北京怀柔地区第四纪下限的综合标志

本文运用综合分析的方法,从岩性、古地磁、古生物、矿物及化学成分等方面,对北京怀柔地区HR88—1钻孔剖面进行了系统研究。认为HR88—1钻孔所揭露的新生代沉积物可划分为4个岩性段。第三与第四岩性段的界线即为N/Q界线,该界线位于孔深370m处。由于M/G界面位于358.5m深处,故确认N/Q界限时代约为2.50MaB.P.,将孔深370m以下的红色沉积物划归上新统,其上的杂色沉积物划归更新统。

COMPREHENSIVE CRITERIA FOR THE N/Q BOUNDARY IN HUAIROU AREA , BEIJING, CHINA

The Cenozoic strata are fairly developed in Huairou area . Since 1988 a lot of useful work has been done and a good deal of information has been gained . In order to use the comprehensive method to identify the N/ Q boundary , we have systematically analyzed the lithology , heavy minerals , clay minerals ,pollen and spore , palaeomagnetic polarity of sediments in the borehole HR88 -l,many other materials are also concerned in this paper. The authors believe that the Cenozoic sediments uncovered in the borehole. HR88 - 1 can be divided into four members . The boundary between the third member and the fourth one is thought to be the N/Q boundary which lies at the depth of 370m from the ground surface . The geological time of the boundary is about 2.50MaB . P . because the bound of Matuyama reversed polarity zone and Gauss normal polarity zone is situated at 358.5m deep . According to this division , the red sediment under 370m deep belongs to Pliocene , and the sediment with multicolors above 370m deep belongs to Pleistocene .