Latitudinal distributions of terrestrial biomarkers in the sediments from the Central Pacific

Twenty-three deep-sea surface sediments collected from the Central Pacific across a latitudinal transect at 175 degrees E from 48 degrees N to 15 degrees S were studied for lipid class compounds including C-25-C-36 n-alkanes, C-24-C-28 fatty alcohols, and C-23-C-34 fatty acids, which are derived from terrestrial higher plants. Although all of these terrestrial biomarkers were most likely transported long distances in the atmosphere over the Central Pacific, their latitudinal distribution patterns are specific to each compound group. n-Alkanes (C-25-C-36) are most abundant in the highest latitude (48 degrees N) and gradually decrease toward the lower latitude (13 degrees N). Fatty alcohols (C-24-C-28) rapidly decrease from 48 degrees N to 30 degrees N and stay relatively low in the lower latitudes. By contrast, abundances of fatty acids (C-23-C-34) are relatively high in the lower latitudes, although they increase from mid to high latitudes of the Northern Hemisphere. In addition, distributions of n-alkanes (C-25-C-36) in 48 degrees N-19 degrees N are characterized by CPI (carbon preference index) of 4.9-8.2 (av. 6.6), which are significantly higher than those (1.9-4.9; av. 2.8) in the low latitudes (15 degrees N-15 degrees S). These latitudinal patterns of terrestrial biomarkers in the Central Pacific sediments are generally interpreted in terms of the different wind regimes between high and low latitudes; that is, distributions of organic molecules transported from Asia to the North Pacific by westeries are different from those by trade winds which transport aerosols from Central and South Americas to the tropical Pacific. Copyright (C) 1997 Elsevier Science Ltd.