西藏扎布耶湖区128～1.4ka BP的微体古生物与环境气候变化

本文主要根据西藏扎布耶湖区SZK02孔所揭露的近84m剖面的沉积物特征与其产的介形类6属20种,轮藻类2属3种,结合14C、ESR、U-series地层测年等,初步认为该区128～1.4ka至少存在5个较明显的气候变化时期。①在128～76.7ka(83.63～57.0m)处于我国末次间冰期时段,气候凉湿,湖盆扩展,在90～81ka期间湖面最高,水质最淡。②76.7～58.6ka(57.0～38.13m)为我国末次冰期早冰阶时期,湖盆收缩,水温低,早期76.7～69.7ka(57.0～47.5m)偏冷湿,中期69.7～65.0ka(47.52～42.64m)气候温干,正逢早冰阶时期;晚期65.0～58.6ka(42.64～38.13m)气候干燥度下降。③58.6～29.1ka(38.13～13.75m)处于我国末次冰期间冰阶时段,早期58.6～51.6ka(38.13～33.07m)偏温湿,为3c暖期;中期51.6～42.5ka(33.07～26.13m)气候干冷,为3b冷期,正临末次冰期中冰阶时;晚期42.5～36.0ka(26.13～20.16m)偏凉湿,湿度更大,再次出现高湖面,为3a暖期;末期36.0～29.1ka(20.16～13.75m),趋向温干。④29.1～11.8Cal.ka(13.75～4.83m),气候趋向干冷,处于末次盛冰期(LGM)、末次晚冰阶时期,湖盆萎缩,水温低。早期29.1～16.6Cal.ka(13.75～6.98m)偏温湿;晚期16.6～13.1Cal.ka(6.98～5.76m)寒冷干燥;至末期13.1～11.7Cal.ka(5.76～4.83m),进一步干燥寒冷,全球新仙女木事件在本区发生。⑤11.7～1.4Cal.ka(4.83～0.65m),大致进入全新世气候期,气候波动大,凉湿与干冷交替频繁发生。在11.7～10.7Cal.ka(4.83～4.42m)时较温湿;10.7～9.5Cal.ka(4.42～4.07m)转向干冷;9.5～9.1Cal.ka(4.07～3.7m)更干冷,湖盆进一步萎缩;9.1～6.3Cal.ka(3.7～2.86m)向温干过渡;6.3～3.6Cal.ka(2.86～1.77m)干冷,湖泊已成盐湖;3.6～1.4Cal.ka(1.77～0.65m),气候趋向冷湿。

Microfossils and Climatic and Environmental Changes in the Zabuye Lake Area,Tibet,from 128 to 1.4 ka BP

This paper introduces the characteristics of sediments and their contained 6 genera and 20 species of ostracods and 2 genera and 3 species of charophytes revealed by nearly 84 m deep well SZK02 drilled in the Zabuye Lake area,Tibet.Based on these,combined with 14C,ESR and U-series dating,the authors preliminarily think that more than five stages with the distinctive characteristics of climatic change occurred in the area at 128~1.4 ka BP.Stage 1(ca.128~76.7 ka BP;83.63~57 m):The first stage occurred in the last interglacial period of China,when the climate was cool and wet and the lake basin expanded.At 92~81 ka BP,the lake had the highest level with the freshest water.Stage 2(ca.76.7~58.6 ka BP;57~38.13 m):It occurred in the early glacial stadial of the last glacial period,when the lake basin shrank and the water temperatures were low.In the early interval 76.7~69.7 ka BP(57.0~47.6 m),the climate was slightly cold-wet;the middle interval 69.7~65.0 ka BP(47.6~42.6 m)fell on the early glacial stadial with a warm-dry climate;and in the late interval 65.0~58.6 ka BP(42.6~38.13 m),the climatic aridity decreased.Stage 3(ca.58.6~29.1 ka BP;38.13~13.75 m):This stage occurred in the interglacial stadial of the last glacial period of China.The early interval 58.6~51.6 ka BP(38.13~33.07 m)was equivalent to mild phase 3c of the interglacial stadial of China,when the climate was slightly warm-wet;the middle interval 51.6~42.5 Ka(33.07~26.13 m)was cold phase 3b,just falling on the middle glacial stadial of the last glacial period,when the climate was dry-cold;and the late interval 42.5~36.0 ka BP(26.13~20.16 m)witnessed a slightly cool-wet climate with a much higher humidity and a higher lake level,which was equivalent to mild phase 3a.In the last interval 36.0~29.1 ka BP(20.16~13.75 m),the climate tended to be warm-dry.Stage 4(ca.29.1~11.8 Cal.ka BP;13.75~4.84 m):The stage occurred in the Last Glacial Maximum(LGM)and late glacial stadial of the last glacial period,when the climate tended to be dry-cold and the lake basin shrank with low water temperatures.In the early interval 29.1~16.6 Cal.ka BP(13.75~6.98 m),the climate was slightly mild-wet;in the late interval 16.6~13.1 Cal.ka BP(6.98~5.76 m),the climate was cold-dry;and in the last interval 13.1~11.8 Cal.ka BP(5.76~4.84 m),the climate became further dry-cold.The global Younger Dryas event took place in the area.Stage 5(ca.11.8~1.4 Cal.ka BP;4.84~0.65 m):In this stage the area entered the Holocene climate period,when the climate fluctuated greatly and the cool-wet climate and cold-dry climate alternated repeatedly.At 11.8~10.7 Cal.ka BP(4.84~4.42 m),the climate was relatively mild-wet;at 10.7~9.5 Cal.ka BP(4.42~4.07 m),the climate turned dry-cold;at 8.4~7.8 Cal.ka BP(9.5~9.1 m),the climate became much drier-colder and the late basin further shrank;at 9.1~6.3 Cal.ka BP(3.7~2.86 m),the dry-cold climate passed into the warm-dry one;and at 6.3~3.6 Cal.ka BP(2.86~1.77 m),the climate turned dry-cold again and the lake became a saline one;at 3.6~1.4 Cal.ka BP(1.77~0.65 m),the climate tended to be cold-wet.