SPATO-TEMPORAL DISTRIBUTION OF THE CRETACEOUS DESERTS IN CENTRAL AND EASTERN CHINA AND ITS CLIMATIC SIGNIFICANCE

The spato-temporal distribution of the Cretaceous deserts in central and eastern China is described in this paper.The conclusions are summarized as follows.
1.The distribution of the Cretaceous deserts in central and eastern China is mainly controlled by climatic zones within the extent of the Cretaceous dry climatic zones crossing the subtropical high-pressure zone (palaeolatitudes of 20—40°N) mainly in the Ordos, Sichuan,Jianghan and Subei Basins.
2.The deserts in various basins occur in different times.For instance,the desert appeared in the Ordos Basin during the Early Cretaceous;in the Sichuan Basin during the late Middle Cretaceous;in the Jianghan Basin during the early Late Cretaceous,and in the Subei Basin during the middle and late Late Cretaceous.
3.The diachronism of the desert initiation has revealed that these basins once entered the dry climatic zones in the following order;from north to south and from west to east.
4.This order is attributed to the clockwise rotation of the Asian continent during the Cretaceous,which permit the above-mentioned basins to enter the dry climatic zones in the following order:the Ordos Basin,Sichuan Basin and Jianghan Basin.The southward drift of the dry climatic zones caused by the catathermal events in the middle and late Late cretaceous made the lagged Subei Basin in the easternmost enter the dry climatic zones as the last one.
5.The existence of the Cretaceous deserts in China indicates that the general atmospheric circulations in the "greenhouse" period would not be "sluggish" but strengthened. The existence of the monsoon system also indicates that the climates were not equable at that time.
The concept of climatic zone drift is proposed in this paper.It is believed that the climatic changes are manifested in the climatic zone drift.The drift can be long or short period drift and relative or absolute drift.The temporal and spatial changes of the Cretaceous deserts in central and eastern China might be caused by the dry climatic zone drift at that time.