珠江三角洲全新世环境演变

本文根据23个钻孔的约200个岩芯样品和6个露头剖面的20个样品的孢粉分析,划分了11个孢粉带和8个亚带以及相应的气候期。以多种喜热与喜凉植物孢粉含量的比值作为温度变化的半定量指标,绘成珠江三角洲全新世气候变化半定量曲线,并用历史时期气候记载检验该曲线。认为存在多次约1000a 尺度的气候变化。用107个已测年的古海面标志物绘制了珠江三角洲全新世海平面变化曲线,并用古文化遗存的性质和区域分布检验该曲线。初步认为,气候曲线与海平面变化曲线有较好的对应关系。海平面升降是本区环境演变的主导因素,并制约先民的生产和栖息。

HOLOCENE ENVIRONMENTAL CHANGES IN ZHUJIANG DELTA

According to the sporo-pollen analysis of about 200 samples from 23 bore holes and 6cropping sedimental sections,11 sporo-pollen assemblage zones and 8 subzones are distinguish-ed.(1) Of Early Holocene,the climate is warm and moist during early period,cool and dryduring late period.(2) Of Middle Holocene the climate is hot and moist during 7500—6500 aB.P.,slightly hot and slightly moist during 6500—5000 a B.P.,warm and moist during 5000—4500 a B.P.,burning hot and very moist during 4500—3400 a B.P.,slightly hot and slightlymoist during 3400—2900 a B.P.,hot and moist during 2900—2500 a B.P.(3) Of Late Holo-cene,the climate is burning hot and moist during 2500—1600 a B.P.,hot and moist during1600—1000 a B.P.,hot and moist during 1000—400 a B.P.,slightly hot and slightly moistsince 400 a B.P.Using the ratio of 14 tropical and south subtropical xylophyta species to the content of 5northern subtropical and temperate species as a semi-quantitative index,the ratio of hot to coolis calculated.By the same way,the ratio of moist to dry is obtained counting of moist speciesand dry species.Based on dating data,the habitual stage of Holocene and the sedimentationrates,the ages of sample are calculated.The semi-quantitative curve of climate change isdrawn logarithmically.Being compared with the archaeological and historical climate re-cords,it is believed that the curve is mainly reliable.107 markers of paleo-sealevel with dated ages are classified into 9 types.Zhujiang Deltais divided into 8 neotectonic districts,each district is divided into 2—3 sub-districts,and ineach subdistrict the rate of neotectonic uplift and subsidence is determined.Being rectified bysedimentation depth and neotectonic rates,the curve of sea-level is drawn.It is shown that thesea-level rose rapidly with a rate of 11 mm/a during 8000—6000 a B.P.,and reached the firstheight around 6000 a B.P.,after that the sea level undulated in 1—2m around the presentlevel,the crests occurred respectively around 5000,3700,3000—2600,2000—1800,1500—1300,1100—900 a B.P.,especially 3000—2600,2000—1800 a B.P.,the sea level is about1.5m higher than present.According to the analysis of hundreds Neolithic cultural relics,it is believed that those re-lics have close relation to the sea level changes.Sea level change is a leading factor in environ-mental evolution in Zhujiang Delta,it restricts the ancestor's production and life.The sea lev-el curve is mainly identical with the climate curve,a rise in sea level is generally accompa-nied by a rise in air temperature.