| Autor: |
M. S. Singletary, B.J. Huizinga, Albert G. Holba, Leon Dzou, J. M. Moldowan, Erik W. Tegelaar, W.D. Masterson, William B. Hughes, Marcio Rocha Mello |
| Rok vydání: |
1998 |
| Předmět: |
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| Zdroj: |
Organic Geochemistry. 29:1269-1283 |
| ISSN: |
0146-6380 |
| Popis: |
Two C26 sterane ratios, the 24-nordiacholestane ratio (NDR) and the 24-norcholestane ratio (NCR), are useful for assessing petroleum source age. Values for these parameters generally increase in the Cretaceous when diatoms were rapidly radiating and further in the Oligo-Miocene due to widespread high-latitude deposition of diatomaceous sediments. Sources with shale lithologies tend to exhibit the highest ratios; while carbonate and terrigenous-rich lithologies generally show lower ratios. On the North Slope of Alaska, elevated ratios are observed for Cretaceous HRZ oils and mixed oils containing Cretaceous input compared to older Triassic and Jurassic derived oils. Tertiary-sourced oils from Romania and Bulgaria have much higher ratios relative to Jurassic-sourced oils in the Black Sea region. Oleanane was observed in comparable levels in some Black Sea Tertiary and Jurassic oils and source rocks. NDR and NCR coupled with other age-diagnostic indicators (such as oleanane and dinosterane) provide powerful tools for differentiating age of source and organic facies for oils from the Black Sea and Sub-Andean Basins of Peru and Ecuador, respectively. Oils derived from sources deposited in low tropical latitudes tend to have little diatom input and as a consequence, do not display high values regardless of age. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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Full Text from ScienceDirect