【摘要】 近年来,在岷江上游及其支流杂谷脑河中发现了多处滑坡古堰塞湖沉积物,并受到广泛关注,但也有不少学者质疑是否是堰塞湖相沉积物。2008年5月12日四川汶川地震引发了几十个规模较大的滑坡堰塞湖,叠溪古堰塞湖展示的重大地质历史事件再次引起学术界广泛的关注。本文根据最新调查、勘查和测试资料对古堰塞湖的形成与消亡过程做了进一步查证;对获得的全断面岩芯样品开展了AMS¹⁴C测年、孢粉分析、稳定碳氧同位素、有机质含量及粒度分析等一系列的环境代用指标分析。研究表明,叠溪古堰塞湖形成于30000万年前,经历了约15000年,沉积了200余米的湖相沉积物,大约在15000年前开始溃决消亡。从钻孔岩芯中获取了古地震和古气候的重要信息,揭示古堰塞湖沉积期间曾经历过至少10次强烈地震,并且与气候的变化有一定的相关性,这些资料信息为讨论岷江上游地区地貌和古气候演化规律提供了重要依据,提出了一套通过对古堰塞湖沉积物的分析研究,探讨地质环境和古气候演化的系统方法。更多还原

【Abstract】 A huge ancient landslide-dammed lake at the upstream of Minjiang River has been discovered,which came into being 30000 years ago.It existed for ten thousand years with 200-meter-thick lacustrine sediments formed,and disappeared with its outburst in 15000 years ago.After that several other such lakes and their sediments had been founded in the same area.These discoveries attracted widespread attention when published,but some scholars are skeptical of their facies of landslide-dammed lake.When dozens of large-scale landslide-dammed lakes resulted from the Wenchuan Earthquake on May 12th,2008,Diexi Lake began to arouse widespread concern again in that it indicates major events in the geological history.Based on the latest surveys,explorations and tests,a further demonstration was done on its formation and disappearance.An AMS experiment was done on whole cross-section cores to carry out C dating and pollen analysis,and to test stable carbon-oxygen isotopes,organic matter content and particle size.Paleo-seismic and paleo-climate information were obtained from drill cores,reveal that during deposition of the ancient dammed lake had experienced at least 10 times strong earthquake from 30830aB.P.to 14854aB.P.These change is a certain correlation with climate change.The obtained data provide an important basis for the discussion of the ancient topography and paleoclimate evolution in the upper reaches of Minjiang River.This study also indicates a new approach to study ancient geological and climatic evolution with samples from the sediments of ancient landslide-dammed lake.更多还原