Correspondence between glass-FT and 14C ages of silicic pyroclastic flow deposits sourced from Maninjau caldera, west-central Sumatra

Abstract

Paroxysmal pyroclastic flow deposits sourced from Maninjau caldera in west-central Sumatra are dated at 50±3 ka ( n=3) using the isothermal plateau and diameter corrected fission-track (ITPFT and DCFT, respectively) techniques on glass shard constituents. In addition, charcoal obtained from tall trees in position of growth within the paroxysmal flow deposit on the upper flanks for the caldera are also dated at 52.3±2 14C ka ( n=2) and 51.1±3.2 14C ka ( n=1) using an acid–base, wet oxidation, stepped combustion (ABOX-SC) and standard acid–base–acid (ABA) 14C techniques, respectively. The close correspondence in 14C ages of charcoal sample splits analysed at two laboratories (Australian National University, Australia and Waikato University, New Zealand) verifies the reliability of these 14C techniques up to at least 50 ka. Based on concordant ages derived from glass-FT and 14C techniques, an age of 52±3 ka is assigned to the latest silicic eruptive activity at Maninjau caldera. This chronology is further confirmed by the occurrence of a silicic tephra bed that closely underlies paroxysmal Maninjau deposits at two sections and is correlated with Youngest (75 ka) Toba Tephra (YTT) erupted from Toba caldera in north-central Sumatra. This study not only provides a much needed regional chronological reference point for Quaternary deposits in west-central Sumatra but also extends the minimum age range of the glass-FT technique from 75 ka down to c. 50 ka that is now for the first time within the extended maximum age range of the 14C technique.