Abstract
24-norcholestanes have been shown to be useful biomarkers to assess the age of sediments and petroleum, but until now, the biological sources of their precursors, i.e., 24-norsterols, were unclear. We have unambiguously identified relatively high concentrations of 24-norcholesta5,22-dies-3 beta-ol in the diatom Thalassiosira aff. antarctica (6%-10% of total sterols) and, in much lower concentrations, in the dinoflagellate Gymnodinium simplex (0.2% of total sterols). These identifications and other reports of 24-norsterols in dinoflagellates suggest that both diatom and dinoflagellate species are major sources for 24-norcholestanes in sediments and petroleum. The evolutionary history of these organisms suggests that observed increases of 24-norcholestane concentration in the Jurassic and the Cretaceous are related to dinoflagellate expansion, whereas an increase in the Oligocene-Miocene is likely caused by diatom expansion. Our results also explain the biogeographical distribution of 24-norcholestanes, i.e., high concentrations at high (paleo)latitudes are likely caused by diatoms, while low concentrations at lower (paleo)latitudes are likely caused by dinoflagellates.
Original language | English |
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Pages (from-to) | 419-422 |
Number of pages | 4 |
Journal | Geology |
Issue number | 5 |
DOIs | |
Publication status | Published - 2007 |
Keywords
- DIATOMS
- SEA
- STEROLS
- IDENTIFICATION
- Geology
- SEDIMENTS
- FOSSIL RECORD
- DINOFLAGELLATE POLARELLA-GLACIALIS
- OCEAN
- TEMPERATURES
- PHYTOPLANKTON