【作者】 郝玉芬；

【导师】 赵景波；

【作者基本信息】 陕西师范大学 ， 自然地理学， 2004， 硕士

【摘要】 全新世环境演变研究在全球变化研究中占据重要的地位。全新世是地球历史最新的一页，现代气候是全新世气候的延续和发展。最近二十多年来，国外国内的地学界都十分重视全新世的研究，深入了解和探讨全新世气候演变规律、各阶段气候特点、有关气候事件的性质和发生原因对认识现代气候形成、灾害发生规律以及预测未来气候既有重要的科学意义又有重要的实际意义。近年来，全新世成壤环境演变研究成为研究的热点和重点之一。深入了解和探讨全新世成壤环境演变规律，认识土壤类型具有重要的现实意义。因此，本文从成壤环境变化的角度探讨黄土高原中南部全新世环境演变。 通过大量的野外考察，选取了黄土高原中部的洛川城东剖面和南部的临潼王庄剖面。两剖面地层稳定，发育连续、完整，保存良好，具有典型性。对两剖面从上往下每隔2.5cm间距采取样品，洛川城东剖面采样94个，临潼王庄剖面采样81个。 本文对研究剖面磁化率、粒度、CaCO₃、土壤微结构、pH值进行了分析测定，获取了比较丰富的全新世成壤环境演变数据资料。剖面中高分辨率的磁化率变化，指示了受东亚季风控制的年降水量变化；各粒级组分含量在黄土剖面中的变化反应了季风强度的长期变化，粒度中50～10μm粗粉沙、小于5μm粘粒含量的变化指示东亚季风所控制的成壤强弱变化；土壤微结构是判别土壤发育强弱、土壤类型的重要依据：CaCO₃和pH值可以作为探索大气降水或湿润程度的指标。 本文根据野外考察和以上实验分析结果，分析论证了黄土高原中南部全新世环境演变的基本规律，并对成壤环境演变进行了深入探讨，得出了如下结论： （1）洛川地区全新世中期发育的古土壤S₀分为上下两层（S₀¹、S₀²），古土壤S₀²的土壤类型应为干性森林条件下发育的典型褐土，年均降水量为700mm左右年均气温为13℃左右；古土壤S₀¹的土壤类型应为碳酸盐褐土，其发育时不具明显的森林植被，年均降水量为600mm左右，年均气温为11℃左右。 （2）临潼地区全新世中期发育古土壤S₀¹与S₀²相当于亚热带黄褐土，年均降水量为750mm左右，年均气温为15℃左右。表明在全新世大暖期秦岭南北两侧均为亚热带气候，当时秦岭已失去温带与亚热带气候分界线的作用。 （3）黄土形成时的沙尘暴活动比古土壤形成时要强的多。洛川地区全新世晚期黄土中强沙尘暴事件多达7次，而古土壤层S₀¹、S₀²中各为1次。沙尘暴的演化受轨道因素的控制，但也受百年至干年尺度的非轨道和突发性因素影响。 （4）在1 1500⁸500a B.P.之间的全新世早期，温度上升，降水量略有增加，为夏季风增强，冬季风减弱的时期。气候由寒冷干早向温暖湿润转变，沙尘攀开始减弱，黄土堆积速率显著减慢，成壤作用逐渐加强，后期有洪水发生。 （5） 8500⁶O00aB.P.为全新世中期温度最高、降水量最大的最适宜期，夏季风强度达到最大，沙尘暴偶有发生，土壤发育最为强烈。6000^S000a B.P.为全新世中期的气候恶化期，夏季风减弱，冬季风增强，沙尘暴活动频繁，风成黄土堆积，降水减少，成壤作用明显变弱。5000一3 IO0a B.P.为温湿气候回返时期，夏季风增强，冬季风减弱，降水量增多，成壤作用变强，沙尘暴活动微弱。 （6） 3100a B.P一今为全新世晚期，季风转变，夏季风减弱，冬季风增强，气候干旱化，沙尘暴最为频繁，土壤退化，形成了现代黄土层L。和表土层TS。更多还原

【Abstract】 Study on the Holocene environmental change occupies the important status of studying on global change. The Holocene period is the last stage of Human history. In resent years, Study on the Holocene Environmental Change of Pedogenensis has become focus and focal points. So the author selects the relationship between the Holocene environmental change and the pedological process as the topic of the thesis.Two Holocene loess profiles have been found in the middle and south Loess Plateau. They expose fresh steep bank. And they can be observed that the sediments of the Holocene loess are continuous and thus they reflect the environmental change since the Holocene. On the basis of outdoor observation and indoor experimental analysis, the author selects proxy substitute indexes, such as grain-size, magnetic susceptibility, soil micromorphology, CaC03 and pH value, etc. Through the comparison study of these climatic substitute indexes, the thesis reveals the process of the change of climatic environment in Holocene in the middle and south Loess Plateau. Finally, the thesis investigates the relationship between the Holocene environmental change and the pedological process.This thesis draws the following conclusion:(1) Two layers of soil (S01 and S02) in the Middle Holocene were formed in Luochuan region. S02 should be typical cinnamon soil. The annual pre -cipitation reached about 700mm. The annual temperature reached about 13 ℃. S01 should be carbonate cinnamon soil. The annual precipitation reached about 600mm. The annual temperature reached about 11℃.(2) Two layers of soil (S01 and S02) in the Middle Holocene were formed in Lintong region. They should be subtropical yellow cinnamon soil. The annual precipitation reached about 750mm. The annual temperature reached about 15℃. In the Middle Holocene, two sides of the Qinling Mountains bothwere subtropical climate, and the Qinling Mountains had lost the function as the boundary between temperate zone and subtropical zone.(3) Dust storms in Loess period were much stronger than in paleosol period. In the Holocene, about 7 extraordinary dust storms in the Loess (Lo) have happened, but only 1 extraordinary dust storm in each layer of soil. Dust storms must have been impacted by the orbital factors, and by other unorbital and paroxysmal factors on the scale of hundred to thousand.(4) 11500~8500a B. P., Summer monsoon was stronger and winter monsoon weaker. Therefore, temperature went higher gradually and precipitation got more, dust-storms weakened, pedological process was becoming strong slowly. There were flood sediments in the layer in the later period.(5) 8500~6000a B. P., Summer monsoon reached its maximum, pedological process was the strongest, dust-storms nearly didn’t happen. Precipitati -on increased remarkably, so was temperature. 6000~5000a B. P., This is a period of climatic deterioration. Summer monsoon was weaker and winter monsoon stronger. Precipitation and temperature decreased mostly, and eolian dust deposition was accelerated. Dust storms became stronger. Pedological process weakened obviously. 5000~3100a B. P. , Summer monsoon was stronger and winter monsoon was weaker. Temperature raised and precipitation increased. Dust storms weakened, and pedological process was becoming strong.(6) Since 3100a B. P., In this period, climate deteriorated again. Summer monsoon was weaker and winter was stronger. A layer of Loess has been accumulated since then. Dust storms were the strongest.更多还原