Differences between Whole Rock and Insitu Analysis on Tephra:Evidence from the 1 600 a cal.BP Eruption of Jinlongdingzi Volcano
Sun Chunqing
You Haitao
Liu Jiaqi
Chu Guoqiang
Liu Qiang
Abstract：Tephra layers with unknown ages are usually identified and fingerprinted by their glass compositions.But,such cor-relations may be problematic when they own heterogeneous glass compositions.Lake Sihailongwan locates in the Longgang vol-canic field and its varved lacustrine sediments can preserve the volcanic products from surrounding areas.Additionally,its varve-chronology can provide an advantage chronological framework for recent geological events which are difficult to date by other dating methods.A core drilled from Lake Sihailongwan (core 2008)shows that there is a tephra layer at 78-79 cm and an age of AD 308 was assigned to it by varve-chronology.The volcanic glass exhibits a heterogeneous composition,ranging from basaltic trachyandesite to tephriphonolite.Such a heterogeneous characteristic of glass shards from this tephra layer can be clearly revealed by the biplots of FeO,TiO 2 and Al2 O 3 vs.MgO.For the applications to the tephrostratigraphy,whole rock analysis of tephra may be wrong and could not reflect the heterougeneous of primary magma while composition of glass is a bet-ter choice.
Keywords：lake Sihailongwantephravolcanic glasstephrochronologyJinlongdingzipetrology
Publication Date：2016-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：8( 97-104 )