| What are the six types of diagenetic reactions? | 1. Oxidation/mineralisation
2. Sulphurisation
3. Aromatisation
4. Defunctionalisation
5. Isomerisation
6. Catagenesis (e.g. C-C bond cleavage) |
| Diagenesis can alter ... and ... of biomarker lipids in different ways depending on the structure of the original biomarker lipids | abundances & structure |
| The concentrations of “marine” biomarkers in the oxidized S1sapropel are significantly .... | decreased |
| The concentrations of “terrestrial” n-alkanes in the oxidized S1sapropel are .... compared to marine bimarkers | decreased much less than |
| Post depositional oxidation = | as oxygen came back the upper part of the sapropel + biomarkers was burned away (this is why the decrease is super sharp) |
| Post depositional oxidation may be recognized when comparing Corg to ... | Ba/Al -> shows old (not burned away) sapropel |
| Terrestrial biomarkers can at times survive in the reoxygenated layer due to .... Uncertain if this is due to structure, matrix protection or prepositional oxidation | slow degradation |
| what happened to this biomarker and what can the ratio between the two signify? What is it and who makes these? | poster-depositional oxidation & shows a spike at the oxidation front. they are longchail diols made by algae. |
| Sulphurisation of biolipids occurs through reaction of ......... species (sulphide, polysulphides) with functional groups (e.g., keto group, double bonds) of biolipids. | inorganic sulphur |
| The position of the sulphur indicated? | position of past functional groups |
| Sulphurisation takes mainly place ... | in the sediments (not watercolumn) as it is a relatively slow process (100-1000 years) -> dependent on structure of organic component however |
| intramolecular S incorporation can result in the formation of... | Low molecular weight molecules |
| intermolecular s incorporation can result in the formation of ... | high molecular weight molecules (polymerisation) |
| labrotary desulphurisation is needed because ... | sulphurisation lead to the lss of many biomarkers from our common analytical window |
| Sulfurisation leads to ..... of many biomarkers. It requires often non-conventional techniques (e.g. desulfurisation) to access thislocked information. | sequestration |
| Sulphurisation results in archiving “labile” functional group information by the ... | position of sulphur incorporation. |
| During late diagenesis/early catagenesis labile S-C bonds are preferentially broken resulting in release of biomarkers from HMW substances... | This process results in loss of information since functional group information is lost. |
| Aromatization is the process of converting a chains & nonaromatic rings into .... and is catalysed by aromatase, a P450 enzyme. | an aromatic rings |
| Aromatization happens relatively fast, especially if .... are already present. Aromatization towards thermodynamically stable products. | rings and double bonds |
| Aromatization leads to the..... However, basic features of carbon skeletons can still be recognized and related to original biomarker lipids | loss of functional groups, addition of rings and ring cleavage |
| Stable isotopes can be used to relate aromatic products with .... | precursors |
| Wha tis a PAH and what diagentic reaction can make them | polycyclic aromatic hydrocarbons - aromatisationS |
| Anthropogenic sources of PAH? | mainly produced by combustion processes, dominated by parent (non-substituted) PAHs |
| Natura sources of PAHs? | forest and prairie fires, natural seepage of petroleum & diagenesis of natural products |
| what is this molecule called and what is its precursor? | perylene -> quinone pigments in fungi and insects |
| What happened to these molecules and what might be their origin? | aromatisation - abietc acid (gymnosperms) -> diterpenoid precursor |
| What happened to these molecules and what might be their origin? | aromatisation- b-amyrin (angiosperms) ((pentacyclic) triterpenoid) |
| What does this figure show? | cyclisation and aromatisation of isorenieratene |
| This was likely a? | bacteriohopanetetrol |
| Defunctionalisation is the .... | loss of functional groups |
| What are the four typical defunctionalisation reactions? | 1. Dehydration (removal of hydroxy groups -OH)
2. Reduction of double bonds (removal of double bonds) – form saturated equivalent, could also aromatize instead though – both take place!
3. Decarboxylation (removal of acid groups -COOH)
4. Reduction of keto groups R-C(=O)-R |
| Isomerisation = | Change of original stereochemistry into its isomer -> can be used to determine maturity of sample/oil as heat and pressure will result in more of the diagenetic isomer (vs natural isomer) |
| Catagenesis = | breaking of bonds |
| catagenesis of c-C bonds | may result in product(s) that can still be used as biomarkers |
| catagenesis often results in | substatial loss of information |
| what happned to this molecule and what is its precursor | catagenesis & isorenieratene |
