| 陕西长武古土壤深部风化剖面与环境研究 |
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| 引用本文： | 赵景波.陕西长武古土壤深部风化剖面与环境研究[J].中国沙漠,2000,20(3):252-255. |
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| 作者姓名： | 赵景波 |
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| 作者单位： | 陕西师范大学,旅游与环境学院,陕西,西安,710062;中国科学院,西安黄土与第四纪地质国家重点实验室,陕西,西安,710062 |
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| 基金项目： | 国际地质对比计划项目!(IGCP3 79)，国土资源部九·五重点科技项目!( 95 0 110 4)，岩溶动力学开放实验室项目 ( 980 1) |
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| 摘 要： | 根据作者提出的ＣａＣＯ３淀积深度理论、风化剖面的野外鉴别和室内ＣａＣＯ３、磁化率测定、粒度分析，确定了陕西长武第４、第５层古土壤底部之下存在深部风化黄土和迁出了土壤层的ＣａＣＯ３结核层。这种风化黄土层和ＣａＣＯ３淀积层的发育表明当时风化淋滤作用超出了成壤带深度范围，指示长武第４、第５层古土壤为不具ＣａＣＯ３淀积层的中酸性、淋溶型森林土壤。该风化层代表了降水丰富的气候事件，当时年均降水量为９００ｍｍ
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| 关 键 词： | 黄土 风化剖面 深层淋滤 降水事件 古土壤 环境 |
| 修稿时间： | 1999-09-16 |
Deep Weathered Section Under Paleosols and Environment in Changwu of Shaanxi |
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| ZHAO Jing-bo.Deep Weathered Section Under Paleosols and Environment in Changwu of Shaanxi[J].Journal of Desert Research,2000,20(3):252-255. |
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| Authors: | ZHAO Jing-bo |
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| Abstract: | On the basis of the illuvial theory raised by the author, weathered and leached section identification in the field, CaCO 3 content, susceptibility and grain size analyses in laboratory, it was found that a deep weathered section under the fourth and the fifth paleosos had developed best since loess deposition. The weathered layer is 0\^3~0\^6 m thickness and it can be divided into two sublayers: the upper sublayer is weathered loess with ferruginous clay film and the lower sublayer is weathered loess without forruginous clay film. Macrocharacteristic is that leached vertical cracks developed in weathered loess and loess exists in the form of lumps of 20~40 cm in diameter from weathering. The low CaCO 3 content about 1% shows that the loess layer was affected by leaching on which overlying paleosol developed. The susceptibility value of weathered loess is between 40 and 60 (10\ \{-6\}SI)and is less than that of paleosol, but bigger slightly than that of unweathered loess layer, which indicates weathered loess layer was affected by the temperature under which overlying paleosol developed. Grain size, microtexture and susceptibility of weathered loess are similar to that of unweathered loess layer, which indicates it doesn't belong to the component of paleosol. Low CaCO 3 content and a lot of leached cracks in weathered loess layer demonstrate it doesn't belong to normal loess layer and is deep weathered residual layer formed when weathering exceeds the range of soil formation zone. There is not illuvial layer of CaCO 3 under the paleosol above weathered loess layer, but illuvial layer of CaCO 3 can be seen at the bottom of weathered loess layer, indicating that the illuvial layer of CaCO 3 has removed away from paleosol. This kind of illuvial layer of CaCO 3 doesn't belong to the component of paleosol, which shows richer rainfall and strong leaching. That the fourth and the fifth paleosols are middle or acid leached forest soils can be determined in the light of deep weathered loess layer and illuvial layer of CaCO 3 removed away from paleosol as well as ferruginous clay film in deep loess layer in Changwu area. When the two paleosols developed the depth of leaching and weathering not only was bigger than that of modern soils in same area, but also bigger than that in the southeast part of Loess Plateau. The development of deep weathered section is possibly because subtropical climate migrates to the middle part of Loess Plateau, and it represents climatic event with rich rainfall when the average annual rainfall was about 900 mm. |
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| Keywords: | loess weathered section leaching in deep loess rain event |
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