川西阿坝盆地南缘阿柯河Ⅲ级阶地晚更新世中期的孢粉记录

Middle Late-Pleistocene Sporopollen Records of Ake River III Terrace in Southern Margin of Aba Basin,Western Sichuan

植被的生长变化指示气候的演化,本文利用孢粉记录反演古植被,重建古气候。选取青藏高原东部的川西阿坝盆地南缘阿柯河Ⅲ级阶地PM01剖面为研究对象,进行样品的孢粉分析和光释光(OSL)测年,以分析阿坝盆地的气候演化。测年结果显示剖面PM01的年龄为晚更新世中期(78.4±7.1)~(71.6±6.2)ka B.P.。根据孢粉组合特征和数学分析方法,将剖面PM01划分为3个孢粉组合带,结果表明阿坝盆地在晚更新世中期(78.4±7.1)~(71.6±6.2)ka B.P.的植被为疏林草原。古气候演化过程可分为三个阶段,第一阶段的气候表现为寒冷干旱;第二阶段较第一阶段温暖,但依然表现为寒冷偏干;第三阶段趋向更温暖,表现为温凉偏干。该结果与末次冰期的气候变化趋势一致。本研究为川西地区第四纪植被与气候演化研究提供了新资料,对青藏高原东部第四纪古气候的研究具有参考意义。

Vegetation growth and change have important implications for climatic evolution.In this study,we used sporopollen record to reconstruct paleovegetation and paleoclimate.Based on the sporopollen study of the Ake River III-level terrace in the southern margin of Aba basin in western Sichuan(eastern Qinghai-Tibet Plateau)and OSL dating,the results show that PM01 is(78.4±7.1)to(71.6±6.2)ka B.P.(middle Late Pleistocene).According to the palynological assemblage and mathematical analysis,the PM01 profile was divided into three palynological zones.The results show that vegetation in the Aba Basin was sparse forest and grassland from(78.4±7.1)to(71.6±6.2)ka B.P.in the middle Late Pleistocene.The paleoclimate evolution can be divided into three stages:(1)cold and arid;(2)warmer than the first stage,but still cold and dry;(3)warmer and then cooler and drier.The results are consistent with the climate evolution trend of the last ice age,and provide new data for the study of the Quaternary regional vegetation and climate evolution,which is of great significance for studying Quaternary paleoclimate in the eastern Qinghai-Tibetan Plateau.