镜泊湖全新世火山空降碎屑剖面和喷发历史

THE SECTION OF AIRFALL CLASTIC ROCK OF HOLOCENE VOLCANO IN JINGPOHU REGION AND ITS ERUPTIVE HISTORY

镜泊湖全新世火山群 10余座火山分成 5个小的喷发中心位居西南和东北两区 ,每个喷发中心由 2～ 4个火山组成。西南区包括“火山口森林”、“大干泡”、“五道沟”和“迷魂阵”等 4个喷发中心 ,东北区仅“蛤蟆塘”1个喷发中心。火山喷发的产物主要包括熔岩流、溅落堆积和空降堆积 ,火口的锥体主要由溅落堆积的火山渣、火山弹、熔岩饼和薄层熔岩流组成。在“大干泡”和“蛤蟆塘”两处的空降碎屑堆积可达数米厚。镜泊湖全新世火山岩分布面积近 5 0 0km2 ,岩浆主要源自“火山口森林”的1号和 4号火口。文中通过“火山口森林”4号火口空降碎屑实测剖面及其碳化木14 C定年 ,纠正了以往的14 C定年资料 ,认为镜泊湖全新世火山的喷发活动主要在距今 5 2 0 0～ 5 5 0 0a,相继由多次喷发形成 10余座火山。研究认为 ,镜泊湖地区全新世期间不存在以千年计的

More than ten volcanoes of Jingpohu Holocene Volcanic Group consist of five small eruption centers situated at southwest area and northeast area separately. Southwest area includes four eruption centers, namely “Crater Forest”, “Daganpao”, “Wudaogou” and “Mihunzhen”, respectively. Northeast area has only one eruption center called “Hamatang”. Eruptive materials include mainly lava flow, splash deposit and airfall deposit. Volcanic cone consists of cinder, bomb, driblet and thin lava flow. The thickness of airfall clastic deposit exceeds several meters in “Daganpao” and “Hamatang”. The distribution area of Jingpohu Holocene volcanic rocks is about 500km 2. The magma source originated mainly from No.1 crater and No.4 crater in “Crater Forest”. According to measured section of airfall clastic rock and 14C dating of carbonized wood at No.4 crater of “Crater Forest”, and correcting a mistake of former 14C dating data, it is inferred that the volcanic eruption of Jingpohu Holocene Volcano had been lasted 300 years from 5500a BP to 5200a BP. Continuous eruption in this period resulted in more than ten volcanoes in Jingpohu region.