Marine tephra in the Japan Sea sediments as a tool for paleoceanography and paleoclimatology

Ken Ikehara

doi:10.1186/s40645-015-0068-z

Abstract

Tephra is a product of large and explosive volcanic events and can travel thousands of kilometers before deposition. Consequently, tephra deposits are common in terrestrial, lacustrine, marine, and glacial environments. Because tephra deposition is a geologically synchronous event, tephras constitute important isochrones in the Quaternary sequence, not only in Japan but also throughout the northwest Pacific and its marginal seas. As a result, establishing the chronostratigraphic order of tephra deposits is an effective tool for assessing local and regional stratigraphies and for correlating events among sites. For example, tephrostratigraphy can provide precise chronological constraints for other stratigraphic data, such as magneto- and biostratigraphic data. Spatiotemporal variability in the occurrence and geochemistry of tephras can also be used to trace the magmatic evolution of island arcs and their relationships to regional tectonics. In a paleoclimatic context, tephra deposits allow the correlation of past climate events among terrestrial, lacustrine, and marine environments. Tephrochronology is also a fundamental element used in reconstructing the marine reservoir effect, where the ages of tephra in marine and terrestrial settings are compared. Therefore, tephra is a valuable tool not only in stratigraphy, chronology, and volcanology but also in paleoceanography and paleoclimatology.

Highlights

Tephra is a product of large, explosive volcanic eruptions, and distal tephra can travel thousands of kilometers before it is deposited (e.g., Alloway et al 2007; Lowe 2011; Costa et al 2012)
Tephra beds occur in marine sediment sequences adjacent to volcanic islands and volcanic arcs associated with subduction zones, such as the Japanese archipelago
The eruption ages of the Late Pleistocene to the Holocene terrestrial tephras are generally determined with radiocarbon dating of (a) tree trunks buried in pyroclastic and ashfall deposits or (b) peat beds located above and below the tephra bed

Summary

Introduction

Tephra is a product of large, explosive volcanic eruptions, and distal tephra (volcanic ash) can travel thousands of kilometers before it is deposited (e.g., Alloway et al 2007; Lowe 2011; Costa et al 2012). Both the Ulleung and Baegdusan volcanoes display explosive alkaline to trachytic volcanism, which has resulted in the deposition of numerous distal tephra beds on the floor of the Japan Sea and on the Japanese islands.

Results

Conclusion