Carbon isotopic compositions of fatty acids from the Japan Sea and their inferred terrestrial palaeoenvironment in Late Pleistocene

Abstract

Abundance and carbon isotopic composition (δ 13 C) of monocarboxylic fatty acids (n-FA) and n-alkanes in sediments spanning the last 24 kyrs from the southeastern Oki Trough, Japan Sea (core KT96-17, P-2) are presented. The δ 13 C values of n-alkanes, ranging from -36.9 to -25.6‰, are consistent with those (from -44.9 to -23.3‰) measured in sediments of C-3 and L-3 cores, located ca. 10 km southeast from KT96-17, P-2 core. We employed multiple regression analysis for n-C 16-30 FA as a function of latitude and distance from the adjacent landmasses, using the δ 13 C database obtained in sediments of the northeastern Asia. Calculated latitudes from even n-C 20-30 FA ranged from 54 to 37°N over the last 24 kyrs. Although the regression accounts for 59% of the total, the result is strongly supported by other evidences, i.e.: (i) a latitudinal migration from the last glacial period to the Present corresponding to the summer polar front migration observed from loess analysis; (ii) temperature estimated from the latitudes ranged from 2.5 to 15°C, corresponding to those estimated from pollen data; and (iii) C 4 plant evolution at ca. 10 ka estimated from their temperatures, which is consistent with historical and archeological studies.