潮汕平原近五万年来的孢粉植物群与古气候

POLLEN FLORA AND PALEOCLIMATE OF THE CHAO-SHAN PLAIN DURING THE LAST 50000 YEARS

As a deltaic area of the Hanjiang and Rongjiang Rivers, the Chao-Shan Plain initiallyformed in Late Pleistocene (about 70 000 yrs. B. P.). The Quaternary continental,transitional and marine deposits may reach 70m in thickness. Palynological studies on a large number of cores from the Chao-Shan area show a se-ries of vegetational and climatic changes. Nine pollen zones are recognized from the portionof Late Pleistocene, among which Zones P8 and P2 represent relatively cold climate charac-terized by the presence of numerous deciduous trees (in particular Fagus) and conifers,while Zones P7--P3 with many tropical and mangrove elements indicate hot and dampclimate. The first marine transgression beginning at about 43 000 yrs. B. P. corresponds tothe gradual warming of the climate. Since that time, the sedimentary environment changed from terrestrial to deltaic and marine facies. A drop in the temparature occurred about28 000 yrs. B. P. However, a large scale regression took place between 20 000 and 12 000yrs. B. P. The Holocene pollen zones (H1--H5) indicate a series of environmental changes,fluviatile type alternating with marine type. The mangroves rcoccurred extensively in thisarea at about 8 500 years ago, and the highest sea level occurred during the period between7 500 and 4 000 yrs. B. P.