腾格里沙漠东缘26ka来环境演化的植硅体记录
Environmental Change Documented by Pluvial Phytolith Records in the Past 26ka on East Edge of Tengger Desert

贺兰山中段西侧沙漠戈壁沉积发育,生态环境脆弱,对探讨末次冰期以来气候变化与沉积响应具有重要意义.选择了腾 格里沙漠东缘晚更新世晚期以来的洪积物剖面进行了初步古环境研究.在数字填图系统和野外路线调查基础上,对贺兰山中 段西侧、腾格里沙漠东缘地貌第四纪沉积物进行了较详细的调查研究.在 AMS14C测年基础上,从内蒙古阿拉善高原腰坝地区 Qp3- Qhpl洪积剖面沉积物中获得较丰富的植硅体化石,主要类型有方型、长方型、扇型、哑铃型、齿型、帽型、尖型、平滑棒型、刺 边棒型、突起棒型、三棱柱型等.此外,沉积物中赋存的大量炭屑和燃烧植硅体反映了古人类活动的历史.运用植硅体组合和温 暖指数分析重建了研究区2 6k a来的古植被、古气候演化,气候变化自早至晚经历了明显的干凉-暖干-暖湿- 冷湿-干 冷-暖干-暖湿7个阶段.洪积扇扇缘沉积环境变化反映了气候的干湿变化,且气候干湿变化与区域沙漠化和人类活动具有 相关性.
The desert and Gobi deposition are prevailing in the west edge of the middle Helan Mountain, which is subject to the frangibility of ecoenvironment. It is important to explore the relationship between the climate change and deposition response of Gobi desert since the Last Glacial, a pluvial profile of late Late Pleistocene on the east edge of Tengger desert is employed to rebuild the palaeoenvironmental change based on the phytolith analysis. On the basis of regional geological survey, geomorphology pattern and Quaternary sediment distribution in the west of middle Helan Mountain and east edge of Tengger desert were investigated in detail. Based on the AMS14C dating and phytolith records, paleovegetation and paleoclimate changes are reconstructed in detail. Relatively abundant phytolths are found in the pluvial sediments of Qp3- Qhplprofile at the Yaoba, including the following morphotypes: parallelepipedal bulliform cells (including square and rectangleshaped) and cuneiform bulliform cells (fanshaped), bilobate, rondel, trapeziform sinuate, elongate and unciform hair cell (pointshaped), elongate smooth, elongate echinate, elongate protuberant, and prism, etc. In addition, there are abundant charcoals and burnt phytoliths in the sediments, indicating the history of ancient human activities. Phytolith assemblages with the warmth index analysis have rebuilt the history of paleovegetation and paleocliamte changes in the past 26ka, showing 7 evident stages as follows: cooldry, warmdry, warmhumid, coldhumid, colddry, warmdry, and warmhumid. Our results demonstrate that the sedimentary environment of pluvial fan margin has a good response to the drought and wetness change of climate. The variation of the drought and wetness has a close relation with the regional desertification and ancient human activities