The lipid distribution in sediments from the surface and base of Hole 1084A (late Pleistocene and mid-Pliocene, respectively) are dominated by marine microalgal biomarkers comprised primarily of long-chain alkenones originating from haptophyte algae. Terrigenous inputs of n-alkanes and n-alkanols are minor components of the GC-amenable lipids, but their presence suggests a terrigenous input most likely via eolian transport in trade winds running off and along the coast of continental southern Africa.
Direct interpretation of lipid abundances in relation to changes in paleoproductivity between the mid-Pliocene and late Pleistocene is complicated by evidence of increased diagenetic transformations in the deep sample. These changes may have caused an apparent enrichment of refractory lipids relative to Corg (e.g., n-alkanes and long-chain alkenones) compared to the more labile lipids (e.g., sterols). This observation would suggest that the labile functionalized compounds present in the surface sediment have become diagenetically depleted in the deeper sediment. Their diagenetic byproducts are evident in the deep sample as increased relative abundances of steroidal/hopanoidal hydrocarbons. The distribution of compounds that might indicate the extent of early diagenesis (unsaturated hydrocarbons and thiophenes) appear contradictory. This observation may be explained by the incorporation of functionalized lipids into the geomacromolecular-bound fraction throughout the diagenetic process and illustrates a potential limitation in studying only the free solvent extractable lipids.