Tephra Discovered in High Resolution Peat Sediment and Its Indication to Climatic Event

Abstract

Floating tephra was deposited together with ice core, snow layer, abyssal sediment, lake sediments, and other geological records. It is of great significance to interpret the impact on the climate change of volcanic eruptions from these geological records. It is the first time that volcanic glass was discovered from the peat of Jinchuan Maar, Jilin Province, China. And it is in situ sediments from a near-source explosive eruption according to particle size analysis and identification results. The tephra were neither from Tianchi volcano eruptions, Changbai Mountain, nor from Jinlongdingzi volcano about 1 600 aBP eruption, but maybe from an unknown eruption of Longgang volcano group according to their geochemistry and distribution. Geochemical characters of the tephra are similar to those of Jinglongdingzi, which are poor in silica, deficient in alkali, Na₂O content is more than K₂O content, and are similar to distribution patterns of REE and incompatible elements, which helps to speculate that they originated from the same mantle magma with rare condemnation, and from basaltic explosive eruption of Longgang volcano group. The tephra, from peat with age proved that the eruption possibly happened in 15 BC–26 AD, is one of Longgang volcano group eruption that was not recorded and is earlier than that of Jinglongdingzi about 1 600 aBP eruption. And the sedimentary time of tephra is during the period of low temperature alteration, which may be the influence of eruption toward the local climate according to the correlativity of eruption to local temperature curve of peat cellulose oxygen isotope.