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A transect of marine surface sediment samples from 1 degrees N to 28 degrees S off southwest Africa was analysed to verify the application of hydrogen isotope compositions of terrestrial plant-wax n-alkanes preserved in ocean sediments as a proxy for continental hydrological conditions. Conditions on the adjacent continent range from humid evergreen forests to deciduous forests, wood-and shrub land and further to arid grass-lands and deserts. The hydrogen isotope values for the dominant n-alkane homologues (C-29, C-31 and C-33) vary from -123% to -141% VSMOW and correlate with the modelled hydrogen isotope composition of mean annual and growing season precipitation of postulated continental source areas (r up to 0.8, p < 0.01). The apparent hydrogen isotope fractionation between alkanes and mean annual precipitation is remarkably uniform (-109% on average, sigma <= 5%, n = 27). Potentially, effects of aridity on the apparent hydrogen isotope fractionation are concealed by the contribution of different plants (C-3 dicotyledons vs C-4 grasses). Thus, isotope ratios of leaf wax n-alkanes preserved in ocean margin sediments in these and similar tropical regions may be directly converted to delta D ratios of ancient precipitation by employing a constant hydrogen isotope fractionation. (C) 2016 Elsevier Ltd. All rights reserved.