Lecture 8
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Lecture 8 - Leaderboard
Lecture 8 - Details
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| 🇬🇧 | 🇬🇧 |
| 1,13 and 1,15 diols are made by? | Eustigmatophytes, however marine Eustigmatophytes currently in culture are likely not the sources of C28 |
| 1,13 and 1,15 diols are made by? | Eustigmatophytes, however marine Eustigmatophytes currently in culture are likely not the sources of C28 |
| Long chain alkenones may be used as biomarkers for ... | Abundant haptophyte algae |
| Uk37 is based on? | C37 alkenone chains from haptophyte algae and the amount of double bonds. More double bonds relates to higher temperatures. Uk37 is higher for higher temperatures. |
| Wh are there offsets between uk37 and SST | The algae don't live at the same depth and environment throughout the whole year (annual mean vs seasonal) |
| Alkenones are easily influenced by lateral transport and sometimes degradation, this causes ... | Differential age and SST than other parts of sediment & core top vsersus surface water offset |
| Uk37 can be found... | Up until the mid eocene |
| TEX86 is based on? | The concept that the GDGT tetraetherlipids (86 carbons) of thaumarchaeta make more cyclopentane rings at higher temperatures as well as crenarchaeol' (GDGT4 + cyclohexane ring) |
| TEX86 gives ..... temperature and not sea surface temperature because the source organisms is not a .... | TEX gives upper water column temperature because thaumarchaeota are not phototrophs but rather ammonia oxidizing archaea (can live as long as there is ammonia) |
| TEX can however | Be calibrated to mean SST |
| 13C of GDGTs in surface sediments are similar to those in the surface and different to those in the deep water because of ... | Selective transport of surface archaeal lipids by packaging in active food webs & aggragates (mineral ballasting) |
| The mean annual T of Uk37 is ... than TEx | Better because it is more related to the photic zone |
| Uk37 algae and thaumarchaeota both compete for ammonia, but | Algae bloom in spring while thaumarchaeota bloom in summers |
| A large input of soil organic matter into a marine sediment will disturb the marine signal because | Soils also contain isoprenoid GDGTs, including crenarchaeol -> check for soil-derived biomarkers such as branched GDGTs |
| TEX can be used in lakes with | No large influence of surrounding soils |
| The long chainndiol index of 1,14 diols (proboscia diartoms) over 1,15-diols (other algae) is an indicator for | Upwelling and high productivity |
| If diagenesis acts the same on all biomarkers, we can use ratios however, | It can affect the relative abundances of biomarkers (why we want constant degradation conditions over time) |
| Dinosterol and other sterols = | Dinoflagellates and diatoms |
| Alkenones = | Haptophytes |
| Relative abundances of biomarkers | Indicate changes in (phytoplankton) compositoin |
| Phytoplankton composition proxy can be used in very ancient sediments yo | Constrain evolution of microbes |
| Two biomarkers for ocean anoxia/euxinia are ... | Isorenieratene (green sulphur bacteria) and okenane (purlpe sulphur bacteria) |
| What is the difference signified by finding okenane over isorenieratene? | Anoxia was high into surface waters |
| Anoxia might be present but not isorieneratene, why? | Anoxia was not into the photic zone |
| Lycopane indicates? (isoprenoid) | Anoxia (ratio of lycopene/n-C31 striahgt chain alkane) --> can be in upwelling |
| A lower amount of TOC also indicates less isorenieratene, why? | High TOC is indicative of anoxia for preservation and high primary productivity (sucking out the oxygen).Anoxia may kick in after the rise in TOC as it needs to grow into the photic zone still |
| Okenane signifies | Shallow surface ocean euxinia |
| Absence of indicators for anoxia may not be evidence of oxic conditions per se | Due to degradation or something |
| Two methods of terrestrial OM transport to oceans and their primary biomarkers they cary= | Wind (n-alkanes) & river (branched GDGTs) |
| Stable isotope analysis of plant wax lipid n-alkanes ... | Gives information on the C3/C4 vegetation |
| The BIT index relates... | Terrestrial derived branched GDGT abundance to marine crenarchaeol abundances, where a higher BIT indicate more soil organic matter input from rivers |
| How can brGDGTs say something about salinity? | Higher BIT index = more terrestrial input from rivers = more fresh water= lower slainity |
| Lignin phenols trace | Vegetation input and composition(BIT = soil input) |
| Branched GDGTs from soils may ... and ... under increasing (soil) temperature or decreasing pH | Form additional methylgroups or cyclopentane moieties |
| 5-methyl brached tetraethers index(MBT'5Me) corresponds to | Mean annual temperature - MAT |
| Cyclisation ratio of branched tetraethers (CBT) corresponds with | Soil pH (needed to derive temperature though!) |
| MBT and CBT can be used for lakes but | With different calibrations |
| DD of terrestrial n-alkanes related to dD of | Precipitation, in turn related to precipitation/evaporation balance |
| Always be aware of | Complicating factors: wind direction, degradation, lateral transport etc. |
| What proxy may be used for arctic sea ice cover (seasonal, not permanent part) | IP25 (HBI) highly branched isoprenoid alkene specific for arctic sea ice diatoms |
| What proxy may be used for anartctic sea ice melt | IPSO25, has 1 more double bond, southern ocean |
| HBI sea ice proxies are sensitive to degradation due to | Their double bonds that are thermodynamically more stable if saturateed - it is limited to the quarternary |
| During burning of biomass, ... and ... are formed. What does their abundance trace? | Anhydrosugars & polycyclic aromatic hydrocarbon (PAH) (aromatization). Their abundances trace fires |
| PAHs are not only formed by fires, this ... | Is a complicating factor as there are other pathways to form polycyclic aromatic hydrocarbons |
| What is this and what does it signify? | Anhydrosugars, biomass burning |
| What is happening here? | The abietic acids (gymnosperm biomarker) is being aromatized into a polycyclic aromatic hydrocarbon, perhaps due to a forrest fire. |
| The .... and .... of long chain 1,14-diols in surface sediments do not correlate well with (annual mean) SST. Diagenesis and variations in biological sources for 1,14 diols may mask the temperature signal. | Chain length and degree of saturation do not correlate with SST for 1,14-diols (proboscia diatoms) |
| The relative abundance of 1,14-diols versus 1,13-diols may be useful as a qualitative indicator for ... | Upwelling intensity -> better so than 14 over 15 at some locations! |
| The LDI (1,15 over 1,13) seems promising as an SST proxy | But not for lakes |
| 1,13 and 1,15 diols are made by? | Eustigmatophytes, however marine Eustigmatophytes currently in culture are likely not the sources of C28 |