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A Puzzling 14C Result Obtained for a Carbonized Wood Sample Embedded in Volcanic Lava

Published online by Cambridge University Press:  09 February 2016

J H Lee*
Affiliation:
NCIRF, Seoul National University, Seoul 151-742 Korea
K Choe
Affiliation:
NCIRF, Seoul National University, Seoul 151-742 Korea
J Kang
Affiliation:
NCIRF, Seoul National University, Seoul 151-742 Korea
S Song
Affiliation:
NCIRF, Seoul National University, Seoul 151-742 Korea
Y M Song
Affiliation:
NCIRF, Seoul National University, Seoul 151-742 Korea
M H Yun
Affiliation:
NCIRF, Seoul National University, Seoul 151-742 Korea
J C Kim
Affiliation:
Department of Physics and Astronomy, Seoul National University, Seoul 151-747 Korea
*
2Corresponding author. Email: jefflee@snu.ac.kr.

Abstract

It has been reported that the characteristics of a very old wood charcoal sample are different from those of modern wood charcoal according to its state of preservation (Cohen-Ofri et al. 2006; Rebollo et al. 2008). It can be assumed that these differences may lead to some difficulties when radiocarbon dating very old wood charcoal samples. To investigate this problem, we studied a carbonized trunk of Prunus pendula for. acendens tree buried in lava and found at the Hantan River lava plateau on the Korean Peninsula. The 14C date of this sample was previously measured as >30,000 BP. However, separate 14C results of its outer crust and inner wood showed a considerable difference, exceeding the estimated age differences by tree-ring counting. To study the reason for this discrepancy, optical microscopy and FTIR (Fourier transform infrared spectroscopy) were performed to examine the differences in the structural and chemical states of the samples. For reference data and to expand our understanding of very old wood charcoal, we applied the same analysis tools (AMS, FTIR, FE-SEM, EDS, and optical microscopy) to a variety of wood charcoals and original wood. From these analyses, we noticed considerable chemical changes in the outer crust sample, and this might explain the age discrepancy. Although it seems that the age difference might be due to the digestion of 14C-free CO2 from a volcanic environment, this explanation would not account for such a large value in the age difference.

Type
Articles
Copyright
Copyright © 2013 by the Arizona Board of Regents on behalf of the University of Arizona 

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