| 关中平原420-350 ka BP的古土壤与环境 |
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| 引用本文： | 赵景波.关中平原420-350 ka BP的古土壤与环境[J].地理学报,2005,15(1):115-122. |
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| 作者姓名： | 赵景波 |
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| 作者单位： | 陕西师范大学地理系,西安,710062;中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,西安,710075 |
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| 基金项目： | 国际地质对比计划;教育部科学技术研究项目;国家重点实验室基金 |
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| 摘 要： | 通过对关中平原双竹村剖面、寇家坡剖面以及蓝田田家坡剖面、三官庙剖面、长安四府村剖面和宝鸡马家塬剖面黄土沉积中第4层古土壤的分析，发现西安、长安、蓝田和宝鸡中更新世中期发育的第4层古土壤已转变成为风化壳，厚度变化在3．5～3．7m之间。它由4层组成，最上部的第1层是发育好的红棕色粘化层(Bts)，第2层是具有铁质胶膜的风化淋滤黄土层(Cs)，第3层是不含铁质胶膜的风化淋滤黄土层(Cl)，第4层是CaCO3结核层(Ck)。对风化剖面中CaCO3含量、pH值、黏土含量，元素Sr、Fe2O3和Al2O3分析，表明该风化剖面受到了较强烈的风化淋溶和黏土化作用，并指示当时的风化淋滤深度明显超出了土壤粘化层的厚度。粘化层中黏土胶膜具亚热带土壤胶膜特征，具超微晶粒结构，由新生的蒙脱石、高岭石和伊利石微晶粒构成，明显定向排列，这是其具有光性的原因。风化壳型古土壤的发育表明，在距今42．35万年前后，黄土高原东南部盛行亚热带气候。这一古土壤剖面构型为Bts-Cs-Cl-Ck-C，它发育时的年平均温度和降水量分别约为16℃和1000mm，比现代关中平原高约30℃和400mm。
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| 关 键 词： | 关中平原 古土壤 风化壳 气候迁移 气候分界线 |
| 收稿时间： | 2003-06-07 |
| 修稿时间： | 6/7/2003 12:00:00 AM |
Desert-steppe migration on the Loess Plateau at about 450 kaBP |
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| ZHAO Jingbo.Desert-steppe migration on the Loess Plateau at about 450 kaBP[J].Acta Geographica Sinica,2005,15(1):115-122. |
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| Authors: | ZHAO Jingbo |
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| Institution: | 1. Department of Geography, Shaanxi Normal University, Xi'an 710062, China;
2. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS, Xi'an 710075, China |
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| Abstract: | The fourth paleosol (S4) which had changed into a residuum of the Brunhes Epoch (780,000 yr BP) at Shuangzhu in Chang'an, Koujiapo in Xi'an, Tianjiapo in Lantian and Hejiacun in Baoji developed over about 40 ka years. It consists of 4 horizons, the 1st one (uppermost) is a well developed reddish brown clay horizon (Bts), the 2nd is a dark yellowish brown weathering-cracked loess horizon (Cs) with red ferruginous clay films, the 3rd is yellowish brown weathering-cracked loess horizon (Cl) without the red ferruginous clay films, and the 4th is CaCO3 nodules horizon (Ck). In the Bts horizon, CaCO3 was leached away, Sr being trace element moved obviously and reached Ck horizon located at the bottom of the weathered profile, which indicates depth affected by weathering-leaching surpassed that of the Bts horizon and reached the lower boundary of the Cl horizon. In the Bts horizon, Fe2O3 and Al2O3 removed intensely also and into Cs horizon. In the weathered profile consisting of Bts, Cs and Cl, pH values are low, clay content is high, and Fe2O3 and Al2O3 were formed, which shows intense chemical weathering took place. The development of the fourth paleosol as a residuum suggests that a moist subtropical climate prevailed 420,000-350,000 yr BP in the southern part of the Loess Plateau in China. Its profile is Bts-Cs-Cl-Ck-C. When the paleosol developed, mean annual temperature and rainfall were about 16oC and 1000 mm respectively, about 3oC higher and 400 mm more than those at present in the Guanzhong Plain. |
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| Keywords: | the Guanzhong Plain paleosol residuum subtropical climate climatic boundary |
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