time to find the gray-green spots of 1~5mm size iron oxide in the paleosol clay layer of this layer. The grey-green spots of low valence iron are formed under the action of higher topography and deeper groundwater level, and belong to the high reducing layer, which is different from the previously known type of hydrocisterization. The gray-green spots indicated that the upper and middle part of the S _ 5 paleosol had accumulated water in the rainy season and was in a reductive environment. At that time, the water content of the reducing layer reached saturation state, the water content of the upper part of the soil was about 42%, and the soil moisture was very sufficient. The red iron colloidal film of the paleosol migrated to the loess with a depth of 6.3 m below the top boundary of the upper paleosol, indicating that the distribution of gravity water at that time reached about 6.3 m depth. At least there has been a climate suitable for the development of lush forest vegetation for a long time. During the development of S5 paleosol in Xi'an area, the income of soil water was higher than that of expenditure, and the soil water was significantly positive equilibrium. At that time, after evaporation, transpiration and loss of surface runoff, There is also more residual water through infiltration to recharge the deep soil water, and the rich precipitation during the development of S5 paleosol is the main factor leading to the formation of high reducing layer in this layer of paleosol.
【作者单位】：陕西师范大学旅游与环境学院;黄土与第四纪地质国家重点实验室(中国科学院地球环境研究所);宝鸡文理学院陕西省灾害监测与模拟重点实验室;
【基金】：陕西省自然科学基金项目(2015JM4135) 中国地质调查局西安地质调查中心项目《关中盆地第四系形成与演化》(水[2016]4) 国家自然科学基金国际合作项目(41210002)资助~~
【分类号】：S151.9

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