摘要
在地球历史上,发生过气候的多次剧烈波动。与此同时,全球海面也曾经历过频繁的升降运动。引致海面升降的原因十分复杂,主要气候波动、地壳运动及大地水准面变形。气候波动直接影响全球水循环过程,从而控制着海洋中海水量的变化,因此是全球海面升降的关键。气候波动和海面升降运动具有不同的时间尺度及多旋回性。
There are still considerable different interpretations of the Holocene sea-level curves of different coastal regions of China.After separating the influences of tectonic and hydroiso-static movements we are able to construct a eustatic sea-level curve showing sea-level changes in the east coast of China over the last 20,000 years,because radiocarbon dates are available to establish a time scale over that period.The present paper tries to discuss the following major problems:1.Identification of sea-level fluctuations during the last 20,000 years.Based on the studies of more than 450 prehistoric sites,the distribution of radiocarbon dating of the shell middens and the sedimentological and micropaleotoloqical studies of more than 400 cores the present paper identified 10 intervals of sea-level oscillations(Fig.3)during the past 20,000 years.The time of sea-level fluctuations correlated exactly with the climatic variations of China(Fig.3,4).The radiocarbon dating of a sample taken at-155 meter on the shelf of the East China Sea indicates that it was deposited at 15,000 years B.P.After deducting the down sinking of the shelf owing to hydroisostasy of the melting water returning to the sea we inferred that lowering of sea-level was 106 m in 15,000 years B.P.2.Abrupt climatic variations and accompanied rapid sea-level fluctuations during the Late Glacial.Evidences furnished by sporo-pollen analysis of the Late Pleistocene and Holocene deposits of northern and eastern coastal plains of China indicate that three cold periods interrupted by two warm intervals obviously occurred during the Late Glacial(Fig.4).The temperature range between the cold period and the adjacent warm interval was around 6℃.Studies based on the paleoclimatic indicators and rate of deposition strongly suggest that the time interval when the warm Allerod dropped into the cold Young Dryas lasted less than 200 years.From 13,200 B.P.to 12,400 B.P.the temperature rose sharply 7℃while the sea level jumped from-83 to-35 m with the highest rate of 60 mm/a(Tab.1,Fig.4).It was the most rapid phase of sea-level rising experienced during the last 15,000 years.On the contrary,in 11,100 B.P.-10,900 B.P.occurred the most rapid phase of sea-level lowering which displayed a remarkable interruption of the tendency of sea-level movement during the Late Glacial.As revealed from drill cores in eastern China the sea level dropped abruptly from-26 to-33 m within 200 years at the beginning of the Woung Dryas.3.Climatic and eustatic changes during the Post Glacial period.Evidences from paly-nological studies in northern and eastern China indicate that since the beginning of the Ho-locene the climate has experienced four major cold phases,occurring around 8200 B.P.,5800 B.P.,3000 B.P.and 300 B.P.respectively.During each cold period the sea level lowered 2-4 m(Tab.3,Fig.4).As shown in table 3 and figure 4,during the warm intervals the sea level rose again and formed three major Holocene high sea levels which occurred at 10,000-8300 B.P.,8000-7000 B.P.and 6000-5500 B.P.4.Climatic and sea-level changes during the last 2000 years.Making full use of the long and rich historical records and the tree ring studies as well,we are now able to reconstruct both climatic and eustatic curves in great detail.In figure 5 we compare the climatic phases of China with the temperature variations of Europe for the last 2000 years.Eustatic fluctuations as shown in figure 5 indicates that high sea-levels occurred in the fourth,ninth and sixteenth centuries with the maximum oscillation amplitudes of more than 2 meters.It is noticeable that the synchronous relation between climatic and sea-level fluctuations not only existed with the time scale for 103 years but also for 101-102 years.We find that the climatic and eustatic curves of China from 1890-1970 coincide very well.
作者
杨怀仁
谢志仁
Yang Huairen;Xie Zhiren(Nanjing University)
出处
《海洋与湖沼》
1984年第1期1-13,共13页
Oceanologia Et Limnologia Sinica
