Chemotaxonomical identification of Holocenic bogwood recovered after 2007 Niigataken Chuestsu-oki Earthquake

Abstract

A Holocenic coniferous bogwood salvaged from the 70 to 100 m-deep seabed after the 2007 Niigataken Chuetsu-oki Earthquake was analyzed anatomically and chemically. The main anatomical features of the wood were the presence of (i) large window-like pits in cross fi eld and (ii) smoothwalled cells of ray tracheid. Feature (i) allowed identifi cation of the wood as genus Pinus . Feature (ii) is characteristic of section Quinquefoliae , but possible decay by the long burial (3400 -3210 cal BP) left the identifi cation inconclusive. Chemical analysis showed that the major volatile components of the bogwood were cadinane-type sesquiterpenes. In contrast, those of modern pine samples were longifolene and monoterpenes from Pinus densifl ora and Pinus thunbergii , nerolidol from Pinus parvifl ora and P . parvifl ora var. pentaphylla , and monoterpenes from Pinus koraiensis . Thus, none of the modern pines contained cadinane-type sesquiterpenes as major components. As organic components of wood are known to undergo diagenetic transformation under geological conditions, recent samples were subjected to heat treatment at 180 ° C for 24 h to simulate the long burial time. As a result, nerolidol, the main component of P . parvifl ora and P . parvifl ora var. pentaphylla was converted to cadinane-type sesquiterpenes. Therefore, it is highly likely that the bogwood sample was P . parvifl ora or P . parvifl ora var. pentaphylla , section Quinquefoliae subsection Strobus , agreeing with the anatomical feature of section Quinquefoliae .