【作者】 查小春；

【导师】 黄春长；

【作者基本信息】 陕西师范大学 ， 自然地理， 2005， 博士

【摘要】 全新世时期是人类文明迅速发展繁荣的时期,也是全球环境发生重大变化的时期。位于黄土高原东南部的汾渭盆地,是我国古代文明发源地之一,人类活动的古遗址分布广泛。深入研究遗址周围的黄土-土壤地层剖面,能够揭示汾渭盆地全新世环境演变和人类活动状况及二者间的相互作用关系。 本研究基于详细的野外考察,分别在汾渭盆地东部的运城盆地、关中盆地东部和西部古遗址周围选择了夏县DXF-N、华县NSC和武功HXZ三个典型的全新世黄土-土壤剖面。对黄土-土壤剖面进行了粒度、磁化率、地球化学元素、TOC和CaCO₃等环境代用指标的室内实验分析和测定。通过实验结果,以及全新世时期环境演变和人类活动的状况,揭示了全新世汾渭盆地面流侵蚀沉积事件和古洪水事件的发生规律,探讨了侵蚀加速问题。获得的主要结论为: 1.汾渭盆地东部运城盆地洪积扇前沿DXF-N黄土-土壤剖面的粒度特征分析表明,DXF-N剖面记录了四个面流侵蚀沉积事件;结合考古地层学、黄土高原已有的文化层¹⁴C年代数据和在DXF-N剖面发现的文化遗物,确定出这四个面流侵蚀沉积事件分别发生在11500～11000 a B.P.、3850～3300 a B.P.、2200～2000 a B.P.和1300～800 a B.P.。全新世初期11500～11000 a B.P.正是冰期结束、气候转暖的初期,大量降雨产生丰富的地表径流,在裸露、疏松的风尘堆积黄土上产生面流侵蚀;3850～3300 a B.P.夏商时期,人类农业耕作和聚落建设等活动对洪积扇地表的干扰加大,增强了地表径流侵蚀、搬运、堆积作用,引起了运城盆地洪积扇前沿面流侵蚀沉积事件的发生;2200～2000 a B.P.和1300～800 a B.P.在气候干冷的情况下,人类活动强烈地影响着洪积扇前沿地表,在自然侵蚀和人为侵蚀的双重作用下,加速了面流侵蚀沉积事件发生。 2.通过对关中盆地东部洪积扇缓坡地带的NSC黄土-土壤剖面粒度特征分析,结合考古地层学、黄土高原已有的文化层¹⁴C年代数据和在NSC剖面发现的文化遗物表明,在11500～8500 a B.P.早期和4000 a B.P.之后,NSC剖面记录了关中盆地东部洪积扇缓坡地带的面流侵蚀沉积事件。11500～8500 a B.P.早期正是冰期结束、气候转暖的初期,气候变化引起了面流侵蚀沉积。自4000 a B.P.之后的夏商文化以来,人类农业耕垦等活动对洪积扇地表的干扰促进了面流沉积过程,也引起了面流侵蚀沉积事件的发生;从3100 a B.P.开始,气候干旱,人类活动强烈地影响着当地的生态环境,加速了面流侵蚀沉积事件发生。自隋更多还原

【Abstract】 The Holocenewas the quick development and prosperity period of the mankind and mankind’s civilization, and was also the great change period of the global environment. The Fenwei basin, one of the prehistoric culture centers in China, lies in the southeastern Loess plateau. Studied the Holocene loess-palaeosol sequence, the information about natural environment evolution and mankind’s activity impact could be obtained.Based on the detailed field investigation in Fenwei basin, the three typical high-resolution Holocene DXF-N, NSC and HXZ loess-palaeosol profile were studied by the proxy climatic data of grain-size, magnetic susceptibility, TOC, CaCO₃ and geochemical elements. The results revealed the rule about the palaeoflood and sheet ersoion-deposit events. The main results are as following: peak value1. Analyzed from the particle-size characteristics in DXF-N loess-palaeosol profile in the front of palaeoalluvial-pluvial fans in Yuncheng basin., and integrated with the archeology, the ¹⁴C age data in loess plateau and the cultural remains found in DXF-N profile, the results showed that the 4 sheet erosion-deposit events were recorded in DXF-N profile in 11500 a B.P. 11000 a B.P., 3850 a B.P.³300 a B.P., 2200 a B.P.²000 a B.P. and 1300 a B.P. 800 a B.P.respectively. The first sheet erosion-deposit event in 11500 a B.P. 11000 a B.P. arose from the climate change, because the temperature risen, a great deal of rainfall caused easily erosion on the bare, loose dust loess deposition. Since Xia and Shang dynasties from 3850 a B.P, mankind activities disturbed the the process of erosion, movement and deposition was advanced, and caused the sheet erosion-deposit events. Under the condition of the dry and cool weather in 2200 a B.P.²000 a B.P. and 1300 a B.P.—800 a B.P, the mankind activities moer strongly disturbed the palaeopluvial-alluvial plans, the sheet erosion-deposit events were accelerated.2. The NSC loess-palaeosol profile lies in the gentle slope ground between Shidihe river palaeoalluvial-pluvial fans and sourthern Weihe T₂ terrace in eastern Guanzhong plain. Analyzed from the particle-size characteristics, and integrated withthe archeology, the ¹⁴C age data in loess plateau and the cultural remains found in NSC profile, the results showed that the sheet erosion-deposit events were recorded in NSC profile in 11500—8500 a B.P.early and after 4000 a B.P., the sheet erosion-deposit event in 11500—8500 a B.P.early just took place in the early when the ice age end toward climate warm, the climatic change caused this sheet erosion- deposit event. Since Xia and Shang dynasties after 4000 a B.P., the human agricultural cultivation activities affected the surface of palaeopluvial-alluvial fan and promoted the slope runoff erosion and deposit process, which caused the sheet erosion- deposit event. Beginning from the 3100 a B.P.. the climate became dryer, but the human activities affected strongly the local eco-environment, and the sheet erosion-depositions events were accelerated. After Sui and Tang dynasties, the intensity of sheet erosion was intensified caused by the human activities.3. Analyzed from the particle-size characteristics, and integrated with the archeology, the ¹⁴C age data in loess plateau and the cultural remains found in HXZ profile, the results showed that the 3 palaeoflood events took place in in 5000 a B.P., 4200 a B.P.⁴200 a B.P. and 3100 a B.P.³000 a B.P.. The palaeoflood in 5000 a B.P. caused mainly by the climatic change from the climate acute fluctuation to the warm and wet. And the palaeoflood in 4200-4000 a B.P. was caused by human activities under the condition of warmer and wetter climate. Because of the instable climatic system after 3100 a B.P., the concentrative rainstorm and human stronger activities caused a paleaoflood event in 3100a B.P.³000 a B.P.. Based on the erosion velocity of Qishuihe river, the river bed gradient and coarseness coefficient, the flood flux of three palaeoflood events in 5000 a B.P., 4200⁴000 a B.P. and 3100 — 3000 a B.P. was 1190 m³/s, 2240 m³/s and 4030 m³/s figureed out respectively according to the current riverbed section counter-rose, and was 1280 m³/s, 2360 m³/s and 4260 m³/s figureed out respectively according to the current Qishuihe riverbed section shrunk by 30%, 25% and 20% because of the erosion velocity and human activities, which could provide reference for the Qishuihe river flood research.4. The acceleration erosion caused by mankind’s activity developed gradually, which experienced a very long historical development process. In the early Holocene. the soil erosion was caused by natural factors because of the weak intensity of mankind’s activity, the soil erosion belonged to natural erosion. The impact of mankind’s activity on soil erosion has began before 4000 a B.P., but the intensity was更多还原