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

Abstract

Abundance and carbon isotopic composition (δ¹³C) 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 δ¹³C 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 δ¹³C 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) C₄ plant evolution at ca. 10 ka estimated from their temperatures, which is consistent with historical and archeological studies.