山东地区黄土沉积特征与环境意义及其与黄土高原的对比

黄土高原与我国东部地区等地广泛分布的第四纪以来的粉尘堆积,是古气候变化的良好记录。但是,将我国黄土堆积视为一个整体、从地质历史的角度来进行区域对比和定量分析粉尘堆积的动态过程及其驱动机制的研究较少。在系统的野外调查与地层对比的基础上,对末次冰期沉积的山东庙岛群岛长岛黄土剖面与宁夏中卫冰沟黄土剖面进行了样品采集,经彻底的前处理后,采用Malvern Mastersizer 2000激光粒度仪进行了粒度分析,结果表明两者在粒度特征上存在一定的相似性,但冰沟剖面粒度明显比长岛剖面粒度粗,在整个末次冰期的风成沉积中,冰沟剖面的中值粒径为48.23μm,而长岛剖面为28.36μm;冰沟剖面的砂粒的百分含量为52.34%,而长岛剖面仅为23.47%。两个剖面均记录了末次冰期可与反映全球冰量变化的SPECMAP曲线对比的阶段,尽管其反映的气候状况并不完全相同。两剖面所指示的环境意义可能也存在差异,冰沟剖面的粒度变化主要反映了古风场强度的变化和沙漠的进退,长岛剖面粒度变化除了指示古风场强度的变化信息外,还指示了粉尘源区环境的变化,在一定程度上还指示了海平面变迁的信息。

Sedimentary characteristics and environmental significance of Loess in Shandong area and comparison with the Loess Plateau during the Last Glaciation

Dust deposit is widely distributed in Chinese Loess Plateau,the eastern of China and other regions,and the aeolian sediments have been regarded as one of the most vigorous terrestrial records of paleoclimatic changes during the Quaternary.So far,a large number of investigations have been carried out on palaeoenvironmental changes.However,regional correlation,as well as the origination,transportation,and deposition of the eolian sediments,have not been well understood.In this study,two loess sections, Changdao loess section in Miaodao Islands of Shandong province and Binggou loess section in Ningxia Hui Nationality Autonomous Region,are decided as the representative loess sections in northwest China and eastern China.Comparative study is conducted from aspects of strata lithology,grain size,climate condition and its forming causes.The grain size were measured by laser particle sizer Malvern MasterSizer 2000,samples were pretreated by removing the organic matter and carbonate,and by heating with chemicals H2O2 and HCl,（NaPO3）6 was added and ultrasonic machine was used in order to fully separate the finer particles.The results indicate that there are some similar characteristics between the two deposits,but the mean grain size in Changdao profile is obvious larger than that in Binggou profile.It shows that median grain size（Md）average value in Binggou section is 48.23μm,the median grain size in Changdao section is 28.36μm during the last glacial.Whereas the sand contents（63μm percent）average values are 52.34% and 23.47%respectively in the two sections.These two sections all recorded the stages which could be compared with SPECMAP curve indicating the changes of global ice volume during the last glacial,thought there were some differences in climate conditions reflected by the records.Because the material source in Changdao profile is the sand in sandy beaches nearby.The grain size records in Binggou profile may imply that the strength of the winter monsoon winds and the expansion or contraction of the Tengger desert. Whereas the grain size records in Changdao profile not only imply the strength of the winter monsoon winds from high latitudes,but also imply the changes of environment of the material source and the information of the sea level change.