北京周口店地区早更新世古冰楔遗迹的发现及其研究意义

THE DISCOVERY OF THE ICE WEDGE CASTS OF EARLY PLEISTOCENE IN ZHOUKOUDIAN AND ITS SIGNIFICANCE

In 1987, the authers discovered ice wedge casts in the strata with an age of 730-900 thousand years determined by palaeomagnetic dating on the north slope of Taipingshan Hill, Zhoukoudian, Beijing. The ice wedge casts are preserved in the clay bed of upper part of Taipingshan formation,and filled with clay. The deepest one of them is about 50 centimeters. Their palaeomagnetic age is more than 730 thousand years7and is determined by mammalian fossils.They are the oldest ice wedge casts so far discovered in China. Therefore,the fact indicates that there was a climate deteriorating event 730-900 thousand years ago. It is of important value in the study of palaeoclimate, palaeoenvironment and stratigraphy in that period.