关中盆地西部黄土台塬全新世气候事件研究

doi:10.13826/j.cnki.cn65-1103/x.2002.01.003

摘要/Abstract

摘要： 通过对陕西歧山黄土剖面地层学和土壤学研究, 磁化率、全铁、粒度、CaCO₃和TOC测定分析, 发现在全新世的全球性“大暖期”即将到来之前, 黄土台塬面有洪水发生。在全新世大暖期当中, 季风气候有明显的波动变化。尤其是在6000aBP前后季风气候转折, 形成了6000～5000aBP显著的干旱阶段。这使得全新世大暖期分裂成为两个主要的温暖湿润阶段。各项气候代用指标显示8500～6000aBP是大暖期中最为温暖湿润的时期。在大约3100aBP季风格局发生变化, 气候向着干旱化发展, 全新世的成壤期为黄土堆积期所取代。这些事实对于我们客观地评价半湿润-半干旱地区的季风气候对于全球变化的响应规律具有重要的科学意义。

关键词: 全新世, 洪水, 干旱, 土壤退化, 黄土高原

Abstract: More and more intensified dust storms and dust deposition currently over the Loess Plateau of China provideanalog for understanding the monsoonal climatic change and reconstruction of the Holocene environment in thissemiarid zone. T'hick profiles of the Holocene loess palacosol sequence were found on the Zhouyuan loess table-land in the western Guanzhong Basin, Shaanxi Province. Detailed stratigraphic and pedological observationswere made in the profile during the filed work. The fragments of the Neolithic cultural remains identified in theprofile provide chronological control in the sequence. Multi-disciplinary analyses, including magnetic susceptibili-ty, total Fe, grain-size and total organic carbon, carried out in laboratory show that Holocene climate has beenhighly variable in this environmental sensitive region. Several important climatic and hydrological events arerecorded in this Holocene profile. A flood phase was identified between 9 000~8 800 a BP (cal. ) during the dli-matic amelioration in the beginning of the Holocene. The flood was from the uplifted pediment of the BeishanMountains on the north. T'he Holocene Megathermal (climatic optimum) was identified between 8 500~3 100 aBP. during which policyclic cinnamon soils were developed on the loess tableland.An abrupt climatic shift fromhumid to dry conditions took place at about 6 000 a BP, therefore, a remarkable climatic aridity phase was foundbetween 6 000~5000 a BP. The Holocene Megathermal (climatic optimum) was thus split into two main peri-ods (8 500～6 000 a BP and 5 000~3 100 BP) with warm wet climate. T'he earlier period was more intensivein its climatic warmness and humidity. This means the Holocene Megathermal was not constant and stable asthought in the past. Another climatic shift was identified at about 3 100 a BP. The increase in climatic ariditysince then has caused intensified dust storms and acceleration of dust accumulation- Because of the largely decreased precipitation, the deficit soil moisture and intense dust deposit has thus caused soil deterioration on theloess tableland. At the present, a layer of about 0.5~～O. 8 m thick loess has blanketed the landscape on the loesstableland. The present ploughed topsoil is only the top part of this recently accumulated eolian loess sediment. This topsoil is rather poorly developed compared with the Holocene palaeosol So in the middle part of the profile. These results are very important for underst anding of the regional response to global change in the semi humid tosemi-arid zone within the middle reaches of the Yellow River drainage basin.

Key words: Holocene, floods, climatic aridity, soil degradation, Loess Plateau

中图分类号:

P532

黄春长, 庞奖励, 黄萍, 侯春红, 韩宇平. 关中盆地西部黄土台塬全新世气候事件研究[J]. 干旱区地理, 2002, 25(1): 10-15.

HUANG Chun-chang, PANG Jiang-li, HUANG Ping, HOU Chun-hong, HAN Yu-ping. HOLOCENE CLIMATIC EVENTS ON THE LOESS TABLELAND IN THE WESTERN GUANZHONG BASIN, CHINA[J]. Arid Land Geography, 2002, 25(1): 10-15.

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