【摘要】：揭示西安地區(qū)第5層古土壤中還原層的類型和水分平衡,對認(rèn)識西安地區(qū)S5古土壤發(fā)育時的氣候和植被以及地下水補給來源具有重要科學(xué)意義。通過對西安地區(qū)第5層古土壤(S5)的調(diào)查和多個剖面的觀察,在西安東郊任家坡剖面、南郊雙竹村剖面和藍田田家坡剖面首次發(fā)現(xiàn)該層古土壤黏化層中含有1~5mm大小的低價氧化鐵的灰綠色斑點。低價鐵的灰綠色斑點是在地勢較高和地下水位較深的還原作用下形成的,屬于高位還原層,不同于以往認(rèn)識的潴育化類型�；揖G色斑點指示S5古土壤發(fā)育時土壤中上部出現(xiàn)了雨季積水并處于還原環(huán)境,當(dāng)時雨季還原層含水量達到了飽和狀態(tài),土壤中上部含水量為42%左右,土壤水分非常充足。該層古土壤的紅色鐵質(zhì)膠膜遷移到了上部古土壤黏化層頂界之下6.3 m深的黃土中,表明當(dāng)時高含量重力水分布達到了6.3 m左右深度,至少出現(xiàn)過較長時期適于茂盛森林植被發(fā)育的氣候。在西安地區(qū)S5古土壤發(fā)育時,土壤水分的收入量大于支出量,土壤水分為顯著正平衡。當(dāng)時大氣降水在經(jīng)過蒸發(fā)、蒸騰與地表徑流損失之后,還有較多剩余的水分通過入滲補給深部土層水。S5古土壤發(fā)育時降水較豐富是導(dǎo)致該層古土壤出現(xiàn)高位還原層的主要因素。
[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.
【作者單位】： 陜西師范大學(xué)旅游與環(huán)境學(xué)院;黃土與第四紀(jì)地質(zhì)國家重點實驗室(中國科學(xué)院地球環(huán)境研究所);寶雞文理學(xué)院陜西省災(zāi)害監(jiān)測與模擬重點實驗室;
【基金】：陜西省自然科學(xué)基金項目(2015JM4135) 中國地質(zhì)調(diào)查局西安地質(zhì)調(diào)查中心項目《關(guān)中盆地第四系形成與演化》(水[2016]4) 國家自然科學(xué)基金國際合作項目(41210002)資助~~
【分類號】：S151.9

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