In 1979

we suggested that pliocene-pleistocene boundary in Beijing plain

based on the results of seismological and geological research

may be placed between the Pliocene Shunyi Formation and the Pleistocene Xiadian Formation

deter about 2.43 m.y.B.P. Since then

we have studied more cores

measured their CaCO

3

content and thermolumlnescene; Micratektltes from the Zhnili Formation

insecte fossils of Diptera from the Xiadan Formation of well No

l in Shunyi have also been discovered. These are sound evidurces for the subdivision of Quaternary and the determination of its lower boundary in this area.