【作者】 刘昆；

【导师】 黄春长；

【作者基本信息】 陕西师范大学 ， 自然地理学， 2004， 硕士

【摘要】 全新世是地球发展史中最新的一页，它是与人类古代社会发展和现今自然环境最有直接联系的一个地质时期。全新世距今时间最近，与人的关系最为密切，是人类从愚昧走向文明的时期，是环境演变与人类社会的发展互为因果融为一体的时期。因此，从对人类社会的影响来说，全新世的环境演变具有特别重要的意义。深入研究全新世气候演变的过程、性质和发生原因，特别是对土壤成壤环境的演变规律研究，对认识现代环境的形成，揭示人类文明对自然界的影响和预测未来的地理环境有重要意义。 土壤是自然环境的主要构成因素，是气候变化的重要指示物。各区域土壤剖面的发育程度强弱，在很大程度上反映了各区域历史时期气候变化的状况，所以本文研究的目的是通过对全新世发育的土壤剖面的理化指标研究，试图从成壤环境角度，探讨全新世不同地貌条件下土壤的成壤变化规律，并在此基础上揭示该区域全新世气候的变化过程、环境的演变规律、Rainwash事件面流沉积物对土壤成壤的过程影响以及人类活动对成壤环境的影响，为认识黄土高原现代土壤侵蚀和人与自然之间的关系提供一定的科学的参考。 通过大量的野外考察，本研究选取了渭河盆地二级阶地的SLC剖面（含西周文化遗物），汾河盆地的河流阶地和山前洪积扇上的TSC、DPG、DXF-S剖面（含陶寺文化遗物）。上述剖面地层稳定，发育连续完整，保存良好，具有典型性。对剖面自上而下每隔2 cm进行高密度采样。分别采集到125、155、140、205个全新世地层样品。对这些样品进行了磁化率、粒度、及CaCO₃含量的室内分析。 采用土壤—古土壤序列与替代指标分析相结合的手段初步恢复了全新世汾渭盆地地区的全新世气候演变过程，同时借用现代土壤侵蚀理论对区域内部的成壤差异进行了分析。 通过本课题的研究，对汾渭盆地全新世成壤环境演变得到以下结论： （一）全新世地层CaCO₃淋溶淀积过程不同。由于不同地貌类型的影响，使得剖面上的沉积物受到侵蚀、搬运、并在低洼处形成新的沉积。这使特征相似的剖面，产生了不同的淋溶淀积。本地区在全新世全球变化的气候条件下，受地带性因素控制，一般来说愈往南部，剖面中CaCO₃淋溶淀积的强度和深度愈大，出现CaCO₃淀积层；受非地带性因素地貌和人文活动的影响，地形低洼和人文活动强烈的地方，剖面中CaCO₃淋溶淀积的强度和深度愈大，出现CaCO₃淀积层。反之，强烈的地方，剖面中CaCO3淋溶淀积的强度和深度愈大，出现CaCO。淀积层。反之，愈向北部CaCO3淋溶淀积的强度和深度愈小;地形起伏大和人文活动微弱的地方，CaCO。淋溶淀积的强度和深度愈小。 （二）地貌的差异，是产生面流侵蚀一沉积的根本原因，面流侵蚀是产生可溶性盐类淋溶淀积不同，成壤环境不同，剖面地层发育厚度巨大差异的驱动力。研究认为在整个全新世时期，土壤侵蚀过程存在四个强烈的时期，（1）11500一8500a B.P.之间，季风转变，出现的洪水侵蚀，为土壤侵蚀一堆积过程，侵蚀区在古洪积扇，沉积区在古洪积扇前沿和河流阶地上，阶地面沉积作用大于古洪积扇前沿，属于自然侵蚀。（2） 8500一4050 a B.P.之间，全新世的大暖期，降水丰沛，造成的面流侵蚀一沉积，侵蚀区在洪积扇中上部，沉积区在洪积扇前沿，属于自然侵蚀。（3）4050一3100 aB.P.之间，古洪积扇仍然为侵蚀区，古洪积扇前沿和阶地为沉积区，古洪积扇前沿沉积作用加强，该期侵蚀一堆积作用于人类活动有关，属于自然一人为双重侵蚀。（4） 3100一0 a B.P.，人为改变洪积扇前沿的地形，修建灌溉工程，使洪积扇上部侵蚀，在洪积扇前沿和阶地处沉积，属于自然一人为双重侵蚀。由此可见，现代黄土高原的土壤侵蚀是历史时期土壤侵蚀的延续和继承。 （三）全新世成壤环境变化过程在汾渭盆地内部表现的有所不同。全新世早期成壤加强，中期增加到最大，晚期开始退化。在11500一8500 a B.P.的全新世早期，地层为L:，气温开始回升，降水量略有增加，夏季风增强，冬季风减弱时期。气候由寒冷干旱向温暖湿润转变，沙尘暴明显减少，黄土堆积速率减慢，成壤作用加强。各剖面成壤作用的差异开始产生。8500一3100 a B.P的全新世大暖期，地层表示为S。，夏季风达到最大，气温达到最高，降水量显著增加，土壤发育强烈。但是由于气候、地貌和人类活动因素的影响，成壤环境的差别扩大，因此成壤强度不同。3100 aB.P一现今的全新世晚期，季风转变，夏季风减弱，冬季风增强，气候干旱化，沙尘暴频繁，土壤退化，形成了现代黄土L。和表土TS，成壤环境差异缩小。研究发现，在全新世大暖期，渭河流域和汾河流域的成壤环境在拉大，而在黄土堆积时期，这种差距在缩小。 本文首次引用土壤侵蚀理论来解释全新世土壤成壤环境的演变，揭示了土壤侵蚀对壤环境的影响，充分证明，成壤环境变化是多要素共同作用的结果，不仅仅是受气候条件影响，而且还受到了其他成壤因素的影响。由于首次使用侵蚀理论来解释全新世成壤环境的演变。因此存在着对侵蚀理论认识水平较低和定量化说明不够等不足之处，有待于以后深入的探讨和研究。更多还原

【Abstract】 Abstract: The Loess Plateau is well known to the world for it’s thickness of larger of loess. The Holocene layer of loess and palaesoil sequence in the Loess plateau consitutes excellent records of evolution of soil formation, change in monsoon, dust-sand storm accumulation and influence of human cultivating over 8500 year.In the study, four typical Holocene soil profiles in the Weihe and Fenhe River Basin were studied by field investigation and using high-resolution analysis of magnetic susceptibility, the content of CaCO3 and grain-size analysis. The results comparied study of these climatic substitute indexes reveal the relationship between the process of soil formation and the change in monsoon climate, and different physiognomy term in the region. The study provides new science basis to instruct human activities in this climatically sensitive semiarid zone. The main results are following by Comparative Studies :(1) The different progress of eluviation and illuviation of CaCO3 in the stratum of Holocene. Because of the impact of different physiognomy term, sediment of profile was eroded, conveyed and deposited in the low-lying place, which made the profiles have resemblingly character engender different kinds of eluviation and illuviation.(2) The different physiognomy term brought about surface erosion, which is the drive force that formed different eluviation and illuviation of CaCO3, different pedogenic environment, the immense differentia of profile stratum of soil formation in Holocene. The study shows the soil erosion has never benn interrupted, only but different intensity. Modern soil erosion is continuation and inheritance of historical soil erosion in the Loess Plateau. The intense soil erosion had occurred in the shift period of accumulation to pedogenesis. But soil erosion weakened in the transitional period of pedogenesis to accumulation, even though the impact of human acativitues.(3) The different variation progress of Pedogenic Environment were showed during the Holocene in the Weihe and Fenhe River Basin. 11500~8500 a B.P., summer monsoon was stronger and winter monsoon was weaker. Temperature went higher graduately, at the same time, precipitation got much, dust-sand storm weakened,but it was mainly still dry and cold. Pedological progress was becoming slowly strong, but there were corrasion and deposits in the dust sediments of late stage in the site of DXF-S profile. 8500-3100 a B.P., it was a period in which the temperature was the highest, the precipitation was the greatest, pedological progress was very strongest and summer monsoon reached its peak during the Holocene. There appeared human ’s culture. Precipitation increased ramakably in this period, but pedological degree was different due to different precipitation, different physiognomy term and impact of human activities. The data of magnetic susceptibility and the content of CaCO3 reflect that the palesol So in the Weihe River basin was far more matured that that in the Fenhe River basin. 3100 a B.P. to now, the climate began to deteriorate around 3100 a B.P. and soil degradation is recorded in the profiles. Summer monsoon was weaker and winter monsoon stronger. The layer of loess L0 has been accumulated since 3100 a B.P.. The climate trended to become dry and cold, the sand-dust storm intensified. Pedological progress hardly stopped, but there were corrasion deposits in the dust sediments of the profiles.更多还原