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干旱区晚第四纪已有较多高湖而与湖泊演化的报道和研究,对于认识区域环境变化有重要意义,但高湖面出现的时间尚存争议,高分辨率的气候环境记录仍相对缺乏。本文通过青海共和盆地达连海湖岸地貌考察和AMS ~(14)C年代学研究,讨论达连海古湖晚第四纪高湖面出现的可能时间;并通过达连海DLH99孔岩芯年代和高分辨率代用指标,讨沦高原东北缘末次冰消期以来的气候环境变化。达连海周围存在6级高湖面岸线或台地,~(14)C测年结果显示,最低的两级湖岸堤形成于全新世,其余湖岸台地年代均老于44cal.kaB.P.,当时在达连海地区形成一个较大的古湖泊。DLH99孔显示达连海近15cal.kaB.P.沉积了40.92m的湖相沉积物,平均沉积速率高达2.7mm/a。孢粉资料揭示出,现代干旱的共和盆地在末次冰消期以来存在两个山地针叶林发育阶段,分别位于末次冰消期和全新世早中期。全新世早中期是适合山地针叶林植被发育的气候最宜期,而晚全新世山地森林植被整体衰退。粒度分析结果显示,达连海全新世低水位时期对应于岩芯中部山地森林植被发育的晚期,出现较强烈干旱事件(岩芯深13～15m段),这种湖泊水位与植被所指示的气候变化不一致现象(即低水位时期盆地内耐旱植物和山地乔木花粉同时增加),可能揭示出干旱区山地与盆地环境对区域气候不同响应。达连海存在的系列高湖面和冰消期以来的完整气候记录,为理解晚第四纪季风边缘区气候变化过程及其机制提供了条件。
There are more high lakes in the arid area and the reports and studies on the evolution of lakes are of great significance for understanding the changes of the regional environment. However, there are still many controversies on the time of the high lakes and the relative lack of high-resolution climatic and environmental records . In this paper, we will discuss the possible occurrence time of the Late Quaternary High Lake in the Helianghai Lake in Qinghai by the geomorphological investigation of the Dalianhai Lake and the AMS ~ (14) C geochronology. Through the DLH99 core age and High-resolution alternative indicators, to discuss the northeastern edge of the plateau climate change since the last date. There are 6 shoreline or platform on the surface of the Dalianhai Sea. The ~ (14) C dating results show that the lowest two-stage bank dike forms in the Holocene, while the remaining lakeshore terraces are older than 44cal.kaB.P., In Dalianhai region to form a larger ancient lake. The DLH99 well shows that there is a lacustrine sediment of 40.92m in the Dalian Sea near 15cal.kaB.P. The average sedimentation rate is as high as 2.7mm / a. The pollen data reveal that there are two stages of coniferous forest development in the modern arid republic basin since the last ice-depletion period, which are located in the last ice-age and early-mid-Holocene, respectively. Mid-Holocene is suitable for the most suitable period for the development of mountain coniferous vegetation, while the late Holocene mountain forest vegetation as a whole declines. The results of grain size analysis show that during the Holocene low water level of the Danianhai Sea, corresponding to the late stage of the forest vegetation in the central core of the core, there was a more intense arid event (13 ~ 15m deep in the core). The lake water level and the climate indicated by the vegetation Inconsistent changes (ie simultaneous increase of drought tolerant plants and mountain arbor pollen in the basin during low water level) may reveal different responses of mountainous and basin environments to regional climate in arid regions. The complete set of climate records since the occurrence of the series of high lakes and dikes in the Dalian Sea provided the conditions for understanding the climate change process and mechanism of the monsoon marginal zone in the late Quaternary.