Carbon isotopic composition of sterols in geochemical samples

Carbon isotopic composition of sterols in marine Holocene sediments, marine sinking particles, tree leaves, and soils were determined. delta C-13 valu es bf algae-derived sterols such as 24-methylcholesta-5,22- dien-3 beta -ol and dinosterol in the marine sediments range from -22.1 to -25.2 parts per thousand, while those of 24-ethylcholest-5-en-3 beta -ol (24-ethylcholeste rol) range from -22.6 to -24.3 parts per thousand. We conclude that 24-ethy lcholesterol in the marine sediments derives from marine algae, because the ir delta C-13 values are markedly different from those of the leaves of C-3 (similar to -29 parts per thousand) and C-4 (-14 parts per thousand) plant s and similar to those of the algal sterols.