中国东部第四纪冰期气候与环境的基本特征

ON BASIC FEATURES OF CLIMATE AND ENVIRONMENT IN QUATERNARY GLACIAL PERIOD IN EASTERN CHINA

本文根据近期获得的一些资料,认为中国东部第四纪冰期气候与环境比较特殊.冰期气温下降达10°—17℃以上,风的作用比较强盛,因而冰期风积物的发育比较普遍.还因为冰期海面的大幅度下降,曾引起中国东部的河流强烈下切,形成被埋藏的深槽.最后还提出中国东部第四纪历次冰期的气候与环境是有差别的,中国东部山地在早—中更新世冰期有可能曾出现过与现代山地冰川不一样的冰川活动.

The climatic and environmental features in Quaternary glacial period in eastern China may be summarized as follows: (1)The drop of temperature was relatively striking in the world. Based on the analyses of periglacial features, loess accumulation and biofossils etc., mean annual temperature in the glacial period may have been 10 to 16 lower than now in Huabei area, about 17 lower in the mid-lower Changjiang River area. During the last glacial maximum, winter temperature in the littoral area of southern China may have been 11 to 15 lower than now, and the surface water temperature in winter in the northern South China Sea may have been 3.5 to 6 lower than now. These facts have shown very great horizontal displacement of the climatic belts in eastern China in the glacial period. (2)Rivers in eastern China have a deeply incising ability in the glacial period so that the buried paleochannel trough were formed in the valley. The bottom of the paleochannel which developed during the last glacial maximum has reached a depth of -60m at the north of the present Changjiang's debouch, and a depth of -62 to -75m in the Zhujiang River mouth area. In some of the mid-lower reaches of large rivers it was about 20m deeper than present river bottom. The development of the paleochannel trough resulted from the drop of the world sea-level in Quaternary period. (3)Wind action was very strong in the glacial period so that eolian depo-sits were generally developed in eastern China. In Huabei area there are eolian sand and loess formed since the beginning of Quaternary. In the mid-lower Changjiang River area there are eolian loess formed since middle Pleistocene and dunes formed during the last glacial maximum. In the littoral area of southern China and on some islands of South China Sea there are coastal dune field and sand drifts formed during late Pleistocene glacial period. The ancient wind field in the glacial period in eastern China was close to present cold wave. It should be noted that, based on our analyses, the climate and environment in the glacial period in eastern China were largely different from early to late Pleistocene. The southward-spreading cold anticylones, which originated in the Arctic Ocean, Siberia, and Mongolia, increased step by step in both strength and frequency. Hence it is not impossible that the glaciation had occurred on the mountains in the mid-lower Changjiang River area in the glacial period of middle Pleistocene. But, it was characterized by extremely low temperature and dry in the glacial period of late Pleistocene.