南海北部深海花粉记录的环境演变

本文报道了南海北部深海沉积物中花粉的研究结果。所研究的17940孔长13．30m,包括最近4万年的沉积物。共鉴定统计103个样品,样品间距10cm,分辨率约为360a,自下而上分为3个花粉带和8个亚带。P1带(13．06～8．70m,约37000～15000aB．P．)以山地针叶树(Picea,Abies,Tsuga)花粉高含量组合与蒿属花粉占优势组合交替出现为特征,指示冷湿及温干频繁交替的气候。根据氧同位素资料该带相当于3期及本次盛冰期。P2带前期(P2-a亚带,8．70～7．23m,约15000～11300aB．P．)热带-亚热带常绿阔叶乔木花粉增加指示气候变暖,其中14000aB．P．前后红树林的高峰可能是海平面一度上升的结果；P2带后期P2-b亚带(7．23～660m,约11300～10000aB．p．)高山雨林及山地针叶树花粉增加指示气候变冷。根据氧同位素资料P2－a亚带与Bφlling－Allerφd升温期相当,而P2－b亚带属新仙女木期。P3带(660～0m,10000aB．P．至现在)为全新世,花粉组合以松属花粉占绝对优势,与现代南海北部表层沉积物中花粉组合相似,说明近万年以来南海北部气候与现代气候相近。近1400年来芒其孢子突然增加说明人类活动加剧。

ENVIRONMENT CHANGE FROM POLLEN RECORD IN DEEP SEA CORE FROM NORTHERN SOUTH CHINA SEA

This paper presents the palynological record of a deep sea core 17940 from the South China Sea （20°07' N, 1 17°23' E, water depth of 1 727 m）, and on the basis of Pollen data a vegetation and climate history for the last 37 000 years is reconstructed.During the Last Glaciation （zone P1, ca 37 000 15 000aB.P.）, the pollen assemblages are dominated by a large amount of herbaceous pollen and those of montane conifer associated with Anthoceros spores, suggesting that the exposed shelf was probably occupied by grassland, with montane conifers growing on nearby mountains. Therefore, the northern part of the South China Sea experienced a remarkable decrease both in temperature and humidity during the Last Glaciation. Strong fluctuations in Percentages with alternating predominance of pollen grains of montane conifer and Artemisia are also observed in the pollen diagram of mis Period, indicating the shifting of the vegetation pattern occurred several bines during that bine. As a result oscillations of relatively cold and moist （dominated by montane conifers） alternatively with temperate and dry climate （dominated by grassland with Artemisia） occurred. During deglaciation from 15 000 - 1 1 300aB. P. （zone P2-a）, tropical-subtrOPical broad-leaved taxa increased in pollen assemblages, indicating a rise of temperatUre. The δ 18O curve aso implies a climatic warming occurred during this Period. Therefore it might be comparable with the Blling-Aller d warm stage. From 11 300 - 10 000aB. P., the Percentage of tropical-subtropical broad-leaved taxa are suddenly decreased, due to the re-expansion of taxa of montane conifers and upper montane rainforests, implying a substantial drop of temperatUre but an increase in moistUre. Data from palynology and oxygen isotopes indicate that this event is closely correlated with the Younger Dryas event. DUring Holocene, pollen records are quite similar tO those of surface sediments from the northern South China Sea implying that the vegetation and climate during the last 10 000 years is similar to that at present.