The First Results of Tephrochronological Study of Late Pleistocene–Holocene Volcanic Eruptions in the Zhom–Bolok River Valley (Eastern Sayan)

Abstract

The first results of tephrochronological studies of Late Pleistocene–Holocene volcanic eruptions in the Zhom-Bolok River valley (Eastern Sayan) are reported. Based on the analysis of bottom sediments of the glacial lake Kaskadnoe-1, a detailed chronological scale of volcanic activity in this region has been worked out. It is established that the eruptions began at least 14 300 years ago and continued, gradually weakening, to 6280 years ago. In this period, ten groups of peaks of sediment enrichment in microtephra are registered for Kaskadnoe-1 Lake. The average interval between the stages of eruptions in this period was ~500–600 years. Between 14 300 and 13 400 years ago, the most large-scale volcanic events took place, eruptions were practically not interrupted, and the explosive activity was the most intense. The volcanic activity in the region in the period between 6280 and 2000 years ago is characterized by a relative rest. Later, eruptions resumed reaching peak values 1150 years ago and completing 800 years ago.