关中泾阳塬全新世黄土剖面磁化率的古气候阶段划分

Partition of the Palaeoclimate Stages in the Holocene on the Susceptibility of Loess in the Loess Plateau of the Jingyang,Guanzhong

通过对陕西关中地区泾阳南塬寨头村和泾阳县新庄村典型剖面全新世黄土-古土壤地层的岩性描述、地层划分和对比，结合泾阳县新庄村AMS^14C的年代测定和其他学者的测年数据，建立了该地区全新世以来黄土沉积年代序列。根据磁化率气候替代指标显示的曲线特征，这一替代指标在剖面上的变化规律以及该黄土剖面所反映的东亚冬、夏季风强弱变化特点，表明了关中地区的气候波动与中国西北地区及全球气候变化的总趋势具有一致性，全新世以来在全球变化背景下关中地区气候变化表现为气候演化的周期性、不稳定性和趋势性。进而对该剖面磁化率曲线特征与其他学者的孢粉谱建立的温度曲线对比，对关中地区全新世以来古气候的阶段性进行了详细分析和论证。将关中地区1万a以来的气候演变划分为7个气候阶段：第1阶段为10．0～9．0kaB．P．冷温转换的阶段；第2阶段为9．0～7．0kaB．P．暖冷波动阶段；第3阶段为7．0～6．0kaB．P．温暖阶段；第4阶段为6．0～5．0kaB．P．较温暖阶段；第5阶段为5．0～3．4kaB．P．暖冷波动阶段；第6阶段为3．4～2．0kaB．P．气温先降后升阶段；第7阶段为2．0kaB．P．至现在温暖半湿润、半干旱阶段。

By lithological description, classification and correlation of the Holocene loess - palaeosol stratum in typical sections of loess plateau in southern Zhaitou and Xinzhuang villages in Jingyang county, Guanzhong area of the Sannxi Province, and combined with the age determination of AMS14C and age data obtained by other scholars, the loess deposition age sequence of the studied area is established. Based on the character of the susceptibility curve, a substitution indication of ancient climate, the authors can expound the changing regularity of this substitution indication in the section. At the same time, the authors can make inference on the strength and changing character of the winter and summer monsoons in East Asian reflected by the loess section. The available evidence suggests that the fluctuation of the ancient climate in the Guanzhong area have the consistent trend with that in Northwest China and the globe. During Holocene, under the general global climate changing tendency, the climate evolu- tion of the Guanzhong area is represented by the nature of cycle, unstability and trend. The susceptibility curve of the section is also compared with the temperature curve reconstructed from sporopollen by other scholars. On the base of careful analysis and verification, the palaeoclimate stage features during the Holocene in the Guanzhong area are thoroughly discussed. Seven climate stages in most recent 10000 years have been suggested and they are. stage 1, 10.0 -9.0 kaB. P. , being a conversion stage when the climate turned from cold to warm; Stage 2, 9.0 - 7.0 kaB. P. , a frequently fluctuated climate stage; Stage 3, 7.0 6.0 kaB. P. , a warm phase; Stage 4, 6.0 - 5.0 kaB. P. , a mild warm stage; Stage 5, 5.0 -3.4 kaB. P., a turbulent, warm and cold alternated stage; Stage 6, 3.4-2.0 kaB. P. , a stage with temperature decreased at first and then increased and finally; Stage 7, 2.0 kaB. P. to present, a warm semi-humid and semi-arid stage.