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SOME REMARKS ON THE NANGOU COLD PERIOD BASED ON THE ANALYSIS OF THE POLLEN FROM THE NIHEWAN STRATUM

Zhou Kunshu Liang Xiulong (Institute of Geology,Academia Sinica,Beijing)Yan Fuhua Ye Yongying (Institute of Geology,National Bureau of Seismology)  
In the Yangyuan Basin in northern Hebei Province and the Datong Basin in northern Shansi Province,400-500 meters of Nihewan deposits were accumulated.They are the deposits of a series of rivers and lakes.Since 1920's or 1930's,these deposits have been a famous stratum of the early pleistocene in China.We have made a special analysis of the spore-pollen contained in the deposits of the Nihewan stratum at Nangou,located about half a kilometer south of the Hongyan Village on the left bank of the Huliu River,a tributary of the Sanggan River.The Nihewan stratum is composed mainly of layers of graydark clay,sandy clay,and clayey sand above red soil of Pliocene,we discovered alternating evolution of paleovegetation from coniferous forests of Abies,Picca,Pinus to steppes of Artemisia,Chenopodiaceae (or lack of spore-pollen),and back to coniferous forests of Pinus,Picea and Allies again.This reflects the cycle of climatic changes since the transition of the Tertiary to the Quaterary from a cold moist to a cold dry,and then back again to a cold moist climate of a cold period that may be called Nangou Cold Period under the action of theclimate of the ice period.The average annual temperature then was about 3°--3℃,about 4°-10℃ lower than that of the present.The stratum,therefore,should belong to the early Pleistocene.In addition,vegetation of coniferous forests of Picea,Abies,and Pinus,and vegetation of steppes formed under cold climate conditions are discovered both between 208 to 223 meters,and 117 to 125 meters beneath the Datong Basin,and in the cross section of the ancient site of Xujiayao Man in the Yangyuan Basin.The former may belong to the Middle and the latter to the Late Pleistocene.So the 400 to 500 meters of the Nihewan deposits of the Datong and Yangyuan Basins contain the strata of all the periods of the Pleistocene.
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